Caffeine impairs HL-60 cellular respiration

ABSTRACT

We investigated the effect of caffeine on mitochondrial O[2] consumption in human promyelocytic leukemia [HL-60] cells. A phosphorescence analyzer that measures O[2] concentrations in cell suspensions as function of time was used for this purpose. O[2] concentrations were determined from the phosphorescence of Pd phosphor, calculated by fitting the phosphorescence decays to exponentials. In sealed vials, O[2] concentrations in the cell suspensions containing glucose declined linearly with time, showing zero-order kinetics for O[2] consumption. NaCN inhibited O[2] consumption, confirming the oxidation occurred in the mitochondrial respiratory chain. A rapid decline in the rate of respiration was observed when 50 [micro]M to 4.0 mM caffeine was added to HL-60 cells in cell growth media [containing 1.41 mM Ca[2+]] or phosphate-buffered-salts [containing 0.91 mM Ca[2+]]. This reversible inhibition was blocked by verapamil and was concentration-dependent, reaching a plateau [43 +/- 7% inhibition] at 50 [micro]M caffeine. The inhibition was not observed when cellular Can+ stores were depleted. T-cell lymphoma [Jurkat] cells and isolated mitochondria were less sensitive to caffeine. Thus, caffeine is a potent inhibitor of HL-60 respiration. This effect is possibly mediated by Ca[2+]-flooding into the cytosol and neighboring mitochondria