Effects of curcumin, a biologically active ingredient of turmeric, were tested on the Ca2+transients induced by the activation of α7 subunit of the human nicotinic acetylcholine (α7nACh) receptor expressed in SH-EP1 cells. Curcumin caused a significant potentiation of choline (1 mM)-induced Ca2+ transients with an EC50 value of 133 nM. The potentiating effect of curcumin was not observed in Ca2+ transients induced by high K+ (60 mM) containing solutions or activation of α4β2 nACh receptors and the extent of curcumin potentiation was not altered in the presence of Ca2+ channel antagonists nifedipine (1 μM), verapamil (1 μM), ω-conotoxin (1 μM), and bepridil (10 μM). Noticeably the effect of curcumin was not observed when curcumin and choline were co-applied without curcumin pre-incubation. The effect of curcumin on choline-induced Ca2+ transients was not reversed by pre-incubation with inhibitors of protein C, A, and CaM kinases. Metabolites of curcumin such as tetrahydrocurcumin, demethylcurcumin, and didemethylcurcumin also caused potentiation of choline-induced Ca2+ transients. Notably, specific binding of [125I]-bungarotoxin was not altered in the presence of curcumin. Collectively, our results indicate that curcumin allosterically potentiate the function of the α7-nACh receptor expressed in SH-EP1 cells.
Nebrisi, E.E., Al Kury, L.T., Yang, K.-H.S., Jayaprakash, P., Howarth, F.C., Kabbani, N., Oz, M., Curcumin potentiates the function of human α7-nicotinic acetylcholine receptors expressed in SH-EP1 cells, Neurochemistry International (2018), doi: 10.1016/j.neuint.2017.12.010.
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