Brash AR

References (6)

Title : Lipidomic and transcriptional analysis of the linoleoyl-omega-hydroxyceramide biosynthetic pathway in human psoriatic lesions - Tyrrell_2021_J.Lipid.Res_62_100094
Author(s) : Tyrrell VJ , Ali F , Boeglin WE , Andrews R , Burston J , Birchall JC , Ingram JR , Murphy RC , Piguet V , Brash AR , O'Donnell VB , Thomas CP
Ref : J Lipid Res , 62 :100094 , 2021
Abstract : A complex assembly of lipids including fatty acids, cholesterol, and ceramides is vital to the integrity of the mammalian epidermal barrier. The formation of this barrier requires oxidation of the substrate fatty acid, linoleic acid (LA), which is initiated by the enzyme 12R-lipoxygenase (LOX). In the epidermis, unoxidized LA is primarily found in long-chain acylceramides termed esterified omega-hydroxy sphingosine (EOS)/phytosphingosine/hydroxysphingosine (collectively EOx). The precise structure and localization of LOX-oxidized EOx in the human epidermis is unknown, as is their regulation in diseases such as psoriasis, one of the most common inflammatory diseases affecting the skin. Here, using precursor LC/MS/MS, we characterized multiple intermediates of EOx, including 9-HODE, 9,10-epoxy-13-HOME, and 9,10,13-TriHOME, in healthy human epidermis likely to be formed via the epidermal LOX pathways. The top layers of the skin contained more LA, 9-HODE, and 9,10,13-TriHOME EOSs, whereas 9,10-epoxy-13-HOME EOS was more prevalent deeper in the stratum corneum. In psoriatic lesions, levels of native EOx and free HODEs and HOMEs were significantly elevated, whereas oxidized species were generally reduced. A transcriptional network analysis of human psoriatic lesions identified significantly elevated expression of the entire biosynthetic/metabolic pathway for oxygenated ceramides, suggesting a regulatory function for EOx lipids in reconstituting epidermal integrity. The role of these new lipids in progression or resolution of psoriasis is currently unknown. We also discovered the central coordinated role of the zinc finger protein transcription factor, ZIC1, in driving the phenotype of this disease. In summary, long-chain oxygenated ceramide metabolism is dysregulated at the lipidomic level in psoriasis, likely driven by the transcriptional differences also observed, and we identified ZIC1 as a potential regulatory target for future therapeutic interventions.
ESTHER : Tyrrell_2021_J.Lipid.Res_62_100094
PubMedSearch : Tyrrell_2021_J.Lipid.Res_62_100094
PubMedID: 34171322

Title : Epoxide hydrolase 3 (Ephx3) gene disruption reduces ceramide linoleate epoxide hydrolysis and impairs skin barrier function - Edin_2021_J.Biol.Chem_296_100198
Author(s) : Edin ML , Yamanashi H , Boeglin WE , Graves JP , DeGraff LM , Lih FB , Zeldin DC , Brash AR
Ref : Journal of Biological Chemistry , 296 :100198 , 2021
Abstract : The mammalian epoxide hydrolase (EPHX)3 is known from in vitro experiments to efficiently hydrolyze the linoleate epoxides 9,10-epoxyoctadecamonoenoic acid (EpOME) and epoxyalcohol 9R,10R-trans-epoxy-11E-13R-hydroxy-octadecenoate to corresponding diols and triols, respectively. Herein we examined the physiological relevance of EPHX3 to hydrolysis of both substrates in vivo. Ephx3(-)(/)(-) mice show no deficiency in EpOME-derived plasma diols, discounting a role for EPHX3 in their formation, whereas epoxyalcohol-derived triols esterified in acylceramides of the epidermal 12R-lipoxygenase pathway are reduced. Although the Ephx3(-)(/)(-) pups appear normal, measurements of transepidermal water loss detected a modest and statistically significant increase compared with the wild-type or heterozygote mice, reflecting a skin barrier impairment that was not evident in the knockouts of mouse microsomal (EPHX1/microsomal epoxide hydrolase) or soluble (EPHX2/sEH). This barrier phenotype in the Ephx3(-)(/)(-) pups was associated with a significant decrease in the covalently bound ceramides in the epidermis (40% reduction, p < 0.05), indicating a corresponding structural impairment in the integrity of the water barrier. Quantitative LC-MS analysis of the esterified linoleate-derived triols in the murine epidermis revealed a marked and isomer-specific reduction (-85%) in the Ephx3(-)(/)(-) epidermis of the major trihydroxy isomer 9R,10S,13R-trihydroxy-11E-octadecenoate. We conclude that EPHX3 (and not EPHX1 or EPHX2) catalyzes hydrolysis of the 12R-LOX/eLOX3-derived epoxyalcohol esterified in acylceramide and may function to control flux through the alternative and crucial route of metabolism via the dehydrogenation pathway of SDR9C7. Importantly, our findings also identify a functional role for EPHX3 in transformation of a naturally esterified epoxide substrate, pointing to its potential contribution in other tissues.
ESTHER : Edin_2021_J.Biol.Chem_296_100198
PubMedSearch : Edin_2021_J.Biol.Chem_296_100198
PubMedID: 33334892
Gene_locus related to this paper: human-EPHX3 , mouse-ephx3

