Subacute Mild Hypoxia Increases Histamine-stimulated Calcium Oscillation Frequency in Pulmonary Artery Endothelial Cells / 生物化学与生物物理进展

ABSTRACT

Calcium oscillation may regulate gene transcription in a frequency-decoding manner during agonist stimulation,which provides an indicator of transcription level in cells. To determine whether persistent exposure to hypoxia may sensitize or blunt cell response to histamine, the effects of 24 h subacute mild hypoxia on histamine-stimulated calcium oscillation frequency were examined in pulmonary artery endothelial cells (PAECs). The results are (1) 24 h subacute mild hypoxia significantly increased the histamine-stimulated calcium oscillation frequency in PAECs. The averaged frequency of calcium oscillation in posthypoxic PAECs was significantly higher than that in normoxic ones. (2) NADPH oxidase inhibitor, diphenylene iodonium chloride (DPI, 10 μmol/L), abolished histamine-stimulated calcium oscillations both in normoxic and posthypoxic PAECs. (3) Xanthine oxidase inhibitor, oxypurinol (100 μmol/L), did not affect the calcium oscillation kequency in normoxic PAECs. However, it significantly decreased the elevation of calcium oscillation frequency in posthypoxic PAECs. These results demonstrated that, during pulmonary disease related to persistent hypoxia,PAECs become more sensitive to histamine. During histamine stimulation, NADPH oxidase plays a critical role in generating calcium oscillations, while xanthine oxidase may contribute to, at least in part, the increase of calcium oscillation frequency in posthypoxic PAECs.