Chenodeoxycholate is toxic to hepatocytes, and accumulation of
chenodeoxycholate in the liver during
cholestasis may potentiate hepatocellular injury. However, the mechanism of hepatocellular injury by
chenodeoxycholate remains obscure. Our aim was to determine the mechanism of cytotoxicity by
chenodeoxycholate in rat hepatocytes. At a concentration of 250 microM,
glycochenodeoxycholate was more toxic than either
chenodeoxycholate or
taurochenodeoxycholate. Cellular
ATP was 86% depleted within 30 min after addition of
glycochenodeoxycholate.
Fructose, a glycolytic substrate, maintained
ATP concentrations at 50% of the initial value and protected against
glycochenodeoxycholate cytotoxicity.
ATP depletion in the absence of a glycolytic substrate suggested impairment of mitochondrial function. Indeed,
glycochenodeoxycholate inhibited state 3 respiration in
digitonin-permeabilized cells in a dose-dependent manner. After
ATP depletion, a sustained rise in cytosolic free
calcium (Cai2+) was observed. Removal of extracellular Ca2+ abolished the rise in Cai2+, decreased cellular proteolysis, and protected against cell killing by
glycochenodeoxycholate. The results suggest that
glycochenodeoxycholate cytotoxicity results from
ATP depletion followed by a subsequent rise in Cai2+. The rise in Cai2+ leads to an increase in
calcium-dependent degradative proteolysis and, ultimately, cell death. We conclude that
glycochenodeoxycholate causes a bioenergetic form of lethal cell injury dependent on
ATP depletion analogous to the lethal cell injury of
anoxia.