The Metabolism of Methazolamide in Immortalized Human Keratinocytes, HaCaT Cells

Title:The Metabolism of Methazolamide in Immortalized Human Keratinocytes, HaCaT Cells

Volume: 10 Issue: 4

Author(s): Tetsuo Sasabe*, Shinichiro Maeda, Kenichi Kishida, Mariko Yamano, Yoshihiro Miwa and Toshihiro Sugiyama

Affiliation:

• Department of Ophthalmology, Osaka Prefectural Medical Center for Respiratory and Allergic Diseases, 3-7-1 Habikino, Habikino-shi Osaka 583-8588,Japan

Keywords: Cytochrome P450, glutathione, methazolamide, N-[3-methyl-5-sulfo-1, 3, 4-thiadiazo-2(3H)-ylidene]acetamide, Stevens-Johnson syndrome, sulfenic acid, sulfonic acid, toxic epidermal necrolysis.

Abstract: Objective: Drug therapy is occasionally accompanied by an idiosyncratic severe toxicity, which occurs very rarely, but can lead to patient mortality. Methazolamide, an anti-glaucomatous agent, could cause severe skin eruptions called Stevens-Johnson syndrome/toxic epidermal necrolyis (SJS/TEN). Its precise etiology is still uncertain. In this study, the metabolism of methazolamide was investigated in immortalized human keratinocytes to reveal the possible mechanism which causes SJS/TEN.

Methods: The metabolism of methazolamide was studied using immortalized human keratinocytes, HaCaT cells. HPLC was used to isolate a metabolite from the culture medium. Mass spectrometry (LCMS/ MS) was employed for its characterization. Three typical chemical inducers were assessed for the inducibility of cytochrome P450, and methimazole was used as the inhibitor of flavin-containing monooxygenase (FMO).

Results: A sulfonic acid, N-[3-methyl-5-sulfo-1,3,4-thiadiazol-2(3H)-ylidene]acetamide (MSO) was identified as the final metabolite. Dexamethasone and β-naphthoflavone behaved as an inducer of cytochrome P450 in the metabolism, but isoniazid did not. The effect of methimazole was not consistent. We did not detect any glucuronide nor any mercapturic acid (N-acetylcysteine conjugate).

Conclusion: N-[3-methyl-5-sulfo-1,3,4-thiadiazol-2(3H)-ylidene]acetamide (MSO) is not considered to be a direct product of an enzymatic reaction, but rather an auto-oxidation product of N-[3-methyl-5- sulfe-1,3,4-thiadiazol-2(3H)-ylidene]acetamide, a chemically unstable sulfenic acid, which is produced by cytochrome P450 from the β-lyase product of cysteine conjugate of methazolamide. MSO is considered to be susceptible to glutathione and to return to glutathione conjugate of methazolamide, forming a futile cycle. A hypothetical scenario is presented as to the onset of the disease.

Cite this article as:

Sasabe Tetsuo*, Maeda Shinichiro, Kishida Kenichi, Yamano Mariko, Miwa Yoshihiro and Sugiyama Toshihiro, The Metabolism of Methazolamide in Immortalized Human Keratinocytes, HaCaT Cells, Drug Metabolism Letters 2016; 10 (4) . https://dx.doi.org/10.2174/1872312811666170127160931

DOI https://dx.doi.org/10.2174/1872312811666170127160931	Print ISSN 1872-3128
Publisher Name Bentham Science Publisher	Online ISSN 1874-0758