Hypoxia modulates the cellular signaling in cultured ratlung micro vascular endothelial cells

Abstract

Acute and chronic oxidative stress is one of the causative factors for endothelial dysfunction; however, itsunderlying mechanism is still unknown. In this study, alterations in signaling proteins in hypoxia-induced rat lung microvascular endothelial cells (RLMEC)were identifiedin vitro. RLMEC were maintained in hypoxia (2% O₂) for 24 hours and 48 hours, as well as in hyperoxia (20% O₂) and normoxia (5% O₂). Some cells were incubated in normoxia following exposure to hypoxia. Western Blotwas performed to determine expression of the signaling proteins. The data were statisticallyanalyzed. Hypoxia induced the up-regulation of p38 MAPK, Cox-2, Bax/Bcl-2, AT1, IL-6 and down-regulatedeNOS in RLMEC compared to normoxia. Additionally, RLMEC incubated at hypoxic condition for 48 hours caused significantly higher expressions of apoptotic and stress signaling proteins compared to 24hour incubation. Thesignaling was reversed in cells that were exposed to 24hourshypoxic condition followed by 24hours innormoxia; however, it was not reversed after a 48 hour hypoxia induction. Conclusion: Hypoxia induces up-regulation of stress and apoptotic signaling in cultured RLMEC that may indicate endothelial dysfunction. This in vitro system can be used as a tool to study hypoxia-induced endothelial dysfunction in diseased condition.