U0126 attenuates ischemia/reperfusion-induced apoptosis and autophagy in myocardium through MEK/ERK/EGR-1 pathway.

Myocardial ischemia is one of the main causes of sudden cardiac death worldwide. Depending on the cell type and stimulus, ERK activity mediates different anti-proliferative events, such as apoptosis, autophagy, and senescence. The aim of this study was to determine the protective effect of 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene (U0126), an ERK kinase inhibitor, on myocardial ischemia/reperfusion (I/R) injury and the mechanisms involved. An I/R model was established in vivo in C57BL/6 mice and in vitro using mouse cardiomyocytes, respectively. To evaluate the protective effects of U0126 on I/R injury, we measured the myocardial infarct area, apoptosis, and autophagy. Our data indicated that pretreatment with U0126 significantly reduced the infarct area caused by I/R. Moreover, U0126 reduced the caspase-3 activity and the number of TUNEL-positive cardiomyocytes, which together indicate decreased apoptosis. Additionally, U0126 remarkable reduced the level of Beclin-1 and LC3 and increased p62 expression, which indicates that U0126 suppressed H/R-induced autophagy. Furthermore, the relationship between U0126 and MEK/ERK pathway activation in H/R-induced cardiomyocytes was also investigated. U0126 ameliorated H/R injury through inhibition of the MEK/ERK pathway and by suppressing in the downstream EGR-1 expression. Together, our research suggests that U0126 may protect against H/R injury by preventing H/R-induced myocardium apoptosis and autophagy via the MEK/ERK/EGR-1 pathway, and may be a potential therapeutic approach for attenuating myocardial I/R injury.

[Effects of rosiglitazone on cholesterol contents and scavenger receptor class B type I expression in RAW264.7 foam cells].

OBJECTIVE: To observe the effect of rosiglitazone on the content of cholesterol and expressions of Acy-coenzyme A: cholesterol acyltransferase 1 (ACAT-1) and scavenger receptor class B type I (SR-BI) in RAW264.7 macrophage-derived foam cells and explore the anti-atherosclerotic mechanism of rosiglitazone. METHODS: RAW264.7 macrophages were incubated with oxidized low-density lipoproteins (ox-LDL) or with both ox-LDL and rosiglitazone (5, 10, or 20 µmol/L). Oil red O staining was used to observe the formation of foam cells, and cholesterol oxidase was used to determine the content of cellular cholesterol contents. Western blotting was used observe the expressions of ACAT-1 and SR-BI in RAW264.7 foam cells. RESULTS: Compared with the control cells, RAW264.7 macrophage-derived foam cells showed significantly increased contents of total cholesterol and free cholesterol (P<0.01) and ACAT-1 expressions (P<0.05) with mildly increased SR-BI expression (P>0.05). Rosiglitazone treatments significantly lowered the contents of total cholesterol and free cholesterol (P<0.05), decreased the expression of ACAT-1 (P<0.05), and increased SR-BI expression (P<0.05) in the foam cells in a dose-dependent manner. CONCLUSION: Rosiglitazone can decrease the contents of total and free cholesterol, down-regulate ACAT-1 expression and up-regulate SR-BI expression in the foam cells produce the anti-atherosclerotic effect.