Category: 7. Science

Now, a new study in mice led by researchers at Washington University School of Medicine in St. Louis and the Baylor College of Medicine reveals a previously unknown cellular purging process that may help injured cells revert to a stem cell-like state more rapidly. The investigators dubbed this newly discovered response cathartocytosis, taking from Greek root words that mean cellular cleansing.

Published online in the journal Cell Reports, the study used a mouse model of stomach injury to provide new insights into how cells heal, or fail to heal, in response to damage, such as from an infection or inflammatory disease.

“After an injury, the cell’s job is to repair that injury. But the cell’s mature cellular machinery for doing its normal job gets in the way,” said first author Jeffrey W. Brown, MD, PhD, an assistant professor of medicine in the Division of Gastroenterology at WashU Medicine. “So, this cellular cleanse is a quick way of getting rid of that machinery so it can rapidly become a small, primitive cell capable of proliferating and repairing the injury. We identified this process in the GI tract, but we suspect it is relevant in other tissues as well.”

Brown likened the process to a “vomiting” or jettisoning of waste that essentially adds a shortcut, helping the cell declutter and focus on regrowing healthy tissues faster than it would be able to if it could only perform a gradual, controlled degradation of waste.

As with many shortcuts, this one has potential downsides: According to the investigators, cathartocytosis is fast but messy, which may help shed light on how injury responses can go wrong, especially in the setting of chronic injury. For example, ongoing cathartocytosis in response to an infection is a sign of chronic inflammation and recurring cell damage that is a breeding ground for cancer. In fact, the festering mess of ejected cellular waste that results from all that cathartocytosis may also be a way to identify or track cancer, according to the researchers.

A novel cellular process

The researchers identified cathartocytosis within an important regenerative injury response called paligenosis, which was first described in 2018 by the current study’s senior author, Jason C. Mills, MD, PhD. Now at the Baylor College of Medicine, Mills began this work while he was a faculty member in the Division of Gastroenterology at WashU Medicine and Brown was a postdoctoral researcher in his lab.

In paligenosis, injured cells shift away from their normal roles and undergo a reprogramming process to an immature state, behaving like rapidly dividing stem cells, as happens during development. Originally, the researchers assumed the decluttering of cellular machinery in preparation for this reprogramming happens entirely inside cellular compartments called lysosomes, where waste is digested in a slow and contained process.

From the start, though, the researchers noticed debris outside the cells. They initially dismissed this as unimportant, but the more external waste they saw in their early studies, the more Brown began to suspect that something deliberate was going on. He utilized a model of mouse stomach injury that triggered the reprogramming of mature cells to a stem cell state all at once, making it obvious that the “vomiting” response — now happening in all the stomach cells simultaneously — was a feature of paligenosis, not a bug. In other words, the vomiting process was not just an accidental spill here and there but a newly identified, standard way cells behaved in response to injury.

Although they discovered cathartocytosis happening during paligenosis, the researchers said cells could potentially use cathartocytosis to jettison waste in other, more worrisome situations, like giving mature cells that ability to start to act like cancer cells.

The downside to downsizing

While the newly discovered cathartocytosis process may help injured cells proceed through paligenosis and regenerate healthy tissue more rapidly, the tradeoff comes in the form of additional waste products that could fuel inflammatory states, making chronic injuries harder to resolve and correlating with increased risk of cancer development.

“In these gastric cells, paligenosis — reversion to a stem cell state for healing — is a risky process, especially now that we’ve identified the potentially inflammatory downsizing of cathartocytosis within it,” Mills said. “These cells in the stomach are long-lived, and aging cells acquire mutations. If many older mutated cells revert to stem cell states in an effort to repair an injury — and injuries also often fuel inflammation, such as during an infection — there’s an increased risk of acquiring, perpetuating and expanding harmful mutations that lead to cancer as those stem cells multiply.”

More research is needed, but the authors suspect that cathartocytosis could play a role in perpetuating injury and inflammation in Helicobacter pylori infections in the gut. H. pylori is a type of bacteria known to infect and damage the stomach, causing ulcers and increasing the risk of stomach cancer.

The findings also could point to new treatment strategies for stomach cancer and perhaps other GI cancers. Brown and WashU Medicine collaborator Koushik K. Das, MD, an associate professor of medicine, have developed an antibody that binds to parts of the cellular waste ejected during cathartocytosis, providing a way to detect when this process may be happening, especially in large quantities. In this way, cathartocytosis might be used as a marker of precancerous states that could allow for early detection and treatment.

“If we have a better understanding of this process, we could develop ways to help encourage the healing response and perhaps, in the context of chronic injury, block the damaged cells undergoing chronic cathartocytosis from contributing to cancer formation,” Brown said.

This work was supported by the National Institutes of Health (NIH), grant numbers K08DK132496, R21AI156236, P30DK052574, P30DK056338, R01DK105129, R01CA239645, F31DK136205, K99GM159354 and F31CA236506; the Department of Defense, grant number W81XWH-20-1-0630; the American Gastroenterological Association, grant numbers AGA2021-5101 and AGA2024-13-01; and a Philip and Sima Needleman Student Fellowship in Regenerative Medicine. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

On August 8, 2024, the NSF Daniel K. Inouye Solar Telescope in Hawaii achieved a historic milestone by capturing the sharpest images ever taken of a solar flare. The unprecedented observations revealed coronal loops in stunning detail. The arches of superheated plasma following the Sun’s magnetic field lines were captured at such resolution that it’s possible to see individual structures as narrow as 21 kilometres across.

To put this achievement into perspective, these plasma loops are roughly twice the width of Los Angeles, yet they arch through space in formations that span distances equivalent to several Earth diameters. The Inouye telescope’s space piercing resolution is more than 2.5 times sharper than any previous solar telescope, finally allowing astronomers to peer into the fundamental building blocks of solar flares.

The NSF Daniel K. Inouye Solar Telescope has a 4.24-meter primary mirror in an off-axis configuration to minimise scattered sunlight. It requires over 11 kilometre of coolant piping for its active cooling systems to handle the extreme heat of direct solar observation, while adaptive and active optics systems use sensors and actuators to continuously correct for atmospheric disturbances and maintain precise mirror alignment. Ten mirrors guide sunlight throughout the observatory to four instruments designed for solar imaging and magnetic field measurements.

The Hawaiian Observatory, home to the NSF Daniel K. Inouye Solar Telescope, on the summit of Haleakalā volcano (Credit : Ekrem Canli)

The discovery came almost by accident. Cole Tamburri, a PhD student at the University of Colorado Boulder and the study’s lead author, was conducting routine observations when the X1.3-class flare erupted.

