The role of miRNA-29b1 on the hypoxia-induced apoptosis in mammalian cardiomyocytes.

Cardiomyocyte apoptosis is a complex biological process involving the interaction of many factors and signaling pathways. In hypoxic environment, cardiomyocytes may trigger apoptosis due to insufficient energy supply, increased production of oxygen free radicals, and disturbance of intracellular calcium ion balance. The present research aimed to investigate the role of microRNA-29b1 (miR-29b1) in hypoxia-treated cardiomyocytes and its potential mechanism involved. We established an in vitro ischemia model using AC16 and H9C2 cardiomyocytes through hypoxia treatment (1% O2, 48 h). Cell apoptosis was evaluated by flow cytometry using Annexin V FITC-PI staining assay. Moreover, we used Western blot and immunofluorescence analysis to determine the expression of Bcl-2, Bax caspase-3 and Cx43 proteins. We found that miR-29b1 protected AC16 and H9C2 cells from hypoxia-induced injury as evidence that miR-29b1 attenuated the effects of hypoxia treatment on AC16 and H9C2 cell apoptosis after hypoxia treatment. In conclusion, our findings suggest that miR-29b1 may have potential cardiovascular protective effects during ischemia-related myocardial injury.

Low shear stress-induced blockage of autophagic flux impairs endothelial barrier and facilitates atherosclerosis in mice.

Atherosclerosis preferentially occurs in areas with low shear stress (LSS) and oscillatory flow. LSS has been demonstrated to correlate with the development of atherosclerosis. The sphingosine 1-phosphate receptor 1 (S1PR1), involving intravascular blood flow sensing, regulates vascular development and vascular barrier function. However, whether LSS affects atherosclerosis via regulating S1PR1 remains incompletely clear. In this study, immunostaining results of F-actin, ß-catenin, and VE-cadherin indicated that LSS impaired endothelial barrier function in human umbilical vein endothelial cells (HUVECs). Western blot analysis showed that LSS resulted in blockage of autophagic flux in HUVECs. In addition, autophagy agonist Rapamycin (Rapa) antagonized LSS-induced endothelial barrier dysfunction, whereas autophagic flux inhibitor Bafilomycin A1 (BafA1) exacerbated it, indicating that LSS promoted endothelial barrier dysfunction by triggering autophagic flux blockage. Notably, gene expression analysis revealed that LSS downregulated S1PR1 expression, which was antagonized by Rapa. Selective S1PR1 antagonist W146 impaired endothelial barrier function of HUVECs under high shear stress (HSS) conditions. Moreover, our data showed that expression of GAPARAPL2, a member of autophagy-related gene 8 (Atg8) proteins, was decreased in HUVECs under LSS conditions. Autophagic flux blockage induced by GAPARAPL2 knockdown inhibited S1PR1, aggravated endothelial barrier dysfunction of HUVECs in vitro, and promoted aortic atherosclerosis in ApoE-/- mice in vivo. Our study demonstrates that autophagic flux blockage induced by LSS downregulates S1PR1 expression and impairs endothelial barrier function. GABARAPL2 inhibition is involved in LSS-induced autophagic flux blockage, which impairs endothelial barrier function via downregulation of S1PR1.

Bivalirudin Attenuates Thrombin-Induced Endothelial Hyperpermeability via S1P/S1PR2 Category: Original Articles.

Aims: To explore the role of the Sphingosine 1-Phosphate (S1P)/Receptor2 (S1PR2) pathway in thrombin-induced hyperpermeability (TIP) and to test whether bivalirudin can reverse TIP via the S1P-S1PRs pathway. Methods and Results: Using western blot, we demonstrated that Human umbilical vein endothelial cells (HUVECs) that were cultured with 2 U/ml thrombin showed significantly increased S1PR2 expression while S1PR1and three kept unchanged. Such increment was attenuated by JTE-013 pretreatment and by presence of bivalirudin. Exposure of 2 U/ml of thrombin brought a higher level of S1P both intracellularly and extracellularly within the HUVECs by using ELISA detecting. Thrombin induced S1P and S1PR2 increment was restored by usage of PF543 and bivalirudin. Bivalirudin alone did not influenced the level of S1P and S1PR1,2, and S1PR3 compare to control group. As a surrogate of cytoskeleton morphology, phalloidin staining and immunofluorescence imaging were used. Blurry cell edges and intercellular vacuoles or spaces were observed along thrombin-exposed HUVECs. Presence of JTE-013 and bivalirudin attenuated such thrombin-induced permeability morphological change and presence of heparin failed to show the protective effect. Transwell chamber assay and probe assay were used to measure and compare endothelial permeability in vitro. An increased TIP was observed in HUVECs cultured with thrombin, and coculture with bivalirudin, but not heparin, alleviated this increase. JTE-013 treatment yielded to similar TIP alleviating effect. In vivo, an Evans blue assay was used to test subcutaneous and organ microvascular permeability after the treatment of saline only, thrombin + saline, thrombin + bivalirudin, thrombin + heparin or thrombin + JTE-013. Increased subcutaneous and organ tissue permeability after thrombin treatment was observed in thrombin + saline and thrombin + heparin groups while treatment of bivalirudin and JTE-013 absent this effect. Conclusion: S1P/S1PR2 mediates TIP by impairing vascular endothelial barrier function. Unlike heparin, bivalirudin effectively blocked TIP by inhibiting the thrombin-induced S1P increment and S1PR2 expression, suggesting the novel endothelial protective effect of bivalirudin under pathological procoagulant circumstance.