Rapamycin inhibits hydrogen peroxide-induced loss of vascular contractility

Cao C, Li J, Li Y, Li D, Wang Y, Wang L, Tang XD, Walsh MP, Gui Y, Zheng X-L. Rapamycin inhibits hydrogen peroxide-induced loss of vascular contractility. Am J Physiol Heart Circ Physiol 300: H1583-H1594, 2011. First published February 25, 2011; doi:10.1152/ajpheart.01084.2010.-Rapamycin. an inhibitor of the mammalian target of rapamycin (mTOR) pathway, has been shown to extend the life span of mice, and oxidative stress plays critical roles in vascular aging involving loss of compliance of arteries. We examined, therefore, whether rapamycin has protective effects on the inhibition of vascular contractility by hydrogen peroxide (H2O2). Prolonged (3 h) exposure to H2O2 induced complete loss of contraction of mouse aortic rings and mesenteric (resistance) arteries to either KCl or phenylephrine, which was attenuated by pretreatment with rapamycin. H2O2-induced loss of contractility was unaffected by treatment with actinomycin D or cycloheximide, inhibitors of gene transcription and protein synthesis, respectively. Western blot analysis showed that there was no increase in phosphorylation of S6 kinase 1 (S6K) or factor 4E binding protein 1 (4EBP1) in response to H2O2 treatment, suggesting involvement of the mTOR complex-2 (mTORC2) rather than mTORC1. H2O2 treatment inhibited phosphorylation of the 20-kDa regulatory light chains of myosin (LC20), which was partially blocked by rapamycin treatment. Interestingly, the calcineurin inhibitors cyclosporine A and FK506 were found to mimic the rapamycin effect, and rapamycin inhibited calcineurin activation induced by H2O2. We conclude that rapamycin inhibits H2O2-induced loss of vascular contractility, likely through an mTORC2-calcineurin pathway.