Brain, Behavior, and Immunity

Background Observational studies have reported an association between inflammation and postoperative complications but it is unclear whether these associations are causal. It is also unknown whether postoperative outcomes share a causal architecture with chronic, all-cause disease. Methods We performed bi-directional two-sample Mendelian randomization to investigate potential causal effects of 19 genetically-proxied inflammatory markers on postoperative acute kidney injury, atrial fibrillation (AF), delirium, myocardial infarction, stroke and surgical site infection, and their all-cause equivalents. Genetic instruments for inflammatory markers were sourced from nine GWAS of up to 204,402 European participants with outcome data derived from UK Biobank. Results The primary postoperative analysis showed a protective effect of down-regulated IL-6 signalling on stroke risk (OR (95% CI) 0.27 (0.11--0.69), p=0.006). However, in the all-cause analysis a causal effect on stroke was not present (OR (95% CI) 1.14 (0.75--1.24), p=0.78), whilst a robust protective effect was seen for down-regulated IL-6 with AF across all three instruments studied (all p<0.009). In postoperative and all-cause analyses, genome-wide variants for CRP showed a protective effect on delirium that was not present in cis-restricted analyses. Conclusions We found evidence supporting a potential causal role for IL-6 signalling in perioperative stroke. However, the divergence in IL-6 effects between postoperative and all-cause outcomes suggests that the inflammatory architecture of acute postoperative complications may differ from chronic disease states. Furthermore, our findings suggest previously reported associations between CRP and delirium likely represent horizontal pleiotropy rather than direct causation. Future work should interrogate local tissue responses and the immediate perioperative period.

BackgroundSickness behavior comprises a coordinated constellation of motivational, cognitive, and social alterations that emerge during systemic inflammation. Although reductions in locomotion, feeding, and social engagement have been extensively characterized, how inflammation affects ultrasonic vocal communication--an ethologically relevant index of social motivation in rodents--remains insufficiently understood. Here, we investigated how systemic immune activation alters male-female social communication in mice by jointly assessing ultrasonic vocalizations (USVs) and approach behavior. MethodsSexually experienced male mice received an intraperitoneal injection of lipopolysaccharide (LPS), and their interactions with a novel estrous female were evaluated 24 h later by quantifying USVs and approach behavior. ResultsLPS administration robustly suppressed both the total number of USVs and the duration of male approach behavior, indicating a pronounced reduction in social motivation. Beyond this quantitative suppression, LPS also induced qualitative changes in vocal output, including shifts in the proportional use of specific USV subtypes and alterations in acoustic features such as sound pressure. ConclusionsThese findings demonstrate that USVs capture multiple dimensions of inflammation-induced disruption of social communication, reflecting not only diminished motivation to engage socially but also changes in the structure of communicative signals themselves. By revealing that systemic immune activation reshapes both social approach behavior and vocal communication patterns, this study establishes USV analysis as a sensitive and translationally relevant behavioral readout for probing neuroimmune mechanisms underlying the social and communicative disturbances characteristic of sickness behavior. More broadly, our results highlight the utility of vocal communication analyses for elucidating how inflammatory processes perturb social circuits and communicative function in health and disease.

BackgroundExposure to prenatal maternal inflammation (PNMI) has been linked to neurodevelopmental alterations in human offspring. Preclinical studies suggest that PNMI disrupts reward circuitry, particularly within mesolimbic circuits. However, the effects of PNMI on mesolimbic circuits (i.e, ventral tegmental area (VTA) projections to the hippocampus (VTA-H) and limbic striatum (VTA-LS)) in humans are not yet known. MethodsData for PNMI biomarkers [interleukin (IL)-6, IL-8, IL-1 receptor antagonist (IL-1ra), soluble TNF receptor-II (sTNF-RII)] from first trimester (T1) and second trimester (T2) maternal sera, and offspring MRI brain scans in late midlife (aged 57-63 years), were available for 89 mother-offspring dyads. Probabilistic tractography delineated bilateral VTA-H and VTA-LS tracts. Macrostructural tract measures were examined using hierarchical linear regressions. Microstructural integrity was assessed using neurite orientation dispersion and density imaging, and permutation-based cluster analyses. ResultsHigher T2 IL-1ra was associated with increased macrostructure (left VTA-H tract), whereas higher T2 sTNF-RII was associated with reduced macrostructure (right VTA-H and VTA-LS tracts) and higher T2 IL-8 (bilateral VTA-LS tracts). Microstructurally, higher T2 IL-6 was associated with increased neurite density (distal cluster, right VTA-H tract), while higher T1 IL-8 was associated with reduced neurite density (near the hippocampus in the left VTA-H tract, near the VTA in bilateral VTA-LS tracts). ConclusionsPNMI was associated with altered mesolimbic reward circuitry in offspring. This suggests that prenatal inflammation may contribute to affective and motivational disorders in offspring via alterations in mesolimbic circuitry.