“This is the first time the Inouye Solar Telescope has ever observed an X-class flare. These flares are among the most energetic events our star produces, and we were fortunate to catch this one under perfect observing conditions,” – Cole Tamburri from University of Colorado Boulder

The telescope’s Visible Broadband Imager, tuned to capture light at a specific wavelength emitted by hydrogen atoms, revealed dark threadlike loops arching through the Sun’s corona with breathtaking clarity. The team measured loop widths averaging 48.2 kilometres, with some potentially half as narrow. These measurements represent the smallest coronal loops ever imaged.

According to Tamburri, the experience resembles going from seeing a forest to suddenly seeing every single tree. The imagery reveals dark, threadlike loops arching in glowing arcades, with bright flare ribbons etched in almost impossibly sharp relief, including a compact triangular formation near the centre and a sweeping arc across the top.

A high resolution image of the flare from the Inouye Solar Telescope, taken on August 8, 2024, at 20:12 UT. The image is about 4 Earth diameters on each side. (Credit : NSF/NSO/AURA)

For decades, theories suggested coronal loops could range from 10 to 100 kilometres in width, but confirming this observationally had been impossible until now. It finally opens the door to studying not just the sheer size of the loops but their shapes, evolution, and even the scales where magnetic reconnection, the engine behind flares, occurs.

Solar flares are among the most dangerous space weather events, capable of disrupting satellites, power grids, and communications on Earth. By understanding the structure and processes that are behind these phenomena it may just be possible to improve the models that predict when and how solar storms will impact our technology dependent world.

Perhaps most tantalising is the possibility that these newly resolved structures are elementary building blocks, the fundamental components of flare architecture. If confirmed, this discovery would mark a paradigm shift in solar physics, allowing scientists to study individual magnetic loops rather than just bundles of them.

Source : The NSF Inouye Solar Telescope Observes Its First X-Class Solar Flare and Reveals the Smallest Coronal Loops Ever Imaged

Red onion dye could be the missing ingredient required to bolster ultraviolet (UV) protection for solar cells, scientists say.

Solar cells are typically coated with a petroleum-based film to protect them from UV-induced degradation. These films include oil-based materials such as polyvinyl fluoride (PVF) and polyethylene terephthalate (PET).

Introduction

Neisseria sicca (N. sicca) typically exists as a commensal bacterium on the mucosal surface of the human upper respiratory tract (URT), with an overall oropharyngeal carriage rate of approximately 9.4%.¹ However, in recent years, with an increasing number of clinical case reports on N. sicca, it has gradually exhibited its characteristics as an opportunistic pathogen rather than just a commensal bacterium on the mucosal surface. Similar to N. meningitidis and N. gonorrhoeae, its pathogenicity may involve a series of sequential steps, including adhesion to mucosal epithelial cells, invasion of host tissues, evasion of immune defenses, and induction of inflammatory damage.^2,3 This bacterium has been reported as a cause of various human infections, including endocarditis,^4,5 pneumonia,^6,7 sinusitis,⁸ osteomyelitis,⁹ meningitis,¹⁰ conjunctivitis,¹¹ peritonitis,^12,13 and bloodstream infections (BSIs).^14,15

BSIs are systemic inflammatory response syndromes caused by the invasion of pathogenic microorganisms such as bacteria or fungi into the bloodstream.¹⁶ BSIs are associated with high mortality and increased healthcare costs.¹⁶ These infections occur not only in immunocompromised individuals but also in healthy populations. Infectious endocarditis can serve as a nidus for ongoing BSIs because microorganisms colonizing the heart valves continuously disseminate into the bloodstream.¹⁷ This may exacerbate BISs, leading to a vicious cycle of infection and inflammation. Based on the previous literature regarding infections caused by N. sicca, endocarditis constitutes the majority of cases.¹⁸ Therefore, detection of N. sicca in the bloodstream warrants vigilance for potential endocardial diseases.

In a decade-long review of ~8,000 bacteremia cases, Feder et al identified only one N. sicca-positive culture that was ultimately deemed a contaminant.¹⁹ While BSIs caused by N. sicca are uncommon, sporadic cases have been reported. Shaw et al first reported a case of N. sicca endocarditis in a 12-year-old patient.²⁰ Subsequent studies have also described true BSIs caused by this organism, though such occurrences remain uncommon.^5,18,21 These reports suggest N. sicca possesses greater pathogenic potential than is traditionally recognized.

Severe cardiac valve degeneration, including stenosis and regurgitation, often necessitates artificial valve replacement, yet this intervention carries a markedly increased risk for BSIs and endocarditis. Previous studies have reported BSI rates of ~8% after valve repair or replacement, of which 13–14.3% subsequently develop endocarditis.^22,23 Following aortic valve replacement (AVR), BSIs occur in approximately 10.1% of patients, of which nearly 40% progress to endocarditis.²⁴ The predominant causative organisms include gram-positive cocci—such as viridans group streptococci, β-hemolytic streptococci, coagulase-negative staphylococci (CoNS), methicillin-sensitive Staphylococcus aureus (MSSA), and Enterococcus spp.—and gram-negative bacilli, including Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.²⁴ Recent reports have also documented rare cases of Neisseria elongata endocarditis in patients with AVR.^25,26

In this study, we report a rare case of BSIs caused by the N. sicca strain junzhu_1 of unknown origin in a patient with a seven-year history of AVR. Whole-genome sequencing was performed to gain a deeper understanding of its pathogenicity and antimicrobial resistance. This case underscores the importance of recognizing N. sicca as an opportunistic pathogen in clinical settings.

Materials and Methods

Bacteria Isolation and Identification

Blood samples were inoculated into both aerobic and anaerobic blood culture bottles, and subsequently incubated in a BACT/ALERT 3D blood culture system (bioMérieux, France). Once a positive result was obtained, Gram staining was performed directly from the bottle, and the broth was plated onto 5% sheep blood agar. The agar plates were then incubated at 37°C for 18–24 hours. The bacterial isolate was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) (bioMérieux, France) with 99.99% confidence. 16S rRNA-based taxonomic confirmation was performed by extracting and analyzing the corresponding genomic sequences from whole-genome assemblies using barrnap (https://github.com/tseemann/barrnap) with default parameters.

Antibiotic Susceptibility Assay

Antibiotic sensitivity testing was performed using the encompassed ten antibiotics: amoxicillin-clavulanate, ampicillin, tetracycline, cefotaxime, cefuroxime, rifampin, trimethoprim-sulfamethoxazole, chloramphenicol, cefaclor, and ofloxacin. MIC values were determined using ATB HAEMO CLSI (12) strips (bioMérieux, France) in accordance with the manufacturer’s guidelines, and susceptibility was interpreted based on the breakpoints outlined in the US Clinical and Laboratory Standards Institute (CLSI) M100-S34 (2024) standards. Furthermore, the Kirby (K-B) disk diffusion method was employed to test for azithromycin and erythromycin.

Public Sequence Data

Whole-genome sequences of N. sicca were retrieved from GenBank using the search term “Neisseria sicca” with a genome length restriction of 1–10 Mb, yielding 28 available strains. Following a comprehensive evaluation of assembly metrics and annotation status, we selected 22 high-quality genomes for downstream comparative genomic analysis.

