Lipoxins as biomarkers of lupus and other inflammatory conditions

Can lipid mediators and free fatty acids guide acute coronary syndrome diagnosis and treatment?

OBJECTIVE

The aim of this study was to investigate fatty acids, lipid mediator levels, and the desaturase index rates on different acute coronary syndrome types and their possible relationship with routine lipid parameters.

METHODS

The study included 81 patients with myocardial infarction (MI), 20 patients with unstable angina pectoris, and 31 healthy people. Fatty acids, CD59, lipoxin A4, 8-isoprostane, serum lipids, albumin, C-reactive protein (CRP), and high sensitive troponin levels were measured in all participants.

RESULTS

When the fatty acid groups were evaluated as a ratio of albumin, MUFA/albumin and SFA/albumin ratios were significantly higher in the MI group compared to the control group. Although CD59 and lipoxin A4 levels were higher in the control group, there was no significant differences between the groups. When lipoxin A4/CRP and CD59/CRP ratios were evaluated, the results were significantly lower than those in the control group.

CONCLUSION

Lipid mediators may be useful in treating atherosclerosis by contributing to the resolution of inflammation.

Disrupted balance between pro-inflammatory lipid mediators and anti-inflammatory specialized pro-resolving mediators is linked to hyperinflammation in patients with alcoholic hepatitis

Background

Chronic excessive alcohol consumption leads to a spectrum of alcohol-associated liver diseases (ALD), including alcoholic hepatitis (AH). AH is characterized by intense systemic and liver inflammation, posing significant risks of health complications and mortality. While inflammation is a crucial defense mechanism against injury and infection, its timely resolution is essential to prevent tissue damage and restore tissue homeostasis. The resolution of inflammation is an actively regulated process, primarily governed by specialized pro-resolving mediators (SPMs), lipid metabolites derived from ω-6 and ω-3 poly-unsaturated fatty acids (PUFAs). We investigated the balance between pro-inflammatory lipid mediators (PLMs) and SPMs in the ω-6 and ω-3 PUFA metabolic pathways and examined the impact of alcohol abstinence on rectifying the dysregulated biosynthesis of PLMs and SPMs in AH patients.

Methods

LC-MS/MS and ELISA were used to quantify levels of bioactive lipid mediators (LMs) and their precursors in the plasma samples from 58 AH patients, 29 heavy drinkers without overt liver diseases (HDCs), and 35 healthy controls (HCs). Subsequently, we assessed correlations of altered LMs with clinical parameters and various markers of inflammatory cascade andmicrobial translocation. Furthermore, we conducted a longitudinal study to track changes in levels of LMs over 6- and 12-month follow-ups in AH patients who underwent alcohol abstinence.

Results

AH patients exhibited significantly higher plasma levels of ω-6 PLMs (PGD 2 and LTB 4 ) and SPM RvE1 compared to HDCs and/or HCs. Conversely, key SPMs such as LXA4, RvD1, and several precursors in the ω-3 pathway were significantly downregulated in AH patients. Some of these altered LMs were found to correlate with AH disease severity, clinical parameters, and various inflammatory cytokines. In particular, the LTB4/LXA4 ratio was substantially elevated in AH patients relative to HDCs and HCs. This altered ratio displayed a positive correlation with the MELD score, suggesting its potential utility as an indicator of disease severity in AH patients. Importantly, the majority of dysregulated LMs, particularly PLMs, were normalized following alcohol abstinence.

Conclusion

Our study reveals significant dysregulation in the levels of PLM metabolites and anti-inflammatory SPMs in both ω-6 and ω-3 PUFA pathways in AH patients. This disrupted biosynthesis, characterized by an overabundance of PLMs and a deficiency in SPMs, is linked to the heightened inflammation observed in AH patients. Importantly, our findings suggest an important role of alcohol abstinence in restoring the balance of these LMs and the potential therapeutic benefits of SPM supplements in alleviating the inflammatory cascade in AH patients.

Lipoxins and their relationship with inflammation-associated diseases. A systematic review

AIM

To determine the relationship of lipoxin levels with inflammation and disease development in adults and children.

METHODS

We conducted a systematic review. The search strategy included Medline, Ovid, EMBASE, LILACS, The Cochrane Central Register of Controlled Trials, and Open Gray. We included Clinical trials, cohort studies, case-control studies, and cross-sectional studies. Animal experiments were excluded.

RESULTS

We included fourteen studies in this review, nine consistently showing decreased lipoxin levels and anti-inflammatory markers or increased pro-inflammatory markers in cardiovascular disease, metabolic syndrome, Alzheimer's disease, periodontitis, or autism. Five studies showed increased lipoxin levels and pro-inflammatory markers in pre-eclampsia, asthma, and coronary disease. On the other hand, one showed increased lipoxin levels and decreased pro-inflammatory marker levels.

CONCLUSIONS

Decreases in lipoxins are associated with developing pathologies such as cardiovascular and neurological diseases, indicating that lipoxins protect against these pathologies. However, in other pathologies, such as asthma, pre-eclampsia, and periodontitis, which are associated with chronic inflammation despite increased levels of LXA4, the increase in inflammation suggests a possible failure of this regulatory pathway. Therefore, further studies are necessary to evaluate the role of LXA4 in the pathogenesis of inflammatory diseases.

Association between 19 dietary fatty acids intake and rheumatoid arthritis: Results of a nationwide survey

BACKGROUND

The relationship between dietary fatty acid intakes and rheumatoid arthritis (RA) is unclear and the available studies have focused on only a few fatty acids. This study investigated the association between the intake of 19 dietary fatty acids and RA in U.S. adults.

METHODS

This cross-sectional study using nationally representative data from the 2010-2020 National Health and Nutrition Examination Survey (NHANES). Multivariate linear regression model, multivariate logic regression models, smoothing curve fitting, and two-segment linear regression model were used to explore the relationships between 19 dietary fatty acids intakes with high-sensitivity C-reactive protein (Hs-CRP) and RA risk.

