ABSTRACT
We examined the inhibitory effect of cationic polyrotaxanes, which consist of alpha-cyclodextrins threaded on a poly(ethylene glycol) (PEG) chain, on the activity of the intestinal carnitine/organic cation transporter, OCTN2, in OCTN2 gene-transfected HEK293/PDZK1 cells. The cationic polyrotaxanes effectively inhibited the OCTN2-mediated carnitine transport. Polyrotaxanes with a longer PEG chain exhibited a greater inhibitory effect, possibly owing to multivalent interactions with binding sites on OCTN2. These cationic polyrotaxanes were far less cytotoxic than conventional polycations, and are therefore interesting candidates as low-toxicity inhibitors of cation transport at cell surfaces.
Subject(s)
Carnitine/metabolism , Organic Cation Transport Proteins/antagonists & inhibitors , Polyethylene Glycols/pharmacology , Rotaxanes/pharmacology , alpha-Cyclodextrins/pharmacology , Biological Transport/drug effects , Cell Line , Humans , Organic Cation Transport Proteins/genetics , Organic Cation Transport Proteins/metabolism , Polyethylene Glycols/chemistry , Rotaxanes/chemistry , Solute Carrier Family 22 Member 5 , alpha-Cyclodextrins/chemistryABSTRACT
Maltose-polyrotaxane conjugates (Mal-PRXs), in which maltose-conjugated alpha-cyclodextrins (alpha-CDs) are threaded onto a poly(ethylene glycol) (PEG) chain capped with benzyloxycarbonyl-L-tyrosine, were characterized in terms of their molecular motion and the relation to multivalent interactions between the maltose moiety and concanavalin A from Canavalia ensiformis (Con A). Spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) of alpha-CD C(1), maltosyl C(1), and PEG methylene protons in the Mal-PRXs revealed that the mobile motion of alpha-CDs in the polyrotaxane governed the molecular motion of maltosyl groups in alpha-CDs and threading PEG chain. The association constant (Ka) of the Mal-PRXs with 22, 38 and 53% of alpha-CD threading was 5.7 x 10(4), 1.1 x 10(6), and 5.3 x 10(5) (M(-1)-maltose), respectively. The largest Ka value of the Mal-PRX with 38% of alpha-CD threading was well correlated with the T1 and T2 values of maltosyl groups and alpha-CD, suggesting that the mobile motion of maltose-conjugated alpha-CDs in the Mal-PRX contributes to the highest affinity with Con A. Initial rate of binding with Con A was also governed by the mobile motion of maltose-conjugated alpha-CDs. Therefore, we concluded that both highly molecular motion due to the mobile motion of maltose-conjugated alpha-CDs and multivalency of the Mal-PRXs contributes to inducing rapid Con A binding.
