15-hydroxyeicosatrienoic acid (15-HETrE) suppresses epidermal hyperproliferation via the modulation of nuclear transcription factor (AP-1) and apoptosis

Expanding the biosynthesis spectrum of hydroxy fatty acids: unleashing the potential of novel bacterial fatty acid hydratases

BACKGROUND

Hydroxy fatty acids represent an emerging class of compounds with promising applications in the chemical, medicinal and functional food sectors. The challenges associated with their chemical synthesis have spurred exploration of biological synthesis as an alternative route, particularly through the use of fatty acid hydratases. Fatty acid hydratases catalyse the regioselective addition of a hydrogen atom and a hydroxyl group from a water molecule to the carbon-carbon cis-double bond of unsaturated fatty acids to form hydroxy fatty acids. Despite having been discovered in the early 1960s, previous research has primarily focused on characterizing single fatty acid hydratase variants with a limited range of substrates. Comprehensive studies that systematically examine and compare the characteristics of multiple variants of fatty acid hydratases are still lacking.

RESULTS

In this study, we employed an integrated bioinformatics workflow to identify 23 fatty acid hydratases and characterized their activities against nine unsaturated fatty acid substrates using whole-cell biotransformation assays. Additionally, we tested a dual-protein system involving two fatty acid hydratases of distinct regioselectivity and demonstrated its suitability in enhancing the biosynthesis of di-hydroxy fatty acids.

CONCLUSIONS

Our study demonstrates that fatty acid hydratases can be classified into three subtypes based on their regioselectivity and provides insights into their preferred substrate structures. These understandings pave ways for the design of optimal fatty acid hydratase variants and bioprocesses for the cost-efficient biosynthesis of hydroxy fatty acids.

Liquid Chromatography-Tandem Mass Spectrometry-Based Metabolomics Analysis of Indigo Naturalis Treatment of Ulcerative Colitis in Mice

Ulcerative colitis (UC), often known as UC, is an inflammatory disease of the intestines that has frequent and long-lasting flare-ups. It is unknown precisely how the traditional Chinese drug Indigo Naturalis (IN) heals inflammatory bowel disease, despite its long-standing use in China and Japan. Finding new metabolite biomarkers linked to UC could improve our understanding of the disease, speed up the diagnostic process, and provide insight into how certain drugs work to treat the condition. Our work is designed to use a metabolomic method to analyze potential alterations in endogenous substances and their impact on metabolic pathways in a mouse model of UC. To determine which biomarkers and metabolisms are more frequently connected with IN's effects on UC, liquid chromatography-tandem mass spectrometry analysis of the serum metabolomics of UC mice and normal mice was performed. The outcomes demonstrated that IN boosted the health of UC mice and reduced the severity of their metabolic dysfunction. In the UC model, it was also found that IN changed the way 17 biomarkers and 3 metabolisms functioned.

Influence of Dietary n-3 Long Chain Polyunsaturated Fatty Acid Intake on Oxylipins in Erythrocytes of Women with Rheumatoid Arthritis

Oxylipins derived from n-3 fatty acids are suggested as the link between these fatty acids and reduced inflammation. The aim of the present study was to explore the effect of a randomized controlled cross-over intervention on oxylipin patterns in erythrocytes. Twenty-three women with rheumatoid arthritis completed 2 × 11-weeks exchanging one cooked meal per day, 5 days a week, for a meal including 75 g blue mussels (source for n-3 fatty acids) or 75 g meat. Erythrocyte oxylipins were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results were analyzed with multivariate data analysis. Orthogonal projections to latent structures (OPLS) with effect projections and with discriminant analysis were performed to compare the two diets' effects on oxylipins. Wilcoxon signed rank test was used to test pre and post values for each dietary period as well as post blue-mussel vs. post meat. The blue-mussel diet led to significant changes in a few oxylipins from the precursor fatty acids arachidonic acid and dihomo-ɣ-linolenic acid. Despite significant changes in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and free EPA in erythrocytes in the mussel group, no concurrent changes in their oxylipins were seen. Further research is needed to study the link between n-3 fatty-acid intake, blood oxylipins, and inflammation.