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic multisystem disease characterized by profound fatigue, post-exertional malaise, cognitive impairment, and autonomic dysfunction. Its pathophysiology is incompletely understood and likely involves complex interactions between immune, autonomic, and metabolic dysregulation. Despite features with potential relevance for anesthesia and perioperative care, evidence to guide anesthetic management in individuals with ME/CFS remains limited. We therefore performed a retrospective matched-pair analysis to generate clinical data on perioperative responses and identify areas for future research. Methods: We conducted a retrospective matched-pair analysis at a single tertiary center. All patients with ME/CFS undergoing general anesthesia from 2015 to 2026 were identified using ICD-10 codes (G93.3 and U09.9) with additional manual verification and matched 1:1 to controls for comparison. Patients with confounding diagnoses or American Society of Anesthesiologists physical status above III were excluded. The analysis focused on intraoperative hemodynamic parameters, including baseline, post-induction, median, and lowest recorded systolic blood pressure and heart rate, as well as early postoperative outcomes in the post-anesthesia care unit (PACU), including maximum pain scores and requirement for rescue analgesia. Results: Out of 189 individuals identified through ICD-10 codes, 15 matched pairs were included after application of exclusion criteria. ME/CFS patients exhibited lower lowest recorded intraoperative systolic blood pressure (90 [82.5-95.0] mmHg in ME/CFS vs 100 [90.0-110.0] mmHg in controls, p = 0.044) as well as lower lowest heart rate (50 [40.0-57.5] bpm in ME/CFS vs 60 [50.0-65.0] bpm in controls, p = 0.012). Vasopressor use and fluid administration did not differ, and no episodes of severe hypotension or perioperative adverse events were observed. Postoperative pain was higher in ME/CFS, with higher maximum pain scores (NRS 5.0 [4.0-6.0] in ME/CFS vs 1.0 [0.0-4.0] in controls, p = 0.008) and more frequent opioid rescue analgesia (80% in ME/CFS vs 33% in controls, p = 0.039). Postoperative nausea or vomiting, oxygen supplementation, and PACU length of stay were similar between groups. Conclusions: General anesthesia appears hemodynamically well tolerated in individuals with ME/CFS. In contrast, postoperative pain burden is increased and may require tailored analgesic strategies. Post-exertional malaise, a key disease feature with potentially delayed onset and significant impact, was not captured in this study and remains an important target for future research. These hypothesis-generating findings highlight the need for prospective studies to optimize perioperative management and evaluate patient-relevant outcomes in ME/CFS.

BackgroundLoneliness is a psychosocial stressor associated with elevated risk of severe mental illness (SMI), including major depressive disorder (MDD), schizophrenia (SCZ), and bipolar disorder (BD). Loneliness is theorized to become biologically embedded via inflammation-related mechanisms, yet its causal relationship with SMI and the role of inflammatory signaling remain unclear. AimsTo investigate whether loneliness causally influences SMI risk and whether inflammatory cytokines mediate this relationship. MethodWe applied univariable Mendelian randomization (MR) to estimate the causal effect of loneliness on SMI and multivariable MR (MVMR) to assess mediation by inflammatory signaling. We integrated genome-wide association study (GWAS) summary statistics for loneliness and SMI with genetic instruments for inflammatory cytokines. MVMR models estimated the direct effect of loneliness after accounting for inflammatory signaling using eQTL and pQTLs for interleukin-1 receptor antagonist (IL-1RA), interleukin-6 (IL-6), IL-6 receptor (IL-6R), tumor necrosis factor alpha (TNF-), and TNF receptors (TNF-R1/2). Bidirectional MR examined potential reverse causal pathways between inflammation, SMI, and loneliness. ResultsMR provided evidence consistent with a causal effect of loneliness on SCZ and MDD. Results were also consistent with inflammatory cytokine pathways for IL-1RA, IL-6R, and TNF-R1, partially mediating the loneliness-SCZ and loneliness-MDD causal effect. No significant effects were identified for BD in UVMR or MVMR models. Bidirectional MR suggested evidence of reverse causation between SCZ and loneliness. ConclusionsThe findings support a causal risk-increasing effect of loneliness on SCZ and MDD, partially mediated by systemic inflammatory signaling, implicating pathways as a plausible mechanistic link between psychosocial stress and mental illness risk and highlighting potential opportunities for prevention and targeted intervention through inflammation and social pathways.

