Neuroinflammatory genes associated with post-traumatic stress disorder: implications for comorbidity

Psychological and biological mechanisms linking trauma with cardiovascular disease risk

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide, and experiences of psychological trauma have been associated with subsequent CVD onset. Identifying key pathways connecting trauma with CVD has the potential to inform more targeted screening and intervention efforts to offset elevated cardiovascular risk. In this narrative review, we summarize the evidence for key psychological and biological mechanisms linking experiences of trauma with CVD risk. Additionally, we describe various methodologies for measuring these mechanisms in an effort to inform future research related to potential pathways. With regard to mechanisms involving posttraumatic psychopathology, the vast majority of research on psychological distress after trauma and CVD has focused on posttraumatic stress disorder (PTSD), even though posttraumatic psychopathology can manifest in other ways as well. Substantial evidence suggests that PTSD predicts the onset of a range of cardiovascular outcomes in trauma-exposed men and women, yet more research is needed to better understand posttraumatic psychopathology more comprehensively and how it may relate to CVD. Further, dysregulation of numerous biological systems may occur after trauma and in the presence of posttraumatic psychopathology; these processes of immune system dysregulation and elevated inflammation, oxidative stress, mitochondrial dysfunction, renin-angiotensin system dysregulation, and accelerated biological aging may all contribute to subsequent cardiovascular risk, although more research on these pathways in the context of traumatic stress is needed. Given that many of these mechanisms are closely intertwined, future research using a systems biology approach may prove fruitful for elucidating how processes unfold to contribute to CVD after trauma.

The hippocampus in stress susceptibility and resilience: Reviewing molecular and functional markers

Understanding the individual variability that comes with the likelihood of developing stress-related psychopathologies is of paramount importance when addressing mechanisms of their neurobiology. This article focuses on the hippocampus as a region that is highly influenced by chronic stress exposure and that has strong ties to the development of related disorders, such as depression and post-traumatic stress disorder. We first outline three commonly used animal models that have been used to separate animals into susceptible and resilient cohorts. Next, we review molecular and functional hippocampal markers of susceptibility and resilience. We propose that the hippocampus plays a crucial role in the differences in the processing and storage of stress-related information in animals with different stress susceptibilities. These hippocampal markers not only help us attain a more comprehensive understanding of the various facets of stress-related pathophysiology, but also could be targeted for the development of new treatments.

Mechanisms by which adverse childhood experiences, other traumas and PTSD influence the health and well-being of individuals with eating disorders throughout the life span

BACKGROUND

Multiple published sources from around the world have confirmed an association between an array of adverse childhood experiences (ACEs) and other traumatic events with eating disorders (EDs) and related adverse outcomes, including higher morbidity and mortality.

METHODS

In keeping with this Special Issue's goals, this narrative review focuses on the ACEs pyramid and its purported mechanisms through which child maltreatment and other forms of violence toward human beings influence the health and well-being of individuals who develop EDs throughout the life span. Relevant literature on posttraumatic stress disorder (PTSD) is highlighted when applicable.

RESULTS

At every level of the pyramid, it is shown that EDs interact with each of these proclaimed escalating mechanisms in a bidirectional manner that contributes to the predisposition, precipitation and perpetuation of EDs and related medical and psychiatric comorbidities, which then predispose to early death. The levels and their interactions that are discussed include the contribution of generational embodiment (genetics) and historical trauma (epigenetics), social conditions and local context, the ACEs and other traumas themselves, the resultant disrupted neurodevelopment, subsequent social, emotional and cognitive impairment, the adoption of health risk behaviors, and the development of disease, disability and social problems, all resulting in premature mortality by means of fatal complications and/or suicide.

CONCLUSIONS

The implications of these cascading, evolving, and intertwined perspectives have important implications for the assessment and treatment of EDs using trauma-informed care and trauma-focused integrated treatment approaches. This overview offers multiple opportunities at every level for the palliation and prevention of EDs and other associated trauma-related conditions, including PTSD.

A review for the pharmacological effects of paeoniflorin in the nervous system

Paeoniflorin, a terpenoid glycoside compound extracted from Paeonia lactiflora Pall, shows preventive and therapeutic effects in various types of nervous system disorders. However, to date, no comprehensive knowledge on the pharmacological effects of paeoniflorin on the nervous system is available online. Clarification of this issue may be useful for the development of paeoniflorin as a new drug for the treatment of nervous system disorders. To this end, the authors summarize the pharmacological aspects of paeoniflorin and its possible mechanisms, such as restoration of mitochondrial function; inhibition of neuroinflammation, oxidative stress, and cellular apoptosis; activation of adenosine A1 receptor, cAMP response element-binding protein (CREB) and extracellular signal-regulated kinase 1/2 (ERK1/2); or enhancement of brain-derived neurotrophic factor and serotonin function, in the prevention of disorders such as cerebral ischemia, subarachnoid hemorrhage, vascular dementia, Alzheimer's disease, Parkinson's disease, depression, post-traumatic syndrome disorder, and epilepsy, by reviewing the previously published literature.

