热休克预处理对严重烧伤大鼠胃黏膜的保护作用及机制

目的观察热休克预处理（HS）对严重烧伤大鼠胃黏膜热休克蛋白（HSP）60、HSP70表达及线粒体超氧化物歧化酶（SOD）、细胞色素氧化酶（CCO）活性的影响，探讨HS对严重烧伤大鼠胃黏膜的保护作用及机制。方法将Wistar大鼠随机分为烧伤组（40只）：烧伤后即制作急性胃黏膜损伤模型；另取8只大鼠不致伤作为空白对照。HS组（40只）：于烧伤前20h行HS，另取8只大鼠仅行HS不烧伤，作为实验对照。放线菌素D组（40只）：在HS前30min静脉注射放线菌素D0．1mg／kg，随后的处理同HS组；另取8只大鼠只注射放线菌素D不烧伤，作为实验对照。于伤后3、6、12、24、48h处死各组大鼠（每组每时相点8只）。取胃黏膜组织检测胃黏膜损伤指数（UI）、HSP70 mRNA、HSP60、HSP70的表达及SOD、CCO的活性。结果大鼠烧伤后uI呈时间依赖性增加，烧伤组伤后24h胃黏膜损伤程度最严重，UI为12．8±1．9。除伤后3h外，HS组大鼠各时相点uI均低于烧伤组（P＜0．05或0．01）。放线菌素D组大鼠胃黏膜损伤程度明显重于烧伤组及HS组（P＜0．05）。烧伤组、HS组除伤后24、48h外其余各时相点HSP70 mRNA均增加，而放线菌素D组伤后24、48h有所增加。与烧伤组比较，HS组大鼠胃黏膜HSP60及HSP70表达显著增加，除伤后48h外其余各时相点比较，差异均有统计学意义（P＜0．05或0．01）。放线菌素D组大鼠HSP60和HSP70表达明显受抑（P＜0．05）。大鼠烧伤后胃黏膜CCO、SOD活性不断降低，经HS后CCO及SOD下降不明显，在伤后6、12、24h均高于同时相点烧伤组（P＜0．05或0．01）。结论HS对大鼠严重烫伤后急性胃黏膜损害具有保护作用，其机制可能与HSP60、HSPT0诱导表达增强，线粒体SOD及CCO活性增加等有关。

Protection of heat shock preconditioning on acute gastric mucosal lesion in scalded rats and its mechanism

OBJECTIVE: To observe the influence of heat shock preconditioning on the expressions of heat shock protein( HSP) 60 and HSP 70 and on the activities of cytochrome oxidase(CCO) and superoxide dismutase( SOD) in mitochondria in gastric mucosa of severely scalded rats, and to investigate its protective mechanism on acute gastric mucosal lesion in rats with severe scald. METHODS: One hundred and forty-four Wistar rats were randomized into three groups, i. e. scald group ( n = 40, acute gastric mucosal lesion was made after scald, other 8 normal rats without scald were employed as blank control) ; HS group( n =40, with heat shock preconditioning 20 h before scald) , and other 8 rats preconditioned with heat shock but without scald were employed as experimental control I; actinomycin D group ( n = 40, with intraperitoneal injection of 0. 1 mg/kg actinomycin D 30 min before heat shock preconditioning and other treatment as HS group) , and other 8 rats with merely actinomycin D injection were employed as experimental control II. Eight rats in each group were sacrificed and laparotomized at 3, 6, 12, 24 and 48 post-scald hours (PSH) , respectively to determine the index of gastric mucosal lesions (UI ) , the mRNA expressions of HSP70 and protein expression of HSP60 and HSP70, and the changes in the activities of SOD and CCO. RESULTS: UI of the scalded rats increased as the time elapses, reaching the peak (12. 8 +/- 1.9) at 24 PSH. In addition, UI in HS group was significantly lower than that in scald group at each time-point except that at 3 PSH ( P < 0. 05 or 0. 01). The extent of gastric mucosal lesion in rats in actinomycin D group was obviously aggravated compared with that in scald and HS groups( P <0. 05). The HSP70 mRNA expression in both scald and HS groups was increased at each time-points except for 48PBH, while that in actinomycin D group was increased at 24 PBH and 48PBH. The expressions of HSP70 and HSP60 were greatly increased in HS group compared with those in scald group ( P < 0. 05 or 0. 01) , while those in actinomycin D group were significantly inhibited ( P < 0. 05). The activities of CCO and SOD were gradually decreased in gastric mocusa in scald group, but it was greatly improved by HS preconditioning at 6, 12, 24 PSH ( P < 0. 05 or 0. 01). CONCLUSION: Heat shock preconditioning is beneficial for the protection of acute gastric mucosal lesion of rats after severe scald, due to increase of HPS60 and HSP70 expression, and increase of CCO and SOD activities in mitochondria.