RESULTS

A total of 16,530 participants were included (1053 participants with RA). Intake of hexadecanoic acid and octadecanoic acid were significantly associated with higher Hs-CRP levels, intake of hexadecenoic acid was significantly associated with higher RA risk, and intake of docosahexaenoic acid was significantly associated with lower RA risk. In addition, there was an inverted U-shaped relationship between total monounsaturated fatty acids (MUFAs) intake and RA risk, with the inflection point reached at 15.77% .

CONCLUSIONS

Among the 19 dietary fatty acids, only 4 subclasses were significantly associated with Hs-CRP or RA risk. The inverted U-shaped relationship between MUFAs and RA risk may provide insights to find potential prevention strategies for RA.

Fish oil supplementation in patients with and without systemic lupus erythematosus: targeting pro-inflammatory and pro-resolving lipid mediators

Background:

Omega-3 fatty acid-derived “specialized pro-resolving mediators” are lipid mediators (LM) central to inflammation resolution. We investigated whether fish oil (FO) supplementation was associated with pro-inflammatory and pro-resolving LM levels in SLE patients compared to matched non-SLE controls.

Methods:

16 SLE patients taking FO were matched (age, sex, race) to 16 non-SLE controls taking FO. Another 16 SLE patients not taking FO were matched to 16 non-SLE patients not taking FO. Demographic/clinical data were obtained by medical record review. Targeted liquid chromatography-tandem spectrometry was performed with plasma to quantify 27 LM. Multivariable linear analyses examined how SLE, FO, and their interaction were associated with LM levels, adjusting for potential confounders including inflammatory markers and SLE disease activity for SLE cases only.

Results:

Higher levels of pro-inflammatory LMs were found in patients with SLE not on FO, compared to controls not on FO, particularly TXB₂ (p=0.03). Lower levels of many SPMs were observed among patients with SLE taking FO compared to controls taking FO, including LXB₄ (p<0.01) and 18-HEPE (p=0.04). In case-only analyses, taking FO was associated with higher 17-HDHA levels (p=0.05). There were no multiplicative interactions between FO effect and SLE status, and after adjustment for multiple comparisons, few of the associations persisted.

Conclusion:

In this cross-sectional exploratory study, higher levels of inflammatory LM and lower levels of SPMs were found in SLE patients than controls, among those taking and not taking FO. Further studies investigating the potentially beneficial biologic effects of FO preparations and doses in SLE are needed.

Baseline Elevations of Leukotriene Metabolites and Altered Plasmalogens Are Prognostic Biomarkers of Plaque Progression in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is associated with an increased incidence of acute and chronic cardiovascular disease as compared to the general population. This study uses a comprehensive metabolomic screen of baseline sera from lupus patients to identify metabolites that predict future carotid plaque progression, following 8–9 years of follow-up. Nine patients had SLE without plaque progression, 8 had SLE and went on to develop atherosclerotic plaques (SLE^PP), and 8 patients were controls who did not have SLE. The arachidonic acid pathway metabolites, leukotriene B4 (LTB4) and 5-hydroxyeicosatetraenoic acid (5-HETE), and the oxidized lipids 9/13-hydroxyoctodecadienoic acid (HODE) were found to be significantly altered (p < 0.05 and fold-change >2) in SLE^PP patients compared to SLE patients without plaque progression. SLE^PP patients also exhibited significantly altered levels of branched chain amino acid (BCAA) metabolites and plasmalogens compared to the non-SLE controls. Taken together with the rich literature on these metabolites, these findings suggest that the identified metabolites may not only be prognostic of cardiovascular disease development in SLE patients, but they may also be active drivers of atheroma formation. Early identification of these high risk SLE patients may help institute preventive measures early in the disease course.

Effects of 15-Lipoxygenase Overexpressing Adipose Tissue Mesenchymal Stem Cells on The Th17 / Treg Plasticity

15-lipoxygenase (15-LOX) is a critical enzyme that allows the direction of arachidonic acid metabolism to change from inflammation into the resolution. This study aims to reveal how the immunomodulation properties of mesenchymal stem cells (MSC) alter by the 15-LOX overexpression. For this purpose, peripheral blood mononuclear cells (PBMCs) isolated from seven healthy volunteers, and both MSCs and 15-LOX overexpressing MSCs (^15-LOXMSCs) were co-cultured at different cell ratios (1/1, 1/5 and 1/10). Alterations of CD4⁺Tbet⁺, CD4⁺Gata3⁺, CD4⁺RoRC2⁺, and CD4⁺FoxP3⁺ lymphocyte frequencies were detected by flow cytometry, and IFN-γ, IL-4, IL-6, IL-10, IL-17a, TGF-β and LXA₄ levels of medium supernatants were measured by ELISA method. According to our findings, MSC and ^15-LOXMSCs have a suppressive effect on PHA activated PBMCs. However, as the ratio of PBMCs increased, the effects of ^15-LOXMSCs increased significantly, while the effects of MSCs decreased. The most notable effect of the 15-LOX modification was the significant reduction in IL-6, IL-10 and IL-17a expression and the accompanying increase in TGF-β and LXA₄ levels. We also observed a similar situation between CD4⁺RoRC2⁺ and CD4⁺FoxP3⁺ cell frequencies. These data suggested that the effects of MSCs on the balance of Th17 / Treg could change by the 15-LOX overexpression, and this might be in favor of the Treg cells.

Low LXA4, RvD1 and RvE1 levels may be an indicator of the development of hypertension

Vascular structure and integrity are at the forefront of blood pressure regulation. However, there are many factors that affect the responses of the vessels. One of these is the inflammatory processes associated with high cholesterol and its modification. 15-lipoxygenase (15-LOX) is the critical enzyme in cholesterol oxidation, but this enzyme is also responsible for the synthesis of specialized proresoving lipid mediators (SPMs) called Lipoxin (Lxs) and Resolvin (Rvs). In this study, we determined serum LXA4, RvD1 and RvE1 levels in newly diagnosed hypertension (HT) and normotension (NT) cases. We evaluated how the presence of hypercholesterolemia (HC) in the follow-up changes the levels of these SPMs. We found that the three SPMs we measured decreased significantly in the presence of HC. In addition, we found a negative and significant correlation with systolic blood pressure and total cholesterol levels for the three SPMs. In conclusion, HT and HC are independent risk factors for cardiovascular death. However, the presence of HC may be an important factor for the development of HT. Increasing cholesterol levels may cause 15-LOX to shift towards LDL oxidation, thus leading to inflammation. This situation may negatively affect the vascular functions in the regulation of blood pressure. Serum LXA4, RvD1 and RvE1 measurements may provide clues that represent a shift of 15-LOX enzyme activity towards cholesterol.

