Antiapoptotic effects of GLP-1 in murine HL-1 cardiomyocytes

Abstract

Activation of apoptosis contributes to cardiomyocyte dysfunction and death in diabetic cardiomyopathy. The peptide glucagon-like peptide-1 (GLP-1), a hormone that is the basis of emerging therapy for type 2 diabetic patients, has cytoprotective actions in different cellular models. We investigated whether GLP-1 inhibits apoptosis in HL-1 cardiomyocytes stimulated with staurosporine, palmitate, and ceramide. Studies were performed in HL-1 cardiomyocytes. Apoptosis was induced by incubating HL-1 cells with staurosporine (175 nM), palmitate (135 μM), or ceramide (15 μM) for 24 h. In staurosporine-stimulated HL-1 cardiomyocytes, phosphatidylserine exposure, Bax-to-Bcl-2 ratio, Bad phosphorylation (Ser136), BNIP3 expression, mitochondrial membrane depolarization, cytochrome c release, caspase-3 activation, DNA fragmentation, and mammalian target of rapamycin (mTOR)/p70S6K phosphorylation (Ser2448 and Thr389, respectively) were assessed. Apoptotic hallmarks were also measured in the absence or presence of low (5 mM) and high (10 mM) concentrations of glucose. In addition, phosphatidylserine exposure and DNA fragmentation were analyzed in palmitate- and ceramide-stimulated cells. Staurosporine increased apoptosis in HL-1 cardiomyocytes. GLP-1 (100 nM) partially inhibited staurosporine-induced mitochondrial membrane depolarization and completely blocked the rest of the staurosporine-induced apoptotic changes. This cytoprotective effect was mainly mediated by phosphatidylinositol 3-kinase (PI3K) and partially dependent on ERK1/2. Increasing concentrations of glucose did not influence GLP-1-induced protection against staurosporine. Furthermore, GLP-1 inhibited palmitate- and ceramide-induced phosphatidylserine exposure and DNA fragmentation. Incretin GLP-1 protects HL-1 cardiomyocytes against activation of apoptosis. This cytoprotective ability is mediated mainly by the PI3K pathway and partially by the ERK1/2 pathway and seems to be glucose independent. It is proposed that therapies based on GLP-1 may contribute to prevent cardiomyocyte apoptosis.

AMPK activation by glucagon-like peptide-1 prevents NADPH oxidase activation induced by hyperglycemia in adult cardiomyocytes

“…For example, GLP-1 treatment, either GLP-1 agonist or DPP-4 inhibitors, limits ischemic injury in perfused hearts in intact animals (8,34,52) as well as in cardiomyocytes (33). The data suggest that the phosphoinositide 3-kinase-Akt pathway is involved in this protective effect of GLP-1.…”

Cardiovascular Actions of Incretin-Based Therapies

“…20 Similarly, GLP-1 (200 nmol/L for 24 hours) activated phosphatidylinositol-3 kinase/Akt and ERK in HL-1 atrial cardiomyocytes, reducing the extent of apoptosis in response to staurosporine treatment; these cytoprotective effects were attenuated by the phosphatidylinositol-3 kinase inhibitor, wortmannin, or the ERK inhibitor, UO126. 25 Although these findings support the notion that native GLP-1 and degradation-resistant exendin-4 exert direct actions on cardiomyocytes, whether these actions are mediated by the classical GLP-1R is often not clearly determined. Furthermore, concentrations of native GLP-1 or exendin-4 used in these experiments are considerably higher (3 nmol/L to 200 nmol/L) than those observed physiologically after nutrient ingestion (20-30 pmol/L) or pharmacologically in therapeutic studies.…”

Exendin-4 protects endothelial cells from lipoapoptosis by PKA, PI3K, eNOS, p38 MAPK, and JNK pathways

“…By contrast, prolonged exposure of the HCAECs to exendin-4 further augmented NO production, a crucial factor in regulation and coordination of endothelial function and apoptosis (Calles-Escandon & Cipolla 2001). GLP1 and its derivates have previously been assigned an anti-apoptotic role in murine HL-1 cardiomyocytes (Ravassa et al 2011), pancreatic b-cells (Cunha et al 2009, and neuronal cells (Li et al 2009). Very recently, it was also shown that exendin-4 protects pancreatic b-cells against lipoapoptosis by interfering with the JNK signaling pathway.…”

“…GLP1 has also been described as an anti-apoptotic factor in different cells, including cardiomyocytes (Ravassa et al 2011), neuronal cells (Li et al 2009), and vein endothelial cells (Schisano et al 2012, Shiraki et al 2012. The aim of our study was to investigate the putative protective effect of exendin-4 and GLP1 against lipoapoptosis of HCAECs and attempt to address the pathways involved in imparting such an effect.…”