Dietary supplementation with ethyl ester concentrates of fish oil (n-3) and borage oil (n-6) polyunsaturated fatty acids induces epidermal generation of local putative anti-inflammatory metabolites

Sustainable and Selective Extraction of Lipids and Bioactive Compounds from Microalgae

The procedures for the extraction and separation of lipids and nutraceutics from microalgae using classic solvents have been frequently used over the years. However, these production methods usually require expensive and toxic solvents. Based on our studies involving the use of eco-sustainable methodologies and alternative solvents, we selected ethanol (EtOH) and cyclopentyl methyl ether (CPME) for extracting bio-oil and lipids from algae. Different percentages of EtOH in CPME favor the production of an oil rich in saturated fatty acids (SFA), useful to biofuel production or rich in bioactive compounds. The proposed method for obtaining an extract rich in saturated or unsaturated fatty acids from dry algal biomass is disclosed as eco-friendly and allows a good extraction yield. The method is compared both in extracted oil percentage yield and in extracted fatty acids selectivity to extraction by supercritical carbon dioxide (SC-CO₂).

Impact of Reduced Dietary Levels of Eicosapentaenoic Acid and Docosahexaenoic Acid on the Composition of Skin Membrane Lipids in Atlantic Salmon ( Salmo salar L.)

Membrane lipids, including sphingolipids and glycerol-phospholipids, are essential in maintaining the skin's barrier function in mammals, but their composition in fish skin and their response to diets have not been evaluated. This study investigated the impacts of reducing dietary eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on membrane lipids in the skin of Atlantic salmon through a 26 week feeding regime supplying different levels (0-2.0% of dry mass) of EPA/DHA. Ceramide, glucosylceramide, sphingomyelin, sphingosine, and sphinganine in salmon skin were analyzed for the first time. Higher concentrations of glucosylceramide and sphingomyelin and higher ratios of glucosylceramide/ceramide and sphingomyelin/ceramide were detected in the deficient group, indicating interruptions in sphingolipidomics. Changes in the glycerol-phospholipid profile in fish skin caused by reducing dietary EPA and DHA were observed. There were no dietary impacts on epidermal thickness and mucus-cell density, but the changes in the phospholipid profile suggest that low dietary EPA and DHA may interrupt the barrier function of fish skin.

Evaluation of the Quantitative and Qualitative Alterations in the Fatty Acid Contents of the Sebum of Patients with Inflammatory Acne during Treatment with Systemic Lymecycline and/or Oral Fatty Acid Supplementation

Background. Acne is a dermatosis that involves an altered sebum pattern. Objectives. (1) To evaluate if a treatment based on antibiotics (lymecycline) can alter fatty acids contents of the sebum of patients with acne; (2) to evaluate if oral supplementation of fatty acids can interfere with fatty acids contents of the sebum of patients with acne; (3) to evaluate if there is any interaction in fatty acids contents of the sebum of patients with acne when they use both antibiotics and oral supplementation of fatty acids. Methods. Forty-five male volunteers with inflammatory acne vulgaris were treated with 300 mg of lymecycline per day, with 540 mg of γ-linolenic acid, 1,200 mg of linoleic acid, and 510 mg of oleic acid per day, or with both regimens for 90 days. Every 30 days, a sample of sebum from the forehead was collected for fatty acids' chromatographic analysis. Results. Twelve fatty acids studied exhibited some kind of pattern changes during the study: C12:0, C14:0, C15:0, C16:1, C18:0, C18:1n9c+C18:1n9t, C18:2n6t, C18:3n6, C18:3n3, C20:1, C22:0, and C24:0. Conclusions. The daily administration of lymecycline and/or specific fatty acids may slightly influence some fatty acids levels present in the sebum of patients with inflammatory acne vulgaris.

Eicosanoids in skin inflammation

Eicosanoids play an integral part in homeostatic mechanisms related to skin health and structural integrity. They also mediate inflammatory events developed in response to environmental factors, such as exposure to ultraviolet radiation, and inflammatory and allergic disorders, including psoriasis and atopic dermatitis. This review article discusses biochemical aspects related to cutaneous eicosanoid metabolism, the contribution of these potent autacoids to skin inflammation and related conditions, and considers the importance of nutritional supplementation with bioactives such as omega-3 and omega-6 polyunsaturated fatty acids and plant-derived antioxidants as means of addressing skin health issues.

Omega-3 polyunsaturated fatty acids: photoprotective macronutrients

Ultraviolet radiation (UVR) in sunlight has deleterious effects on skin, while behavioural changes have resulted in people gaining more sun exposure. The clinical impact includes a year-on-year increase in skin cancer incidence, and topical sunscreens alone provide an inadequate measure to combat overexposure to UVR. Novel methods of photoprotection are being targeted as additional measures, with growing interest in the potential for systemic photoprotection through naturally sourced nutrients. Omega-3 polyunsaturated fatty acids (n-3 PUFA) are promising candidates, showing potential to protect the skin from UVR injury through a range of mechanisms. In this review, we discuss the biological actions of n-3 PUFA in the context of skin protection from acute and chronic UVR overexposure and describe how emerging new technologies such as nutrigenomics and lipidomics assist our understanding of the contribution of such nutrients to skin health.

ALOX5 gene variants affect eicosanoid production and response to fish oil supplementation

The objective of this study was to determine whether 5-lipoxygenase (ALOX5) gene variants associated with cardiovascular disease affect eicosanoid production by monocytes. The study was a randomized, double-masked, parallel intervention trial with fish oil (5.0 g of fish oil daily, containing 2.0 g of eicosapentaenoic acid [EPA] and 1.0 g of docosahexaenoic acid [DHA]) or placebo oil (5.0 g of corn/soy mixture). A total of 116 subjects (68% female, 20-59 years old) of African American ancestry enrolled, and 98 subjects completed the study. Neither ALOX5 protein nor arachidonic acid-derived LTB4, LTD4, and LTE4 varied by genotype, but 5-hydroxyeicosatetraenoate (5-HETE), 6-trans-LTB4, 5-oxo-ETE, 15-HETE, and 5,15-diHETE levels were higher in subjects homozygous for the ALOX5 promoter allele containing five Sp1 element tandem repeats ("55" genotype) than in subjects with one deletion (d) (three or four repeats) and one common ("d5" genotype) allele or with two deletion ("dd") alleles. The EPA-derived metabolites 5-HEPE and 15-HEPE and the DHA-derived metabolite 17-HDoHE had similar associations with genotype and increased with supplementation; 5-HEPE and 15-HEPE increased, and 5-oxo-ETE decreased to a greater degree in the 55 than in the other genotypes. This differential eicosanoid response is consistent with the previously observed interaction of these variants with dietary intake of omega-3 fatty acids in predicting cardiovascular disease risk.

