125,126 Interestingly, 5-HT3 receptor variants were initially associated with bipolar disorder, a finding that has been recently replicated in genome-wide association studies.127,128 Epigenetic modulation of serotonin-related genes by early-life stress Rodent and human studies indicate that early-life adversity helps program responsiveness to stressors by inducing long-term epigenetic
modifications in several genes Inhibitors,research,lifescience,medical regulating the HPA axis such as the NR3C1 gene coding for GR.122 The best studied epigenetic marker, with regards to early-life adversity, is DNA methylation of cytosine -guanine dinucleotides. In rodents, prenatal stress129 as well as low maternal care130,131 has been shown to increase
methylation in the NR3C1 promoter region, thereby leading to decreased expression Inhibitors,research,lifescience,medical and function of GR in the hippocampus. In humans, increased NR3C1 methylation in blood cells, cord cells, or in hippocampal postmortem tissue have been observed in individuals exposed to prenatal adversity132,133 or high levels of http://www.selleckchem.com/products/crenolanib-cp-868596.html childhood maltreatment.134-136 In addition, increased NR3C1 methylation was linked to increased stress-induced cortisol reactivity in humans132 and rodents.130,131 To date, few studies Inhibitors,research,lifescience,medical have explored the impact of early-life stress on the methylation status of serotonin-related genes. In humans, methylation
in the promoter region of SERT decreases its expression and this effect is dependent on the Inhibitors,research,lifescience,medical genotype of the serotonin transporter gene-linked polymorphic region (5-HTTLPR).137 The methylation status of SERT was increased in females compared with males138 Inhibitors,research,lifescience,medical and was associated with increased scores for unresolved loss and trauma, a risk factor for psychopathology, in s allele carriers.139 Furthermore, an association between increased SERT methylation and depressive scores was observed in individuals carrying the s allele.140 In a monozygotic twin sample, bullying victimization during childhood was found to be associated with increased SERT methylation and a blunted cortisol response to stress.141 Increased SERT methylation was also associated with childhood sexual abuse and to an increased risk for antisocial behavior in women.142 Relevant to human studies, macaque models of early-life stress indicate that increased SERT methylation medroxyprogesterone is associated with lower SERT expression in the peripheral blood and increased behavioral stress reactivity in infants subjected to early maternal separation143 or in adults exposed during infancy to early-life stress.144 Emerging data suggests that the methylation pattern of other serotonin-related genes could be associated with psychiatric disorders and related to expression levels in the brain.