抄録
Changes in intracellular hydrogen peroxide concentration ([H2O2]) constitute an important signal controlling cellular adaptations. In response to cooling, decreases in [H2O2] and changes in antioxidant-related gene expression have been observed in skeletal muscle. However, the specific temperature dependence of cooling-induced [H2O2] changes and their quantitative relationship to induced gene expression are unknown. This investigation tested the hypothesis that differences in muscle cytosolic and mitochondrial [H2O2] changes during cooling/rewarming determine the pattern of H2O2-related gene expression. H2O2-sensitive cytosolic (HyPer7) and mitochondrial (MLS-HyPer7) fluorescent proteins were expressed into tibialis anterior (TA) muscle of male C57BL/6J mice. The temperature dependence of [H2O2] was determined via in vivo imaging during 3-minute cooling protocol from 35°C to 0°C. Two cooling patterns (6 bouts of intermittent cooling, I-Cool vs. sustained cooling, S-Cool; both to 13°C) were applied over 60 min. Three hours after cooling, the muscles were removed and gene expression was evaluated using real-time PCR. The decrease in [H2O2] was observed in both cytosolic and mitochondrial compartments from 35°C to 13°C, but was of greater magnitude in the cytosol; in contrast, further cooling from 12°C to 0°C induced a rebound increase especially in cytosolic [H2O2]. I-Cool increased the mRNA level of Nrf2 (+15%, p < 0.001). S-Cool decreased the mRNA levels of Sod2, Cat, and Ucp3 (i.e., -20%, -23%, and -30%, respectively, p<0.05). In conclusion, the greatest decrease in temperature-dependent [H2O2] occurred at 13°C in the cytosolic and mitochondrial compartments of muscle fibers and I-Cool increased Nrf2 mRNA expression, while S-Cool decreased several antioxidant-related genes.