Healing fats of the skin: the structural and immunologic roles of the omega-6 and omega-3 fatty acids

Linoleic acid (18:2omega6) and alpha-linolenic acid (18:3omega3) represent the parent fats of the two main classes of polyunsaturated fatty acids: the omega-6 (n-6) and the omega-3 (n-3) fatty acids, respectively. Linoleic acid and alpha-linolenic acid both give rise to other long-chain fatty acid derivatives, including gamma-linolenic acid and arachidonic acid (omega-6 fatty acids) and docosahexaenoic acid and eicosapentaenoic acid (omega-3 fatty acids). These fatty acids are showing promise as safe adjunctive treatments for many skin disorders, including atopic dermatitis, psoriasis, acne vulgaris, systemic lupus erythematosus, nonmelanoma skin cancer, and melanoma. Their roles are diverse and include maintenance of the stratum corneum permeability barrier, maturation and differentiation of the stratum corneum, formation and secretion of lamellar bodies, inhibition of proinflammatory eicosanoids, elevation of the sunburn threshold, inhibition of proinflammatory cytokines (tumor necrosis factor-alpha, interferon-gamma, and interleukin-12), inhibition of lipoxygenase, promotion of wound healing, and promotion of apoptosis in malignant cells, including melanoma. They fulfill these functions independently and through the modulation of peroxisome proliferator-activated receptors and Toll-like receptors.

Systemic evening primrose oil improves the biophysical skin parameters of healthy adults

Biophysical skin parameters are indicators of age-related structural and functional changes in skin tissues. This randomized, double-blind, placebo-controlled study in healthy adults tested the effect of Efamol evening primrose oil [EPO, a gamma-linolenic acid (GLA) containing vegetable oil] on skin moisture, transepidermal water loss (TEWL), redness, firmness, elasticity, fatigue resistance and roughness. Efamol EPO was administered orally in soft gel capsules, 3 x 500 mg b.i.d. for 12 weeks. Measurements were taken at baseline and at weeks 4 and 12. The two treatment groups did not differ at baseline and at week 4. At week 12, however, all measured variables, with the exception of skin redness, were significantly different in the EPO group compared with placebo. Skin moisture, TEWL, elasticity, firmness, fatigue resistance and roughness had significantly improved by 12.9, 7.7, 4.7, 16.7, 14.2 and 21.7%, respectively. The two-sided levels of significance in favor of the EPO treatment ranged between 0.034 and 0.001. These findings lend further support to the notion that GLA is a conditionally essential fatty acid for the skin, i.e. it is unable to synthesize GLA, and therefore depends on preformed GLA for optimal structure and function.

Specific effects of gamma-linolenic, eicosapentaenoic, and docosahexaenoic ethyl esters on bone post-ovariectomy in rats

Long chain polyunsaturated fatty acids (LCPUFAs) are involved in the regulation of bone metabolism. Increased dietary consumption of n-3, and possibly some n-6, LCPUFAs may limit postmenopausal bone loss. The aim of this study was to determine the effects on bone of specific fatty acids within the n-3 and n-6 LCPUFA families in ovariectomized (OVX) rats. Rats were OVX or sham-operated and fed either a control diet (OVX and sham) or a diet supplemented with 0.5 g/kg body weight/day of gamma-linolenic (GLA), eicosapentaenoic (EPA), docosahexaenoic (DHA) ethyl esters or a mixture of all three (MIX) for 16 weeks. Bone mineral content (BMC), area, and density and plasma concentrations of insulin-like growth factor-I, vitamin D, selected biochemical markers of bone metabolism, and parathyroid hormone (PTH) were determined. The OVX-induced decrease in lumbar spine BMC was significantly attenuated by DHA but not by EPA or GLA supplementation or supplementation with a mixture of all three LCPUFAs. Endosteal circumferences of tibiae were significantly greater in DHA and EPA compared to OVX. Plasma C-terminal telopeptide of type I collagen and osteocalcin concentrations were not significantly different in the DHA group compared to OVX. Femur BMC decreased by a significantly greater amount in GLA than OVX, and final plasma PTH concentrations were significantly higher in GLA compared to all other groups. In conclusion, DHA ameliorated OVX-induced bone mineral loss. GLA exacerbated post-OVX bone mineral loss, possibly as a result of PTH-induced bone catabolism.

Long chain polyunsaturated fatty acids alter membrane-bound RANK-L expression and osteoprotegerin secretion by MC3T3-E1 osteoblast-like cells

Inflammation triggers an increase in osteoclast (bone resorbing cell) number and activity. Osteoclastogenesis is largely controlled by a triad of proteins consisting of a receptor (RANK), a ligand (RANK-L) and a decoy receptor (osteoprotegerin, OPG). Whilst RANK is expressed by osteoclasts, RANK-L and OPG are expressed by osteoblasts. The long chain polyunsaturated fatty acid (LCPUFA) arachidonic acid (AA, 20:4n-6) and its metabolite prostaglandin E2 (PGE2), are pro-inflammatory and PGE2 is a potent stimulator of RANKL expression. Various LCPUFAs such as eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and gamma-linolenic acid (GLA, 18:3n-6) have anti-inflammatory activity. We aimed to determine if AA itself can stimulate RANKL expression and whether EPA, DHA and GLA inhibit RANKL expression in osteoblasts. MC3T3-E1/4 osteoblast-like cells were cultured under standard conditions with each of the LCPUFAs (5microg/ml) for 48h. Membrane-bound RANKL expression was measured by flow cytometry and OPG secretion measured by ELISA. In a second experiment, RANKL expression in MC3T3-E1/4 cells was stimulated by PGE2 treatment and the effect of EPA, DHA and GLA on membrane-bound RANKL expression and OPG secretion determined. The percentage of RANKL-positive cells was higher (p<0.05) than controls following treatment with AA or GLA but not after co-treatment with the cyclooxygenase inhibitor, indomethacin. DHA and EPA had no effect on membrane-bound RANKL expression under standard cell culture conditions. Secretion of OPG was lower (p<0.05) in AA-treated cells but not significantly different from controls in GLA, EPA or DHA treated cells. Treatment with prostaglandin E2 (PGE2) resulted in an increase (p<0.05) in the percentage of RANK-L positive cells and a decrease (p<0.05) in mean OPG secretion. The percentage of RANKL positive cells was significantly lower following co-treatment with PGE2 and either DHA or EPA compared to treatment with PGE2 alone. Mean OPG secretion remained lower than controls in cells treated with PGE2 regardless of co-treatment with EPA or DHA. Results from this study suggest COX products of GLA and AA induce membrane-bound RANKL expression in MC3T3-E1/4 cells. EPA and DHA have no effect on membrane-bound RANKL expression in cells cultured under standard conditions however both EPA and DHA inhibit the PGE2-induced increase in RANKL expression in MC3T3-E1/4 cells.