Something Smells Fishy: How Lipid Mediators Impact the Maternal-Fetal Interface and Neonatal Development

Normal pregnancy relies on inflammation for implantation, placentation, and parturition, but uncontrolled inflammation can lead to poor maternal and infant outcomes. Maternal diet is one modifiable factor that can impact inflammation. Omega-3 and -6 fatty acids obtained through the diet are metabolized into bioactive compounds that effect inflammation. Recent evidence has shown that the downstream products of omega-3 and -6 fatty acids may influence physiology during pregnancy. In this review, the current knowledge relating to omega-3 and omega-6 metabolites during pregnancy will be summarized.

Feeding mice a diet high in oxidized linoleic acid metabolites does not alter liver oxylipin concentrations

The oxidation of dietary linoleic acid (LA) produces oxidized LA metabolites (OXLAMs) known to regulate multiple signaling pathways in vivo. Recently, we reported that feeding OXLAMs to mice resulted in liver inflammation and apoptosis. However, it is not known whether this is due to a direct effect of OXLAMs accumulating in the liver, or to their degradation into bioactive shorter chain molecules (e.g. aldehydes) that can provoke inflammation and related cascades. To address this question, mice were fed a low or high LA diet low in OXLAMs, or a low LA diet supplemented with OXLAMs from heated corn oil (high OXLAM diet). Unesterified oxidized fatty acids (i.e. oxylipins), including OXLAMs, were measured in liver after 8 weeks of dietary intervention using ultra-high pressure liquid chromatography coupled to tandem mass-spectrometry. The high OXLAM diet did not alter liver oxylipin concentrations compared to the low LA diet low in OXLAMs. Significant increases in several omega-6 derived oxylipins and reductions in omega-3 derived oxylipins were observed in the high LA dietary group compared to the low LA group. Our findings suggest that dietary OXLAMs do not accumulate in liver, and likely exert pro-inflammatory and pro-apoptotic effects via downstream secondary metabolites.

Modern Methods of Sample Preparation for the Analysis of Oxylipins in Biological Samples

Oxylipins are potent lipid mediators derived from polyunsaturated fatty acids, which play important roles in various biological processes. Being important regulators and/or markers of a wide range of normal and pathological processes, oxylipins are becoming a popular subject of research; however, the low stability and often very low concentration of oxylipins in samples are a significant challenge for authors and continuous improvement is required in both the extraction and analysis techniques. In recent years, the study of oxylipins has been directly related to the development of new technological platforms based on mass spectrometry (LC–MS/MS and gas chromatography–mass spectrometry (GC–MS)/MS), as well as the improvement in methods for the extraction of oxylipins from biological samples. In this review, we systematize and compare information on sample preparation procedures, including solid-phase extraction, liquid–liquid extraction from different biological tissues.

Advances in Our Understanding of Oxylipins Derived from Dietary PUFAs

Oxylipins formed from polyunsaturated fatty acids (PUFAs) are the main mediators of PUFA effects in the body. They are formed via cyclooxygenase, lipoxygenase, and cytochrome P450 pathways, resulting in the formation of prostaglandins, thromboxanes, mono-, di-, and tri-hydroxy fatty acids (FAs), epoxy FAs, lipoxins, eoxins, hepoxilins, resolvins, protectins (also called neuroprotectins in the brain), and maresins. In addition to the well-known eicosanoids derived from arachidonic acid, recent developments in lipidomic methodologies have raised awareness of and interest in the large number of oxylipins formed from other PUFAs, including those from the essential FAs and the longer-chain n-3 (ω-3) PUFAs. Oxylipins have essential roles in normal physiology and function, but can also have detrimental effects. Compared with the oxylipins derived from n-3 PUFAs, oxylipins from n-6 PUFAs generally have greater activity and more inflammatory, vasoconstrictory, and proliferative effects, although there are notable exceptions. Because PUFA composition does not necessarily reflect oxylipin composition, comprehensive analysis of the oxylipin profile is necessary to understand the overall physiologic effects of PUFAs mediated through their oxylipins. These analyses should include oxylipins derived from linoleic and α-linolenic acids, because these largely unexplored bioactive oxylipins constitute more than one-half of oxylipins present in tissues. Because collated information on oxylipins formed from different PUFAs is currently unavailable, this review provides a detailed compilation of the main oxylipins formed from PUFAs and describes their functions. Much remains to be elucidated in this emerging field, including the discovery of more oxylipins, and the understanding of the differing biological potencies, kinetics, and isomer-specific activities of these novel PUFA metabolites.

