Abstract
INTRODUCTION: We aimed to explore the role of Apelin-13 in resisting oxidation, inflammation as well as apoptosis and its underlying mechanisms of action using a model of nicotine-induced H9c2 cardiomyocyte injury. METHODS: H9c2 cardiomyocytes were randomly divided into control, nicotine, nicotine + Apelin-13, and Apelin-13 groups. Cell counting kit-8 assay was conducted to determine the cell viability. Interleukin (IL)-6, superoxide dismutase, tumor necrosis factor-alpha (TNF-α), glutathione peroxidase (GSH-Px), IL-β, catalase (CAT), IL-8, lactate dehydrogenase (LDH), and malondialdehyde (MDA) levels were examined. A 2',7'-dichlorodihydrofluorescein diacetate assay was conducted to measure the intracellular reactive oxygen species (ROS) level. The morphology of apoptotic cardiomyocytes was observed by 4',6-diamidino-2-phenylindole staining. Western blotting was employed to measure the protein expressions of apoptotic factors B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X (Bax). Apoptosis was quantified using Annexin V/propidium iodide staining. RESULTS: Exposure of H9c2 cardiomyocytes to 10 μM nicotine significantly reduced cell viability and increased LDH release, oxidative stress (elevated MDA and ROS levels with decreased superoxide dismutase, GSH-Px, and CAT activities), pro-inflammatory cytokines (IL-6, TNF-α, IL-1β, IL-8), and apoptotic markers (increased Bax with decreased Bcl-2 expression, along with nuclear condensation) (p<0.05). In contrast, treatment with 2 μM Apelin-13 significantly alleviated these deleterious effects, enhancing cell viability, restoring antioxidant enzyme activities, reducing oxidative and inflammatory responses, and inhibiting apoptosis (p<0.05). CONCLUSIONS: Nicotine induction increases the oxidative stress and apoptotic capacity of H9c2 cardiomyocytes, but Apelin-13 protects H9c2 cardiomyocytes against nicotine-induced apoptosis and oxidative stress.