Causal Relationship Between Post-Traumatic Stress Disorder and Immune Cell Traits: A Mendelian Randomization Study.

INTRODUCTION: Post-traumatic stress disorder (PTSD) is a debilitating psychological disorder that occurs after exposure to catastrophic-level experiences. Although alterations in immune function have been identified in individuals with PTSD, the causal relationship between the two remains unclear. METHODS: To investigate the causal relationship between PTSD and immune function, we conducted the forward and backward two-sample Mendelian randomization (MR) analyses, based on summary-level genome-wide association studies (GWAS) data on PTSD and immune cell traits. RESULTS: For the forward MR analysis, PTSD was found to reduce the levels of CD62L- dendritic cell (DC) (beta = -0.254, FDR = 0.01), CD86+ myeloid DC (beta = -0.238, FDR = 0.014), CD62L- myeloid DC (beta = -0.26, FDR = 0.01), CD62L- CD86+ myeloid DC absolute count (beta = -0.264, FDR = 0.024), and CD62L- CD86+ myeloid DC (beta = -0.328, FDR = 0.002). In contrast, PTSD was observed to increase the level of CD28- CD8dim T-cell absolute count (beta = 0.27, FDR = 0.029). For the backward MR analysis, the odds ratio (OR) for CD33 on CD33dim HLA DR+ CD11b- in relation to PTSD risk was found to be 1.045 (95% CI = 1.021-1.069, FDR = 0.008). The OR for FSC-A on HLA DR+ CD8br was 1.048 (95% CI = 1.018-1.079, FDR = 0.039) and for CCR2 on CD14- CD16+ monocyte was 1.059 (95% CI = 1.027-1.092, FDR = 0.008). No significant pleiotropy was detected in both forward and backward MR analyses. CONCLUSION: The bidirectional MR study shed light on the intricate interplay between immune function and PTSD. The identification of a bidirectional causal relationship between T cells and PTSD opens new avenues for considering innovative approaches to the prevention and early intervention of PTSD.

Central innate immunization induces tolerance against post-traumatic stress disorder-like behavior and neuroinflammatory responses in male mice.

Post-traumatic stress disorder (PTSD) is a severe psychiatric disorder associated with abnormally elevated neuroinflammatory responses. Suppression of neuroinflammation is considered to be effective in ameliorating PTSD-like behaviors in rodents. Since pre-stimulation of microglia prior to stress exposure can prevent neuroinflammation, we hypothesized that pre-stimulation of microglia may prevent PTSD in animals. The results show that a single injection of a classical immune stimulant, lipopolysaccharide (LPS), at 50, 100 or 500, but not 10 µg/kg, one day before stress exposure, prevented the anxiety- and fear-like behaviors induced by modified single prolonged stress (mSPS). The time-dependent analysis shows that a single injection of LPS (100 µg/kg) either one or five, but not ten, days before stress prevented mSPS-induced anxiety- and fear-like behaviors. A second low-dose LPS injection 10 days after the first injection or a repeated LPS injection (4 × ) 10 days before stress induced tolerance to mSPS. Mechanistic studies show that a single injection of LPS one day before stress stimulation prevented mSPS-induced increases in levels of interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α), and IL-6 mRNA in the hippocampus and medial prefrontal cortex. Inhibition of microglia by pretreatment with minocycline or depletion of microglia by PLX3397 abolished the preventive effect of low-dose LPS pre-injection on mSPS-induced anxiety- and fear-like behavior and neuroinflammatory responses. These results suggest that pre-stimulation of microglia may prevent the development of PTSD-like behaviors by attenuating the development of neuroinflammatory responses. This could help to develop new strategies to prevent the damaging effects of harmful stress on the brain.

Microglia-mediated neuroimmune suppression in PTSD is associated with anhedonia.

Dynamic brain immune function in individuals with posttraumatic stress disorder is rarely studied, despite evidence of peripheral immune dysfunction. Positron emission tomography brain imaging using the radiotracer [11C]PBR28 was used to measure the 18-kDa translocator protein (TSPO), a microglial marker, at baseline and 3 h after administration of lipopolysaccharide (LPS), a potent immune activator. Data were acquired in 15 individuals with PTSD and 15 age-matched controls. The PTSD group exhibited a significantly lower magnitude LPS-induced increase in TSPO availability in an a priori prefrontal-limbic circuit compared to controls. Greater anhedonic symptoms in the PTSD group were associated with a more suppressed neuroimmune response. In addition, while a reduced granulocyte-macrophage colony-stimulating factor response to LPS was observed in the PTSD group, other measured cytokine responses and self-reported sickness symptoms did not differ between groups; these findings highlight group differences in central-peripheral immune system relationships. The results of this study provide evidence of a suppressed microglia-mediated neuroimmune response to a direct immune system insult in individuals with PTSD that is associated with the severity of symptoms. They also provide further support to an emerging literature challenging traditional concepts of microglial and immune function in psychiatric disease.

