AIMS: The initiation of hypoxic pulmonary vasoconstriction (HPV) involves an increase in cytosolic calcium ([Ca(2+)](i)) in pulmonary artery (PA) smooth muscle cells (PASMCs). Both the processes depend on extracellular Ca(2+). Extracellular Ca(2+) can be sensed by extracellular calcium-sensing receptor (CaSR). This study aims at determining whether CaSR is pivotal in the initiation of HPV. RESULTS: Experiments were performed in cultured PASMCs, isolated PAs, and rats including CaSR knockdown preparations. Both hypoxia and H(2)O(2) equivalent to the level achieved by hypoxia increased [Ca(2+)](i) in an extracellular Ca(2+)-dependent manner in PASMCs, and this was inhibited by CaSR knockdown or its negative allosteric modulator, Calhex231. Hypoxia-increased H(2)O(2) generation was diminished by mitochondria depletion. Mitochondria depletion abolished hypoxia-induced [Ca(2+)](i) increase (HICI), which was reversed by H(2)O(2) repletion. CaSR knockdown or Calhex231, however, prevented the reversible effect of H(2)O(2). HICI was abolished by catalase-polyethylene glycol (PEG-Catalase), not superoxide dismutase-polyethylene glycol (PEG-SOD) pretreatment, attenuated by ryanodine receptor3-knockdown or inhibition of store-operated Ca(2+) entry. HPV in vitro and in vivo was inhibited by Calhex231 and by CaSR knockdown. INNOVATION: A novel mechanism underlying HPV is revealed by the role of CaSR in orchestrating reactive oxygen species and [Ca(2+)](i) signaling. CONCLUSIONS: The activation of mitochondrial H(2)O(2)-sensitized CaSR by extracellular Ca(2+) mediates HICI in PASMCs and, thus, initiates HPV.
AIMS: The initiation of hypoxic pulmonary vasoconstriction (HPV) involves an increase in cytosolic calcium ([Ca(2+)](i)) in pulmonary artery (PA) smooth muscle cells (PASMCs). Both the processes depend on extracellular Ca(2+). Extracellular Ca(2+) can be sensed by extracellular calcium-sensing receptor (CaSR). This study aims at determining whether CaSR is pivotal in the initiation of HPV. RESULTS: Experiments were performed in cultured PASMCs, isolated PAs, and rats including CaSR knockdown preparations. Both hypoxia and H(2)O(2) equivalent to the level achieved by hypoxia increased [Ca(2+)](i) in an extracellular Ca(2+)-dependent manner in PASMCs, and this was inhibited by CaSR knockdown or its negative allosteric modulator, Calhex231. Hypoxia-increased H(2)O(2) generation was diminished by mitochondria depletion. Mitochondria depletion abolished hypoxia-induced [Ca(2+)](i) increase (HICI), which was reversed by H(2)O(2) repletion. CaSR knockdown or Calhex231, however, prevented the reversible effect of H(2)O(2). HICI was abolished by catalase-polyethylene glycol (PEG-Catalase), not superoxide dismutase-polyethylene glycol (PEG-SOD) pretreatment, attenuated by ryanodine receptor3-knockdown or inhibition of store-operated Ca(2+) entry. HPV in vitro and in vivo was inhibited by Calhex231 and by CaSR knockdown. INNOVATION: A novel mechanism underlying HPV is revealed by the role of CaSR in orchestrating reactive oxygen species and [Ca(2+)](i) signaling. CONCLUSIONS: The activation of mitochondrial H(2)O(2)-sensitized CaSR by extracellular Ca(2+) mediates HICI in PASMCs and, thus, initiates HPV.
Authors: Krishna C Penumatsa; Deniz Toksoz; Rod R Warburton; Andrew J Hilmer; Tiegang Liu; Chaitan Khosla; Suzy A A Comhair; Barry L Fanburg Journal: Am J Physiol Lung Cell Mol Physiol Date: 2014-08-15 Impact factor: 5.464
Authors: Michelle J Connolly; Jesus Prieto-Lloret; Silke Becker; Jeremy P T Ward; Philip I Aaronson Journal: J Physiol Date: 2013-06-17 Impact factor: 5.182
Authors: Aya Yamamura; Hisao Yamamura; Qiang Guo; Adriana M Zimnicka; Jun Wan; Eun A Ko; Kimberly A Smith; Nicole M Pohl; Shanshan Song; Amy Zeifman; Ayako Makino; Jason X-J Yuan Journal: Circ Res Date: 2013-01-08 Impact factor: 17.367