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Pyrrole adducts in globin and plasma of workers exposed to hexane

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International Archives of Occupational and Environmental Health Aims and scope Submit manuscript

Abstract

Objectives

Urinary excretion of 2,5-hexanedione is currently used to estimate the exposure levels of hexane occurring to an individual during the previous work shift. However, because hexane exposures and urinary 2,5-hexanedione levels can vary considerably from day to day, and subchronic to chronic exposures to hexane are required to produce neuropathy, this biomarker may not accurately reflect the risk of an individual for developing hexane neuropathy. This investigation examines the potential of hexane-derived pyrrole adducts produced on globin and plasma proteins as markers for integrating cumulative exposures. Because the pyrrole markers incorporate bioactivation of hexane to 2,5-hexandione and the initial step of protein adduction involved in hexane-induced neuropathy, they potentially can serve as biomarkers of effect through reflecting pathogenetic events within the nervous system. Additionally, pyrrole formation is an irreversible reaction suggesting that hexane-derived protein pyrroles can be used to assess cumulative exposures to provide a better characterization of individual susceptibilities.

Methods

To examine the utility of the proposed markers, blood samples were obtained from eleven workers who used hexane for granulating metal powders in a slurry to produce metal machining die tools and four non-exposed volunteers. Globin and plasma were isolated, and the proteins were digested using pepsin, reacted with Ehrlich’s reagent and the level of pyrrole adducts were determined by absorbance at 530 nm. To determine the dose–response curve and dynamic range of the assay, erythrocytes were incubated with a range of 2,5-hexanedione concentrations and the net absorbance at 530 nm of isolated globin was measured.

Results

Pyrrole was detected in both the globin and plasma samples of the workers exposed to hexane and the levels of pyrroles in plasma were positively correlated with the levels of pyrroles in globin for most of the workers.

Conclusions

This investigation demonstrates that detectable levels of hexane-derived protein pyrrole adducts are produced on peripheral proteins following occupational exposures to hexane and supports the utility of measuring pyrroles for integrating cumulative exposures to hexane.

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Acknowledgements

Our sincere thanks to Dr. Doyle G. Graham (Vanderbilt University Medical Center, TN, USA), Dr. Yasutaka Ogawa, Dr. Naomi Hisanaga (National Institute of Industrial Health, Kanagawa, Japan) and Dr. Yasuhiro Takeuchi (Emeritus Professor of Nagoya University, Nagoya, Japan).

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Authors and Affiliations

  1. Department of Occupational and Environmental Health, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan

    Gaku Ichihara

  2. Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA

    Venkataraman Amarnath, Holly L. Valentine & William M. Valentine

  3. Department of Public Health, Wakayama Medical University, Wakayama, Japan

    Tatsuya Takeshita

  4. Department of Social and Environmental Medicine, Osaka University Graduate School of Medicine, Osaka, Japan

    Kanehisa Morimoto & Tomotaka Sobue

  5. Osaka Occupational Health Service Center, Osaka, Japan

    Toshio Kawai

Authors
  1. Gaku Ichihara
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  2. Venkataraman Amarnath
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  3. Holly L. Valentine
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  4. Tatsuya Takeshita
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  5. Kanehisa Morimoto
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  6. Tomotaka Sobue
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  7. Toshio Kawai
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  8. William M. Valentine
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Contributions

GI and WMV deigned the project and wrote the manuscript. GI, VA and HLV measured pyrrole adducts and protein. TT, KM and TS conducted the field-work. TK measured urinary 2,5-hexanedione. VA drew the figure of pyrrole formation and detection.

Corresponding author

Correspondence to Gaku Ichihara.

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The authors declare that they have no competing interests.

Informed consent

All assays were performed with the subjects’ informed consent following the Helsinki Declaration. The study protocol was approved by the ethical committee of Tokyo University of Science.

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Ichihara, G., Amarnath, V., Valentine, H.L. et al. Pyrrole adducts in globin and plasma of workers exposed to hexane. Int Arch Occup Environ Health 92, 873–881 (2019). https://doi.org/10.1007/s00420-019-01430-7

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  • DOI: https://doi.org/10.1007/s00420-019-01430-7

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