Suppression of ZIP8 expression is a common feature of cadmium-resistant and manganese-resistant RBL-2H3 cells

Abstract

Rat basophilic leukemia RBL-2H3 cells show markedly high sensitivity to both CdCl₂ and MnCl₂ compared with other rat cell lines, due to efficient accumulation of cadmium and manganese. To clarify the roles of metal transporters in hyperaccumulation of cadmium and manganese in RBL-2H3 cells, Cd-resistant and Mn-resistant cells were developed from RBL-2H3 cells by continuous exposure to CdCl₂ and MnCl₂, respectively. The established Cd-resistant (RBL-Cdr) and Mn-resistant (RBL-Mnr) cells exhibited about 20 times higher LC₅₀ values of CdCl₂ and MnCl₂, respectively, than parental RBL-2H3 cells, and showed cross-resistance to each metal. The resistance to cadmium and manganese was primarily conferred by a marked decrease in the uptake of both metals. RBL-Cdr cells also showed cross-resistance to HgCl₂ and AgNO₃ probably due to enhanced expression of metallothionein. Among the possible transporters involved in the uptake of Cd²⁺ and Mn²⁺, the expression of ZIP8 (Zrt-, Irt-related protein 8), encoded by Slc39a8, showed a marked suppression in both RBL-Cdr and RBL-Mnr cells. These results suggest that ZIP8 plays a pivotal role in the transport and toxicity of Cd²⁺ and Mn²⁺ in RBL-2H3 cells.