Brain, Behavior, & Immunity - Health

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.

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.

Post-traumatic stress disorder (PTSD) has been linked to various alterations within the immune system, yet the metabolic programming of immune cells remains unexplored. In the current cross-sectional study, we interrogated immunometabolic function by applying cell-specific metabolic flow cytometry, serum biomarker profiling, and targeted gene expression analysis in peripheral blood mononuclear cells from patients with PTSD (N=34) compared with healthy controls (N=32). PTSD was associated with higher glycolysis- and oxidative pentose phosphate pathway-related markers across adaptive and innate immune cell subsets, as well as elevated circulating interleukin-6. Expression of inflammatory- and stress-related genes was largely comparable between groups. Together, these data provide preliminary evidence for immunometabolic alterations in PTSD at both cellular and systemic levels. These results could contribute to understanding potential pathophysiological mechanisms and support further investigation of immunometabolism in PTSD.

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.

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 ([≥]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.

Exercise is a positive health behaviour associated with improved mood. However, the mechanisms underlying the benefits of exercise on affective health are unclear, particularly with respect to type of exercise and sex. Chronic exercise decreases neuroinflammation, which is linked to improvements in mood and anxiety. However, exercise is also a physiological stressor that can transiently upregulate systemic inflammation, and its effects on neuroinflammation are not well understood. This study examined how acute and chronic exercise affect circulating and brain cytokine levels and anxiety-related behaviour in young healthy male and female mice. In Experiment 1, mice were placed on a treadmill for a two-hour bout of moderate exercise. Two hours after exercise, animals were either tested in the open field or euthanized for measurement of cytokines (IL-1{beta}, TNF, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p70, IFN-{gamma}, KC/GRO). In Experiment 2, mice underwent an 8-week moderate treadmill exercise paradigm followed by open field testing and tissue collection. Acute exercise decreased time spent in the centre of the open field in males only, suggesting increased anxiety-like behaviour in males. Acute exercise increased IL-6 and decreased TNF in serum, and increased amygdala principal component 1 (loading IL-12p70, IL-10, IFN-{gamma}, and TNF) in both sexes. Chronic exercise increased open field centre entries, increased IL-6 in the prefrontal cortex, decreased TNF in the dorsal hippocampus, and had minimal effects on circulating cytokines in both sexes. These results demonstrate that the effects of exercise on anxiety-related behaviour and cytokine levels depend on recurrence, tissue, and brain region. New & NoteworthyOur work highlights the contrast between anxiogenic and anxiolytic effects of acute versus chronic exercise, respectively, in healthy mice. Acute and chronic exercise differentially affected circulating and brain cytokines, providing insight into physiological adaptations to exercise. Both sexes demonstrated similar cytokine responses to exercise. These similarities are novel with respect to exercise research and noteworthy given sex differences in anxiety with respect to acute exercise.

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.

Microglial activation is a common feature of neurological and inflammatory diseases and may contribute to some associated symptoms. However, methodological limitations have made it challenging to identify the specific symptoms and behavioral consequences of selective microglial activation. In this study, we examined the spectrum of symptoms elicited by acute chemogenetic activation of microglia in mice and compared them to those induced by endotoxin-driven systemic inflammation. Both interventions upregulated inflammatory gene expression in the brain, reduced voluntary wheel running, and decreased self-care. Systemic inflammation additionally caused anorexia, weight loss, reduced motivation to work for palatable food, and impaired motor performance in the rotarod test--effects not observed with chemogenetic microglial activation. By showing that acute microglial activation reproduces certain motivational aspects of the sickness response while sparing other functions, the findings might shed new light on the contribution of microglia to symptoms and behavioral alterations during disease.

INTRODUCTIONThe pathophysiology and risk factors for Alzheimers disease (AD) and dementia are insufficiently known. We studied the connections between gut microbiome, overall dementia and AD in a prospective, population-based cohort. METHODSWe followed a population based random sample of 4,055 individuals (FINRISK 2022) for 16 years, with 330 cases of incident dementia and 280 AD cases. Gut microbiome community diversity and composition were assessed against future dementia and AD risk. Competing mortality risks were accounted for using Fine-Gray models. RESULTSCommunity diversity was not associated with dementia or AD. However, a supervised ordination with dbRDA suggested a possible compositional link between gut microbiome and dementia. One putative bacterial genus, Dorea, was associated with a decreased dementia risk. APOE {varepsilon}4 genotype associated with several taxa; of these, phylum Verrucomicrobiota and species Nocardia carnea were associated with incident dementia. DISCUSSIONThe gut-brain axis has a modest association on future dementia or AD risk. Microbial composition, rather diversities, may contribute to dementia risk.

