title: Vaginal expression of efflux transporters and the potential impact on the disposition of microbicides in vitro and in rabbits.
abstract: In order to reach sufficiently high tissue concentrations and thus be effective, vaginally applied anti-HIV microbicides that are active at the level of the immune cells must permeate across the cervicovaginal mucosal layer. Cellular efflux transporters, such as Pgp, BCRP, and MRP-2, have been demonstrated to greatly affect drug disposition at different sites in the body including the intestine and the blood-brain barrier; their possible role on drug uptake from the female genital tract, however, has not been elucidated yet. In the present study, the protein expression of Pgp, BCRP, and MRP-2 in endocervical and vaginal tissue of premenopausal women was confirmed by Western blot analysis. To enable the assessment of transporter effects in vitro, the identification of an appropriate cervicovaginal cell line was pursued. The cervical SiHa cell line was observed to express mRNA of the 3 studied transporters, but only MRP-2 was found to be active. Consequently, the established Caco-2 cell line was utilized as an alternative in which the interaction of 10 microbicide candidates with the efflux transporters was studied. Darunavir, saquinavir, and maraviroc were identified as Pgp and MRP-2 substrates. The impact of Pgp on in vivo drug disposition was further examined for the model Pgp substrate talinolol in rabbits. Its vaginal uptake was significantly reduced by Pgp-mediated efflux when formulated in a neutral but not in an acidic gel. Our findings indicate the expression of a functional Pgp transporter in the vaginal mucosa that may severely reduce the vaginal uptake of Pgp substrates, including certain microbicide candidates, especially in women with an increased vaginal pH.
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, Drug Delivery and Disposition, KU Leuven-University of Leuven , Leuven, Belgium.
authors.forename: Carolien
authors.initials: C
authors.lastname: Grammen
authors.forename: Myriam
authors.initials: M
authors.lastname: Baes
authors.forename: Steven
authors.initials: S
authors.lastname: Haenen
authors.forename: Jasper
authors.initials: J
authors.lastname: Verguts
authors.forename: Koen
authors.initials: K
authors.lastname: Augustyns
authors.forename: Thomas
authors.initials: T
authors.lastname: Zydowsky
authors.forename: Paolo
authors.initials: P
authors.lastname: La Colla
authors.forename: Patrick
authors.initials: P
authors.lastname: Augustijns
authors.forename: Joachim
authors.initials: J
authors.lastname: Brouwers
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000378:metabolism*; D001692:Biological Transport; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism*; D000089762:Multidrug Resistance-Associated Protein 2; D011817:Rabbits; D014621:Vagina / Q000378:metabolism
chemical_list: C000715087:ABCC2 protein, human; D000890:Anti-Infective Agents; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2
keywords: efflux transporters; in vitro transport; in vivo rabbit study; microbicides; vaginal drug uptake