CYP2J SUBFAMILY P450S IN THE LUNG - EXPRESSION, LOCALIZATION, AND POTENTIAL FUNCTIONAL-SIGNIFICANCE

Cytochrome P450 (P450) monooxygenases catalyze the epoxidation of arac hidonic acid to form epoxyeicosatrienoic acids, which modulate bronchi al smooth muscle tone and airway transepithelial ion transport. We rec ently described a new human P450 arachidonic acid epoxygenase (CYP2J2) and the corresponding rat homologue (CYP2J3). Northern analysis of lu ng RNA using CYP2J cDNA probes demonstrated that CYP2J2 and CYP2J3 mRN As were expressed in the lung. Immunoblotting of microsomal fractions prepared from human and rat lungs using a polyclonal antibody raised a gainst recombinant human CYP2J2 revealed a single 56-kDa band confirmi ng abundant pulmonary CYP2J2 and CYP2J3 protein expres sion. Immunohis tochemical analysis of formalin-fixed paraffin-embedded human and rat lung sections using the anti-human CYP2J2 IgG and avidin/biotin/peroxi dase detection showed that CYP2J proteins were primarily expressed in ciliated epithelial cells lining the airway. Prominent staining was al so noted in nonciliated airway epithelial cells, bronchial and pulmona ry vascular smooth muscle cells, pulmonary vascular endothelium, and a lveolar macrophages, whereas less intense staining was noted in alveol ar epithelial cells. Endogenous epoxyeicosatrienoic acids were detecte d in both human and rat lung using gas chromatography/mass spectrometr y, thus providing direct evidence for the in vivo human and rat pulmon ary P450 metabolism of arachidonic acid. Based on these data, we concl ude that CYP2J2 and CYP2J3 are abundant pulmonary arachidonic acid epo xygenases and that CYP2J products, the epoxyeicosatrienoic acids, are endogenous constituents of human and rat lung. In addition to known ef fects on airway smooth muscle tone and transepithelial electrolyte tra nsport, the localization of CYP2J proteins to vascular smooth muscle a nd endothelium suggests that epoxyeicosatrienoic acids may also be inv olved in the modulation of pulmonary vascular tone.