Differentiation-Specific Factors Modulate Epidermal CYP1–4 Gene Expression in Human Skin in Response to Retinoic Acid and Classic Aryl Hydrocarbon Receptor Ligands

Abstract

Human epidermal keratinocytes express subsets of cytochromes P450 (P450) (CYP gene products) that are strongly up-regulated, not regulated, or down-regulated by differentiation-specific factors. We investigated how drug exposure affects epidermal expression of CYP1-4 genes, which encode many drug-metabolizing P450s. Real-time polymerase chain reaction (PCR) assays measured CYP1-4 mRNA levels in epidermal keratinocytes differentiated in vitro in the presence of drug or vehicle for 6 days. We confirmed the spinous phenotype at day 6 by changes in cellular morphology and upregulation of cytokeratin 10 and transglutaminase (TGM)1 mRNA in the differentiating keratinocytes. Effects of drug exposure depended on the influence of differentiation-specific factors in controlling epidermal CYP1-4 expression. CYP2C18, 2C19, 2C9, 2W1, 3A4, and 4B1 are up-regulated by cellular differentiation; mRNA levels for these CYP genes were inhibited in differentiating keratinocytes exposed to retinoic acid and aryl hydrocarbon receptor (AhR) ligands. These same drugs effected Յ2-fold change or even augmented mRNA levels for CYP genes that are not regulated by differentiation (CYP2S1, 2J2, 1B1, 1A1, 1A2, 2E1, and 2D6) and for CYP2U1, which is expressed at highest levels in undifferentiated keratinocytes. The clinically relevant drugs miconazole, dexamethasone, rifampicin, and dapsone had little effect on CYP1-4 mRNA levels under assay conditions. The AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin also up-regulated keratinocyte TGM1 mRNA in a concentration-and time-dependent manner. This effect was blocked by the AhR antagonist resveratrol. These findings implicate AhR-dependent up-regulation of TGM1 mRNA in differentiating keratinocytes as one mechanism contributing toward chloracne in humans exposed to toxic levels of dioxin.Structural and biochemical features of skin are specialized toward its major protective functions as a barrier to the host environment. In addition to regulating water loss and body temperature, skin has mechanisms for self-renewal and for surveillance and repair of cell damage due to biological, physical, and chemical exposures. Epidermal keratinocytes constitute the major reservoir of cutaneous cytochromes P450 enzymes (CYP gene products) involved in oxidative metabolism and disposition of endogenous and foreign compounds, including environmental toxins, natural products, and drugs. Most drug-metabolizing cytochromes P450 are members of the CYP1-4 gene families, which number 35 (61%) of the 57 putatively functional CYP genes in humans (Nelson et al., 2004).Major detoxifying organs such as the liver rank among tissues containing the highest concentrations of cytochromes P450; much lower concentrations are found in peripheral tissues such as skin. Liver and skin express many of the same P450s, but an important difference is the most abundant hepatic P450s tend to be expressed at relatively low levels in cutaneous tissues and vice versa (Du et al., 2006). This tissue-specificity suggests unique adaptation to ...

An environmental contaminant, benzo(a)pyrene, induces oxidative stress-mediated interleukin-8 production in human keratinocytes via the aryl hydrocarbon receptor signaling pathway

“…However, only a few studies have focused on the metabolism and biology of PAHs in NHEKs [18][19][20]. The present study demonstrated the nuclear translocation of AhR from cytoplasm after BaP [ ( ) T D $ F I G ] Fig.…”

“…*p < 0.05 compared to DMSO-treatment (control). ligand such as resveratrol and curcumin inhibit NF-kb activation although they induce translocation of AhR into nuclei [18,[43][44][45]. These findings suggest that further studies are required to elucidate the precise mechanism of RelB/AhR-mediated IL-8 production.…”

Expression and Induction of Cytochrome P450 Isoenzymes in Human Skin Equivalents

“…We showed in previous studies that characterization of the CYP expression pattern in the skin can be easily fulfilled in a semi-quantitative way by PCR or Western blot analysis or in a quantitative way by real-time PCR [13,21,22] . Many of the CYPs that have been characterized to play major roles in xenobiotic or drug metabolism in the liver have also been identified in human skin.…”

Cutaneous Metabolism in Transdermal Drug Delivery

“…In a later study, the real time PCR assays measured the CYP1-CYP4 mRNA levels in differentiating human epidermal keratino-cytes. Significant increases were found in CYP2C18 (113-fold), CYP2W1 (27-fold), and CYP4B1 (356-fold) by exposure to known CYP inducers and clinically relevant drug compounds [57].…”