Abstract
BACKGROUND: Mast cells exhibit uptake of histamine from the extracellular microenvironment, which can affect the extent of histamine release following their activation. How mast cells take up exogenous histamine, however, is not fully understood. Organic cation transporter-3 (OCT3), which is encoded by Slc22a3, is a bidirectional plasma membrane transporter for small cation molecules (including histamine), which is expressed in many types of cells, including mast cells. However, its precise roles in mast cells remain uncertain. OBJECTIVE: This study examined whether OCT3 plays a role in histamine uptake in mast cells. METHODS: Bone marrow-derived mast cells (BMMCs) obtained from OCT3-deficient (Slc22a3-knockout [Slc22a3-KO]) or wild-type (WT) mice were analyzed by microscopic examination, quantitative PCR, and flow cytometry to assess morphology and differentiation. Intracellular monoamine levels were evaluated by using HPLC and histamine enzyme immunoassay. The FcεRI-mediated activation of BMMCs was evaluated by β-hexosaminidase assay, ELISA, Western blot, and calcium flux assay. Passive cutaneous anaphylaxis reaction was used for in vivo analysis. RESULTS: The WT and Slc22a3-KO mouse BMMCs were comparable in morphology and differentiation. The Slc22a3-KO mouse BMMCs exhibited low intracellular histamine levels associated with low uptake of extracellular histamine and showed a reduction of histamine release following FcεRI activation when compared with WT BMMCs. Compared with WT mice Slc22a3-KO mice exhibited a reduction in passive cutaneous anaphylaxis reaction. CONCLUSION: These findings suggest that OCT3 mediates exogenous histamine uptake by primary mast cells and that deficiency of OCT3 reduces intracellular histamine levels and downregulates IgE-mediated histamine release in mast cells.