Loss of peroxiredoxin-2 exacerbates eccentric contraction-induced force loss in dystrophin-deficient muscle

Abstract

Force loss in skeletal muscle exposed to eccentric contraction is often attributed to injury. We show that EDL muscles from dystrophin-deficient mdx mice recover 65% of lost force within 120 min of eccentric contraction and exhibit minimal force loss when the interval between contractions is increased from 3 to 30 min. A proteomic screen of mdx muscle identified an 80% reduction in the antioxidant peroxiredoxin-2, likely due to proteolytic degradation following hyperoxidation by NADPH Oxidase 2. Eccentric contraction-induced force loss in mdx muscle was exacerbated by peroxiredoxin-2 ablation, and improved by peroxiredoxin-2 overexpression or myoglobin knockout. Finally, overexpression of γcyto- or βcyto-actin protects mdx muscle from eccentric contraction-induced force loss by blocking NADPH Oxidase 2 through a mechanism dependent on cysteine 272 unique to cytoplasmic actins. Our data suggest that eccentric contraction-induced force loss may function as an adaptive circuit breaker that protects mdx muscle from injurious contractions.

Variable cytoplasmic actin expression impacts the sensitivity of different dystrophin‐deficient mdx skeletal muscles to eccentric contraction

“…Cytoplasmic β‐ and γ‐actins are required for normal skeletal muscle function . We have shown that gross overexpression of cytoplasmic β‐ or γ‐actin by transgenic methods can protect mdx EDL muscle from ECC‐induced force loss , by either blocking the production of force‐inhibiting reactive oxygen species (ROS), or preventing ROS from oxidizing proteins important for muscle contraction . Our data showing that the mdx Sol muscle endogenously expresses significantly greater cytoplasmic β‐ and γ‐actins than the EDL and PL support a new mechanism to explain Sol insensitivity to ECC.…”

“…In fact, the Sol muscle, which is the most protected against ECC‐induced force drop, has the highest specific isometric tetanic force as well as the highest ECC : ISO compared to an EDL or PL. We recently proposed that mdx EDL muscle has an adaptive “circuit breaker” that limits force production to prevent ECC‐induced muscle damage . Based on the results of this study, it could be hypothesized that the Sol muscle does not have the same circuit breaker, potentially due to different cytoplasmic actin expression, MHC composition, or utrophin content.…”

“…All mice used in this study were adult males (3–6 months of age) except dystrophin/utrophin double knockout mice which were 7 weeks of age because of their shortened life span. Our previous studies have shown that there is no difference in the sensitivity of 3‐ or 6‐month‐old mdx skeletal muscle to ECCs . Further yet, there is no difference in the level of skeletal muscle degeneration and regeneration in mdx mice between the ages of 3 and 6 months .…”

“…E). We have also previously shown that ECC‐induced force loss of mdx EDL muscle in vitro is attenuated in the presence of an antioxidant . To determine whether PL force loss is similarly affected by an oxidative component, we incubated the PL muscle with N ‐acetyl cysteine (NAC).…”

“…There is also evidence that changes in cytosolic calcium can impact ECC‐induced force loss and that overexpression of SERCA1 provides protection . Finally, we and others have previously shown that skeletal muscles in mdx mice have 10‐ and 14‐fold greater expression of cytoplasmic γ‐ and β‐actins than wild‐type mice, respectively, while transgenic overexpression of either actin isoform significantly protects the EDL from ECC‐induced force loss . However, the relationship between endogenous cytoplasmic γ‐ or β‐actin expression in different mdx skeletal muscles and their impact on sensitivity to ECC has not been investigated.…”