Genomic factors underlying sex differences in trauma-related disorders

Epigenetic control of memory formation

A neuron's suitability to participate in a memory trace is modulated by its epigenetic state.

Ketamine ameliorates post-traumatic social avoidance by erasing the traumatic memory encoded in VTA-innervated BLA engram cells

Erasing traumatic memory during memory reconsolidation is a promising retrieval-extinction strategy for post-traumatic stress disorder (PTSD). Here, we developed an acute social defeat stress (SDS) mouse model with short-term and re-exposure-evoked long-term social avoidance. SDS-associated traumatic memories were identified to be stored in basolateral amygdala (BLA) engram cells. A single intraperitoneal administration of subanesthetic-dose ketamine within, but not beyond, the re-exposure time window significantly alleviates SDS-induced social avoidance, which reduces the activity and quantity of reactivated BLA engram cells. Furthermore, activation or inhibition of dopaminergic projections from the ventral tegmental area to the BLA effectively mimics or blocks the therapeutic effect of re-exposure with ketamine and is dopamine D2 receptor dependent. Single-cell RNA sequencing reveals that re-exposure with ketamine triggered significant changes in memory-related pathways in the BLA. Together, our research advances the understanding of how ketamine mitigates PTSD symptoms and offers promising avenues for developing more effective treatments for trauma-related disorders.

Moral injury appraisals and dissociation: Associations in a sample of trauma-exposed community members

Appraisal of trauma is a critical factor in the development of impairing post-traumatic stress symptoms, such as dissociation. Individuals may appraise trauma as morally injurious (i.e., moral injury exposure [MIE]) and experience subsequent moral distress related to this exposure (i.e., moral injury distress [MID]). To date, however, investigation into the relations between moral injury appraisals and dissociation has been limited, particularly within community populations. This study investigated MIE and MID in relation to six facets of dissociation (disengagement, depersonalization, derealization, memory disturbances, emotional constriction, identity dissociation) in a sample of trauma-exposed community members (n = 177, 58.2% Black, 89.3% female) recruited from a public hospital and/or community advertisements. Participants completed measures assessing trauma exposure, MIE, MID, dissociation, and posttraumatic stress disorder (PTSD) symptoms. Partial correlation analyses revealed that after controlling for PTSD symptoms, MIE was correlated with disengagement, r = .23, p ≤ .025, and depersonalization, r = .25, p ≤ .001, and MID was correlated with depersonalization, r = .19, p ≤ .025. Sex moderated each association, with stronger associations observed for female participants. Findings suggest that moral injury appraisals are linked to more severe dissociative symptoms among female civilians, and as such, may need to be specifically targeted in empirically supported treatments.

Methyl-CpG binding protein 2 expression is associated with symptom severity in patients with PTSD in a sex-dependent manner

Traumatic events may lead to post-traumatic stress disorder (PTSD), with higher prevalence in women. Adverse childhood experiences (ACE) increase PTSD risk in adulthood. Epigenetic mechanisms play important roles in PTSD pathogenesis and a mutation in the methyl-CpG binding protein 2 (MECP2) in mice provide susceptibility to PTSD-like alterations, with sex-dependent biological signatures. The present study examined whether the increased risk of PTSD associated with ACE exposure is accompanied by reduced MECP2 blood levels in humans, with an influence of sex. MECP2 mRNA levels were analyzed in the blood of 132 subjects (58 women). Participants were interviewed to assess PTSD symptomatology, and asked to retrospectively report ACE. Among trauma-exposed women, MECP2 downregulation was associated with the intensification of PTSD symptoms linked to ACE exposure. MECP2 expression emerges as a potential contributor to post-trauma pathophysiology fostering novel studies on the molecular mechanisms underlying its potential sex-dependent role in PTSD onset and progression.

Sex differences in fear responses: Neural circuits

Women have increased vulnerability to PTSD and anxiety disorders compared to men. Understanding the neurobiological underpinnings of these disorders is critical for identifying risk factors and developing appropriate sex-specific interventions. Despite the clear clinical relevance of an examination of sex differences in fear responses, the vast majority of pre-clinical research on fear learning and memory formation has exclusively used male animals. This review highlights sex differences in context and cued fear conditioning, fear extinction and fear generalization with a focus on the neural circuits underlying these behaviors in rodents. There are mixed reports of behavioral sex differences in context and cued fear conditioning paradigms, which can depend upon the behavioral indices of fear. However, there is greater evidence of differential activation of the hippocampus, amygdalar nuclei and the prefrontal cortical regions in male and female rodents during context and cued fear conditioning. The bed nucleus of the stria terminalis (BNST), a sexually dimorphic structure, is of particular interest as it differentially contributes to fear responses in males and females. In addition, while the influence of the estrous cycle on different phases of fear conditioning is delineated, the clearest modulatory effect of estrogen is on fear extinction processes. Examining the variability in neural responses and behavior in both sexes should increase our understanding of how that variability contributes to the neurobiology of affective disorders. This article is part of the Special Issue on 'Fear, anxiety and PTSD'.

The Molecular Relationship between Stress and Insomnia

The bi-directional relationship between sleep and stress has been actively researched as sleep disturbances and stress have become increasingly common in society. Interestingly, the brain and underlying neural circuits important for sleep regulation may respond uniquely to stress that leads to post-traumatic stress disorder (PTSD) and stress that does not. In stress that does not lead to PTSD, the hypothalamic-pituitary-adrenal axis (HPA) pathway is activated normally that results in sympathetic nervous system activation that allows the brain and body to return to baseline functioning. However, exposure to stress that leads to PTSD, causes enhanced negative feedback of this same pathway and results in long-term physiological and psychological changes. In this review, how stress regulates glucocorticoid signaling pathways in brain glial cells called astrocytes, and then mediates stress-induced insomnia are examined. Astrocytes are critical sleep regulatory cells and their connections to sleep and stress due to disturbed glucocorticoid signaling provide a novel mechanism to explain how stress leads to insomnia. This review will examine the interactions of stress neurobiology, astrocytes, sleep, and glucocorticoid signaling pathways and will examine the how stress that leads to PTSD and stress that does not impacts sleep-regulatory processes.