The Relationship Between Polymorphisms Of Interleukin-4 Gene And Pneumoconiosis Susceptibility

Background Pneumoconiosis is the most common and serious occupational disease in China. According to the end of 2008 year's data, the number of occupational patients had more than 700 thousands in the all past of years, there approximate had 640 thousands pneumoconiosis patients. The number of pneumoconiosis patients in our country was three more than the total number of all of other country's. This figure just was the part of true number because it only belonged the emphasis enterprises in our country. According to the end of 2009 year's data, 14495 new pneumoconiosis patients had been diagnosed, it approximat eighty percent in workers with occupational dis- ease. Controlling the morbidity of pneumoconiosis should take a heavy burden and embark on a long road and brook no delay. According to a great deal epidemiological studies of pneumoconiosis, only a few persons suffered from it even they had the same situation of exposure. They had the different severity in the group of patients. This fact indicated that the morbidity of pneumoconiosis not only related to environmental factor but also with individual susceptivity. Exploring genetic susceptible markeres of screening the high risk group of workers exposed to dust is an important to decrease development of pneumoconiosis. Pneumoconiosis is a fibrotic disease becase of inhaling dust in occupational activity. There are many cytokines of participating the lung fibrosis process, such as transforming growth factor (TGF), tumor necrosis factor-α(TNF-α), platelet-derived growth factor (PDGF), fibronectin (FN), Interleukin-1 (IL-1), Interleukin-6 (IL-6), etc. Interleukin-4 (IL-4) is a multifunctional cytokine. The production of IL-4 protein is regulated by gene. The protein expression is different in different genotype individuals at the same physiological and pathologic conditions. As an important factor in the process of inducing fibrosis, IL-4 level increase in systemic sclerosis because it can promote the proliferation and differentiation of fibroblast. Integrality of skin will be destroyed when the chaos happen in the signal transmission of IL-4. IL-4 level obviously increase in the rat model of pulmonary fibrosis. All of these facts indicate that there is the intimate connection between IL-4 and fibrosis. So we have enough reasons about the definite relationship between IL-4 and pneumoconiosis. IL-4 have many mutant sites, but we haven't found the studies about the relationship between polymorphisms of Interleukin-4 gene and pneumoconiosis.Objectives Case-control study was adopted in our study. We explored the relationship between polymorphisms of IL-4 gene (-33, +45, intron3, +429, +448) and the susceptibility of silicosis and coal worker's pneumoconiosis (CWP). We try to interpret the effect of gene in pneumoconiosis suscep- tibility and to provid evidence of genetic susceptible markeres for screening the high risk group of workers exposed to dust.Subjects and methods 298 gold mine workers, 967 refractories factory workers and 2568 coal mine workers were investigated whom all exposed to dust. They were examined by chest X-ray base on the health check-up. All investigators were trained together and questionnaire was designed by ourselves. All subjects's data was collected by face to face. The contents included the general information and occupational exposure histories. The pneumoconiosis was diagnosed by the Pneumoconiosis Diagnosis Expert Panel, based on the Chinese National Diagnosis Criteria of Pneumoconiosis (GBZ70-2009). From them, 101 silicosis patients were selected as silicosis cases, 112 coal worker's pneumoconiosis patients were selected as CWP cases, all them were male and Han nationality. The workers exposed to dust and without pneumoconiosis were selected as the controls according to the same nation, the same working type and nearly age. The persons of having other fibrosis disease were excluded in all objects. The number of contorls of silicosis and CWP was 121 and 130 persons respectively. The genotype of IL-4 (-33, +45, intron3, +429, +448) were detected by using the method of polymerase chain reaction–restriction fragment length polymorphism (PCR- RFLP) techniques. Pearson′sχ~2 test was used for analysing relation of the genotypes with pneumoconiosis. Values of P<0.05 were considered statis- tically significant.Results1 General informations The number of pneumoconiosis cases was 213, they all are male, Han nationality, their average age was 54.9±9.4 years, average cumulative length of service was 29.3±6.1 years. The cases of 101 silicosis patients included four working types, such as crushing, briquetting, roasting and digger. Their average age was 59.1±8.9 years, average cumulative