Participation of b0,+ and B0,+ systems in the transport of mercury bound to cysteine in intestinal cells

Abstract

The main source of exposure to mercury (Hg) as divalent inorganic Hg [Hg(ii)] and methylmercury (CH3Hg) is the diet, in which complexes with the amino acid cysteine (Hg-Cys) may be found. The present study explores the participation of the b0,+ and B0,+ amino acid transporters in the intestinal transport of mercuric conjugates with cysteine [Hg(ii)-Cys and CH3Hg-Cys], using Caco-2 cells as a model of the intestinal epithelium. For this purpose, the effects of b0,+ and B0,+ gene silencing upon Hg(ii)-Cys and CH3Hg-Cys uptake were evaluated. In addition, after treatment with Hg-Cys complexes, we evaluated the differential expression of b0,+ and B0,+ and of transporters belonging to the LAT and y+LAT systems, which have also been described as possible participants in the Hg-Cys transport. The results show that b0,+ and B0,+ silencing reduces intracellular accumulation of Hg(ii)-Cys (39 ± 8%) and CH3Hg-Cys (16 ± 3%), respectively. These results, together with the existing literature, suggest that these transporters are involved in the transport of Hg-Cys in intestinal cells. On the other hand, the differential expression studies reflect an increase in LAT and y+LAT transporters after treatment with Hg-Cys, which could indicate their participation in the cellular elimination of such complexes, as has been previously suggested.