Comparison of pulmonary/nasal CYP2F expression levels in rodents and rhesus macaque

Naphthalene is a ubiquitous environmental contaminant that results in dose-dependent and tissue-, species-, and cell-selective necrosis of murine Clara cells upon exposure. Naphthalene is metabolized by CYP2F to a 1,2-epoxide, the first and obligate step in events leading to cytotoxicity. The studies reported here examine the relationship between levels of transcript (mRNA) and CYP2F protein in the respiratory tract of rodents with tissue susceptibility to injury. In both mice and rats, the lung contains more CYP2F transcript than liver; levels in kidney were undetectable. Mice expressed 4- and 8-fold greater CYP2F transcript in lung and liver tissue, respectively, than rats. Quantitative immunoblot blot analysis of CYP2F in airway subcompartments revealed mice to have 30- (minor daughters/terminal bronchioles), 20- (major daughter), 40- (trachea), and 6- (parenchyma) fold higher levels of CYP2F protein than rats. Within the lungs of both rodent species, the highest CYP2F expression was found in the distal airways. The kidney contained undetectable amounts of CYP2F; multiple immunoreactive bands in liver precluded quantification. The olfactory epithelium contains the greatest amount of cytochrome P450 protein of all tissues studied in the rat, consistent with the observed pattern of in vivo injury. Overall, these studies in rodents demonstrate a strong association between CYP2F expression levels and susceptibility to naphthalene-induced cytotoxicity. Of all primate tissues studied, only the nasal ethmoturbinates contain quantifiable amounts of CYP2F, roughly 10- and 20-fold less than the corresponding tissues in rats and mice, respectively. These results suggest that rhesus macaques may be refractory to naphthalene-induced pulmonary injury.