Telomeres shorten in response to oxidative stress in mouse skeletal muscle fibers.

Aging phenotypes are dictated by myriad cellular changes including telomere shortening. In most tissues, telomere shortening is accelerated during replication if unrepaired oxidative damage to telomere sequences is present. However, the effect of reactive oxygen species exposure on skeletal muscle telomeres is unknown. We sought to determine if oxidative stress shortens telomeres in isolated adult rodent skeletal muscle fibers. Flexor digitorum brevis muscles were dissected from male mice (C57BL/6, long telomere and CAST/Ei, wild-derived, short telomere) and dissociated into single fibers. Fibers were cultured at an oxygen tension of 2%-5% for 5 days in control, hydrogen peroxide (oxidant), or a combination of N-acetylcysteine (antioxidant) and oxidant containing media. Telomere length, telomerase enzyme activity, and protein content of TRF1 and TRF2 were subsequently measured. In both strains, oxidative stress resulted in significant telomere shortening in isolated skeletal muscle fibers, likely by different mechanisms. Telomerase activity was not altered by oxidative stress treatment but was significantly different between strains, with greater telomerase activity in long-telomere-bearing C57BL/6 mice. These results provide important insights into mechanisms by which oxidative stress could shorten skeletal muscle telomeres.