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Downhill Running Decreases the Acetylation of Tubulins and Impairs Autophagosome Degradation in Rat Skeletal Muscle.

PURPOSE
This study was designed to probe the effect of downhill running on microtubule acetylation and autophagic flux in rat skeletal muscle.


METHODS
Sprague-Dawley rats were subjected to an exercise protocol of a 90-min downhill run with a slope of -16° and a speed of 16 m/min, and then the soleus was sampled at 0 h, 12 h, 24 h, 48 h, and 72 h after exercise. Protein expression levels of microtubule-associated protein 1 light chain 3 (LC3), p62/sequestosome 1 (p62), α-tubulin and acetylated α-tubulin (AcK40 α-tubulin) were detected by Western blotting. Alpha-tubulin was costained with acetylated α-tubulin (AcK40 α-tubulin) or cytoplasmic dynein intermediate chain in a single muscle fiber, and LC3 was costained with lysosomal associated membrane protein 1 (LAMP1) in cryosections. To assess autophagic flux in vivo, colchicine or vehicle was injected intraperitoneally 3 days before the exercise experiment, and the protein levels of LC3 and p62 were measured by Western blotting.


RESULTS
Downhill running induced a significant increase in the protein levels of LC3-II and p62, while the level and proportion of AcK40 α-tubulin were markedly decreased. Furthermore, the amount of dynein on α-tubulin was decreased after downhill running, and autophagosomes accumulated in the middle of myofibrils. Importantly, LC3-II flux was decreased following downhill running compared with that in the control group.


CONCLUSIONS
A bout of downhill running decreases microtubule acetylation, which may impair dynein recruitment and autophagosome transportation, causing blocked autophagic flux.