Inhibition of phagocyte-endothelium interactions by oxidized fatty acids: a natural anti-inflammatory mechanism?

Concerned topics of epidural labor analgesia: labor elongation and maternal pyrexia: a systematic review

Objective:

Labor is a complex process and labor pain presents challenges for analgesia. Epidural analgesia (EA) has a well-known analgesic effect and is commonly used during labor. This review summarized frequently encountered and controversial problems surrounding EA during labor, including the labor process and maternal intrapartum fever, to build knowledge in this area.

Data sources:

We searched for relevant articles published up to 2019 in PubMed using a range of search terms (eg, “labor pain,” “epidural,” “analgesia,” “labor process,” “maternal pyrexia,” “intrapartum fever”).

Study selection:

The search returned 835 articles, including randomized control trials, retrospective cohort studies, observational studies, and reviews. The articles were screened by title, abstract, and then full-text, with a sample independently screened by two authors. Thirty-eight articles were included in our final analysis; 20 articles concerned the labor process and 18 reported on maternal pyrexia during EA.

Results:

Four classic prospective studies including 14,326 participants compared early and delayed initiation of EA by the incidence of cesarean delivery. Early initiation following an analgesia request was preferred. However, it was controversial whether continuous use of EA in the second stage of labor induced adverse maternal and neonatal outcomes due to changes in analgesic and epidural infusion regimens. There was a high incidence of maternal pyrexia in women receiving EA and women with placental inflammation or histologic chorioamnionitis compared with those receiving systemic opioids.

Conclusions:

Early EA (cervical dilation ≥1 cm) does not increase the risk for cesarean section. Continuous epidural application of low doses of analgesics and programmed intermittent epidural bolus do not prolong second-stage labor duration or impact maternal and neonatal outcomes. The association between EA and maternal pyrexia remains controversial, but pyrexia is more common with EA than without. A non-infectious inflammatory process is an accepted mechanism of epidural-related maternal fever.

Biological activities of non-enzymatic oxygenated metabolites of polyunsaturated fatty acids (NEO-PUFAs) derived from EPA and DHA: New anti-arrhythmic compounds?

ω3 Polyunsaturated fatty acids (ω3 PUFAs) have several biological properties including anti-arrhythmic effects. However, there are some evidences that it is not solely ω3 PUFAs per se that are biologically active but the non-enzymatic oxygenated metabolites of polyunsaturated fatty acids (NEO-PUFAs) like isoprostanes and neuroprostanes. Recent question arises how these molecules take part in physiological homeostasis, show biological bioactivities and anti-inflammatory properties. Furthermore, they are involved in the circulations of childbirth, by inducing the closure of the ductus arteriosus. In addition, oxidative stress which can be beneficial for the heart in given environmental conditions such as the presence of ω3 PUFAs on the site of the stress and the signaling pathways involved are also explained in this review.

Physiological role of reactive oxygen species as promoters of natural defenses

It has been 60 yr since the discovery of reactive oxygen species (ROS) in biology and the beginning of the scientific community's attempt to understand the impact of the unpaired electron of ROS molecules in biological pathways, which was eventually noted to be toxic. Several studies have shown that the presence of ROS is essential in triggering or acting as a secondary factor for numerous pathologies, including metabolic and genetic diseases; however, it was demonstrated that chronic treatment with antioxidants failed to show efficacy and positive effects in the prevention of diseases or health complications that result from oxidative stress. On the contrary, such treatment has been shown to sometimes even worsen the disease. Because of the permanent presence of ROS in organisms, elaborate mechanisms to adapt with these reactive molecules and to use them without necessarily blocking or preventing their actions have been studied. There is now a large body of evidence that shows that living organisms have conformed to the presence of ROS and, in retrospect, have adapted to the bioactive molecules that are generated by ROS on proteins, lipids, and DNA. In addition, ROS have undergone a shift from being molecules that invoked oxidative damage in regulating signaling pathways that impinged on normal physiological and redox responses. Working in this direction, this review unlocks a new conception about the involvement of cellular oxidants in the maintenance of redox homeostasis in redox regulation of normal physiological functions, and an explanation for its essential role in numerous pathophysiological states is noted.-Roy, J., Galano, J.-M., Durand, T., Le Guennec, J.-Y., Lee, J. C.-Y. Physiological role of reactive oxygen species as promoters of natural defenses.

