Zileuton nanocrystals alter intestinal phase I/II metabolic enzymes and epithelial permeability in a sex-dependent manner

The bioavailability of a drug is influenced by its physicochemical properties, dissolution rate, solubility, gastrointestinal tract permeability, and its absorption, distribution, and metabolism. Zileuton, a poorly soluble biopharmaceutical classification system class II drug prescribed for the treatment of asthma, was selected as a candidate for nanocrystal drug formulation. Our previous study demonstrated that zileuton nanocrystal formulation (NfZ) efficiently suppressed proinflammatory cytokines associated with asthma pathogenesis. Hence, this study aims to evaluate whether sex-dependent differences in the expression of genes related to drug metabolism and intestinal permeability influence the activity of the nanocrystal-formulated drug. In this study, we used the same animal samples as those reported in our earlier publications. To the best of our knowledge, this is the first study to conduct a comparative analysis of the effects of pure active pharmaceutical ingredient (API) and its nanocrystal formulation on metabolic enzyme genes and intestinal permeability-related genes. Our results demonstrated a significant increase in several genes involved in the metabolism of API, physical mixture (PM), and NfZ in males compared with females. PM and NfZ-treated animals showed increased expression of metabolic enzyme-related genes (phase I and phase II) and reduced alanine aminotransaminase activity at an equivalent dose compared with API-treated animals. However, genes related to oxidative metabolism and detoxification pathways were highly expressed in PM-treated animals; comparatively, NfZ treatment showed modest induction. Genes related to intestinal permeability were most significantly altered in API-treated animals compared to those dosed with NfZ. SIGNIFICANCE STATEMENT: The significance of this study is the sex-dependent difference in the expression of phase I and phase II metabolic enzymes and intestinal permeability-related genes upon treatment with different formulations of zileuton. Approximately 5% of asthmatic patients develop hepatocytotoxicity due to zileuton treatment and show several fold elevated levels of ALT in plasma. In the present study, differences in the decrease of ALT levels between the formulations highlight the advantages of the nanocrystal formulation.