Evidence that actin disassembly is a requirement for matrix metalloproteinase secretion by sinusoidal endothelial cells during cold preservation in the rat.

Abstract

Cold preservation induces the secretion of matrix metalloproteinases (MMPs) by hepatic sinusoidal endothelial cells (SECs). These enzymes are important mediators of cold preservation injury. The purpose of this study was to determine if low temperature caused actin disassembly in SECs and whether actin disassembly was required for secretion of MMPs under these conditions. To establish the basis of interpreting the effect of low temperature, isolated SECs were exposed to cytochalasin B with or without pretreatment with phalloidin. Cytochalasin B produced actin disassembly and resulted in the secretion of MMPs. Both were retarded by phalloidin pretreatment. Low temperature (4 degrees C) also induced actin disassembly and MMP secretion and pretreatment with phalloidin again retarded actin disassembly and MMP secretion. Cycloheximide had no effect on these results. Actin disassembly began with 30 minutes of exposure of isolated SECs to cold and reached a final state at 8 hours, at which time no actin stress fibers were visible, and the normally fusiform SECs were fully rounded. Increased MMP activity in the supernatant was also present at 30 minutes and continued to rise sharply in the first hour; thereafter the rate of rise diminished. The study shows that secretion of MMPs during cold preservation is dependent on the induction of actin disassembly by low temperature. The rapid appearance of increased MMP activity after exposure to cold and the studies using cycloheximide indicate that the MMPs originate from preformed MMPs rather than newly synthesized MMPs.