Study On The Mechanism Of Atherogenic Effects By Lysophosphatidlycholine

Oxidized low density lipoprotein(ox-LDL)formed by oxidative modification of low density lipoprotein(LDL),is an independent factor causing atherosclerosis.ox-LDL induced atherosclerosis mainly by promoting the proliferation and migration of vascular smooth muscle cells(VSMCs),inducing the apoptosis of vascular endothelial cells(VECs),and motivating the expression of adhesion molecules of VECs,which enabled the monocytes migration and adhesion to form foam cells.However,the underlying mechanisms are still unclear.The present study aimed to explore whether lysophosphatidylcholine(LPC),as the major active substance of ox-LDL,plays a vital role in the ox-LDL-induced atherosclerosis and its mechanism.In this study,we mainly detected the effects of LPC on the proliferation,migration and apoptosis of HASMCs and HUVECs,in combination with animal models.The CCK-8 assay and Neuro Probe AA12 chemotaxis chamber were usedto measure cell proliferation and migration,respectively.Real-time quantitative PCR was used to detect the expression of receptors and signaling molecules in this work.The phosphorylation and expression of proteins are detected by Western blot or immunohistochemistry.Small interfering RNA,inhibitor,and antagonist were used to certify the function of related genes.Our results indicated that:(1)LPC promoted the proliferation and migration of HASMCs.The ki16425,a specific antagonist of LPA1/3 receptor,and PTX,the specific inhibitor of Gi protein,abolished not only LPA,but also the LPC-induced proliferation and migration.The ERK1/2 inhibitor PD98059 caused a significant decrease of LPC-stimulated HASMCs proliferation.SB20580,the inhibitor of p38,and Y27632,the Rho-associated protein kinase inhibitor,caused a significant decrease of LPA-stimulated HASMCs migration.Autotaxin(ATX)was highly expressed in HASMCs and the lyso-PLD was elevated in both HASMCs and the serum of atherosclerotic rabbits.In addition,the content of LPC increased in the serum of model rabbits,and the expression of LPA1 and ATX in vascular tissues of model rabbits were upregulated.(2)We also found that LPC induced the apoptosis of HUVECs.Silencing GPR4 gene by siRNA weakened LPC-induced apoptosis of HUVECs.Western blotting results also showed that LPC induced the increase of Bax expression and the decrease of Bcl-2 expression in HUVECs.However,our results also showed that LPA inhibited the apoptosis of HUVECs and promoted itsproliferation.LPA-induced proliferation of HUVECs was abolished by knocking down LPA1 gene by siRNA,which could also be abolished by PD98059 and GW9662.AG1478,an inhibitor of EGF receptor,also inhibited the effect of LPA.Real-time quantitative PCR showed that LPA increased the expression of bcl-2 and decreased the expression of bax.In summary,the mechanisms of atherogenic actions by LPC were stated as follows.(1)LPC induced the proliferation and migration of HASMCs through the ATX-LPA axis,thereby accelerating the progression of atherosclerosis.LPA1-Gi-ERK pathway and LPA1-Gi-RhoA-p38 pathway mediated the proliferation and migration of HASMCs,respectively.(2)LPC induced the apoptosis of VECs by increasing the expression of Bax and down-regulating the expression of Bcl-2.GPR4 mediated these effects.(3)LPA improved the survival of HUVECs through LPA1-Gi-PPAR signaling pathway.The increase of Bcl-2 expression and the decrease of Bax expression might be involved in this process.(4)LPC inhibited the migration of HUVECs,which was also relevant to the atherogenic effects.Above all,the atherogenic effects of LPC are mainly dependent on the promotion of proliferation and migration of HASMCs and apoptosis of HUVECs.Blocking the signaling pathways induced by LPC is a noval way for preventing and curing atherosclerosis.LPA1 and GPR4 may be the potential drug targets for the prevention and treatment of atherosclerosis.The antagonist of LPA1 may be considered as a potential therapeutic and preventative drug for cardiovasculardisease.