Dietary gamma-linolenate attenuates tumor growth in a rodent model of prostatic adenocarcinoma via suppression of elevated generation of PGE(2) and 5S-HETE

Prostate cancer poses considerable threat to the aging male population as it has become a leading cause of cancer death to this group. Due to the complexity of this age-related disease, the mechanism(s) and factors resulting in prostate cancer remain unclear. Reports showing an increase risk in prostatic cancer with increasing dietary fat are contrasted by other studies suggesting the beneficial effects of certain polyunsaturated fatty acid (PUFA) in the modulation of tumor development. The n-6 PUFA, gamma-linolenic acid (GLA), has been shown to suppress tumor growth in vitro. Therefore, using the Lobund-Wistar (L-W) rat model of prostate cancer, we tested the hypothesis whether dietary supplementation of GLA could suppress tumor growth and development in vivo. Prostatic adenocarcinomas were induced in two groups of L-W rats, the experimental group (N-nitroso-N-methylurea, NMU/testosterone propionate, TP) and the GLA group (NMU/TP/GLA fed) undergoing similar treatment but fed a purified diet supplemented with GLA. Our findings revealed a decrease in prostate growth in the NMU/TP/GLA-fed group as determined by weight, tissue size, DNA content and prostate-specific antigen (tumor marker of prostate cancer). Comparison between the two groups showed a significant increase in 5S-hydroxyeicosatetraenoic acid and prostaglandin E(2) in the NMU/TP group. These increases paralleled the increased protein expression and activity of cyclooxygenase-2 as well as increased activity of 5-lipoxygenase. Taken together, the findings showed that intake of GLA-enriched diet does reduce prostatic cancer development in L-W rats and could serve as a non-toxic adjunct in management of human prostatic cancer.

The clinical benefit of moisturizers

Moisturizing creams marketed to consumers often contain trendy ingredients and are accompanied by exciting names and attractive claims. Moisturizers are also an important part of the dermatologist's armamentarium to treat dry skin conditions and maintain healthy skin. The products can be regarded as cosmetics, but may also be regulated as medicinal products if they are marketed against dry skin diseases, such as atopic dermatitis and ichthyosis. When moisturizers are used on the so-called dry skin, many distinct disorders that manifest themselves with the generally recognized symptoms of dryness are treated. Dryness is not a single entity, but is characterized by differences in chemistry and morphology in the epidermis depending on the internal and external stressors of the skin. Patients and the society expect dermatologists and pharmacists to be able to recommend treatment for various dry skin conditions upon evidence-based medicine.

LEARNING OBJECTIVE

Upon completing this paper, the reader should be aware of different types of moisturizers and their major constituents. Furthermore, s/he will know more about the relief of dryness symptoms and the functional changes of the skin induced by moisturizers.

Plasma and skin concentrations of polyunsaturated fatty acids before and after supplementation with n-3 fatty acids in dogs with atopic dermatitis

OBJECTIVE

To determine essential fatty acid concentrations in plasma and tissue before and after supplementation with n-3 fatty acids in dogs with atopic dermatitis.

ANIMALS

30 dogs with atopic dermatitis.

PROCEDURE

Dogs received supplemental flaxseed oil (200 mg/kg/d), eicosapentaenoic acid (EPA; 50 mg/kg/d)-docosahexaenoic acid (DHA; 35 mg/kg/d), or mineral oil as a placebo in a double-blind, placebo-controlled, randomized trial. Clinical scores and plasma and cutaneous concentrations of linoleic acid, arachidonic acid, alpha-linolenic acid (alpha-LLA), EPA, DHA, prostaglandin E2, and leukotriene B4 were determined.

RESULTS

Total plasma concentrations of alpha-LLA and EPA increased and those of arachidonic acid decreased significantly with administration of EPA-DHA, and concentrations of alpha-LLA increased with flaxseed oil supplementation; nevertheless, there was no significant change in the concentrations of these fatty acids or eicosanoids in the skin. There was no correlation between clinical scores and plasma or cutaneous concentrations for any of the measured fatty acids or eicosanoids.

CONCLUSION AND CLINICAL RELEVANCE

Results indicated that at the dose used, neither the concentrations of fatty acids in skin or plasma nor a decrease in the production of inflammatory eicosanoids was a major factor involved in the mechanism of action in dogs with atopy that responded to fatty acid supplementation.

15-lipoxygenase metabolites of gamma-linolenic acid/eicosapentaenoic acid suppress growth and arachidonic acid metabolism in human prostatic adenocarcinoma cells: possible implications of dietary fatty acids

Although gammalinolenic acid (GLA) and eicosapentaenoic acid (EPA) have independently been reported to suppress growth of cancer cells, their relative potencies are unknown. To determine the possible attenuating efficacies of dietary GLA or EPA on prostate carcinogenesis, we hereby report the in vitro effects of GLA, EPA and their 15-lipoxygenase (15-LOX) metabolites: 15(S)-HETrE and 15(S)-HEPE, respectively, on growth and arachidonic acid (AA) metabolism in human androgen-dependent (LNCaP) and androgen-independent (PC-3) prostatic cancer cells in culture. Specifically, both cells were preincubated respectively with the above PUFAs. Growth was determined by [3H]thymidine uptake and AA metabolism by HPLC analysis of the extracted metabolites. Our data revealed increased biosynthesis of prostaglandin E2 (PGE2) and 5-hydroxyeicosatetraenoic acid (5(S)-HETE) by both cells. Preincubation of the cells with 15(S)-HETrE or 15(S)-HEPE more markedly inhibited cellular growth and AA metabolism when compared to precursor PUFAs. Notably, 15(S)-HETrE exerted the greatest inhibitory effects. These findings therefore imply that dietary GLA rather than EPA should better attenuate prostate carcinogenesis via its in vivo generation of 15(S)-HETrE, thus warranting exploration.

Alterations of mast cell mediator production and release by gamma-linolenic and docosahexaenoic acid

The purpose of our investigations was to evaluate the supposed beneficial effects of gamma-linolenic (GLA) and docosahexaenoic acid (DHA) in a canine mastocytoma cell line (C2) as a model for canine atopic dermatitis. Cells were cultured in a basic medium (DEH) and in DEH supplemented with 14.3 microM GLA (DEH-GLA) or 14.3 microM DHA (DEH-DHA) for 8 days. Chymase and tryptase activity, as well as histamine and prostaglandin (PG)E(2) release were measured. To stimulate histamine and PGE(2) release, cells were incubated with the wasp venom peptide mastoparan (50 microM) for 30 min. GLA increased tryptase activity and decreased histamine release after C2 stimulation. DHA diminished PGE(2) production in activated C2. These results support the prescription of GLA- and DHA-enriched diets to reduce inflammatory signs in canine atopic dermatitis.

