Search

In order to study the cytoprotective function of colonic heat shock proteins (HSPs) in vivo, the effect of specific preinduction of HSP60 by thyrotropin-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 immunohistochemical analyses before and after TRH administration. Following pretreatment with or without TRH administration, the rats received intrarectal infusion of 5% acetic acid. The colonic mucosal damage was macroscopically evaluated 24 hr after the intrarectal infusion of acetic acid. Expression of HSP60 was significantly increased by TRH administration in the colonic mucosa, whereas 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. The colonic mucosal damage caused by intrarectal infusion of 5% acetic acid was not prevented by preinduction of HSP60. We demonstrated that specific preinduction of HSP60 by TRH administration did not show cytoprotective function in the colonic mucosa, although this protein plays a crucial role for cytoprotection in the pancreatic acinar cells. Our results indicate that the role of HSP60 may be different in each organ with respect to cytoprotection.

It is well documented that gastric mucosa canincrease its resistance to mucosal damage caused byaspirin during repeated long-term administration ofaspirin. However, the underlying mechanism of thisadaptation is not well established. In the present study,we investigated the effect of long-term (chronic)administration of aspirin on expression of heat shockproteins (HSPs), which are known as endogenouscytoprotectants, in rat gastric mucosa. Rats were administeredaspirin (100 mg/kg) daily for up to 20 days. Aftervarious periods of aspirin administration, a high doseof aspirin (250 mg/kg) was administered, and the mucosal damage was assessed. Expression of heat shockproteins (HSPs) in gastric mucosa was evaluated byWestern blot. Intracellular localization of each HSP wasstudied immunohistochemically. ProstaglandinE2 (PGE2) and leukotriene B4(LTB4) levels were also investigated.Long-term aspirin administration resulted in developmentof resistance to aspirin-induced mucosal damage, and theincrease of HSP72 expression correlated with mucosal resistance to aspirin.No significant increase was observed in HSP60 and HSP90levels. Immunohistochemical study showed an increase ofHSP72 in the cytoplasm of mucosal surface cells. The PGE2 level was suppressed and nochange in the level of LTB4 was observed. Itis possible that HSP72 could play important roles ingastric mucosal adaptation when the PGE2level is suppressed by NSAIDs.

Bowel dysfunction such as irritable bowelsyndrome caused by stress is well described. Previousreports suggest that stress is known to cause therelease of endogenous substances such as catecholamine, beta-endorphine, 5-hydroxytryptamine,corticotropin-releasing factor, andthyrotropin-releasing hormone (TRH). However, the roleplayed by these neurohormonal mediators in boweldysfunction under stress conditions is not well known. We investigatedthe influence of water-immersion stress or TRHadministration on the expression of 60-kDa, 72-kDa, and90-kDa heat-shock proteins (HSP60, HSP72, and HSP90, respectively) in rat small intestinal mucosa byWestern blot and immunohistochemical analyses. Thecytoprotective function of preinduced HSPs onexperimentally induced mucosal damage also was studied.In order to investigate the influence ofpreinduction of HSP60 on small intestinal damage, thesmall intestinal lumen was perfused with 1.5% aceticacid 1 ml/min for 15 min with or without pretreatmentwith water-immersion stress or TRH administration.Expression of HSP60 was significantly increased bywater-immersion stress or TRH administration in thesmall intestinal mucosa, whereas HSP72 and HSP90 did not increase. Interestingly, expression of thisprotein showed the biphasic peak pattern afterwater-immersion stress or TRH administration. Each peakwas observed 3-6 hr and 21-24 hr after the initiation of water-immersion stress or TRHadministration. Immunohistochemical study also showed asignificant increment of HSP60 in both the cytoplasm andnuclei of the small intestinal mucosal cells. Nohistopathologic alteration was observed in rat small intestinalmucosa after each treatment. Small intestinal damagecaused by 1.5% acetic acid perfusion was not influencedby preinduction of HSP60. We demonstrated that waterimmersion stress or TRH administrationspecifically induced HSP60, although preinduction ofthis protein did not show a cytoprotective function inthe small intestinal mucosa.

We previously reported that water-immersionstress specifically induced the synthesis of a 60-kDaheat-shock protein (HSP60, chaperonin homolog) inpancreatic cells and preinduction of HSP60 completely prevented development of cerulein-inducedpancreatitis in the rat in an HSP60 quantitativelydependent manner. In order to study the cytoprotectivefunction of a 72-kDa heat-shock protein (HSP72,stress-inducible hsp70), the effect of specific preinduction ofHSP72 by hyperthermia on cerulein-induced pancreatitiswas investigated and compared with the effect ofpreinduction of HSP60 in this study. Expression of HSP60 and HSP72 in the pancreas wasinvestigated by immunoblot before and after waterimmersion or hyperthermia. Following pretreatment withwater-immersion stress or hyperthermia, the rats wereinjected with cerulein (40 μg/kg, intraperitoneally).The pancreas wet weight and serum amylase concentrationwere measured before and after cerulein injection.Hyperthermia (42.5°C, 20 min) specifically induced HSP72 in the pancreas. The synthesis of HSP60was specifically induced by water-immersion stress inthe pancreas. Cerulein-induced pancreatitis was clearlyprevented by specific preinduction of HSP60 by water-immersion stress. However, preinductionof HSP72 by hyperthermia had no preventive effect oncerulein-induced pancreatitis. Our findings suggest thatHSP60 and HSP72 have distinct functions in the pancreas, and their induction mechanisms arealso different in vivo. These results could be importantfor understanding the mechanism of “adaptivecytoprotection” in the pancreas mediated byheat-shock proteins.

