| AIM:Cardiovascular diseases cause great harm to human health.The important pathological mechanism is atherosclerosis. In the formation of atherosclerosis, macrophages play an important role and oxidized low density lipoprotein(ox-LDL) is a main factor of the foam cell formation. Scavenger receptor CD36 and scavenger receptor A1(SR-A1) are closely associated with the formation of foam cells. CD36 and SR- A1 on macrophages play a quantitatively important role in the uptake of ox-LDL, which is a well-known risk factor for the development of AS. Lipid oxidation has strong cytotoxic effect, which leads to the foam cell apoptosis and necrosis and formation of lipid core in atheromatous plaque. Apolipoprotein A- I(apoA-I) is a major protein component of HDL. L-4 F and D-4 F, mimetic peptides of apoA-I can spur macrophage cholesterol outflows, inhibit mice AS caused by lipid disorders. However, whether D-4 F can inhibit the lipid accumulation in macrophages by regulating the expression of scavenger receptor has not been reported. This work was designed to explore the role of endoplasmic reticulumstress(ERS) in the SR-A1 expression induced by ox-LDL and whether D-4F could inihit the macrophage-derived foam cell formation by attenuating ERS-mediated SR-A1 upregulation, and to further clarify the mechanisms underlying the macrophage-derived foam cell formation and anti-atherogenic functions of D-4 F.METHODS:RAW264.7 cells were pretreated with PBA(20 mmol/L) for 30 min and then treated with 50 mg/L ox-LDL for 12 h or stimulated with 2 mg/L TM or TG for 4 h. In addition, RAW264.7 cells were incubated with TM( 0.5, 1 and 2 mg/L)for 4 h or treated with TM(2 mg/L)for 1, 2 and 4 h. RAW264.7 cells were pretreated with D-4F(12.5, 25 and 50 mg/L) or s D4F(50 mg/L) for 1 h or PBA(5 mmol/L) for 30 min, followed by treatment with ox-LDL(100 mg/L) for 12 h. In addition, the cells were pretreated with D4F(50 mg/L)or s D4F(50 mg/L)for 1 h, and then stimulated with 2 mg/L TM for 4 h. The viability of the cells was measured by MTT assay;The content of TC was measured using a tissue/cell TC assay kit. The protein levels of SR-A1 and GRP78 were analyzed by Western blotting and the mRNA levels of SR-A1 and GRP78 were analyzed by quantitative real-time PCR. The fluorescence intensity of Dil-ox-LDL in the cells was detected by a multifunctional microplate reader.RESULTS:Compared with the control group, the TC levels in the macrophages of the ox- LDL increased significantly(P < 0.01), while the PBA can significantly inhibit the ox- LDL induced the accumulation of cholesterol in the macrophages. Compared with ox- LDL group,its content is reduced by 32.0%(P < 0.05). Ox- LDL group compared with control group, cell SR- A1, GRP78 protein levels increase significantly(P < 0.01), while the PBA significantly inhibit the raise of SR- A1 induced by ox- LDL. Compared with the ox- LDL group it reduced by 48.4%(P < 0.05); GRP78 protein expression was 39.3% lower, but no statistical significance(P = 0.057). Compared with the control group, the SR- A1 mRNA level of ox- LDL group raised obviously;it is 1.81 times(P < 0.05); In ox- LDL induced SR-A1 transcriptin level, PBA has no affect;Compared with ox- LDL group comparison, the mRNA level has no statistical difference(P > 0.05). TM significantly raised macrophage SR- A1 protein levels, and there is time and the concentration dependence.When TM has handed 2h,the height will summit(P < 0.01 or P < 0.05); TM’s different concentrations(0.5, 1 and 2 mg/L) although can make SR- A1 mRNA level shows ascendant trend, but statistical difference(P > 0.05). TM can increase the macrophages ingest ox-LDL, TM(2 mg/L) is especially significant(P < 0.01). The PBA + TM treatment group compared with TM treatment group, ox- LDL intake and SR- A1, GRP78 protein levels were reduced obviously, TM group is 51.3%, 53.9% and 60.0% respectively(P < 0.05). Under the effect of TG macrophages,SR-A1,GRP78 protein levels rise significantly, but the PBA + TG group of SR- A1, GRP78 protein levels were obviously reduced, is TG treatment group were 47.5%, 58.3%(P < 0.05). D- 4 f can obviously reduce the ox- LDL macrophages caused by injury and the accumulation of cholesterol in the cell. Ox- LDL significantly raised macrophage SR- A1, GRP78 expression level, and the simulation peptide D- 4 f significantly inhibited the change, and the concentration dependence. D- 4 f for TM induced SR- A1, GRP78 protein levels and macrophages ingest ox- LDL have obvious inhibitory effect.Conclusion:ERS in ox- LDL induced SR- A1 increases plays a key role, ERS in ox-LDL induced SR- A1 raised plays an important role.It absorbs more ox- LDL and promots the formation of foam cells. Endoplasmic reticulum stress can mediate ox- LDL inducing macrophage scavenger receptor raising A1 process,and apolipoprotein AI D- 4 f can obviously inhibit ox- LDL induced SR- A1 increasing. Simulation peptide D- 4 f can inhibit the SR- A1 expression, and reduce the damage of macrophages caused by ox- LDL and the accumulation of cholesterol in the macrophage, the mechanism may be related to inhibition of GRP78 mediated signal pathway in ERS. |
PDF Full Text Request