Reinioside C Inhibits Adhesion Of Monocytes To Endothelial Cells Induced By Asymmetric Dimethylarginine

BACKGROUND: Adhesion of circulating monocytes toendothelium plays an important role in early events of atheroscleroSis.Asymmetric dimethylarginine (ADMA), an endogenous nitric oxidesynthase (NOS) inhibitor, is a risk factor of atherosclerosis. In vitro studieshave demonstrated that ADMA can induce apoptosis in endothelial cells,but there are few studies about the pro-inflammatory effect of ADMA.Recently, it was reported that ADMA can increase the levels of monocytechemoattract protein-1 (MCP-1) and tumor necrosis factor-α(TNF-α) inendothelial cells and increase adhesion of monocytes to endothelial cells.But there is not reported that ADMA induced monocyte-endothelial cellsadhesion and cytokines production in monocytes.Atherosclerosis is an chronic inflammatory disease. TNF-αandslCAM-1, are important cytokines involved in the development ofatherosclerosis. There is emerging evidence that the reactive oxygenspecies (ROS) sensitive-activation of NF-κB plays an important role in thetranscriptional activation of TNF-αand slCAM-1.Polygala fallax Hemsl., a commonly used Chinese medicinal herb, has been used to treat some diseases such as infective inflammation andhypercholesterolemia. It was reported that many Chinese medicinal herbssuch as xanthones have the effects of anti-atherosclerosis by down-regulating the ADMA levels in various cell lines. But there are sincerestudies on depressing the pro-inflammatory effect of ADMA. Further-more, previous study has shown that reinioside C could inhibit theelevated expression of lectin-liked oxidized low density lipoproteinreceptor (LOX)-1 mRNA and protein induced by ox-LDL in the humanumbilical vein endothelial cells (HUVECs). Therefore, we hypothesizedthat reinioside C can inhibit the TNF-αand slCAM-1 production inducedby ADMA. In the present study we will study the effect of reinioside Con adhesion of monocytes to endothelial cells and cytokines expressionsinduced by ADMA and its mechanisms.METHODS: TNF-αand slCAM-1 levels in culture medium wasassayed by enzyme linked immunosorbent assay (ELISA). Changes inintracellular ROS levels were determined by measuring the oxidativeconversion of cell permeable 2', 7'-dichlorofluorescein diacetate(DCFH-DA) to fluorescent dichlorofluorescein (DCF) in fluorospectro-photometer, and the NF-κB DNA-binding activity was determined byEMSA.RESULTS: 1) ADMA increased adhesion of monocytes toendothelial cells in a concentration-dependent manner and elevated the expression of TNF-αand sICAM-1 of THP-1 cells in concentration-andtime-dependent manner; 2) ADMA (30μM) time-dependently increasedintracellular ROS production and activated NF-κB activity, which weresuppressed by L-arg (0.5 mM) and PDTC (10μM); 3) reinioside Cconcentration-dependently inhibited the increased adhesion of monocytesto endothelial cells and reduced TNF-αand sICAM-1 elevation inducedby ADMA (30μM); Moreover, reinioside C reduced intracellular ROSelevation and NF-κB activation induced by ADMA (30μM).CONCLUSIONS: 1. ADMA can induce adhesion of monocytes toendothelial cells via increasing TNF-αand sICAM-1 production, whichwas related to activation of intracellular ROS/NF-κB pathway. 2.reinioside C could attenuate the increase of monocyte-endothelial cellsadhesion and elevation of TNF-αand sICAM-1 levels induced byADMA via inhibiting activation of ROS/NF-κB pathway in THP-1 cells.