The Association Of The Metalloproteinase-3 Gene Promoter Polymorphism And The Middle Cerebral Arteriostenosis

In Asia, MCA stenosis is the most commonly identified intracranial vascular lesion,which is primary cause of ischemic cerebrovascular disease.Large number of epidemiological studies and animal experiments show that the majority of ischemic cerebrovascular disease are under the control of genetic factors,which is polygenic inheritance disease. Recently,Many studies have reported a relationship between the MMP-3 gene polymorphism and caucasian carotid artery intima-media thickness. Our study focus on the relationship between MMP-3 gene 5A/6A polymorphism and MCA stenosis to clear the role of MMP-3 polymorphism in angiostenosis.The research indicated that the function and metabolism of ECM play a decisive role in the formation of atherosclerosis. ECM is in the continuous dynamic balance of generation and degradation.when it is broken,the organization structure will be damaged and destructed. In the earliest stage of atherosclerosis, smooth muscle cells migrate from the media into the intima and proliferate following the ECM degradation. With time and lesion progression, the function of matrix protein synthesis over degradation lead to matrix deposition and angiostenosis;With the atherosclerosis development,the degration of extracellar matrix results in plaque destabilization and rupture[80].Matrix metalloproteinases (MMPs), a family of Zinc-binding endopeptidases,are proteolytic enzymes whose basic function is degrading the extracellular matrix (ECM) and basement membrane. MMP-3 (stromelysin-1) degrade typeⅡ, IV, IX collagen, laminin, fibronectin, proteoglycans, elastin and gelatin, and also activate other MMPs, such as the MMP-1precrusors can be activated to MMP-1 which degrade type I, III collagen. So MMP-3 play a key role in the activation of MMP.The MMP-3 gene is located on the long arm of chromosome 11 (11q22). The variation of the MMP3 SNP is located at position 1171 bp upstream of the transcriptional initiation site. The results of transient expression experiments demonstrated that 5A expressed approximately 2-fold higher CAT activity than the cells transfected with 6A-CAT. The reduced transcription activity results in low expression on the arterial wall and low proteolytic activity may be beneficial to ECM desposition. Reduced stromelysin -1 expression seems to be associated with more repid progression of atherosclerosis.Common variant in the promoter of the MMP-3 show three genetype: 5A/5A,5A/6A,6A/6A.Method: (1) Subject characteristics: This study included 119 Chinese Han patients with MCA stenosis and 92 healthy corresponding individuals without MCA stenosis in northern.Briefly, between January 2006 and June 2009, subjects who visited the Jilin University First Hospital was diagnosised with MCA stenosis or not by transcanial Doppler (TCD). (2) Genomic DNA was extracted from venous blood by using KI; (3) PCR reaction and PCR product electrophoresis; (4) PCR product was digested in a reaction containing Tth111I enzyme . After digestion, the products were subjected to electrophoresis on a 3% agarose gel stained with ethidium bromide. The 6A alleles were expected as a DNA band with size of 129 bp, the 5A alleles were expected as DNA bands of 97bp and 32 bp, whereas the heterozygotes were expected as a combination of both the alleles (129 bp, 97 bp and 32 bp). (5) Hardy–Weinberg analysis was performed to compare the observed and expected genotype frequencies and alleles frequencies using 2 test. The distribution of the MMP3 SNP and the risk factors in the study groups was compared using 2 test.There was no statistical difference in age distribution between the two groups (P > 0.05). Among individuals with available information, the proportion of smokers , hypertension and diabetes mellitus in MCA stenosis patients was significantly higher than that in healthy controls. The frequencies of 5A and 6A alleles in MMP-3 in patients group were 15.97%, 84.03% and in control group 15.76%,84.24%,with no significant difference between the two groups (P >0.05). The frequencies of 5A/5A, 5A/6A, 6A/6A genetype in MMP-3 in patients group were 0.84%, 30.25%, 68.91% and in control group 0, 31.52%, 68.48%. No significant difference in genotype (5A/ 5A, 5A/ 6A and 6A/ 6A) distribution between middle cerebral arteriostenosis and control groups was observed,either. Compared to 5A/ 5A plus 5A/ 6A genotype,6A/ 6A genotype did not significantly modify the risk of developing middle cerebral arteriostenosis. The result indicated that there is relationship between MCA stenosis and carotid artery intima-media thickness (IMT). Usually 1.1mm≤IMT<1.5mm judged as intimal thickening, IMT≥1.5mm judged to plaque formation.The difference between the patients with IMT≥1.1mm in case group and the control group was significant (P<0.05). It shows IMT thickening may modify susceptibility to MCA stenosis.In summary, we have following conclusion: (1) The metalloproteinase-3 gene promoter polymorphism may be not associated with increased risk of the middle cerebral arteriostenosis; (2) Hypertension,diabetes mellitus and smoking are risk factors of the middle cerebral arteriostenosis; (3) IMT thickening may modify susceptibility to MCA stenosis.As early as 1991, Henney et al investigated that messenger RNA encoding MMP-3 express in human atherosclerotic plaque[96]. Gnasso et al[97] and Rauramaa et al[98] study show that 6A allele is associated with increased carotid intima-media thickness.However,there is few study about the realationship between the MMP-3 promoter 5A/6A polymorphism and intracranial arterial stenosis. MCA stenosis is the most commonly identified intracranial vascular lesion in China.In order to the futher understanding of the pathogenesis of ischemic cerebrovascular disease,we study the association between MMP-3 promoter 5A/6A polymorphism and intracranial arterial stenosis.at the same time.It is helpful to widen the method of treatment and the prevention and early treatment for ischemic cerebrovascular disease. Our results show that there is no association between MMP-3 promoter 5A/6A polymorphism and intracranial arterial stenosis and 6A/ 6A genotype may be not the risk factors of middle cerebral arteriostenosis.In this study,because the sample size is not big enough,we need a larger sample size to verify and futher understanding the role of the MMP-3 polymorphism in MCA stenosis. Ischemic cerebrovascular disease is polygenic inheritance disease.The role of multiple gene polymorphism may not be consistant with a single gene polymorphism.In other words,a single gene polymorphism do not play a key role in MCA stenosis. Additionally,we should consider the difference in race which may be the reason of the different gene distribution.So MMP-3 gene promoter polymorphism may be not a risk factor of MCA stenosis.