Cutaneous neurogenic inflammation (CNI) is inflammation that is induced (or enhanced) in the skin by the release of neuropeptides from sensory nerve endings. Clinical manifestations are mainly sensory and vascular disorders such as pruritus and erythema. Transient receptor potential vanilloid 1 and ankyrin 1 (TRPV1 and TRPA1, respectively) are non-selective cation channels known to specifically participate in pain and CNI. Both TRPV1 and TRPA1 are co-expressed in a large subset of sensory nerves, where they integrate numerous noxious stimuli. It is now clear that the expression of both channels also extends far beyond the sensory nerves in the skin, occuring also in keratinocytes, mast cells, dendritic cells, and endothelial cells. In these non-neuronal cells, TRPV1 and TRPA1 also act as nociceptive sensors and potentiate the inflammatory process. This review discusses the role of TRPV1 and TRPA1 in the modulation of inflammatory genes that leads to or maintains CNI in sensory neurons and non-neuronal skin cells. In addition, this review provides a summary of current research on the intracellular sensitization pathways of both TRP channels by other endogenous inflammatory mediators that promote the self-maintenance of CNI.

Human CYP450 v-hydroxylases of the CYP4 family are known to convert arachidonic acid (AA) to its metabolite . This study deals with hydroxylations of four PUFAs, eicosatrienoic acid (ETA), AA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) by either human recombinant CYP4s enzymes or human liver microsomal preparations. CYP4F3A and CYP4F3B were the most efficient v-hydroxylases of these PUFAs. Moreover, the differences in the number of unsaturations of ETA, AA, and EPA allowed us to demonstrate a rise in the metabolic rate of hydroxylation when the double bond in 14-15 or 17-18 was missing. With the CYP4F enzymes, the main pathway was always the v-hydroxylation of PUFAs, whereas it was the (v-1)-hydroxylation with CYP1A1, CYP2C19, and CYP2E1. Finally, we demonstrated that the v9 and v3 PUFAs (ETA, EPA, and DHA) could all be used as alternative substrates in AA metabolism by human CYP4F2 and -4F3B. Thus, they decreased the ability of these enzymes to convert AA to 20-HETE. However, although ETA was the most hydroxylated substrate, EPA and DHA were the most potent inhibitors of the conversion of AA to 20-HETE. These findings suggest that some physiological effects of v3 FAs could partly result from a shift in the generation of active hydroxylated metabolites of AA through a CYP-mediated catalysis.-Fer, M., L. Corcos, Y. Dréano, E. Plée-Gautier, J-P. Salaün, F. Berthou, and Y. Amet. Cytochromes P450 from family 4 are the main omega hydroxylating enzymes in humans: CYP4F3B is the prominent player in PUFA metabolism. J. Lipid Res. 2008Res. . 49: 2379Res. -2389

Cutaneous neurogenic inflammation (CNI) is frequently associated with skin disorders. CNI is not limited to the retrograde signalling of nociceptive sensory nerve endings but can instead be regarded as a multicellular phenomenon. Thus, soluble mediators participating in communication among sensory nerves, skin and immune cells are key components of CNI. These interactions induce the self-maintenance of CNI, promoting a vicious cycle. Certain G protein-coupled receptors (GPCRs) play a prominent role in these cell interactions and contribute to selfmaintenance. Protease-activated receptors 2 and 4 (PAR-2 and PAR-4, respectively) and Mas-related G protein-coupled receptors (Mrgprs) are implicated in the synthesis and release of neuropeptides, proteases and soluble mediators from most cutaneous cells. Regulation of the expression and release of these mediators contributes to the vicious cycle of CNI. The authors propose certain hypothetical therapeutic options to interrupt this cycle, which might reduce skin symptoms and improve patient quality of life.

CYP4F isoforms are involved in the oxidation of important cellular mediators such as leukotriene B 4 (LTB4) and prostaglandins. The proinflammatory agent LTB4 and cytotoxic leukotoxins have been associated with several inflammatory diseases. We present evidence that the hydroxylation of Z 9(10)-epoxyoctadecanoic, Z 9(10)-epoxyoctadec-Z 12-enoic, and Z 12(13)-epoxyoctadec-Z 9-enoic acids and that of monoepoxides from arachidonic acid [epoxyeicosatrienoic acid (EET)] is important in the regulation of leukotoxin and EET activity. These three epoxidized derivatives from the C18 family (C18-epoxides) were converted to 18-hydroxy-C18-epoxides by human hepatic microsomes with apparent K m values of between 27.6 and 175 M. Among recombinant P450 enzymes, CYP4F2 and CYP4F3B catalyzed mainly the -hydroxylation of C18-epoxides with an apparent V max of between 0.84 and 15.0 min ؊ 1 , whereas the apparent V max displayed by CYP4F3A, the isoform found in leukocytes, ranged from 3.0 to 21.2 min ؊ 1 . The rate of -hydroxylation by CYP4A11 was experimentally found to be between 0.3 and 2.7 min ؊ 1 . CYP4F2 and CYP4F3 exhibited preferences for -hydroxylation of Z 8(9)-EET, whereas human liver microsomes preferred Z 11(12)-EET and, to a lesser extent, Z 8(9)-EET. Moreover, vicinal diol from both C18-epoxides and EETs were -hydroxylated by liver microsomes and by CYP4F2 and CYP4F3. These data support the hypothesis that the human CYP4F subfamily is involved in the -hydroxylation of fatty acid epoxides. These findings demonstrate that another pathway besides conversion to vicinal diol or chain shortening by ␤ -oxidation exists for fatty acid epoxide inactivation. -Le Quéré, V., E. Plée-Gautier, P. Potin, S. Madec, and J-P. Salaün. Human CYP4F3s are the main catalysts in the oxidation of fatty acid epoxides.

