Environmental stress is among the most important contributors to increased susceptibility to develop psychiatric disorders. While it is well known that acute environmental stress alters gene expression, the molecular mechanisms underlying these changes remain largely unknown. 5-hydroxymethylcytosine (5hmC) is a novel environmentally sensitive epigenetic modification that is highly enriched in neurons and is associated with active neuronal transcription. Recently, we reported a genome-wide disruption of hippocampal 5hmC in male mice following acute stress that was correlated to altered transcript levels of genes in known stress related pathways. Since sex-specific endocrine mechanisms respond to environmental stimulus by altering the neuronal epigenome, we examined the genome-wide profile of hippocampal 5hmC in female mice following exposure to acute stress and identified 363 differentially hydroxymethylated regions (DhMRs) linked to known (e.g., Nr3c1 and Ntrk2) and potentially novel genes associated with stress response and psychiatric disorders. Integration of hippocampal expression data from the same female mice found stress-related hydroxymethylation correlated to altered transcript levels. Finally, characterization of stress-induced sex-specific 5hmC profiles in the hippocampus revealed 778 sex-specific acute stress-induced DhMRs some of which were correlated to altered transcript levels that produce sex-specific isoforms in response to stress. Together, the alterations in 5hmC presented here provide a possible molecular mechanism for the adaptive sex-specific response to stress that may augment the design of novel therapeutic agents that will have optimal effectiveness in each sex.
Background: While electroconvulsive therapy (ECT) is the most effective treatment for major depression (major depressive disorder [MDD]), deep brain stimulation (DBS) has shown efficacy in patients who have not received benefit from ECT. Studies of DBS are small, and a better understanding of which eligibility criteria lead to exclusion may help achieve a more appropriate balance between scientific rigor and generalizability in future trials.We assessed the rate and reasons for exclusion from a study of DBS for treatment-resistant MDD and bipolar type II (BPII) depression.
Methods: One thousand ninety-eight adults were screened for a study of DBS for MDD or BPII. Reasons for exclusion were documented. Descriptive statistics were calculated for each reason for exclusion for the entire sample as well as the self-reported MDD and BPII subgroups.
Results: Ninety-eight percent (98%) of patients screened were excluded. Exclusion due to lack of interest or inability to relocate to the study sitewas high (41%). Following this, primary reasons for exclusion were lack of prior ECT and presence of psychiatric/general medical comorbidity. Patients with MDD were more likely to be excluded because of inadequate ECT, whereas patients with BPII depression were more likely to be excluded for comorbid psychiatric diagnoses and not meeting minimum severity criteria.
Conclusions: A surprisingly high number of potential participants were excluded because of lack of adequate ECT. This suggests that many patients self-identifying as "treatment resistant" have not truly exhausted available, evidence-based treatments. Overall exclusion rate was high, with key differences in exclusion reasons between the MDD and BPII subgroups. These findings can inform design of future clinical trials for treatment-resistant unipolar and bipolar depression.
Crosstalk between inflammatory pathways and neurocircuits in the brain can lead to behavioural responses, such as avoidance and alarm, that are likely to have provided early humans with an evolutionary advantage in their interactions with pathogens and predators. However, in modern times, such interactions between inflammation and the brain appear to drive the development of depression and may contribute to non-responsiveness to current antidepressant therapies. Recent data have elucidated the mechanisms by which the innate and adaptive immune systems interact with neurotransmitters and neurocircuits to influence the risk for depression. Here, we detail our current understanding of these pathways and discuss the therapeutic potential of targeting the immune system to treat depression.