Effect of omega-3 fatty acids on canine atopic dermatitis

Twenty-nine dogs were included in a double-blinded, placebo-controlled, randomised trial and were orally supplemented for 10 weeks with either flax oil (200 mg/kg/day), eicosapentaenoic acid (50 mg/kg/day) and docosahexaenoic acid (35 mg/kg/day) in a commercial preparation, or mineral oil as a placebo. For each dog, clinical scores were determined based on a scoring system developed prior to the trial. Total omega-6 and omega-3 intake and the ratio of omega-6:omega-3 (omega-6:3) were calculated before and after the trial. The dogs' clinical scores improved in those supplemented with flax oil and the commercial preparation, but not in the placebo group. No correlation was identified between total fatty acid intake or omega-6:3 ratio and clinical scores. Based on the results of this study, the total intake of fatty acids or the omega-6:3 ratio do not seem to be the main factors in determining the clinical response.

Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders

Emollients and moisturizing creams are used to break the dry skin cycle and to maintain the smoothness of the skin. The term 'moisturizer' is often used synonymously with emollient, but moisturizers often contain humectants in order to hydrate the stratum corneum. Dryness is frequently linked to an impaired barrier function observed, for example, in atopic skin, psoriasis, ichthyosis, and contact dermatitis. Dryness and skin barrier disorders are not a single entity, but are characterized by differences in chemistry and morphology in the epidermis. Large differences also exist between moisturizing creams. Moisturizers have multiple functions apart from moistening the skin. Similar to other actives, the efficacy is likely to depend on the dosage, where compliance is a great challenge faced in the management of skin diseases. Strong odor from ingredients and greasy compositions may be disagreeable to the patients. Furthermore, low pH and sensory reactions, from lactic acid and urea for example, may reduce patient acceptance. Once applied to the skin, the ingredients can stay on the surface, be absorbed into the skin, be metabolized, or disappear from the surface by evaporation, sloughing off, or by contact with other materials. In addition to substances considered as actives, e.g. fats and humectants, moisturizers contain substances conventionally considered as excipients (e.g. emulsifiers, antioxidants, preservatives). Recent findings indicate that actives and excipients may have more pronounced effects in the skin than previously considered. Some formulations may deteriorate the skin condition, whereas others improve the clinical appearance and skin barrier function. For example, emulsifiers may weaken the barrier. On the other hand, petrolatum has an immediate barrier-repairing effect in delipidized stratum corneum. Moreover, one ceramide-dominant lipid mixture improved atopic dermatitis and decreased transepidermal water loss (TEWL) in an open-label study in children. In double-blind studies moisturizers with urea have been shown to reduce TEWL in atopic and ichthyotic patients. Urea also makes normal and atopic skin less susceptible against irritation to sodium laurilsulfate. Treatments improving the barrier function may reduce the likelihood of further aggravation of the disease. In order to have optimum effect it is conceivable that moisturizers should be tailored with respect to the epidermal abnormality. New biochemical approaches and non-invasive instruments will increase our understanding of skin barrier disorders and facilitate optimum treatments. The chemistry and function of dry skin and moisturizers is a challenging subject for the practicing dermatologist, as well as for the chemist developing these agents in the pharmaceutical/cosmetic industry.

Dietary CLA and DHA modify skin properties in mice

This study investigated the influence of PUFA on the properties of mouse skin. Mice (3 wk old) were given free access to oils high in linoleic acid, CLA, or DHA for 4 wk. At the end of the experiment, their skins were compared by both biochemical and histological methods. No significant differences in lipid and collagen contents were detected among treatments, although the FA composition in the skin was altered depending upon the FA composition of the supplemented oils. Electron microscopy revealed that the subcutaneous tissue layers in the CLA and DHA groups were significantly thinner than that in the high linoleic acid group, whereas no differences in the thickness of dermis layers were observed among the three groups. These results suggest that skin properties in mice are readily modified by dietary FA sources within 4 wk of dietary oil supplementation.

Novel docosatrienes and 17S-resolvins generated from docosahexaenoic acid in murine brain, human blood, and glial cells. Autacoids in anti-inflammation

Docosahexaenoic acid (DHA, C22:6) is highly enriched in brain, synapses, and retina and is a major omega-3 fatty acid. Deficiencies in this essential fatty acid are reportedly associated with neuronal function, cancer, and inflammation. Here, using new lipidomic analyses employing high performance liquid chromatography coupled with a photodiode-array detector and a tandem mass spectrometer, a novel series of endogenous mediators was identified in blood, leukocytes, brain, and glial cells as 17S-hydroxy-containing docosanoids denoted as docosatrienes (the main bioactive member of the series was 10,17S-docosatriene) and 17S series resolvins. These novel mediators were biosynthesized via epoxide-containing intermediates and proved potent (pico- to nanomolar range) regulators of both leukocytes reducing infiltration in vivo and glial cells blocking their cytokine production. These results indicate that DHA is the precursor to potent protective mediators generated via enzymatic oxygenations to novel docosatrienes and 17S series resolvins that each regulate events of interest in inflammation and resolution.

Different effects of n-6 and n-3 polyunsaturated fatty acids on the activation of rat smooth muscle cells by interleukin-1 beta

There is good evidence that the n-3 polyunsaturated fatty acids (PUFAs) in fish oil have antiinflammatory effects and reduce the pathogenesis of atherosclerosis. However, the mechanisms underlying these actions are largely unknown. This study was designed to investigate the effects of membrane incorporation of two major components of fish oil [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)], on rat smooth muscle cells (SMCs) activation induced by interleukin-1 beta (IL1 beta). We compared their effects with those of n-6 arachidonic acid (AA). Expression of vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1 adhesion molecules involved in SMCs migration was enhanced by AA, whereas EPA and DHA had no similar effects. We established that AA potentiates IL1 beta-induced expression of the type IIA secreted phospholipase A2 (sPLA2) gene, whereas EPA and DHA reduce this stimulation. EPA and DHA also abolished proinflammatory prostaglandin PGE2 production by inhibiting the IL1 beta-induced production of cyclooxygenase-2 (COX-2) mRNA. Much interest was then focused on three transcriptional factors implicated in inflammation control and especially in modulating rat sPLA2 and COX-2 gene transcription: nuclear factor-kappa B, CCAAT/enhancer binding protein beta, and E26 transformation-specific-1. electrophoretic mobility shift assay revealed that the binding activity of all three factors was increased by AA and reduced (or not affected) by n-3 PUFA. These results indicate that EPA and DHA act in opposition to AA by modulating various steps of the inflammatory process induced by IL1 beta, probably by reducing mitogen-activated protein kinase p42/p44 activity.