Title : Catalytic activities of mammalian epoxide hydrolases with cis and trans fatty acid epoxides relevant to skin barrier function - Yamanashi_2018_J.Lipid.Res_59_684
Author(s) : Yamanashi H , Boeglin WE , Morisseau C , Davis RW , Sulikowski GA , Hammock BD , Brash AR
Ref : J Lipid Res , 59 :684 , 2018
Abstract : Lipoxygenase (LOX)-catalyzed oxidation of the essential fatty acid, linoleate, represents a vital step in construction of the mammalian epidermal permeability barrier. Analysis of epidermal lipids indicates that linoleate is converted to a trihydroxy derivative by hydrolysis of an epoxy-hydroxy precursor. We evaluated different epoxide hydrolase (EH) enzymes in the hydrolysis of skin-relevant fatty acid epoxides and compared the products to those of acid-catalyzed hydrolysis. In the absence of enzyme, exposure to pH 5 or pH 6 at 37 degreesC for 30 min hydrolyzed fatty acid allylic epoxyalcohols to four trihydroxy products. By contrast, human soluble EH [sEH (EPHX2)] and human or murine epoxide hydrolase-3 [EH3 (EPHX3)] hydrolyzed cis or trans allylic epoxides to single diastereomers, identical to the major isomers detected in epidermis. Microsomal EH [mEH (EPHX1)] was inactive with these substrates. At low substrate concentrations (<10 microM), EPHX2 hydrolyzed 14,15-epoxyeicosatrienoic acid (EET) at twice the rate of the epidermal epoxyalcohol, 9R,10R-trans-epoxy-11E-13R-hydroxy-octadecenoic acid, whereas human or murine EPHX3 hydrolyzed the allylic epoxyalcohol at 31-fold and 39-fold higher rates, respectively. These data implicate the activities of EPHX2 and EPHX3 in production of the linoleate triols detected as end products of the 12R-LOX pathway in the epidermis and implicate their functioning in formation of the mammalian water permeability barrier.
ESTHER : Yamanashi_2018_J.Lipid.Res_59_684
PubMedSearch : Yamanashi_2018_J.Lipid.Res_59_684
PubMedID: 29459481

Title : PNPLA1 has a crucial role in skin barrier function by directing acylceramide biosynthesis - Hirabayashi_2017_Nat.Commun_8_14609
Author(s) : Hirabayashi T , Anjo T , Kaneko A , Senoo Y , Shibata A , Takama H , Yokoyama K , Nishito Y , Ono T , Taya C , Muramatsu K , Fukami K , Munoz-Garcia A , Brash AR , Ikeda K , Arita M , Akiyama M , Murakami M
Ref : Nat Commun , 8 :14609 , 2017
Abstract : Mutations in patatin-like phospholipase domain-containing 1 (PNPLA1) cause autosomal recessive congenital ichthyosis, but the mechanism involved remains unclear. Here we show that PNPLA1, an enzyme expressed in differentiated keratinocytes, plays a crucial role in the biosynthesis of omega-O-acylceramide, a lipid component essential for skin barrier. Global or keratinocyte-specific Pnpla1-deficient neonates die due to epidermal permeability barrier defects with severe transepidermal water loss, decreased intercellular lipid lamellae in the stratum corneum, and aberrant keratinocyte differentiation. In Pnpla1(-/-) epidermis, unique linoleate-containing lipids including acylceramides, acylglucosylceramides and (O-acyl)-omega-hydroxy fatty acids are almost absent with reciprocal increases in their putative precursors, indicating that PNPLA1 catalyses the omega-O-esterification with linoleic acid to form acylceramides. Moreover, acylceramide supplementation partially rescues the altered differentiation of Pnpla1(-/-) keratinocytes. Our findings provide valuable insight into the skin barrier formation and ichthyosis development, and may contribute to novel therapeutic strategies for treatment of epidermal barrier defects.
ESTHER : Hirabayashi_2017_Nat.Commun_8_14609
PubMedSearch : Hirabayashi_2017_Nat.Commun_8_14609
PubMedID: 28248300

