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Endothelial dysfunction and apoptosis have key roles in the initiation and progression of atherosclerosis (AS). AS has been demonstrated to be associated with a high‑fat diet, which may increase endothelial permeability and apoptosis; however, the exact mechanisms underlying the development of AS remain poorly understood. MicroRNAs (miRNAs) are vital for the regulation of cardiovascular disease, and dysregulated miRNAs have been implicated in AS. The present study investigated whether miRNA (miR)‑126 regulates high‑fat diet‑induced endothelial permeability and apoptosis by targeting transforming growth factor β (TGFβ), a secreted protein that controls cellular proliferation and apoptosis. In the present study, apolipoprotein E (apoE)‑/‑ mice were fed a high‑fat diet in order to establish a model of AS. Mice were subcutaneously injected with a miR‑126 mimic, a miR‑126 antagomir or control miRNA. Reverse transcription‑quantitative polymerase chain reaction was used to assess miR‑126 expression, and a fluorometric assay was used to evaluate caspase‑3 activity. The effects of miR‑126 on the endothelial permeability of the aortic intima were also explored. Western blotting and immunohistochemical analysis were used to investigate the effects of miR‑126 on B‑cell lymphoma‑2 (Bcl‑2) and transforming growth factor (TGF) β protein expression levels. Furthermore, a luciferase assay was performed to verify whether TGFβ may be a direct target gene of miR‑126. In apolipoprotein E‑knockout mice, a high‑fat diet reduced miR‑126 expression and induced apoptosis as determined by the upregulation of caspase‑3 activity. A miR‑126 antagomir increased endothelial permeability and apoptosis in mice fed a high‑fat diet. By contrast, an miR‑126 mimic attenuated endothelial permeability and apoptosis. The reduction in miR‑126 was associated with a reduction in protein expression levels of Bcl‑2 and an increase of TGFβ in mice fed a high‑fat diet. In addition, the present study demonstrated that miR‑126 reduced TGFβ expression following binding to the 3'‑untranslated region of TGFβ mRNA. The current study demonstrated a role for miR‑126 in AS and identified TGFβ as a direct target of miR‑126. Furthermore, the present study demonstrated that miR‑126 contributed to endothelial permeability and apoptosis, and suggested that the downregulation of TGFβ may be involved in the molecular mechanisms underlying the actions of miR‑126. miR‑126 may therefore have potential as a novel therapeutic target for the treatment of AS. [ABSTRACT FROM AUTHOR]

Melatonin (MLT) is an endogenous indole compound with numerous biological activities that has been associated with atherosclerosis (AS). In the present study, rabbits were used as an AS model in order to investigate whether MLT affects endothelial cell permeability, myosin light chain kinase (MLCK) activity and MLCK expression via the mitogen-activated protein kinase (MAPK) pathway. Expression and activity of MLCK were measured using western blot analysis, quantitative polymerase chain reaction, immunohistochemistry and γ-32P-adenosine triphosphate incorporation. Endothelial permeability was detected using rhodamine phalloidin fluorescence staining. The phosphorylation of extracellular regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 in endothelial cells were also analyzed using western blot analysis. Atheromatous plaques were formed in rabbits with a high cholesterol diet; however, following treatment with MLT, the number and areas of atheromatous plaques were significantly reduced. In addition, MLT treatment reversed the increase of MLCK activity and expression that occurred in rabbits with high cholesterol intake. Furthermore, levels of phosphorylated ERK, JNK and p38 decreased following MLT treatment. In conclusion, the results of the present study indicated that AS may be associated with increased MLCK expression and activity, which was reduced following treatment with MLT. The mechanism of action of MLT was thought to proceed via modulating MAPK pathway signal transduction; however, further studies are required in order to fully elucidate the exact regulatory mechanisms involved. [ABSTRACT FROM AUTHOR]