Amentoflavone impairs the reconsolidated fear memories through inhibition of ERK pathway

Post-traumatic stress disorder (PTSD) is a pathological fear memory-related disease. The persistence of pathological fearful memories is one of the most characteristic symptoms of PTSD. However, this can be eliminated by intervening in reconsolidation. Inflammation is intimately involved in the pathophysiologic progression of PTSD. Amentoflavone (AF) has anti-inflammatory effects. However, the effect of AF on fear memory reconsolidation remains unclear. In the present series of experiments, the CFC paradigm of rats were constructed. This was followed by AF administration immediately after exposure to the conditioning chamber to observe the maintenance of fear memory. Finally, a Western blot for the amygdala was used to explore the possible molecular biological mechanisms of AF affecting animal behavior. The findings suggest that re-exposure to the conditioning chamber for retrieval of CFC memory followed by immediate intragastric AF administration in rats attenuated the fear response for at least 14 days. In addition, the Western blot results show that the CFC memory intervention effect of AF administration during the reconsolidation phase may be related to the ERK signaling pathway inhibition. In general, the administration of AF in the reconsolidation phase to inhibit neuroinflammation can block the reconsolidation process and disrupt fear memory retention in the long term, at least in part through ERK pathway.

MicroRNA-124 attenuates PTSD-like behaviors and reduces the level of inflammatory cytokines by downregulating the expression of TRAF6 in the hippocampus of rats following single-prolonged stress

BACKGROUND

MicroRNA-124-3p (miR-124) plays an important role in neuroprotective functions in various neurological disorders, but whether miR-124 participates in the pathological progression of posttraumatic stress disorder (PTSD) remains poorly understood.

METHODS

In the present study, we assessed the level of neuroinflammation in the hippocampus of rats exposed to single-prolonged stress (SPS) by Western blot and immunofluorescence staining, while the effect of miR-124 on PTSD-like behaviors was evaluated by behavioral test.

RESULTS

Our results showed that the level of miR-124 in the hippocampus of rats exposed to SPS was downregulated and that the upregulation of miR-124 could alleviate the PTSD-like behaviors of SPS rats. This effect of miR-124 might be achieved through TNF receptor-associated Factor 6 (TRAF6), which is a target gene of miR-124 and plays an important role in the immune and inflammatory reaction by regulating nuclear factor kappa-B (NF-κB). Furthermore, we found that miR-124 not only decreased the level of proinflammatory cytokines but also increased the expression levels of synaptic proteins (PSD95 and synapsin I) and regulated the morphology of neurons.

CONCLUSION

These results suggested that miR-124 might attenuate PTSD-like behaviors and decrease the level of proinflammatory cytokines by downregulating the expression of TRAF6 in the hippocampus of rats exposed to SPS.

The Cannabis Constituent Cannabigerol Does Not Disrupt Fear Memory Processes or Stress-Induced Anxiety in Mice

Introduction: Medicinal cannabis has proliferated around the world and there is increasing interest in the therapeutic potential of individual plant-derived cannabinoids (phytocannabinoids). Preclinical evidence suggests the phytocannabinoid cannabigerol (CBG) could be useful in treating brain disorders, including stress and anxiety-related disorders. In this study, we aimed to explore whether CBG disrupts various contextually conditioned fear memory processes and trauma-induced anxiety-related behavior in a mouse model of post-traumatic stress disorder (PTSD). Materials and Methods: All mice underwent contextual fear conditioning. CBG was administered between 1 and 60 mg/kg intraperitoneally (i.p.). We first assessed the effects of repeated CBG exposure on long-term fear memories. We also examined whether acute CBG affected various fear memory processes, namely expression, acquisition, consolidation, and reconsolidation of conditioned fear. Finally, the effect of acute CBG administration on stress-induced anxiety in the light/dark test was assessed. Results: Repeated CBG exposure did not affect long-term conditioned fear that was observed 24 days after the conditioning session. Moreover, acute CBG administration did not influence the acquisition, consolidation, reconsolidation, or expression of contextually conditioned fear. Acute CBG treatment also did not affect stress-induced anxiety-related behaviors in the light/dark test. Conclusions: CBG was ineffective in disrupting long-term fear memories, various conditioned fear memory processes, or stress-induced anxiety-related behavior in mice. These preclinical data suggest CBG may have limited scope in the treatment of PTSD and stress-related anxiety.

