Epac is Required for GLP-1R-Mediated Inhibition of Oxidative Stress and Apoptosis in Cardiomyocytes

Abstract

Although the cardioprotective effects of glucagon-like peptide-1 and its analogs have been reported, the exact mechanisms of the glucagon-like peptide-1 receptor (GLP-1R) signaling pathway in the heart are still unclear. Activation of the GLP-1R has been shown to increase cAMP levels, thus eliciting protein kinase A- and exchange protein activated by cAMP (Epac)-dependent signaling pathways in pancreatic β-cells. However, which pathway plays an important role in the antioxidant and antiapoptotic effects of GLP-1R activation in the heart is not known. In this study, we demonstrated that stimulation of GLP-1Rs with exendin-4 attenuated H2O2-induced reactive oxygen species production and increased the synthesis of antioxidant enzymes, catalase, glutathione peroxidase-1, and manganese superoxide dismutase that is dependent on Epac. Additionally, exendin-4 has an antiapoptotic effect by decreasing a number of apoptotic cells, inhibiting caspase-3 activity, and enhancing the expression of antiapoptotic protein B-cell lymphoma 2, which is mediated through both protein kinase A- and Epac-dependent pathways. These data indicate a critical role for Epac in GLP-1R-mediated cardioprotection.

Enhanced AMPA Receptor Trafficking Mediates the Anorexigenic Effect of Endogenous Glucagon-like Peptide-1 in the Paraventricular Hypothalamus

“…However, in addition to the effects on PKA, it is also possible that activation of GLP-1R affects the activity of exchange proteins activated by cAMP (EPAC) (Mangmool et al, 2015) to facilitate GluA1 trafficking. Contrary to this hypothesis, unlike the effects of H-89, application of ESI-09, an EPAC inhibitor, did not block either Exn4 induced membrane GluA1 trafficking or GluA1 phosphorylation (Figure S4, C&D).…”

Functional and cardioprotective effects of simultaneous and individual activation of protein kinase A and Epac

“…Recent work using neonatal rat isolated cardiomyocytes showed that stimulation of glucagon‐like peptide‐1 receptor by exendin‐4 mediated a cytoprotective effect, which was associated with both PKA and Epac‐dependent pathways (Mangmool et al, 2015). Our results, however, do not suggest a simple additive cardioprotective effect of PKA and Epac but a coordinated synergistic action of these two cAMP‐related pathways, particularly considering the absence of any protective effect of Epac activation alone and a relatively weak cardioprotective effect of 6‐Bnz‐induced PKA activation.…”

Thai Fruits Exhibit Antioxidant Activity and Induction of Antioxidant Enzymes in HEK-293 Cells

“…The intracellular antioxidant activities of the crude extract of Thai fruits were quantified using a fluorescent probe dichlorodihydrofluorescein (DCF) diacetate (Sigma-Aldrich) to estimate the intracellular ROS production in the cell as previously described [20]. HEK-293 cells were seeded in a 12-well plate (5 × 10 4  cells/well) or 35-mm glass bottomed dishes (1 × 10 5  cells/dish) and treated with Thai fruit extracts (10 and 100  μ g/ml) for 12 h. After 12 h, the cells were then incubated with 100  μ M of H 2 O 2 for 2 h and washed once with phosphate buffered saline (PBS), pH 7.4.…”

“…Protein expression of antioxidant enzymes was performed by Western blotting as previously described [20]. Following stimulation, cells were washed once with PBS and solubilized in lysis buffer containing 20 mM Tris-HCl, pH 7.4, 0.8% Triton X-100, 150 mM NaCl, 2 mM EDTA, 10% glycerol, 100  μ M PMSF, 5  μ g/ml aprotinin, and 5  μ g/ml leupeptin.…”