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Environ Health Perspect. 1996 Dec;104 Suppl 6:1251-6.

p-Benzoquinone, a reactive metabolite of benzene, prevents the processing of pre-interleukins-1 alpha and -1 beta to active cytokines by inhibition of the processing enzymes, calpain, and interleukin-1 beta converting enzyme.

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  • 1Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.


Chronic exposure of humans of benzene affects hematopoietic stem and progenitor cells and leads to aplastic anemia. The stromal macrophage, a target of benzene toxicity, secretes interleukin-1 (IL-1), which induces the stromal fibroblast to synthesize hematopoietic colony-stimulating factors. In a mouse model, benzene causes an acute marrow hypocellularity that can be prevented by the concomitant administration of IL-1 alpha. The ability of benzene to interfere with the production and secretion of IL-1 alpha was tested. Stromal macrophages from benzene-treated mice were capable of the transcription to the IL-1 alpha gene and the translation of the message but showed an inability to process the 34-kDa pre-IL-1 alpha precursor to the 17-kDa biologically active cytokine. Treatment of normal murine stromal macrophages in culture with hydroquinone (HQ) also showed an inhibition in processing of pre-IL-1 alpha. Hydroquinone is oxidized by a peroxidase-mediated reaction in the stromal macrophage to p-benzoquinone, which interacts with the sulfhydryl (SH) groups of proteins and was shown to completely inhibit the activity of calpain, the SH-dependent protease that cleaves pre-IL-1 alpha. In a similar manner, HQ, via peroxidase oxidation to p-benzoquinone, was capable of preventing the IL-1 beta autocrine stimulation of growth of human B1 myeloid tumor cells by preventing the processing of pre-IL-1 beta to mature cytokine. Benzoquinone was also shown to completely inhibit the ability of the SH-dependent IL-1 beta converting enzyme. Thus benzene-induced bone marrow hypocellularity may result from apoptosis of hematopoietic progenitor cells brought about by lack of essential cytokines and deficient IL-1 alpha production subsequent to the inhibition of calpain by p-benzoquinone and the prevention of pre-IL-1 processing.

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