Biological significance of essential fatty acids/prostanoids/lipoxygenase-derived monohydroxy fatty acids in the skin

The skin displays a highly active metabolism of polyunsaturated fatty acids (PUFA). Dietary deficiency of linoleic acid (LA), an 18-carbon (n-6) PUFA, results in characteristic scaly skin disorder and excessive epidermal water loss. Although arachidonic acid (AA), a 20-carbon (n-6) PUFA, is metabolized via cyclooxygenase pathway into predominantly prostaglandin E2 (PGE2) and PGF2alpha, the metabolism of AA via the 15-lipoxygenase (15-LOX) pathway, which is very active in skin epidermis and catalyzes the transformation of AA into predominantly 15S-hydroxyeicosatetraenoic acid (15S-HETE). Additionally, the 15-LOX also metabolizes the 18-carbon LA into 13S-hydroxyoctadecadienoic acid (13S-HODE), respectively. Interestingly, 15-LOX catalyzes the transformation of dihomo-gamma-linolenic acid (DGLA), derived from dietary gamma-linolenic acid, to 15S-hydroxyeicosatrienoic acid (15S-HETrE). These monohydroxy fatty acids are incorporated into the membrane inositol phospholipids which undergo hydrolytic cleavage to yield substituted-diacylglycerols such as 13S-HODE-DAG from 13S-HODE and 15S-HETrE-DAG from 15S-HETrE. These substituted-monohydroxy fatty acids seemingly exert anti-inflammatory/antiproliferative effects via the modulation of selective protein kinase C as well as on the upstream/down-stream nuclear MAP-kinase/AP-1/apoptotic signaling events.

5 alpha-reductase-catalyzed conversion of testosterone to dihydrotestosterone is increased in prostatic adenocarcinoma cells: suppression by 15-lipoxygenase metabolites of gamma-linolenic and eicosapentaenoic acids

Although the androgens, testosterone (T) and its highly active metabolite dihydrotestosterone (DHT) play a role in the development and progression of prostate cancer, the mechanism(s) are unclear. Furthermore, 5 alpha-reductase which catalyze the conversion of T to DHT, has been a target of manipulation in the treatment of prostatic cancer, hence synthetic 5 alpha-reductase activity inhibitors have shown therapeutic promise. To demonstrate that nutrients derived from dietary sources can exert similar therapeutic promise, this study was designed using benign hyperplastic cells (BHC) and malignant tumorigenic cells (MTC) derived from Lobund-Wistar (L-W) rat model of prostatic adenocarcinoma to test the effects of gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and their 15-lipoxygenase metabolites on cellular 5 alpha-reductase activity. Our data revealed: (i) that incubation of MTC with [3H]-T resulted in marked conversion to [3H]-DHT when compared to similar incubation with BHC; (ii) that DHT-enhanced activity of 5 alpha-reductase was inhibited 80% by 15S-hydroxyeicosatrienoic acid, the 15-lipoxygenase metabolite of GLA, when compared to 55% by 15S-hydroxyeicosapentaenoic acid, the 15-lipoxygenase metabolite of EPA; and (iii) that their precursor fatty acids, respectively, exerted moderate inhibition. Taken together, the study underscores the biological importance of 15-lipoxygenase metabolites of polyunsaturated fatty acids (PUFAs) in androgen metabolism.

Resolvins: a family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammation signals

Aspirin (ASA) is unique among current therapies because it acetylates cyclooxygenase (COX)-2 enabling the biosynthesis of R-containing precursors of endogenous antiinflammatory mediators. Here, we report that lipidomic analysis of exudates obtained in the resolution phase from mice treated with ASA and docosahexaenoic acid (DHA) (C22:6) produce a novel family of bioactive 17R-hydroxy-containing di- and tri-hydroxy-docosanoids termed resolvins. Murine brain treated with aspirin produced endogenous 17R-hydroxydocosahexaenoic acid as did human microglial cells. Human COX-2 converted DHA to 13-hydroxy-DHA that switched with ASA to 17R-HDHA that also proved a major route in hypoxic endothelial cells. Human neutrophils transformed COX-2-ASA-derived 17R-hydroxy-DHA into two sets of novel di- and trihydroxy products; one initiated via oxygenation at carbon 7 and the other at carbon 4. These compounds inhibited (IC(50) approximately 50 pM) microglial cell cytokine expression and in vivo dermal inflammation and peritonitis at ng doses, reducing 40-80% leukocytic exudates. These results indicate that exudates, vascular, leukocytes and neural cells treated with aspirin convert DHA to novel 17R-hydroxy series of docosanoids that are potent regulators. These biosynthetic pathways utilize omega-3 DHA and EPA during multicellular events in resolution to produce a family of protective compounds, i.e., resolvins, that enhance proresolution status.

Gamma-linolenic acid in borage oil reverses epidermal hyperproliferation in guinea pigs

As dietary sources of gamma-linolenic acid [GLA; 18:3(n-6)], borage oil (BO; 24-25 g/100 g GLA) and evening primrose oil (PO; 8-10 g/100 g GLA) are efficacious in treating skin disorders. The triglycerol stereospecificity of these oils is distinct, with GLA being concentrated in the sn-2 position of BO and in the sn-3 position of PO. To determine whether the absolute level and/or the triglycerol stereospecificity of GLA in oils affect biological efficacy, epidermal hyperproliferation was induced in guinea pigs by a hydrogenated coconut oil (HCO) diet for 8 wk. Subsequently, guinea pigs were fed diets of PO, BO or a mixture of BO and safflower oil (SO) for 2 wk. The mixture of BO and SO (BS) diet had a similar level of GLA as PO but with sn-2 stereospecificity. As controls, two groups were fed SO and HCO for 10 wk. Epidermal hyperproliferation was reversed by all three oils in the order of BO > BS > PO. However, proliferation scores of group PO were higher than of the normal control group, SO. The accumulations of dihomo-gamma-linolenic acid [DGLA; 20:3(n-6)], an elongase product of GLA, into phospholipids and ceramides, of 15-hydroxyeicosatrienoic acid (15-HETrE), the potent antiproliferative metabolite of DGLA, and of ceramides, the major lipid maintaining epidermal barrier, in the epidermis of group BO were greater than of groups BS and PO. Group BS had higher levels of DGLA, 15-HETrE and ceramides than group PO. With primary dependence on absolute levels, our data demonstrate that the antiproliferative efficacy of GLA in the epidermis is preferably exerted from sn-2 stereospecificity of GLA in BO.

