Hydrogen peroxide-induced Ca²⁺mobilization in pulmonary arterial smooth muscle cells

Abstract

March 16, 2007; doi:10.1152/ajplung.00323.2006.-Reactive oxygen species (ROS) generated from NADPH oxidases and mitochondria have been implicated as key messengers for pulmonary vasoconstriction and vascular remodeling induced by agonists and hypoxia. Since Ca 2ϩ mobilization is essential for vasoconstriction and cell proliferation, we sought to characterize the Ca 2ϩ response and to delineate the Ca 2ϩ pathways activated by hydrogen peroxide (H2O2) in rat intralobar pulmonary arterial smooth muscle cells (PASMCs). Exogenous application of 10 M to 1 mM H 2O2 elicited concentration-dependent increase in intracellular Ca 2ϩ concentration in PASMCs, with an initial rise followed by a plateau or slow secondary increase. The initial phase was related to intracellular release. It was attenuated by the inositol trisphosphate (IP 3) receptor antagonist 2-aminoethyl diphenylborate, ryanodine, or thapsigargin, but was unaffected by the removal of Ca 2ϩ in external solution. The secondary phase was dependent on extracellular Ca 2ϩ influx. It was unaffected by the voltage-gated Ca 2ϩ channel blocker nifedipine or the nonselective cation channel blockers SKF-96365 and La 3ϩ , but inhibited concentration dependently by millimolar Ni 2ϩ , and potentiated by the Na ϩ /Ca 2ϩ exchange inhibitor KB-R 7943. H2O2 did not alter the rate of Mn 2ϩ quenching of fura 2, suggesting store-and receptor-operated Ca 2ϩ channels were not involved. By contrast, H2O2 elicited a sustained inward current carried by Na ϩ at Ϫ70 mV, and the current was inhibited by Ni 2ϩ . These results suggest that H2O2 mobilizes intracellular Ca 2ϩ through multiple pathways, including the IP3-and ryanodine receptor-gated Ca 2ϩ stores, and Ni 2ϩ -sensitive cation channels. Activation of these Ca 2ϩ pathways may play important roles in ROS signaling in PASMCs.nonselective cation channels; sodium-calcium exchange; ryanodine receptor; inositol trisphosphate receptor; pulmonary arteries REACTIVE OXYGEN SPECIES (ROS) derived from diverse cellular sources, including NADPH oxidase, mitochondrial electron transport chain (ETC), xanthine oxidase, cytochrome P-450, cyclooxygenase, and nitric oxide synthase, are known to play important roles in the regulation of pulmonary and systemic circulation (15). It has been established that vasoconstrictors/ mitogens, such as angiotensin II, serotonin, endothelin-1, platelet-derived growth factor, and tumor necrosis factor-␣, stimulate the production of superoxide and hydrogen peroxide (H 2 O 2 ) to enhance vasoconstriction and activate redox-sensitive gene transcription to promote proliferation, hypertrophy, migration, and survival of vascular smooth muscle cell (14,34,36,58). Recent studies showed that ROS overproduction is associated with pulmonary remodeling and alterations in vascular reactivity observed in chronic hypoxia, and targeted deletion of gp91 phox subunit prevented these changes in knockout mice, suggesting that ROS generated from NADPH oxidase contribute significantly to the pathogenesis of hypoxic pulmonary hypertens...

Important role of PLC-γ1 in hypoxic increase in intracellular calcium in pulmonary arterial smooth muscle cells

“…7). A similar inhibitory effect on H 2 O 2 -induced increase in [Ca 2ϩ ] i has also been observed in isolated rat PASMCs (13). All these data further support our concept that ROS are the important signaling molecules to mediate the hypoxic Ca 2ϩ response in PASMCs by causing PLC-␥1-dependent opening of P 3 Rs.…”

Reactive Oxygen Species Scavengers Improve Voltage‐Gated K+ Channel Function in Pulmonary Arteries of Newborn Pigs with Progressive Hypoxia‐Induced Pulmonary Hypertension

“…39,40 Hence, the ability to trigger intracellular calcium release could be another mechanism by which ROSs contribute to impaired Kv channel function. 41,42 Relevant to this in our study ROS-removing agents did not restore the PASMC Em of hypoxic arteries to control levels. Thus, our findings are consistent with the possibility that ROSs, rather than being an influence on PASMC Em, alter Kv-mediated vascular contraction via changes in Ca 2+ sensitization.…”

Hypoxia Induces Intracellular Ca2+ Release by Causing Reactive Oxygen Species-Mediated Dissociation of FK506-Binding Protein 12.6 from Ryanodine Receptor 2 in Pulmonary Artery Myocytes

“…Exogenous ROS, mimicking hypoxia, also leads to an increase in [Ca 2þ ] i and contraction in PASMCs (8,(16)(17)(18)26). Moreover, application of ryanodine to block RyRs significantly inhibits ROS-evoked increase in [Ca 2þ ] i in PASMCS (8). Supportively, the RyR antagonists dantrolene and ryanodine eliminate or greatly suppress ROS-induced increase in [Ca 2þ ] i and vasoconstriction in isolated PAs (16).…”

“…Numerous reports have provided pharmacological and genetic evidence that mitochondrial ROS is responsible for the hypoxic increase in [Ca 2þ ] i in PASMCs and associated HPV (1,24,27). Exogenous ROS, mimicking hypoxia, also leads to an increase in [Ca 2þ ] i and contraction in PASMCs (8,(16)(17)(18)26). Moreover, application of ryanodine to block RyRs significantly inhibits ROS-evoked increase in [Ca 2þ ] i in PASMCS (8).…”