REACTIVE OXYGEN SPECIES INDUCE APOPTOSIS IN CULTURED HUMAN MESANGIAL CELLS

Apoptosis is a distinct form of cell death that is observed under vari ous physiologic and pathologic conditions, and it is thought to be imp ortant in regulating the number of glomerular cells, This study invest igated the possible role of reactive oxygen species in the induction o f apoptosis in cultured human mesangial cells, Fragmented nuclei with condensed chromatin, a morphologic characteristic of apoptosis, were o bserved by electron microscopy in mesangial cells exposed to 0.02 mM h ydrogen peroxide for 4 h. Nuclear DNA extracted from mesangial cells t hat had been incubated with hydrogen peroxide (2 to 20 mM) or with xan thine (0.05 mM) and xanthine oxidase (5 to 100 mU/mL) showed the ladde r pattern on electrophoresis that is a biochemical marker for apoptosi s, Hydrogen peroxide (0.02 to 20 mM) decreased the number of viable ce lls, as determined by trypan blue exclusion, in a dose-dependent manne r, Hydrogen peroxide or xanthine and xanthine oxidase increased the la ctate dehydrogenase release from mesangial cells in a dose- and time-d ependent manners, The release of lactate dehydrogenase was prevented b y treatment with a free radical scavenger, catalase. Hydrogen peroxide (2 mM) also significantly increased the number of mesangial cells wit h fragmented DNA as detected by in situ nick end-labeling, Results ind icate that reactive oxygen species induce apoptosis in cultured human mesangial cells, Furthermore, apoptosis of mesangial cells induced by reactive oxygen species may contribute to the loss of such cells obser ved in glomerular disease.