E. et al., Soc. Neurosci. Abstr. 219.01, 2011; Pfau, M.L. et al., Soc. Neurosci. Abstr. 541.26, 2013). Further mining of these data sets may reveal promising patterns and candidate genes for further understanding of sex-dependent stress resilience. In addition to the activating effects of sex hormones on stress circuitry in adulthood, prenatal perturbations can exert organizational effects on the brain that dictate sex differences in adult stress response. Mueller and Bale (2008) reported increased depression-like

behavior in male, but not female, mice whose mothers had been exposed to CUS during early pregnancy. Male mice displayed elevated amygdala CRF expression and decreased hippocampal GR expression that corresponded with epigenetic alterations—reduced Crizotinib purchase methylation of the CRF promoter and enhanced methylation of the 17 exon of the GR promoter. The authors identified sex differences in prenatal stress-induced click here placental gene expression profiles, particularly differences in the methylation maintenance enzyme Dnmt1, as potential developmental mechanisms underlying adult phenotypes. Moreover, a recent study showed that stress-induced pro-inflammatory placental gene expression contributes to enhanced male susceptibility to prenatal stress ( Bronson and Bale, 2014). Maternal nonsteroidal anti-inflammatory drug treatment reversed the stress-induced increase in placental Interleukin 6 (IL-6)

expression and ameliorated locomotor hyperactivity (a behavioral indicator of dopaminergic dysfunction) next in prenatally stressed adult male mice. While much work has focused on the maternal environment, an interesting study by Rodgers et al. (2013) demonstrated a role for paternal stress in male offspring susceptibility. Adult male mice sired by fathers exposed to CUS in puberty or adulthood displayed HPA axis hypoactivity, which

correlated with changes in paternal sperm microRNA expression profiles. Together these results highlight the complex interactions between genetics and environment in stress resilience. The interaction of stress and the immune system has become a major focus of psychiatric research since the introduction of the “cytokine hypothesis of depression” in the 1990s (Maes et al., 2009). The hypothesis asserts that many of the central abnormalities observed in depression—enhanced HPA axis activity, neurodegeneration, decreased neurogenesis, oxidative stress, and serotonergic signaling dysfunction—are at least in part due to peripheral inflammatory cytokines released in response to external, psychological stressors and internal stressors such as chronic disease and “leaky gut. A growing literature explores the connection between stress, proinflammatory cytokines, and depression and anxiety-like behavior in both humans and animals. Cytokines are soluble proteins that are released at a site of infection by leukocytes.