American Journal of Physiology-Lung Cellular and Molecular Physiology · 2013 · 50 citations · 32 references
Acute Lung InjuryInflammatory Lung DiseaseEndothelial CellsLung InflammationLipid PeroxidationInducible Hsp70Redox BiologyOxidative StressInflammationMitochondrial Oxidative StressMitochondrial BiogenesisCell SignalingRedox SignalingMolecular PhysiologyBiochemistryMitochondrial DynamicMedicineVascular BiologyReactive Oxygen SpecieCell BiologyReductive StressMitochondrial FunctionNatural SciencesPhysiologyEndothelial DysfunctionMitochondrial MedicineCellular BiochemistryMetabolismPersistent Pulmonary HypertensionSuperoxide Dismutase 2
Superoxide dismutase 2 (SOD-2) is synthesized in the cytosol and imported into the mitochondrial matrix, where it is activated and functions as the primary antioxidant for cellular respiration. The specific mechanisms that target SOD-2 to the mitochondria remain unclear. We hypothesize that inducible heat shock protein 70 (iHSP70) targets SOD-2 to the mitochondria via a mechanism facilitated by ATP, and this process is impaired in persistent pulmonary hypertension of the newborn (PPHN). We observed that iHSP70 interacts with SOD-2 and targets SOD-2 to the mitochondria. Interruption of iHSP70-SOD-2 interaction with 2-phenylethylenesulfonamide-μ (PFT-μ, a specific inhibitor of substrate binding to iHSP70 COOH terminus) and siRNA-mediated knockdown of iHSP70 expression disrupted SOD-2 transport to mitochondria. Increasing intracellular ATP levels by stimulation of respiration with CaCl2 facilitated the mitochondrial import of SOD-2, increased SOD-2 activity, and decreased the mitochondrial superoxide (O2(·-)) levels in PPHN pulmonary artery endothelial cells (PAEC) by promoting iHSP70-SOD-2 dissociation at the outer mitochondrial membrane. In contrast, oligomycin, an inhibitor of mitochondrial ATPase, decreased SOD-2 expression and activity and increased O2(·-) levels in the mitochondria of control PAEC. The basal ATP levels and degree of iHSP70-SOD-2 dissociation were lower in PPHN PAEC and lead to increased SOD-2 degradation in cytosol. In normal pulmonary arteries (PA), PFT-μ impaired the relaxation response of PA rings in response to nitric oxide (NO) donor, S-nitroso-N-acetyl-penicillamine. Pretreatment with Mito-Q, a mitochondrial targeted O2(·-) scavenger, restored the relaxation response in PA rings pretreated with PFT-μ. Our observations suggest that iHSP70 chaperones SOD-2 to the mitochondria. Impaired SOD-2-iHSP70 dissociation decreases SOD-2 import and contributes to mitochondrial oxidative stress in PPHN.
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