Differential effects of chloroquine on cardiolipin biosynthesis in hepatocytes and H9c2 cardiac cells

Chloroquine is a potent lysomotropic therapeutic agent used in the treatmen t of malaria. The mechanism of the chloroquine-mediated modulation of new c ardiolipin biosynthesis in isolated rat liver hepatocytes and H9c2 cardiac myoblast cells was addressed in this study. Hepatocytes or H9c2 cells were incubated with [1,3-H-3]glycerol in the absence or presence of chloroquine and cardiolipin biosynthesis was examined. The presence of chloroquine in t he incubation medium of hepatocytes resulted in a rapid accumulation of rad ioactivity in cardiolipin indicating an elevated de novo biosynthesis. In c ontrast, chloroquine caused a reduction in radioactivity incorporated into cardiolipin in H9c2 cells. The presence of brefeldin A, colchicine or 3-met hyladenine did not effect radioactivity incorporated into cardiolipin nor t he chloroquine-mediated stimulation of cardiolipin biosynthesis in hepatocy tes indicating that vesicular transport, cytoskeletal elements or increased autophagy were not involved in de novo cardiolipin biosynthesis induced by chloroquine. The addition of chloroquine to isolated rat liver membrane fr actions did not affect the activity of the enzymes of de novo cardiolipin b iosynthesis but resulted in an inhibition of mitochondrial cytidine-5'-diph osphate-1,2-diacyl-sn-glycerol hydrolase activity. The mechanism for the re duction in cardiolipin biosynthesis in H9c2 cells was a chloroquine-mediate d inhibition of glycerol uptake and this did not involve impairment of lyso somal function. The kinetics of the chloroquine-mediated inhibition of glyc erol uptake indicated the presence of a glycerol transporter in H9c2 cells. The results of this study clearly indicate that chloroquine has markedly d ifferent effects on glycerol uptake and cardiolipin biosynthesis in hepatoc ytes and H9c2 cardiac cells.