Whole Genome Sequencing and Bioinformatics Analysis

Total DNA of the N. sicca junzhu_1 isolate was extracted from pure cultures using a bacterial DNA extraction kit (Bacterial/Fungal DNA Extraction Kit [Magnetic Beads], China). A next-generation sequencing library was prepared using the NEBNext®Ultra™ DNA Library Prep Kit for Illumina (NEB, USA) (350 bp fragment library, paired-end) in accordance with the manufacturer’s recommendations. The whole-genome sequence of N. sicca was obtained using the Illumina HiSeq 4000-PE150 platform (Illumina, Inc., USA), followed by assembly using Unicycler v. 0.5.0 (https://github.com/rrwick/Unicycler). The genome was annotated using the Prokaryotic Genome Annotation tool (Prokka v.1.14.6) (https:// github.com/ tseemann/prokka).

Antimicrobial Resistance and Virulence Analysis

We identified virulence and antibiotic resistance factors using the Virulence Factor Database (VFDB) (http://www.mgc.ac.cn/VFs/) and the Comprehensive Antibiotic Research Database (CARD) (https://card.mcmaster.ca/).

Phylogenetic Analysis

To characterize the evolutionary relationships among the 23 N. sicca isolates in a global context, we utilized CSI Phylogeny 1.4 for phylogenetic analyses (https://cge.food.dtu.dk/services/CSIPPhylogeny/). The phylogenetic tree was visualized and modified using iTOL (https://itol.embl.de).

Result

Case Presentation

A 73-year-old female with a 7-year history of AVR was admitted on November 8, 2023, with a one-day history of chills and high fever. Laboratory tests revealed a white blood cell (WBC) count of 17.1 × 10⁹/L with neutrophilia (85.6%), markedly elevated C-reactive protein (CRP, 160.6 mg/L), and elevated procalcitonin (PCT, 1.53 ng/mL). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Mycoplasma pneumoniae tests were negative. Cytokine analysis showed significantly elevated interleukin-6 (IL-6, 566.10 pg/mL) and interleukin-10 (IL-10, 3888.73 pg/mL). Sputum cultures revealed normal respiratory flora, including N. sicca (1+). Blood culture yielded N. sicca, and chest computed tomography (CT) revealed an infectious lesion in the right lung (Figure 1A and D). The patient was diagnosed with pneumonia and bacteremia. The patient was administered ticarcillin-clavulanate (3.2 g q8h, IV). After one week of treatment, the patient no longer had fever, cough, or sputum production. Follow-up chest CT indicated resolution of the infectious lesion in the right upper lung (Figure 1B). Oral amoxicillin-clavulanate therapy was continued for 4 days after discharge.

Figure 1 CT imaging changes between the two hospital admissions. (A) Local infectious lesion in upper lobe of right lung (red arrow); (B) Infectious lesion absorption in upper lobe of the right lung; (C) No infectious lesions in right upper lung lobe; (D) Plain transverse image of mediastinal window.

On December 11, 2023, the patient was readmitted to our hospital because of persistent high fever accompanied by chills for a day. Upon presentation, the patient had a body temperature of 39.1°C, a heart rate of 97 beats per minute, and a blood pressure of 113/53 mmHg. No symptoms of cough, sputum production, chest tightness, or shortness of breath were observed. Both lungs exhibited clear respiratory sounds, with no audible rales. The abdomen was soft and non-tender without rebound pain, and the liver and spleen were not palpable. The patient denied any symptoms, such as abdominal pain, diarrhea, urinary frequency, urgency, or dysuria. CT revealed multiple small nodules in both lungs with no inflammatory lesions (Figure 1C). Transthoracic echocardiography (TTE) revealed valvular dysfunction and aortic valve replacement with no vegetation (Figure 2).

Figure 2 Echocardiogram showed no vegetation on the valves. (A) The artificial aortic valve image (red arrow); (B) The left ventricular long-axis section image; (C) Apical precordial four chamber view of the first admission; (D) Apical precordial four chamber view of the second admission.

Laboratory tests showed a WBC count of 13.5 ×10⁹/L, neutrophil ratio of 80.8%, hemoglobin of 109 g/L, platelet count of 129 × 10⁹/L, CRP of 158.0 mg/L, troponin I of 0.034 ng/mL, brain natriuretic peptide (BNP) of 795 ng/L, and PCT of 8.10 ng/mL. Tests for SARS-CoV-2, influenza A virus, adenovirus, respiratory syncytial virus, and influenza B virus antigens were all negative. Prior to initiating empiric antimicrobial treatment with ticarcillin-clavulanate (3.2 g q8h IV) for eight days, two sets of aerobic and anaerobic blood cultures were performed. On the following day, sputum culture showed normal respiratory flora, and four culture bottles were positive for gram-negative Diplococcus (Figure 3A, B and D). The organism grew on blood agar as irregular, elevated, smooth, dry, opaque, and yellowish colonies (Figure 3C). The isolated organism (N. sicca junzhu_1) was identified using MALDI-TOF MS and verified using 16S rRNA sequencing. Sepsis was diagnosed on the basis of the presence of this organism in the bloodstream. Antibiotic sensitivity testing indicated sensitivity to the current antibiotics, and the treatment was continued (Table 1).

Table 1 MIC Values (µg/Ml) of N. Sicca Junzhu_1

Figure 3 General overview of Neisseria sicca. (A and B) Growth curve of N. sicca under anaerobic (A) and microaerobic (B) conditions, respectively. (C) Columbia blood agar plate with growth of N.sicca. (D) Staining revealed Gram-negative diplococcus.

After 8 days of treatment, the patient showed overall improvement with no fever or other symptoms. Follow-up blood culture results were negative. Pre-discharge blood tests showed a WBC count of 6.6×10⁹/L with a neutrophil ratio of 71.9%, CRP of 55.3 mg/L, and PCT of 0.99 ng/mL. The patient was discharged with instructions to continue oral amoxicillin-clavulanate for one week and to follow up regularly in the outpatient clinic. During the 18-month post-discharge follow-up period, the patient remained afebrile with no recurrence of cough or other infectious symptoms.

General Genomic Features of N. sicca Junzhu_1

The genome of N. sicca junzhu_1 comprises 2,420,190 bp and exhibits a G+C content of 51.21%. The strain was predicted to have 68 contigs, 2129 coding sequences (CDSs), and 61 RNA genes [58 tRNAs, one 5S rRNA, one 16S rRNA, and one 23S rRNA]. The genome sequence of N. sicca junzhu_1 has been deposited in NCBI GenBank under the accession number SRR29061210.

