FLOW CYTOMETRIC DETECTION OF MITOCHONDRIAL DYSFUNCTION IN SUBPOPULATIONS OF HUMAN MONONUCLEAR-CELLS

At 488 nm argon-ion laser excitation human mononuclear cells emit flav oprotein-related autofluorescence signals. Approximately 60% of these are caused by the mitochondrial flavoproteins alpha-lipoamide dehydrog enase and electron transfer flavoprotein, having differences in their fluorescence emission spectra, At the emission wavelength of 530 nm th e redox changes of alpha-lipoamide dehydrogenase fluorescence in human mononuclear cells can be monitored by Row cytometry. This allows the estimation of the steady-state reduction level of this flavoprotein be ing in redox equilibrium with the mitochondrial NAD-system. We applied this method to elucidate the possible impairment of mitochondrial fun ction in subpopulations of mononuclear cells of patients harboring del etions of the mitochondrial DNA in skeletal muscle, In the monocyte fr action of three patients and in the lymphocyte fraction of one patient we observed in the presence of the mitochondrial substrate octanoate elevated steady-state reduction levels of alpha-lipoamide dehydrogenas e. This is arm indication for the presence of respiratory chain-inhibi ted mitochondria in mononuclear cell subpopulations of the described p atients, These data were confirmed by conventional determinations of m aximal oxygen consumption rates of digitonin-permeabilized cells. Ther efore, the flow cytometric determination of flavoprotein-caused autofl uorescence changes is a useful and sensitive method for the detection of an impairment of mitochondrial respiratory chain in subpopulations of heterogeneous cell suspensions. (C) 1997 Academic Press.