Association Study Between EIF4E, MMP-9 And Psoriasis

Psoriasis （PS） is a common chronic inflammatory skin problem, characterized by erythematous plaques bearing adherent silvery scales. Different prevalent rates are shown between different races and different regions. The immunopathogenesis of psoriasis is complex, with both genetic and environmental factors contributing to the development of the disease. T lymphocyte cells are central to its pathogenesis. Infection, getting wet, trauma, mental stress are risk factors of psoriasis and may have impacts on its pathogenesis. Psoriasis is recognized as a multiple gene controlled disease, and numerous candidate genes have been reported （PSORS1-PSORS9）. The strongest genetic association for psoriasis are PSORS1 on 6p21 and PSORS2 on 17q25. Since the establishment of GWAS （genome-wide association studies）, there have been many new discoveries on genes associated with psoriasis.Psoriasis is characterized by a marked hyperproliferation of the keratinocytes. As the most effective regulatory factors, eIF4E （eukaryotic translation initiation factor 4E） plays a crucial role in controlling the initiation rate of mRNA translation in eukaryote protein synthesis, and is involved in cell transformation, apoptosis resistance, wound healing process and longevity. The activity of eIF4E is limited under normal physiological conditions in order to maintain normal level of cellular mRNA translation required for normal life activities. During tumorigenesis, eIF4E expression increases and thus the enhanced expression of downstream oncogenes. Studies have shown that levels of phosphorylated eIF4E and eIF4E-binding protein （eIF4E binding proteins,4E-BP） in psoriatic lesions are higher than those in non-lesion areas, indicating that eIF4E in psoriasis lesions may get abnormally expressed, contributing to the pathological processes involved in the disease. Matrix metalloproteinases （MMPs） are matrix proteinases. They are involved in the breakdown of extracellular matrix in normal physiological processes, such as embryonic development, reproduction, and tissue remodelling, as well as in disease processes, such as arthritis and metastasis. MMPs are also thought to play a major role on cell behaviors such as cell proliferation, migration （adhesion/dispersion）, differentiation, angiogenesis, apoptosis, and host defense. MMP-9 is one member of MMPs, and many reports had indicated the relationship between MMP-9 and psoriasis. Therefore both eIF4E and MMP-9 are thought to play important roles in development of psoriasis.This study examined the expression of eIF4E and MMP-9 in the lesions of psoriasis vulgaris by using immunohistochemical technique and RT-PCR. A population-based case-control association study was also conducted to investigate the association of eIF4E and MMP-9 genes with psoriasis. The aim of this study is to investigate the role of eIF4E and MMP-9 in psoriasis, and to search susceptibility loci of PS. PART ONE Expression of eIF4E and MMP-9 in the lesions of psoriasis vulgaris Objective:To study the expression of eukaryotic initiation factor 4E （eIF4E） and matrix metalloproteinase-9 （MMP-9） in psoriastic lesions and to explore their clinical significance.Methods:1.40 cases of psoriasis patients （21 males,19 females） and 30 control samples were selected under informed consent. The skin biopsy lesions were removed and divided into two parts, one to make wax block, the other to be frozen in liquid nitrogen. The expression of eIF-4E and MMP-9 were detected by PV-9000 immunohistochemical method. Wilcoxon rank sum test was used to compare the expression of eIF4E and MMP-9 in psoriasis lesions and normal tissue, and P values of<0.05 was taken to be statistically significant. Spearman correlation test was used to analyze the correlation of expression between eIF4E and MMP-9, and P value<0.05 was taken to be statistically significant.2. The expression of eIF-4E and MMP-9 were determined by RT-PCR in frozen samples of 40 cases of psoriasis vulgaris as well as 30 cases of healthy individuals. Using image analysis technique, we analyzed the quantity of eIF-4E and MMP-9 expressed in psoriasis vulgaris and the normal skin. And their correlation analysis was performed.Results:1. Immunohistochemical study showed that eIF4E was not expressed in the normal samples, while the weak positive and positive expression were observed in PS. MMP-9 was expressed in both samples, but positive and strong positive in PS. The levels of eIF-4E and MMP-9 were significantly higher in PS than those in the normal skin tissue （P< 0.0001）.2. Spearman rank correlation analysis showed no correlation between the expression level of eIF-4E and MMP-9 in psoriasis （r=0.05, P>0.05）.3. RT-PCR results showed the expression of eIF4E in psoriasitic lesion was significantly higher （P<0.005） than that in normal skin, with quantification values of 1.39±0.13 and O, respectively. The expression of MMP-9 in psoriatic lesions was also significantly higher （P<0.005） than that in normal skin, the mean absorbance values for PCR bands were 6.71±0.68 （psoriatic lesion） and 2.00±0.11 （normal skin）,.Conclusion: Both eIF-4E and MMP-9 were over-expressed in lesions of PS, Expression of eIF-4E and MMP-9 at both mRNA and protein levels were significantly higher than that of normal skin tissue, which may contribute to the pathogenesis of psoriasis.PART TWO Association of polymorphisms in eIF4E and MMP-9 genes with psoriasis in Chinese Han populationObjective:To investigate the association of the eIF4E and MMP-9 gene polymorphisms with psoriasis in Chinese Han population.Methods:A population-based case-control association study was carried out in 188 psoriasis patients （110 males,78 females） and 280 healthy controls from Shandong province, from whom both clinical data and blood samples were collected. Taqman SNP genotyping method was used to genotype three SNPs:rs4810482 and rs3918254 in MMP-9 and rs11723037 in eIF4E gene. Pair wise linkage disequilibrium analysis was conducted by Haploview4.2. Allele and genotype frequencies were analyzed using Plinkl.07. Bioinformatics tools were employed to analyze the sequence of rs4810482 locus （NT₀11362.10:g.14830642T> C）, and Matlnspector software was used to predict transcription factor binding sites.Results1. All the SNPs genotype distributions in our sample sets agreed to Hardy-weinberg equilibrium in either PS cases or controls.2. The allelic and genotypic distribution of rs4810482 was significantly different in PS and control groups. The minor allele T was significantly associated with psoriasis with OR=1.49 and allelic p=0.006. The difference remained significant under recessive and dominant models.3. There was only weak linkage disequilibrium （r2=0.06） between the two MMP-9 SNP sites, rs4810482 and rs3918254.4. The allelic and genotypic distribution of rs11723037 （eIF4E） and rs3918254 （MMP-9） was not significantly different in PS and control groups.Conclusions:1. The genetic variations of the MMP-9 gene may be associated with psoriasis in Chinese Han population, and MMP-9 maybe one of the susceptibility genes of PS.2. eIF4E may not be the susceptibility genes of PS.