Social isolation refers to an extreme form of social deprivation that has enduring effects on the brain and behavior. Adolescents show selective vulnerability to such heightened social stress, displaying aberrant behavior and psychiatric ailments. The post-weaning social isolation rodent model has been widely used to recapitulate such behavioral anomalies and delineate their mechanistic bases. Here, we aim to identify how prolonged social isolation during adolescence affects neuroimmune responses in both sexes and the implications for behavioral outcomes, particularly aggression. While males subjected to adolescent isolation were hyper-aggressive with pathological signs, females showed reduced social exploration and inactivity. Cytokine profiling in core brain regions implicated in aggression revealed reduced interleukin 6 (IL6) levels, specifically in the hypothalamus, in both sexes. Other proinflammatory cytokines, including interferon-gamma and interleukin-1beta, were unaltered. IL6-responsive genes, SOCS3 and TIMP1, were also downregulated in the hypothalamus of both socially isolated males and females. The hypothalamus is crucial for stress responsiveness and the expression of excessive aggression. Despite behavioral dimorphism, reduced IL6 levels in both sexes may indicate differences in downstream signaling and roles beyond classical immune responses. Our findings suggest that hypothalamic IL6 may be a key mediator of adolescent social isolation, which is associated with aberrant behavior, including aggression.

Background: Acute necrotizing encephalopathy (ANE) is a rare and severe neurologic complication of viral infection in children, thought to result from a hyperacute cytokine storm causing blood-brain barrier disruption and central nervous system injury. Despite characteristic clinical and radiologic features, ANE remains poorly understood at the molecular level, with no validated biomarkers or targeted therapies. We aimed to determine whether genetic predisposition to ANE due to RANBP2 variants is associated with a distinct immunologic signature. Methods: We conducted a prospective biological study of familial ANE (ANE1, NCT06731790). We included 23 heterozygous carriers of the RANBP2 c.1754C>T (p.Thr585Met) variant from 10 families, and 28 noncarriers (median age, 40 years [range, 4-72]). Soluble immune mediators, transcriptomic analyses, multiparameter flow cytometry, and cellular imaging were analysed in peripheral blood mononuclear cells (PBMCs) and monocytes. Baseline and resiquimod stimulated immune responses were analysed within the same statistical model, with genetic status as the primary predictor. Findings: The RANBP2 Thr585Met mutation was associated with a dysregulated inflammatory phenotype characterized by reduced basal mediator production and exaggerated TNF- responses following stimulation (estimated difference, +2,098 pg/mL; 95% CI, 1,121 to 3,076; P=0.0001). Transcriptomic and flow cytometry analyses showed broad reprogramming of myeloid cells with enrichment of CXCR3-high CD14-high subsets. Expansion of these populations was associated with increased long-term disease burden. The RANBP2 variant was the only independent factor associated this inflammatory phenotype. Interpretation: RANBP2-associated ANE is characterised by a distinct immunological signature that can inform disease stratification and support the development of targeted immunotherapeutic approaches.

T-cell activation may be contributing to severe psychiatric disorders. Soluble CD27 (sCD27) - a marker for T-cell activation and disease activity in several autoimmune diseases - was evaluated as a tool for distinguishing T-cell activity in selected patients with severe psychiatric disorders, multiple sclerosis (MS), and controls. We hypothesise that elevated sCD27 levels will be associated with comorbid autoimmune disease (AID). sCD27 was measured in cerebrospinal fluid (CSF) and blood from a population enriched for suspected immunological comorbidity: the Immunopsychiatry Cohort (IP; n=115) and patients with MS (n=37), where levels in both groups were higher when compared with age matched controls undergoing surgery (n=154). Positive sCD27 (sCD27+), was defined as values >97.5% of controls. In IP, 23% were CSF sCD27+ and 15% blood sCD27+, compared to patients with MS where 88% were CSF sCD27+ and 22% were blood sCD27+. CSF-sCD27+ was confirmed as a sensitive marker for MS. In IP, CSF-sCD27+ was associated with comorbid AID (X2=4.847, p =0.028;) and AID disease activity (OR=5.14, p=0.029). Associations with AID were stronger when CSF and/or blood sCD27+ were combined (X2=8.559, p=0.003). CSF-sCD27+ in IP was also associated with pleocytosis, CSF-Total-tau, and CSF-NfL. In patients with severe psychiatric disorders, the sCD27+ cases were more likely to have comorbid AID and established markers for neuroinflammation in CSF. Combining analyses of CSF and blood improved sensitivity and specificity for AID suggesting compartmentalized T-cell activation. Psychiatric symptoms may precede somatic symptoms - or be the prominent symptom - of AID and sCD27 is a candidate marker for identification of this subgroup.

