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.

Improved intestinal absorption of paclitaxel by mixed micelles self-assembled from vitamin E succinate-based amphiphilic polymers and their transcellular transport mechanism and intracellular trafficking routes

“…These findings were partially evidenced by the results of in situ intestinal absorption ( Figure 3(D) ). A possible explanation for this phenomenon might be assigned to enhancement of PTX solubility, involvement of multiple transcytosis pathway ( Figure 4(E) ) and alleviation of P-gp mediated efflux through masking effect by the micelles and inhibition of P-gp activity by their components (Li et al., 2014 ).…”

“…Caco-2 cell monolayers were obtained by seeding Caco-2 cells at a density of 2 × 10 5 cells/well on Transwell ® polycarbonate membrane inserts and culturing for about 21 days after seeding (Zhang et al., 2010a , b ; Li et al., 2014 ). The culture medium was refreshed every other day as the apical (AP) and basolateral (BL) compartments received 0.5 and 1.5 mL of culture medium, respectively.…”

Sirolimus-loaded polymeric micelles with honokiol for oral delivery

“…In our past work, a remarkable potential inhibitory effect of mPEG‐PLA on P‐gp activity was fully confirmed. mPEG‐PLA decreased intracellular ATP level, exerting no influence on plasma membrane fluidity, P‐gp ATPase activity and P‐gp level [55]. Interestingly, downregulating the expression of P‐gp by honokiol, together with decreasing intracellular ATP level of Caco‐2 cells by mPEG‐PLA‐based PMs, synergistically enhanced the transport of sirolimus in Caco‐2 cells and intestine, which was shown to be of potential clinical prospects.…”

Polymeric micelles for oral drug administration enabling locoregional and systemic treatments

“…TPGS [51], N-octyl-O-sulfate chitosan (NOSC) [15,16,79], Pluronic and Tetronic unimers with an intermediate PPO length (30 --60 units) and lowto-medium HLB [35,36,39,40], monomethoxy poly(ethylene glycol)-poly(D, L-lactic acid) [80] and several other diblock copolymers [81] have been identified as potent inhibitors of efflux pumps. For example, oral bioavailability of paclitaxel (an anticancer agent with water solubility < 1 µg/ml) was enhanced sixfold when formulated in NOSC micelles compared to Taxol Ò solutions [15,16,79].…”