Regression Of Spontaneous Calcified Atherosclerotic Plaque In ApoE-/-Mice And Its Potential Mechanism

Objective To investigate the effect of simvastatin on atherosclerotic calcificationand its potential mechanism.Methods24male ApoE-/-mice ona C57BL/6J genetic background and12maleC57BL/6J mice were selected when they were8-week-old.24male ApoE-/-micewere randomly divided into model group and simvastatin group(n=12).12maleC57BL/6J mice were regarded as control group. All mice received adaptive feeding inthe animal center for two weeks after which they werefeed by a high-fat dietinstead.After nine weeks,animals were treated with intragastric administration asfollows:Control group and model group received0.2ml PBS buffer per day for8weeks; Simvastatin group received simvastatin(20mg/kgdissolved in0.2ml PBS bufferfor intragastric administration) every day for8weeks.The body weight of mice wererecorded everyday during the whole experiment.They were sacrificed and their aortaand aortic sinus were separated for further use.The aorta of mice were stained with oilred O and aortic sinus paraffin sections were processed with HE, Von kossa, TUNELand immunohistochemical staining to observe plaque size,atheroscleroticcalcification,apoptosis and expression of related proteins.Results Body weight of the three groups increased gradually over time.By theend of the experiment, the mean body weightof control group gained to(38.2±3.1)g,model group gained to(31.0±1.6) g and simvastatin group gained to (30.5±2.6) g.Compared to model group,simvastatin group was not statistically significant (P>0.05).Serumlipid parameters of TG, TC, LDL-C, HDL-C in the model group weresignificantly higher, compared withcontrol group andmodel group(P<0.01).HDL-C/LDL-C value ofsimvastatin group was0.17±0.005, whichrepresented a slight increase compared with model group(0.15±0.003), but the difference was not statistically significant (P=0.09). Percentage of aortic plaque areaofmodel group and simvastatin group were (54.50±15.41)%and (33.69±9.72)%,which simvastatin groupsignificantly reduced (P <0.05).And the mean plaquearea of aortic sinus of simvastatin group was significantly less than model group (P<0.05).No calcificationwas found in control group.In addition, percentage ofcalcification area of simvastatin group(2.33±0.73)%was lower than model group(10.87±2.41)%(P <0.05).A certain apoptosis was observed in each group.Apoptosisrate of control group was (30.90±1.75)%,model group (66.43±4.05)%andsimvastatin group (47.01±5.94)%, respectively. Apoptosis rate of model groupwassignificantly higher than control group(P <0.01).And it was significantly reducedinsimvastatin groupcompared with the model group(P <0.05). Protein expressions inaortic sinus of the three groups of GRP78, CHOP and Caspase12were observed invarying degrees. The highest expressionlevels of the three proteins wereobserved inmodel group, which were significantly decreased in simvastatin group.Conclusion Simvastatin may reduce endoplasmic reticulum stress-mediated apoptosisinvolved atherosclerotic calcification.