Although congenital Zika virus (ZIKV) syndrome is well-characterized, the neurodevelopmental consequences of postnatal infection are less understood. Here we used a rhesus macaque model to investigate the developmental consequences of ZIKV infection during infancy on the brain and behavior, building on our prior research. Male and female infant rhesus macaques infected with ZIKV at 1 month of age were compared to sex-, age-, and rearing-matched uninfected controls and infants treated with the TLR3 agonist PolyIC as a control for activation of the innate immune system. Longitudinal behavioral assessments revealed alterations in emotional regulation following ZIKV exposure, including poor state control scores obtained from the Infant Neurobehavioral Assessment Scale early after ZIKV infection and longer-term displays of increased hostility during an acute stressor. While attachment bonds to caregivers were preserved, ZIKV-infected infants showed sex-specific alterations in behavioral regulation during caregiver separation compared to controls. At 3 months of age, MRI scans revealed larger total cerebrospinal fluid (CSF) volume and reduced volumes in visual processing regions in ZIKV-infected infants compared to controls. Postnatal ZIKV exposure also resulted in sex-specific brain structural alterations with males exhibiting amygdala hypertrophy, whereas ZIKV-infected females had volumetric reductions in temporal-limbic and temporal-auditory cortices. These findings demonstrate that postnatal ZIKV infection disrupts the development of sensory, social and emotion-regulatory systems and CSF function, highlighting the critical need for long-term monitoring of exposed children. One-Sentence SummaryPostnatal Zika virus infection disrupts emotional regulation and alters brain development in infant rhesus macaques, revealing a critical window of neurodevelopmental vulnerability that extends beyond the fetal period.

ImportanceEmerging data show that B-cell depleting chemotherapies, which are increasingly used to treat autoimmune disorders and multiple sclerosis, can be associated with mucosal side effects such as inflammatory vaginitis. ObjectiveEvaluate the impact of rituximab treatment on vaginal mucosal immune markers, endocervical immune cell populations and vaginal microbiome. DesignCross-sectional observational study conducted between 2022 - 2024. SettingAcademic medical center, Boston Massachusetts. ParticipantsWe enrolled women aged >18 years who were either 1) receiving rituximab for autoimmune renal disease or were 2) healthy controls ExposureTreatment with rituximab, an anti CD20 monoclonal antibody. Main outcome and measureWe compared endocervical immune cell populations, vaginal fluid immune markers, vaginal fluid immunoglobulins and vaginal microbiome composition between individuals being treated with rituximab and healthy controls. ResultsWe enrolled 26 women treated with rituximab for autoimmune renal disease and 26 healthy controls. Median circulating and endocervical B-cell and plasma cell proportions were significantly lower in treated participants compared to controls. Median vaginal fluid IgA concentrations were significantly lower in participants treated with rituximab, while ILE, IgM, IgG1, IgG2, IgG3 and IgG4 were not different between groups. Total T cell frequencies were similar between groups, but the proportion of activated T cells (CD4+CD38+HLADR+) was significantly lower in people treated with rituximab. Concentrations of IL10, IL13, IL17, IL21, IL23, IL4, ITAC and TNFa were elevated in vaginal fluid from the rituximab group, while IL-8 was lower. A CST-IV-C, low-Lactobacillus pattern of vaginal microbiota was more common in the rituximab group. Conclusions and RelevanceSystemic B-cell depletion is associated with reduced vaginal fluid IgA, a more diverse microbiome composition, and increases in many vaginal fluid immune markers compared to healthy controls. The reduction in vaginal fluid IgA may provide opportunities for vaginal bacteria to induce inflammation. Key pointsO_ST_ABSQuestionC_ST_ABSHow does circulating B-cell depletion impact the vaginal microenvironment? FindingsIn this cross-sectional study of 52 women, B cell and plasma cell proportions were significantly lower in both blood and vaginal mucosa among rituximab-treated participants compared to healthy controls. Vaginal IgA concentrations, but not other immunoglobulins, were significantly lower in rituximab treated participants. In treated participants, vaginal cytokine concentrations were elevated, and microbiome composition shifted toward non-Lactobacillus-dominant communities. In six people with inflammatory vaginitis, both circulating and endocervical B cells were lowest in people with the most severe symptoms. MeaningSystemic B cell depletion is associated with alterations in vaginal mucosal immune markers and microbiome composition which increase local inflammation.

