Toluene and P-Xylene Mixture Exerts Antagonistic Effect on Lipid Peroxidation in vitro

Blood serum levels of selected biomarkers of oxidative stress among printing workers occupationally exposed to low-levels of toluene and xylene

Printing workers (PWs) are exposed to a mixture of solvents, yet the health risks associated with such exposuer are unknown. This study aimed to compare the serum levels of selected biomarkers of oxidative stress among occupationally exposed PWs to low-level of toluene and xylenes and unexposed controls. Associations between levels of such biomarkers and occupational exposures to toluene and xylene were also investigated. Urinary levels of hippuric acid (HA) and methyl hippuric acids (MHAs) as exposure biomarkers of toluene and xylenes, respectively, and serum levels of oxidative stress biomarkers, including total antioxidant capacity (TAC), malondialdehyde (MDA), and the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), were measured among the 84 subjects, comprising 44 PWs and 40 unexposed subjects. Mean concentrations of urinary HA and MHAs of PWs showed a significant increase compared with the unexposed controls. Although levels of urinary biomarkers of exposure to toluene (HA) and xylenes (MHAs) were well below the biological exposure indices (BEIs; ACGHI), PWs presented significantly increased serum levels of MDA, and significantly decreased serum activities of SOD and GPx compared to the unexposed controls. However, for serum TAC and CAT activity, no significant difference was observed between the two groups. Correlation analyses indicated that urinary levels of HA and MHAs were positively correlated with MDA levels and negatively correlated with GPx and SOD. Our study suggested that the alterations evidenced in serum levels of MDA, SOD, and GPx could be involved in the oxidative stress caused by co-exposure to low levels of toluene and xylene. Further investigation is needed to clarify the effect of low-level occupational exposure to solvents among PWs.

Changes in oxidative stress biomarker and gene expression levels in workers exposed to volatile organic compounds

Exposure to volatile organic compounds (VOCs) was known to result in immunologic, respiratory, carcinogenic, reproductive, neurologic, and cardiovascular effects. However, the mechanisms by which VOCs induce these adverse health effects are not well understood. To evaluate the change of oxidative stress biomarker and gene expression levels in workers exposed to VOCs, we obtained urine and blood samples from 21 subjects before and after occupational exposure to VOCs. We measured levels of muconic acid (MuA), hippuric acid (HA), mandelic acid (MaA), and methyl hippuric acid (MHA) as urinary exposure biomarkers for benzene, toluene, ethylbenzene, and xylene (collectively BTEX), and malondialdehyde (MDA) and 8-hydroxydeoxyguanine (8-OHdG) as oxidative stress biomarkers in all subjects. We also evaluated BTEX-mediated RNA expression using cDNA microarray in 14 subjects. HA and MHA levels were higher following occupational exposure to VOCs (p < 0.01). In the linear regression analysis, HA ratios of after- and before-exposure were found to be significantly associated with increase of MDA ratios of after- and before-exposure after controlling for age, body mass index, and smoking (β = 0.06, p = 0.031). Evaluation of the gene expressions by HA showed that 23 gene expressions were found to be significantly associated with HA levels after adjusting for age, body mass index, and smoking (p < 0.001). In particular, expressions of ENO3 and CDNA FLJ39461 fis among the 23 genes were significantly associated with the change in MDA level (p < 0.05). Our study results suggest that exposure to VOCs, specifically toluene, induces oxidative stress and various gene expression change of which some may be responsible for oxidative stress.

Antioxidant Effect of CoQ(10) on N-nitrosodiethylamine-induced Oxidative Stress in Mice

The antioxidant effect of CoQ(10) on N-nitrosodiethylamine (NDEA)-induced oxidative stress was investigated in mice. Food intake and body weight were similar in both CoQ(10) and control groups during the 3-week experimental period. NDEA significantly increased the activities of typical marker enzymes of liver function (AST, ALT and ALP) both in control and CoQ(10) groups. However, the increase of plasma aminotransferase activity was significantly reduced in the CoQ(10) group. Lipid peroxidation in various tissues, such as heart, lung, liver, kidney, spleen and plasma, was significantly increased by NDEA, but this increase was significantly reduced by 100 mg/kg of CoQ(10). Superoxide dismutase activity increased significantly upon NDEA-induced oxidative stress in both the control and CoQ(10) groups with the effect being less in the CoQ(10) group. Catalase activity decreased significantly in both the control and CoQ(10) groups treated with NDEA, again with the effect being less in the CoQ(10) group. The lesser effect on superoxide dismutase and catalase in the NDEA-treated CoQ(10) group is indicative of the protective effect CoQ(10). Thus, CoQ(10) can offer useful protection against NDEA-induced oxidative stress.