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Estrogen-dependent association of HDAC4 with fear in female mice and women with PTSD.

ABSTRACT: Women are at increased risk of developing post-traumatic stress disorder (PTSD) following a traumatic event. Recent studies suggest that this may be mediated, in part, by circulating estrogen levels. This study evaluated the hypothesis that individual variation in response to estrogen levels contributes to fear regulation and PTSD risk in women. We evaluated DNA methylation from blood of female participants in the Grady Trauma Project and found that serum estradiol levels associates with DNA methylation across the genome. For genes expressed in blood, we examined the association between each CpG site and PTSD diagnosis using linear models that adjusted for cell proportions and age. After multiple test correction, PTSD associated with methylation of CpG sites in the HDAC4 gene, which encodes histone deacetylase 4, and is involved in long-term memory formation and behavior. DNA methylation of HDAC4 CpG sites were tagged by a nearby single-nucleotide polymorphism (rs7570903), which also associated with HDAC4 expression, fear-potentiated startle and resting-state functional connectivity of the amygdala in traumatized humans. Using auditory Pavlovian fear conditioning in a rodent model, we examined the regulation of Hdac4 in the amygdala of ovariectomized (OVX) female mice. Hdac4 messenger RNA levels were higher in the amygdala 2 h after tone-shock presentations, compared with OVX-homecage control females. In naturally cycling females, tone-shock presentations increased Hdac4 expression relative to homecage controls for metestrous (low estrogen) but not the proestrous (high estrogen) group. Together, these results support an estrogenic influence of HDAC4 regulation and expression that may contribute to PTSD in women.

SUBMITTER: Maddox SA

PROVIDER: S-EPMC5513798 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:OBJECTIVE:Heightened generalization of fear from an aversively reinforced conditioned stimulus (CS+, a conditioned danger cue) to resembling stimuli is widely accepted as a pathogenic marker of posttraumatic stress disorder (PTSD). Indeed, a distress response to benign stimuli that "resemble" aspects of the trauma is a central feature of the disorder. To date, the link between overgeneralization of conditioned fear and PTSD derives largely from clinical observations, with limited empirical work on the subject. This represents the first effort to examine behavioral and brain indices of generalized conditioned fear in PTSD using systematic methods developed in animals known as generalization gradients: the gradual decline in conditioned responding as the presented stimulus gradually differentiates from CS+. METHOD:Gradients of conditioned fear generalization were assessed using functional MRI and behavioral measures in U.S. combat veterans who served in Iraq or Afghanistan and had PTSD (N=26), subthreshold PTSD (N=19), or no PTSD (referred to as trauma control subjects) (N=17). Presented stimuli included rings of graded size, with extreme sizes serving as CS+ (paired with shock) and as a nonreinforced conditioned stimulus (CS-, a conditioned safety cue), and with intermediate sizes forming a continuum of similarity between CS+ and CS-. Generalization gradients were assessed as response slopes from CS+, through intermediate ring sizes, to CS-, with less steep slopes indicative of stronger generalization. RESULTS:Relative to trauma control subjects, PTSD patients showed stronger conditioned generalization, as evidenced by less steep generalization gradients in both behavioral risk ratings and brain responses in the left and right anterior insula, left ventral hippocampus, dorsolateral and dorsomedial prefrontal cortex, and caudate nucleus. Severity of PTSD symptoms across the three study groups was positively correlated with levels of generalization at two such loci: the right anterior insula and left ventral hippocampus. CONCLUSIONS:The results point to evidence of brain-based markers of overgeneralized fear conditioning related to PTSD. These findings provide further understanding of a central yet understudied symptom of trauma-related psychopathology.

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Estrogen-dependent association of HDAC4 with fear in female mice and women with PTSD.

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