Cognitive impairment is a disabling feature of Long COVID, with data supporting neuroinflammation and maladaptive glial responses as primary drivers. Nasal administration of an anti-CD3 monoclonal antibody (aCD3 mAb) has shown therapeutic benefits in autoimmune and CNS disease models. Using a respiratory-restricted mild SARS-CoV-2 mouse model of Long COVID, we show that nasal anti-CD3 mAb, administered shortly after infection or during chronic neuroinflammation, increased brain FoxP3+ IL-10+ Tregs, reduced microglial and astrocytic gliosis in the white matter and hippocampus, restored neurogenesis, and improved short-term memory. Nasal aCD3 mAb reprogrammed microglia from an antigen-presenting, NF-{kappa}B-driven inflammatory state toward chemokine signaling, phagosome, and TGF {beta}-related regulatory phenotype. Patients with Long COVID with neurological symptoms had lower circulating Treg populations. These findings identify nasal administration of aCD3 mAb as a noninvasive strategy to control neuroinflammation, restore the neurogenic niche, and offer a novel approach to treating cognitive impairment in Long COVID.

Background: Adolescence is a critical period of neurodevelopment with the emergence of chronic medical conditions and increasing exposure to long-term medications. P-tau217 is a sensitive blood-based biomarker of neuropathology in older adults, yet its developmental behavior and susceptibility to common clinical factors in youth are unclear. Here we tested whether p-tau217 varies with age, comorbidity, or medication use during adolescence; and whether collection method (venous vs Tasso+ capillary) yields comparable concentrations. Methods: In an adolescent cohort, plasma p-tau217 was measured by Simoa-X. Paired venous and Tasso+ capillary samples were also analyzed from adult volunteers for methodological comparison Results: In adolescents (n=41; mean age 16{+/-}2.6 years), p-tau217 did not correlate with age or BMI z-score and did not differ by psychiatric, cardiometabolic, or gastrointestinal comorbidity, nor by corresponding medication use. In contrast, p-tau217 concentrations were >10-fold higher in Tasso+ capillary plasma than venous plasma, a discordance replicated in paired adult samples. Conclusion: Plasma p-tau217 appears physiologically stable across common clinical variables in adolescence, but highly sensitive to biospecimen collection method. Venous and Tasso+ capillary plasma should not be directly compared or pooled until methodological differences are resolved. These data provide a developmental baseline and critical methodological caution for pediatric neuroscience and decentralized biomarker studies.

Introduction: Eating behaviors are consistently associated with weight-related traits, yet the biological factors contributing to individual differences in these behaviors remain poorly characterized. Plasma proteomics offers an opportunity to investigate the biological processes underlying eating behaviors. Methods: Participants were 730 young adult twins from the FinnTwin12 cohort. Eating behaviors were measured through self-report questionnaires, including the Three-Factor Eating Questionnaire-R18 and four additional items on eating styles. Associations between plasma proteins and eating behaviors were examined using generalized estimating equation models adjusted for age and sex, with additional analyses adjusting for body mass index (BMI). Within-pair analyses were conducted in both monozygotic (MZ) and dizygotic twin pairs to assess whether associations were influenced by genetic or environmental factors. Results: We identified 51 significant protein-eating behavior associations involving 35 unique proteins (FDR <0.05). We observed 19 associations for the item "overeating when feeling down" and 12 for the TFEQ factor of emotional eating. The identified proteins were predominantly enriched in immune system pathways, including the complement cascade and adaptive immune signaling. After further adjustment for BMI, 12 associations persisted, most of which were associated with eating-style items, suggesting that BMI had a substantial influence on protein-eating behavior associations. Within-pair analyses of MZ pairs indicated that several associations persist after accounting for genetic effects. Conclusion: Our study identifies plasma proteins associated with eating behaviors, largely involving immune-related pathways. While some associations attenuated in twin analyses, several persisted, suggesting environmental influences. These results highlight potential biomarker candidates and indicate that modifiable environmental factors may contribute to the proteomic profiles associated with eating behaviors, with possible implications for weight-related traits.