Hormone-sensitive lipase (HSL) catalyses the rate-limiting step in adipocyte lipolysis. Short-term hormonal regulation of HSL activity is well characterized, whereas little is known about the control of HSL gene expression. We have measured HSL mRNA content of 3T3-F442A and BFC-1 adipocytes in response to the cAMP analogue 8-(4-chlorophenylthio)-cAMP (8-CPT-cAMP) and to the phorbol ester phorbol 12-myristate 13-acetate (PMA) by Northern blot, using a specific mouse cDNA fragment. Treatment of the cells for 12 or 6 h with, respectively, 0.5 mM 8-CPT-cAMP or 1 microM PMA produced a maximal decrease of about 60% in HSL mRNA. These effects were unaffected by the protein-synthesis inhibitor anisomycin, suggesting that cAMP and PMA actions were direct. The reduction in HSL mRNA was accompanied by a reduction in HSL total activity. The intracellular routes that cAMP and PMA follow for inducing such an effect seemed clearly independent. (i) After desensitization of the protein kinase C regulation pathway by a 24 h treatment of the cells with 1 microM PMA, PMA action was abolished whereas cAMP was still fully active. (ii) Treatment with saturating concentrations of both agents produced an additive effect. (iii) The synthetic glucocorticoid dexamethasone had no proper effect on HSL gene expression but potentiated cAMP action without affecting PMA action. cAMP inhibitory action on HSL is unexpected. Indeed, the second messenger of catecholamines is the main activator of HSL by phosphorylation. We envision that a long-term cAMP treatment of adipocytes induces a counter-regulatory process that reduces HSL content and, ultimately, limits fatty acid depletion from stored triacylglycerols.

Skin-derived precursor cells (SKPs) are neural crest stem cells that persist in certain adult tissues, particularly in the skin. They can generate a large type of cell in vitro, including neurons. SKPs were induced to differentiate into sensory neurons (SNs) by molecules that were previously shown to be important for the generation of SNs: purmorphamine, CHIR99021, BMP4, GDNF, BDNF, and NGF. We showed that the differentiation of SKPs induced the upregulation of neurogenins. At the end of the differentiation protocol, transcriptional analysis was performed on BRN3A and a marker of pain-sensing nerve cell PRDM12 genes: 1000 times higher for PRDM12 and 2500 times higher for BRN3A in differentiated cells than they were in undifferentiated SKPs. Using immunostaining, we showed that 65% and 80% of cells expressed peripheral neuron markers BRN3A and PERIPHERIN, respectively. Furthermore, differentiated cells expressed TRPV1, PAR2, TRPA1, substance P, CGRP, HR1. Using calcium imaging, we observed that a proportion of cells responded to histamine, SLIGKV (a specific agonist of PAR2), polygodial (a specific agonist of TRPA1), and capsaicin (a specific agonist of TRPV1). In conclusion, SKPs are able to differentiate directly into functional SNs. These differentiated cells will be very useful for further in vitro studies.

Cytochrome P450 4F3 (CYP4F3), originally identified as one of the leukotriene B4 ω-hydroxylases, belongs to a CYP gene family that comprises several members, which participate in the metabolism of various endobiotics, as well as some xenobiotics. The CYP4F gene family is clustered in a 0.5-Mb stretch of genomic DNA on the p13 region of chromosome 19. Apart from the ω-hydroxylation of leukotriene B4 and prostaglandins, CYP4F3 is the main catalyst in the oxidation of fatty acid epoxides. CYP4F3 expression results from the synthesis of two distinct enzymes, CYP4F3A and CYP4F3B, which originate from the alternative splicing of a single pre-mRNA precursor molecule. Remarkably, the selection of either isoform is part of a tissue-specific control through which CYP3F3A is mostly expressed in leukocytes and CYP4F3B mostly in the liver. Recently, CYP4F3 single nucleotide polymorphisms have been incriminated in the onset of pathologies, including celiac or Crohn's diseases. Although much has been discovered in the regulation and function of CYP4F2, the closest CYP4F subfamily member, analyses of CYP4F3 enzymes lag somewhat behind in the field of our knowledge. In this short review, emphasis will be placed on the regulation and the functional roles of human CYP4F3.

The regulation of the human liver-specific cytochrome P450 4F3B (CYP4F3B) isoform, a splice variant of the CYP4F3 gene with strong substrate specificity for long chain fatty acids, is yet an unsolved question. This report provides the first evidence that CYP4F3B is uniquely induced by prostaglandin A 1 (PGA 1 ) in human hepatocyte-like