ABSTRACT
Hexarelin is a synthetic growth hormone-releasing peptide that exerts cardioprotective effects. Regulation of autophagy is known to be cardioprotective so this study examined the role of autophagy and potential regulatory mechanisms in hexarelin-elicited anti-cardiac hypertrophic action in cardiomyocytes subjected to hypertrophy. H9C2 cardiomyocytes were subjected to hypertrophy by angiotensin-II (Ang-II). Autophagic light chain-3 (LC3) and cytoskeletal proteins were determined by immunofluorescence assay. Autophagy was also detected using monodansylcadaverine (MDC) for autophagic vacuole visualization and Cyto-ID staining for autophagic flux measurement. Molecular changes were analysed by Western blotting and qRT-PCR. Apoptosis was evaluated using flow cytometry and TUNEL assay. ATP content and CCK-8 assay were used in assessing enhanced cell survival whilst oxidative stress was analysed by measuring malondialdehyde(MDA) and superoxide dismutase(SOD) levels. Ang-II induced cardiomyocyte hypertrophy, oxidative stress, apoptosis and decreased cell survival, all of which were significantly suppressed by hexarelin treatment which also enhanced autophagy in hypertrophic H9C2 cells. Furthermore, inhibition of hexarelin induced autophagy by 3-methyladenine (3MA) abolished the anti-hypertrophic function of hexarelin and also abrogated the protection of hexarelin against cell survival inhibition and apoptosis. Conversely, the application of autophagy stimulator rapamycin in H9C2 hypertrophic cells inhibited apoptosis, cell survival and reduced cell size as well. Additionally, hexarelin regulated the upstream signalling of autophagy by inhibiting the phosphorylation of mammalian target of rapamycin(mTOR). We propose that hexarelin plays a novel role of attenuating cardiomyocyte hypertrophy and apoptosis via an autophagy-dependent mechanism associated with the suppression of the mTOR signalling pathway.
Subject(s)
Angiotensin II/metabolism , Autophagy/drug effects , Cardiomegaly/metabolism , Cardiomegaly/prevention & control , Myocytes, Cardiac/drug effects , Oligopeptides/pharmacology , Animals , Autophagosomes/drug effects , Cardiomegaly/chemically induced , Cell Line , Cell Survival , Metabolic Networks and Pathways , Myocytes, Cardiac/metabolism , Myocytes, Cardiac/pathology , Oxidative Stress , Protective Agents/pharmacology , Rats , Signal Transduction , TOR Serine-Threonine Kinases/metabolismABSTRACT
Chemokines and their receptors participate in the development of cancers by enhancing tumor cell proliferation, angiogenesis, invasion, metastasis and penetration of tumor immune cells. It remains unclear whether CXC chemokine ligand 4 (CXCL4)/CXC chemokine receptor 3-B (CXCR3-B) can be used as an independent molecular marker for establishing prognosis for breast cancer patients. We evaluated CXCL4 and CXCR3-B expression in 114 breast cancer tissues and 30 matched noncancerous tissues using immunohistochemistry and western blot, and determined the correlation between their expression and clinicopathologic findings. We observed that breast cancer tissues express CXCL4 strongly and CXCR3-B weakly compared to noncancerous tissues. Strong CXCL4 expression was detected in 94.7% and weak CXCR3-B expression was detected in 78.9% of the tissues. Therefore, CXCL4/CXCR3-B might play a crucial role in breast cancer progression. We found no significant correlation between CXCL4 and age, tumor stage, tumor grade or TNM stage. CXCR3-B was associated significantly with tumor grade. Moreover, the Chi-square test of association showed that the expression of CXCL4/CXCR3-B might be an independent prognostic marker for breast cancer. Therefore, we suggest that CXCR3-B is an indicator of poor prognosis and may also be a chemotherapeutic target.