Central and Peripheral Immune Dysregulation in Posttraumatic Stress Disorder: Convergent Multi-Omics Evidence

Posttraumatic stress disorder (PTSD) is a chronic and multifactorial disorder with a prevalence ranging between 6–10% in the general population and ~35% in individuals with high lifetime trauma exposure. Growing evidence indicates that the immune system may contribute to the etiology of PTSD, suggesting the inflammatory dysregulation as a hallmark feature of PTSD. However, the potential interplay between the central and peripheral immune system, as well as the biological mechanisms underlying this dysregulation remain poorly understood. The activation of the HPA axis after trauma exposure and the subsequent activation of the inflammatory system mediated by glucocorticoids is the most common mechanism that orchestrates an exacerbated immunological response in PTSD. Recent high-throughput analyses in peripheral and brain tissue from both humans with and animal models of PTSD have found that changes in gene regulation via epigenetic alterations may participate in the impaired inflammatory signaling in PTSD. The goal of this review is to assess the role of the inflammatory system in PTSD across tissue and species, with a particular focus on the genomics, transcriptomics, epigenomics, and proteomics domains. We conducted an integrative multi-omics approach identifying TNF (Tumor Necrosis Factor) signaling, interleukins, chemokines, Toll-like receptors and glucocorticoids among the common dysregulated pathways in both central and peripheral immune systems in PTSD and propose potential novel drug targets for PTSD treatment.

Bruton's tyrosine kinase drives neuroinflammation and anxiogenic behavior in mouse models of stress

BACKGROUND

Current therapies targeting several neurotransmitter systems are only able to partially mitigate the symptoms of stress- and trauma-related disorder. Stress and trauma-related disorders lead to a prominent inflammatory response in humans, and in pre-clinical models. However, mechanisms underlying the induction of neuroinflammatory response in PTSD and anxiety disorders are not clearly understood. The present study investigated the mechanism underlying the activation of proinflammatory NLRP3 inflammasome and IL1β in mouse models of stress.

METHODS

We used two mouse models of stress, i.e., mice subjected to physical restraint stress with brief underwater submersion, and predator odor stress. Mice were injected with MCC950, a small molecule specific inhibitor of NLRP3 activation. To pharmacologically inhibit BTK, a specific inhibitor ibrutinib was used. To validate the observation from ibrutinib studies, a separate group of mice was injected with another BTK-specific inhibitor LFM-A13. Seven days after the induction of stress, mice were examined for anxious behavior using open field test (OFT), light-dark test (LDT), and elevated plus maze test (EPM). Following the behavior tests, hippocampus and amygdale were extracted and analyzed for various components of NLRP3-caspase 1-IL1β pathway. Plasma and peripheral blood mononuclear cells were also used to assess the induction of NLRP3-Caspase 1-IL-1β pathway in stressed mice.

RESULTS

Using two different pre-clinical models of stress, we demonstrate heightened anxious behavior in female mice as compared to their male counterparts. Stressed animals exhibited upregulation of proinflammatory IL1β, IL-6, Caspase 1 activity and NLRP3 inflammasome activation in brain, which were significantly higher in female mice. Pharmacological inhibition of NLRP3 inflammasome activation led to anxiolysis as well as attenuated neuroinflammatory response. Further, we observed induction of activated Bruton's tyrosine kinase (BTK), an upstream positive-regulator of NLRP3 inflammasome activation, in hippocampus and amygdala of stressed mice. Next, we conducted proof-of-concept pharmacological BTK inhibitor studies with ibrutinib and LFM-A13. In both sets of experiments, we found BTK inhibition led to anxiolysis and attenuated neuroinflammation, as indicated by significant reduction of NLRP3 inflammasome and proinflammatory IL-1β in hippocampus and amygdala. Analysis of plasma and peripheral blood mononuclear cells indicated peripheral induction of NLRP3-caspase 1-IL1β pathway in stressed mice.

CONCLUSION

Our study identified BTK as a key upstream regulator of neuroinflammation, which drives anxiogenic behavior in mouse model of stress. Further, we demonstrated the sexually divergent activation of BTK, providing a clue to heightened neuroinflammation and anxiogenic response to stress in females as compared to their male counterparts. Our data from the pharmacological inhibition studies suggest BTK as a novel target for the development of potential clinical treatment of PTSD and anxiety disorders. Induction of pBTK and NLRP3 in peripheral blood mononuclear cells of stressed mice suggest the potential effect of stress on systemic inflammation.

