CYCLOSPORINE AND CARNITINE PREVENT THE ANOXIC DEATH OF CULTURED-HEPATOCYTES BY INHIBITING THE MITOCHONDRIAL PERMEABILITY TRANSITION

Cyclosporin A (CyA) and L-carnitine (LC) prevented the killing of cult ured hepatocytes by anoxia and rotenone but not by cyanide. Neither Cy A nor LC affected the rate or extent of the loss of the mitochondrial membrane potential or the rate or extent of the depletion of ATP. Atra ctyloside blocked the ability of both CyA and LC to protect, and D-car nitine antagonized the effect of LC but not that of CyA. Cell killing by cyanide was prevented when the phospholipase A2 inhibitor butacaine was added together with CyA. Butacaine by itself had no effect on cel l killing. In a swelling assay with isolated rat liver mitochondria ha ving a low calcium content, phenylarsine oxide or palmitoyl-CoA induce d the inner membrane permeability transition when electron transport w as inhibited by rotenone or cyanide. CyA prevented the permeability tr ansition with rotenone but not with cyanide, and atractyloside reverse d the effect of CyA. LC prevented the permeability transition occurrin g with palmitoyl-CoA plus rotenone but not with palmitoyl-CoA plus cya nide. Atractyloside and D-carnitine antagonized the protective effect of LC. Inhibition of the cyanide-dependent permeability transition in isolated liver mitochondria required the presence of both CyA and buta caine. These data document the close correlation between the effect of CyA and LC on the response of cultured hepatocytes to inhibition of m itochondrial electron transport and their ability to prevent the perme ability transition in isolated mitochondria. It is concluded that the ability of CyA and LC to protect cultured hepatocytes is a consequence of their ability to prevent the mitochondrial permeability transition , indicating that this event is likely to be causally linked to the ge nesis of irreversible injury. Thus, cell death with anoxia or inhibito rs of electron transport is related to a mitochondrial alteration by a mechanism that is independent of the maintenance of a membrane potent ial or cellular stores of ATP.