Evidence that cytochrome P450 CYP2B19 is the major source of epoxyeicosatrienoic acids in mouse skin.

CYP2B19 is an arachidonic acid monooxygenase highly expressed in the outer, differentiated cell layers of mouse epidermis. We aimed to establish whether CYP2B19 is the source of epidermal epoxyeicosatrienoic acids (EETs), which are implicated in mechanisms regulating epidermal cornification. We show that primary cultures of mouse epidermal keratinocytes expressed native CYP2B19, as determined by mass spectrometry. Differentiation upregulated CYP2B19 mRNA levels ( approximately 39-fold) detected by real-time PCR, CYP2B19 immunoreactivity detected by Western blotting, and cellular levels of the CYP2B19 product 11,12-EET. Cellular 11,12-EET formed from endogenous arachidonic acid increased preferentially (4- to 12-fold) at Day 4 or 5 of differentiation, compared with undifferentiated (Day 0) keratinocyte cultures. Temporally, these results concur with the maximal levels of CYP2B19 mRNA measured at Day 2 and CYP2B19 immunoreactivity at Day 4. We conclude that while mouse epidermis likely expresses multiple cytochrome P450 enzymes, existing evidence supports native CYP2B19 as being the major source of epidermal EET formation.