Aging is associated with chronic low-grade inflammation, which is thought to contribute to both cognitive decline and various neurodegenerative diseases. Cannabinoids are reported to reduce levels of inflammatory markers; however, these effects have not been thoroughly assessed in aged subjects. To address this gap, we evaluated effects of chronic cannabis smoke exposure on peripheral and brain inflammatory markers in young and aged mice. Young adult (4 months old) and aged (22 months old) C57Bl/6J mice were exposed to smoke from burning either cannabis (5.5 - 6.2% THC) or placebo (0% THC) cigarettes daily for 30 consecutive days. Following exposure sessions, both blood and brain tissue from the prefrontal cortex (PFC) and hippocampus (HPC) were collected and analyzed for multiple markers of inflammation. Overall, the patterns of inflammatory markers varied across the three tissue types. Both comparisons of individual cytokines and global cytokine profiles revealed that aging caused modest increases in cytokine levels in serum and PFC, with little influence of cannabis exposure. In contrast, HPC samples had stronger age effects, with numerous cytokines elevated in aged mice compared to young. Cannabis also interacted with age in the HPC such that smoke exposure tended to increase cytokine levels in young mice but decrease them in aged mice. These findings point to general age-related increases in brain inflammatory markers in this mouse strain, but cannabis effects were largely restricted to the HPC, where smoke exposure produced age-dependent changes in cytokine profiles. HIGHLIGHTSO_LIAged C57BL/6 mice have elevated cytokines levels, especially in the hippocampus C_LIO_LICannabis smoke exposure produces age-dependent changes in cytokine levels in hippocampus C_LIO_LIIn HPC, cannabis smoke exposure attenuated age-related increases in IL-13 and Dkk1 C_LI

IntroductionNeurodegenerative dementia syndromes are severely debilitating, progressive and increasing in incidence with an ageing population. A treatable differential diagnosis to neurodegenerative dementia is autoimmune encephalitis (AE), but AE patients are often misdiagnosed, delaying treatment. Previous work in the Netherlands has shown that 0.8% of patients with suspected neurodegenerative dementia suffer from AE. In Sweden, there is considerable variability in the prevalence of AE, possibly indicating under-diagnosis. We hypothesized that some Swedish individuals seeking care for memory impairment might suffer from an undetected AE and that these would show aberrances in available markers of neuroinflammation. MethodsWe retrospectively screened frozen sera from 1041 individuals seen between 2019 and 2023 at the Karolinska University hospital memory clinics in Stockholm for autoantibodies to contactin-associated protein-like 2 (CASPR2), leucine-rich glioma-inactivated 1 (LGI1), gamma-aminobutyric acid receptor B (GABABR), the n-methyl-d-aspartate receptor (NMDA-R) and Immunoglobulin superfamily containing LAMP, OBCAM, and Neurotrimin family member 5 (IgLON5) using live cell-based assays (CBAs) and scored them by microscopy. Serum and CSF from suspected positive patient samples were re-tested and titrated by live CBA, commercial fixed CBAs and tissue based assays. Results8 of the 1021 individuals, or 0.8% of the cohort, tested positive in at least three different tests for antibodies to CASPR2 (n=3), GABABR (n=2), LGI1 (n=1) and NMDAR (n=2). Seven of these patients had not been previously diagnosed with AE. Apart from two CASPR2-antibody positive patients showing neuropathic pain and seizures and neuromyotonia, respectively, the patients lacked clinical signs of encephalitis aside from memory impairment and affect lability. The antibody-positive patients did not differ significantly from autoantibody-negative patients in any available clinical parameter. None showed signs of inflammation on brain magnetic resonance tomography, and 2/7 lacked any sign of neuroinflammation in the CSF with available tests, which is commonly seen in later-onset AE. ConclusionOur work identifies undiagnosed AE patients with subtle symptomatology among Swedish memory clinic visitors, that cannot be sensitively separated from antibody-negative patients with current diagnostic tests. Our results suggest the need for the introduction of more sensitive markers of neuroinflammation to the memory clinic to identify and treat individuals with AE among sufferers of memory impairment.

