mRNA expression levels among cell regulatory and DNA damage genes in benzene-exposed workers in China.

OBJECTIVE: We investigated how cells respond to the induction of DNA damage, focusing specifically on mRNA expression levels of cell regulatory and DNA repair genes under exposure to benzene. METHOD: The study sample was classified into three groups: direct exposure to benzene (A), indirect exposure to benzene (B), and non-exposed (C). Concentrations of benzene in the air of workplaces were monitored. Further blood biochemical parameters, cell cycle-regulated and DNA damage-related genes expression were analyzed. RESULTS: The mRNA expression levels of Apel, Rad51, Bcl-2, Bax, Xpa, and Xpc genes were significantly down-regulated in groups A and B, with a dramatic up-regulation of p21 gene in group A accompanied by significantly lower counts of white blood cells, hemoglobin, platelets and lymphocyte subsets of CD8+, CD4+, T and B cells. CONCLUSION: The results indicated that exposure to benzene had significantly altered mRNA expression of some critical cell regulatory and DNA repair genes.

[Association analysis of polymorphisms of metabolizing enzyme genes with chronic benzene poisoning based on logistic regression and multifactor dimensionality reduction].

OBJECTIVE: To explore the association of polymorphisms of metabolizing enzyme genes with chronic benzene poisoning (CBP) comprehensively by case-control design. METHODS: 152 CBP patients and 152 workers occupationally exposed to benzene without poisoning manifestations were investigated. 30 single nucleotide polymorphisms (SNPs) in 13 genes such as CYP2E1 were tested by PCR-RFLP, sequencing approaches. Logistic regression model was used to detect main effects and 2-order interaction effects of gene and/or environment. Multifactor dimensionality reduction (MDR) was used to detect high-order gene-gene or gene-environment interactions. RESULTS: Based on logistic regression, the main effects of GSTP1 rs947894, EPHX1 rs1051740, CYP1A1 rs4646903, CYP2D6 rs1065852 and rs1135840 were found to be significant (P < 0.05) while the confounding factors of sex, cigarette smoking, alcohol consumption and the intensity of benzene exposure were controlled. EPHX1 rs1051740 might be associated with CBP (P = 0.06). There existed 3 types of interactions were as followed: interactions of GSTP1 rs947894 with alcohol consumption, CYP2E1 rs3813867 with EPHX1 rs3738047, EPHX1 rs3738047 with alcohol consumption(P < 0.05), while the main effects of CYP2E1 rs3813867 and EPHX1 rs3738047 were not significant (P > 0.05). The other SNPs did not show any significant associations with CBP. According to MDR, a 3-order interaction with the strongest combined effect was found, i.e. the 3-factor combination of CYP1A1 rs4646903, CYP2D6 rs1065852 and CYP2D6 rs1135840. CONCLUSION: Gene-gene, gene-environment interactions are important mechanism to genetic susceptibility of CBP.

Polymorphisms in phase I and phase II metabolism genes and risk of chronic benzene poisoning in a Chinese occupational population.

It is widely accepted that the cytotoxicity and genotoxicity of benzene results from the action of reactive metabolites. Therefore, genetic variation in metabolic enzyme genes may contribute to susceptibility to chronic benzene poisoning (CBP) in the exposed population. Using a case-control study that included 268 benzene-poisoned patients and 268 workers occupationally exposed to benzene in South China, we aimed to investigate the association between single-nucleotide polymorphisms in genes with phase I and II of metabolism and risk of CBP. The TaqMan technique was used to detect polymorphisms of CYP1A1, CYP1A2, CYP1B1, ADH1B, EPHX1, EPHX2, NQO1, MPO, GSTP1 and UGT1A6 genes. We also explored potential interactions of these polymorphisms with lifestyle factors such as cigarette smoking and alcohol consumption. A weak positive association was found between glutathione S-transferase pi-1 (GSTP1) rs1695 polymorphism and the risk of CBP (P = 0.046), but this association was not statistically significant (P = 0.117) after adjustment for potential confounders. Further analysis showed that the risk of CBP increased in the subjects with EPHX1 GGAC/GAGT diplotype (P = 0.00057) or AGAC/GAGT diplotype (P = 0.00086). In addition, we found that alcohol drinkers with the EPHX1 rs3738047 GA + AA genotypes and non-alcohol drinkers with the GSTP1 rs1695 AA genotype tended to be more susceptible to benzene toxicity. Our results suggest that genetic polymorphisms in EPHX1 may contribute to risk of CBP in a Chinese occupational population.

