A rat air pouch model for evaluating the efficacy and selectivity of 5-lipoxygenase inhibitors

• Published in: European journal of pharmacology 2008-04, Vol.584 (1), p.166-174
• Main Authors: Zweifel, Ben S., Hardy, Medora M., Anderson, Gary D., Dufield, Dawn R., Pufahl, Robert A., Masferrer, Jaime L.
• Format: Article
• Language: English
• Subjects: 5-lipoxygenase; Air; Animals; Arachidonate 5-Lipoxygenase - blood; Arachidonate 5-Lipoxygenase - metabolism; Biological and medical sciences; Biological Assay - methods; Calcimycin - pharmacology; Carrageenan; Cell Line, Tumor; Chromatography, Liquid; CJ-13,610; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Activators - pharmacology; Enzyme-Linked Immunosorbent Assay; Humans; Hydroxyurea - analogs & derivatives; Hydroxyurea - pharmacology; Imidazoles - pharmacology; Immunoglobulin E - immunology; Inflammation - chemically induced; Inflammation - enzymology; Ionophores - pharmacology; Leukotrienes - blood; Leukotrienes - metabolism; Lipoxygenase Inhibitors - pharmacology; Male; Mast Cells - drug effects; Mast Cells - enzymology; Mast Cells - immunology; Medical sciences; Oxidation-Reduction; Pharmacology. Drug treatments; Rats; Rats, Inbred Lew; Reproducibility of Results; Sulfides - pharmacology; Tandem Mass Spectrometry; Zileuton
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2008.01.021

The 5-lipoxygenase (5-LOX) pathway has been associated with a variety of inflammatory diseases including asthma, atherosclerosis, rheumatoid arthritis, pain, cancer and liver fibrosis. Several classes of 5-LOX inhibitors have been identified, but only one drug, zileuton, a redox inhibitor of 5-LOX, has been approved for clinical use. To better evaluate the efficacy of 5-LOX inhibitors for pharmacological intervention, a rat model was modified to test the in vivo efficacy of 5-LOX inhibitors. Inflammation was produced by adding carrageenan into a newly formed air pouch and prostaglandins produced. While macrophages and neutrophils are present in the inflamed pouch, little 5-LOX products are formed. Cellular 5-LOX activation was obtained by adding calcium ionophore (A23187) into the pouch thus providing a novel model to evaluate the efficacy and selectivity of 5-LOX inhibitors. Also, we described modifications to the in vitro 5-LOX enzyme and cell assays. These assays included a newly developed fluorescence-based enzyme assay, a 5-LOX redox assay, an ex vivo human whole blood assay and an IgE-stimulated rat mast cell assay, all designed for maximal production of leukotrienes. Zileuton and CJ-13,610, a competitive, non-redox inhibitor of 5-LOX, were evaluated for their pharmacological properties using these assays. Although both compounds achieved dose-dependent inhibition of 5-LOX enzyme activity, CJ-13,610 was 3–4 fold more potent than zileuton in all-assays. Evaluation of 5-LOX metabolites-by LC/MS/MS and ELISA confirmed that both compounds selectively inhibited all products downstream of 5-hydroperoxy eicosatetraenoic acid (5-HPETE), including 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxoETE), without inhibition of 12-lipoxygenase (12-LOX), 15-lipoxygenase (15-LOX), or cyclooxygenase (COX) products. In the rat air pouch model, oral dosing of CJ-13,610 and zileuton resulted in selective inhibition 5-LOX activity from pouch exudate and ex vivo rat whole blood with similar potency to in vitro assay. These data show that the rat air pouch model is a reliable and useful tool for evaluating in vivo efficacy of 5-LOX inhibitors and may aid in the development of the next generation of 5-LOX inhibitors, such as the non-redox inhibitors similar to CJ-13,610.