Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
, 2017, 9736836

Spontaneous Production of Glutathione-Conjugated Forms of 1,2-Dichloropropane: Comparative Study on Metabolic Activation Processes of Dihaloalkanes Associated With Occupational Cholangiocarcinoma

Affiliations
Comparative Study

Spontaneous Production of Glutathione-Conjugated Forms of 1,2-Dichloropropane: Comparative Study on Metabolic Activation Processes of Dihaloalkanes Associated With Occupational Cholangiocarcinoma

Yu Toyoda et al. Oxid Med Cell Longev.

Abstract

Recently, epidemiological studies revealed a positive relationship between an outbreak of occupational cholangiocarcinoma and exposure to organic solvents containing 1,2-dichloropropane (1,2-DCP). In 1,2-DCP-administered animal models, we previously found biliary excretion of potentially oncogenic metabolites consisting of glutathione- (GSH-) conjugated forms of 1,2-DCP (GS-DCPs); however, the GS-DCP production pathway remains unknown. To enhance the understanding of 1,2-DCP-related risks to human health, we examined the reactivity of GSH with 1,2-DCP in vitro and compared it to that with dichloromethane (DCM), the other putative substance responsible for occupational cholangiocarcinoma. Our results showed that 1,2-DCP was spontaneously conjugated with GSH, whereas this spontaneous reaction was hardly detected between DCM and GSH. Further analysis revealed that glutathione S-transferase theta 1 (GSTT1) exhibited less effect on the 1,2-DCP reaction as compared with that observed for DCM. Although GSTT1-mediated bioactivation of dihaloalkanes could be a plausible explanation for the production of reactive metabolites related to carcinogenesis based on previous studies, this catalytic pathway might not mainly contribute to 1,2-DCP-related occupational cholangiocarcinoma. Considering the higher catalytic activity of GSTT1 on DCM as compared with that on 1,2-DCP, our findings suggested differences in the activation processes associated with 1,2-DCP and DCM metabolism.

Figures

Figure 1
Figure 1
Spontaneous reaction of 1,2-DCP with GSH under physiological pH conditions. (a) GSH levels in the reaction mixture containing halogenated hydrocarbons. Each in vitro mixture containing 6 mM GSH and DCM (shaded) or 1,2-DCP (black) at the indicated concentration (v/v) was incubated at 37 °C for 60 min, followed by determination of GSH concentration in the resulting solution. (b) Time- and dose-dependent decreases in GSH concentration in the presence of 1,2-DCP. The levels of remaining GSH under each experimental condition were normalized against the initial GSH concentration. Statistical analyses for significant differences were performed according to Bartlett's test, followed by Shirley-Williams' multiple-comparison test. ∗∗ P < 0.01 versus control in each group. (c) Putative metabolic pathway of 1,2-DCP and structures of relating metabolites in the presence of GSH. This metabolic scheme was modified from that of a previous report [12]. #P1 (GS-Cl-DCP) and #P2 represent the detected GSH-conjugated forms of 1,2-DCP, whereas #P3 was not detected in the present study. Dashed arrows mean that the processes were not observed in the present study. (d and e) Dose-dependent increases in GSH-conjugated forms of 1,2-DCP. Each mixture containing 6 mM GSH and 1,2-DCP at the indicated concentration (v/v) was incubated at 37 °C for 60 min, followed by examination of (d) GS-Cl-DCP (#P1) and (e) GS-DCP (#P2) levels in the resulting solution analyzed by LC-MS. Data were expressed as means ± SD, n = 4.
Figure 2
Figure 2
Effect of GSTT1 on the reactivity of halogenated hydrocarbon with GSH. (a) Data-processing scheme for differential analysis of four cases: in vitro reaction of 1,2-DCP or DCM with GSH in the presence or absence of GSTT1. The seven component products are summarized in Table 1. (b) Principal component analysis (PCA) based on differentially detected peaks across incubation component conditions. Green, 1,2-DCP without GSTT1; red, 1,2-DCP with GSTT1; purple, DCM without GSTT1; and yellow, DCM with GSTT1. This PCA of acquired data, such as peak information including integrated intensity, was performed by using the SIEVE 2.1 program. Upper panel, the first second-principal components; lower panel, the third two-principal components of all extracted data are plotted. n = 4 in each group.
Figure 3
Figure 3
Relative levels of halogenated hydrocarbon metabolites in the presence of GSTT1. (a) #P1, (b) #P2, (c) #M1, and (d) #M3. Reaction mixtures containing 1% (v/v) (a and b) 1,2-DCP or (c and d) DCM in the presence or absence of GSTT1 protein (50 μg/mL) were incubated at 37 °C for 60 min, followed by semiquantification of the levels of each metabolite in the resulting solution. Data were normalized against those acquired in the absence of GSTT1 conditions. Data were expressed as means ± SD, n = 12. Statistical analyses for significant differences were performed using Student's t-test. ∗∗P < 0.01. N.S.: not significantly different among groups.

Similar articles

See all similar articles

References

    1. Sies H. Glutathione and its role in cellular functions. Free Radical Biology & Medicine. 1999;27(9-10):916–921. doi: 10.1016/S0891-5849(99)00177-X. - DOI - PubMed
    1. Birben E., Sahiner U. M., Sackesen C., Erzurum S., Kalayci O. Oxidative stress and antioxidant defense. World Allergy Organization Journal. 2012;5(1):9–19. doi: 10.1097/WOX.0b013e3182439613. - DOI - PMC - PubMed
    1. Attia S. M. Deleterious effects of reactive metabolites. Oxidative Medicine and Cellular Longevity. 2010;3(4):238–253. doi: 10.4161/oxim.3.4.13246. - DOI - PMC - PubMed
    1. Toyoda Y., Tamai M., Kashikura K., et al. Acetaminophen-induced hepatotoxicity in a liver tissue model consisting of primary hepatocytes assembling around an endothelial cell network. Drug Metabolism and Disposition. 2012;40(1):169–177. doi: 10.1124/dmd.111.041137. - DOI - PubMed
    1. Monks T. J., Anders M. W., Dekant W., Stevens J. L., Lau S. S., van Bladeren P. J. Glutathione conjugate mediated toxicities. Toxicology and Applied Pharmacology. 1990;106(1):1–19. doi: 10.1016/0041-008X(90)90100-9. - DOI - PubMed

Publication types

MeSH terms

Feedback