Simulated hypoxia modulates P2X7 receptor function in mice peritoneal macrophages

The inflammatory focus is similar to the tumor microenvironment, which contains a complex milieu with im-mune cells and macrophages. The accumulation of cells promotes local pH and O2 tension decline (hypoxia). Local O2 tension decline activates hypoxia-inducible factor alpha and beta (HIF-1 alpha and HIF-1 beta adenosine triphosphate (ATP) release. ATP activates the P2X7 receptor and modulates ischemic/hypoxic conditions. Similarly, alpha 1 alpha may regulate P2X7 receptor expression in the hypoxic microenvironment. Therefore, we investigated P2X7 receptor function under simulated hypoxic conditions by pretreating peritoneal macrophages with mitochondrial electron transport chain complex inhibitors (simulated hypoxia). Treatment with mitochondrial electron transport chain complex inhibitors until three hours of exposure did not cause LDH release. Additionally, mitochondrial electron transport chain complex inhibitors increased ATP-induced P2X7 receptor function without being able to directly activate this receptor. Other P2 receptor subtypes do not appear to participate in this mechanism. Simulated hypoxia augmented HIF-1 alpha levels and suppressed HIF-1 alpha and P2X7 receptor antagonists. Similarly, simulated hypoxia increased ATP-induced dye uptake and inhibited HIF-1 alpha antagonists. Another factor activated in simulated hypoxic conditions was the intracellular P2X7 receptor regulator PIP2. Treatment with HIF-1 alpha agonists increased PIP2 levels and reversed the effects of HIF-1 alpha and P2X7 receptor antagonists. Additionally, the improved ATP-induced dye uptake caused by the simulated hypoxia stimulus was inhibited by P2X7 receptor and PIP2 antagonists. Therefore, simulated hypoxia may augment P2X7 receptor activity for a pathway dependent on HIF-1 alpha and PIP2 activation.