The Role of IL-36 in the Pathophysiological Processes of Autoimmune Diseases

A member of the interleukin (IL)-1 superfamily was IL-36, which contained IL-36α, IL-36β, IL-36γ, and IL-36Ra. Heterotrimer complexes, consisting of heterodimeric receptor complexes and IL-36 agonist, gave signals through intracellular functional domains, so as to bind to downstream proteins and induce inflammatory response. IL-36 agonists upregulated mature-associated CD80, CD86, MHCII, and inductively produced several pro-inflammatory cytokines through the IL-36R-dependent manner in dendritic cells (DCs). Besides, DCs had the ability to initiate the differentiation of helper T (Th) cells. Up to date, the role of IL-36 in immunity, inflammation and other diseases is of great importance. Additionally, autoimmune diseases were characterized by excessive immune response, resulting in damage and dysfunction of specific or multiple organs and tissues. Most autoimmune diseases were related to inflammatory response. In this review, we will conclude the recent research advances of IL-36 in the occurrence and development of autoimmune diseases, which may provide new insight for the future research and the treatment of these diseases.

NAP1051, a Lipoxin A4 Biomimetic Analogue, Demonstrates Antitumor Activity Against the Tumor Microenvironment

Resolving tumor-associated inflammation in the tumor microenvironment (TME) may promote antitumor effects. Lipoxin A4 (LXA4) is a short-lived endogenous bioactive lipid with potent anti-inflammatory and pro-resolving properties. Here, a biomimetic of LXA4, NAP1051, was shown to have LXA4-like in vitro properties and antitumor activity in colorectal cancer xenograft models. NAP1051 inhibited neutrophil chemotaxis toward fMLP and dose-dependently promoted dTHP-1 efferocytosis which was equipotent to aspirin-triggered lipoxin A4 (ATLA). In dTHP-1 cells, NAP1051 induced strong phosphorylation on ERK1/2 and AKT similar to formyl peptide receptor 2 (FPR2/ALX) agonists. In two mouse xenograft colorectal cancer models, NAP1051 significantly inhibited tumor growth when given orally at 4.8 to 5 mg/kg/day. Flow cytometric analyses showed that NAP1051 reduced splenic and intratumoral neutrophil and myeloid-derived suppressor cell populations, which correlated to the antitumor effect. In addition, NAP1051 reduced NETosis in the TME while stimulating T-cell recruitment. Overall, these results show that NAP1051 possesses key lipoxin-like properties and has antitumor activity against colorectal cancer via modulation of neutrophils and NETosis in the TME.

Role of the Specialized Pro-resolving Mediator Resolvin D1 in Hashimoto's Thyroiditis

OBJECTIVE

Resolvins are produced by the catabolism of polyunsaturated fatty acids (PUFAs) and play vital roles in inflammation resolution. Resolvins have been associated with autoimmune disorders. This study aimed to measure the level of Resolvin D1 (RVD1) in the serum of Hashimoto's thyroiditis (HT) patients and healthy controls (HCs) and to further analyse its correlation with thyroid autoantibodies and inflammatory factors.

METHODS

Sixty-three participants were recruited, namely, 30 untreated HT patients and 33 sex- and age-matched HCs. Serum RVD1 and inflammatory chemokine (MCP-1 and IP-10) levels were measured by ELISA according to the manufacturer's protocol. Serum total T3 (TT3), TT4, free T3 (FT3), FT4, thyroglobulin antibody (TgAb), thyroid peroxidase antibody (TPOAb) and thyroid-stimulating hormone (TSH) levels were measured using an electrochemiluminescence immunoassay. Thyroid homeostasis parameters, including the thyroid secretory capacity (SPINA-GT), the total deiodinase activity (SPINA-GD), Jostel's TSH index (TSHI) and the thyrotroph thyroid hormone sensitivity index (TTSI), were calculated.

RESULTS

Serum RVD1 levels in HT patients (134.76, 85.35-201.36 pg/mL) were significantly lower than those in HCs (187.64, 131.01-326.85 pg/mL) (P=0.004). As the TPOAb level increased, the RVD1 level showed a decreasing trend (P for trend=0.002). Both multinomial and ordinal logistics analyses revealed that serum RVD1 levels were negatively correlated with TPOAb levels in the adjusted models. Moreover, RVD1 showed a negative correlation with the inflammatory chemokine IP-1 0 (r=-0.276, P=0.034), TSHI (r=-0.269, P=0.036) and TTSI (r=-0.277, P=0.031).

CONCLUSIONS

Thyroid autoimmunity may be associated with low levels of RVD1. Decreased RVD1 levels indicate impaired resolution of inflammation in HT patients.

Resolution-Based Therapies: The Potential of Lipoxins to Treat Human Diseases

Inflammation is an a physiological response instead an essential response of the organism to injury and its adequate resolution is essential to restore homeostasis. However, defective resolution can be the precursor of severe forms of chronic inflammation and fibrosis. Nowadays, it is known that an excessive inflammatory response underlies the most prevalent human pathologies worldwide. Therefore, great biomedical research efforts have been driven toward discovering new strategies to promote the resolution of inflammation with fewer side-effects and more specificity than the available anti-inflammatory treatments. In this line, the use of endogenous specialized pro-resolving mediators (SPMs) has gained a prominent interest. Among the different SPMs described, lipoxins stand out as one of the most studied and their deficiency has been widely associated with a wide range of pathologies. In this review, we examined the current knowledge on the therapeutic potential of lipoxins to treat diseases characterized by a severe inflammatory background affecting main physiological systems, paying special attention to the signaling pathways involved. Altogether, we provide an updated overview of the evidence suggesting that increasing endogenously generated lipoxins may emerge as a new therapeutic approach to prevent and treat many of the most prevalent diseases underpinned by an increased inflammatory response.