The Antimicrobial Resistance of N. sicca Junzhu_1

N. sicca junzhu_1 is susceptible to a variety of antimicrobial agents including amoxicillin-clavulanate, ampicillin, tetracycline, cefotaxime, cefuroxime, rifampin, trimethoprim-sulfamethoxazole, chloramphenicol, cefaclor, and ofloxacin. However, the strain was resistant to azithromycin and erythromycin (Table 1). Consistent with these findings, the resistome of N. sicca junzhu_1 comprised three antimicrobial resistance genes: macB, macA, and mtrD (Figure 4).

Figure 4 Distribution of antimicrobial resistance genes among 23 N. sicca isolates. Green rectangles indicate the presence of resistance genes in the corresponding isolates.

Virulence Genes in N. sicca Junzhu_1

Virulence gene analysis showed that the pathogenicity of N. sicca junzhu-1 was related to the MntABC pathway (mntB and mntC), efflux pump system (farA, farB, mtrD, and mtrE), oxidative damage (msrA/B [pilB]), lipooligosaccharide synthesis pathway (rfaF and rfaC), membrane receptor (hpuB), motor protein (pilT), catalase (KatA), and DNA repair(recN), which may be related to the poor prognosis of infection.

Phylogenetic Analysis of 23 N. sicca Strains

To elucidate the phylogenetic relationships between Neisseria strains from different regions and our strain, junzhu_1, 22 genomic datasets from the NCBI database (Table S1), and the sequence of junzhu_1 were used to construct a phylogenetic tree. These isolates were primarily distributed in the USA (17, accounting for 73.91%), and the majority of hosts from which they were isolated were humans (n=19, 82.61%). The isolates were obtained from various samples, including oral cavity, nasopharynx, blood, urine, and duodenal aspirates. Phylogenetic analysis revealed that the two strains most closely related to the isolated strain junzhu_1 were GCA_007673275 and GCA_017753665. Strain GCA_017753665 was recovered from a blood sample in Zhejiang, China, and differed by 3585 single nucleotide polymorphisms (SNPs) in the same region (Figure 5).

Figure 5 Recombination-filtered core genome phylogeny for a total of 23 Neisseria sicca isolates worldwide deposited in the NCBI GenBank database. The isolation date, host, source and country are represented by squares of different colors. The isolate junzhu_1 recovered in this study is highlighted in red font.

Discussion

This case report presents a patient with a history of AVR who was confirmed to be infected with N. sicca, the origin of the infection remains elusive.

Upon admission, the patient presented with a localized inflammatory lesion in the right lung lobe, as revealed by chest CT. Blood cultures were positive for N. sicca, whereas sputum cultures revealed the presence of normal upper respiratory tract flora, including N. sicca. Unfortunately, bronchoalveolar lavage fluid was not obtained from the bacterial culture. While the exact cause of the lesion is uncertain, N. sicca infection is a possible contributor, as it has been reported to cause pneumonia in prior cases.^6,7 Following antibiotic treatment, the pulmonary lesion resolved completely and the patient’s temperature normalized. However, the patient was readmitted one month later with fever, and subsequent blood cultures again detected N. sicca, CT imaging showed no pulmonary or other lesions. Comparative echocardiography from both admissions showed no evidence of vegetation on the cardiac valves.

Diagnosing prosthetic valve endocarditis is challenging and requires multiple imaging techniques beyond standard microbiological analysis.²⁷ The complexity arises from device-related infection characteristics, biofilm formation, and limitations in imaging interpretation.^27,28 Considering the possibility of infective endocarditis, a negative TTE result does not definitively exclude the diagnosis, as vegetations may be too small, located in atypical positions, or obscured by suboptimal image quality. Therefore, transesophageal echocardiography (TEE) should be considered, alongside other diagnostic modalities such as cardiac CT or PET/CT, to confirm or rule out occult infective endocarditis.²⁹

To our knowledge, only two cases of BSIs caused by N. sicca following AVR have been reported. Cheng et al³⁰ described a male patient with a history of AVR who presented with 10-day fever. Although TTE was negative for vegetation, TEE revealed vegetation on the aortic valve. The isolated N. sicca was found to be sensitive to meropenem, trimethoprim-sulfamethoxazole, chloramphenicol, and minocycline, but resistant or insensitive to penicillin, azithromycin, ciprofloxacin, and cefuroxime. After an 8-week treatment regimen, the patient’s blood cultures were negative, and the follow-up TEE showed no evidence of vegetation. Locke et al³¹ reported the case of a female patient with a history of AVR and pacemaker implantation who presented with recurrent fever. Although TTE was negative, TEE revealed two vegetations in the lead of the right atrial pacemaker. The patient subsequently underwent complete pacemaker and lead extraction, received initial intravenous ertapenem, and was later transitioned to ceftriaxone. The patient fully recovered and was discharged after completing a 6-week course of intravenous cefuroxime at home.

We retrieved 22 N. sicca sequences from GenBank and analyzed them together with the strain junzhu_1 from this study. Most strains were of human origin (n = 19), followed by environmental sources (n = 3), with one strain of unknown origin, suggesting that N. sicca can inhabit both human hosts and environmental niches. Within humans, it primarily colonizes the upper respiratory tract but has also been isolated from blood, the gastrointestinal tract, and urine. Notably, two bloodstream-derived strains were identified, including junzhu_1 and NS20201025 (GCA_017753665.1). Phylogenetic analysis revealed that NS20201025, one of the closest relatives of junzhu_1, was isolated from Zhejiang—the same geographic region as our strain. This strain has been reported to cause native-valve endocarditis complicated by multiple embolic cerebral infarctions in a patient with underlying heart disease. Collectively, these findings suggest that the strain junzhu_1 may have pathogenic potential for infective endocarditis.

In the present study, we performed whole-genome sequencing of the isolated N. sicca junzhu-1 strain to further study its pathogenicity and resistance. N.sicca junzhu-1 harbors virulence factors, including fatty acid efflux system genes (MtrCDE and FarAB-MtrE), Type IV pili (PilT), lipooligosaccharides (involving rfaC and rfaF genes), and reactive oxygen species (ROS) defense mechanisms (involving Recn, KatA, MntABC, and MsrA/B). These virulence genes are also present in the genomes of pathogenic N. gonorrhoeae and N. meningitidis and may contribute to poor infection prognosis.

