| Background:Acute coronary syndrome (ACS), an intensive disease of coronary heart disease (CHD), is a common killer for the elderly, and affects the health of them seriously. ACS is a clinical syndrome which includes unstable angina pectoris (UAP), ST segment elevation myocardial infarction and non ST segment elevation myocardial infarction. Nowadays, scholars believe that the the ulcer, rupture and thrombus of vulnerable plaque (VP) in coronary is the main pathophysiology of ACS. VP refers to the atherosclerotic lesion which is unstable or susceptible to thrombosis. There are three characteristics for VP, which are thin fibrous cap, large lipid core and considerable macrophage infiltrating.Inflammation plays an important role in the development of ACS, inflammatory cells and their proinflammatory mediators can make the fibrous cap of plaque become thinner, lipid core become larger, then the plaque becomes VP which is easy to break to cause ACS. A lot of proinflammatory mediators involve in the development of VP, including CRP, IL-6, TNF and so on. Recently, more and more scholars pay attention to the relationship between the newly discovered inflammatory mediators and VP, and interleukin-18(IL-18) is the most representative.IL-18 is a multifunctional pro-inflammatory mediator which plays a key role in the inflammation, it is mainly produced by cells such as macrophages, kuffer cells. There are lots of polymorphisms in IL-18 gene, the promoter functional polymorphisms-137G/C and-607C/A, were studied the most, which regulate the expression of IL-18. Studies have shown that the promoter polymorphisms-137G/C and-607C/A are closely related to the development of coronary heart disease (CHD).Many studies have revealed that IL-18 not only involves in the development of Atherosclerosis (AS) in coronary, but also enhanced the instability of AS plaque, making it to be VP. IL-18 induces the coronary artery smooth muscle cell migrate to accelerate the progress of atherosclerosis and increase vascular stenosis through regulation CXCL16 and MMP9-dependent way; IL-18 can induce vascular endothelial cell production of tumor necrosis factor-α, interleukin-1, fas ligand, and adhesion molecules and other bioactive substances, it also regulate the monocyte macrophage to deposit in atherosclerotic plaque and induce cell death, both of which are the important mechanism for the development of VP and the key mediators of thrombosis and rupture of atherosclerotic plaque, and rupture of coronary atherosclerotic plaque, thrombus developing is the main pathophysiology of ACS processes occurring.From the above studies, we can see that IL-18 involves in the development of AS and VP in the level of nerve-body fluids and cells. Recently, there are new progresses in gene area. More and more studies confirmed that the promoter functional polymorphisms of IL-18 are closed to CHD, but there is no study to confirme the relationship between IL-18 promoter functional polymorphisms and VP. Our study explore the relationship between IL-18 promoter functional polymorphisms (-137G/C and-607C/A) and VP in the level of gene, to provide new theory basis for mechanism of VP, and do a good for the treament and diagnosis of VP.In summary, IL-18 plays an important role not only in the development of AS but the development of VP. However, the mechanism that IL-18 promotes the development of VP is still not clear now. Studies have shown that IL-18 can induce a variety of cells apoptosis, and apoptosis in plaque is an important feature of VP. More and more scholars are detecting apoptosis in plaque to diagnose VP. Increased apoptotic cells within the plaques can make necrotic core in AS plaque larger, fibrous cap thinner, inflammatory response more intensive. So that, IL-18 iducing cell apoptosis in AS plaque may be an important part in the development of VP, but it is lack of relevant research and needs further study to clarify its position in the development mechanism of VP. In this study, the AS plaques were stimulated by IL-18 in vitro, then we detect the rates of apoptosis to confirm that IL-18 lead to the development of VP by inducing apoptosis is one of mechanisms for developing VP. It not only can enrich the theory of developing VP, but also can provide new ideas fpr people to prevent and treat VP.Chapter 1:The Relationship between IL-18 