Resolvins: Emerging Players in Autoimmune and Inflammatory Diseases

Resolvins, belonging to the group of specialized proresolving mediators (SPMs), are metabolic products of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) and are synthesized during the initial phases of acute inflammatory responses to promote the resolution of inflammation. Resolvins are produced for termination of neutrophil infiltration, stimulation of the clearance of apoptotic cells by macrophages, and promotion of tissue remodeling and homeostasis. Metabolic dysregulation due to either uncontrolled activity of pro-inflammatory responses or to inefficient resolution of inflammation results in chronic inflammation and may also lead to atherosclerosis or other chronic autoimmune diseases such as rheumatoid arthritis, psoriasis, systemic lupus erythematosus, vasculitis, inflammatory bowel diseases, and type 1 diabetes mellitus. The pathogenesis of such diseases involves a complex interplay between the immune system and, environmental factors (non-infectious or infectious), and critically depends on individual susceptibility to such factors. In the present review, resolvins and their roles in the resolution of inflammation, as well as the role of these mediators as potential therapeutic agents to counteract specific chronic autoimmune and inflammatory diseases are discussed.

A Systematic Review on the Role of Arachidonic Acid Pathway in Multiple Sclerosis

BACKGROUND & OBJECTIVE

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease characterized by destruction of oligodendrocytes, immune cell infiltration and demyelination. Inflammation plays a significant role in MS, and the inflammatory mediators such as eicosanoids, leukotrienes, superoxide radicals are involved in pro-inflammatory responses in MS. In this systematic review we tried to define and discuss all the findings of in vivo animal studies and human clinical trials on the potential association between arachidonic acid (AA) pathway and multiple sclerosis.

METHODS

A systematic literature search across Pubmed, Scopus, Embase and Cochrane database was conducted. This systematic review was performed according to PRISMA guidelines.

RESULTS

A total of 146 studies were included, of which 34 were conducted in animals, 58 in humans, and 60 studies reported the role of different compounds that target AA mediators or their corresponding enzymes/ receptors, and can have a therapeutic effect in MS. These results suggest that eicosanoids have significant roles in experimental autoimmune encephalomyelitis (EAE) and MS. The data from animal and human studies elucidated that PGI2, PGF2α, PGD2, isoprostanes, PGE2, PLA2, LTs are increased in MS. PLA2 inhibition modulates the progression of the disease. PGE1 analogues can be a useful option in the treatment of MS.

CONCLUSIONS

All studies reported the beneficial effects of COX and LOX inhibitors in MS. The hybrid compounds, such as COX-2 inhibitors/TP antagonists and 5-LOX inhibitors can be an innovative approach for multiple sclerosis treatment. Future work in MS should shed light in synthesizing new compounds targeting arachidonic acid pathway.

Bioactive lipids, inflammation and chronic diseases

Endogenous bioactive lipids are part of a complex network that modulates a plethora of cellular and molecular processes involved in health and disease, of which inflammation represents one of the most prominent examples. Inflammation serves as a well-conserved defence mechanism, triggered in the event of chemical, mechanical or microbial damage, that is meant to eradicate the source of damage and restore tissue function. However, excessive inflammatory signals, or impairment of pro-resolving/anti-inflammatory pathways leads to chronic inflammation, which is a hallmark of chronic pathologies. All main classes of endogenous bioactive lipids - namely eicosanoids, specialized pro-resolving lipid mediators, lysoglycerophopsholipids and endocannabinoids - have been consistently involved in the chronic inflammation that characterises pathologies such as cancer, diabetes, atherosclerosis, asthma, as well as autoimmune and neurodegenerative disorders and inflammatory bowel diseases. This review gathers the current knowledge concerning the involvement of endogenous bioactive lipids in the pathogenic processes of chronic inflammatory pathologies.

Bioactive Lipids in Age-Related Disorders

Our own studies and those of others have shown that defects in essential fatty acid (EFA) metabolism occurs in age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, immune dysfunction and cancer. It has been noted that in all these disorders there could occur a defect in the activities of desaturases, cyclo-oxygenase (COX), and lipoxygenase (LOX) enzymes leading to a decrease in the formation of their long-chain products gamma-linolenic acid (GLA), arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). This leads to an increase in the production of pro-inflammatory prostaglandin E2 (PGE2), thromboxanes (TXs), and leukotrienes (LTs) and a decrease in anti-inflammatory lipoxin A4, resolvins, protectins and maresins. All these bioactive molecules are termed as bioactive lipids (BALs). This imbalance in the metabolites of EFAs leads to low-grade systemic inflammation and at times acute inflammatory events at specific local sites that trigger the development of various age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, coronary heart disease, atherosclerosis, and immune dysfunction as seen in rheumatoid arthritis, lupus, nephritis and other localized inflammatory conditions. This evidence implies that methods designed to restore BALs to normal can prevent age-related disorders and enhance longevity and health.

HMGB1-C1q complexes regulate macrophage function by switching between leukotriene and specialized proresolving mediator biosynthesis

Macrophage polarization is critical to inflammation and resolution of inflammation. We previously showed that high-mobility group box 1 (HMGB1) can engage receptor for advanced glycation end product (RAGE) to direct monocytes to a proinflammatory phenotype characterized by production of type 1 IFN and proinflammatory cytokines. In contrast, HMGB1 plus C1q form a tetramolecular complex cross-linking RAGE and LAIR-1 and directing monocytes to an antiinflammatory phenotype. Lipid mediators, as well as cytokines, help establish a milieu favoring either inflammation or resolution of inflammation. This study focuses on the induction of lipid mediators by HMGB1 and HMGB1 plus C1q and their regulation of IRF5, a transcription factor critical for the induction and maintenance of proinflammatory macrophages. Here, we show that HMGB1 induces leukotriene production through a RAGE-dependent pathway, while HMGB1 plus C1q induces specialized proresolving lipid mediators lipoxin A4, resolvin D1, and resolvin D2 through a RAGE- and LAIR-1-dependent pathway. Leukotriene exposure contributes to induction of IRF5 in a positive-feedback loop. In contrast, resolvins (at 20 nM) block IRF5 induction and prevent the differentiation of inflammatory macrophages. Finally, we have generated a molecular mimic of HMGB1 plus C1q, which cross-links RAGE and LAIR-1 and polarizes monocytes to an antiinflammatory phenotype. These findings may provide a mechanism to control nonresolving inflammation in many pathologic conditions.

