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.