ABSTRACT
Membrane transporters P-glycoprotein [P-gp; multidrug resistance 1 (MDR1)], multidrug resistance-associated protein (MRP) 2, and breast cancer resistance protein (BCRP) affect drug absorption and disposition and can also mediate drug-drug interactions leading to safety/toxicity concerns in the clinic. Challenges arise with interpreting cell-based transporter assays when substrates or inhibitors affect more than one actively expressed transporter and when endogenous or residual transporter activity remains following overexpression or knockdown of a given transporter. The objective of this study was to selectively knock out three drug efflux transporter genes (MDR1, MRP2, and BCRP), both individually as well as in combination, in a subclone of Caco-2 cells (C2BBe1) using zinc finger nuclease technology. The wild-type parent and knockout cell lines were tested for transporter function in Transwell bidirectional assays using probe substrates at 5 or 10 µM for 2 hours at 37°C. P-gp substrates digoxin and erythromycin, BCRP substrates estrone 3-sulfate and nitrofurantoin, and MRP2 substrate 5-(and-6)-carboxy-2',7'-dichlorofluorescein each showed a loss of asymmetric transport in the MDR1, BCRP, and MRP2 knockout cell lines, respectively. Furthermore, transporter interactions were deduced for cimetidine, ranitidine, fexofenadine, and colchicine. Compared with the knockout cell lines, standard transporter inhibitors showed substrate-specific variation in reducing the efflux ratios of the test compounds. These data confirm the generation of a panel of stable Caco-2 cell lines with single or double knockout of human efflux transporter genes and a complete loss of specific transport activity. These cell lines may prove useful in clarifying complex drug-transporter interactions without some of the limitations of current chemical or genetic knockdown approaches.
Subject(s)
ATP-Binding Cassette Transporters/metabolism , Enterocytes/metabolism , Multidrug Resistance-Associated Proteins/metabolism , Neoplasm Proteins/metabolism , Xenobiotics/metabolism , ATP Binding Cassette Transporter, Subfamily B/antagonists & inhibitors , ATP Binding Cassette Transporter, Subfamily B/genetics , ATP Binding Cassette Transporter, Subfamily B/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/antagonists & inhibitors , ATP-Binding Cassette Transporters/genetics , Biological Transport/drug effects , Caco-2 Cells , Cell Membrane Permeability/drug effects , Clone Cells , Drug Evaluation, Preclinical/methods , Drug Interactions , Enterocytes/drug effects , Gene Knockout Techniques , Humans , Multidrug Resistance-Associated Protein 2 , Multidrug Resistance-Associated Proteins/antagonists & inhibitors , Multidrug Resistance-Associated Proteins/genetics , Neoplasm Proteins/antagonists & inhibitors , Neoplasm Proteins/genetics , RNA, Messenger/metabolism , Xenobiotics/analysis , Xenobiotics/pharmacologyABSTRACT
A limitation of the traditional Caco-2 cell assay for measuring transporter-mediated efflux of a given substrate is that it is not possible to determine which specific transporter is involved. The methods in this unit describe an approach for generating specific transporter knockout cell lines that can be used to test efflux with any desired substrates. In this approach, human C2BBe1 cells (a subclone of Caco-2 cells) are nucleofected with specific zinc finger nucleases (ZFN), which can be designed to target any gene of interest and generate a double-stranded break. The cell's normal repair mechanisms can then generate targeted deletions (or integrations). A single ZFN can be used to generate a single transporter knockout, or multiple ZFNs can be used to knock out more than one transporter. This unit provides all methods needed to design the required plasmids, generate and identify transporter knockout cell lines, verify their membrane integrity, and test them with functional transport assays.