Arachidonic acid in health and disease with focus on hypertension and diabetes mellitus: A review

Arachidonic acid (AA 20:4n-6) is an essential component of cell membranes and modulates cell membrane fluidity. AA is metabolized by cyclo-oxygenase (COX), lipoxygenase (LOX) and cytochrome P450 enzymes to form several metabolites that have important biological actions. Of all the actions, role of AA in the regulation of blood pressure and its ability to prevent both type 1 and type 2 diabetes mellitus seems to be interesting. Studies showed that AA and its metabolites especially, lipoxin A4 (LXA4) and epoxyeicosatrienoic acids (EETs), potent anti-inflammatory metabolites, have a crucial role in the pathobiology of hypertension and diabetes mellitus. AA, LXA4 and EETs regulate smooth muscle function and proliferation, voltage gated ion channels, cell membrane fluidity, membrane receptors, G-coupled receptors, PPARs, free radical generation, nitric oxide formation, inflammation, and immune responses that, in turn, participate in the regulation blood pressure and pathogenesis of diabetes mellitus. In this review, role of AA and its metabolites LXA4 and EETs in the pathobiology of hypertension, pre-eclampsia and diabetes mellitus are discussed. Based on several lines of evidences, it is proposed that a combination of aspirin and AA could be of benefit in the prevention and management of hypertension, pre-eclampsia and diabetes mellitus.

Visceral fat adipocytes from obese and colorectal cancer subjects exhibit distinct secretory and ω6 polyunsaturated fatty acid profiles and deliver immunosuppressive signals to innate immunity cells

Obesity is a low-grade chronic inflammatory state representing an important risk factor for colorectal cancer (CRC). Adipocytes strongly contribute to inflammation by producing inflammatory mediators. In this study we investigated the role of human visceral fat adipocytes in regulating the functions of innate immunity cells. Adipocyte-conditioned media (ACM) from obese (n = 14) and CRC (lean, n = 14; obese, n = 13) subjects released higher levels of pro-inflammatory/immunoregulatory factors as compared to ACM from healthy lean subjects (n = 13). Dendritic cells (DC), differentiated in the presence of ACM from obese and CRC subjects, expressed elevated levels of the inhibitory molecules PD-L1 and PD-L2, and showed a reduced IL-12/IL-10 ratio in response to both TLR ligand- and γδ T lymphocyte-induced maturation. Furthermore, CRC patient-derived ACM inhibited DC-mediated γδ T cell activation. The immunosuppressive signals delivered by ACM from obese and CRC individuals were associated with a pro-inflammatory secretory and ω6 polyunsaturated fatty acid profile of adipocytes. Interestingly, STAT3 activation in adipocytes correlated with dihomo-γlinolenic acid content and was further induced by arachidonic acid, which conversely down-modulated PPARγ. These results provide novel evidence for a cross-talk between human adipocytes and innate immunity cells whose alteration in obesity and CRC may lead to immune dysfunctions, thus setting the basis for cancer development.

Differential action of polyunsaturated fatty acids and eicosanoids on bleomycin-induced cytotoxicity to neuroblastoma cells and lymphocytes

INTRODUCTION

This study was conducted to examine whether bleomycin-induced growth inhibitory action on human neuroblastoma cells (IMR-32) is influenced by anti-inflammatory metabolites of polyunsaturated fatty acids (PUFAs): lipoxin A4 (LXA4), resolvin D1 and protectin D1 in vitro.

MATERIAL AND METHODS

The in vitro study was conducted using monolayer cultures of exponentially growing IMR-32 cells. The effects of various PUFAs and eicosanoids and anti-inflammatory metabolites of PUFAs such as lipoxin A4 (LXA4), resolvin D1 and protectin D1 on the growth of IMR-32 cells and human lymphocytes in vitro were investigated. The potential of PUFAs, eicosanoids and LXA4, resolvin D1 and protectin D1 to modify the growth inhibitory effects of bleomycin was also studied in IMR-32 cells and human lymphocytes.

RESULTS

PUFAs inhibited the growth of IMR-32 cells (EPA > DHA = AA > GLA = ALA > DGLA = LA) significantly (p < 0.001) while prostaglandins were found to be not effective. Bleomycin-induced growth inhibitory action on IMR-32 cells was augmented by PUFAs and its metabolites (p < 0.05). PUFAs and LXA4 did not inhibit the growth of human lymphocytes and bleomycin-induced growth inhibitory action was also not enhanced by these bioactive lipids.

CONCLUSIONS

Bioactive lipids have differential action on normal human lymphocytes and tumor cells in vitro. The apparent lack of effect of PUFAs in combination with bleomycin on the growth of human lymphocytes in comparison to their growth inhibitory action on IMR-32 cells suggests that PUFAs can be used in combination with bleomycin to target tumor cells with little concern over this combination's effect on the growth of human lymphocytes. Further studies are warranted to evaluate these differential effects under in vivo conditions.

Deletion of 12/15-lipoxygenase accelerates the development of aging-associated and instability-induced osteoarthritis

OBJECTIVE

12/15-Lipoxygenase (12/15-LOX) catalyzes the generation of various anti-inflammatory lipid mediators, and has been implicated in several inflammatory and degenerative diseases. However, there is currently no evidence that 12/15-LOX has a role in osteoarthritis (OA). The aim of this study was to investigate the role of 12/15-LOX in the pathogenesis of OA.

