Nitric oxide preserves XIAP and reduces hypoxia/reoxygenation-induced cardiomyocytes apoptosis via ERK1/2 activation.

The signaling pathways that control the hypoxia/reoxygenation (H/R)-induced cardiomyocyte apoptosis have not been fully defined. In this study, we investigated whether extracellular signal-regulated kinase1/2 (ERK1/2) plays a role in NO's anti-apoptotic effect against H/R injury. Primary cultures of adult rat ventricular myocytes (ARVMs) were exposed to 3 h of hypoxia followed by 30, 60, 90 and 120 min of reoxygenation in presence of a vehicle, NO donor (GSNO, 50 µmol/L) and inhibitors of ERK1/2 (PD98059, 10 µmol/L). GSNO protected the cardiomyocyte from reoxygenation injury, as evidenced by decreased apoptosis, and this protective effect was inhibited by co-treatment with PD98059 during reoxygenation. Consistent with this, when administered with adenoviral vector encoding dominant negative ERK (Ad-dnERK), GSNO's effect was also blocked. Western blotting revealed that GSNO increased the ERK phosphorylation during reoxygenation. Furthermore, H/R-induced activation of caspase-3 and -9 were attenuated by GSNO. Interestingly, X-linked inhibitor of apoptosis protein (XIAP) protein levels decreased in myocytes subjected to reoxygenation, and ERK phosphorylation can improve XIAP expression, which involved inhibiting caspase-3, -7 and -9 activities. Overexpression experiment with adenoviral vector containing constitutively active ERK (Ad-caERK) alone acquired protection against apoptosis triggered by H/R injury and positively regulated XIAP expression compared with control adenovirus (Ad-LacZ). Our data demonstrated that, GSNO's antiapoptotic effect against reoxygenation injury involves ERK signaling pathway. The activation of ERK increased XIAP expression and led to decreased caspase activation.

Milk fat globule epidermal growth factor VIII signaling in arterial wall remodeling.

Arterial inflammation and remodeling, important sequellae of advancing age, are linked to the pathogenesis of age-associated arterial diseases e.g. hypertension, atherosclerosis, and metabolic disorders. Recently, high-throughput proteomic screening has identified milk fat globule epidermal growth factor VIII (MFG-E8) as a novel local biomarker for aging arterial walls. Additional studies have shown that MFG-E8 is also an element of the arterial inflammatory signaling network. The transcription, translation, and signaling levels of MFG-E8 are increased in aged, atherosclerotic, hypertensive, and diabetic arterial walls in vivo as well as activated vascular smooth muscle cells (VSMC) and a subset of macrophages in vitro. In VSMC, MFG-E8 increases proliferation and invasion as well as the secretion of inflammatory molecules. In endothelial cells (EC), MFG-E8 facilitates apoptosis. In addition, MFG-E8 has been found to be an essential component of the endothelial-derived microparticles that relay biosignals and modulate arterial wall phenotypes. This review mainly focuses upon the landscape of MFG-E8 expression and signaling in adverse arterial remodeling. Recent discoveries have suggested that MFG-E8 associated interventions are novel approaches for the retardation of the enhanced rates of VSMC proliferation and EC apoptosis that accompany arterial wall inflammation and remodeling during aging and age-associated arterial disease.