and VP in CoronaryObjective:1. To detecte the IL-18 promoter functional polymorphisms (-137G/C and-607C/A) and plasma IL-18 of the patients with different types of CHD, explore the role IL-18 plays in the development of plaque in coronary2. To observe the IL-18 promoter functional polymorphisms (-137G/C and-607C/A) and plasma IL-18 of the CHD patients with different types of plaques in the coronary, explore the relationship between IL-18 and VP in coronary and explain the mechanisms development of VP in coronary.3. Investigate the change of plasma IL-18 in SAP patients who underwent ACS during the 2-years follow-up in 215 patients with SAP, explore the role IL-18 plays in the development of ACS.Subjects and MethodsObject1. SubjectsWe chose the patients who were prepared to be given CAG and (or) IVUS in Guangzhou General Hospital of Guangzhou Military Command from March 2007 to March 2011. Those who suffer from myocarditis, a serious heart failure, and serious liver and kidney diseases, autoimmune diseases, blood diseases, inflammation, infection, and other serious systemic diseases were excluded, there were 623 patients in all.2. MethodThe patients were divided into control group (173 cases) and CHD group (450 cases) according to the results of CAG, the CHD group was divided into SAP group (236 cases) and ACS group (214 cases) according to the results of CAG and their symptoms,194 CHD patients were divided into the VP group (116 cases) and the stable plaque group (78 cases) according to CAG and IVUS results.211 patients with SAP were divided they into 2 groups:developing ACS group (38 patients) and none ACS group (173 patients) according to the results of the 24 months’follow-up. Polymerase chain reactionsequencespecific primer (PCR-SSP) was used to detect IL-18 promoter functional polymorphisms (-137G/C-607C/A), and sequence they to verify their accuracy. ELASA was used to determine the plasma of IL-18 in all patients. Independent samples t-test was employed to analyze the distinction between 2 measured data,χ2-test was used to compare differences between 2 count data, One-way ANOVA analysis was used to analyze the distinction amoung 3 or more than 3 groups of measured data, multiple comparison LSD test was used to analyze the variance with homogeneity and the Tamban-e’s T2 test was employed to analyze variance with arrhythmia, A probability value<0.05 was considered statistically significant.Results:1. The concentration of plasma IL-18 in the CHD patients was higher than those in the controls (t=9.118, P=0.000), The concentration of plasma IL-18 in CHD patients with different clinical types was significantly different(F=102.500,P=0.000), that in AMI group was higher than that in UAP group (P<0.05), UAP group was higher than that in SAP group (P<0.05), SAP group was higher that in controls (P <0.05); The concentrations of plasma IL-18 in ACS group was higher than that in SAP group(t=12.353, P=0.000), VP group was higher that in SP group (t=3.818, P =0.000);2. The concentration of plasma IL-18 in the patients with different genotypes was significantly different (F=9.170,P=0.000). The concentration of plasma IL-18 in the patients with CC genotype at locus IL-18-607 was higher than that in CA (P=0.020) or AA-type patients (P=0.000), CA-type patients were higher than AA-type patients (P=0.037); The concentration of plasma IL-18 in the CHD patients with GG genotype at locus IL-18-137 was higher than that in CC-type patients(P=0.006), there was no significantly difference between GC-type patients and GG-type patients(P>0.05), GC-type patients andCC-type patients (P>0.05);3. The distribution of genotype at locus-607 and the allele frequency were significantly different between patients and controls, ACS group and SAP group, SP group and VP group(P all<0.05), haplotype (-607C) and allele C in CHD were significant higher than that in control group, ACS group were significant higher than those in SAP group, VP group were significant higher than those in SP group (P all <0.05). The distribution for the allele frequency of G in the CHD group was significantly higher than that in the controls(χ2 2=4.142, P= 0.042), The distribution for the allele frequency of A in the CHD group was significantly lower than that in the controls(χ2=4.142, P= 0.042), There was no significantly different distribution of all the