METHODS

The development of aging-associated and destabilization of the medial meniscus (DMM)-induced OA were compared in 12/15-LOX-deficient (12/15-LOX-/-) and wild-type (WT) mice. The extent of cartilage damage was evaluated by histology. The expression of OA markers was evaluated by immunohistochemistry and RT-PCR. Cartilage explants were stimulated with IL-1α in the absence or presence of the 12/15-LOX metabolites, 15-hydroxyeicosatetraenoic acids (15-HETE), 13-hydroxyoctadecadienoic acid (13-HODE) or lipoxin A4 (LXA4), and the levels of matrix metalloproteinases-13 (MMP-13), Nitric oxide (NO) and prostaglandin E₂ (PGE₂) were determined. The effect of LXA4 on the progression of OA was evaluated in wild type (WT) mice.

RESULTS

The expression of 12/15-LOX in cartilage increased during the progression of DMM-induced OA and with aging in WT mice. Cartilage degeneration was more severe in 12/15-LOX-/- mice compared to WT mice in both models of OA, and this was associated with increased expression of MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs, aggrecanases (ADAMTS5), inducible NO synthases (iNOS), and mPGES-1. Treatment of cartilage explants with 12/15-LOX metabolites, suppressed IL-1α-induced production of MMP-13, NO and PGE₂, with LXA4 being the most potent. Intra-peritoneal injection of LXA4 reduced the severity of DMM-induced cartilage degradation.

CONCLUSIONS

These data suggest an important role of 12/15-LOX in the pathogenesis of OA. They also suggest that activation of this pathway may provide a novel strategy for prevention and treatment of OA.

Is There a Role for Bioactive Lipids in the Pathobiology of Diabetes Mellitus?

Inflammation, decreased levels of circulating endothelial nitric oxide (eNO) and brain-derived neurotrophic factor (BDNF), altered activity of hypothalamic neurotransmitters (including serotonin and vagal tone) and gut hormones, increased concentrations of free radicals, and imbalance in the levels of bioactive lipids and their pro- and anti-inflammatory metabolites have been suggested to play a role in diabetes mellitus (DM). Type 1 diabetes mellitus (type 1 DM) is due to autoimmune destruction of pancreatic β cells because of enhanced production of IL-6 and tumor necrosis factor-α (TNF-α) and other pro-inflammatory cytokines released by immunocytes infiltrating the pancreas in response to unknown exogenous and endogenous toxin(s). On the other hand, type 2 DM is due to increased peripheral insulin resistance secondary to enhanced production of IL-6 and TNF-α in response to high-fat and/or calorie-rich diet (rich in saturated and trans fats). Type 2 DM is also associated with significant alterations in the production and action of hypothalamic neurotransmitters, eNO, BDNF, free radicals, gut hormones, and vagus nerve activity. Thus, type 1 DM is because of excess production of pro-inflammatory cytokines close to β cells, whereas type 2 DM is due to excess of pro-inflammatory cytokines in the systemic circulation. Hence, methods designed to suppress excess production of pro-inflammatory cytokines may form a new approach to prevent both type 1 and type 2 DM. Roux-en-Y gastric bypass and similar surgeries ameliorate type 2 DM, partly by restoring to normal: gut hormones, hypothalamic neurotransmitters, eNO, vagal activity, gut microbiota, bioactive lipids, BDNF production in the gut and hypothalamus, concentrations of cytokines and free radicals that results in resetting glucose-stimulated insulin production by pancreatic β cells. Our recent studies suggested that bioactive lipids, such as arachidonic acid, eicosapentaneoic acid, and docosahexaenoic acid (which are unsaturated fatty acids) and their anti-inflammatory metabolites: lipoxin A4, resolvins, protectins, and maresins, may have antidiabetic actions. These bioactive lipids have anti-inflammatory actions, enhance eNO, BDNF production, restore hypothalamic dysfunction, enhance vagal tone, modulate production and action of ghrelin, leptin and adiponectin, and influence gut microbiota that may explain their antidiabetic action. These pieces of evidence suggest that methods designed to selectively deliver bioactive lipids to pancreatic β cells, gut, liver, and muscle may prevent type 1 and type 2 DM.

Diabetic macular edema, retinopathy and age-related macular degeneration as inflammatory conditions

Diabetic macular edema (DME) and diabetic retinopathy (DR) are complications affecting about 25% of all patients with long-standing type 1 and type 2 diabetes mellitus and are a major cause of significant decrease in vision and quality of life. Age-related macular degeneration (AMD) is not uncommon, and diabetes mellitus affects the incidence and progression of AMD through altering hemodynamics, increasing oxidative stress, accumulating advanced glycation end products, etc. Recent studies suggest that DME, DR and AMD are inflammatory conditions characterized by a breakdown of the blood-retinal barrier, inflammatory processes and an increase in vascular permeability. Key factors that seem to have a dominant role in DME, DR and AMD are angiotensin II, prostaglandins and the vascular endothelial growth factor and a deficiency of anti-inflammatory bioactive lipids. The imbalance between pro- and anti-inflammatory eicosanoids and enhanced production of pro-angiogenic factors may initiate the onset and progression of DME, DR and AMD. This implies that bioactive lipids that possess anti-inflammatory actions and suppress the production of angiogenic factors could be employed in the prevention and management of DME, DR and AMD.

An insight into the role of arachidonic acid derived lipid mediators in virus associated pathogenesis and malignancies

Several studies shed light on the size and diversity of the lipidome, along with its role in physiological and pathological processes in human health. Besides that, lipids also function as important signaling mediators. This review focuses on discussing the role of arachidonic acid (AA) derived lipids as mediators in diseases with special emphasis on viral infections. Structurally, arachidonic acid derived lipids, also referred to as lipid mediators, can be classified into three specific classes: Class 1-eicosanoids derived from arachidonic acid metabolism; Class 2-lysophospholipids consisting of either a glycerol or a sphingosine backbone; Class 3-AA and ω-3 polyunsaturated fatty acid (PUFA) derivatives. Class 1 and 2 lipids are commonly referred to as pro-inflammatory molecules, which are found upregulated in diseases like cancer and viral infection. Class 3 lipids are anti-inflammatory molecules, which could be potentially used in treatment of diseases associated with inflammation. The function of each class has been elucidated as unique and contributory to an overall cellular homeostasis. Current work in this field is promising and will surely usher in a new era of lipid understanding and control not only at the molecular level, but also in terms of holistic patient care.