The Role of Lactylation in Regulating Microglial Inflammation in PTSD.

Lactylation plays an important regulatory role in neural development, neural stem cell fate determination, and the physiological function of the nervous system. Abnormal lactylation is closely related to the occurrence and development of hippocampal microglial inflammation in post-traumatic stress disorder (PTSD), so lactylation may serve as a potential therapeutic target for PTSD. This article reviewed the latest research progress on the involvement of lactylation in hippocampal microglial inflammation and its molecular mechanisms in PTSD.

Gender differences in the associations of psychosocial trauma and acute medical stressors with immune system activation and dementia risk.

Objective: The purpose of this article is to provide a narrative review synthesizing the literature on differences between women and men in relationships among certain stressors associated with immune system activation and their relationship to cognitive dysfunction and dementia. Method: We review the cycle of stress leading to neuroinflammation via cortisol and neurochemical alterations, cell-mediated immune system activation, and pro-inflammatory cytokines, and how this is implicated in the development of dementia. We follow this by discussing sex differences in stress physiology and immune function. We then review the work on early life adversity (ELA) and adverse childhood experiences (ACEs), post-traumatic stress disorder, acute medical stressors, and their associations with cognitive dysfunction and dementia. Throughout, we emphasize women's presentations and issues unique to women (e.g. trauma disorder prevalence). Conclusions: There is a need for more mechanistic and longitudinal studies that consider trauma accumulation, both physical and emotional, as well as a greater focus on traumas more likely to occur in women (e.g. sexual abuse), and their relationship to early cognitive decline and dementia.

Exploring the interplay between posttraumatic stress disorder, gut microbiota, and inflammatory biomarkers: a comprehensive meta-analysis.

Introduction: Posttraumatic stress disorder (PTSD) is the most common mental health disorder to develop following exposure to trauma. Studies have reported conflicting results regarding changes in immune biomarkers and alterations in the abundance of bacterial taxa and microbial diversity in patients with PTSD. Aim: The purpose of this meta-analysis is to summarize existing studies examining gut microbiota characteristics and changes in immune biomarkers in patients with PTSD. Methods: Relevant studies were systematically searched in PubMed, Scopus, and Embase, published in English between January 1, 1960, and December 1, 2023. The outcomes included changes in abundance and diversity in gut microbiota (gut microbiota part) and changes in immune biomarkers (immune part). Results: The meta-analysis included a total of 15 studies, with 9 focusing on changes in inflammatory biomarkers and 6 focusing on changes in gut microbiota composition in patients with PTSD. No differences were observed between groups for all inflammatory biomarkers (P≥0.05). Two of the six studies found that people with PTSD had less alpha diversity. However, the overall Standardized Mean Difference (SMD) for the Shannon Diversity Index was not significant (SMD 0.27, 95% CI -0.62-0.609, p = 0.110). Regarding changes in abundance, in two of the studies, a significant decrease in Lachnospiraceae bacteria was observed. Conclusion: This meta-analysis provides a comprehensive overview of gut microbiota characteristics in PTSD, suggesting potential associations with immune dysregulation. Future research should address study limitations, explore causal relationships, and consider additional factors influencing immune function in individuals with PTSD. Systematic review registration: https://www.crd.york.ac.uk, identifier CRD42023476590.

T-cell infiltration, contribution and regulation in the central nervous system post-traumatic injury.

T cells participate in the repair process and immune response in the CNS post-traumatic injury and play both a beneficial and harmful role. Together with nerve cells and other immune cells, they form a microenvironment in the CNS post-traumatic injury. The repair of traumatic CNS injury is a long-term process. T cells contribute to the repair of the injury site to influence the recovery. Recently, with the advance of new techniques, such as mass spectrometry-based flow cytometry, modern live-cell imaging, etc, research focusing on T cells is becoming one of the valuable directions for the future therapy of traumatic CNS injury. In this review, we summarized the infiltration, contribution and regulation of T cells in post-traumatic injury, discussed the clinical significance and predicted the future research direction.

COVID-19 patient transcriptomic and genomic profiling reveals comorbidity interactions with psychiatric disorders.

