Endothelial Cells Response To Monomeric C-reactive Protein In A Polarized Manner

Endothelial cells are natural barriers between circulating blood and the vascular smooth muscle,regulating blood vessel contraction and blood clotting,and involved in inflammation and the secretion of inflammatory factors.Thus,they are widely used in the study of cardiovascular physiology and pathology.C-reactive protein is an important molecule associated with cardiovascular diseases and inflammation.In recent years more and more data suggest,besides pentameric CRP,monomeric CRP plays an active role in inflammation of cardiovascular diseases;while many conflicting reports from experiments in vitro and in vivo exist on the activity of CRP and mCRP.For instance,low dosage subcutaneous injection of CRP for a long period induced atherosclerosis in ApoE-/-mice,an early atherosclerosis animal model,whereas injection mCRP could partially prevent plaque formation and induce the secretion of anti-inflammatory factor IL-10.In contrast,in vitro cell culture experiments revealed low concentration of mCRP could significantly up-regulate inflammatory factors in endothelial cells and neutrophile granulocyte,thus displayed strong pro-inflammatory effect.mCRP present in tissue-associated form,while CRP existed in the blood as a free plasma protein.In this study,CRP and mCRP were injected intravenously into C57BL mice and mCRP was soon cleared out from circulating blood.The different spatial distributions of CRP and mCRP might have direct impact on their respective physiological effects.Therefore,we cultured endothelial cells on porous filters,which formed polarized cell monolayer facing apically(toward blood)and basolaterally(toward tissue).According to our experiments,the presence of mCRP on apical side of endothelial cells induced high expression of pro-inflammatory factors and related mRNA,which was greatly reduced when it was on the basolateral side.Furthermore,after incubation of endothelial cells with cholesterol extraction reagent,which caused the destruction of lipid rafts on the plasma membrane,the polarized response of mCRP was effectively abolished.Since lipid rafts distributed unequally on apical and basolateral plasma membrane of endothelial cells,it was likely this asymmetric distributions led to the polarized effect of mCRP.Finally,we found Bay11-7082(an inhibitor of NF-κB),U73122(an inhibitor of PLC)and SB20358(an inhibitor of p38 MAPK)could inhibit the response of human coronary artery endothelial cells to mCRP to different extents and affect mCRP-induced polarized responses of HCAEC.mCRP activated human coronary artery endothelial cells via PLC/p38 MAPK/NF-κB mediated pathways.Asymmetric distribution of lipid rafts on apical and basolateral membrane of endothelial cells may lead to the polarized response of endothelial cells upon mCRP induction.Our study helps explain the conflicted roles of mCRP played in pro-inflammation or anti-inflammation and aggravation or alleviation of atherosclerosis from researches in vivo and in vitro.