The role of protein kinase A in hypoxia-induced PC-12 cell death.

[摘要] Hypoxia is characterized by an inadequate oxygen supply to the tissues inproportion to their metabolic needs, and is a primary factor in traumatic CNSinjury, strokes, cardiopulmonary diseases, and obstructive sleep apnea. ThecAMP-dependent protein kinase (PKA) has been attributed a role as an antiapoptotickinase as well as a pro-apoptotic signal. Thus the role of PKA inhypoxia-induced cell survival is currently unclear.We show here that hypoxia induces cell death in WT PC-12 cells,pheochromocytoma cells used as a model of the oxygen-sensitive carotid bodyglomus cells. The onset of cell death following 24 hours of severe, sustainedhypoxia also correlated with an increase in oxidative stress and a drop in ATPlevels. Inactivation of PKA in the 123.7 PC-12 cell line prevented the hypoxiainducedROS surge, energy depletion, and cell death. PKA activity thuscontributes to hypoxia~induced cell death in WT cells via enhanced ROSproduction and energy depletion, but was not shown to playa role in theregulation of cellular antioxidant mechanisms. 123.7 cells had lower levels of hypoxia-induced glucose utilization andlactate release than WT cells, thus PKA appears to stimulate increases inglycolytic flux during hypoxia. Mitochondrial potentials were higher in 123.7cells than in WT cells, indicating that PKA inhibits mitochondrial metabolism.Furthermore, the expression of COX IV was decreased by hypoxic exposure inboth cell types, but was significantly greater in 123.7 cells. The greaterexpression of COX IV may allow 123.7 cells to maintain mitochondrial electronflow and energy production under drastically reduced oxygen conditions.Antioxidant treatment blocked hypoxia-induced cell death, but was notsufficient to prevent depletion of ATP or to modulate the metabolic pathways.Thus, this finding indicates that hypoxia-induced metabolic regulation and energydepletion occur independently of oxidative stress.Consequently, the PKA signaling pathway appears to contribute tohypoxia-induced cell death through its regulatory effects on oxidative stress andmetabolic pathways. Modulation of the PKA signaling pathway could providenovel therapeutic strategies to improve cellular adaptation and recovery in themany pathologies characterized by periods of hypoxia.

[发布机构] University:University of Louisville;Department:Physiology and Biophysics

[效力级别] Hypoxia

[关键词] Protein kinase A;Hypoxia;Metabolism;Energy;Cell death;Reactive oxygen species;PC-12