Polyunsaturated fatty acids and inflammatory diseases

Inflammation is overall a protective response, whose main goal is to liberate the human being of cellular lesions caused by micro-organisms, toxins, allergens, etc., as well as its consequences, and of death cells and necrotic tissues. Chronic inflammation, which is detrimental to tissues, is the basic pathogenic mechanism of hypersensitivity reactions against xenobiotics. Other frequent pathologies, for instance atherosclerosis, chronic hepatitis, inflammatory bowel disease (IBD), liver cirrhosis, lung fibrosis, psoriasis, and rheumatoid arthritis are also chronic inflammatory diseases. Chemical mediators of inflammation are derived from blood plasma or different cell-type activity. Biogenic amines, eicosanoids and cytokines are within the most important mediators of inflammatory processes. The different activities of eicosanoids derived from arachidonic acid (20:4 n-6) versus those derived from eicosapentaenoic acid (20:5 n-3) are one of the most important mechanisms to explain why n-3, or omega-3, polyunsaturated fatty acids (PUFA) exhibit anti-inflammatory properties in many inflammatory diseases. Dietary supplements ranging 1-8 g per day of n-3 PUFA have been reportedly beneficial in the treatment of IBD, eczema, psoriasis and rheumatoid arthritis. In addition, recent experimental studies in rats with experimental ulcerative colitis, induced by intrarectal injection of trinitrobenzene sulphonic acid, have documented that treatment with n-3 long-chain PUFA reduces mucosal damage as assessed by biochemical and histological markers of inflammation. Moreover, the defence antioxidant system in this model is enhanced in treated animals, provided that the n-3 PUFA supply is adequately preserved from oxidation.

Effect of corticosteroids and eicosapentaenoic acid/docosahexaenoic acid on pro-oxidant and anti-oxidant status and metabolism of essential fatty acids in patients with glomerular disorders

It is known that the concentrations of essential fatty acids and their metabolites including eicosanoids, free radicals and anti-oxidants are altered in glomerular disorders. Both corticosteroids and n-3 fatty acids--eicosapentaenoic acid and docosahexaenoic acid (EPA and DHA respectively)--are useful in the management of glomerular disorders. In the present study, the altered plasma concentrations of lipid peroxides, nitric oxide and the metabolites of essential fatty acids and anti-oxidants--superoxide dismutase, glutathione peroxidase and vitamin E--in the RBC membranes of patients with glomerular disorders (nephrotic syndrome) reverted to normalcy following corticosteroids or EPA/DHA administration. This suggests that the beneficial actions of corticosteroids and EPA/DHA in glomerular disorders can be attributed to their action on the pro-oxidant and anti-oxidant concentrations and metabolism of essential fatty acids.

The ACVD task force on canine atopic dermatitis (XXIII): are essential fatty acids effective?

Essential fatty acids (EFAs) exhibit the potential to affect allergic inflammation through the modulation of prostaglandin and leukotriene production, the inhibition of cellular activation and cytokine secretion as well as the alteration of the composition and function of the epidermal lipid barrier. Because of these multi-faceted effects, EFA have been proposed for treatment of canine atopic dermatitis (AD) since 1987. To date, more than 20 trials have been performed, reporting the efficacy of either oral EFA supplements or EFA-rich diets. Unfortunately, most of these studies were found to exhibit one or more of the following deficiencies: heterogeneity of diagnoses used as inclusion criteria, short duration of supplementation, lack of randomization of treatment allocation, lack of blinding of investigators and/or owners, lack of placebo or active controls, lack of documentation of plasma or skin EFA profiles during supplementation, as well as lack of standardization of the basal diets or supplements which could have provided additional EFA. Consequently, there is presently insufficient evidence to recommend for or against the use of EFA to control clinical signs of canine AD. Evidence of efficacy must await the performance of blinded, randomized and controlled trials of at least 3 months duration in which diets are identical for all of study subjects. In these trials, clinical efficacy should be evaluated in relation to plasma and cutaneous EFA treatment-induced alterations.

Current prospects for controlling cancer growth with non-cytotoxic agents--nutrients, phytochemicals, herbal extracts, and available drugs

In animal or cell culture studies, the growth and spread of cancer can be slowed by many nutrients, food factors, herbal extracts, and well-tolerated, available drugs that are still rarely used in the clinical management of cancer, in part because they seem unlikely to constitute definitive therapies in themselves. However, it is reasonable to expect that mechanistically complementary combinations of these measures could have a worthwhile impact on survival times and, when used as adjuvants, could improve the cure rates achievable with standard therapies. The therapeutic options available in this regard include measures that: down-regulate serum free IGF-I; suppress the synthesis of mevalonic acid and/or certain derivatives thereof; modulate arachidonate metabolism by inhibiting 5-lipoxygenase, 12-lipoxygenase, or COX-2; antagonize the activation of AP-1 transcription factors; promote the activation of PPAR-gamma transcription factors; and that suppress angiogenesis by additional mechanisms. Many of these measures appear suitable for use in cancer prevention.

Metabolism of polyunsaturated fatty acids by skin epidermal enzymes: generation of antiinflammatory and antiproliferative metabolites

In the skin epidermis, the metabolism of polyunsaturated fatty acids (PUFAs) is highly active. Dietary deficiency of linoleic acid (LA), the major 18-carbon n-6 PUFA in normal epidermis, results in a characteristic scaly skin disorder and excessive epidermal water loss. Because of the inability of normal skin epidermis to desaturate LA to gamma-linolenic acid, it is transformed by epidermal 15-lipoxygenase to mainly 13-hydroxyoctadecadienoic acid, which functionally exerts antiproliferative properties in the tissue. In contrast, compared with LA, arachidonic acid (AA) is a relatively minor 20-carbon n-6 PUFA in the skin and is metabolized via the cyclooxygenase pathway, predominantly to the prostaglandins E(2), F(2)(alpha), and D(2). AA is also metabolized via the 15-lipoxygenase pathway, predominantly to 15-hydroxyeicosatetraenoic acid. At low concentrations, the prostaglandins function to modulate normal skin physiologic processes, whereas at high concentrations they induce inflammatory processes. PUFAs derived from other dietary oils are also transformed mainly into monohydroxy fatty acids. For instance, epidermal 15-lipoxygenase transforms dihomo-gamma-linolenic acid (20:3n-6) to 15-hydroxyeicosatrienoic acid, eicosapentaenoic acid (20:5n-3) to 15-hydroxyeicosapentaenoic acid, and docosahexaenoic acid (22:6n-3) to 17-hydroxydocosahexaenoic acid, respectively. These monohydroxy acids exhibit antiinflammatory properties in vitro. Thus, supplementation of diets with appropriate purified vegetable oils, fish oil, or both may generate local cutaneous antiinflammatory and antiproliferative metabolites which could serve as less toxic in vivo monotherapies or as adjuncts to standard therapeutic regimens for the management of inflammatory skin disorders.

