title: Inhibition mechanism of P-glycoprotein mediated efflux by mPEG-PLA and influence of PLA chain length on P-glycoprotein inhibition activity.
abstract: The present study aimed to investigate the effect of monomethoxy poly(ethylene glycol)-block-poly(D,L-lactic acid) (mPEG-PLA) on the activity of P-glycoprotein (P-gp) in Caco-2 cells and further unravel the relationship between PLA chain length in mPEG-PLA and influence on P-gp efflux and the action mechanism. The transport results of rhodamine 123 (R123) across Caco-2 cell monolayers suggested that mPEG-PLA unimers were responsible for its P-gp inhibitory effect. Furthermore, transport studies of R123 revealed that the inhibitory potential of P-gp efflux by mPEG-PLA analogues was strongly correlated with their structural features and showed that the hydrophilic mPEG-PLA copolymers with an intermediate PLA chain length and 10.20 of hydrophilic-lipophilic balance were more effective at inhibiting P-gp efflux in Caco-2 cells. The fluorescence polarization measurement results ruled out the plasma membrane fluidization as a contributor for inhibition of P-gp by mPEG-PLA. Concurrently, mPEG-PLA inhibited neither basal P-gp ATPase (ATP is adenosine triphosphate) activity nor substrate stimulated P-gp ATPase activity, suggesting that mPEG-PLA seemed not to be a substrate of P-gp and a competitive inhibitor. No evident alteration in P-gp surface level was detected by flow cytometry upon exposure of the cells to mPEG-PLA. The depletion of intracellular ATP, which was likely to be a result of partial inhibition of cellular metabolism, was directly correlated with inhibitory potential for P-gp mediated efflux by mPEG-PLA analogues. Hence, intracellular ATP-depletion appeared to be possible explanation to the inhibition mechanism of P-gp by mPEG-PLA. Taken together, the establishment of a relationship between PLA chain length and impact on P-gp efflux activity and interpretation of action mechanism of mPEG-PLA on P-gp are of fundamental importance and will facilitate future development of mPEG-PLA in the drug delivery area.
authors.affiliation: Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University , Beijing 100191, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Li
authors.forename: Xinru
authors.initials: X
authors.lastname: Li
authors.forename: Yajie
authors.initials: Y
authors.lastname: Gao
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Zhou
authors.forename: Shujin
authors.initials: S
authors.lastname: Ma
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jinwen
authors.initials: J
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Xinglin
authors.initials: X
authors.lastname: Wang
authors.forename: Dongdong
authors.initials: D
authors.lastname: Yin
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects*; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism; D016503:Drug Delivery Systems; D006801:Humans; D019344:Lactic Acid / Q000737:chemistry*; D008560:Membrane Fluidity / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008823:Micelles; D011091:Polyesters / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011108:Polymers / Q000737:chemistry*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008823:Micelles; D011091:Polyesters; D011108:Polymers; C492425:methoxy poly(ethylene glycol)-poly(lactide); D019344:Lactic Acid; D011092:Polyethylene Glycols; C033616:poly(lactide); D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases