Protection of NADH‐linked Fe‐S clusters in cardiac mitochondria by ranolazine

Abstract

Mitochondrial complex I (CI), composed of Fe‐S clusters numbered N1‐N5, is susceptible to damage by reactive oxygen species during cardiac ischemia reperfusion (IR). We used electron paramagnetic resonance (EPR) to assess how IR injury affects these Fe‐S clusters and if ranolazine (RAN), an antianginal drug, attenuates these effects. Guinea pig hearts were perfused with Krebs Ringer (KR) buffer and subjected to one of the following protocols: a) KR perfusion for 30 min, b) 30 min ischemia (I), c) 5 μM RAN for 1 min before ischemia (RAN+I), d) 30 min ischemia followed by 10 min reperfusion (IR) and e) 5 μM RAN for 1 min before 30 min ischemia and 10 min reperfusion (RAN+IR). Hearts were immediately ground in liquid N2 and the powder packed into EPR tubes. Changes in signal intensities at g=1.94, 1.86, and 1.89, assigned to N1b, N3, and N4, respectively, were recorded at 10°K (liquid He) at 9.6 GHz, 5 mW. Versus time control (100%), N1b signal decreased to 0% in the I hearts and was restored to 40%, 100%, and 70% in IR, RAN+I and RAN+IR hearts, respectively. N4 signal was 67% for I, 183% for RAN+I, 117% for IR, and 100% in RAN+IR hearts. N3 signal was 50% for both IR and RAN+IR hearts, and unaltered for I and RAN+I hearts (100%). These data suggest that RAN treatment before IR protects electron flux only through some Fe‐S centers. This finding may underlie a possible mechanism of RAN to attenuate electron flux in distinct Fe‐S clusters of CI.This work was supported in part by grants from NIH HL089514 and HL073246; VA 8204‐05P, and AHA 0855940G.