Natesan S, Lukacova V, Peng M, Subramaniam R, Lynch S, Wang Z, Tandlich R, Balaz S. Structure-based prediction of drug distribution across the headgroup and core strata of a phospholipid bilayer using surrogate phases.
Mol Pharm 2014;
11:3577-95. [PMID:
25179490 PMCID:
PMC4186683 DOI:
10.1021/mp5003366]
[Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
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Solvation of drugs in the core (C)
and headgroup (H) strata of
phospholipid bilayers affects their physiological transport rates
and accumulation. These characteristics, especially a complete drug
distribution profile across the bilayer strata, are tedious to obtain
experimentally, to the point that even simplified preferred locations
are only available for a few dozen compounds. Recently, we showed
that the partition coefficient (P) values in the
system of hydrated diacetyl phosphatidylcholine (DAcPC) and n-hexadecane (C16), as surrogates of the H- and C-strata
of the bilayer composed of the most abundant mammalian phospholipid,
PC, agree well with the preferred bilayer location of compounds. High P values are typical for lipophiles accumulating in the
core, and low P values are characteristic of cephalophiles
preferring the headgroups. This simple pattern does not hold for most
compounds, which usually have more even distribution and may also
accumulate at the H/C interface. To model complete distribution, the
correlates of solvation energies are needed for each drug state in
the bilayer: (1) for the H-stratum it is the DAcPC/W P value, calculated as the ratio of the C16/W and C16/DAcPC (W for
water) P values; (2) for the C-stratum, the C16/W P value; (3) for the H/C interface, the P values for all plausible molecular poses are characterized using
the fragment DAcPC/W and C16/W solvation parameters for the parts
of the molecule embedded in the H- and C-strata, respectively. The
correlates, each scaled by two Collander coefficients, were used in
a nonlinear, mass-balance based model of intrabilayer distribution,
which was applied to the easily measurable overall P values of compounds in the DMPC (M = myristoyl) bilayers and monolayers
as the dependent variables. The calibrated model for 107 neutral compounds
explains 94% of experimental variance, achieves similar cross-validation
levels, and agrees well with the nontrivial, experimentally determined
bilayer locations for 27 compounds. The resulting structure-based
prediction system for intrabilayer distribution will facilitate more
realistic modeling of passive transport and drug interactions with
those integral membrane proteins, which have the binding sites located
in the bilayer, such as some enzymes, influx and efflux transporters,
and receptors. If only overall bilayer accumulation is of interest,
the 1-octanol/W P values suffice to model the studied
set.
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