Arsenic undergoes significant speciation changes upon incubation of contaminated rice with human colon micro biota.
Cellular and animal studies involving MMA(III) (monomethyl arsonous acid) and DMA(III) (dimethyl arsinous acid) have indicated that their toxicities meet or exceed that of iAs. Thiolated arsenic metabolites were observed in urine after oral exposure of inorganic arsenic in some studies. For these species, the toxicological profile was not yet fully characterized in human cells. Some studies revealed that trivalent organoarsenic species are well absorbed in the intestine compared to iAs. However, other studies also indicated that a significant amount of rice-bound As reaches the colon, which may be attributed to the fibre-rich nature of the rice. Studies have revealed that microorganisms from the gut environment are important contributors to arsenic speciation changes. We aimed to study how the gut microbial metabolism affects As in different rice matrices. This was done in vitro using colon suspension from the Simulator of the Human Intestinal Microbial Ecosystem (SHIME system). Significant amounts of MMA(III), DMA(III) and MMMTA(V) were formed due to microbial metabolic processes like methylation and thiolation. These results suggested that presystemic metabolism by human gut micro biota should not be neglected in risk assessment studies. In this context, also toxicity and absorption of thiolated species by mammalian cells should be further investigated.
Laboratory of Analytical Chemistry and Applied Eco Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium. Electronic address: pradeep.alava@ugent.be.
Pradeep
P
Alava
Filip
F
Tack
Gijs Du
GD
Laing
Tom
T
Van de Wiele
D001151:Arsenic / Q000032:analysis* / Q000378:metabolism / Q000652:urine; D001152:Arsenicals / Q000378:metabolism; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D003106:Colon / Q000187:drug effects / Q000382:microbiology*; D005506:Food Contamination; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D008954:Models, Biological; D012275:Oryza; D012997:Solvents; D013438:Sulfhydryl Compounds / Q000737:chemistry
D001152:Arsenicals; D012997:Solvents; D013438:Sulfhydryl Compounds; D001151:Arsenic