TY - JOUR
T1 - Nasal cytochrome P450 2A
T2 - Identification, regional localization, and metabolic activity toward hexamethylphosphoramide, a known nasal carcinogen
AU - Thornton-Manning, Janice R.
AU - Nikula, Kristen J.
AU - Hotchkiss, Jon A.
AU - Avila, Kelly J.
AU - Rohrbacher, Kevin D.
AU - Ding, Xinxin
AU - Dahl, Alan R.
N1 - Funding Information:
The authors acknowledge the excellent technical help of Heidi Harms. They also thank Dr. Fletcher Hahn for his careful review of the manuscript. The Inhalation Toxicology Research Institute is fully accredited by the American Association for Accreditation of Laboratory Animal Care. This work was supported by U.S. DOE/OHER under Contract DE-AC04-76EV01013 and NIH Grant ES 5910 (to A.R.D.) and ES 07462 (to X.D.) from the National Institute for Environmental Health Sciences.
PY - 1997/1
Y1 - 1997/1
N2 - Two members of the cytochrome P450 2A subfamily, CYP2A10 and 2A11, are abundant nasal enzymes previously characterized in rabbit olfactory microsomes. Rabbit CYP2A is active toward a number of nasal toxicants, including the rat nasal procarcinogen hexamethylphosphoramide (HMPA). While P450s immunochemically related to the rabbit CYP2As have been detected in rat and human nasal mucosa, confirmation of these enzymes as members of the CYP2A subfamily and efforts to characterize their ability to bioactivate toxicants have been limited. In the present study, the regional distribution and cell-specific expression of CYP2A in the rat nasal cavity were examined using an antibody to rabbit CYP2A10/11. In sections of the anterior nose, immunoreactive CYP2A was present in ciliated cells of the nasal respiratory epithelium and cuboidal epithelial cells of the nasal transitional epithelium, but was absent in squamous epithelial cells. The most intense immunostaining was observed in the posterior nose. Olfactory sustentacular cells and Bowman's gland cells in sections posterior to the nasal papilla stained most intensely. Western blot analysis revealed that anti-CYP2A10/11 recognized a sharp band of approximately 50 kDa in nasal respiratory and olfactory microsomes, supporting the premise that the antibody is reacting with a cytochrome P450 enzyme. The nasal expression of CYP2A6 mRNA - a member of the human CYP2A subfamily having a high degree of homology to rabbit 2A10 and 2A11 - was examined in human surgical patients. Middle turbinectomy tissues - largely composed of nasal respiratory epithelia - from 11 patients were analyzed for the presence of CYP2A6 using reverse transcription-polymerase chain reaction (RT-PCR). Identification of CYP2A6 was confirmed by DNA sequencing of RT-PCR products. CYP2A6 mRNA was detected in all of the human samples analyzed. In additional experiments, human CYP2A6 metabolized HMPA to formaldehyde, suggesting that this compound might cause nasal toxicity in humans. The identification of CYP2A cytochromes in rat and human nasal tissues may have important implications for risk assessment of inhaled xenobiotics.
AB - Two members of the cytochrome P450 2A subfamily, CYP2A10 and 2A11, are abundant nasal enzymes previously characterized in rabbit olfactory microsomes. Rabbit CYP2A is active toward a number of nasal toxicants, including the rat nasal procarcinogen hexamethylphosphoramide (HMPA). While P450s immunochemically related to the rabbit CYP2As have been detected in rat and human nasal mucosa, confirmation of these enzymes as members of the CYP2A subfamily and efforts to characterize their ability to bioactivate toxicants have been limited. In the present study, the regional distribution and cell-specific expression of CYP2A in the rat nasal cavity were examined using an antibody to rabbit CYP2A10/11. In sections of the anterior nose, immunoreactive CYP2A was present in ciliated cells of the nasal respiratory epithelium and cuboidal epithelial cells of the nasal transitional epithelium, but was absent in squamous epithelial cells. The most intense immunostaining was observed in the posterior nose. Olfactory sustentacular cells and Bowman's gland cells in sections posterior to the nasal papilla stained most intensely. Western blot analysis revealed that anti-CYP2A10/11 recognized a sharp band of approximately 50 kDa in nasal respiratory and olfactory microsomes, supporting the premise that the antibody is reacting with a cytochrome P450 enzyme. The nasal expression of CYP2A6 mRNA - a member of the human CYP2A subfamily having a high degree of homology to rabbit 2A10 and 2A11 - was examined in human surgical patients. Middle turbinectomy tissues - largely composed of nasal respiratory epithelia - from 11 patients were analyzed for the presence of CYP2A6 using reverse transcription-polymerase chain reaction (RT-PCR). Identification of CYP2A6 was confirmed by DNA sequencing of RT-PCR products. CYP2A6 mRNA was detected in all of the human samples analyzed. In additional experiments, human CYP2A6 metabolized HMPA to formaldehyde, suggesting that this compound might cause nasal toxicity in humans. The identification of CYP2A cytochromes in rat and human nasal tissues may have important implications for risk assessment of inhaled xenobiotics.
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U2 - 10.1006/taap.1996.7975
DO - 10.1006/taap.1996.7975
M3 - Article
C2 - 9007030
AN - SCOPUS:0031018163
SN - 0041-008X
VL - 142
SP - 22
EP - 30
JO - Toxicology and Applied Pharmacology
JF - Toxicology and Applied Pharmacology
IS - 1
ER -