Omega-3 fatty acids as an adjunct for periodontal therapy-a review

OBJECTIVES

The aim of this article is to present an overview of omega-3 fatty acids, their anti-inflammatory properties and potential use as an adjunct for periodontal therapy.

MATERIALS AND METHODS

A general literature search was conducted to provide an overview of omega-3 fatty acids, their metabolism and anti-inflammatory properties. A more specific literature search of PubMed and EMBASE was conducted to identify articles dealing studies investigating the effects of omega-3 fatty acids in the treatment of periodontitis in animals and humans and included cross-sectional, longitudinal and intervention designs.

RESULTS

To date, there is good emerging evidence that dietary supplementation with fish oil may be of some benefit and this is enhanced if combined with aspirin. All clinical intervention studies to date have been on small sample sizes, and this indicates there is need for larger and more robust clinical trials to verify these initial findings.

CONCLUSIONS

Dietary supplementation with fish oil could be a cost-effective adjunctive therapy to the management of periodontal disease.

CLINICAL RELEVANCE

The host modulatory properties of omega-3 fatty acids warrant further assessment of their use as an adjunct in the management of periodontitis.

Lipoxins exert antiangiogenic and anti-inflammatory effects on Kaposi's sarcoma cells

Lipoxin A4 (LXA4) is an endogenously produced host molecule with anti-inflammatory resolution effects. Previous studies demonstrated it to be involved in anti-vascular endothelial growth factor (VEGF)-mediated angiogenesis and in a possible anticancer role via interaction with its receptor, lipoxin A 4 receptor (ALXR). Here, we examined the effects of LXA4 and its epimer 15-epi-LXA4 in inhibiting proinflammatory and angiogenic functions in a human Kaposi's sarcoma tumor-derived cell line (KS-IMM). KS-IMM cells expressed increased levels of inflammatory cyclooxygenase 2 (COX-2) and 5-lipoxygenase (5-LO) pathway enzymes when compared with human microvascular dermal endothelial cells (HMVEC-d). KS-IMM cells secreted high levels of prostaglandin E2 (PGE2) and chemotactic leukotriene B4 (LTB4). Treatment with LXA4 or 15-epi-LXA4 effectively reduced the levels of COX-2, 5-LO proteins, and secretion of PGE2 and LTB4 in KS-IMM cells. LXA4 or 15-epi-LXA4 treatment also decreased secretion of proinflammatory interleukin 6 (IL-6) and IL-8 cytokines but induced the secretion of anti-inflammatory IL-10. LXA4 treatment reduced the phosphorylation of VEGF receptor (VEGFR) and ephrin family receptor tyrosine kinases. LXA4 treatment effectively induced dephosphorylation of multiple cellular kinases such as Focal Adhesion Kinase, Protein kinase B, nuclear factor kappa-light-chain-enhancer of activated B cells, and Extracellular signal-regulated kinases (ERK)1/2, and reduced angiogenic factor VEGF-C secretion in KS cells. LX treatment drastically induced the Src-homology 2 domain-containing phosphatase tyrosine (Y542) phosphatase and reduced VEGFR-2 phosphorylation at sites Y1059, Y1175, and Y1212. Treatment of KS-IMM cells with LXA4 resulted in selective localization of VEGFR-2 in nonlipid raft (non-LR) and ALXR to LR fractions. These results demonstrated that LXA4 or 15-epi-LXA4 induce anti-inflammatory and antiangiogenic effects in KS cells and suggest that treatment with LXs is an attractive novel strategy against KS.

Cytokines, angiogenic, and antiangiogenic factors and bioactive lipids in preeclampsia

Preeclampsia is a low-grade systemic inflammatory condition in which oxidative stress and endothelial dysfunction occurs. Plasma levels of soluble receptor for vascular endothelial growth factor (VEGFR)-1, also known as sFlt1 (soluble fms-like tyrosine kinase 1), an antiangiogenic factor have been reported to be elevated in preeclampsia. It was reported that pregnant mice deficient in catechol-O-methyltransferase (COMT) activity show a preeclampsia-like phenotype due to a deficiency or absence of 2-methoxyoestradiol (2-ME), a natural metabolite of estradiol that is elevated during the third trimester of normal human pregnancy. Additionally, autoantibodies (AT1-AAs) that bind and activate the angiotensin II receptor type 1 a (AT1 receptor) also have a role in preeclampsia. None of these abnormalities are consistently seen in all the patients with preeclampsia and some of them are not specific to pregnancy. Preeclampsia could occur due to an imbalance between pro- and antiangiogenic factors. VEGF, an angiogenic factor, is necessary for the transport of polyunsaturated fatty acids (PUFAs) to endothelial cells. Hence reduced VEGF levels decrease the availability of PUFAs to endothelial cells. This leads to a decrease in the formation of anti-inflammatory and angiogenic factors: lipoxins, resolvins, protectins, and maresins from PUFAs. Lipoxins, resolvins, protectins, maresins, and PUFAs suppress insulin resistance; activation of leukocytes, platelets, and macrophages; production of interleukin-6 and tumor necrosis factor-α; and oxidative stress and endothelial dysfunction; and enhance production of prostacyclin and nitric oxide (NO). Estrogen enhances the formation of lipoxin A4 and NO. PUFAs also augment the production of NO and inhibit the activity of angiotensin-converting enzyme and antagonize the actions of angiotensin II. Thus, PUFAs can prevent activation of angiotensin II receptor type 1 a (AT1 receptor). Patients with preeclampsia have decreased plasma phospholipid concentrations of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), the precursors of lipoxins (from AA), resolvins (from EPA and DHA), and protectins (from DHA) and prostaglandin E1 (PGE1 from DGLA: dihomo-γ-linolenic acid) and prostacyclin (PGI2 derived from AA). Based on these evidences, it is proposed that preeclampsia may occur due to deficiency of PUFAs and their anti-inflammatory products: lipoxins, resolvins, protectins, and maresins.

