The Contractile Response of Lung Pericytes to Reactive Oxygen Metabolites
Regulation of pericyte contractility by reactive oxygen metabolites (ROM) may play a significant role in contributing to the regulation of microvascular fluid hemodynamics during inflammation, sepsis, and the adult respiratory distress syndrome (ARDS). ROM, which are known mediators in the pathophysiological response of sepsis, have been shown to induce both relaxation and contraction in large blood vessels. The purpose of this study was to test the effects of ROM on lung pericyte contractility and whether these effects could be attenuated by antioxidants. Cultured pericytes were exposed to hydrogen peroxide and pyrogallol at 10 µM, 100 µM, and 1 mM, while the antioxidant effects of catalase (100 µM), super oxide dismutase (SOD; 100 µM), and vitamin E pretreatments (1 mM) were also quantified. Both hydrogen peroxide and pyrogallol induced dose-dependent relaxation at 10 minutes. However, at 30 minutes dose-dependent contraction was measured. Catalase completely attenuated both physiological responses, while SOD did not have an effect on either. Vitamin E, however, only partially attenuated contractions induced at 30 minutes but had no effect on the relaxation at 10 minutes. These results suggest that ROMs are capable of inducing both relaxation and contraction in lung pericytes, implying two separate time dependent pathways by which contractility is regulated.