The Effect Of Peritoneal Lavage With 0.9% Saline At 42℃ On The Intrapancreatic Induction Of HSP70 And The Cerulein-induced Acute Pancreatitis In Rats

Background and aims:Heat shock proteins are a set of proteins ubiquitously expressed among prokaryotic and eucaryotic organisms,which are highly conserved and cytoprotective,playing a regulative role in the growth, development,differentiation and apoptosis of cells.To maintain the normal morphology and function of cells,HSPs can be induced under variety of stresses, such as inflammation,ischemia,neoplasms,especially hyperthemia.Recent studies have indicated that prior thermal stress(hot-water immersion at 42℃or heated by heating pad),cold-water immersion(23℃) or medication(isoprenaline, sodium arsenite or BRX-220) pretreatment cause upregulation of HSP70 and/or HSP60 expression in pancreas and protect against cerulein,sodium taurocholate or arginine induced acute pancreatitis(AP) in rats or mice,decreasing the serum amylase and proinflammatory cytokines TNF-α,IL-1 and IL-6 levels,and ameliorating the morphologic damages related to AP.However,some researches have showed that preinduction of HSP70 has no significant preventive effect on AP.So far,the protective effect of HSP70 expression on AP hasn't been definitely concluded.Moreover,the thermal stresses and toxic substances mentioned above are not feasible options for HSPs induction in a clinical setting.The purpose of our study is to investigate the effect of peritoneal lavage with 0.9%saline at 42℃on the preinduction of HSP70 in pancreas,its protective role in the cerulein-induced AP in rats and potential mechanisms.Methods:Male Wistar rats weighting about 250g were divided into seven groups randomly.Rats in group A(n=6) were sacrificed by administration of a lethal intraperitoneal dose of pentobarbital,12 hours after sham operation.Pancreas samples were obtained for the measurement of HSP70 level by western blot.Rats in group B were randomly assigned to six subgroups(B1-B6),6 in each subgroup. Peritoneal lavage with 0.9%saline at 42℃for 30 minutes was performed on rats in B1-B6 subgroups,which were sacrificed 0,3,6,12,24 and 36 hours after peritoneal lavage respectively.Pancreas samples in these subgroups were obtained for the measurement of HSP70 levels by western blot.Rats in group D(n=6) and E(n=6) were intraperitoneally injected with cerulein(20ug/kg)four times at a one-hour interval alter being fasted for 12 hours.Then they were killed 6 and 12 hours after the last injection respectively.Rats in group C(n=6) received comparable injections of saline and were killed 6 hours after the last injection. Rats in group F(n=6) and G(n=6) received prior peritoneal lavage as group B.12 hours after peritoneal lavage,they were intraperitoneally injected with cerulein (20ug/kg) four times at a one-hour interval,then sacrificed 6 and 12 hours after the last injection respectively.Serum samples and pancreas tissues were obtained from the five groups(groupC,D,E,F,and G) for measurement of serum amylase, TNF-α,IL-6,TAP levels and histomorphologic damages.Results:Compared to group A,the intrapancreatic expression of HSP70 in group B was upregulated significantly.HSP70 expression was increased gradually from 0 to 12 hours after peritoneal lavage,reaching a peak 12 hours after peritoneal lavage.After that,the expression began to decrease gradually.Compared to group C,serum amylase,TNF-α,IL-6 and TAP levels were increased significantly with obvious histomorphologic damages(edema,acinar necrosis,inflammation, hemorrhage and fat necrosis) in group D and E.In group F,the serum amylase, TNF-α.IL-6,TAP levels and histomorphologic damages was reduced significantly compared to group D.In group G,only serum IL-6 concentration and part of the histomorphologic damages were ameliorated compared to group E. There was no significant difference of the serum TAP level among the five groups (groupC,D,E,F,and G).Conclusions:Peritoneal lavage with 0.9%saline at 42℃upregulated the HSP70 expression significantly in pancreas of rats.HSP70 expression was increased 3 hours after peritoneal lavage and reached a peak 12 hours after peritoneal lavage. Prior peritoneal lavage with 0.9%saline at 42℃protected against ceruleininduced AP in rats,reducing serum amylase,TNF-α,IL-6 levels and ameliorating histomorphologic damages.The mechanism of the protective effect was speculated to be related to the inhibition of proinflammatory cytokines synthesis during AP.Induction of HSP70 may play a critical role in this inhibition effect.