[Menthol promotes cytokine secretion in human bronchial epithelial BEAS-2B cells by activating transient receptor potential melastatin 8 (TRPM8)].

Objective To explore the role of transient receptor potential melastatin 8 (TRPM8) in the expression of airway epithelial-derived cytokines interleukin 25 (IL-25), IL-33 and thymic stromal lymphopoietin (TSLP) in human bronchial epithelial BEAS-2B cells induced by menthol and its related signal transduction mechanism. Methods BEAS-2B cells were treated with 2 mmol/L menthol for 1, 2, 3 and 4 hours. The groups with the higher expression of IL-25, IL-33, TSLP or Ca2+ were chosen to carry out the following experiments. The cells were transfected with siRNA of TRPM8 (si-TRPM8) or negative control siRNA (si-NC) and pretreated with intracellular calcium chelator BAPTA-AM, nuclear factor κB (NF-κB) inhibitor pyrrolidine dithiocarbamate (PDTC), and then intervened with menthol. Cell survival rate was measured by CCK-8 assay. The mRNA levels of IL-25, IL-33 and TSLP were detected by real-time quantitative PCR. The protein levels of IL-25, IL-33 and TSLP were detected by ELISA. The intracellular Ca2+ fluorescence intensity was detected by flow cytometry with Fluo-4 AM loading. Western blotting was used to detect the interference efficiency of si-TRPM8 on BEAS-2B cells and its effect on the protein expression of NF-κB p65. Results Compared with the blank control group, the mRNA and protein expression of IL-25, IL-33 and TSLP, the level of Ca2+, and the protein expression of NF-κB p65 were significantly up-regulated in the menthol group. After knock-down of TRPM8, the menthol-induced increases of Ca2+, IL-25, IL-33, TSLP and NF-κB p65 expression were inhibited. Both BAPTA-AM and PDTC could inhibit the high expression of IL-25, IL-33 and TSLP induced by menthol. Conclusion Menthol can induce the secretion of IL-25, IL-33 and TSLP in human BEAS-2B cells by activating TRPM8 which leads to increased Ca2+ concentration and activation of the NF-κB pathway.