Abstract
Depression in astronauts is one of the consequences of space flight effects, negatively impacting their work performances. Unfortunately, the underlying molecular mechanisms in space flight-induced depression are still unknown; however, various neuropsychiatric disorders reported that overexpressed NR2B-PSD-95-nNOS complex in the brain triggers various pathological pathways, and inhibiting NR2B-PSD-95-nNOS complex asserts antidepressant effects. Through our in silico analysis, we found that epigenetic regulator miR-445-3p targets PSD-95 and is hypothesized to down-regulate NR2B-PSD-95-nNOS complex to prevent neuronal damage associated with depression. Therefore, the present study is aimed to determine the novel insight of the miR-455-3p against the NR2B-PSD-95-nNOS complex in the neurobiology of space flight-induced depressive behavior. Using a simulated space environment complex model (SCSE) for 21 days, we induced depressive behavior in rats to analyze miR-455-3p expression and NR2B-PSD-95-nNOS complex in the cortex and hippocampus of the SCSE depressed rats through qRT-PCR and western blot analysis. Further, an in vitro microgravity model using rat hippocampus cell lines (RHNC) was utilized to identify the independent role of miR-455-3p on (1) NR2B-PSD-95-nNOS complex and TrKB-BDNF proteins, (2) oxidative stress, (3) nitric oxide level, (4) inflammatory cytokines, (5) mitochondrial biogenesis/ dynamics, and (6) cell survival. Our results showed that miR-455-3p regulates NR2B-PSD-95-nNOS complex in the SCSE depressed rats in opposite ways, with the cortex revealing a higher level of miR-455-3p and low-level NR2B-PSD-95-nNOS complex and the hippocampus showing down-regulated miR-455-3p and up-regulated NR2B-PSD-95-nNOS complex, indicating a region-specific change in the miR-455-3p and NR2B-PSD-95-nNOS complex in the SCSE depressed rats. Further RHNC results also confirmed down-regulated miR-455-3p and up-regulated NR2B-PSD-95-nNOS complex expression, similar to the findings in the hippocampus of SCSE rats, suggesting that microgravity influences miR-455-3p and associated changes. Additional investigations revealed that miR-455-3p targets PSD-95 and co-regulates NR2B-PSD-95-nNOS complex along with TrkB-BDNF signaling and exert protective effects against NR2B-PSD-95-nNOS complex, oxidative stress, nitric oxide, inflammatory cytokines, and mitochondrial defects, suggesting a valuable biomarker for devising depressive disorders.