Genetic polymorphisms in CYP1A1, CYP2D6, UGT1A6, UGT1A7, and SULT1A1 genes and correlation with benzene exposure in a Chinese occupational population.

Metabolic enzymes involved in benzene activation or detoxification, including cytochrome P-450 1A1 (CYP1A1), cytochrome P-450 2D6 (CYP2D6), UDP-glucuronosyltransferase 1A6 (UGT1A6), UDP-glucuronosyltransferase1A7 (UGT1A7), and sulfotransferase 1A1 (SULT1A1), were studied for their roles in human susceptibility to benzene poisoning. All 304 subjects were investigated with a unitary questionnaire and their DNA was isolated from blood samples by a routine phenol-chloroform extraction. The study included 152 benzene poisoning patients, and 152 control workers occupationally exposed to benzene in South China. The genotypes were determined by polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP) technique with genomic DNA. No individuals had the CYP 2D6 c.212 G>A variant alleles in this study. There is no association between the UGT1A6 c.181 T>A, UGT1A7 c.208 Trp>Arg, and SULT1A1 c.638 G>A genotypes and increased risk of benzene-induced carcinogenesis. Although most of the CYP2D6 haplotypes did not show any significant difference, the CYP2D6 haplotype CYP2D6 c.188 C/C, C/T, and c.4268 C/C was significantly overrepresented in the case group (OR 4.02, 95% CI: 2.53-6.39) compared with in controls. Overall, our data suggested that individuals with CYP1A1 c.5639 T/T, CYP2D6 c.188 C/C, C/T, and CYP2D6 c.4268 C/C genotypes tend to be more susceptible to benzene toxicity.

[Relationship of genetic polymorphism in APE1 and ADPRT to risks of chronic benzene poisoning].

OBJECTIVE: To explore the relationship between genetic polymorphisms in apurinic/apyrimidinic endonuclease (APE1) and ADP ribosyltransferase (ADPRT) and individuals' susceptibility to chronic benzene poison ing (BP). METHODS: A case-control study was conducted. One hundred and fifty-two B P patients and 152 workers occupationally exposed to benzene without poisoning manifestations were investigated. The mismatched bases combined to create restriction site with restrained fragment length polymorphism technique (CRS-RFLP) was used for detecting the single nucleotide polymorphisms (SNPs) at Asp148Glu of APE1 gene and Val762Ala of ADPRT gene. RESULTS: There was no significant difference in the distribution of genotypes of APE1Asp148Glu and ADPRTVal762Ala between the patients and the control groups. Compared with individuals having genotype of APE1Asp148Glu T/T without habit of alcohol consumption, there was a 4.13 times increased risk of BP for the alcohol user with genotype of APE1Asp148Glu T/T (OR = 4.13, 95% CI: 1.07 - 15.85, P = 0.03). The analysis of Logistic regression showed that smoking may play some role in modifying the risk of cironic benzene poisoning (OR = 0.33, 95% CI: 0.14 - 0.75, P = 0.01). CONCLUSION: The genetic polymorphisms in APE1Asp148Glu, ADPRTVal762Ala are not related to the risk of BP. Potential interaction is found between alcohol consumption and polymorphism of APE1Asp148Glu. Further study is needed to elucidate this interaction.

[Genetic polymorphism of CYP-1A1, CYP2D6 and risks of chronic benzene poisoning].