Inflammatory neuropsychiatric disorders and COVID-19 neuroinflammation

Neuropsychiatric sequalae to coronavirus disease 2019 (COVID-19) infection are beginning to emerge, like previous Spanish influenza and severe acute respiratory syndrome episodes. Streptococcal infection in paediatric patients causing obsessive compulsive disorder (PANDAS) is another recent example of an infection-based psychiatric disorder. Inflammation associated with neuropsychiatric disorders has been previously reported but there is no standard clinical management approach established. Part of the reason is that it is unclear what factors determine the specific neuronal vulnerability and the efficacy of anti-inflammatory treatment in neuroinflammation. The emerging COVID-19 data suggested that in the acute stage, widespread neuronal damage appears to be the result of abnormal and overactive immune responses and cytokine storm is associated with poor prognosis. It is still too early to know if there are long-term-specific neuronal or brain regional damages associated with COVID-19, resulting in distinct neuropsychiatric disorders. In several major psychiatric disorders where neuroinflammation is present, patients with abnormal inflammatory markers may also experience less than favourable response or treatment resistance when standard treatment is used alone. Evidence regarding the benefits of co-administered anti-inflammatory agents such as COX-2 inhibitor is encouraging in selected patients though may not benefit others. Disease-modifying therapies are increasingly being applied to neuropsychiatric diseases characterised by abnormal or hyperreactive immune responses. Adjunct anti-inflammatory treatment may benefit selected patients and is definitely an important component of clinical management in the presence of neuroinflammation.

Hippocampal TNF-α Signaling Mediates Heroin Withdrawal-Enhanced Fear Learning and Withdrawal-Induced Weight Loss

There is significant comorbidity of opioid use disorder (OUD) and post-traumatic stress disorder (PTSD) in clinical populations. However, the neurobiological mechanisms underlying the relationship between chronic opioid use and withdrawal and development of PTSD are poorly understood. Our previous work identified that chronic escalating heroin administration and withdrawal can produce enhanced fear learning, an animal model of hyperarousal, and is associated with an increase in dorsal hippocampal (DH) interleukin-1β (IL-1β). However, other cytokines, such as TNF-α, work synergistically with IL-1β and may have a role in the development of enhanced fear learning. Based on both translational rodent and clinical studies, TNF-α has been implicated in hyperarousal states of PTSD, and has an established role in hippocampal-dependent learning and memory. The first set of experiments tested the hypothesis that chronic heroin administration followed by withdrawal is capable of inducing alterations in DH TNF-α expression. The second set of experiments examined whether DH TNF-α expression is functionally relevant to the development of enhanced fear learning. We identified an increase of TNF-α immunoreactivity and positive cells at 0, 24, and 48 h into withdrawal in the dentate gyrus DH subregion. Interestingly, intra-DH infusions of etanercept (TNF-α inhibitor) 0, 24, and 48 h into heroin withdrawal prevented the development of enhanced fear learning and mitigated withdrawal-induced weight loss. Overall, these findings provide insight into the role of TNF-α in opioid withdrawal and the development of anxiety disorders such as PTSD.

White Matter Alterations Are Associated With Cognitive Dysfunction Decades After Moderate-to-Severe Traumatic Brain Injury and/or Posttraumatic Stress Disorder

BACKGROUND

Possible white matter (WM) alterations following moderate-to-severe traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) and their relationship to clinical outcome have yet to be investigated decades after trauma. We utilized structural magnetic resonance imaging and diffusion tensor images to investigate brain volume and WM alterations in Vietnam War veterans with moderate-to-severe TBI and/or PTSD examined 5 decades after trauma.

METHODS

Data from 160 veterans-history of moderate-to-severe TBI (n = 23), history of TBI+PTSD (n = 36), history of PTSD (n = 53), and control veterans (n = 48)-were obtained from the Department of Defense Alzheimer's Disease Neuroimaging Initiative database. Voxel-based morphometry and tract-based spatial statistics were used to investigate ongoing brain morphometry and WM abnormalities. The fractional anisotropy (FA) and mean diffusivity were then correlated with neuropsychological scores and amyloid deposition in the trauma groups.

RESULTS

Compared with control subjects, the three trauma groups showed gray matter atrophy, lower FA, and distinctly higher diffusivity in the major WM tracts, including the corpus callosum, external and internal capsules, cingulum, and inferior and superior longitudinal fasciculi. The FA and mean diffusivity correlated with cognitive deficits in the trauma groups. Furthermore, the FA in the cingulum correlated negatively with amyloid deposition in the posterior cingulate cortex of all three trauma groups.

CONCLUSIONS

Diffusion tensor imaging detected WM abnormalities that correlated with the severity of present cognitive dysfunction and the degree of cortical amyloid deposition decades after moderate-to-severe TBI and/or PTSD. These results may hint that PTSD secondary to TBI may incur late cognitive sequalae and persistence of brain microstructure alterations.