BackgroundAdverse life events and psychosocial stressors contribute to a range of neuropsychiatric disorders. However, the role of inflammatory dynamics around stress exposure remains unclear. Using TriNetX, a large international electronic health records database, we examined how systemic inflammatory activity and its temporal dynamics relate to subsequent risk of mental illness and somatic symptoms. MethodsWe compared 36,772 individuals with records of adverse life events and leukocytosis in the surrounding period with matched individuals with normal leukocyte counts, and performed an analogous comparison for socioeconomic and psychosocial stressors in cohorts of 87,936 individuals with leukocytosis and matched controls. To contrast dynamic with static inflammatory responses, we compared cohorts exhibiting leukocyte count changes with those maintaining persistently normal or persistently elevated leukocyte counts around stressor exposure. Outcomes, including new mental health and somatic symptom presentations, were evaluated within two years of the stressor. ResultsFollowing acute stressors, leukocytosis (compared with normal leukocyte counts) was associated with lower rates of subsequent anxiety disorders, cognitive symptoms and several somatic symptom diagnoses, with similar reductions in anxiety observed after chronic stressors. A dynamic inflammatory response was associated with the most favourable outcomes, with lower rates of anxiety, depression, functional neurological disorder, cognitive and sleep difficulties, fatigue, and multiple pain-related and other somatic symptoms than persistently low or high inflammation. ConclusionOur findings suggest that a well-regulated inflammatory response to stressors is associated with a reduced risk of diverse mental health and somatic outcomes, and that a transient immune activation may support recovery rather than confer risk.

Anorexia nervosa is characterized by maladaptive eating behavior and cognitive dysfunction, which could be explained by a neuroinflammation. A gut dysbiosis could link gastrointestinal alterations to central dysfunctions, particularly via the toll-like receptor 4 (TLR4), which has been shown to play a key role in the activity-based anorexia (ABA) model. We aimed to evaluate the neuroinflammation and its behavioral consequences in the ABA model, and to decipher the role of the microbiota-gut-brain axis, and more specifically of TLR4, in these alterations of the central nervous system. We show that chronic restriction is more strongly associated with gut inflammation, cecal microbiota alteration and neuroinflammatory processes in the hippocampus than acute restriction. The hippocampal glial response is characterized by a loss of astrocyte density, and an increased number of deramified microglia. We further demonstrate that these alterations are independent of TLR4 expressed by intestinal epithelial cells. In conclusion, our results highlight that the chronicity of ABA-associated undernutrition alters the response of glial cells in the hippocampus that is linked with changes in microbiota composition, highlighting the importance of faster diagnosis and treatment of AN.

BackgroundTraumatic brain injury (TBI) together with non-cerebral injuries characterizes the TBI-polytrauma (P-TBI) constellation, which is associated with acute neurological deterioration, delirium and unfavourable prognosis. It is hypothesized that systemic inflammatory mediators my enhances the focal, cerebral neuroimmune reaction with overall detrimental consequences, in particular in terms of acute microglial reactivity. MethodsWe explored the role of the Complement factor 3 (C3) and of the TLR-co receptor cluster of differentiation (CD14) in a murine polytrauma model that involves a mild TBI together with femur fracture, blunt thorax trauma and resuscitated haemorrhagic shock, making use of mice genetically lacking either C3, CD14 or both. ResultsWe show that P-TBI results in a rapid (4h) and brain-wide induction of inflammatory cytokines, although with distinct profiles (TNF and CCL2 having brain-wide involvement and IL-1{beta} restricted to ipsilateral cortex and striatum). TNF and CCL2 mRNA as well as protein synthesis were upregulated in microglia upon P-TBI in cortex, hippocampus and striatum which was fully abolished in the C3-/-CD14-/-animals. The analysis of single-KO animals revealed that induction of TNF and CCL2 was prevented in animals lacking C3, but not CD14, in the contralateral cortex and striatum, with an abolishment in hippocampus in mice lacking both C3 and CD14. In the cortical area of focal lesion neither C3 nor CD14 affected the induction of pro-inflammatory cytokines. ConclusionThus, C3 and CD14 are dispensable for the acute cytokine response to P-TBI in the site of injury but play differential roles across the cortex, hippocampus and striatum for the induction of cytokines in the non-injured parenchyma and in particular in microglia. Thus, interventions on C3 (mainly) and/or CD14 may reduce the encephalopathy risk associated with P-TBI but not the acute response in the injury site, where additional DAMP signalling may offer redundant activation pathways.