Title : The Precise Structures and Stereochemistry of Trihydroxy-linoleates Esterified in Human and Porcine Epidermis and Their Significance in Skin Barrier Function: implication of an epoxide hydrolase in the transformation of linoleate - Chiba_2016_J.Biol.Chem_291_14540
Author(s) : Chiba T , Thomas CP , Calcutt MW , Boeglin WE , O'Donnell VB , Brash AR
Ref : Journal of Biological Chemistry , 291 :14540 , 2016
Abstract : Creation of an intact skin water barrier, a prerequisite for life on dry land, requires the lipoxygenase-catalyzed oxidation of the essential fatty acid linoleate, which is esterified to the omega-hydroxyl of an epidermis-specific ceramide. Oxidation of the linoleate moiety by lipoxygenases is proposed to facilitate enzymatic cleavage of the ester bond, releasing free omega-hydroxyceramide for covalent binding to protein, thus forming the corneocyte lipid envelope, a key component of the epidermal barrier. Herein, we report the transformations of esterified linoleate proceed beyond the initial steps of oxidation and epoxyalcohol synthesis catalyzed by the consecutive actions of 12R-LOX and epidermal LOX3. The major end product in human and porcine epidermis is a trihydroxy derivative, formed with a specificity that implicates participation of an epoxide hydrolase in converting epoxyalcohol to triol. Of the 16 possible triols arising from hydrolysis of 9,10-epoxy-13-hydroxy-octadecenoates, using LC-MS and chiral analyses, we identify and quantify specifically 9R,10S,13R-trihydroxy-11E-octadecenoate as the single major triol esterified in porcine epidermis and the same isomer with lesser amounts of its 10R diastereomer in human epidermis. The 9R,10S,13R-triol is formed by SN2 hydrolysis of the 9R,10R-epoxy-13R-hydroxy-octadecenoate product of the LOX enzymes, a reaction specificity characteristic of epoxide hydrolase. The high polarity of triol over the primary linoleate products enhances the concept that the oxidations disrupt corneocyte membrane lipids, promoting release of free omega-hydroxyceramide for covalent binding to protein and sealing of the waterproof barrier.
ESTHER : Chiba_2016_J.Biol.Chem_291_14540
PubMedSearch : Chiba_2016_J.Biol.Chem_291_14540
PubMedID: 27151221
Gene_locus related to this paper: human-EPHX3

Title : Mutations associated with a congenital form of ichthyosis (NCIE) inactivate the epidermal lipoxygenases 12R-LOX and eLOX3 - Yu_2005_Biochim.Biophys.Acta_1686_238
Author(s) : Yu Z , Schneider C , Boeglin WE , Brash AR
Ref : Biochimica & Biophysica Acta , 1686 :238 , 2005
Abstract : Non-bullous congenital ichthyosiform erythroderma (NCIE) is one of the main clinical forms of ichthyosis. Genetic studies indicated that 12R-lipoxygenase (12R-LOX) or epidermal lipoxygenase-3 (eLOX3) was mutated in six families affected by NCIE [F. Jobard, C. Lefevre, A. Karaduman, C. Blanchet-Bardon, S. Emre, J. Weissenbach, M. Ozguc, M. Lathrop, J.F. Prud'homme, J. Fischer, Lipoxygenase-3 (ALOXE3) and 12(R)-lipoxygenase (ALOX12B) are mutated in non-bullous congenital ichthyosiform erythroderma (NCIE) linked to chromosome 17p13.1, Hum. Mol. Genet. 11 (2002) 107-113.], but the impact of these mutations on LOX function has not been defined. To explore this, we overexpressed the wild-type or mutated enzymes in E. coli and COS7 cells and then analyzed the essential catalytic properties. We showed recently that human eLOX3 is a hydroperoxide isomerase (hepoxilin synthase) that converts the product of 12R-LOX, 12R-hydroperoxyeicosatetraenoic acid (12R-HPETE) to a specific epoxyalcohol. Using incubations with [(14)C]-labeled substrates and HPLC analyses, we found that the naturally occurring mutations totally eliminate the lipoxygenase activity of 12R-LOX and the hydroperoxide isomerase activity of eLOX3. We further demonstrate that the 12R-LOX/eLOX3-derived 8R-hydroxy-11R,12R-epoxide is converted by an epoxide hydrolase in COS7 cells and in human keratinocytes to a single isomer of 8,11,12-trihydroxyeicosa-5,9,14-trienoic acid. Taken together, the results support the hypothesis that 12R-LOX, eLOX3, and perhaps an epoxide hydrolase function together in the normal process of skin differentiation, and that the loss of function mutations are the basis of the LOX-dependent form of NCIE.
ESTHER : Yu_2005_Biochim.Biophys.Acta_1686_238
PubMedSearch : Yu_2005_Biochim.Biophys.Acta_1686_238
PubMedID: 15629692