Maie Shaaban Taha

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BACKGROUND: P-glycoprotein (P-gp) is a membrane efflux pump which is overexpressed in Chronic Rhinosinusitis with Nasal Polyps (CRSwNP) and promotes Type 2 inflammation. Glucocorticoids (GC) are substrates of P-gp suggesting that overexpression may additionally contribute to GC resistance in CRSwNP. This study aims to determine whether P-gp inhibition using verapamil enhances mometasone retention and efficacy in nasal polyp explants.

METHODOLOGY: IRB approved study in which organotypic polyp explants were exposed to mometasone (4.15 μg/mL) and verapa- mil (125 μg/mL) as mono and combination therapy. The effect of verapamil on mometasone tissue retention over time was deter- mined using HPLC. The effect of verapamil on mometasone anti-inflammatory function was determined using ELISA for secreted IL-5. Groups were compared using Kruskal-Wallis test.

RESULTS: P-gp expression strongly and significantly inversely correlated with mometasone retention 1hr after exposure, with a ne- arly 6-fold reduction in tissue retention between the lowest and highest P-gp expressing polyp explants. P-gp inhibition reversed this effect and significantly improved mometasone retention at 1hr relative to mometasone alone. The combination of mome- tasone and verapamil significantly reduced IL-5 secretion relative to vehicle control and outperformed either treatment alone.

CONCLUSIONS: Our study confirms that P-gp contributes to mometasone resistance. This P-gp mediated resistance was successfully reversed by addition of the P-gp inhibitor verapamil. Verapamil further significantly enhanced the anti-inflammatory effect of mometasone when given as a combination therapy.

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