Systemic injection of a tripeptide inhibits the intracellular activation of CPP32-like proteases in vivo and fully protects mice against Fas-mediated fulminant liver destruction and death

Abstract

Mice injected with anti-Fas antibody die within a few hours with total liver destruction due to massive apoptosis of hepatocytes. We show that this is preceded and accompanied by the sequential activation of cysteine proteases of the interleukin 1β-converting enzyme (ICE) and CPP32 types in the cytosol of the hepatocytes, and that proCPP32 cleavage and enzymatic activity can be prevented by intravenous injections of the tripeptide N- benzyloxycarbonyl-Val-Ala Asp fluoromethylketone (Z-VAD.fmk), an inhibitor of ICE-like proteases. Four Z-VAD.fmk injections at 1 hour intervals abolished all signs of liver damage after anti-Fas antibody injection and resulted in 100% long-range recovery, without residual tissue damage, from a condition otherwise uniformly fatal within <3 hours. This treatment was effective even when delayed until some liver DNA degradation was already detectable. Injections of the tetrapeptide AcYVAD.cmk, more specific for the ICE-like subfamily of cysteine proteases but less cell permeable, also gave protection, but at higher doses and when injections started before that of anti-Fas antibody. These observations afford a way of temporarily modulating a number of apoptotic processes in vivo and may have important therapeutic implications in some human diseases.