| (Pro)renin receptor (PRR) is the co-receptor of prorenin and renin, which was found in2002. After combined with tis ligands, it could enhanced the enzymatic activation ofrenin and prorenin, which promotes the generation of angiotensin II (Ang II), therebyehnhancing the renin-angiotensin system (RAS) activity. This will raise the bloodpressure, promote the expression of inflammatory cytokines, which contributes to thedevelopment of atherosclerosis. But recent studies found that PRR could be activated inan AngII-independent manner, triggering the intracellular signal transduction cascade.High level of prorenin could promote the expression of inflammatory cytokines andproliferation in human vascular endothelial cells and podocytes via PRR.Vascular smooth muscle cells (VSMCs) were mainly located in the middle layer ofblood vessels, which played a key role in the development of atherosclerosis. Undervarious atherogenic pathological conditions, VSMCs could migrate to thesubendothelial layer, proliferate excessively, and promote the formation of fibrous capof atherosclerotic plaque. Further, the cell type would switch into the secretory type,promote the release of inflammatory cytokines, attract inflammatory cell infiltration,promote the formation of foam cells. Meanwhile, apoptosis of VSMCs becameabnormal, leading to apoptosis/proliferation imbalance. All these promote the formationof atherosclerosis.In our previous studies, high glucose, lipoprotein A, etc, could affect the expression ofPRR, and induce inflammation and oxidative stress in human vascular endothelial cells. Indicating that PRR might be involved in the formation and development ofatherosclerosis. But another key factor, oxidative low-density lipoprotein’s (ox-LDL)effect on the expression of PRR in different kinds of vascular cells, and its subsequentrole in atherosclerosis remains unclear.Thus, in this study, we observed the effect of ox-LDL on the expression of PRR incultured human aortic smooth muscle cells (HASMCs), explored the impact of PRR onthe HASMCs’ function, further, discussed the possible effect of PRR on the occurrenceand development of atherosclerosis.MethodsCultured HASMCs were pretreated with10-5M valsartan and10-5M PD123319toblock AngII type1and type2receptor. The pretreated HASMCs were cultured with100μg/L ox-LDL for0,1,2,4,6,12,14h. The expression of PRR’s mRNA and proteinwere detected by quantitative real-time PCRs and western blot. The time point of themaximum expression of PRR was chosen as the intervention time in the next step. Thepretreated HASMCs were cultured with0,25,50,100,150,200,300μg/L ox-LDL for acertain time (referred above). The expression of PRR’s mRNA and protein weredetected by quantitative real-time PCRs and western blot. The concentration of ox-LDLof the maximum expression of PRR was chosen as the intervention time in the next step.Then small RNA interference was used to down-regulate the expression of PRR. Andthe pretreated HASMCs were divided into3groups: control group, ox-LDL group andox-LDL+siRNA group. The boyden chamber assay was used to assess the migration ofHASMCs. And The phosphorylation levels of p38mitogen-activated protein kinase(p38MAPK) were detected by western blot.Results1. PRR was expression abundantly in HASMCs, mainly distributed in cytoplasm andcell membrance.2. When cultured with100μg/L ox-LDL, the expression of PRR was graduallyincreased, peaked at6h (P<0.05), then slightly decreased, showing a time-dependentmanner. 3. When the HASMCs were cultured with different concentration of ox-LDL for6h,the expression of PRR was gradually increased, peaked at50μg/L (P<0.05), thenslightly decreased, showing a concentration-dependent manner.4. Comparing with the control group, when cultured with50μg/L ox-LDL for6h, themigration of HASMCs was significantly increased (P<0.05); but after the PRR wasknocked out by siRNA, the migration of HASMCs was decreased significantly down tothe baseline (P<0.05).5. Comparing with the control group, the expression of phosphorylate p38MAPK ofox-LDL group has no significant difference; and there as no significant differencebetween the ox-LDL group and the ox-LDL+siRNA group.Conclusions1. PRR was expressed in HASMCs.2. Ox-LDL could up-regulate the expression of PRR in a time-and concentration-dependent manner in HASMCs.3. Ox-LDL could induce the migration of HASMCs via PRR, which acted as achemokine.4. P38MAPK might be involved in the migration of HASMCs induced by ox-LDL viaPRR; and this pathway played a key role at the upstream. |
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