Stimulation of H(2)O(2) generation by calcium in brain mitochondria respiring on alpha-glycerophosphate.
It has been reported recently (Tretter et al., 2007b) that in isolated guinea pig brain mitochondria supported by alpha-glycerophosphate (alpha-GP) reactive oxygen species (ROS) are produced through the reverse electron transport (RET) in the respiratory chain and by alpha-glycerophosphate dehydrogenase (alpha-GPDH). We studied the effect of calcium on the generation of H(2)O(2) as measured by the Amplex Red fluorescent assay in this model. H(2)O(2) production in alpha-GP-supported mitochondria was increased significantly in the presence of 100, 250, and 500 nM Ca(2+), respectively. In addition, Ca(2+) enhanced the membrane potential, the rate of oxygen consumption, and the NAD(P)H autofluorescence in these mitochondria. Direct measurement of alpha-GPDH activity showed that Ca(2+) stimulated the enzyme by decreasing the Km for alpha-GP. In those mitochondria where RET was eliminated by the Complex I inhibitor rotenone (2 microM) or due to depolarization by ADP (1 mM), the rate of H(2)O(2) formation was smaller and the stimulation of H(2)O(2) generation by Ca(2+) was prevented partly, but the stimulatory effect of Ca(2+) was still significant. These data indicate that in alpha-GP-supported mitochondria activation of alpha-GPDH by Ca(2+) leads to an accelerated RET-mediated ROS generation as well as to a stimulated ROS production by alpha-GPDH.
Tretter
Laszlo
L
Department of Medical Biochemistry, Semmelweis University, Neurobiochemical Group, Hungarian Academy of Sciences and Szentagothai Janos Knowledge Center, Budapest, Hungary.
Takacs
Katalin
K
Kövér
Kinga
K
Adam-Vizi
Vera
V
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D019069:Cell Respiration / Q000502:physiology*; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism*; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*
D005994:Glycerophosphates; C029620:alpha-glycerophosphoric acid; D006861:Hydrogen Peroxide; D005993:Glycerolphosphate Dehydrogenase; D002118:Calcium