Frataxin deficiency increases cyclooxygenase 2 and prostaglandins in cell and animal models of Friedreich's ataxia

An inherited deficiency of the mitochondrial protein frataxin causes Friedreich's ataxia (FRDA); the mechanism by which this deficiency triggers neuro- and cardio-degeneration is unclear. Microarrays of neural tissue of animal models of the disease showed decreases in antioxidant genes, and increases in inflammatory genes. Cyclooxygenase (COX)-derived oxylipins are important mediators of inflammation. We measured oxylipin levels using tandem mass spectrometry and ELISAs in multiple cell and animal models of FRDA. Mass spectrometry revealed increases in concentrations of prostaglandins, thromboxane B2, 15-HETE and 11-HETE in cerebellar samples of knockin knockout mice. One possible explanation for the elevated oxylipins is that frataxin deficiency results in increased COX activity. While constitutive COX1 was unchanged, inducible COX2 expression was elevated over 1.35-fold (P < 0.05) in two Friedreich's mouse models and Friedreich's lymphocytes. Consistent with higher COX2 expression, its activity was also increased by 58% over controls. COX2 expression is driven by multiple transcription factors, including activator protein 1 and cAMP response element-binding protein, both of which were elevated over 1.52-fold in cerebella. Taken together, the results support the hypothesis that reduced expression of frataxin leads to elevation of COX2-mediated oxylipin synthesis stimulated by increases in transcription factors that respond to increased reactive oxygen species. These findings support a neuroinflammatory mechanism in FRDA, which has both pathomechanistic and therapeutic implications.

PPARgamma-dependent effects of conjugated linoleic acid on the human glioblastoma cell line (ADF)

Conjugated linoleic acid (CLA) has been shown to exert beneficial effects against carcinogenesis, atherosclerosis and diabetes. It has been demonstrated that CLA modulates lipid metabolism through the activation of peroxisome proliferator-activated receptors (PPARs). The PPAR family comprises 3 closely related gene products, PPAR alpha, beta/delta and gamma, differing for tissue distribution, developmental expression and ligand specificity. It has also been demonstrated that activated PPARgamma results in growth inhibition and differentiation of transformed cells. These observations stimulated a great interest toward PPARgamma ligands as potential anticancer drugs to be used in a differentiation therapy. Glioblastomas are the most commonly diagnosed primary tumors of the brain in humans. The prognosis of patients with high-grade gliomas is poor and only marginally improved by chemotherapy. The aim of this work was to study the effects of CLA and of a specific synthetic PPARgamma ligand on cell growth, differentiation and death of a human glioblastoma cell line as well as on parameters responsible for the metastatic behavior of this tumor. We demonstrate here that CLA and PPARgamma agonist strongly inhibit cell growth and proliferation rate and induce apoptosis. Moreover, both treatments decrease cell migration and invasiveness. The results obtained show that CLA acts, directly or indirectly, as a PPARgamma activator, strongly suggesting that this naturally occurring fatty acid may be used as brain antitumor drug and as a chemopreventive agent. Moreover, the gamma-agonist, once experimented and validated on man, may represent a useful coadjuvant in glioblastoma therapy and in the prevention of recurrences.

Suppression of cyclooxygenase-2 overexpression by 15S-hydroxyeicosatrienoic acid in androgen-dependent prostatic adenocarcinoma cells

Emerging reports now implicate alterations of arachidonic acid (AA) metabolism with prostate carcinogenesis. To test this hypothesis, androgen-primed benign hyperplastic (BHC) and malignant tumorigenic (MTC) cells derived from the Lobund-Wistar rat model of autochthonous prostate adenocarcinoma were incubated with (14)C-AA. Our data using MTCs revealed enhanced dual metabolism of (14)C-AA via COX to generate increased PGE(2) and via 5-lipoxygenase (LOX) to generate increased 5S-HETE in tumorigenic cells. Western blot of MTCs revealed upregulation of COX-2 expression. This paralleled the increased biosynthesis of PGE(2). Since some polyunsaturated fatty acids have been reported to modulate AA metabolism and tumorigenesis, we primed the cells with either gamma-linolenic acid (GLA) or its in vivo metabolite, 15S-HETrE, prior to incubation with AA. Our data revealed suppression of COX-2 expression/PGE(2) biosynthesis. In parallel, priming cells with 15S-HETrE resulted in greater suppression of COX-2 expression/PGE(2) biosynthesis. These findings suggest that 15S-HETrE could function in vivo after dietary intake of GLA to suppress DHT-enhanced prostatic COX-2 expression/PGE(2) biosynthesis and, thus, alleviate tumor growth and progression.