Association of CRP genetic variation with symptomatology, cognitive function, and circulating proinflammatory markers in civilian women with PTSD

BACKGROUND

Posttraumatic stress disorder (PTSD) has been associated with increased inflammation. C-reactive protein (CRP) is a marker of systemic inflammation, and recently, single nucleotide polymorphisms (SNPs) in the CRP gene have been associated with increased blood CRP protein levels and illness severity in PTSD patients. However, the mechanism by which the CRP SNPs are involved in PTSD remains unclear. Here we investigated the association of CRP genetic variation with blood proinflammatory protein levels, symptomatology, and cognitive function, and further explored the moderating effect of childhood maltreatment history, in adult patients with PTSD.

METHODS

Fifty-seven Japanese civilian women with PTSD and 73 healthy control women were enrolled. Three SNPs in the CRP gene, namely rs2794520, rs1130864, and rs3093059, were genotyped, and analyses focused on rs2794520 (T/C). Serum levels of high-sensitivity CRP (hsCRP), high-sensitivity tumor necrosis factor-α (hsTNF-α), and interleukin-6 were measured. PTSD symptoms were evaluated by the Posttraumatic Diagnostic Scale. Cognitive function was assessed by the Repeatable Battery for the Assessment of Neuropsychological Status. Childhood maltreatment history was assessed by the Childhood Trauma Questionnaire.

RESULTS

Patients with the rs2794520 CC/CT genotype, compared to those with the TT genotype, showed significantly higher levels of hsCRP (p=0.009) and hsTNF-α (p=0.001), more severe PTSD symptoms (p=0.036), and poorer cognitive function (p=0.018). A two-way analysis of variance revealed a significant genotype-by-maltreatment interaction for more severe PTSD avoidance symptom (p=0.012).

LIMITATIONS

The relatively small sample size limited our findings.

CONCLUSIONS

These findings may provide an insight into the etiology of PTSD from the inflammatory perspective.

Translocator protein 18 kDa: a potential therapeutic biomarker for post traumatic stress disorder

Post traumatic stress disorder (PTSD) is widely regarded as a stress-related and trauma disorder. The symptoms of PTSD are characterized as a spectrum of vulnerabilities after the exposure to an extremely traumatic stressor. Considering as one of complex mental disorders, little progress has been made toward its diagnostic biomarkers, despite the involvement of PTSD has been studied. Many studies into the underlying neurobiology of PTSD implicated the dysfunction of neurosteroids biosynthesis and neuorinflammatory processes. Translocator protein 18 kDa (TSPO) has been considered as one of the promising therapeutic biomarkers for neurological stress disorders (like PTSD, depression, anxiety, et al) without the benzodiazepine-like side effects. This protein participates in the formation of neurosteroids and modulation of neuroinflammation. The review outlines current knowledge involving the role of TSPO in the neuropathology of PTSD and the anti-PTSD-like effects of TSPO ligands.

Mast cell-mediated neuroinflammation may have a role in attention deficit hyperactivity disorder (Review)

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental and behavioral disorder with a serious negative impact on the quality of life from childhood until adulthood, which may cause academic failure, family disharmony and even social unrest. The pathogenesis of ADHD has remained to be fully elucidated, leading to difficulties in the treatment of this disease. Genetic and environmental factors contribute to the risk of ADHD development. Certain studies indicated that ADHD has high comorbidity with allergic and autoimmune diseases, with various patients with ADHD having a high inflammatory status. Increasing evidence indicated that mast cells (MCs) are involved in the pathogenesis of brain inflammation and neuropsychiatric disorders. MCs may cause or aggravate neuroinflammation via the selective release of inflammatory factors, interaction with glial cells and neurons, activation of the hypothalamic-pituitary adrenal axis or disruption of the blood-brain barrier integrity. In the present review, the notion that MC activation may be involved in the occurrence and development of ADHD through a number of ways is discussed based on previously published studies. The association between MCs and ADHD appears to lack sufficient evidence at present and this hypothesis is considered to be worthy of further study, providing a novel perspective for the treatment of ADHD.

Shedding Light on the Transcriptomic Dark Matter in Biological Psychiatry: Role of Long Noncoding RNAs in D-cycloserine-Induced Fear Extinction in Posttraumatic Stress Disorder

