Atmospherically relevant PM2.5 promotes age-related muscle atrophy in an age-dependent manner

Maintaining the quality and function of skeletal muscle in the older adult has become a key topic in successful aging. However, the impact of environmental factors on skeletal muscle aging is often overlooked. This study used male mice aged 1, 6, and 15 months, which were each exposed to PM 2.5 (50 μg/m 3 , 2 h/day) for 5 days, and the skeletal muscles of each age group were analyzed one month after the end of the treatment to verify the age-specific effects of PM 2.5 on the skeletal muscle system. Total body weight and lean body weight were significantly affected by age and PM 2.5 exposure. However, fat levels were not affected by PM 2.5 exposure. PM 2.5 exposure promoted the development of age-related muscle atrophy by inducing oxidative stress and increased expression of Myostatin in skeletal muscle of older adults. On the other hand, the damaging effect of PM 2.5 exposure on skeletal muscle mitochondria was age-related. Young and older adult mice showed extensive mitochondrial damage after PM 2.5 exposure. In particular, older adults showed a marked increase in mitochondrial fission and mitophagy after PM 2.5 exposure. The effects of PM 2.5 exposure on the skeletal muscle system are age-specific, with distinct damaging effects during growth and aging, whereas skeletal muscles in middle-aged mice are resistant to PM 2.5 -induced damage. • PM 2.5 exposure accelerates age-related skeletal muscle atrophy in mice. • Age determines susceptibility of muscle to PM 2.5 -induced oxidative damage. • PM 2.5 triggers excessive mitochondrial fission and mitophagy in aged muscle. • Environmental pollutants may be risk factors for sarcopenia and muscle aging.