Heat shock factor 1 regulates the expression of the TRPV1 gene in the rat preoptic-anterior hypothalamus area during lipopolysaccharide-induced fever

摘要

The TRPV1 cation channel is a member of the thermo-TRP family of ionic channels activated by noxious heat and various endogenous mediators. Expression of TRPV1 is widespread and includes hypothalamic neurons. The preoptic-anterior hypothalamus area (PO/AH) are required for regulation of body temperature, suggesting that resident thermosensitive TRPV1 channels may be involved in thermoregulation. Heat shock factor 1 (HSF1) is a ubiquitous heat-sensitive transcription factor that co-ordinates the genomic response to noxious heat, but it is not known whether TRPV1 expression is part of this adaptive mechanism. We therefore investigated whether HSF1 regulates TRPV1 transcription in response to lipopolysacharide (LPS)-induced fever in rats. Expression of TRPV1 and nuclear translocation of HSF1 were transiently upregulated during LPS-induced fever, with temporal profiles that mirrored the rise and fall in body temperature. We used a series of luciferase reporter vectors encoding different spans of the TRPV1 gene 5′-flanking region to identify possible HSF1-binding sites. Reporter assays in transfected PC12 cells demonstrated that only TRPV1 promoters with the -1160 to -821 region drove reporter expression in response to heat shock. This region contains one putative heat shock-responsive element (HSE) for HSF1 binding at -919 to -910. Site-directed mutagenesis of this HSE abrogated reporter activity in response to heat shock, indicating that -919 to -910 contains the specific HSF1-binding sequence. In the PO/AH, electrophoretic mobility shift assay and chromatin immunoprecipitation assay analyses demonstrated that HSF1 is recruited to the HSE of the TRPV1 gene in PO/AH cells during LPS-induced fever, resulting in enhanced TRPV1 expression. Based on these findings, we conclude that HSF1 regulates TRPV1 gene expression in PO/AH of rats with LPS-induced fever.