GH-Releasing Hormone Promotes Survival and Prevents TNF-α-Induced Apoptosis and Atrophy in C2C12 Myotubes

Abstract

Skeletal muscle atrophy is a consequence of different chronic diseases, including cancer, heart failure, and diabetes, and also occurs in aging and genetic myopathies. It results from an imbalance between anabolic and catabolic processes, and inflammatory cytokines, such as TNF-α, have been found elevated in muscle atrophy and implicated in its pathogenesis. GHRH, in addition to stimulating GH secretion from the pituitary, exerts survival and antiapoptotic effects in different cell types. Moreover, we and others have recently shown that GHRH displays antiapoptotic effects in isolated cardiac myocytes and protects the isolated heart from ischemia/reperfusion injury and myocardial infarction in vivo. On these bases, we investigated the effects of GHRH on survival and apoptosis of TNF-α-treated C2C12 myotubes along with the underlying mechanisms. GHRH increased myotube survival and prevented TNF-α-induced apoptosis through GHRH receptor-mediated mechanisms. These effects involved activation of phosphoinositide 3-kinase/Akt pathway and inactivation of glycogen synthase kinase-3β, whereas mammalian target of rapamycin was unaffected. GHRH also increased the expression of myosin heavy chain and the myogenic transcription factor myogenin, which were both reduced by the cytokine. Furthermore, GHRH inhibited TNF-α-induced expression of nuclear factor-κB, calpain, and muscle ring finger1, which are all involved in muscle protein degradation. In summary, these results indicate that GHRH exerts survival and antiapoptotic effects in skeletal muscle cells through the activation of anabolic pathways and the inhibition of proteolytic routes. Overall, our findings suggest a novel therapeutic role for GHRH in the treatment of muscle atrophy-associated diseases.

Molecular Mechanisms of Obesity-Induced Osteoporosis and Muscle Atrophy

“…It has been identified from several studies that elevated levels of TNF-α are associated with increased muscle atrophy and apoptosis (Gallo et al, 2015 ). Obesity and T2DM are associated with a chronic inflammatory response that is characterized by increased production of TNF-α and other proinflammatory cytokines (Steinberg et al, 2006 ).…”

Growth hormone-releasing hormone attenuates cardiac hypertrophy and improves heart function in pressure overload-induced heart failure

“…In addition to regulating the release of pituitary growth hormone (GH), GH-releasing hormone (GHRH) exerts many peripheral effects ( 5 , 6 ), displaying autocrine and paracrine actions and regulating the survival and proliferation of different cell types. Accordingly, the expression of both GHRH and GHRH receptors has been demonstrated in extrapituitary sites ( 5 ), including CMs ( 7 – 9 ), skeletal myoblasts, and myotubes ( 10 ). We have recently demonstrated the antiapoptotic action of GHRH in H9c2 cardiac cells and adult rat ventricular myocytes (ARVMs), through signaling mediated by the GHRH receptor (GHRH-R) and activation of cAMP/protein kinase A (PKA) ( 7 ).…”

The Mineralocorticoid Agonist Fludrocortisone Promotes Survival and Proliferation of Adult Hippocampal Progenitors

“…Total RNA extraction from AHP cells and reverse transcription to cDNA from 3 μg RNA were performed as previously described ( 39 ). Nine microliters of cDNA were amplified by standard polymerase chain reaction (PCR) in a 50 μl volume using AmpliTaq Gold Polymerase in a GeneAmp PCR System (Perkin Elmer, Milano, Italy) as described ( 10 ).…”

“…Immunoblot analysis was performed as previously described ( 10 , 39 ). Proteins (50 μg) were resolved in 11% SDS-PAGE and transferred to a nitrocellulose membrane; after blocking with 1% BSA in Tris-buffered saline with 0.1% Tween for 2 h at room temperature, membranes were incubated overnight at 4°C with the specific antibody (P-CREB, P-Akt, P-GSK-3β, P-p70S6K, and P-Tau) (dilution 1:1000).…”