title: Lysosomal sequestration (trapping) of lipophilic amine (cationic amphiphilic) drugs in immortalized human hepatocytes (Fa2N-4 cells).
abstract: Lipophilic (logP > 1) and amphiphilic drugs (also known as cationic amphiphilic drugs) with ionizable amines (pKa > 6) can accumulate in lysosomes, a process known as lysosomal trapping. This process contributes to presystemic extraction by lysosome-rich organs (such as liver and lung), which, together with the binding of lipophilic amines to phospholipids, contributes to the large volume of distribution characteristic of numerous cardiovascular and central nervous system drugs. Accumulation of lipophilic amines in lysosomes has been implicated as a cause of phospholipidosis. Furthermore, elevated levels of lipophilic amines in lysosomes can lead to high organ-to-blood ratios of drugs that can be mistaken for active drug transport. In the present study, we describe an in vitro fluorescence-based method (using the lysosome-specific probe LysoTracker Red) to identify lysosomotropic agents in immortalized hepatocytes (Fa2N-4 cells). A diverse set of compounds with various physicochemical properties were tested, such as acids, bases, and zwitterions. In addition, the partitioning of the nonlysosomotropic atorvastatin (an anion) and the lysosomotropics propranolol and imipramine (cations) were quantified in Fa2N-4 cells in the presence or absence of various lysosomotropic or nonlysosomotropic agents and inhibitors of lysosomal sequestration (NH4Cl, nigericin, and monensin). Cellular partitioning of propranolol and imipramine was markedly reduced (by at least 40%) by NH4Cl, nigericin, or monensin. Lysosomotropic drugs also inhibited the partitioning of propranolol by at least 50%, with imipramine partitioning affected to a lesser degree. This study demonstrates the usefulness of immortalized hepatocytes (Fa2N-4 cells) for determining the lysosomal sequestration of lipophilic amines.
authors: XenoTech, LLC, Lenexa, Kansas 66219, USA. fkazmi@xenotechllc.com
authors: Faraz
authors: F
authors: Kazmi
authors: Tiffini
authors: T
authors: Hensley
authors: Chad
authors: C
authors: Pope
authors: Ryan S
authors: RS
authors: Funk
authors: Greg J
authors: GJ
authors: Loewen
authors: David B
authors: DB
authors: Buckley
authors: Andrew
authors: A
authors: Parkinson
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000493:pharmacokinetics; D000588:Amines / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology; D000929:Antidepressive Agents, Tricyclic / Q000493:pharmacokinetics; D000069059:Atorvastatin; D002461:Cell Line, Transformed; D004232:Diuretics / Q000493:pharmacokinetics; D022781:Hepatocytes / Q000378:metabolism*; D006538:Heptanoic Acids / Q000493:pharmacokinetics*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000493:pharmacokinetics; D007099:Imipramine / Q000493:pharmacokinetics*; D008247:Lysosomes / Q000378:metabolism*; D008985:Monensin / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D011433:Propranolol / Q000493:pharmacokinetics*; D011758:Pyrroles / Q000493:pharmacokinetics*
chemical_list: D000319:Adrenergic beta-Antagonists; D000588:Amines; D000929:Antidepressive Agents, Tricyclic; D004232:Diuretics; D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011758:Pyrroles; C493330:Red DND-99; D000643:Ammonium Chloride; D008985:Monensin; D011433:Propranolol; D000069059:Atorvastatin; D007099:Imipramine; D009550:Nigericin
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