Purpose: We have shown heat stress induces mitochondrial biogenesis in skeletal muscle. However, its underlying mechanisms have not been clarified. Recent emerging evidence indicates that tumor-suppressor p53 involved in exercise-driven mitochondrial gene transcription in skeletal muscle. Based on these findings, we tested whether a single session of heat stress treatment activates p53 and whether the activation of p53 pathway can be a mechanism underlying heat stress-induced mitochondrial biogenesis. Methods: Male ICR mice were involved. Immediately after treatment and three hours after a single bout of heat stress treatment (exposing mouse into a hot environment chamber; 40°C, 30 min), gastrocnemius muscles were collected and then examined changes in expression of mitochondrial genes and p53 activity (phosphorylation status and nuclear and mitochondrial localization). Results: We found a single bout of heat stress increased expression of mitochondria-related genes encoded by nDNA (Cs: +21.7%, Alas: +24.8%, Tfam: +21.7% and Cytc: +22.5%, P<0.05) and mtDNA (Cox2: +38.5%, Nd1: +29.1% and Nd4: +40.4%, P<0.05) three hours after treatment. However, there are non-detectable changes in phosphorylation(P=0.84) and sub-cellular localizations of p53 (no p53 band on western blot was observed in nuclear and mitochondrial fractions) at both immediately and 3h after heat stress. Conclusion: Heat stress activates mitochondrial gene transcription, which may not be mediated by p53 activation.
