The Mechanism Of PCSK9 Promoting The Progression Of Calcific Aortic Valve Disease

Objective: Calcific aortic valve disease(CAVD)is a common,potentially fatal valvular disease.Previous studies have shown that development of CAVD is associated with elevated serum lipids and lipoprotein(a)[Lp(a)] levels.Proprotein convertase subtilisin/kexin type 9(PCSK9)is a serine protease that binds to low-density lipoprotein receptor(LDL-R),leading to their accelerated degradation and increased low-density lipoprotein cholesterol(LDL-C)levels.However,little is known of the relationship between PCSK 9 and the incidence of CAVD.We have investigated the possible association between plasma proprotein convertase subtilisin/kexin type 9(PCSK9)and the incidence and severity of calcific aortic valve disease(CAVD)in part I.And then we explored the relationship between valvular local proprotein convertase subtilisin/kexin type 9(PCSK9)levels and inflammatory factors in CAVD patients undergoing aortic valve replacement(part II).Methods: Part I is a prospective,cross sectional study in which we have enrolled patients with and without(controls)aortic valve calcification diagnosed by transthoracic echocardiography and dual source computed tomography(DSCT)scan.Aortic valves calcification scores were calculated from DSCT scans and patients were graded: grade 1,no calcification;grade 2,mildly calcified;grade 3,moderately calcified;grade 4,heavily calcified.Plasma PCSK9 levels were measured using an enzyme-linked immunosorbent assay.In part II,we enrolled 59 CAVD patients and16 controls who had experienced aortic valve replacement in Tianjin Chest Hospital by transthoracic echocardiography and dual source computed tomography between March 2015 and December 2015.Immunofluorescence(IF)staining was used to determine the protein levels of PCSK9,Monocyte/Macrophage marker antibody(MOMA2)and alpha-smooth muscle actin(?-SMA)in aortic valve tissue.m RNA expression levels of PCSK9,low density lipoprotein receptor(LDLR),actin alpha 2(ATCA2),tumor necrosis factor alpha(TNF-?),and interleukin-6(IL-6)were determined by quantitative Real-time fluorescence polymerase chain reaction(q RT-PCR).Results: Forty patients were grade 1(controls),32 were grade 2,48 were grade 3 and32 were grade 4 in part I.Plasma levels of PCSK9 were significantly different between the four groups and the highest value was observed in the patients with grade2 calcification.Only low-density lipoprotein cholesterol and Lp(a)were associated with the severity of CAVD.Regression analysis showed that age,Lp(a)and PCSK9 were independent predictors of CAVD.In part II,PCSK9 can be detected in aortic valve.As compared to the control group,PCSK9,MOMA-2 and ?-SMA in human calcific valve was significantly higher by IF(1.75 vs.1,1.67 vs.1 and 1.25 vs.1;all p <0.01).The PCSK9 was significantly and positively correlated with the MOMA2 and ?-SMA(r = 0.342,p < 0.01;r=0.277,p < 0.01).There were significantly upregulation in valvular m RNA expressions of PCSK9,ATCA2 and TNF-?(3.03 vs.1,4.00 vs.1,4.75 vs.1;all p < 0.01).LDLR were downregulated in CAVD patients(1 vs.1.58;p < 0.01).There was no significant difference in IL-6 between the two groups.The expression of PCSK9 in calcified aortic valve was up-regulated,and there was a correlation between PCSK9 and TNF-?.Conclusion: Data from the cross sectional study(part I)in a small sample of patients showed that plasma PCSK9 was correlated with the presence of CAVD but not its severity.Plasma LDL cholesterol was significantly increased in CAVD patients,and there was a correlation between LDL cholesterol and aortic calcification score.Lipoprotein(a)is one of the independent risk factors of CAVD.PCSK9 was also found in the aortic valve locally,and the expression of PCSK9 in CAVD was higher than that of the normal valve(part II).The expression level of MOMA2 and ACTA in calcified valve was up-regulated and the expression of LDL receptor was down-regulated.Valvular local PCSK9 might be involved in the pathogenesis of CAVD by regulating its inflammatory response.