Background Chronic pain and depression are prevalent and burdensome conditions that frequently co-occur. Separate neuroimaging studies of each disorder suggest overlapping brain-structure alterations, however, relatively few studies have examined their comorbidity directly, and the neuroanatomical profile of co-occurring chronic pain and depression remains unclear. Methods Using UK Biobank data (n = 71,214), we conducted cross-sectional pairwise association analyses of brain structure (cortical measures, subcortical volumes, and white matter microstructure) comparing participants with current comorbid chronic pain and depression, current chronic pain only, current depression only, and controls. Results Compared with controls, the comorbidity group showed regional differences in cortical surface area and thickness ({beta} range = -0.096 to 0.098, pFDR < 0.05), widespread lower cortical volume ({beta} range = -0.096 to -0.050, pFDR < 0.05), lower thalamic (left: {beta} = -0.048, pFDR = 0.038; right: {beta} = -0.060, pFDR = 0.007), hippocampal (left: {beta} = -0.062, pFDR = 0.035; right: {beta} = -0.088, pFDR = 0.002) and left accumbens volume ({beta} = -0.073, pFDR = 0.011), and evidence of widespread white matter microstructure alterations (fractional anisotropy: {beta} range = -0.116 to -0.080, pFDR < 0.05; mean diffusivity: {beta} range = 0.063 to 0.137, pFDR < 0.05). Pairwise comparisons with the disorder-specific groups also identified several alterations unique to the comorbidity group. Compared to controls, those with chronic pain only had widespread lower cortical surface area and volume ({beta} range = -0.043 to -0.015, pFDR < 0.05), whereas non-comorbid depression showed more regionally specific lower cortical thickness and volume ({beta} range = -0.140 to -0.062, pFDR < 0.05) and lower thalamic volume (left: {beta} = -0.067, pFDR = 0.016; right: {beta} = -0.066, pFDR = 0.015), alongside widespread white matter microstructure deficits (fractional anisotropy: {beta} range = -0.104 to -0.083, pFDR < 0.05; mean diffusivity: {beta} range = 0.079 to 0.149, pFDR < 0.05). Conclusion These results provide a robust characterisation of brain structure alterations in comorbid chronic pain and depression, highlighting a distinct neuroanatomical profile and advancing understanding of its underlying neurobiology.

Background Chronic pain and depression are common disorders and leading causes of disability worldwide. They frequently co-occur and show substantial genetic correlation, indicating a shared genetic basis. However, the locus-specific architecture of this overlap remains poorly characterised and may yield important insights into the pathophysiology of their comorbidity. Methods Using the largest currently available European-ancestry genome-wide association studies of major depressive disorder (MDD) (n = 1,639,572) and multisite chronic pain (MCP) (n = 387,649), we estimated the polygenic overlap between traits using the bivariate causal mixture model (MiXeR), identified shared loci via conjunctional false discovery rate (conjFDR), and tested colocalisation with each trait and genetically regulated gene expression in 13 brain tissues. Results MiXeR analysis demonstrated a high degree of directionally consistent polygenic overlap between MDD and MCP. Subsequent conjFDR analysis identified 375 shared loci, 22 of which showed cross-trait colocalisation between the MDD and MCP signals. Gene mapping and enrichment of shared loci implicated several biological processes, including cadherin-mediated cell-cell adhesion and translational initiation. Gene expression colocalisation in brain tissue highlighted protein phosphatase 6 catalytic subunit (PPP6C) and suppressor of cancer cell invasion (SCAI) in both disorders. Conclusion Overall, these findings have enhanced our understanding of the complex relationship between chronic pain and depression by identifying shared molecular mechanisms that warrant further study as targets for prevention and treatment.