Psychiatric symptoms are seen in some COVID-19 patients, as direct or indirect sequelae, but it is unclear whether SARS-CoV-2 infection interacts with underlying neuronal or psychiatric susceptibilities. Such interactions might arise from COVID-19 immune responses, from infection of neurons themselves or may reflect social-psychological causes. To clarify this we sought the key gene expression pathways altered in COVID-19 also affected in bipolar disorder, post-traumatic stress disorder (PTSD) and schizophrenia, since this may identify pathways of interaction that could be treatment targets. We performed large scale comparisons of whole transcriptome data and immune factor transcript data in peripheral blood mononuclear cells (PBMC) from COVID-19 patients and patients with psychiatric disorders. We also analysed genome-wide association study (GWAS) data for symptomatic COVID-19 patients, comparing GWAS and whole-genome sequence data from patients with bipolar disorder, PTSD and schizophrenia patients. These studies revealed altered signalling and ontology pathways shared by COVID-19 patients and the three psychiatric disorders. Finally, co-expression and network analyses identified gene clusters common to the conditions. COVID-19 patients had peripheral blood immune system profiles that overlapped with those of patients with psychiatric conditions. From the pathways identified, PTSD profiles were the most highly correlated with COVID-19, perhaps consistent with stress-immune system interactions seen in PTSD. We also revealed common inflammatory pathways that may exacerbate psychiatric disorders, which may support the usage of anti-inflammatory medications in these patients. It also highlights the potential clinical application of multi-level dataset studies in difficult-to-treat psychiatric disorders in this COVID-19 pandemic.

Microglial deletion and inhibition alleviate behavior of post-traumatic stress disorder in mice.

BACKGROUND: Alteration of immune status in the central nervous system (CNS) has been implicated in the development of post-traumatic stress disorder (PTSD). However, the nature of overall changes in brain immunocyte landscape in PTSD condition remains unclear. METHODS: We constructed a mouse PTSD model by electric foot-shocks followed by contextual reminders and verified the PTSD-related symptoms by behavior test (including contextual freezing test, open-field test, and elevated plus maze test). We examined the immunocyte panorama in the brains of the naïve or PTSD mice by using single-cell mass cytometry. Microglia number and morphological changes in the hippocampus, prefrontal cortex, and amygdala were analyzed by histopathological methods. The gene expression changes of those microglia were detected by quantitative real-time PCR. Genetic/pharmacological depletion of microglia or minocycline treatment before foot-shocks exposure was performed to study the role of microglia in PTSD development and progress. RESULTS: We found microglia are the major brain immune cells that respond to PTSD. The number of microglia and ratio of microglia to immunocytes was significantly increased on the fifth day of foot-shock exposure. Furthermore, morphological analysis and gene expression profiling revealed temporal patterns of microglial activation in the hippocampus of the PTSD brains. Importantly, we found that genetic/pharmacological depletion of microglia or minocycline treatment before foot-shock exposure alleviated PTSD-associated anxiety and contextual fear. CONCLUSION: Our results demonstrated a critical role for microglial activation in PTSD development and a potential therapeutic strategy for the clinical treatment of PTSD in the form of microglial inhibition.

PTSD is associated with neuroimmune suppression: evidence from PET imaging and postmortem transcriptomic studies.

Despite well-known peripheral immune activation in posttraumatic stress disorder (PTSD), there are no studies of brain immunologic regulation in individuals with PTSD. [11C]PBR28 Positron Emission Tomography brain imaging of the 18-kDa translocator protein (TSPO), a microglial biomarker, was conducted in 23 individuals with PTSD and 26 healthy individuals-with or without trauma exposure. Prefrontal-limbic TSPO availability in the PTSD group was negatively associated with PTSD symptom severity and was significantly lower than in controls. Higher C-reactive protein levels were also associated with lower prefrontal-limbic TSPO availability and PTSD severity. An independent postmortem study found no differential gene expression in 22 PTSD vs. 22 controls, but showed lower relative expression of TSPO and microglia-associated genes TNFRSF14 and TSPOAP1 in a female PTSD subgroup. These findings suggest that peripheral immune activation in PTSD is associated with deficient brain microglial activation, challenging prevailing hypotheses positing neuroimmune activation as central to stress-related pathophysiology.

Immediate psychological distress in quarantined patients with COVID-19 and its association with peripheral inflammation: A mixed-method study.

