Oxidative stress and upregulation of mitochondrial biogenesis genes in mitochondrial DNA-depleted HeLa cells

The signaling mechanism through which deficitary mitochondrial function wou ld activate nuclear genes required for mitochondrial biogenesis, has not be en established. To explore the hypothesis that reactive oxygen species (ROS ), a mitochondrial product, constitute part of the mitochondria-nuclei sign aling pathway, Re obtained Beta cells depleted of mitochondrial DNA (rho(0) cells) through exposure to ethidium bromide. We found evidences of oxidati ve stress in rho(0) cells, employing a fluorescent probe and measuring NF-k appa B activation. Nuclear Respiratory Factor-1 (NRF-1) and Mitochondrial T ranscription Factor A (Tfam) mRNA were measured by RT-PCR, For both transcr iption factors, rho(0) cells revealed significantly higher levels of mRNA T hese results support several hypothesis: that endogenous ROS enhance the ex pression of nuclear mitochondrial biogenesis genes NRF-1 and Tfam; that DNA deprived mitochondria lead to cellular oxidative stress, probably because of incomplete biogenesis of the mitochondrial electron transport chain, and consequently, that ROS are part of a mitochondria-nuclei regulatory signal ing pathway, (C) 1999 Academic Press.