Endotoxic shock leads to apoptosis in vivo and reduces Bcl-2

Endotoxic shock results in multiple organ failure. At present, two different mechanisms of cellular destruction are of interest: necrosis and apoptosis. Therefore, we started to investigate in pigs whether cell death due to apoptosis is involved in this pathophysiological process. DNA fragments were detected by ELISA specific for histone-associated DNA fragments in three different experimental settings, Pigs were laparotomized followed by endotoxin infusion (ETOX group, n = 6), or laparotomized without endotoxin infusion (LAP group; n = 3) and compared with control animals (n = 3). 6 h of continuous endotoxin-infusion (5 micrograms/kg/h) resulted in a significantly enhanced apoptosis in liver as compared with controls animals (295 +/- 11%; p < .01), whereas in the LAP group, only a minor increase of 166 +/- 14% was detectable. In spleen of endotoxin-treated animals, an enhanced apoptosis of 150 +/- 12% compared with controls was shown in the ETOX group (p = .02), whereas kidney remained unaffected. These results were confirmed by agarose DNA gel electrophoresis. A typical DNA ladder was detected in liver and spleen, but not in kidney of endotoxin-treated animals. Furthermore, immunohistochemical detection of DNA strand breaks with terminal deoxynucleotidyl transferase in liver sections revealed a drastic increase of stained cells. The induction of apoptosis correlated with a reduced Bcl-2 content in endotoxin-treated animals. Our study demonstrates that 6 h of endotoxin treatment leads to apoptosis in liver and spleen in vivo, whereas kidney of endotoxin-treated animals remains unaffected. This process may be mediated by reduction of Bcl-2 by endotoxin treatment.