OBJECTIVE: To explore the relationship between genetic polymorphisms of CYP-1A1 and CYP2D6 and risks of chronic benzene poisoning (BP). METHODS: A case control study was conducted. 152 BP patients and 152 workers occupationally exposed to benzene without poisoning manifestations were involved. Polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) technology was used for detecting the single nucleotide polymorphisms (SNPs) of MspI in the non-coding region of CYP-1A1 gene and c.188, g.212 position in the first extron of CYP2D6 gene. RESULTS: The individuals with CYP1A1 MspI T/T genotype had a 1.32 times (95% CI: 1.05 approximately 1.65, P = 0.02) increased risk of BP compared with those carrying T/C and C/C genotypes. In no-smoking population, there was a 1.56 times (95% CI: 1.15 approximately 2.12, P = 0.003) increased risk of BP for subjects carrying CYP1A1 MspIT/T genotype compared with those carrying T/C and C/C genotypes. The individuals carrying CYP2D6 c.188 C/C or C/T genotype had a 1.23 times (95% CI: 1.05 approximately 1.42, P = 0.01) increased risk compared with those carrying T/T genotypes. In no-smoking population, there was a 1.23 times (95% CI: 1.04 approximately 1.47, P = 0.01) increased risk of BP for subjects carrying CYP2D6 c.188 C/C or C/T genotypes compared with those carrying T/T genotype. The single nucleotide polymorphism of g.212 position in the first extron of CYP2D6 gene had not been validated. CONCLUSION: The individuals with CYP2D6 c.188 C/C, CYP2D6 c.188 C/T and CYP1A1 MspIT/T genotypes tend to be more susceptible to benzene toxicity.

[Relationship between genetic polymorphism in hMTH1c.83, hOGG1c.326 and hMYHc.335 and risks of chronic benzene poisoning].

OBJECTIVE: To explore the relationship between genetic polymorphisms in hMTH1, hOGG1 and hMYH and risks of chronic benzene poisoning (CBP). METHODS: A case control study was conducted. One hundred and fifty-two BP patients and 152 workers occupationally exposed to benzene without poisoning manifestations were investigated. The polymerase chain reaction restrained fragment length polymorphism technique (PCR-RFLP) was applied to detect the single nucleotide polymorphisms (SNPs) on c.83 of hMTH1 gene, c.326 of hOGG1 gene and c.335 of hMYH gene. RESULTS: There were 2.51 times (OR(adj) = 2.51, 95% CI: 1.14-5.49, P = 0.02) and 2.49 times (OR(adj) = 2.49, 95% CI: 1.52-4.07, P < 0.01) risks of BP for individuals carrying genotypes of hMTH1c.83Val/Met + Met/Met or hOGG1c.326Cys/Cys compared with individuals carrying genotypes of hMTH1c.83Val/Val or hOGG1c.326Ser/Cys + Ser/Ser, respectively. Compared with individuals carrying genotypes of hOGG1c.326Cys/Cy and hMYHc.335 is/His at the same time, there was 0.33 times (OR(adj) = 0.33, 95% CI = 0.15-0.72, P = 0.01) risks of BP for these with genotypes of hOGG1c.326Ser/Cys + Ser/Ser and hMYHc.335His/Gln + Gln/Gln simultaneously. In the smoking group, there was 0.15 times (OR(adj) = 0.15, 95% CI: 0.03-0.68, P = 0.01) risks of BP for subjects carrying genotypes of hMYHc.335His/Gln + Gln/Gln compared with these carrying genotypes of hMYHc.335His/His. CONCLUSION: Polymorphisms of hMTH1 Val83 Met and hOGG1 Ser326Cys may contribute to altered risks of CBP, and potential interaction may exist among polymorphisms of hOGG1 Ser326Cys and hMYH His335Gln.

Evaluation in vinyl chloride monomer-exposed workers and the relationship between liver lesions and gene polymorphisms of metabolic enzymes.

