Induction and activation of P-glycoprotein by dihydroxylated xanthones protect against the cytotoxicity of the P-glycoprotein substrate paraquat.
Xanthones are a family of compounds with several known biological activities and therapeutic potential for which information on their interaction with membrane transporters is lacking. Knowing that P-glycoprotein (P-gp) acts as a cellular defense mechanism by effluxing its toxic substrates, the aim of this study was to investigate the potential of five dihydroxylated xanthones as inducers of P-gp expression and/or activity and to evaluate whether they could protect Caco-2 cells against the cytotoxicity induced by the toxic P-gp substrate paraquat (PQ). After 24 h of incubation, all tested xanthones caused a significant increase in both P-gp expression and activity, as evaluated by flow cytometry using the UIC2 antibody and rhodamine 123, respectively. Additionally, after a short 45-min incubation, all the tested xanthones induced a rapid increase in P-gp activity, indicating direct pump activation without increased P-gp protein expression. The tested compounds also increased P-gp ATPase activity in MDR1-Sf9 membrane vesicles, demonstrating to be P-gp substrates. Moreover, when simultaneously incubated with PQ, all xanthones significantly reduced the cytotoxicity of the herbicide, and these protective effects were completely reversed upon incubation with a specific P-gp inhibitor. In silico studies evaluating the interactions between xanthones and P-gp in the presence of PQ suggested that a co-transport mechanism may be operating. A quantitative structure-activity relationship model was developed and validated, and the maximal partial charge for an oxygen atom was the descriptor predicted as being implicated in P-gp activation by the dihydroxylated xanthones. These results disclose new perspectives in preventing PQ- and other P-gp substrates-induced poisonings.
REQUIMTE, Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal, rsilva@ff.up.pt.
Renata
R
Silva
Emília
E
Sousa
Helena
H
Carmo
Andreia
A
Palmeira
Daniel José
DJ
Barbosa
Mariline
M
Gameiro
Madalena
M
Pinto
Maria de Lourdes
Mde L
Bastos
Fernando
F
Remião
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000819:agonists / Q000096:biosynthesis / Q000737:chemistry; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D006540:Herbicides / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D006801:Humans; D006900:Hydroxylation; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects* / Q000473:pathology; D062105:Molecular Docking Simulation; D015394:Molecular Structure; D010269:Paraquat / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D020011:Protective Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013997:Time Factors; D015854:Up-Regulation; D044004:Xanthones / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D006540:Herbicides; D020011:Protective Agents; D044004:Xanthones; D010269:Paraquat