The traditional diet of Greece and cancer

The term 'Mediterranean diet', implying that all Mediterranean people have the same diet, is a misnomer. The countries around the Mediterranean basin have different diets, religions and cultures. Their diets differ in the amount of total fat, olive oil, type of meat, wine, milk, cheese, fruits and vegetables; and the rates of coronary heart disease and cancer, with the lower death rates and longer life expectancy occurring in Greece. The diet of Crete represents the traditional diet of Greece prior to 1960. Analyses of the dietary pattern of the diet of Crete shows a number of protective substances, such as selenium, glutathione, a balanced ratio of n-6/n-3 essential fatty acids (EFA), high amounts of fibre, antioxidants (especially resveratrol from wine and polyphenols from olive oil), vitamins E and C, some of which have been shown to be associated with lower risk of cancer, including cancer of the breast. Epidemiological studies and animal experiments indicate that n-3 fatty acids exert protective effects against some common cancers, especially cancers of the breast, colon and prostate. Many mechanisms are involved, including suppression of neoplastic transformation, cell growth inhibition, and enhanced apoptosis and anti-angiogenicity, through the inhibition of eicosanoid production from n-6 fatty acids; and suppression of cyclooxygenase 2 (COX-2), interleukin 1 (IL-1) and IL-6 gene expression by n-3 fatty acids. Recent intervention studies in breast cancer patients indicate that n-3 fatty acids, and docosahexaenoic acid (DHA) in particular, increase the response to chemopreventive agents. In patients with colorectal cancer, eicosapentaenoic acid (EPA) and DHA decrease cell proliferation, and modulate favourably the balance between colonic cell proliferation and apoptosis. These findings should serve as a strong incentive for the initiation of intervention trials that will test the effect of specific dietary patterns in the prevention and management of patients with cancer.

Regional biosynthesis of prostaglandins and hydroxyeicosatetraenoic acids from arachidonic acid in the rat stomach tissue

The present study was conducted to determine regional differences in the biosynthesis of prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs) in the rat stomach tissue (fundus, corpus and pyloric antrum) from radioactive arachidonic acid (AA). The radioactive metabolites were validated by RP-HPLC using non-radioactive AA as substrate. PGE(2) was the major prostanoid in the tissue(.) The relative ratio of PGE(2):PGF(2)alpha:PGD(2) in the whole stomach was 1:0.5:0.1. Regionally, the fundus biosynthesized the largest amount of all three cyclo-oxygenase products. Among the lipoxygenase metabolites, 15S-HETE was the predominant product, while 12S-HETE was found to be the lowest. The relative ratio of 15S-HETE:5S-HETE:12S-HETE in the whole stomach was 1:0.6:0.4. Interestingly, the generation of lipoxygenase products was the highest in the pyloric antrum when compared to fundus or corpus. Thus, the regional differences in the biosyntheses of gastric PGs and monohydroxy fatty acids may be relevant to our understanding of corresponding differences in mucosal resistance or susceptibility to gastric disease.

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.

Polyunsaturated fatty acids (PUFA) and eicosanoids in human health and pathologies