MtrCDE and FarAB-MtrE efflux pumps enhance resistance against host-derived long-chain fatty acids by relying on the outer membrane protein MtrE for export. The expression of these pumps may be differentially regulated by the transcriptional regulatory protein MtrR.³² Type IV pili (TFP) are crucial for bacterial attachment to host cells, with PilT proteins mediating retraction and intimate attachment.³³ Lipooligosaccharides (LOS) are key virulence factors that are involved in immune evasion, tissue attachment, and host cell invasion. Its biosynthesis involves branched oligosaccharide production linked to lipid A via two 3-deoxy-D-manno-2-octulosonic acid (KDO) molecules, with rfaC and rfaF playing essential roles.³⁴ ROS play crucial roles in bacterial physiology and stress responses. Both N. meningitidis and N. gonorrhoeae possess ROS defense mechanisms essential for survival. These include RecN (a putative zinc metalloprotease), KatA (catalase), MntABC (an ABC-type Mn transporter), and MsrA/B (methionine sulfoxide reductases), which collectively contribute to ROS detoxification.³⁵ Płaczkiewicz et al³⁶ demonstrated that both N. gonorrhoeae and N. sicca induce the secretion of pro-inflammatory cytokines, including IL-6 and TNF-α, as well as chemokines CXCL8 and CCL20, in infected epithelial cells. A study³⁷ found that commensal species of Neisseria, specifically N. sicca and N. lactamica, can cause toxic damage to cultured human endothelial cells. Considering the virulence factors of N. sicca and its ability to elicit inflammatory responses, a potential link exists between its pathogenicity and its ability to cause BSIs.

Recent research suggests that commensal Neisseria species serve as reservoirs for antibiotic resistance genes, particularly those conferring resistance to azithromycin and erythromycin, which can be horizontally transferred to pathogenic Neisseria species.³⁸ Consistent with this, N. sicca junzhu_1 harbored resistance determinants-including macB, macA, and mtrD-that are associated with resistance to both azithromycin and erythromycin. N. lactamica harbors mutated gyrA and penA, leading to resistance to quinolones and penicillin, respectively.³⁹ One study found that the blaTEM gene, responsible for β-lactamase production, was present in 93.9% of Neisseria spp. isolates, all of which showed resistance to penicillin.⁴⁰ Genomic analysis of the 23 N. sicca isolates revealed resistance patterns, all of which harbored multiple macrolide resistance genes (including mtrC, mtrD, marA, marB, and lsaC), whereas specific isolates carried additional β-lactamase genes (TEM-1 in strains GCA_003044345 and GCA_019334765; TEM-50 in GCA_963456655) (Figure 4). Fortunately, most blaTEM-positive commensal Neisseria spp. are susceptible to cephalosporins.⁴⁰ However, the commensal species, N. cinerea and N. elongata, demonstrated resistance to ceftriaxone.³⁸

To the best of our knowledge, published reports indicates that N. sicca is generally susceptible to third-generation cephalosporins, β-lactamase inhibitors, penicillins, and quinolones. However, no CLSI criteria are currently available for this organism, and breakpoints for Neisseria meningitidis were therefore applied as a reference in susceptibility testing. In patients with AVR who develop BSIs concomitant with infective endocarditis, treatment poses additional challenges due to the potential formation of bacterial biofilms on prosthetic materials, which can reduce antibiotic efficacy and increase the risk of persistent infection.⁴¹ Therefore, combination therapy—including aminoglycosides or rifampin—may be considered to enhance antimicrobial activity and target biofilm-associated bacteria,^42,43 with the final regimen tailored according to local resistance patterns and individual susceptibility results.

This case report had several limitations. First, the definitive diagnosis of endocarditis in our patient remains elusive, as we lacked TEE and other advanced imaging modalities such as cardiac CT or PET/CT, relying solely on TTE. Second, in the absence of CLSI susceptibility breakpoints for N. sicca, we used ATB HAEMO CLSI (12) strips, referring to the susceptibility breakpoints for Haemophilus influenzae. Third, although the virulence genes of N. sicca have been identified through whole-genome sequencing, their expression levels have not yet been verified using qPCR. Furthermore, we did not perform in vivo animal model experiments to validate virulence.

Conclusions

In summary, this case study provides the first genomic insight into the virulence and resistance characteristics of N. sicca implicated in BSIs in patients with AVR. These findings provide valuable information for future research on the pathogenicity and antibiotic resistance mechanisms of this microorganism in clinical contexts. Although N. sicca is generally susceptible to β-lactams, determining its sensitivity is highly advisable for guiding appropriate therapies. N. sicca commonly resides as a commensal bacterium on the mucosal surface of the human URT. However, its potential pathogenicity, particularly in BSIs arising from underlying heart valve disease, warrants further investigation.

Data Sharing Statement

Data supporting the findings of this study are openly available at https://trace.ncbi.nlm.nih.gov/Traces/index.html?view=run_browser&acc=SRR29061210&display=metadata reference number SRR29061210.

Ethics Approval and Consent to Participate

Whole genome sequencing, along with a case report, was approved by the Ethics Committee of Sanmen People’s Hospital in Taizhou, China.

Patient Consent for Publication

The patient provided written informed consent for the publication of case details and accompanying images.

Funding

This research received no external funding.

Disclosure

The authors declare that they have no competing interests in this work.

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Deep beneath the ocean’s surface lies a phenomenon, only a few of us ever think of. A place where tectonic forces influence the fate of continents and coastlines. Scientists are reaching into these extreme depths, looking for clues on how massive earthquakes and huge tsunamis begin.Many years later, the scientist have reached the fault that unleashed one of through miles of dark water and sediment to reach a fault that, in 2011, unleashed one of the most devastating tsunamis in modern history to better predict Earth’s violent tantrums, to understand how faults heal, and to protect vulnerable communities from future disasters.

Drilling into the deep to understand tsunamis

According to the press release by the project, between September and December 2024, IODP Expedition 405, known as JTRACK or Tracking Tsunamigenic Slip Across the Japan Trench, began an ambitious mission. Aboard the Japanese drilling vessel Chikyu, the world’s most advanced deep-sea drilling ship, 60 scientists probed nearly seven kilometers beneath the Pacific Ocean to explore the fault behind the devastating 2011 Tōhoku earthquake and tsunami.

Reaching the earthquake’s weak point

The team drilled into the décollement, the base layer of the fault where the earthquake’s slippage began. They retrieved sediment and rock cores reaching more than 800 meters below the seafloor, giving a rare look into the physical conditions that triggered the disaster.

Building a real-time observatory in the abyss

Not stopping at core samples, the expedition also installed a long-term borehole observatory to monitor temperature and fluid pressure at the fault site over time. These measurements can reveal changing stress patterns, which are the key data for understanding how faults recharge and potentially fail again.

What the cores reveal

Scientists on board received core samples every few hours, analyzing them to trace signs of past earthquakes, tsunamis, and underwater landslides. In particular, they noted layers rich in certain clay minerals, which may ease fault slippage. They also observed chart layers, marking the transition between oceanic sediments and the underlying crust, which symbolises the geological complexity at play.

Why does this matter beyond Japan

This expedition revisited a site explored just after the 2011 quake, and it helped scientists to see how the fault has changed over more than a decade. The data collected from JTRACK aren’t just relevant to Japan; they help scientists better understand similar subduction zones in Chile, Alaska, and Indonesia, where shallow fault slip also threatens coastal communities.

The fault has healed over time

Initial results suggest that fault rocks damaged in 2011 may have partially re-cemented, reducing fluid flow, but potentially storing mechanical energy for future events. Understanding this “healing” process is crucial for anticipating seismic risks over time.