[Resolving factors of inflammation - a bridge between innate immunity and adaptive immunity]

Acute inflammation, a physiologic response to protect cells from microbial infection and other stimuli, is automatically terminated by endogenous anti-inflammatory and pro-resolving mediators to restore homeostatic conditions. However, if timely resolution of inflammation is failed, inflammation persists and can progress to a chronic inflammation such as rheumatoid arthritis, interstitial pneumonitis. To prevent chronic inflammation, understanding the process that resolves inflammation is essential. Resolution of inflammation is an active coordinated process regulated by distinct anti-inflammatory and pro-resolving endogenous lipid mediators, such as lipoxins/ALX, chemerin/chemR23. In resolution of inflammation these resolving factors contribute a bridge between innate and adaptive immunity.

Plasma oxylipin profiling identifies polyunsaturated vicinal diols as responsive to arachidonic acid and docosahexaenoic acid intake in growing piglets

The dose-responsiveness of plasma oxylipins to incremental dietary intake of arachidonic acid (20:4n-6; ARA) and docosahexaenoic acid (22:6n-3; DHA) was determined in piglets. Piglets randomly received one of six formulas (n = 8 per group) from days 3 to 27 postnatally. Diets contained incremental ARA or incremental DHA levels as follows (% fatty acid, ARA/DHA): (A1) 0.1/1.0; (A2) 0.53/1.0; (A3-D3) 0.69/1.0; (A4) 1.1/1.0; (D1) 0.66/0.33; and (D2) 0.67/0.62, resulting in incremental intake (g/kg BW/day) of ARA: 0.07 ± 0.01, 0.43 ± 0.03, 0.55 ± 0.03, and 0.82 ± 0.05 at constant DHA intake (0.82 ± 0.05), or incremental intake of DHA: 0.27 ± 0.02, 0.49 ± 0.03, and 0.81 ± 0.05 at constant ARA intake (0.54 ± 0.04). Plasma oxylipin concentrations and free plasma PUFA levels were determined at day 28 using LC-MS/MS. Incremental dietary ARA intake dose-dependently increased plasma ARA levels. In parallel, ARA intake dose-dependently increased ARA-derived diols 5,6- and 14,15-dihydroxyeicosatrienoic acid (DiHETrE) and linoleic acid-derived 12,13-dihydroxyoctadecenoic acid (DiHOME), downstream metabolites of cytochrome P450 expoxygenase (CYP). The ARA epoxide products from CYP are important in vascular homeostatic maintenance. Incremental DHA intake increased plasma DHA and most markedly raised the eicosapentaenoic acid (EPA) metabolite 17,18-dihydroxyeicosatetraenoic acid (DiHETE) and the DHA metabolite 19,20-dihydroxydocosapentaenoic acid (DiHDPE). In conclusion, increasing ARA and DHA intake dose-dependently influenced endogenous n-6 and n-3 oxylipin plasma concentrations in growing piglets, although the biological relevance of these findings remains to be determined.

Inflammation in cancer cachexia: to resolve or not to resolve (is that the question?)

BACKGROUND & AIMS

Cachexia is associated with poor prognosis and shortened survival in cancer patients. Growing evidence points out to the importance of chronic systemic inflammation in the aetiology of this syndrome. In the recent past, chronic inflammation was considered to result from overexpression and release of pro-inflammatory factors. However, this conception is now the focus of debate, since the importance of a crescent number of pro-resolving agents in the dissolution of inflammation is now recognised--leading to the hypothesis that chronic inflammation occurs rather due to failure in the resolution process. We intend to put forward the possibility that this may also be occurring in cancer cachexia.

METHODS

Recent reviews on inflammation and cachexia, and on the factors involved in the resolution of inflammation are discussed.

RESULTS

The available information suggests that indeed, inflammation resolution failure may be present in cachexia and therefore we speculate on possible mechanisms.

CONCLUSIONS

We emphasise the importance of studying resolution-related mechanisms in cancer cachexia and propose the opening of a new venue for cachexia treatment.

Radiation resistance, invasiveness and metastasis are inflammatory events that could be suppressed by lipoxin A4

Radiation induces overexpression and activity of the MET oncogene that, in turn, enhances the production of prostaglandin E(2), a pro-inflammatory molecule. Prostaglandin E(2) promotes tumor cell invasion, prevents apoptosis, enhances their metastasis and causes radioresistance. It is proposed that lipoxin A(4), a potent endogenous anti-inflammatory molecule, opposes the actions of prostaglandin E(2) and thus, could promote radiosensitivity, suppress tumor cell proliferation, invasiveness and suppress metastasis. Thus, methods designed to enhance endogenous lipoxin A(4) formation or its synthetic analogs may be useful in the management of cancer.

A defect in the activities of Δ and Δ desaturases and pro-resolution bioactive lipids in the pathobiology of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a low-grade systemic inflammatory condition, since liver and adipose tissue tumor necrosis factor-α (TNF-α) and TNF receptor 1 transcripts and serum TNF-α levels are increased and IL-6(-/-) mice are less prone to NAFLD. Fatty liver damage caused by high-fat diets is associated with the generation of pro-inflammatory prostaglandin E(2) (PGE(2)). A decrease in the levels of arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the usefulness of EPA and DHA both in the prevention and management of NAFLD has been reported. AA, EPA and DHA and their anti-inflammatory products lipoxins (LXs), resolvins and protectins suppress IL-6 and TNF-α and PGE(2) production. These results suggest that the activities of Δ(6) and Δ(5) desaturases are reduced in NAFLD and hence, the dietary essential fatty acids, linoleic acid (LA) and α-linolenic acid (ALA) are not metabolized to their long-chain products AA, EPA and DHA, the precursors of anti-inflammatory molecules, LXs, resolvins and protectins that could pre vent NAFLD. This suggests that an imbalance between pro- and anti-inflammatory bioactive lipids contribute to NAFLD. Hence, it is proposed that plasma and tissue levels of AA, EPA, DHA and LXs, resolvins and protectins could be used as predictors and prognostic biomarkers of NAFLD. It is suggested that the synthesis and use of more stable analogues of LXs, resolvins and protectins need to be explored in the prevention and management of NAFLD.