Eicosapentaenoic Acid Influences the Lipid Profile of an In Vitro Psoriatic Skin Model Produced with T Cells

Psoriasis is a skin disease characterized by epidermal hyperplasia and an inappropriate activation of the adaptive immunity. A dysregulation of the skin's lipid mediators is reported in the disease with a predominance of the inflammatory cascade derived from n-6 polyunsaturated fatty acids (n-6 PUFAs). Bioactive lipid mediators derived from arachidonic acid (AA) are involved in the inflammatory functions of T cells in psoriasis, whereas n-3 PUFAs' derivatives are anti-inflammatory metabolites. Here, we sought to evaluate the influence of a supplementation of the culture media with eicosapentaenoic acid (EPA) on the lipid profile of a psoriatic skin model produced with polarized T cells. Healthy and psoriatic skin substitutes were produced following the auto-assembly technique. Psoriatic skin substitutes produced with or without T cells presented increased epidermal and dermal linolenic acid (LA) and AA levels. N-6 PUFA lipid mediators were strongly measured in psoriatic substitutes, namely, 13-hydroxyoctadecadienoic acid (13-HODE), prostaglandin E2 (PGE2) and 12-hydroxyeicosatetraenoic acid (12-HETE). The added EPA elevated the amounts of EPA, n-3 docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) in the epidermal and dermal phospholipids. The EPA supplementation balanced the production of epidermal lipid mediators, with an increase in prostaglandin E3 (PGE3), 12-hydroxyeicosapentaenoic acid (12-HEPE) and N-eicosapentaenoyl-ethanolamine (EPEA) levels. These findings show that EPA modulates the lipid composition of psoriatic skin substitutes by encouraging the return to a cutaneous homeostatic state.

Endocannabinoid hydrolysis inhibition unmasks that unsaturated fatty acids induce a robust synthesis of 2-arachidonoyl-glycerol and its congeners in human myeloid leukocytes

The endocannabinoid 2-arachidonoyl-gycerol (2-AG) modulates immune responses by activating cannabinoid receptors or through its multiple metabolites, notably eicosanoids. Thus, 2-AG hydrolysis inhibition might represent an interesting anti-inflammatory strategy that would simultaneously increase the levels of 2-AG and decrease those of eicosanoids. Accordingly, 2-AG hydrolysis inhibition increased 2-AG half-life in neutrophils. Under such setting, neutrophils, eosinophils and monocytes synthesized large amounts of 2-AG and other monoacylglycerols (MAGs) in response to arachidonic acid and other unsaturated fatty acids (UFAs). Arachidonic acid and UFAs were ~1000-fold more potent than GPCR agonists at stimulating MAG biosynthesis. Triascin C and thimerosal, which respectively inhibit fatty acyl-CoA synthases and acyl-CoA transferases, prevented the UFA-induced MAG synthesis, implying glycerolipid remodeling is essential in this process. 2-AG and other MAG biosynthesis was preceded by that of the corresponding lysophosphatidic acid (LPA). However, we could not directly implicate LPA dephosphorylation in MAG biosynthesis. While the GPCR agonists PAF, fMLP and LTB4 poorly or did not induced 2-AG biosynthesis, they inhibited that induced by AA by 25–50%, suggesting that 2-AG biosynthesis is decreased when leukocytes are surrounded by a pro-inflammatory entourage. Our data conclusively indicate that human leukocytes use AA and UFAs to biosynthesize biologically significant concentrations of 2-AG and other MAGs and that hijacking the immune system with 2-AG hydrolysis inhibitors might diminish inflammation in humans.

Human eosinophils and neutrophils biosynthesize novel 15-lipoxygenase metabolites from 1-linoleoyl-glycerol and N-linoleoyl-ethanolamine

BACKGROUND

The endocannabinoids 2-AG and AEA are lipids regulating many physiological processes, notably inflammation. The endocannabinoidome includes other monoacylglycerols (MAG) and N-acyl-ethanolamines (NAE) such as 1-linoleoyl-glycerol (1-LG) and N-linoleoyl-ethanolamine (LEA). Endocannabinoid hydrolysis inhibitors are now being tested as potential anti-inflammatory agents. By increasing MAG and/or NAE levels, these inhibitors will likely increase the levels of their metabolites. Herein we investigated whether 1-LG and LEA were substrates for the 15-lipoxygenase pathway, which is strongly involved in asthma and its severity. We thus assessed how human eosinophils and neutrophils biosynthesized the 15-lipoxygenase metabolites of 1-LG and LEA. Linoleic acid (LA), a well-documented substrate of 15-lipoxygenases, was used as positive control.

RESULTS

We synthesized the putative 15-lipoxygenase metabolites of 1-LG and LEA using Novozym435 and soybean lipoxygenase. Eosinophils, which express the 15-lipoxygenase-1, metabolized LA, 1-LG, and LEA into their 13-hydroxy derivatives. This was almost complete after 5 minutes. Substrate preference of eosinophils was LA>LEA>1-LG. Human neutrophils, which express the 15-lipoxygenase-2, also metabolized LA, 1-LG, and LEA into their 13-hydroxy derivatives. This was maximal after 30 seconds. Substrate preference was LA≫1-LG>LEA. Importantly, the new 15-lipoxygenase metabolites we disclose were found in tissues from humans and mice.

CONCLUSIONS

We successfully showed that human eosinophils and neutrophils transforms 1-LG and LEA into novel 15-lipoxygenase metabolites. How these new metabolites modulate the inflammatory cascade is now being explored.

Transcriptional landscape of the human and fly genomes: nonlinear and multifunctional modular model of transcriptomes

Regions of the genome not coding for proteins or not involved in cis-acting regulatory activities are frequently viewed as lacking in functional value. However, a number of recent large-scale studies have revealed significant regulated transcription of unannotated portions of a variety of plant and animal genomes, allowing a new appreciation of the widespread transcription of large portions of the genome. High-resolution mapping of the sites of transcription of the human and fly genomes has provided an alternative picture of the extent and organization of transcription and has offered insights for biological functions of some of the newly identified unannotated transcripts. Considerable portions of the unannotated transcription observed are developmental or cell-type-specific parts of protein-coding transcripts, often serving as novel, alternative 5' transcriptional start sites. These distal 5' portions are often situated at significant distances from the annotated gene and alternatively join with or ignore portions of other intervening genes to comprise novel unannotated protein-coding transcripts. These data support an interlaced model of the genome in which many regions serve multifunctional purposes and are highly modular in their utilization. This model illustrates the underappreciated organizational complexity of the genome and one of the functional roles of transcription from unannotated portions of the genome.