Biological psychiatry scholarship on posttraumatic stress disorder (PTSD) is making strides with new omics technologies. In this context, there is growing recognition that noncoding RNAs are vital for the regulation of gene and protein expression. Long noncoding RNAs (lncRNAs) can modulate splicing, influence RNA editing, messenger RNA (mRNA) stability, translation activation, and microRNA-mRNA interactions, are highly abundant in the brain, and have been implicated in neurodevelopmental disorders. The largest subclass of lncRNAs is long intergenic noncoding RNAs (lincRNAs). We report on lincRNAs and their predicted mRNA targets associated with fear extinction induced by co-administration of D-cycloserine and behavioral fear extinction in a PTSD animal model. Forty-three differentially expressed lincRNAs and 190 differentially expressed mRNAs were found to be associated with fear extinction. Eight lincRNAs were predicted to interact with and regulate 108 of these mRNAs, while seven lincRNAs were predicted to interact with 22 of their pre-mRNA transcripts. Based on the functions of their target mRNAs, we inferred that these lincRNAs bind to nucleotides, ribonucleotides, and proteins; subsequently influence nervous system development, morphology, and immune system functioning; and could be associated with nervous system and mental health disorders. We found the quantitative trait loci that overlapped with fear extinction-related lincRNAs included traits such as serum corticosterone level, neuroinflammation, anxiety, stress, and despair-related responses. To the best of our knowledge, this is the first study to identify lincRNAs and their RNA targets with a putative role in transcriptional regulation during fear extinction in the context of an animal model of PTSD.

Posttraumatic stress disorder and breast cancer: Risk factors and the role of inflammation and endocrine function

A breast cancer diagnosis can be a life-changing and stressful experience that can lead to chronic mental health conditions such as posttraumatic stress disorder (PTSD). Greater than one-third of patients initially diagnosed with PTSD after a diagnosis of breast cancer continue to have persistent or worsening PTSD symptoms after 4 years. An emerging body of literature has indicated several key environmental and biological risk factors for PTSD among survivors of breast cancer. Well-recognized risk factors include having a history of childhood trauma, being nonwhite, obesity, younger age at the time of diagnosis, diagnosis with a higher stage of breast cancer, and short time since treatment. Of the emerging risk factors related to fear circuitry in the brain, 2 pathways of particular importance are the stress-driven activation of inflammatory pathways and the long-term effect of antiendocrine therapies. These central and peripheral responses during and after stress exposure are important because increased fear and anxiety can lead to the maintenance of PTSD and worse patient outcomes. Given the poor outcomes associated with PTSD and the high prevalence of breast cancer in women, more research to identify those women at heightened risk of PTSD after breast cancer is warranted to reduce the number of diagnoses and lessen the negative impact of this chronic mental health condition.

Treatment with a heat-killed preparation of Mycobacterium vaccae after fear conditioning enhances fear extinction in the fear-potentiated startle paradigm

The hygiene hypothesis or "Old Friends" hypothesis proposes that inflammatory diseases are increasing in modern urban societies, due in part to reduced exposure to microorganisms that drive immunoregulatory circuits and a failure to terminate inappropriate inflammatory responses. Inappropriate inflammation is also emerging as a risk factor for anxiety disorders, affective disorders, and trauma-and stressor-related disorders, including posttraumatic stress disorder (PTSD), which is characterized as persistent re-experiencing of the trauma after a traumatic experience. Traumatic experiences can lead to long-lasting fear memories and fear potentiation of the acoustic startle reflex. The acoustic startle reflex is an ethologically relevant reflex and can be potentiated in both humans and rats through Pavlovian conditioning. Mycobacterium vaccae is a soil-derived bacterium with immunoregulatory and anti-inflammatory properties that has been demonstrated to enhance fear extinction in the fear-potentiated startle paradigm when given prior to fear conditioning. To determine if immunization with M. vaccae after fear conditioning also has protective effects, adult male Sprague Dawley rats underwent fear conditioning on days -37 and -36 followed by immunizations (3x), once per week beginning 24 h following fear conditioning, with a heat-killed preparation of M. vaccae NCTC 11659 (0.1 mg, s.c., in 100 µl borate-buffered saline) or vehicle, and, then, 3 weeks following the final immunization, were tested in the fear-potentiated startle paradigm (n = 12 per group). Rats underwent fear extinction training on days 1 through 6 followed by spontaneous recovery 14 days later (day 20). Rats were euthanized on day 21 and brain tissue was sectioned for analysis of Tph2, Htr1a, Slc6a4, Slc22a3, and Crhr2 mRNA expression throughout the brainstem dorsal and median raphe nuclei. Immunization with M. vaccae did not affect fear expression on day 1. However, M. vaccae-immunized rats showed enhanced enhanced within-session fear extinction on day 1 and enhanced between-session fear extinction beginning on day 2, relative to vehicle-immunized controls. Immunization with M. vaccae and fear-potentiated startle had minimal effects on serotonergic gene expression when assessed 42 days after the final immunization. Together with previous studies, these data are consistent with the hypothesis that immunoregulatory strategies, such as immunization with M. vaccae, have potential for both prevention and treatment of trauma- and stressor-related psychiatric disorders.

