Cytochrome P450-mediated drug metabolizing activity in the nasal mucosa

Abstract

Pre-systemic elimination by local enzymatic degradation can play a key role in limiting the bioavailability of intranasally administered drugs. Despite remarkable advancement in the characterization of the nasal biotransformative enzymes, knowledge of the role of the nasal mucosa in limiting bioavailability of therapeutic agents is still inadequate. The aim of this work was to evaluate the expression and substrate biotransformation activity of cytochrome P450 enzymes in the nasal mucosa using bovine olfactory and respiratory explants as in vitro models. Gene expression and localization of major CYP450 isoforms in the nasal mucosa were examined using RT-PCR and immunohistochemistry. The bovine nasal mucosa showed abundant expression of CYP2A6 and 3A4 genes whereas 1A1, 1A2, 2C9, and 2C19 isoforms were expressed at much lower levels. The CYP450 proteins were observed to be present in the epithelial layer and in submucosal glandular cells. The diffusion of melatonin, a CYP1A2 substrate, and the appearance of 6-hydroxymelatonin, its primary metabolite, across bovine olfactory and respiratory explants was measured, and nasal olfactory and respiratory microsomal preparations were used to quantify the kinetic parameters for melatonin 6-hydroxylation. Results indicated that bovine olfactory and respiratory CYP450 isoforms were metabolically active towards melatonin metabolism, and the respiratory mucosa demonstrated the greatest melatonin 6-hydroxylation activity. Numerical simulations were used to probe the effects of the relative magnitudes of the permeability coefficient and enzymatic parameters on net substrate mass transfer across nasal mucosal tissues. The simulations indicated that the concentration gradient of This work could not have been completed without the love and support from my family and friends. I would like to thank my mom, dad, and brother for their unconditional love and encouragement. Also, sincere thanks to Bhakti and all my friends in Iowa City for making the graduate study an awesome experience. Finally, I would like to thank Girish for making this journey a memorable one! v ABSTRACT Pre-systemic elimination by local enzymatic degradation can play a key role in limiting the bioavailability of intranasally administered drugs. Despite remarkable advancement in the characterization of the nasal biotransformative enzymes, knowledge of the role of the nasal mucosa in limiting bioavailability of therapeutic agents is still inadequate. The aim of this work was to evaluate the expression and substrate biotransformation activity of cytochrome P450 enzymes in the nasal mucosa using bovine olfactory and respiratory explants as in vitro models. Gene expression and localization of major CYP450 isoforms in the nasal mucosa were examined using RT-PCR and immunohistochemistry. The bovine nasal mucosa showed abundant expression of CYP2A6 and 3A4 genes whereas 1A1, 1A2, 2C9, and 2C19 isoforms were expressed at much lower levels. The CYP450 proteins were observed to be present in the epithelial layer and in submuco...

Nose-to-Brain (N2B) Delivery: An Alternative Route for the Delivery of Biologics in the Management and Treatment of Central Nervous System Disorders

“…It is slightly acidic (pH 5.5–6.5), required for optimal ciliary clearance, and has limited buffering capacity [ 73 ]. The nasal mucus plays an important role in mediating immune responses to allergens and infectious particles by trapping them as they enter the respiratory passage [ 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 ]. MCC is the self-cleaning mechanism of the airways and a protective process for the lungs in removing inhaled particles, including pathogens.…”