title: Avermectin induces P-glycoprotein expression in S2 cells via the calcium/calmodulin/NF-κB pathway.
abstract: Avermectin (AVM) is a macrocyclic lactone agent widely used as a nematicide, acaricide and insecticide in veterinary medicine and plant protection. P-glycoprotein (P-gp) is an ATP-dependent drug efflux pump for xenobiotic compounds, and is involved in multidrug resistance. To understand the development of AVM resistance in invertebrates, we investigated the mechanisms by which AVM affected P-gp expression in Drosophila S2 cells. We found that AVM induced upregulation of P-gp protein expression, increased P-gp ATPase activity and enhanced cellular efflux of the P-gp substrate rhodamine 123 from cells. Furthermore, we observed that AVM-induced expression of P-gp was due to elevation of intracellular calcium concentration ([Ca(2+)](i)). This occurred both directly, by activating calcium ion channels, and indirectly, by activating chloride ion channels. These results are supported by our observations that verapamil, a Ca(2+) channel blocker, and niflumic acid, a chloride channel antagonist, significantly attenuated AVM-induced [Ca(2+)](i) elevation, thereby reducing P-gp expression. Inhibition of P-gp with anti-P-gp antibody or cyclosporine A (a P-gp inhibitor) reduced the AVM-induced elevation of [Ca(2+)](i), implying that P-gp and [Ca(2+)](i) regulate each other. Finally, we found that trifluoperazine, a calmodulin inhibitor, and pyrrolidine dithiocarbamic acid, an NF-κB inhibitor, attenuated the AVM-induced expression of P-gp, suggesting that AVM induces P-gp protein expression via the calmodulin/Relish (NF-κB) signaling pathway.
authors.affiliation: Laboratory of Molecular Toxicology, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Luo
authors.forename: Yin-Jian
authors.initials: YJ
authors.lastname: Sun
authors.forename: Lin
authors.initials: L
authors.lastname: Yang
authors.forename: Shile
authors.initials: S
authors.lastname: Huang
authors.forename: Yi-Jun
authors.initials: YJ
authors.lastname: Wu
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002460:Cell Line; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology; D004351:Drug Resistance / Q000187:drug effects; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D015220:Calcium Channels; D002147:Calmodulin; D018118:Chloride Channels; D002712:Chlorides; D016328:NF-kappa B; D007559:Ivermectin; C019264:avermectin; D002118:Calcium