Pharmacological inhibition of Rac1 attenuates myocardial abnormalities in tail-suspended mice.

Microgravity conditions cause myocardial abnormalities with limited therapeutic approaches. We reported that NADPH oxidase-derived reactive oxygen species contribute to microgravity-induced myocardial abnormalities. This study investigated whether pharmacological inhibition of Rac1 protected the heart during microgravity. Simulated microgravity was induced by tail-suspension in mice. Tail-suspension for 28 days increased Rac1 activity in hearts, reduced heart weight and cross-sectional areas of cardiomyocytes, indicative of myocardial atrophy, and myocardial dysfunction. Administration of NSC23766, a selective inhibitor of Rac1, or atorvastatin reported to inhibit Rac1 activation, attenuated myocardial atrophy and preserved myocardial function in tail-suspended mice. These protective effects of Rac1 inhibition were associated with inhibition of NADPH oxidase activation and a reduction of oxidative stress. Our finding may inform a future clinical trial using atorvastatin to prevent myocardial abnormalities under microgravity conditions.