Nicorandil inhibits degranulation and TNF-α release from RBL-2H3 cells

Objective: Nicorandil is a potassium channel opener and nitric oxide (NO) donor, and the hypothesis was tested that these modes of action may inhibit cellular degranulation and release of tumour necrosis factor-α (TNF-α).¶Materials and methods: TNF-α and β-hexosaminidase secretion were measured from rat basophilic leukemia cells (RBL-2H3) activated via the high affinity IgE receptor with dinitrophenyl-albumin (DNP-A) challenge in the presence of nicorandil. Inhibitors of K+ openers and NO were pre-incubated with the RBL-2H3 cells to determine the principal mode of action.¶Results: Nicorandil significantly inhibited the release of TNF-α in a dose-dependent manner (p < 0.001, ANOVA) reaching a maximum inhibition of DNP-A 74.1% at 10-3 M, (p < 0.001). Similarly it inhibited β-hexosaminidase release (p < 0.001, ANOVA) with maximal inhibition at 10-3 M (p < 0.001). Other K+ openers did not show this effect. Neither the potassium channel blocker glibenclamide nor the guanylyl cyclase inhibitor, ODQ, could reverse this inhibition, but when added in combination reduced the effect by 47%.¶Conclusions: Nicorandil is able to inhibit degranulation and TNF-α release of RBL cells stimulated through the IgE receptor, and requires both the K+ opening and nitric oxide donor activity, which may represent a novel method for inhibiting cytokine release.