Endothelin-1 contributes to increased NFATc3 activation by chronic hypoxia in pulmonary arteries

de Frutos S, Ramiro Diaz JM, Nitta CH, Sherpa ML, Gonzalez Bosc LV. Endothelin-1 contributes to increased NFATc3 activation by chronic hypoxia in pulmonary arteries. Am J Physiol Cell Physiol 301: C441-C450, 2011. First published April 27, 2011; doi: 10.1152/ajpcell.00029.2011.-Chronic hypoxia (CH) activates the Ca2+-dependent transcription factor nuclear factor of activated T cells isoform c3 (NFATc3) in mouse pulmonary arteries. However, the mechanism of this response has not been explored. Since we have demonstrated that NFATc3 is required for CH-induced pulmonary arterial remodeling, establishing how CH activates NFATc3 is physiologically significant. The goal of this study was to test the hypothesis that endothelin-1 (ET-1) contributes to CH-induced NFATc3 activation. We propose that this mechanism requires increased pulmonary arterial smooth muscle cell (PASMC) intracellular Ca2+ concentration ([Ca2+](i)) and stimulation of RhoA/Rho kinase (ROK), leading to calcineurin activation and actin cytoskeleton polymerization, respectively. We found that: 1) CH increases pulmonary arterial pre-pro-ET-1 mRNA expression and lung RhoA activity; 2) inhibition of ET receptors, calcineurin, L-type Ca2+ channels, and ROK blunts CH-induced NFATc3 activation in isolated intrapulmonary arteries from NFAT-luciferase reporter mice; and 3) both ET-1-induced NFATc3 activation in isolated mouse pulmonary arteries ex vivo and ET-1-induced NFATc3-green fluorescence protein nuclear import in human PASMC depend on ROK and actin polymerization. This study suggests that CH increases ET-1 expression, thereby elevating PASMC [Ca2+] i and RhoA/ROK activity. As previously demonstrated, elevated [Ca2+] i is required to activate calcineurin, which dephosphorylates NFATc3, allowing its nuclear import. Here, we demonstrate that ROK increases actin polymerization, thus providing structural support for NFATc3 nuclear transport.