Social stress is a risk factor for psychiatric disorders and also influences immune function. While it is known that acute social stress impacts the number of immune cells in circulation, the temporal dynamics of stress induced immune-related transcriptional changes in human blood remain unclear. To investigate changes in gene expression, we exposed 26 adults to the Trier Social Stress Test (TSST), and collected blood at baseline, as well as 5, 30, 60 and 90 min after stress. Whole-blood gene expression was profiled using a 5 targeted RNA-sequencing method (STRT). Differential expression was analyzed using linear and cubic models. We observed a total of 54 differentially expressed genes following stress. Fast responses, with a transient peak immediately following stress, were enriched for cytotoxic T cell, NK cell and dendritic cell functions (e.g., GZMB, GNLY, CCL4 and GZMA) and paralleled lymphocyte count changes. In contrast, gradual, linear responses without any evident peak were enriched for neutrophil related genes (e.g., FPR2, PLAUR, CXCR2, AQP9, and QPCT) and did not mirror neutrophil counts, indicating cell intrinsic transcriptional changes. From pathway and transcription factor enrichment analyses, IL-12 family mediated signaling is inferred as a central mechanism linking stress to immune gene regulation. Our results show that acute psychosocial stress induces both fast and slower changes in gene expression in different immune cell populations. The involvement of the IL-12-STAT4 axis and genes such as PLAUR and FPR2 suggests molecular mechanisms through which stress-related immune activation may contribute to vulnerability for anxiety and depressive disorders.

BackgroundThe relationship between neighborhood-level socioeconomic disadvantage and brain health is an emerging area of research with critical implications for public health and clinical practice, yet its influence on brain structure remains unclear. PurposeTo investigate the epidemiological association between neighborhood-level socioeconomic disadvantage [Area Deprivation Index (ADI)] and morphometric neuroimaging variables in a consecutive, non-disease enriched patient population. Materials and MethodsThis study, conducted at an academic medical center and associated community partners, used consecutive cross-sectional MRI neuroimaging data from 2,826 inpatient and outpatient individuals without radiological evidence of disease from January 2024 to June 2024. ADI, a geospatially determined index of neighborhood-level disadvantage, was calculated for each individual. Linear regressions tested the relationship between ADI and multiple morphometric variables: brain age gap (BAG; estimated - chronological BA), total brain tissue volume (TBV; total gray + white matter), five subcortical region volumes (hippocampus, thalamus, caudate, putamen, and nucleus accumbens) and four cortical region volumes [anterior cingulate cortex, posterior cingulate cortex, medial prefrontal cortex (MPFC), lateral PFC (LPFC)]. Volumetric measures were normalized to intracranial volume. Models controlled for age, sex, and total white matter hyperintensity volume (WMHV). Results2,826 individuals (mean age, 52.7 {+/-} 18.8 [standard deviation]; 1732 women) were evaluated. Residence in the 20% most disadvantaged neighborhoods was associated with a higher BAG ({beta}s > 2.12, Ps < .01) and decreased TBV ({beta}s < -5.12, Ps < .05). Additionally, increased WMHV was higher among those in the most disadvantaged neighborhoods (ts < - 2.50, Ps < .05) and associated with lower volume in most regions. Interaction models showed increased negative associations between WMHV and volumes of the caudate, nucleus accumbens, and lateral prefrontal cortex among those in the most disadvantaged neighborhoods. ConclusionsNeighborhood disadvantage is associated with adverse brain morphometry, including higher BAG, lower TBV, and amplified vascular-related regional volume loss. Key ResultsO_LIIn 2,826 adults (mean age, 53 years {+/-} 19; 1,732 women), residence in the most disadvantaged neighborhoods (national: 116/2,826, 4%; state: 129/2826, 5%) was associated with higher brain age gap at the national ({beta} = 2.12, 95% CI = 0.81 to 3.43, P = .001) and state levels ({beta} = 2.36; 95% CI = 1.10 to 3.61, P < .001). C_LIO_LITotal brain tissue volume was lower at the national ({beta} = -5.12, 95% CI = -10.13 to -0.11, P = .045) and state levels ({beta} = -6.13, 95% CI = -10.90 to -1.37, P = .011). C_LIO_LIWhite matter hyperintensity volume was higher in the most disadvantaged group (national: P = .013; state: P = .003) and demonstrated amplified associations with caudate, nucleus accumbens, and lateral prefrontal cortex volumes in the most disadvantaged group at the national and/or state levels (Ps < .05). C_LI