In order to study the cytoprotective function ofheat shock proteins (HSPs) in vivo, the effect ofpreinduction of HSPs by hyperthermia on aceticacid-induced colitis was investigated. Expression of60-kDa, 72-kDa, and 90-kDa heat shock proteins (HSP60,HSP72, and HSP90, respectively) in rat colonic mucosawas investigated by Western blot analysis andimmunohistochemical study before and after hyperthermia. Following pretreatment with or withouthyperthermia, the rats received intrarectal infusion ofvarious doses of acetic acid. The colonic mucosal damagewas evaluated by macroscopic and microscopic assessments 24 hr after the intrarectal infusion of aceticacid. Expression of HSPs was significantly increased byhyperthermia in rat colonic mucosa. Immunohistochemicalstudy also showed the increments of HSPs in the colonic mucosal cells after hyperthermia.Acetic acid-induced colitis was dramatically preventedby pretreatment with hyperthermia when HSP72 and HSP90were preinduced. On the other hand, induction of HSP60 did not correlate with mucosalprotection. Our findings suggest that HSP72 and HSP90may have cytoprotective function against aceticacid-induced mucosal damage. These results may beimportant for understanding the mechanism of“adaptive cytoprotection” mediated byHSPs.

Heat shock proteins are ubiquitous intracellular proteins induced by various physiological stress-related events. A 72-kDa heat shock protein (HSP72) has been reported to be an endogenous cytoprotectant in variety of cells in vitro. In order to study the cytoprotective function of HSP72 in the liver, the effect of preinduction of HSP72 in rat liver by systemic hyperthermia on thioacetamide-induced hepatic injury was investigated in this study. Expression of HSP72 in the liver was investigated by immunoblot and densitometric analysis. Rats were injected with thioacetamide (100 mg/kg, subcutaneously) with or without preinduction of HSP72 by hyperthermia. Serum AST and ALT concentrations were measured before and after thioacetamide injection in both group. Histologic alteration of the liver was evaluated also. Systemic hyperthermia (42.5 degrees C, 20 min) significantly induced HSP72 in the liver. Thioacetamide-induced hepatic injury was clearly prevented by preinduction of HSP72 by hyperthermia. Prevention of hepatocyte damage was more clear in the area around central veins where HSP72 induction was apparent. Our findings might suggest that HSP72 has an important function in the liver with respect to cytoprotection. These results might be important for understanding the mechanism of "adaptive cytoprotection" in the liver mediated by the function of heat shock proteins as "molecular chaperons" as reported in vitro.

We investigated the expression and changes in the intracellular localization of a 72-kDa heat shock protein (HSP72) in rat gastric pyloric and fundic mucosa before and after water-immersion stress. Severe mucosal damage was found in the fundic mucosal area of the stomach after this stress. However, no mucosal lesion developed in the pyloric mucosal area. HSP72 in both the soluble and insoluble fractions of the pyloric and the fundic mucosal areas was significantly increased after water-immersion stress, peaking 6 h after the initiation of the stress. The increase in HSP72 was more significant in the pyloric mucosal area than in the fundic mucosal area under both normal and stress conditions. The increase of HSP72 in the pyloric mucosal cells occurred prior to the formation of the mucosal lesions, whereas the increase of HSP72 in the fundic mucosal cells was observed after ulcer formation. An immunohistochemical study showed that HSP72 was constitutively expressed in the cytoplasm of the gastric mucosal cells, and that the intranuclear induction of HSP72 was remarkably intense in the pyloric mucosal cells, especially in the proliferative zone, compared with the fundic mucosal cells. Our results may suggest that HSP72 has an important cytoprotective function in gastric mucosal cells and that there is a “biophysical” difference between pyloric and the fundic mucosal cells.

Bowel dysfunction such as irritable bowel syndrome caused by stress is well described. Previous reports suggest that 5-hydroxytryptamine (5-HT) mediates alteration of bowel motility. In this study, the effects of water-immersion stress and the administration of 5-HT on the expression of a 60-kDa heat shock protein (HSP60) in rat colonic mucosa were investigated. The effect of YM-060, a 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, on the expression of this protein was also studied. Water-immersion stress and the administration of 5-HT induced synthesis of HSP60 in rat colonic mucosa. The induction of HSP60 and the number of defecations were clearly inhibited by the oral administration of YM-060. Our results suggest that the induction of HSP60 in rat colonic mucosa by water-immersion stress may be associated with gastrointestinal motility mediated by 5-HT, especially via 5-HT3 receptors.

Many recent studies have shown the importance of heat shock proteins (HSPs) for the survival of cells under stress conditions, t'2 The dramatic induction of the synthesis of the 70-kDa heat shock protein (HSP70) family has been demonstrated during periods of stress in vitro. 3 In cultured pancreatic islet cells, HSP70 is induced during prolonged exposure to interleukin 1~. 4 It has also been reported that the synthesis of a 60kDa heat shock protein (HSP60) is induced by waterimmersion stress in vivo, and that pre-induction of HSP60 completely prevents caerulein-induced acute pancreatitis, s In this study, we investigated the influence of systemic hyperthermia upon the expression of a HSP60 and a HSP72 in the rat pancreas.