Astronomers have zoomed in on small loops of plasma within a powerful solar flare for the first time, potentially revealing the fundamental building blocks of the sun‘s violent storms. 

The images, captured with the new Daniel K. Inouye Solar Telescope in Hawaii, reveal arcs of hot gas just 10 to 30 miles wide that follow the sun’s magnetic fields. Earlier instruments could only resolve loops 60 to 100 miles wide. Inouye’s images are over 2.5 times sharper.

Scientists believe these so-called “coronal loops” may in fact be the most basic pieces of solar flares — sudden explosions of energy that hurl a torrent of radiation into space and toward Earth.

The discovery is giving a new window into how our host star makes flares in the first place. Gathering such insight may lead to better space weather forecasts, perhaps preventing future solar storms from wreaking havoc on satellites, power grids, and radio signals.

“Knowing a telescope can theoretically do something is one thing,” said Maria Kazachenko, a co-author in the study, in a statement. “Actually watching it perform at that limit is exhilarating.”

The solar observatory sits atop a dormant volcano, Haleakalā, towering over Maui at 10,000 feet above sea level. Fittingly, the name Haleakalā means “house of the sun” in Hawaiian. But that’s not why the site was selected for the telescope. The summit has special environmental conditions that allow astronomers to better view the sun’s corona, the outer layer of its atmosphere. 

For the study, published in The Astrophysical Journal Letters, the team measured 686 loops. They found the loops’ widths tended to be similar in thickness, rather than a random mix. This suggests the telescope may finally be seeing the tiniest parts of a solar flare. 

Mashable Light Speed

Taken in August 2024 during an X-class flare, the images show dark, threadlike arches rising over glowing flare ribbons. 

Scientists have long believed that solar flares are made up of many little magnetic loops. But up until now, those loops were impossible to see. Researchers could only theorize that they existed.  

If the team has indeed found the fundamental components of a solar flare — and not just larger bundles of loops — it’s a breakthrough for solar storm forecasters, said Cole Tamburri, the paper’s lead author. The data that could come from studying them in greater detail could improve computer models for predicting space weather. 

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“It’s like going from seeing a forest to suddenly seeing every single tree,” Tamburri said. 

Just as Earth has seasons, the sun goes through an 11-year cycle of activity. It is quietest at the beginning and end of the cycle, but in the middle, it grows turbulent, unleashing powerful eruptions.

That peak just came, with solar activity hitting its maximum around October 2024. As a result, solar flares, along with massive blasts of plasma from the corona, have made headlines more frequently.

Even at 93 million miles away, the sun’s outbursts can affect Earth and the rest of the solar system. The planet’s atmosphere and magnetic field shield people from the worst radiation, but these events can still have catastrophic consequences for life on Earth, interfering with telecommunications, navigation systems, and other critical technology. 

Such events are rare but memorable. In March 1989, for example, a major flare knocked out power across Quebec, Canada, for 12 hours and even disrupted Radio Free Europe broadcasts.

Turtles and tortoises are both reptiles with shells, but they’re not exactly the same. So how can you tell them apart? What’s the difference between a turtle and a tortoise?

“All tortoises are turtles, but not all turtles are tortoises,” Sydnee Fenn, a reptile keeper at Columbus Zoo and Aquarium, told Live Science. Generally, the reptiles that people call turtles spend a great deal of time in the water, whereas tortoises live on land, according to Genius Vets in San Diego, California.

Absence of D2Rs increases compulsive-like eating

We evaluated compulsive-like eating in wild-type (WT) and dopamine D2R knock-out (Drd2^−/−) mice by employing a palatable food (PF) self-acquisition task. When a mouse pressed the active lever, a sucrose pellet (i.e., PF) was delivered. After 7 days, the number of lever presses required to obtain PF was increased, shifting from a fixed ratio of 1 (FR1) to FR2 and FR3 training schedules (Fig. 1A). Both groups successfully acquired lever pressing as the sessions progressed (Fig. 1B, C), although Drd2^−/− mice displayed slightly less active lever pressing than WT mice across sessions, probably due to decreased locomotor activity in these mice [27]. During FR1 to FR3 sessions, both WT and Drd2^−/− mice exhibited significantly increased active lever pressing than inactive lever press, demonstrating that the increase in lever pressing is specific to PF-seeking (Supplementary Fig. 1B–E).

After the FR3 sessions, additional FR3 sessions with delivery of electric foot shock (FS) were administered (FR3 + FS), and the perseverance of lever pressing to obtain PF despite the delivery of foot shocks was used as an indicator of compulsive-like food-seeking. Surprisingly, Drd2^−/− mice exhibited significantly higher active lever pressing despite receiving foot shocks (Fig. 1B, D), showing perseverance in reward-seeking despite punishment. In contrast, WT mice exhibited significantly increased inactive lever press compared to active lever during FR3 + FS sessions (Supplementary Fig. 1F). When the rewards were omitted and only foot shocks were delivered (FS only), lever pressing was comparable between WT and Drd2^−/− mice (Fig. 1B, E, Supplementary Fig. 1B, G), indicating similar sensitivity to foot shocks, but greater compulsivity in Drd2^−/− mice, driving active lever pressing despite punishment. These data, together with previous observations [11], indicate that the absence of D2Rs promotes compulsive-like eating behavior.

CeA D2Rs regulate compulsive-like eating

To further address the role of D2Rs in the control of compulsive eating, we targeted D2Rs in the CeA based on our previous finding that CeA D2Rs play a crucial role in reward-related impulsive and compulsive behaviors [11]. We generated Drd2 ^flox/flox mice (Supplementary Fig. 2) and injected AAV-Cre-eGFP virus into the CeA to selectively eliminate D2R expression in the CeA (CeA-Drd2KO mice) (Fig. 1F), resulting in a 73% reduction in D2R expression in CeA-Drd2KO mice (Cre-GFP) compared with control flox mice in which AAV-eGFP virus was injected (CeA-Drd2WT, GFP) (Fig. 1G, H). We then trained mice in the PF self-acquisition task.

Both control (GFP) and CeA-Drd2KO (Cre-GFP) mice displayed successful FR1-FR3 performance with no difference between groups (Fig. 1I, J, Supplementary Fig. 3B–E). However, CeA-Drd2KO mice (Cre-GFP) showed more active lever pressing than CeA-Drd2WT mice (GFP) during the FR3 + FS sessions (Fig. 1I, K) while CeA-Drd2WT mice exhibited significantly increased inactive lever press compared to active lever during FR3 + FS sessions (Supplementary Fig. 3F). In FS-only sessions, both CeA-Drd2WT and CeA-Drd2KO mice showed low levels of lever pressing (Fig. 1I, L, Supplementary Fig. 3G). Taken together, these data suggest that D2Rs in the CeA critically contribute to the compulsive-like perseverance of PF-seeking behavior.