Since the end of 2019, Corona Virus Disease 2019 (COVID-19) has been the cause of a worldwide pandemic. The mental status of patients with COVID-19 who have been quarantined and the interactions between their psychological distress and physiological levels of inflammation have yet to be analyzed. Using a mixed-method triangulation design (QUAN + QUAL), this study investigated and compared the mental status and inflammatory markers of 103 patients who, while hospitalized with mild symptoms, tested positive with COVID-19 and 103 matched controls that were COVID-19 negative. The severity of depression, anxiety, and post-traumatic stress symptoms (PTSS) was measured via an on-line survey. Using a convenience sampling technique, qualitative data were collected until the point of data saturation. In addition, a semi-structured interview was conducted among five patients with COVID-19. Peripheral inflammatory markers were also collected in patients, both at baseline and within ± three days of completing the on-line survey. Results revealed that COVID-19 patients, when compared to non-COVID controls, manifested higher levels of depression (P < 0.001), anxiety (P < 0.001), and post-traumatic stress symptoms (P < 0.001). A gender effect was observed in the score of "Perceived Helplessness", the subscale of PSS-10, with female patients showing higher scores compared to male patients (Z = 2.56, P = 0.010), female (Z = 2.37, P = 0.018) and male controls (Z = 2.87, P = 0.004). Levels of CRP, a peripheral inflammatory indicator, correlated positively with the PHQ-9 total score (R = 0.37, P = 0.003, Spearman's correlation) of patients who presented symptoms of depression. Moreover, the change of CRP level from baseline inversely correlated with the PHQ-9 total score (R = -0.31, P = 0.002), indicative of improvement of depression symptoms. Qualitative analysis revealed similar results with respect to patient reports of negative feelings, including fear, guilt, and helplessness. Stigma and uncertainty of viral disease progression were two main concerns expressed by COVID-19 patients. Our results indicate that significant psychological distress was experienced by hospitalized COVID-19 patients and that levels of depressive features may be related to the inflammation markers in these patients. Thus, we recommend that necessary measures should be provided to address depression and other psychiatric symptoms for COVID-19 patients and attention should be paid to patient perceived stigma and coping strategies when delivering psychological interventions.

High IL-6 in military personnel relates to multiple traumatic brain injuries and post-traumatic stress disorder.

Repetitive traumatic brain injuries (TBIs) among military personnel have been linked to chronic behavioral and neurological symptoms, and poor health outcomes. Repetitive TBIs may impact inflammation, which may offer some explanation of the biological basis of these long-term risks, and may improve the care that is provided to these individuals. This study examines the concentrations of TNFα, IL-6 and IL-10 and associations with behavioral symptoms, including post-traumatic stress disorder symptoms and depression in a cohort of 106 military personnel and Veterans with a history of TBI. Group comparisons conducted for those with repetitive TBIs (> 3; n = 44), to participants with less than three TBIs (n = 29), and controls with no TBIs (n = 33). The primary outcomes were serum levels of inflammatory related proteins TNF-α, IL-6 and IL-10, TBI history, and PTSD symptoms. IL-6 mean concentration was significantly higher in the repetitive TBI group compared to those with 1-2 TBI or no TBI history (p = 0.050). Additionally, for participants with a history of TBI, PTSD symptom severity, specifically, intrusion (p = .006 and p = .007) and avoidance (p = .034 and .009), were significant predictors of higher IL-6 and IL-10 concentrations respectively. These findings suggest that repetitive TBIs concurrent with high PTSD symptoms in military personnel and Veterans are associated with chronic inflammation, and specifically elevated concentrations of IL-6. Examining the changes in inflammatory processes may identify potential therapeutic targets for early intervention after TBI in order to prevent the development of neurological deficits and disorders.

Are we facing a crashing wave of neuropsychiatric sequelae of COVID-19? Neuropsychiatric symptoms and potential immunologic mechanisms.

The coronavirus disease 19 (COVID-19) pandemic is a significant psychological stressor in addition to its tremendous impact on every facet of individuals' lives and organizations in virtually all social and economic sectors worldwide. Fear of illness and uncertainty about the future precipitate anxiety- and stress-related disorders, and several groups have rightfully called for the creation and dissemination of robust mental health screening and treatment programs for the general public and front-line healthcare workers. However, in addition to pandemic-associated psychological distress, the direct effects of the virus itself (several acute respiratory syndrome coronavirus; SARS-CoV-2), and the subsequent host immunologic response, on the human central nervous system (CNS) and related outcomes are unknown. We discuss currently available evidence of COVID-19 related neuropsychiatric sequelae while drawing parallels to past viral pandemic-related outcomes. Past pandemics have demonstrated that diverse types of neuropsychiatric symptoms, such as encephalopathy, mood changes, psychosis, neuromuscular dysfunction, or demyelinating processes, may accompany acute viral infection, or may follow infection by weeks, months, or longer in recovered patients. The potential mechanisms are also discussed, including viral and immunological underpinnings. Therefore, prospective neuropsychiatric monitoring of individuals exposed to SARS-CoV-2 at various points in the life course, as well as their neuroimmune status, are needed to fully understand the long-term impact of COVID-19, and to establish a framework for integrating psychoneuroimmunology into epidemiologic studies of pandemics.