Stress-Induced Sensitization of Angiotensin II Hypertension Is Reversed by Blockade of Angiotensin-Converting Enzyme or Tumor Necrosis Factor-α

BACKGROUND

Post-traumatic stress disorder (PTSD) is characterized by a disordered stress response and associated with increased cardiovascular disease risk. The present study investigated whether angiotensin (Ang) II-elicited hypertensive response is sensitized in a model of PTSD and whether inhibition of angiotensin-converting enzyme (ACE) or tumor necrosis factor (TNF)-α prior to PTSD blocks this sensitization of Ang II hypertension.

METHODS

The resident-intruder paradigm was used to model PTSD. Each intruder rat (male Sprague-Dawley) was given normal drinking water or was pretreated with either an ACE inhibitor (captopril) or a TNF-α inhibitor (pentoxifylline) in the drinking water for 2 weeks. Subsequently, they were exposed to a different resident (male Long-Evans) for 2 hours on 3 days with each session separated by 1 day and then received a subcutaneous infusion of Ang II for 2 weeks.

RESULTS

The stressed rats had a significantly enhanced hypertensive response to the Ang II infusion (stressed Δ40.2 ± 3.9 mm Hg vs. unstressed Δ20.5 ± 4.5 mm Hg) and an upregulation of mRNA or protein expression of renin-angiotensin system (RAS) and proinflammatory cytokine (PIC) components and of a microglial marker in the lamina terminalis and hypothalamic paraventricular nucleus when compared with unstressed control rats. Both the sensitized hypertensive response and enhanced gene and protein expression were blocked by pretreatment with either ACE (Δ21.3 ± 3.9 mm Hg) or TNF-α inhibitor (Δ21.4 ± 2.6 mm Hg).

CONCLUSIONS

The results indicate that upregulation of the brain RAS and PICs produced by severe stress contributes to traumatic-induced sensitization of hypertensive response to Ang II, and disorders such as PTSD may predispose individuals to development of hypertension.

Understanding Resilience and Preventing and Treating PTSD

Resilience is defined as the dynamic ability to adapt successfully in the face of adversity, trauma, or significant threat. Some of the key early studies of resilience were observational studies in children. They were followed by research in adults, studies testing interventions to promote resilience in different populations, and a recent upsurge of studies on the underlying genomic and neurobiological mechanisms. Neural and molecular studies in preclinical models of resilience are also increasingly identifying active stress adaptations in resilient animals. Knowledge gained from animal and human studies of resilience can be harnessed to develop new preventive interventions to enhance resilience in at-risk populations. Further, treatment interventions focused on enhancing potentially modifiable protective factors that are consistently linked to psychological resilience can enrich currently available treatment interventions for individuals with posttraumatic stress disorder (PTSD). Translating our expanding knowledge of the neurobiology of resilience additionally promises to yield novel therapeutic strategies for treating this disabling condition. This review summarizes the vast field of resilience research spanning genomic, psychosocial, and neurobiological levels, and discusses how findings have led and can lead to new preventive and treatment interventions for PTSD.

Head Transplantation: The Immune System, Phantom Sensations, and the Integrated Mind

The principal focus of this paper is to consider the implications of head and neck transplantation surgery on the issue of personal identity. To this end, it is noted that the immune system has not only been established to impose a level of self-identity on bodily cells, it has also been implicated in mental development and the regulation of mental state. In this it serves as a paradigm for the mind as the product of cephalic and extracephalic systems. The importance of bodily systems in identity is then discussed in relation to phantom tissue syndrome. The data strongly indicate that, even if surgically successful, head and neck transplantation will result in the loss of the continuity of personal identity.

Chronic pain as a human rights issue: setting an agenda for preventative action

Background: Historically, chronic pain has been viewed primarily as a medical issue, and research has been focused on the individual and predominantly on pain sufferers in high-income countries.

Objectives: This article argues the need for a broader understanding of the context of chronic pain and its complex aetiologies and maintenance. It is suggested that the interaction between chronic pain and social context has been inadequately explored.

Methods: A single case study is used of a man living in a violent urban environment in South Africa accessing a pain clinic at a tertiary hospital. Following the case-study approach, as used in the chronic traumatic stress field by Kaminer et al., the case material is utilised to develop an argument for a new research agenda.

Results: Analysis of the case material demonstrates the complex interplay between bodily and psychological experiences, with chronic pain being contextually maintained and exacerbated by very difficult life circumstances, ongoing violence, and marginalisation.

Conclusions: It is suggested that a research agenda be developed which explores the links between chronic pain and ongoing chronic traumatisation in contexts of continuous violence, oppression, and disempowerment – common features of much of the contemporary majority world.

