Assessing the Perturbing Effects of Drugs on Lipid Bilayers Using Gramicidin Channel-Based In Silico and In Vitro Assays

Abstract

Partitioning of bioactive molecules, including drugs, into cell membranes may produce indiscriminate changes in membrane protein function. As a guide to safe drug development, it therefore becomes important to be able to predict the bilayer-perturbing potency of hydrophobic/amphiphilic drugs candidates. Toward this end, we exploited gramicidin channels as molecular force probes and developed in silico and in vitro assays to measure drugs’ bilayer-modifying potency. We examined eight drug-like molecules that were found to enhance or suppress gramicidin channel function in a thick 1,2-dierucoyl- sn -glycero-3-phosphocholine (DC 22:1 PC) but not in thin 1,2-dioleoyl- sn -glycero-3-phosphocholine (DC 18:1 PC) lipid bilayer. The mechanism underlying this difference was attributable to the changes in gramicidin dimerization free energy by drug-induced perturbations of lipid bilayer physical properties and bilayer–gramicidin interactions. The combined in silico and in vitro approaches, which allow for predicting the perturbing effects of drug candidates on membrane protein function, have implications for preclinical drug safety assessment.

Amphiphiles capsaicin and triton X-100 regulate the chemotherapy drug colchicine’s membrane adsorption and ion pore formation potency

“…Secondly, the quantitatively measured strong correlation between either amphiphile’s effects on membrane adsorption and ion pore forming potency of the CD molecules hints that the coexistence of MAAs with amphiphiles in the membrane vicinity (or inside the membrane) may influence each other’s (especially considered here the effects of amphiphiles on CD’s functions) effects on the membrane, depending on their relative concentrations, in various ways, such as influencing in membrane adsorption and accumulation inside, formation of stable structures, etc. These results with other sets of studies ( Lundbaek et al, 2005 , Greisen et al, 2011 , Ashrafuzzaman et al, 2007 Sun et al, 2020 ) altogether raise our general understanding of the universality of the effects of MAAs (independently or their binary combinations) on bilayer physical properties. We can thus state that despite any MAA (peptides, CDs or amphiphiles) may not disrupt lipid bilayer electrical barrier properties, especially at low nM-μM concentrations in membrane bathing aqueous buffer, it may still exert effects on other types of bilayer physical properties and thus subsequently regulate the effects of other MAAs on cell membrane.…”

The Antimicrobial Peptide Gramicidin S Enhances Membrane Adsorption and Ion Pore Formation Potency of Chemotherapy Drugs in Lipid Bilayers

“…Therefore, GS is predicted to somehow alter the general membrane properties, which subsequently regulates other AMPs’ pore-forming potencies. GS effects are found to be consistent with a large number of membrane active agents (MAAs) amphiphiles and amphipathic molecules, and other drugs that have been reported to increase the values of both stability τ ch and appearance frequency f ch for β-helical gA channels [ 33 , 34 , 35 , 36 , 37 ]. We have also found substantial effects of amphiphiles triton X-100 (TX100) and capsaicin (Cpsn) on the stability of the appearance frequency of barrel-stave structure forming Alm channels [ 38 ], the details of which appear elsewhere by Ashrafuzzaman and Andersen.…”

Regulation of Gramicidin Channel Function Solely by Changes in Lipid Intrinsic Curvature

“…where is the difference in bilayer deformation energy between the non-conducting monomers (M) and conducting dimers (D) and the energetic contributions from the dimerization per se ( Lundbæk et al, 2010 ; Sun et al, 2020 ).…”