DHA-derived oxylipins, neuroprostanes and protectins, differentially and dose-dependently modulate the inflammatory response in human macrophages: Putative mechanisms through PPAR activation

Whereas the anti-inflammatory properties and mechanisms of action of long chain ω3 PUFAs have been abundantly investigated, research gaps remain regarding the respective contribution and mechanisms of action of their oxygenated metabolites collectively known as oxylipins. We conducted a dose-dependent and comparative study in human primary macrophages aiming to compare the anti-inflammatory activity of two types of DHA-derived oxylipins including the well-described protectins (NPD1 and PDX), formed through lipoxygenase pathway and the neuroprostanes (14-A_4t- and 4-F_4t-NeuroP) formed through free-radical mediated oxygenation and expected to be new anti-inflammatory mediators. Considering the potential ability of these DHA-derived oxylipins to bind PPARs and knowing the central role of these transcription factors in the regulation of macrophage inflammatory response, we performed transactivation assays to compare the ability of protectins and neuroprostanes to activate PPARs. All molecules significantly reduced mRNA levels of cytokines such as IL-6 and TNF-α, however not at the same doses. NPD1 showed the most effect at 0.1µM (-14.9%, p<0.05 for IL-6 and -26.7%, p<0.05 for TNF-α) while the three other molecules had greater effects at 10µM, with the strongest result due to the cyclopentenone neuroprostane, 14-A_4t-NeuroP (-49.8%, p<0.001 and -40.8%, p<0.001, respectively). Part of the anti-inflammatory properties of the DHA-derived oxylipins investigated could be linked to their activation of PPARs. Indeed, all tested oxylipins significantly activated PPARγ, with 14-A_4t-NeuroP leading to the strongest activation, and NPD1 and PDX also activated PPARα. In conclusion, our results show that neuroprostanes and more especially cyclopentenone neuroprostanes have potent anti-inflammatory activities similar or even more pronounced than protectins supporting that neuroprostanes should be considered as important contributors to the anti-inflammatory effects of DHA.

Inflammation and Epidural-Related Maternal Fever: Proposed Mechanisms

Intrapartum fever is associated with excessive maternal interventions as well as higher neonatal morbidity. Epidural-related maternal fever (ERMF) contributes to the development of intrapartum fever. The mechanism(s) for ERMF has remained elusive. Here, we consider how inflammatory mechanisms may be modulated by local anesthetic agents and their relevance to ERMF. We also critically reappraise the clinical data with regard to emerging concepts that explain how anesthetic drug-induced metabolic dysfunction, with or without activation of the inflammasome, might trigger the release of nonpathogenic, inflammatory molecules (danger-associated molecular patterns) likely to underlie ERMF.

Non-enzymatic cyclic oxygenated metabolites of omega-3 polyunsaturated fatty acid: Bioactive drugs?

Non-enzymatic oxygenated metabolites derived from polyunsaturated fatty acids (PUFA) are formed in vivo through free radical reaction under oxidative stress conditions. It has been over twenty-five years since the discovery of cyclic oxygenated metabolites derived from arachidonic acid (20:4 n-6), the isoprostanes, and since then they have become biomarkers of choice for assessing in vivo OS in humans and animals. Chemical synthesis of n-3 PUFA isoprostanoids such as F3-Isoprostanes from eicosapentaenoic acid (20:5 n-3), and F4-Neuroprostanes from docosahexaenoic acid (22:6 n-6) unravelled novel and unexpected biological properties of such omega-3 non-enzymatic cyclic metabolites as highlighted in this review.

Modulation of endothelial cell integrity and inflammatory activation by commercial lipid emulsions

Background

Thrombosis and immune dysfunction are two important complications that result from the administration of parenteral nutrition. Endothelial cells within the vasculature are crucial components necessary for maintenance of normal coagulation and immune function.

Methods

We compared the effects of three commercial lipid emulsions (LEs; Intralipid®, ClinOleic® [or Clinolipid®], and Omegaven®) differing in the levels of omega-6 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, omega-9 monounsaturated fatty acids, and saturated fatty acids upon endothelial cell fatty acid composition using Gas chromatography, endothelial cell integrity by assessing measurement of apoptosis and necrosis using flow cytometry, endothelial cell inflammatory activation by assessing the induction of ICAM-1 by lipopolysaccharide [LPS]), and transcription factor activation (phosphorylation of NF-κB) using western blot analysis.