Recent Genetics and Epigenetics Approaches to PTSD

PURPOSE OF REVIEW

Following a life-threatening traumatic exposure, about 10% of those exposed are at considerable risk for developing posttraumatic stress disorder (PTSD), a severe and disabling syndrome characterized by uncontrollable intrusive memories, nightmares, avoidance behaviors, and hyperarousal in addition to impaired cognition and negative emotion symptoms. This review will explore recent genetic and epigenetic approaches to PTSD that explain some of the differential risk following trauma exposure.

RECENT FINDINGS

A substantial portion of the variance explaining differential risk responses to trauma exposure may be explained by differential inherited and acquired genetic and epigenetic risk. This biological risk is complemented by alterations in the functional regulation of genes via environmentally induced epigenetic changes, including prior childhood and adult trauma exposure. This review will cover recent findings from large-scale genome-wide association studies as well as newer epigenome-wide studies. We will also discuss future "phenome-wide" studies utilizing electronic medical records as well as targeted genetic studies focusing on mechanistic ways in which specific genetic or epigenetic alterations regulate the biological risk for PTSD.

CRP polymorphisms and DNA methylation of the AIM2 gene influence associations between trauma exposure, PTSD, and C-reactive protein

BACKGROUND

Recent studies have implicated inflammatory processes in the pathophysiology of posttraumatic stress disorder (PTSD). C-reactive protein (CRP) is a widely-used measure of peripheral inflammation, but little is known about the genetic and epigenetic factors that influence blood levels of C-reactive protein (CRP) in individuals with PTSD.

METHODS

Participants were 286 U.S. military veterans of post-9/11 conflicts (57% with current PTSD). Analyses focused on single nucleotide polymorphisms (SNPs) in the CRP gene and DNA methylation at cg10636246 in AIM2-a locus recently linked to CRP levels through results from a large-scale epigenome-wide association study.

RESULTS

PTSD was positively correlated with serum CRP levels with PTSD cases more likely to have CRP levels in the clinically-elevated range compared to those without a PTSD diagnosis. Multivariate analyses that controlled for white blood cell proportions, genetic principal components, age and sex, showed this association to be mediated by methylation at the AIM2 locus. rs3091244, a functional SNP in the CRP promoter region, moderated the association between lifetime trauma exposure and current PTSD severity. Analyses also revealed that the top SNPs from the largest genome-wide association study of CRP conducted to date (rs1205 and rs2794520) significantly interacted with PTSD to influence CRP levels.

CONCLUSIONS

These findings provide new insights into genetic and epigenetic mechanisms of inflammatory processes in the pathophysiology of PTSD and point to new directions for biomarker identification and treatment development for patients with PTSD.

Mast Cell Activation in Brain Injury, Stress, and Post-traumatic Stress Disorder and Alzheimer's Disease Pathogenesis

Mast cells are localized throughout the body and mediate allergic, immune, and inflammatory reactions. They are heterogeneous, tissue-resident, long-lived, and granulated cells. Mast cells increase their numbers in specific site in the body by proliferation, increased recruitment, increased survival, and increased rate of maturation from its progenitors. Mast cells are implicated in brain injuries, neuropsychiatric disorders, stress, neuroinflammation, and neurodegeneration. Brain mast cells are the first responders before microglia in the brain injuries since mast cells can release prestored mediators. Mast cells also can detect amyloid plaque formation during Alzheimer's disease (AD) pathogenesis. Stress conditions activate mast cells to release prestored and newly synthesized inflammatory mediators and induce increased blood-brain barrier permeability, recruitment of immune and inflammatory cells into the brain and neuroinflammation. Stress induces the release of corticotropin-releasing hormone (CRH) from paraventricular nucleus of hypothalamus and mast cells. CRH activates glial cells and mast cells through CRH receptors and releases neuroinflammatory mediators. Stress also increases proinflammatory mediator release in the peripheral systems that can induce and augment neuroinflammation. Post-traumatic stress disorder (PTSD) is a traumatic-chronic stress related mental dysfunction. Currently there is no specific therapy to treat PTSD since its disease mechanisms are not yet clearly understood. Moreover, recent reports indicate that PTSD could induce and augment neuroinflammation and neurodegeneration in the pathogenesis of neurodegenerative diseases. Mast cells play a crucial role in the peripheral inflammation as well as in neuroinflammation due to brain injuries, stress, depression, and PTSD. Therefore, mast cells activation in brain injury, stress, and PTSD may accelerate the pathogenesis of neuroinflammatory and neurodegenerative diseases including AD. This review focusses on how mast cells in brain injuries, stress, and PTSD may promote the pathogenesis of AD. We suggest that inhibition of mast cells activation and brain cells associated inflammatory pathways in the brain injuries, stress, and PTSD can be explored as a new therapeutic target to delay or prevent the pathogenesis and severity of AD.