Early life stress (ELS) events during sensitive postnatal time periods can recalibrate future stress responsiveness and precipitate mental disorders. Neurovascular adaptations can influence cognition, mood, and stress responses. Disruption of blood-brain barrier (BBB) integrity, which is formed by endothelial cells, astrocytes, and pericytes, has been implicated in affective disorders such as depression, which often arise from chronic stress experiences. Despite the BBB undergoing critical maturation stages during development, it remains poorly known how ELS influences brain vascular function, as previously shown for adult stress, and whether it augments BBB vulnerability to subsequent challenges. First, we took advantage of a public two-hit stress RNA-sequencing dataset and filtered for vascular enriched genes in the prefrontal cortex and nucleus accumbens, the two brain regions where BBB integrity is frequently compromised. This analysis revealed BBB-related gene ontology categories modulated by either ELS alone or its combination with adult stress. Then, using a mouse model combining ELS with chronic social defeat stress (CSDS) in adulthood, we found that ELS did not exacerbate CSDS susceptibility; instead, it increased social interactions and the likelihood of a resilient profile in both males and females. Transcriptomic profiling in our cohort further identified distinct sex- and region-specific BBB gene expression patterns associated with ELS and its interaction with CSDS. Additionally, we observed a reduction of corticosterone levels, the primary stress hormone, following CSDS. Altogether, these results indicate that ELS modulates stress responses when facing emotional challenges in adulthood, possibly through long-lasting changes of BBB function via the glucocorticoid system. HighlightsO_LIRNA-seq vascular filtering reveals BBB distinct ontology categories for ELS and AS C_LIO_LIELS increases the likelihood of a high social and resilient profile. C_LIO_LIPericytes gene expression associated to resilience is sex- and region-specific. C_LIO_LICORT response desensitizes after adult CSDS in both sexes. C_LI

Structured AbstractO_ST_ABSINTRODUCTIONC_ST_ABSAdults with Down syndrome (DS) have a higher risk of developing Alzheimers disease (AD). As gut microbiota (GM) alterations have been reported in AD, we investigated their association with cognitive decline and plasma AD biomarkers in DS. METHODSFecal and plasma samples were collected from 58 adults with DS (21-75 years) and 30 euploid controls (CTRL; 25-83 years). GM was profiled using 16S rRNA sequencing. Major Neurocognitive Disorder (NcD) was diagnosed according to DSM-5 criteria. Plasma levels of p-Tau181, NfL, and GFAP were measured using the Simoa platform. RESULTSCompared with CTRL, DS showed significant changes in UBA1819 and Intestinibacter genera, previously reported to be associated with mild cognitive impairment. Furthermore, DS with NcD were characterized by a reduced abundance of Roseburia genus, which was also negatively associated with plasma levels of AD biomarkers. CONCLUSIONAdults with DS display AD-associated changes in GM partially resembling those previously reported in euploid AD patients

Chronic short sleep (CSS) is an emerging public health issue that frequently begins in adolescence and is common among healthcare professionals and others engaged in shift work. Epidemiological studies associate CSS and sleep disruption with metabolic disorders, cardiovascular disease, cognitive decline, and heightened Alzheimers disease risk. Building on our prior findings that sleep deprivation perturbs proteostasis and activates endoplasmic reticulum (ER) stress pathways, we investigated the long-term consequences of CSS in young adult wild-type mice over the course of one year. Mice exposed to CSS displayed impaired cognition in hippocampal dependent tasks by 28 weeks of age, indicating emerging memory deficits. At the molecular level, CSS disrupted hippocampal proteostasis--particularly protein folding processes--and triggered ER stress and activation of the unfolded protein response (UPR). Importantly, disrupted proteostasis preceded the behavioral decline, with diminution of the key chaperone and UPR regulator BiP occurring at 20-22 weeks of age. CSS also increased markers of cellular stress and neuroinflammation while reducing the expression of proteins associated with memory function. Age also seemed to be a cellular stressor, causing a longitudinal increase in UPR, ISR, and neuroinflammation markers. Together, these results indicate that both chronic short sleep and age compromise proteostasis and promote neuroinflammation, contributing to progressive cognitive dysfunction.