AIM: To analyze occupational health hazards exposure to doses lower than the Chinese occupational health standard in a selected VC polymerization plant in China, and also to elucidate the relationship between genetic polymorphisms and genetic susceptibility on liver lesions of workers exposed to vinyl chloride monomer(VCM). METHODS: In order to explore the mechanism of VCM-related health effects, we used a case-control design to investigate the association between the genetic polymorphisms of metabolic enzymes and liver lesions in workers occupationally exposed to VCM. Genotypes of CYP2E1, GSTT1, GSTM1, ALDH2 and ADH2 were identified using PCR and PCR-RFLP. RESULTS: Even when the concentration of VCM was lower than the current Chinese occupational health standard, neurasthenia, pharyngeal irritation, liver ultrasonography abnormalities and hemoglobin disorders were significantly higher in exposure subjects compared to non-exposure subjects, and the relative risks (RR and 95% CI) were 1.74 (1.06-2.85), 1.97 (1.56-2.48), 10.69 (4.38-26.12), and 2.07 (1.20-3.57). CYP2E1 c1c2/c2c2 genotype was significantly associated with liver damages (OR 3.29, 95% CI 1.51-7.20, P<0.01). CONCLUSION: The incidences of neurasthenia and liver ultrasonography abnormalities significantly increase when the cumulative exposure dose increases. The genotypes of metabolic enzymes (CYP2E1 c1c2/c2c2, null GSTT1 and ADH2 1-1) play important roles in VCM metabolism. Polymorphisms of CYP 2E1, GSTT1 and ADH2 may be a major reason of genetic susceptibility in VCM-induced hepatic damage.

[Case-only study on the relationship between genetic polymorphisms in toxicant metabolizing enzymes and risk of occupational chronic benzene poisoning].

OBJECTIVE: To explore the effects of interaction between environmental exposure factors and genetic polymorphism in toxicant metabolizing enzymes on risk of occupational chronic benzene poisoning. METHODS: One hundred and fifty-two cases of chronic benzene poisoning were analyzed for the risk by case-only study. RESULTS: The frequency of non-null GSTT1 gene in benzene poisoning workers with moderate benzene exposure level was higher than that in cases with lower benzene exposure (68.63% vs 38.00%, OR(adj) = 4.32, 95% CI 1.75 - 10.66, P = 0.002). The frequency of NQO1 C.609T/T gene in alcohol drinking group was higher than that in non-drinking group (61.11% vs 20.00%, OR(adj) = 8.03, 95% CI 2.28 - 28.25, P = 0.001), moreover, it was higher in workers with smoking and drinking than that in the rest group, and in drinking x exposure level workers than that in non-drinking x exposure level workers (85.71% vs 22.76%, OR(adj) = 18.62, 95% CI 2.01 - 172.72, P = 0.01 and 61.11% vs 20.00%, OR(adj) = 3.18, 95% CI 1.55 - 6.52, P = 0.002 respectively). The frequency of non-null GSTM1 gene was also higher in drinking x exposure level workers than that in non-drinking x exposure level workers (66.67% vs 47.06%, OR(adj) = 1.99, 95% CI 1.05 - 3.76, P = 0.036). CONCLUSION: There is interaction between the polymorphism of GSTT1 gene and moderate benzene exposure level; non-null GSTM1 gene and drinking x exposure level increase the risk of occupational chronic benzene poisoning; polymorphism of NQO1 gene C.609 also interacts with drinking, while polymorphism of NQO1 gene and drinking x smoking may further increase the risk of occupational chronic benzene poisoning.

[Relationship of genetic polymorphism of microsomal epoxide hydrolase with susceptibility of chronic benzene poisoning].

OBJECTIVE: To explore the relationship between genetic polymorphisms of microsomal epoxide hydrolase (mEH) and susceptibility of chronic benzene poisoning (BP). METHOD: A case-control study was conducted. 152 BP patients and 152 workers occupationally exposed to benzene without poisoning manifestations were investigated. Polymerase chain reaction-restrained fragment length polymorphism technique (PCR-RFLP) was applied to detect the single nucleotide polymorphisms (SNPs) on c.113 and c.139 of mEH gene. RESULTS: The risk of BP for individuals carrying mEHc.113 C/C genotype was 0.60 (OR = 0.60, 95% CI: 0.37 - 0.97, P = 0.04) of those carrying T/T and T/C genotypes. In non-smoking population, the risk of BP for subjects carrying mEHc.113 C/C genotype was 0.56 (OR = 0.56, 95% CI: 0.33 - 0.96, P = 0.03) of those carrying T/T and T/C genotypes, and in non-drinking population, the individuals carrying mEHc.113 C/C genotype was 0.51 (OR = 0.51, 95% CI: 0.30 - 0.86, P = 0.01) of those carrying T/T and T/C genotypes. CONCLUSION: The subjects carrying mEHc.113 C/C genotype and together with non-smoking or non-drinking habit may have lower risk of chronic benaene poisoning.