Role of enhanced glucocorticoid receptor sensitivity in inflammation in PTSD: insights from computational model for circadian-neuroendocrine-immune interactions.

Although glucocorticoid resistance contributes to increased inflammation, individuals with posttraumatic stress disorder (PTSD) exhibit increased glucocorticoid receptor (GR) sensitivity along with increased inflammation. It is not clear how inflammation coexists with a hyperresponsive hypothalamic-pituitary-adrenal (HPA) axis. To understand this better, we developed and analyzed an integrated mathematical model for the HPA axis and the immune system. We performed mathematical simulations for a dexamethasone (DEX) suppression test and IC50-dexamethasone for cytokine suppression by varying model parameters. The model analysis suggests that increasing the steepness of the dose-response curve for GR activity may reduce anti-inflammatory effects of GRs at the ambient glucocorticoid levels, thereby increasing proinflammatory response. The adaptive response of proinflammatory cytokine-mediated stimulatory effects on the HPA axis is reduced due to dominance of the GR-mediated negative feedback on the HPA axis. To verify these hypotheses, we analyzed the clinical data on neuroendocrine variables and cytokines obtained from war-zone veterans with and without PTSD. We observed significant group differences for cortisol and ACTH suppression tests, proinflammatory cytokines TNFα and IL6, high-sensitivity C-reactive protein, promoter methylation of GR gene, and IC50-DEX for lysozyme suppression. Causal inference modeling revealed significant associations between cortisol suppression and post-DEX cortisol decline, promoter methylation of human GR gene exon 1F (NR3C1-1F), IC50-DEX, and proinflammatory cytokines. We noted significant mediation effects of NR3C1-1F promoter methylation on inflammatory cytokines through changes in GR sensitivity. Our findings suggest that increased GR sensitivity may contribute to increased inflammation; therefore, interventions to restore GR sensitivity may normalize inflammation in PTSD.

Dysregulation of inflammation, neurobiology, and cognitive function in PTSD: an integrative review.

Compelling evidence from animal and human research suggest a strong link between inflammation and posttraumatic stress disorder (PTSD). Furthermore, recent findings support compromised neurocognitive function as a key feature of PTSD, particularly with deficits in attention and processing speed, executive function, and memory. These cognitive domains are supported by brain structures and neural pathways that are disrupted in PTSD and which are implicated in fear learning and extinction processes. The disruption of these supporting structures potentially results from their interaction with inflammation. Thus, the converging evidence supports a model of inflammatory dysregulation and cognitive dysfunction as combined mechanisms underpinning PTSD symptomatology. In this review, we summarize evidence of dysregulated inflammation in PTSD and further explore how the neurobiological underpinnings of PTSD, in the context of fear learning and extinction acquisition and recall, may interact with inflammation. We then present evidence for cognitive dysfunction in PTSD, highlighting findings from human work. Potential therapeutic approaches utilizing novel pharmacological and behavioral interventions that target inflammation and cognition also are discussed.

Proinflammatory status-stratified blood transcriptome profiling of civilian women with PTSD.

Etiology of posttraumatic stress disorder (PTSD) remains largely unknown. Studies have shown that a significant subset of patients with PTSD exhibit increased inflammation, suggesting that the understanding of this disorder could be facilitated by classifying these patients by inflammatory status. Here we performed a microarray-based blood transcriptome analysis on proinflammatory status-stratified Japanese civilian women with PTSD most of whom developed the disorder after experiencing interpersonal violence. By utilizing our previously identified cut-off serum interleukin-6 (IL-6) level that approximately corresponded to the median IL-6 level of our PTSD patients, we classified patients into those with high IL-6 levels and those with normal IL-6 levels (n = 16 for each). Transcriptome profiles of these 2 groups were compared with the profile of 16 age-matched healthy control women. Differentially expressed genes between high IL-6 patients and controls showed significant enrichment in a number of gene ontology terms and pathways primarily involved in immune/inflammatory responses, and their protein-protein interaction network was significantly enriched. In contrast, differentially expressed genes between normal IL-6 patients and controls showed significant enrichment in several gene ontology terms related to ion transport and neural function. The microarray data were confirmed by reverse transcription quantitative PCR. These findings illustrate the heterogeneous molecular mechanisms of PTSD within this relatively homogeneous sample in terms of sex, trauma type, and ethnicity, suggesting that peripheral proinflammatory status such as IL-6 levels could be a useful subtyping marker for this disorder. With further research, it is hoped that our findings will be translated into personalized medicine.