other genotypes and alleles at locus-137 between CHD group and control group,ACS group and SAP group, VP group and stable plaque group (P all>0.05);4. The concentration of plasma IL-18 in the SAP patients who undergoing ACS was higher than that in the patients with no ACS (P<0.05), the concentration of plasma IL-18 in SAP patients underwent ACS was significantly higher than that before the ACS (P<0.05).Conclusions:1. The higher concentrations of plasma IL-18 was in the CHD patients and it paralleled with the gravity of disease. This suggested that IL-18 plays an important role in the development of CHD. It can be used as references in risk stratification and seriousness assessment of CHD.2. IL-18 promoter functional polymorphisms (-137G/C,-607C/A) may affect the plasma of IL-18 (P<0.05), the promoter functional polymorphism (-607C/A) was closely related to the occurrence of ACS and VP, It suggested IL-18 plays an important role in development of VP.Chapter 2: IL-18 promotes the development of VP by inducing apoptosis in AS plaque Objective:1. Use rabbit to establish AS model by high-cholesterol diet and obtain AS plaques from them. The AS plaque was stimulated in vitro by different concentrations and limes of IL-18, then observe the change of plaque morphology and cell apoptosis in the AS plaque, explore the prable mechanism for the development of VP;2. To investigate the relationgship between the apoptosis ratio and plaque morphology, to explore the role of cell apoptosis in plaque in the decelopment of VPMaterials and methods:1. Materials30 healthy white New Zealand male rabbits were fed adaptly for one week and then fed with high fat diet for 10 weeks,after 10 weeks,the rabbits were euthanized.The entire length of the aorta was exposed; the fat and tissue attaching to the arteries were cleared and the arteries were divided into 60 segments in all according to the distribution of plaque.2. Methods The AS plaques in vitro were stimulated by 3 kinds of concentrations and 4kinds of stimulus time,used formaldehyde to fixe the samples,then embedded withparaffin, sliced,stained HE. Used Image-Pro Plus image analysis software th analyze the image,and measured the the thickness of fibrous cap and nuclear cross section,TUNEL was used ththSt cell apoptosis in the AS plaque. Multi-factor factorial analysis was employed to analyze the distinction amoung 3 or more than 3 groups ofmeasured data,linear correlation analysis was use th the relationship between two measured variables.Results:1. The apoptotic index of plaques were changed according to the concentration and stimulus time of IL-18(F=50.790,P=0.000),withthe concentration and stimulus time of IL-18 increased,apoptotic index of plaques raised,there was an interaction between stimulus time and the stimulus concentration of IL-18( F-31.517,P =0,000);2. The fibrous cap thickness was changed according to the concentration and stimulus time of th-18(F=4.437,P=0.000),with the concentration and stimuhis time of IL-18 increased,the fibrous cap thickness of plaques reduced,there was no interaction between stimulus time and the stimulus concentration of IL-18(F =1.633,P=0.159);3. The core section thickness of plaques were changed according to the concentration and stimulus time of IL-18(F=2.209,P=0.046), with the concentration and stimulus time of IL-18 mcreased,the core section thickness of plaques increase,there was no interaction between stimulus lime and the stimulus concentration of IL-18(F=0.683,P=0.664);4. The cap / core ratio was changed according to the COncentration and stim加s time of IL-18(F=12.467,P =0.000),with the concentration and stimulus time of IL-18 increased, the cap / core ratio of plaques reduced, there was an interaction between stimulus time and the stimulus concentration of IL-18(F=4.134, P =0.002);3. Apoptotic index of cell in plaques was significantly negatively correlated with the cap/core ratio(F=0.776,P=0.05)Conclusions:1. IL-18 can induce cell apoptosis in the AS plaque in vitro;2. The apoptotic index of cell in plaques was significantly negatively correlated with the cap / core ratio,it suggests that cell apoptosis iin AS plaque is the main mechanisms of develoment of VP;3. IL-18 induces cell apoptosis in AS plaque may be the main mechanisms of promoting the development of VP. |
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