CeA D2Rs regulate InsR signaling

Recent reports indicate that InsRs are highly expressed in the CeA and are associated with reduced food intake [28,29,–30]. Using Drd2-EGFP mice, we observed abundant expression of InsRs in the CeA and found that ~61% of CeA D2R- expressing neurons co-expressed InsRs (Fig. 2A, B). Interestingly, in Drd2^−/− mice, InsR expression was decreased to 42% in the CeA compared with WT mice (Fig. 2C, D). In addition, in CeA-specific Drd2 KO (CeA-Drd2KO) mice, InsR expression was reduced by ~60% compared with control CeA-Drd2WT mice (Fig. 2E–G).

We next examined InsR activity by assessing insulin-mediated phosphorylation of InsRs in the CeA of CeA-Drd2WT (Drd2^flox/flox + GFP) and CeA- Drd2KO (Drd2^flox/flox+Cre-GFP) mice as well as the possible regulation of InsR phosphorylation by a D2R agonist. We analyzed phosphorylation of Tyr-972 (pInsR^Tyr972), an important residue for the recruitment of IRS-1, phosphorylation of Tyr1162/1163 (pInsR^Tyr1162/1163) in the activation loop of the InsR catalytic domain [31, 32], and phosphorylation of Akt (pAkt^Ser473) in the downstream InsR signaling cascade [32]. After 12 h of food deprivation, saline, insulin (10 mU), or D2R agonist quinpirole (1 μg) were infused into the CeA. A robust increase in the number of pInsR^Tyr972-positive cells was observed 30 min after insulin or quinpirole infusion in CeA-Drd2WT mice (Drd2^flox/flox + GFP), whereas CeA-Drd2KO mice (Drd2^flox/flox+Cre-GFP) showed higher basal levels of pInsR^Tyr972-positive cells, but no increase after insulin or quinpirole infusion (Fig. 2H, I, Supplementary Fig. 4A). Insulin or quinpirole infusion significantly increased the number of pInsR^Tyr1162/1163-positive cells in the CeA of CeA-Drd2WT mice (GFP). By contrast, CeA-Drd2KO mice (Cre-GFP) showed a higher basal level of pInsR^Tyr1162/1163-positive cells, but insulin or quinpirole infusion had little or no effect on their levels (Supplementary Fig. 4B, D, E). Insulin or quinpirole infusion significantly increased the number of pAKT^Ser473-positive cells in the CeA of CeA-Drd2WT mice but not in CeA-Drd2KO mice (Fig. 2J, Supplementary Fig. 4C, D).

To understand how the D2R activation induces the tyrosine phosphorylation of InsRs, we hypothesized that D2R activation with Gi protein coupling promotes the phosphorylation of InsRs. Several studies demonstrate that the cAMP-inhibiting Gi proteins, including G_αi2, positively regulate InsR activation [33,34,35,–36]. By contrast, the expression and activity of protein-tyrosine phosphatase 1B (PTP1B) is decreased in tissue expressing constitutively active Gα_i2 [37]. We examined the involvement of PTP1B by analyzing the phosphorylation level of PTP1B at Ser50 (pPTP1B^Ser50), which negatively modulates its phosphatase activity, thus creating a positive feedback mechanism for insulin signaling [38]. We observed that D2R activation by quinpirole significantly increased the number of pPTP1B^Ser50-positive cells in CeA-Drd2WT (Drd2^flox/flox + GFP) mice, whereas insulin or quinpirole infusion had little or no effect on number of pPTP1B^Ser50-positive cells in CeA-Drd2KO mice (Drd2^flox/flox+Cre-GFP) (Fig. 2K, L and Supplementary Fig. 4F). These data suggest that D2R activation induces PTP1B inhibition and impairs its ability to dephosphorylate InsRs, leading to increased insulin signaling. Thus, the stimulation of CeA D2Rs may induce concomitant activation of InsR signaling in the CeA, and the absence of D2Rs severely impairs InsR signaling.

CeA InsRs impact compulsive-like eating

We next tested the effect of selective loss of InsR expression in CeA D2R- expressing neurons on compulsive-like eating behavior. To accomplish this, we used a gene knockdown strategy with Cre-dependent AAV vectors expressing a short-hairpin RNA (shRNA) targeting InsRs to induce cell type-specific loss of function while simultaneously visualizing recombination through mCherry labeling using AAV-DIO-DSE-mCherry-PSE-shInsR [39]. Selective expression of shInsR in D2R- expressing neurons in the CeA (CeA-D2R^shInsR) resulted in an ~80% reduction in InsR expression compared with control mice in which AAV-DIO-eYFP was injected (CeA-D2R^eYFP) (Fig. 3A–C). We found that D2R-specific loss of InsRs in the CeA exacerbated compulsive-like eating phenotype, as evidenced by robust perseverance of active lever pressing despite foot shock punishment (Fig. 3D–F, Supplementary Fig. 5B–F). In FS-only sessions, no difference in lever pressing was observed between control and CeA-D2R^shInsR mice (Fig. 3D, G, Supplementary Fig. 5G). Together, these data suggest that InsRs and the interaction between InsRs and D2Rs in the CeA are critical for the control of compulsive-like eating behavior.

PF and insulin modulate CeA D2R-expressing neuronal activity

To understand how CeA D2R-expressing neurons respond to PF, we used fiber photometry to perform in vivo calcium imaging. We virally expressed the Cre- dependent calcium indicator GCaMP6s (AAV-DIO-GCaMP6s-mCherry) in the CeA of Drd2-Cre mice (Fig. 4A) and recorded changes in GCaMP6s fluorescence signal through an optic fiber placed above CeA D2R-expressing neurons during exposure to PF in a light/dark box test. Histological analysis revealed that ~96% of GCaMP6-expressing cells overlapped with Cre-expressing CeA D2R-expressing cells (Fig. 4B, C). After measuring baseline body weight and food intake, mice underwent a pre-test without food for 15 min to measure their time spent in the light and dark chambers of the light/dark box [11]. Mice were then divided into two groups: one group was fed a NC diet, and the other group was fed a PF diet high in sugar and fat ad libitum for 14 days. After a 48-h PF withdrawal, mice were returned to the light/dark box for 15 min, with PF placed in the light chamber, to assess compulsive-like eating behavior [11], during which we recorded GCaMP signals from CeA D2R-expressing neurons (Fig. 4D). As shown by peri-event time histogram (PETH) analysis, there was a significant decrease in z-score (i.e., normalized ΔF/F) during PF consumption (Fig. 4E, G), whereas no significant change in GCaMP signal was observed during exposure to NC (Fig. 4E, F), indicating a decrease in CeA D2R-expressing neuronal activity in response to PF. This suppression was accompanied by increased PF intake in the light chamber, supporting a link between reduced D2R neuron activity and compulsive-like eating behavior (Fig. 4H).