Acute stress activates the immune system, leading to the release of pro-inflammatory cytokines, such as interleukin-6 (IL-6). Chronic alcohol consumption alters the physiological stress systems and is associated with increased chronic inflammation. However, it remains unclear how IL-6 responds to acute stress in individuals with alcohol use disorder (AUD). Forty patients with AUD during early abstinence and 37 healthy controls (HC) completed two study visits. On one day, an acute stress induction task was performed, and on the other, a non-stressful control task, with the order of tasks being balanced. Plasma IL-6 and C-reactive protein (CRP) were measured as inflammatory markers at baseline and changes in IL-6 were assessed 90 minutes after the experimental manipulation. Patients with AUD showed significantly elevated baseline IL-6 and CRP compared to HC. In HC, inflammatory parameters were positively correlated with age and BMI, whereas in patients with AUD, they were correlated with the amount of consumed alcohol. IL-6 responses to the stress intervention did not differ between groups. Increases in IL-6 were observed on stress and control days and were larger when samples were collected via an indwelling catheter than with a butterfly needle. These findings suggest that heavy chronic alcohol use may mask the typical associations between inflammatory markers and physiological factors. However, IL-6 responses to acute stress do not differ between AUD and HC, despite increased baseline inflammation. Furthermore, the results indicate that blood collection methods can influence IL-6 measurements and highlight the importance of methodological considerations.

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.

Background Group A streptococcus (GAS) infections have been associated with neuropsychiatric disorders in epidemiologic studies and animal models, but data in US health care populations are limited. GAS is also associated with autoimmune sequelae, including acute rheumatic fever (ARF)/Sydenham chorea (SC), poststreptococcal reactive arthritis (PSRA), poststreptococcal glomerulonephritis (PSGN), and guttate psoriasis (GP). Epstein-Barr virus (EBV) has been linked to systemic lupus erythematosus (SLE) and multiple sclerosis (MS) and the complexity of these associations parallels that of GAS-associated conditions, providing a useful comparison. Objectives 1) Assess the association between a positive GAS test and incident neuropsychiatric diagnoses within 1 year in a large US health care database. 2) Assess the validity of the same database in detecting well-established disease associations while avoiding false associations. Design, Setting, Participants Retrospective cohort study using TriNetX data from US health care organizations. Patients with positive or negative tests were propensity score-matched (GAS cohort n=178,301; EBV cohort n=64,854). Patients with documented neuropsychiatric diagnoses prior to testing were excluded. To approximate a primary care population, inclusion required at least one well-visit. Exposures Positive vs negative GAS test; positive vs negative EBV test (separate cohorts). Main Outcomes and Validations Main outcome: incident neuropsychiatric diagnoses within 1 year of GAS testing. Positive control outcomes: ARF/SC, PSRA, PSGN, and GP (for GAS cohort); SLE and MS (for EBV cohort). Negative control outcomes: conditions without known association with GAS. Results After matching, a positive GAS test was associated with attention-deficit/hyperactivity disorder (ADHD) (RR: 1.09; 95% CI: 1.03-1.15). Among established poststreptococcal conditions, only GP was associated with prior GAS (RR: 1.75; 95% CI: 1.06-2.89). Case counts were insufficient to evaluate ARF/SC, PSRA, and PSGN. Negative control outcomes showed no association. In the EBV cohort, no association was observed with SLE, and MS showed a decreased risk. Conclusions and Relevance A positive GAS test was associated with ADHD but not with other neuropsychiatric disorders. The database detected poststreptococcal GP but did not identify most established postinfectious autoimmune associations, likely reflecting rarity, heterogeneity, and diagnostic complexity. These findings begin to describe the range of real-world health care databases to evaluate postinfectious neuropsychiatric risk.

Inflammatory bowel disease (IBD) frequently co-occurs with immune-mediated and metabolic disorders, but whether these associations reflect shared genetics or causal effects remains unclear. We performed two-sample Mendelian randomization (MR) using large-scale genome-wide association study (GWAS) summary statistics to investigate potential causal effects of immune-mediated diseases and lifestyle traits on IBD, Crohns disease (CD), and ulcerative colitis (UC). SNP-based heritability and genetic correlations were estimated to contextualize findings. Following false discovery rate correction, genetically predicted psoriasis was positively associated with IBD (OR 1.15), CD (OR 1.23), and UC (OR 1.10), with the strongest effect observed for CD. Genetically predicted type 2 diabetes mellitus (T2DM) showed a modest inverse association with UC (OR 0.88). No lifestyle-related traits remained significant after correction. Sensitivity analyses indicated heterogeneity across instruments and evidence of directional pleiotropy in selected models, whereas no pleiotropy was detected for the T2DM-UC association. These findings support a role of psoriasis-related immune pathways in IBD susceptibility and suggest a potential inverse association between genetic liability to T2DM and UC.