Study Of Aspirin On Increasing Stability Of Atherosclerotic Plaque And Its Underlying Mechanisms

Objective: To investigate the effects of aspirin on anti-atherosclerosis and increasingthe atherosclerotic plaque stability, and approach its underlying mechanisms in vivoand in vitro, and observed which dosage of aspirin can exert best effect.Methods: In vivo, the hyperlipidemic atherosclerotic model was generated in maleNew Zealand rabbits that were given high fat diet and abrasion of the abdominal aortaendothelial cells. These rabbits were then treated with aspirin 5-20mg/kg for 4 weeks.At experimental end, the plaques were evoked into rupture by drugs. Areas ofthrombosis on atherosclerotic aorta were determined by image analysis, morphologiccharacter of plaque rupture was determined by electron and light microscope. SerumTC, TG, HDL-C were measured with colorimetric method, platelet aggregationinduced by ADP or arachidonic acid was determined with turbidimetric method. Invitro, THP-1 cells were cultured and then differentiated to macrophages, subsequently,stimulated them by ox-LDL. Then, cells were incubated in RPMI 1640 plus aspirin12.5-200μg/ml for 24h, respectively. The levels of MMP-2 and MMP-9 in supernatantwere measured with ELISA, the mRNA expression of MMP-1, MMP-2, MMP-9,TIMP-1, TIMP-2, PPARα, PPARγ, was examined with RT-PCR, the protein expressionof NF-κB was detected by western blot.Results: (1) Aspirin was able to decrease serum TC, LDL-C and ratio ofLDL-C/HDL-C, increase serum HDL-C in atherosclerotic rabbits. These effects weredose dependent. (2) Aspirin could inhibit platelet aggregation induced by ADP orarachidonic acid, but the inhibition of aspirin 20mg/kg against platelet aggregationwas weakened. (3) Aspirin at does of 5-10mg/kg was able to inhibit thrombosis onatherosclerotic plaque, and the effect of 5mg/kg is better. (4) Aspirin could inhibitfoam cell formation and aggregation in plaque, keep the integrity of fiber cap andshoulder area. (5) The level of MMP-2 and MMP-9 in supernatant were notablydecreased by aspirin in ox-LDL-stimulated macrophages, the mRNA expression ofMMP-1, MMP-2 and MMP-9 was also decreased, but the mRNA expression of TIMP-1 and TIMP-2 was significantly increased, and All of these effects were thebest when concentrations of aspirin was at 50μg/ml or 100μ/ml. (6) Aspirin couldalso inhibit the protein expression of NF-κB via the activation of PPARα/γmRNAexpression.Conclusion: Aspirin was able to increase the stability of atherosclerotic plaque, thiseffect was associated with regulation of blood lipid, and reduction of macrophagesand foam cells in atherosclerotic plaque. Importantly, aspirin could inhibit the proteinexpression of NF-κB via the elevation of PPARα/γmRNA expression, consequently,reduction of MMP production and release. In addition, aspirin was able to increase themRNA expression of TIMP-1 and TIMP-2 and accordingly decrease the activities ofMMP-1, MMP-2 and MMP-9. 50μg/ml or 100μg/ml was the best dosage in theseeffects.