We next recorded changes in the GCaMP6s signal from CeA D2R-expressing neurons during exposure to PF in the light/dark box test after infusion of saline, quinpirole, insulin, quinpirole+insulin, or the D2 receptor antagonist sulpiride into the CeA (Fig. 5A). Under saline infusion, CeA D2R neurons exhibited significantly reduced activity during PF consumption (Fig. 5B, C), consistent with the dynamics observed in Fig. 4E, and G. Quinpirole or insulin infusion, also induced significant reductions in z-scores during PF consumption (Fig. 5D–F) which was accompanied by a reduction in PF consumption (Fig. 5D–F, L). However, when quinpirole and insulin were co-infused, the suppression of neuronal activity was alleviated (Fig. 5D, G, L) corresponding to reduced PF consumption. In contrast, sulpiride infusion resulted in a significant suppression of neuronal activity and an increase in PF consumption (Fig. 5H, I, L), while its effect was slightly reversed by quinpirole (Fig. 5H, J, L) and fully alleviated by quinpirole+insulin, which also reduced PF consumption (Fig. 5H, K, L). These data indicate that D2R activation in the presence of insulin effectively enhances CeA D2R-expressing neuronal activity, thereby contributing to the suppression of PF consumption.

We further explored the effect of insulin on CeA D2R neuronal activity by ex vivo electrophysiological recordings in brain slices from Drd2-EGFP mice. Bath application of quinpirole alone (10 µM) failed to significantly change the membrane excitability of D2R-expressing CeA neurons (Supplementary Fig. 6A–E). CeA D2R neurons did not show significant changes in rheobase or membrane potential. However, when co-treated with insulin (500 nM), quinpirole dramatically depolarized their resting membrane potential and increased their excitability, as shown by decreased rheobase and enhanced input resistance (Supplementary Fig. 6C–E). When insulin alone was perfused into the recording chamber, it significantly hyperpolarized the resting membrane potential of CeA D2R neurons and decreased their firing probabilities by increasing rheobase and reducing input resistance (Supplementary Fig. 6F–J). These ex vivo electrophysiological studies suggest that the activation of D2Rs and InsRs has a synergistic effect that substantially increases the excitability of D2R neurons in the CeA. Furthermore, this interaction may be critical for the regulation of compulsive-like eating behavior, supporting our GCaMP6s photometry analysis following quinpirole or insulin infusion.

Next, we examined the effect of selective optogenetic inhibition of CeA D2R-positive neurons expressing halorhodopsin in the CeA of Drd2-Cre mice by injecting AAV-DIO-eNpHR3.0-eYFP virus (Fig. 6A, B) and conducted the light/dark box test (Fig. 6C–H). Bilateral photoinhibition of CeA D2R neurons resulted in a significant and specific increase in palatable food consumption in the light compartment (Fig. 6G, H and Supplementary Video 1). We further tested whether InsR signaling contributes to the regulation of CeA D2R-mediated PF consumption by selectively activating CeA D2R neurons. To this end, we injected AAV-DIO-eYFP (eYFP) or AAV-DIO-ChR2-eYFP (ChR2) into the CeA of Drd2-Cre mice followed by CeA infusion of the InsR antagonist S961 (Supplementary Fig. 7, Supplementary Fig. 8A, B). Mice underwent the light/dark box test, and pre-test evaluations revealed no differences in basal body weight, food intake, or light/dark box preference between groups expressing eYFP (control) or ChR2 in CeA D2R neurons (Supplementary Fig. 8C–F). Following this, the mice were divided into two groups: one group was maintained on a NC diet, while the other was provided with PF for 14 days. Afterward, mice were reintroduced to the light/dark box for a 25-minute test, with PF placed in the light compartment. Fifteen minutes before testing, mice received CeA infusions of either saline or S961.

In the PF-fed group, optogenetic activation of CeA D2R neurons significantly suppressed PF consumption in ChR2-expressing mice. However, this suppression was abolished when S961 was infused into the CeA, demonstrating that InsR signaling is necessary for CeA D2R-mediated regulation of compulsive-like PF consumption (Supplementary Fig. 8G, H). These findings indicate that CeA D2R neurons, in conjunction with InsR signaling, are critical for modulating compulsive-like eating behavior specific to PF. In the NC group, however, optogenetic activation of CeA D2R neurons had no effect on NC consumption, even after six hours of food deprivation prior to testing. Furthermore, S961 infusion did not alter NC consumption in either eYFP control or ChR2-expressing mice (Supplementary Fig. 8G, H). Together, these data indicate that reduced CeA D2R-expressing neuronal activity is associated with increased PF consumption whereas activation of CeA D2R neurons suppresses compulsive-like eating in an InsR-dependent manner (Fig. 6I).

DA release during PF consumption and its modulation by CeA D2R knockdown

Next, we examined changes in DA release in the CeA in response to PF using the genetically encoded fluorescence DA sensor GRAB-DA2m [40]. We prepared two groups of Drd2-Cre mice: one receiving AAV- DIO-DSE-mCherry-PSE-shLacZ in the CeA as a control (shLacZ) and the other receiving AAV- DIO-DSE-mCherry-PSE-shD2R (shD2R) for selective D2R knockdown in CeA D2R neurons (Supplemental method). Selective expression of shD2R in D2R-expressing CeA neurons resulted in a ~ 77% reduction in D2R expression compared to the control group injected with shLacZ (Supplementary Fig. 9A–C). Both groups were injected with AAV-hSyn-GRAB_DA2m viruses bilaterally into the CeA and a fiber optic cannula was implanted unilaterally to enable real-time measurement of DA levels during PF-seeking behavior (Supplementary Fig. 9A, D). After one week of NC access, there was no significant difference in the GRAB signal between the shLacZ and shD2R mice (Supplementary fig. 9F, G). Subsequently, mice were randomly assigned to two groups: one with limited PF access (1 hr/day, PF limited) and the other with extended PF access (24 hr/day, PF extended) for two weeks (Supplementary Fig. 9D). In the PF-limited condition, shD2R mice consumed approximately 64% of their daily caloric intake during the 1-hour PF access period, significantly more than shLacZ mice, despite similar overall daily caloric intake between groups. This behavior indicates binge-like eating in shD2R mice with CeA D2R downregulation (Supplementary Fig. 9E). In the PF-extended condition, both groups displayed similar daily caloric intakes, derived almost exclusively from PF consumption (Supplementary Fig. 9E). In terms of body weight, PF-extended shD2R mice showed a slight, non-significant increase compared to shLacZ mice (Supplementary Fig. 9F).

After two weeks of PF exposure, DA release profiles during PF consumption were similar between shLacZ and shD2R mice in the PF-limited condition. However, in the PF-extended condition, shD2R mice exhibited a blunted DA signal in the CeA compared to shLacZ controls (Supplementary Fig. 9I–L), These findings indicate that CeA D2R deficiency leads to attenuated DA release under prolonged PF exposure, emphasizing the importance of CeA D2R in modulating reward-related DA signaling.