Specific preinduction of 60-kDa heat shock protein (chaperonin homolog) byTRH does not protect colonic mucosa against acetic acid-induced lesion in rats

In order to study the cytoprotective function of colonic heat shock protein s (HSPs) in vivo, the effect of specific preinduction of HSP60 by thyrotrop in-releasing hormone (TRH) administration on the development of acetic acid -induced colonic mucosal lesion was investigated. Expression of 60-kDa, 72- kDa, and 90-kDa heat shock proteins (HSP60, HSP72, and HSP90, respectively) in rat colonic mucosa was investigated by western blot and immunohistochem ical analyses before and after TRH administration Following pretreatment wi th or without TRH administration, the rats received intrarectal infusion of 5% acetic acid. The colonic mucosal damage was macroscopically evaluated 2 4 hr after the intrarectal infusion of acetic acid. Expression of HSP60 was significantly increased by TRH administration in the colonic mucosa, where as HSP72 and HSP90 did not increase. Immunohistochemical study also showed a significant increase in HSP60 in colonic mucosal cells, especially at the surface of the colonic mucosa after TRH administration. No histopathologic alteration was observed in the colonic mucosa after TRH administration. Th e colonic mucosal damage caused by intrarectal infusion of 5% acetic acid w as not prevented by preinduction of HSP60. We demonstrated that specific pr einduction of HSP60 by TRH administration did not show cytoprotective funct ion in the colonic mucosa, although this protein plays a crucial role for c ytoprotection in the pancreatic acinar cells. Our results indicate that the role of HSP60 may be different in each organ with respect to cytoprotectio n.