RESUMO
Scaffold proteins such as radixin help to modulate the plasma membrane localization and transport activity of the multidrug resistance-associated protein 2 (MRP2/ABCC2) and P-glycoprotein (P-gp/ABCB1) efflux transporters in the liver. We examined changes in radixin expression and interaction with efflux transporters in adjuvant-induced arthritic (AA) rats, an animal model of rheumatoid arthritis, as well as in human liver cancer (HepG2) cells because inflammation affects drug pharmacokinetics via the efflux transporters. The expression levels of radixin and phosphorylated radixin (p-radixin) were measured 24 h after treatment with inflammatory cytokines comprising tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6 or sodium nitroprusside (SNP; a nitric oxide donor). The protein levels of radixin, MRP2, and P-gp in the rat liver were next examined. We also investigated whether inflammation affected the formation of complexes between radixin and MRP2 or P-gp. The mRNA and protein levels of radixin in HepG2 cells were significantly decreased by TNF-α treatment, while minimal changes were observed after treatment with IL-1ß, IL-6 or SNP. TNF-α also significantly decreased the protein levels of p-radixin, suggesting that TNF-α inhibited the activation of radixin and thereby reduced the activity of the efflux transporters. Complex formation of radixin with MRP2 and P-gp was significantly decreased in AA rats but this was reversed by prednisolone and dexamethasone treatment, indicating that decreased interactions of radixin with MRP2 and P-gp likely occur during liver inflammation. These data suggest that liver inflammation reduces radixin function by decreasing its interactions with MRP2 and P-gp.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Transportadores de Cassetes de Ligação de ATP/metabolismo , Artrite Experimental/metabolismo , Proteínas do Citoesqueleto/metabolismo , Fígado/metabolismo , Proteínas de Membrana/metabolismo , Animais , Anti-Inflamatórios/farmacologia , Artrite Experimental/genética , Artrite Experimental/microbiologia , Citocinas/farmacologia , Proteínas do Citoesqueleto/genética , Feminino , Células Hep G2 , Humanos , Fígado/efeitos dos fármacos , Proteínas de Membrana/genética , Proteína 2 Associada à Farmacorresistência Múltipla , Mycobacterium , Doadores de Óxido Nítrico/farmacologia , Fosforilação , Ligação Proteica , Ratos Sprague-DawleyRESUMO
Pathophysiological changes are associated with alterations in the expression and function of numerous ADME-related proteins. We have previously demonstrated that the membrane localization of ATP-binding cassette (ABC) transporters in liver was decreased without change of total expression levels in adjuvant-induced arthritis (AA) in rats. Ezrin/radixin/moesin (ERM) proteins are involved in localization of some ABC transporters in canalicular membrane. The mRNA levels of radixin decreased significantly in liver but not kidney, small intestine, and brain. The mRNA levels of ezrin and moesin did not change in AA. The membrane localization of radixin was reduced in liver of AA and the ratios of activated radixin (p-radixin) to total radixin were decreased in AA, although the protein levels of radixin did not change in homogenate and membrane protein. To clarify whether AA affects the linker functions of ERM proteins, we examined the interactions between ERM proteins and ABC transporters. The interactions between radixin and ABC transporters were decreased in AA. In vitro studies using human hepatoma HepG2 cells showed that interleukin-1ß decreased the mRNA levels of radixin and colocalization of radixin and Mrp2. Our results show that the decreased radixin functions affect the interaction between radixin and ABC transporters in inflammation.