Vascular nitric oxide, sex hormone replacement, and fish oil may help to prevent Alzheimer's disease by suppressing synthesis of acute-phase cytokines

The neurodegenerative plaques of Alzheimer's disease (AD) are characterized by a self-sustaining acute-phase reaction in which both interleukin-1 (IL-1) and interleukin-6 (IL-6) are up-regulated. The fact that IL-6 is detectable in early stage diffuse plaques encourages the speculation that the acute-phase process is crucial to the pathogenesis of AD. The epidemiological association of AD with estrogen deficiency, as well as with various disorders characterized by vascular endotheliopathy, suggest a protective role for vascular nitric oxide (NO). NO has an autocrine anti-inflammatory impact on endothelium, owing in part to antagonism of NF-kappaB activity; since induction of IL-6 is dependent on NF-kappaB, this may explain recent evidence that NO inhibits macrophage IL-6 production. It is reasonable to postulate that, analogously, cerebrovascular NO decreases IL-6 production in the brain. Vascular NO may also have direct neuroprotective activity. Estrogen, in addition to promoting vascular NO synthesis, can block IL-6 production by a more direct mechanism in cells expressing estrogen receptors; since such receptors have been reported in brain glia and astrocytes, estrogen has the potential to limit brain IL-1 activity. Testosterone likewise can inhibit IL-6 induction in androgen-responsive cells, which may include brain glia and astrocytes. Since fish oil and gamma linolenic acid (GLA) suppress IL-1 production by stimulated monocytes, they conceivably could exert this effect in the brain as well; the comparatively low prevalence of AD in elderly Japanese is intriguing in this regard. These considerations suggest that a healthy cerebrovascular endothelium, sex hormone activity, and dietary fish oil/GLA may slow or prevent AD onset by dampening acute-phase mechanisms in the brain.

Niacinamide therapy for osteoarthritis--does it inhibit nitric oxide synthase induction by interleukin 1 in chondrocytes?

Fifty years ago, Kaufman reported that high-dose niacinamide was beneficial in osteoarthritis (OA) and rheumatoid arthritis. A recent double-blind study confirms the efficacy of niacinamide in OA. It may be feasible to interpret this finding in the context of evidence that synovium-generated interleukin-1 (IL-1), by inducing nitric oxide (NO) synthase and thereby inhibiting chondrocyte synthesis of aggrecan and type II collagen, is crucial to the pathogenesis of OA. Niacinamide and other inhibitors of ADP-ribosylation have been shown to suppress cytokine-mediated induction of NO synthase in a number of types of cells; it is therefore reasonable to speculate that niacinamide will have a comparable effect in IL-1-exposed chondrocytes, blunting the anti-anabolic impact of IL-1. The chondroprotective antibiotic doxycycline may have a similar mechanism of action. Other nutrients reported to be useful in OA may likewise intervene in the activity or synthesis of IL-1. Supplemental glucosamine can be expected to stimulate synovial synthesis of hyaluronic acid; hyaluronic acid suppresses the anti-catabolic effect of IL-1 in chondrocyte cell cultures, and has documented therapeutic efficacy when injected intra-articularly. S-adenosylmethionine (SAM), another proven therapy for OA, upregulates the proteoglycan synthesis of chondrocytes, perhaps because it functions physiologically as a signal of sulfur availability. IL-1 is likely to decrease SAM levels in chondrocytes; supplemental SAM may compensate for this deficit. Adequate selenium nutrition may down-regulate cytokine signaling, and ample intakes of fish oil can be expected to decrease synovial IL-1 production; these nutrients should receive further evaluation in OA. These considerations suggest that non-toxic nutritional regimens, by intervening at multiple points in the signal transduction pathways that promote the synthesis and mediate the activity of IL-1, may provide a substantially superior alternative to NSAIDs (merely palliative and often dangerously toxic) in the treatment and perhaps prevention of OA.

Interleukin-6 as a central mediator of cardiovascular risk associated with chronic inflammation, smoking, diabetes, and visceral obesity: down-regulation with essential fatty acids, ethanol and pentoxifylline

Increased plasma levels of fibrinogen and C-reactive protein (CRP), as well as leukocytosis, are now established as risk factors for the thromboembolic complications of vascular disease. Chronic inflammation or infection associated with an acute-phase response--notably, periodontal disease and smoking-induced lung damage--are likewise known to increase cardiovascular risk. A common etiologic factor in these conditions may be interleukin-6 (IL-6), acting on hepatocytes to induce acute-phase reactants that increase blood viscosity and promote thrombus formation. Recent evidence that hypertrophied adipocytes release IL-6, and that hyperglycemia evokes IL-6 production by endothelium, may explain why plasma fibrinogen is increased in visceral obesity and poorly controlled diabetes. IL-6 is released by a range of tissues in response to stimulation by the monocyte-derived cytokines interleukin-1 and tumor necrosis factor; by suppressing production of these cytokines, fish oil, alpha-linolenic acid, and pentoxifylline can reduce IL-6 synthesis. Moderate ethanol consumption, as well as sex-hormone replacement, also appear to inhibit IL-6 production or activity. These practical protective measures may be of particular value to patients with pre-existing atheroma and elevated plasma levels of acute-phase reactants. Since IL-6 plays a crucial physiological role in osteoclast generation and activation, these measures may also aid preservation of bone density.

A blinded, placebo-controlled study of the efficacy of borage seed oil and fish oil in the management of canine atopy

Twenty-one dogs with atopy were entered into a blinded, placebo-controlled study lasting eight weeks. They were randomly divided into three groups and were all given supplementary oils orally once daily. The dogs in groups A and B were given borage seed oil and fish oil in combination (Viacutan; Boehringer Ingelheim Vetmedica) to provide 176 mg/kg or 88 mg/kg borage seed oil respectively. The dogs in group C were given 204 mg/kg olive oil as a placebo. They were all re-examined after four and eight weeks and scored for pruritus, erythema, oedema, alopecia and self-excoriation. After eight weeks the scores for erythema and self-excoriation, and the total score for the dogs in group A, and the total score for the dogs in group B were significantly reduced (P < 0.05). The dogs in group C showed no significant improvement.

Evidence of nuclear PKC/MAP-kinase cascade in guinea pig model of epidermal hyperproliferation

In order to delineate the biochemical events in the nuclear compartment of an in vivo proliferating epidermis, we produced a model of hyperproliferative epidermis by topical application of docosahexaenoic acid (22:6n-3) on guinea pig skin. Employing this model we demonstrated: (i) that protein kinase C (PKC)-a and atypical PKC-zeta are the two major PKC isozymes in the normal epidermal nuclear membrane, in contrast to PKC-alpha and PKC-beta in the epidermal plasma membrane; (ii) that topical application of docosahexaenoic acid induced epidermal hyperproliferation and enhanced total nuclear PKC, particularly nuclear PKC-alpha and the atypical PKC-zeta isozymes. The increase in the nuclear PKC isozymes paralleled a marked increase in the expression of nuclear mitogen-activated protein-kinase. These data suggest that epidermal hyperproliferative activity is accompanied by the upregulation of nuclear PKC/mitogen-activated protein-kinase signaling pathway.

