Exosome-Mediated miR-155 Transfer from Smooth Muscle Cells to Endothelial Cells Induces Endothelial Injury and Promotes Atherosclerosis.

The vascular response to pro-atherosclerotic factors is a multifactorial process involving endothelial cells (ECs), macrophages (MACs), and smooth muscle cells (SMCs), although the mechanism by which these cell types communicate with each other in response to environmental cues is yet to be understood. Here, we show that miR-155, which is significantly expressed and secreted in Krüppel-like factor 5 (KLF5)-overexpressing vascular smooth muscle cells (VSMCs), is a potent regulator of endothelium barrier function through regulating endothelial targeting tight junction protein expression. VSMCs-derived exosomes mediate the transfer of KLF5-induced miR-155 from SMCs to ECs, which, in turn, destroys tight junctions and the integrity of endothelial barriers, leading to an increased endothelial permeability and enhanced atherosclerotic progression. Moreover, overexpression of miR-155 in ECs inhibits endothelial cell proliferation/migration and re-endothelialization in vitro and in vivo and thus increases vascular endothelial permeability. Blockage of the exosome-mediated transfer of miR-155 between these two cells may serve as a therapeutic target for atherosclerosis.

Chinese medicine Tongxinluo reduces atherosclerotic lesion by attenuating oxidative stress and inflammation in microvascular endothelial cells.

Oxidative stress and inflammation are the important pathological basis of atherogenesis. So, attenuating oxidative stress and inflammation has a very important significance in the prevention and treatment of atherosclerosis. The aim of present study was to investigate whether anti-atherosclerotic effect of Tongxinluo (TXL), a compound traditional Chinese medicine, is related to its anti-oxidation and anti-inflammation in human cardiac microvascular endothelial cells (HCMEC). We found that TXL treatment significantly reduced serum lipid levels and atherosclerotic plaque formation of apoE-deficient mice, and improved endothelial cell function as evidenced by increased expression of CD31 and eNOS. TXL pretreatment could abrogate the up-regulation of ROS and MDA induced by C16. Further experiments showed that the anti-oxidative effect of TXL may be related to inhibiting the expression of p22(phox), p47(phox) and HO-1 in HCMECs. We also found that TXL could inhibit the release of IL-1ß and TNFα induced by C16, which is mediated by inhibiting the expression and activation of NF-κB. In conclusion, TXL decreases atherosclerotic plaque formation and improves endothelial cell function by inhibiting oxidative stress and inflammation in HCMECs. This finding provides a new molecular mechanism for the anti-atherosclerotic effect of TXL.

Chinese medicine Tongxinluo increases tight junction protein levels by inducing KLF5 expression in microvascular endothelial cells.

Tongxinluo (TXL) is a compound prescription formulated according to the meridian theory of traditional Chinese medicine. It may play an important role in cardiovascular protection by improving endothelial cell function. The aim of present study was to investigate whether endothelial protection with TXL is related to its regulation of tight junction protein expression. Human cardiac microvascular endothelial cells (HCMECs) were cultured and treated with 10(-7) mol l(-1) angiotensin II (Ang II) and the different doses of TXL; the expression of tight junction proteins occludin, claudin, VE-cadherin and beta-catenin was determined by Western blotting and real-time PCR. Gain-of-function and loss-of-function of Krüppel-like factor 5 (KLF5) were carried out in HCMEC transfected with either KLF5 adenovirus pAd-KLF5 or siRNA specific for KLF5. Angiotensinogen transgenic mice were treated with TXL by oral administration of TXL of 0.75 g kg(-1) day(-1) , and immunohistochemical staining was performed with antioccludin, anticlaudin, anti-VE-cadherin, antibeta-catenin and anti-KLF5 antibodies. Ang II treatment significantly reduced the expression of tight junction proteins occludin, claudin, VE-cadherin and beta-catenin in cultured HCMECs. TXL pretreatment could abrogate the down-regulation of these tight junction proteins induced by Ang II. Ang II treatment also decreased KLF5 expression at the mRNA and protein levels; TXL pretreatment markedly reversed the inhibitory effect of Ang II on KLF5 expression. Gain-of-function and loss-of-function of KLF5 showed that KLF5 mediated the expression of tight junction proteins in HCMECs. TXL-enhanced expression of the tight junction proteins was mediated by KLF5. In angiotensinogen transgenic mice, TXL also increased the tight junction protein levels by inducing KLF5 expression. Chinese medicine TXL increases tight junction protein levels by inducing KLF5 expression in microvascular endothelial cells.