Hypotonic swelling promotes Nitric Oxide release in rat cardiac myocytes: impact on swelling-induced negative inotropic effect

GONANO L, MORELL M, VILA PETROFF M

San Diego

Congreso; ISHR World Congress; 2013

Cardiomyocyte swelling occurs in multiple pathological situations and in particular, it has been shown to contribute to the deleterious effects of ischemia and reperfusion by promoting contractile dysfunction. We have previously shown that myocyte axial stretch promotes nitric oxide (NO) release. However, whether myocyte swelling promotes NO release and if so, whether it impacts on swelling-induced contractile dysfunction has not been previously assessed. We found that treating rat cardiac myocytes, loaded with the NO sensor DAF-FM, with a hypotonic solution, increased cell volume, reduced myocyte contraction amplitude and significantly increased DAF-FM fluorescence. When cells were exposed to the hypotonic solution supplemented with 2.5 mM of the NO synthase inhibitor L-Name, cell swelling occurred in the absence of NO release. Swelling-induced NO release was also inhibited by the PI3K inhibitor Wortmannin. Interestingly, swelling-induced negative inotropic effect was exacerbated in the presence of L-Name or Wortmannin. These results suggest that swelling activates NOS3 (NOS3 being a known target of the PI3K/AKT axis in contrast to NOS1) which promotes NO release. In adition, using colchicine (an inhibitor of microtubule polymerization) we evaluated the participation of the cytoskeleton as a mechanotransducer of Swelling-dependent NO release. The increase in DAF-FM fluorescence was prevented when hypotonic stress applied to cardiomyocytes pre-incubated whith Colchicine. This result suggests that cytoskeleton integrity is nessesary for swelling-induced NO release. Taken together, these findings suggest a novel mechanism for NO release in cardiac myocytes with putative pathophysiological relevance in the context of ischemia and reperfusion, where it may serve a cardioprotective role by reducing the extent of swelling-induced contractile dysfunction.