Unfolded protein response and associated alterations in toll-like receptor expression and interaction in the hippocampus of restraint rats

Abstract

Recent evidence suggests that the cellular response to stress often elicits the unfolded protein response (UPR), which has an active role in major depression in emotionally relevant regions of the brain, such as the hippocampus. Much of the UPR activity has been found to be coalesced with the pro-inflammatory environment of the depressed brain. Specifically, downstream transcriptions of pro-inflammatory cytokines and increased regulation of candidate inflammatory mediators, such as toll-like receptors (TLRs), are promoted by the UPR. The present study examined the hippocampus associated expression profile of Tlr genes and their interaction with the UPR chaperone GRP94 in stress-induced rodent model of depression (restraint stress model). Also, the expression status of UPR related genes was evaluated in hippocampus using the same model. mRNA and protein levels of Tlr and UPR associated genes were examined by qRT-PCR and Western blot, respectively. Co-immunoprecipitation (Co-IP) method was used to determine the direct interaction between TLRs with GRP94 in depressed rat brain. The results showed that both UPR (Xbp-1, its spliced variant sXbp-1, Atf-6, Chop, and Grp94) and Tlr (2, 3, 4, 7 and 9) genes were significantly upregulated in the hippocampi of rats who were exposed to restraint stress. Similar upregulation was observed in the protein levels of the above-mentioned TLRs and the UPR chaperone protein GRP94 as well as total and phosphorylated forms of sensor proteins IRE1α and PERK. Further, a significantly increased interaction was observed between GRP94 and the activated TLR proteins. Since, increased inflammatory activity in vulnerable areas like hippocampus is coherently associated with depressed brain; our present data suggest that the UPR may be an integral part of increased activity of inflammatory regulations in depression.

Molecular pathology associated with altered synaptic transcriptome in the dorsolateral prefrontal cortex of depressed subjects

“…IL-6 and TNF-α are also involved in the induction of indoleamine 2,3-dioxygenase, which depletes tryptophan and induces depression 71 , 72 . Recently, we reported that the pharmacological manipulation of cellular stress pathways can induce depression phenotype in rats, which involved TNF-α, NF-κB, and TLRs 73 . Our findings of GR signaling along with immune response mediated through differentially regulated synaptic genes suggest that they may, either independently or in concert, be playing a critical role in compromised immune functions and may be responsible for the development of depressive behavior.…”

GABAA Receptor Subunit Transcriptional Regulation, Expression Organization, and Mediated Calmodulin Signaling in Prefrontal Cortex of Rats Showing Testosterone-Mediated Impulsive Behavior

“…All samples had 260/280 ratio >1.8 and demonstrated 28S:18S rRNA ratio of 2:1 on agarose gel. The single-stranded cDNA was prepared following the previously described method (Timberlake et al, 2018). Following the preparation of mRNA specific first strand cDNA, relative transcript abundance of coding genes was measured with quantitative real-time PCR (Stratagene MxPro3005, La Jolla, CA, United States) method.…”

Chronic Testosterone Increases Impulsivity and Influences the Transcriptional Activity of the Alpha-2A Adrenergic Receptor Signaling Pathway in Rat Brain

“…The single-stranded cDNA was prepared as described previously [28]. Following the preparation of mRNA specific first strand cDNA, 1 μg total RNA was reverse transcribed using M-MLV Reverse Transcriptase (Invitrogen, NY, USA) and oligo (dT) primer.…”