Importance of dietary gamma-linolenic acid in human health and nutrition

Considerable debate remains regarding the distinct biological activities of individual polyunsaturated fatty acids (PUFA). One of the most interesting yet controversial dietary approaches has been the possible prophylactic role of dietary gamma-linolenic acid (GLA) in treating various chronic disease states. This strategy is based on the ability of diet to modify cellular lipid composition and eicosanoid (cyclooxygenase and lipoxygenase) biosynthesis. Recent studies demonstrate that dietary GLA increases the content of its elongase product, dihomo-gamma-linolenic acid (DGLA), within cell membranes without concomitant changes in arachidonic acid (AA). Subsequently, upon stimulation, DGLA can be converted by inflammatory cells to 15-(S)-hydroxy-8,11,13-eicosatrienoic acid and prostaglandin E1. This is noteworthy because these compounds possess both anti-inflammatory and antiproliferative properties. Although an optimal feeding regimen to maximize the potential benefits of dietary GLA has not yet been determined, it is the purpose of this review to summarize the most recent research that has focused on objectively and reproducibly determining the mechanism(s) by which GLA may ameliorate health problems.

Nitric oxide deficiency, leukocyte activation, and resultant ischemia are crucial to the pathogenesis of diabetic retinopathy/neuropathy--preventive potential of antioxidants, essential fatty acids, chromium, ginkgolides, and pentoxifylline

Impaired microcirculatory perfusion appears to be crucial to the pathogenesis of both neuropathy and retinopathy in diabetics. This in turn reflects a hyperglycemically mediated perturbation of vascular endothelial function that entails overactivation of protein kinase C, reduced availability of nitric oxide, increased production of superoxide and endothelin, impaired insulin function, diminished synthesis of prostacyclin/PGE1, and increased activation and endothelial adherence of leukocytes. These dysfunctions may be addressed with a supplementation program that includes high-dose antioxidants, fish oil, gamma-linolenic acid, chromium, arginine, carnitine, and ginkgolides. Pharmaceuticals likely to be of benefit in this regard include pentoxifylline, probucol, replacement estrogens, and inhibitors of angiotensin converting enzyme and aldose reductase.

gamma-Linolenic acid-containing diet attenuates bleomycin-induced lung fibrosis in hamsters

Although bleomycin (BLM), an antineoplastic drug, is used in the treatment of a variety of tumors, the mechanism(s) that contribute to its induced lung injury and fibrosis are not fully elucidated. Since alterations in the levels of certain fatty acid metabolites have been associated with BLM-induced lung injury, we tested the effects of dietary gamma-linolenic acid (GLA)-containing evening primrose oil on BLM-induced morphological alterations in the hamster lung, the marked elevation of tissue hydroxyproline (a marker for collagen synthesis), and elevated generation of arachidonic acid metabolites (marker of inflammatory mediators). Our data revealed that after 14 d of dietary GLA-containing oil (i) BLM-induced elevation of lung hydroxyproline was suppressed (P < 0.05), (ii) the marked BLM-induced elevation of lung leukotriene B4 (LTB4) (a marker of polymorphanuclear generation of proinflammatory LTB4) was significantly suppressed (P < 0.05). The decrease in LTB4 was accompanied by marked elevations (P < 0.05) of lung prostaglandin E1 (PGE1) and 15-hydroxyeicosatrienoic acid (15-HETrE), both with known antiinflammatory properties. Taken together, data from these studies suggest that dietary GLA-containing oil contributes to tissue elevation of PGE1 and 15-HETrE, which in vivo may attenuate lung inflammation and fibrosis.

Glucosamine for psoriasis?

Amphiregulin and transforming growth factor-alpha, agonists for the epidermal growth factor receptor, are the major autocrine growth factors for cultured keratinocytes, and their substantial overexpression in psoriatic lesions suggests that they are crucial to the basal hyperplasia that characterizes psoriasis. Amphiregulin binds to heparin and related highly sulfated polysaccharides, and exogenous heparin blocks its growth factor activity, rationalizing previous reports that psoriasis responds to heparin therapy. Differentiating keratinocytes produce increased amounts of protein-bound as well as free-chain heparan sulfates, which may function physiologically as amphiregulin antagonists. By promoting keratinocyte synthesis of these heparan sulfates, glucosamine administration may inhibit amphiregulin function and thus provide therapeutic benefit in psoriasis. Concurrent ingestion of fish oil, by impeding the excessive activation of protein kinase C, may decrease keratinocyte production of amphiregulin and other autocrine growth factors, thus complementing the postulated benefits of glucosamine.

The significance of polyunsaturated fatty acids in cutaneous biology

The skin epidermis displays a highly active metabolism of polyunsaturated fatty acids (PUFA). Dietary deficiency of linoleic acid (LA) and 18-carbon (n-6) PUFA results in characteristic scaly skin disorder and excessive epidermal water loss. Arachidonic acid, a 20-carbon (n-6) PUFA is metabolized via the cyclooxygenase pathway into predominantly prostaglandin E2 (PGE2) PGF2 alpha, and PGD2 and via the lipoxygenase pathway into predominantly 15-hydroxyeicosatetraenoic acid (15-HETE). The prostaglandins modulate normal skin physiological processes at low concentrations and inflammatory reactions at high concentrations. Similarly, the very active epidermal 15-lipoxygenase transforms dihomogammalinolenic acid (DGLA) into 15-hydroxy eicosatrienoic acid (15-HETrE), eicosapentaenoic acid (EPA) into 15-hydroxyeicosapentaenoic acid (15-HEPE) and docosahexaenoic acid (DHA) into 17-hydroxydocosahexaenoic acid (17-HDoHE), respectively. These monohydroxy acids exhibit anti-inflammatory properties. In contrast, the 18-carbon (n-6) PUFA is transformed into 13-hydroxy-9,11-octadecadienoic acid (13-HODE), which exerts antiproliferative properties in the tissue. Thus, the supplementation of diets with appropriate purified vegetable oils and/or fish oil may generate local cutaneous anti-inflammatory metabolites which could serve as a less toxic in vivo monotherapy or as adjuncts to standard therapeutic regimens for the management of skin inflammatory disorders.

Fish oil may impede tumour angiogenesis and invasiveness by down-regulating protein kinase C and modulating eicosanoid production

Inhibition of angiogenesis shows considerable promise as a strategy for treating solid malignancies. Induction of collagenase by protein kinase C plays an important role in the angiogenic process as well as in metastasis. Lipoxygenase products are required for endothelial cell mitosis, and also promote collagenase production. By down-regulating hormonal activation of protein kinase C and modulating eicosanoid metabolism, ingestion of omega-3-rich fish oils may impede angiogenesis and reduce tumor invasiveness-thus rationalizing the growth-retardant and anti-metastatic effects of fish oil feeding almost invariably seen in animal tumour models. Certain other anti-inflammatory agents-including cromolyn (an inhibitor of protein kinase C activation) and gamma-linolenic acid (which indirectly inhibits lipoxygenase) may have analogous tumour-retardant activity. Clinical application of supplemental fish oil in cancer therapy is long overdue.