Background Chronic pain and depression are leading causes of disability and frequently co-occur. Depression presents with diverse symptoms, but despite this variability, the prevalence of individual depressive symptoms in chronic pain and the genetic and causal associations linking these traits remain poorly characterised. Methods Using data from 142,688 age- and sex-matched UK Biobank participants, we compared depressive symptom severity levels and item-level Patient Health Questionnaire-9 (PHQ-9) prevalences, spanning affective, cognitive and somatic domains, between participants with and without chronic pain. Using genome-wide association study (GWAS) summary statistics of multisite chronic pain (MCP), major depressive disorder (MDD), and individual symptoms of depression, genetic correlations and bidirectional causal effects between MCP and depressive phenotypes (MDD and individual symptoms) were estimated via linkage disequilibrium score regression (LDSC) and two-sample Mendelian randomisation (MR), respectively. Results Depression (at every severity level) was more common in the chronic pain group compared to controls, with the largest between-group difference for severe symptoms (7.50-fold increase). All individual depressive symptoms were at least 2.79 times as prevalent in chronic pain. Additionally, chronic pain had a significant and positive genetic correlation with MDD (rg = 0.59) and all depressive symptoms (rg = [0.24, 0.55]). MR supported a bidirectional causal association between MCP and MDD (MCP[-&gt;]MDD: OR = 1.85, pFDR < 0.001, MDD[-&gt;]MCP: {beta} = 0.17, pFDR < 0.001). At the symptom level, MR indicated bidirectional effects between MCP and anhedonia (MCP[-&gt;]anhedonia: OR = 1.60, pFDR < 0.001, anhedonia[-&gt;]MCP: {beta} = 0.08, pFDR = 0.005), and unidirectional effects of MCP on appetite/weight gain (OR = 1.90, pFDR = 0.022) and appetite/weight loss (OR = 1.63, pFDR = 0.005), concentration problems (OR = 1.63, pFDR = 0.044), and suicidal thoughts (OR = 1.46, pFDR = 0.021). Additionally, genetic liability to concentration problems was associated with a lower risk of MCP ({beta} = -0.04, pFDR = 0.022). Conclusion Chronic pain is associated with a marked depressive burden spanning all symptom domains. Shared genetic architecture and symptom-specific causal pathways, particularly involving anhedonia, highlight potential targets for improved treatment of comorbid chronic pain and depression.

ObjectiveStudies of nutritional status and host responses during severe and critical illness have focused predominantly on obesity; in contrast, the relationship between undernutrition, host responses, and clinical outcomes in adults hospitalized with severe infection remains poorly defined. We sought to determine whether severe undernutrition is associated with distinct host responses and clinical outcomes in adults hospitalized with severe infection. DesignProspective cohort study. SettingTwo public referral hospitals in Uganda. PatientsNon-pregnant adults ([&ge;]18 yr) hospitalized with severe, undifferentiated infection. InterventionsNone. Measurements and Main ResultsWe analyzed clinical data and serum Olink proteomic data from 432 participants (median age, 45 yr [IQR, 31-57 yr]; 44% male). Overall, 213 participants (49%) met prespecified criteria for undernutrition, including 52 (12%) with severe undernutrition. Clinically, severe undernutrition was associated with HIV coinfection, microbiologically diagnosed tuberculosis, greater physiological instability, and higher mortality. After adjustment for age, sex, illness duration, study site, and HIV, malaria, and tuberculosis coinfection, severe undernutrition was associated with higher expression of proteins involved in pro-inflammatory immune signaling, endothelial and vascular remodeling, hypoxia and oxidative stress responses, and extracellular matrix remodeling, together with lower expression of proteins linked to growth signaling, anticoagulant regulation, and lipid homeostasis. ConclusionsSevere undernutrition is associated with a distinct high-risk clinical phenotype and biologic signature in adults hospitalized with severe infection. These findings suggest that undernutrition may potentiate key domains of sepsis pathobiology, with implications for strengthening nutritional support and informing host-directed treatment strategies in low- and middle-income countries where malnutrition is common. Key PointsO_ST_ABSQuestionC_ST_ABSHow does undernutrition influence immune, metabolic, and endothelial responses to severe infection in adults? FindingsIn this multicenter cohort study of 432 adults hospitalized with severe infection in Uganda, severe undernutrition was associated with greater physiologic instability, higher mortality, and a distinct proteomic host-response profile. Adults with severe undernutrition exhibited a proteomic signature characterized by pro-inflammatory immune signaling, endothelial and extracellular matrix remodeling, and hypoxia and oxidative stress responses, together with lower expression of proteins involved in growth signaling, anticoagulant regulation, and lipid homeostasis. MeaningSevere undernutrition is associated with a distinct high-risk clinical and biologic phenotype during severe infection, with implications for nutritional support, risk stratification, and host-directed therapeutic strategies, particularly in low- and middle-income countries.