Koury Jadd, Deitch Edwin A, Homma Hiroshi, Abungu Billy, Gangurde Pranoti, Condon Michael R, Lu Qi, Xu Da-Zhong, Feinman Rena
Department of Surgery, UMDNJ-New Jersey Medical School, Newark, New Jersey 07103, USA.
Shock. 2004 Sep;22(3):270-7. doi: 10.1097/01.shk.0000135256.67441.3f.
In both animal models of hemorrhagic shock and clinical settings, shock-induced gut ischemia has been implicated in the development of the systemic inflammatory response syndrome and distant organ injury, yet the factors transducing these events remain to be fully determined. Because hypoxia-inducible factor (HIF-1), a transcription factor composed of oxygen-labile HIF-1alpha and constitutive HIF-1beta subunits, regulates the physiologic/pathophysiologic response to hypoxia and ischemia, we examined the HIF-1 response in two rat models of gut ischemia-reperfusion. We found that ileal nuclear HIF-1alpha protein levels were induced in rats subjected to trauma (laparotomy) plus hemorrhagic shock for 90 min relative to their trauma sham-shock and naïve counterparts and that this trauma hemorrhagic shock-induced mucosal HIF-1alpha protein response persisted after 1 h and 3 h of reperfusion. Likewise, in a model of isolated gut ischemia-reperfusion injury, where the superior mesenteric artery was occluded for 45 min, nuclear HIF-1alpha were induced in the gut mucosa relative to their sham counterparts and persisted after 1 h and 3 h or reperfusion. Similar to the in vivo response, in vitro hypoxia induced HIF-alpha expression in three different enterocyte cell lines (rat IEC-6 and human Caco-2 and HT-29 cell lines). However, in contrast to the in vivo response, HIF-1 expression rapidly disappeared on subsequent reoxygenation. Because in vivo enterocytes are exposed to bacteria, we tested whether the in vitro HIF-1alpha response would persist on reoxygenation if the enterocytes were cocultured with bacteria. P. aeruginosa, an enteric bacterium, markedly induced enterocyte HIF-1alpha protein levels under normoxic conditions. Furthermore, the addition of P. aeruginosa during either the hypoxic or reoxygenation phase prevented the degradation of HIF-1alpha protein levels. Moreover, the observation that lipopolysaccharide induced HIF-1alpha expression in a time-dependent manner in IEC-6 cells indicated that the induction of HIF-1 by exposure to P. aeruginosa is not dependent on bacterial viability. In conclusion, these results suggest that HIF-1alpha activation is an early reperfusion-independent event in models of gut ischemia-reperfusion and that this HIF-1alpha response is potentiated by the presence of P. aeruginosa or lipopolysaccharide.
在出血性休克的动物模型和临床环境中，休克诱导的肠道缺血被认为与全身炎症反应综合征和远处器官损伤的发生有关，然而，介导这些事件的因素仍有待完全确定。由于缺氧诱导因子（HIF-1）是一种由氧不稳定的HIF-1α和组成型HIF-1β亚基组成的转录因子，可调节对缺氧和缺血的生理/病理生理反应，我们在两种大鼠肠道缺血再灌注模型中研究了HIF-1反应。我们发现，与创伤假休克组和未处理组相比，经历创伤（剖腹术）加90分钟出血性休克的大鼠回肠核HIF-1α蛋白水平升高，并且这种创伤性出血性休克诱导的黏膜HIF-1α蛋白反应在再灌注1小时和3小时后持续存在。同样，在孤立性肠道缺血再灌注损伤模型中，肠系膜上动脉闭塞45分钟，与假手术组相比，肠道黏膜中核HIF-1α水平升高，并在再灌注1小时和3小时后持续存在。与体内反应相似，体外缺氧诱导三种不同肠上皮细胞系（大鼠IEC-6和人Caco-2及HT-29细胞系）中的HIF-α表达。然而，与体内反应不同的是，随后再给氧时HIF-1表达迅速消失。由于体内肠上皮细胞暴露于细菌，我们测试了如果肠上皮细胞与细菌共培养，体外HIF-1α反应在再给氧时是否会持续。铜绿假单胞菌是一种肠道细菌，在常氧条件下可显著诱导肠上皮细胞HIF-1α蛋白水平。此外，在缺氧或再给氧阶段添加铜绿假单胞菌可防止HIF-1α蛋白水平的降解。此外，脂多糖在IEC-6细胞中以时间依赖性方式诱导HIF-1α表达的观察结果表明，暴露于铜绿假单胞菌对HIF-1的诱导不依赖于细菌活力。总之，这些结果表明，在肠道缺血再灌注模型中，HIF-1α激活是早期不依赖再灌注的事件，并且这种HIF-1α反应因铜绿假单胞菌或脂多糖的存在而增强。