Subject(s)
ATP-Binding Cassette Transporters/genetics , Deoxyribonucleases, Type II Site-Specific/metabolism , Gene Knockout Techniques/methods , Zinc Fingers , Cell Culture Techniques , Cell Line, Tumor , Cloning, Molecular , DNA Breaks, Double-Stranded , DNA Repair , Deoxyribonucleases, Type II Site-Specific/genetics , Genetic Vectors , Green Fluorescent Proteins/genetics , Humans , Plasmids , TransfectionABSTRACT
Installation of sites for metabolism in the lead compound PHA-767408 was the key focus of the IKK-2 inhaled program. This paper reports our efforts to identify a novel series of aminopyridinecarboxamide-based IKK-2 inhibitors, which display low nanomolar potency against IKK-2 with long duration of action (DOA), and metabolically labile to phase I and/or phase II metabolizing enzymes with potential capability for multiple routes of clearance. Several compounds have demonstrated their potential usefulness in the treatment of asthma and chronic obstructive pulmonary disease (COPD).
Subject(s)
Aminopyridines/chemical synthesis , Asthma/drug therapy , I-kappa B Kinase/antagonists & inhibitors , Niacinamide/analogs & derivatives , Protein Kinase Inhibitors/chemical synthesis , Pulmonary Disease, Chronic Obstructive/drug therapy , Pyrazoles/chemical synthesis , Administration, Inhalation , Aminopyridines/chemistry , Aminopyridines/pharmacology , Binding, Competitive , Drug Design , HEK293 Cells , Humans , Indazoles/chemistry , Indazoles/metabolism , Indazoles/pharmacology , Isonicotinic Acids/chemistry , Isonicotinic Acids/metabolism , Isonicotinic Acids/pharmacology , Microsomes, Liver/drug effects , Models, Molecular , Molecular Structure , Molecular Targeted Therapy , Niacinamide/chemical synthesis , Niacinamide/chemistry , Niacinamide/metabolism , Niacinamide/pharmacology , Phenethylamines/metabolism , Potassium Channel Blockers/metabolism , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Pyrazoles/chemistry , Pyrazoles/metabolism , Pyrazoles/pharmacology , Structure-Activity Relationship , Sulfonamides/metabolismABSTRACT
Nuclear factor-kappaB (NF-kappaB) is one of the major families of transcription factors activated during the inflammatory response in asthma and chronic obstructive pulmonary disease. Inhibitory factor-kappaB kinase 2 (IKK-2) has been shown to play a pivotal role in cytokine-induced NF-kappaB activation in airway epithelium and in disease-relevant cells. Nevertheless, the potential toxicity of specific IKK-2 inhibitors may be unacceptable for oral delivery in chronic obstructive pulmonary disease. Therefore, local delivery to the lungs is an attractive alternative that warrants further exploration. Here, we describe potent and selective small-molecule IKK-2 inhibitors [8-(5-chloro-2-(4-methylpiperazin-1-yl)isonicotinamido)-1-(4-fluorophenyl)-4,5-dihydro-1H-benzo[g]indazole-3-carboxamide (PHA-408) and 8-(2-(3,4-bis(hydroxymethyl)-3,4-dimethylpyrrolidin-1-yl)-5-chloroisonicotinamido)-1-(4-fluorophenyl)-4,5-dihydro-1H-benzo-[g]indazole-3-carboxamide (PF-184)] that are competitive for ATP have slow off-rates from IKK-2 and display broad in vitro anti-inflammatory activities resulting from NF-kappaB pathway inhibition. Notably, PF-184 has been designed to have high systemic clearance, which limits systemic exposure and maximizes the effects locally in the airways. We used an inhaled lipopolysaccharide-induced rat model of neutrophilia to address whether inhibiting NF-kappaB activation locally within the airways would show anti-inflammatory effects in the absence of systemic exposure. PHA-408, a low-clearance compound previously shown to be efficacious orally in a rodent model of arthritis, dose-dependently attenuated inhaled lipopolysaccharide-induced cell infiltration and cytokine production. Interestingly, PF-184 produced comparable dose-dependent anti-inflammatory activity by intratracheal administration and was as efficacious as intratracheally administered fluticasone propionate (fluticasone). Together, these results support the potential therapeutic utility of IKK-2 inhibition in inflammatory pulmonary diseases and demonstrate anti-inflammatory efficacy of an inhaled IKK-2 inhibitor in a rat airway model of neutrophilia.