length of service was 28.0±5.1 years. The sex, nationality and work environment of 121 silicosis controls was same as cases. Their average age was 57.3±8.1 years, average cumulative length of service was 28.1±5.2 years. The difference of age, cumulative length of service, smoking rate or smoking indices between cases and controls were not significance (P>0.05). These two groups had good comparability. All 112 coal worker's pneumo- coniosis patients was male, Han nationality. Their average age was 51.1±8.1 years, average cumulative length of service was 29.8±6.7years. The sex, nationality and work environment of 130 CWP controls was same as CWP. Their average age was 52.4±1.9 years, average cumulative length of service was 30.6±4.7 years. The difference of age, cumulative length of service, smoking rate between cases and controls were not significance (P>0.05). 2 The distribution of genotype and allele of IL-4-33 site The frequencies of CC, CT and TT of -33 locus in the cases were 12.7%, 30.5% and 56.8% and in the controls were 6.4%,23.1% and 70.5%, respectively. The difference was significant (χ~2=10.695, P<0.01). The frequencies of allele C were 27.9% and 17.9% in cases and controls. The difference was significant (χ~2=13.222, P<0.01). The frequencies of three genotypes in the silicosis were 11.9%, 32.7% and 55.4% and in the controls were 4.1%, 26.4% and 69.4%, respectively. The difference was significant (χ~2=6.751, P<0.05). The freq- uencies of allele C were 28.2% and 17.4% in silicosis and controls. The difference was significant (χ~2=7.498, P<0.01). The three genotypes in the CWP were 13.4%, 28.6% and 58.0% and in the controls were 8.5%, 20.0% and 71.5%, respectively. The difference was not significant (χ~2=4.886, P>0.05). The frequencies of allele C were 27.7% and 18.5% in the CWP and controls. The difference was significant (χ~2=5.821, P<0.05).3 The distribution of genotype and allele of IL-4 VNTR site The freq- uencies of B1B1, B1B2 and B2B2 of VNTR locus in the cases were 70.9%, 26.3% and 2.8% and in the controls were 70.1%, 27.5% and 2.4%, respectively. The difference was not significant (χ~2=0.152, P>0.05). The frequencies of allele B1 were 84.0% and 83.9% in the cases and controls. The difference was not significant (χ~2=0.005, P>0.05). The frequencies of three genotypes in the silicosis cases were 73.3%, 25.7% and 1.0% and in the controls were 68.6%, 29.8% and 1.7%, respectively. The difference was not significant (χ~2=0.672, P>0.05). The frequencies of allele B1 were 86.1% and 83.5% in the cases and controls in silicosis. The difference was not significant (χ~2=0.604, P>0.05). The three genotypes in the CWP cases were 68.8%, 26.8% and 4.5% and in the controls were 71.5%, 25.4% and 3.1%, respectively. The difference was not significant (χ~2=0.423, P>0.05). The frequencies of allele B1 were 82.1% and 84.2% in the cases and controls in CWP. The difference as not significant (χ~2=0.376, P>0.05).4 The distribution of genotype and allele of IL-4 +45 site The frequencies of AA, AG and GG of +45 locus in the pneumoconiosis cases were 51.6%, 32.9% and 15.5% and in the controls were 57.4%, 28.7% and 13.9%, respectively. The difference was not significant (χ~2=1.536, P>0.05). The frequencies of allele A were 68.1% and 71.7% in the cases and controls. The difference was not significant (χ~2=1.454, P>0.05). The frequencies of three genotypes in the silicosis cases were 55.4%, 33.7% and 10.9% and in the controls were 62.0%, 26.4% and 11.6%, respectively. The difference was not significant (χ~2=1.386, P>0.05). The frequencies of allele A were 72.3% and 75.2% in the cases and controls in silicosis. The difference was not significant (χ~2=0.490, P>0.05). The three genotypes in the CWP cases were 48.2%, 32.1% and 19.6% and in the controls were 53.1%, 30.8% and 16.2%, respectively. The difference was not significant (χ~2=0.782, P>0.05). The frequencies of allele A were 64.3% and 68.5% in the cases and controls in CWP. The difference was not significant (χ~2=0.942, P>0.05).5 The distribution of genotypes of IL-4 (+429, +448) sites There were just only GA genotype for IL-4 +429 in these two studies groups and only CC genotype in the site of IL-4 +448. These two sites showed the unity genotype in the exposed population, this suggested that mutations in these two sites might be correlated, it could be a great relationship with the race.Conclusions The relationship between genetic polymorphism of IL-4-33 site and pneumoconiosis had been found. Especially in the silica workers, the wild type genotype of -33 site was a risk factor for silicosis. No relationships between IL-4 VNTR or +45 genotypes and silicosis or CWP had been found in this study. The polymorphism of IL-4 (+429, +448) sites had not been found in the group of workers exposed to dust.