Graduate student Mohamad Hamdi publishes about arsenic toxicity

Biomedical Sciences: Biological Communications graduate student Mohamad Hamdi is the lead author on a recent paper about arsenic toxicity (Identification of an S-adenosylmethionine (SAM) dependent arsenic methyltransferase in Danio rerio) published in the July 15 issue of the journal Toxicology and Applied Pharmacology (Volume 262, Pages 185-193). Hamdi’s supervisor is CBR member Zijuan Liu, of the Department of Biological Sciences. Coauthors include graduate students Janell Hallauer and Joseph McDermott. This paper is an outgrowth of Hamdi’s 2009 paper, featured previously in the CBR News. The study makes use of a zerbrafish (Danio rerio), which is a valuable vertebrate model for studying arsenic toxicity in humans. Hamdi summarizes his research clearly at the start of the discussion section of the paper, reproduced below (with references deleted).

“Due to the abundance of arsenic in the environment and diversity of mechanisms through which arsenic causes toxicity, it is important to understand the regulation of chemical metabolism, distribution, and bodily clearance of arsenic. The methylation of arsenic is one of the key variables and thus detailed understanding of mechanism of arsenic methyltransferases is crucial…. AS3MT is considered the major enzyme in arsenic biomethylation. …. AS3MT transforms arsenic into less toxic DMA^V [dimethylarsinic acid] which is more easily cleared from the body. However, it remains an open question whether AS3MT is responsible for the formation of more toxic intermediates such as MMA^III [monomethylarsonous acid]. This study showed zAs3mt transforms As^III to DMA^V similar to mammalian AS3MT homologs (Fig. 3). The absence of significant MMA^III in zebrafish tissue after arsenic exposure can be explained through MMA^III not being rate limiting in the second round under these exposure conditions.”

The work was supported by a grant (NIH ES016856) to Liu from the National Institutes of Health. The study makes uses an inductively-coupled plasma mass spectrometer (ICP-MS) to measure arsenic levels. Oakland University recently purchased an ICP-MS for use in biomedical research, in part with funds from the CBR.