Linoleic and alpha-linolenic acids, obtained from plant material in the diet are the precursors in tissues of two families with opposing effects which are referred to as "essential fatty acids" (EFA): arachidonic acid (AA) and pentaene (eicosapentaenoic acid: EPA) and hexaene (docosahexaenoic acid: DHA) acids. The role of EFA is crucial, without a source of AA or compounds which can be converted into AA, synthesis of prostaglandins (PGs) by a cyclooxygenase (COX) enzyme would be compromised, and this would seriously affect many normal metabolic processes. COX, also known as prostaglandin endoperoxide synthase (Pghs) or as prostaglandin G/H synthase, is a key membrane bound enzyme responsible for the oxidation of AA to PGs. Two COX isoforms have been identified, COX-1 and COX-2 that form PGH2, a common precursor for the biosynthesis of thromboxane A2 (TxA2), prostacyclin (PGI2) and PGs (PGD2, PGE2, PGF2alpha. COX-1 enzyme is expressed constitutively in most cells and tissues. Its expression remains constant under either physiological or pathological conditions controlling synthesis of those PGs primarily involved in the regulation of homeostatic functions. In contrast, COX-2 is an intermediate response gene that encodes a 71-kDa protein. COX-2 is normally absent from most cells but highly inducible in certain cells in response to inflammatory stimuli resulting in enhanced PG release. PGs formed by COX-2 primarily mediate pain and inflammation but have multiple effects that can favour tumorigenesis. They are more abundant in cancers than in normal tissues from which the cancers arise. COX-2 is a participant in the pathway of colon carcinogenesis, especially when mutation of the APC (Adenomatous Polyposis Coli) tumour suppressor gene is the initiating event. In addition, COX-2 up-regulation and elevated PGE2 levels are involved in breast carcinogenesis. It seems that there is a correlation between COX-2 level of expression and the size of the tumours and their propensity to invade underlying tissue. Inhibition by non-steroidal anti-inflammatory drugs (NSAIDs) of COX enzymes which significantly suppress PGE2 levels, reduced breast cancer incidence and protected against colorectal cancer. Therefore it is suggested that consumption of a diet enriched in n-3 PUFA (specifically EPA and DHA) and inhibition of COX-2 by NSAIDs may confer cardioprotective effects and provide a significant mechanism for the prevention and treatment of human cancers.

Fatty acid oxidation and signaling in apoptosis

It is well established that fatty acid metabolites of cyclooxygenase, lipoxygenase (LOX), and cytochrome P450 are implicated in essential aspects of cellular signaling including the induction of programmed cell death. Here we review the roles of enzymatic and non-enzymatic products of polyunsaturated fatty acids in controlling cell growth and apoptosis. Also, the spontaneous oxidation of polyunsaturated fatty acids yields reactive aldehydes and other products of lipid peroxidation that are potentially toxic to cells and may also signal apoptosis. Significant conflicting data in terms of the role of LOX enzymes are highlighted, prompting a re-evaluation of the relationship between LOX and prostate cancer cell survival. We include new data showing that LNCaP, PC3, and Du145 cells express much lower levels of 5-LOX mRNA and protein compared with normal prostate epithelial cells (NHP2) and primary prostate carcinoma cells (TP1). Although the 5-LOX activating protein inhibitor MK886 killed these cells, another 5-LOX inhibitor AA861 hardly showed any effect. These observations suggest that 5-LOX is unlikely to be a prostate cancer cell survival factor, implying that the mechanisms by which LOX inhibitors induce apoptosis are more complex than expected. This review also suggests several mechanisms involving peroxisome proliferator activated receptor activation, BCL proteins, thiol regulation, and mitochondrial and kinase signaling by which cell death may be produced in response to changes in non-esterified and non-protein bound fatty acid levels. Overall, this review provides a context within which the effects of fatty acids and fatty acid oxidation products on signal transduction pathways, particularly those involved in apoptosis, can be considered in terms of their overall importance relative to the much better studied protein or peptide signaling factors.

The Mediterranean diets: What is so special about the diet of Greece? The scientific evidence

The term "Mediterranean diet," implying that all Mediterranean people have the same diet, is a misnomer. The countries around the Mediterranean basin have different diets, religions and cultures. Their diets differ in the amount of total fat, olive oil, type of meat and wine intake; milk vs. cheese; fruits and vegetables; and the rates of coronary heart disease and cancer, with the lower death rates and longer life expectancy occurring in Greece. Extensive studies on the traditional diet of Greece (the diet before 1960) indicate that the dietary pattern of Greeks consists of a high intake of fruits, vegetables (particularly wild plants), nuts and cereals mostly in the form of sourdough bread rather than pasta; more olive oil and olives; less milk but more cheese; more fish; less meat; and moderate amounts of wine, more so than other Mediterranean countries. Analyses of the dietary pattern of the diet of Crete shows a number of protective substances, such as selenium, glutathione, a balanced ratio of (n-6):(n-3) essential fatty acids (EFA), high amounts of fiber, antioxidants (especially resveratrol from wine and polyphenols from olive oil), vitamins E and C, some of which have been shown to be associated with lower risk of cancer, including cancer of the breast. These findings should serve as a strong incentive for the initiation of intervention trials that will test the effect of specific dietary patterns in the prevention and management of patients with cancer.