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Mechanisms of P-gp inhibition and effects on membrane fluidity of a new rifampicin derivative, 1,8-dibenzoyl-rifampicin.

Toxicol Lett. 2013 May 16;

Authors: Vilas-Boas V, Silva R, Nunes C, Reis S, Ferreira L, Vieira C, Carvalho F, Bastos MD, RemiĆ£o F


PURPOSE: To assess P-glycoprotein (P-gp)-modulation ability and the mechanisms of P-gp inhibition mediated by a new synthetic rifampicin derivative, 1,8-dibenzoyl-rifampicin (DiBenzRif), in an in vitro model of the blood-brain barrier (BBB), RBE4 cells, and in membrane mimetic models (liposomes). METHODS: P-gp expression (western blot) and activity [rhodamine-123 accumulation studies] were assessed until 72h of exposure to DiBenzRif. The effects on intracellular ATP levels and on P-gp ATPase activity were studied using luciferin-luciferase bioluminescence assay. Membrane fluidity changes were tracked by steady-state anisotropy measurements. Non-P-gp-related rhodamine-123 accumulation was evaluated using liposomes prepared with the main lipids present in RBE4 cell membranes. RESULTS: A significant increase in intracellular rhodamine-123 content was observed in DiBenzRif-treated cells at all tested time-points. This effect was associated with a significant reduction in ATP intracellular levels, the inhibition of P-gp ATPase activity and a significant increase in membrane fluidity. DiBenzRif also favoured rhodamine-123 accumulation in a liposomal model of RBE4 cells, suggesting that it may be useful in increasing intracellular levels of substances that passively diffuse into the cells. CONCLUSION: DiBenzRif-induced inhibitory effect on P-gp increases xenobiotic accumulation in BBB cells, which may contribute to the development of therapeutic adjuvants to enhance brain penetration of drugs.

PMID: 23685082 [PubMed - as supplied by publisher]