Superoxide: A major factor for stress protein induction in reoxygenation injury in the intestinal cell line Caco-2

Background/Aims: Acute intestinal ischemia is followed by cellular destruct ion and loss of mucosal barrier function. Posthypoxic injury of cellular pr oteins leads to the synthesis of heat shock proteins. The role of oxygen ra dicals in this process, however, is not fully established. Methods: In the present study, using the intestinal cell line Caco-2, we investigated the r elationship between the synthesis of the heat shock protein HSP70, detected by Western blot and oxygen radicals as well as lactate dehydrogenase (LDH) release, as measured in photometrical tests. Results: Various periods of h ypoxia and 30 min of reoxygenation resulted in an increased generation of s uperoxide as measured by the tetrazolium base 3-(4,5-dimethylthiazol-2-yl)2 ,5-diphenyltetrazoliumbromide. The inhibitor of superoxide dismutase (SOD), diethyldithiocarbamate (DDC) increased and addition of SOD decreased intra cellular superoxide levels. HSP70 synthesis was detectable after 2 h of hyp oxia. Similar to superoxide production, DDC increased and SOD reduced the H SP70 synthesis, In contrast, the increased LDH release from the cells obser ved after hypoxia was not significantly altered by DDC and SOD. Conclusion: The production of superoxide correlates with HSP70 induction, but not with LDH release. We conclude that hypoxia/reoxygenation induces heat shock pro tein production, a result of protein damage, by increased superoxide genera tion, whereas superoxide does not correlate with membrane damage in Caco-2 cells.