Results

Gas chromatographic analysis confirmed cellular uptake of the fatty acids within the LEs; furthermore, these fatty acid changes reflected the composition of the oils and egg phosphatides used in the manufacturing of these emulsions. However, the kinetics of fatty acid uptake and processing differed between LEs. Fish oil LE negatively impacted cell viability by doubling the percentage of apoptotic and necrotic cell populations quantified by flow cytometry using Annexin V/Fluorescein and propidium iodide. The soybean oil LE did not alter cell viability, while the olive oil-predominate emulsion improved cell viability. All LEs were capable of suppressing LPS-induced ICAM-1 expression; however, the fish oil LE was more potent than the other emulsions. Fish oil LE supplementation of cells also suppressed LPS-induced phosphorylation of NF-κB, while the soybean oil and olive predominant LE had no effect upon NF-κB phosphorylation.

Conclusions

Lipid emulsions are readily incorporated and stored in the form of triacylglycerols. Soybean oil-based, olive oil-predominant and fish-oil based LEs differentially affected endothelial cell integrity. Importantly, these three LEs were capable of suppressing endothelial cell inflammatory response despite their fatty acid content.

Non-enzymatic cyclic oxygenated metabolites of adrenic, docosahexaenoic, eicosapentaenoic and α-linolenic acids; bioactivities and potential use as biomarkers

Cyclic oxygenated metabolites are formed in vivo through non-enzymatic free radical reaction of n-6 and n-3 polyunsaturated fatty acids (PUFAs) such as arachidonic (ARA C20:4 n-6), adrenic (AdA 22:4 n-6), α-linolenic (ALA 18:3 n-3), eicosapentaenoic (EPA 20:5 n-3) and docosahexaenoic (DHA 22:6 n-3) acids. These cyclic compounds are known as isoprostanes, neuroprostanes, dihomo-isoprostanes and phytoprostanes. Evidence has emerged for their use as biomarkers of oxidative stress and, more recently, the n-3PUFA-derived compounds have been shown to mediate bioactivities as secondary messengers. Accordingly, this review will focus on the cyclic oxygenated metabolites generated from AdA, ALA, EPA and DHA. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

EPA-coated titanium implants promote osteoconduction in white New Zealand rabbits

OBJECTIVES

To investigate the effect of eicosapentaenoic acid (EPA)-coated Ti implants on osteoconduction in white New Zealand rabbit mandibles.

MATERIAL AND METHODS

Sandblasted and cleansed planar titanium specimens with a size of 5 × 5 × 1 mm were coated on one side with 0.25 vol% eicosapentaenoic acid (EPA). The other side of the specimens was kept highly polished (the control side). These specimens were inserted in rabbit mandibles. Twelve rabbits were randomly assigned into three study groups (n = 4). The rabbits were sacrificed at 4, 8, and 12 weeks. The harvested specimens with the implants were assessed for new bone formation on both sides of the implant using CBCT, conventional radiographs, and the biaxial pullout test. The results were statistically analyzed by a nonparametric Kruskal-Wallis test and Friedman's test as multiple comparisons and by Brunner-Langer nonparametric mixed model approach (R Software).

RESULTS

A significant osteoconductive bone formation was found on the EPA-coated Ti implant surface (P < 0.05) at 8 weeks when compared to the polished surface (control). Biaxial pullout test results showed a significant difference (P < 0.05) after 8 and 12 weeks with a maximum force of 243.8 N, compared to 143.25 N after 4 week.

CONCLUSION

EPA implant coating promoted osteoconduction on the Ti implant surfaces, enhancing the anchorage of the implant to the surrounding bone in white New Zealand rabbits.

Lipid profiling following intake of the omega 3 fatty acid DHA identifies the peroxidized metabolites F4-neuroprostanes as the best predictors of atherosclerosis prevention

The anti-atherogenic effects of omega 3 fatty acids, namely eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) are well recognized but the impact of dietary intake on bioactive lipid mediator profiles remains unclear. Such a profiling effort may offer novel targets for future studies into the mechanism of action of omega 3 fatty acids. The present study aimed to determine the impact of DHA supplementation on the profiles of polyunsaturated fatty acids (PUFA) oxygenated metabolites and to investigate their contribution to atherosclerosis prevention. A special emphasis was given to the non-enzymatic metabolites knowing the high susceptibility of DHA to free radical-mediated peroxidation and the increased oxidative stress associated with plaque formation. Atherosclerosis prone mice (LDLR^−/−) received increasing doses of DHA (0, 0.1, 1 or 2% of energy) during 20 weeks leading to a dose-dependent reduction of atherosclerosis (R² = 0.97, p = 0.02), triglyceridemia (R² = 0.97, p = 0.01) and cholesterolemia (R² = 0.96, p<0.01). Targeted lipidomic analyses revealed that both the profiles of EPA and DHA and their corresponding oxygenated metabolites were substantially modulated in plasma and liver. Notably, the hepatic level of F₄-neuroprostanes, a specific class of DHA peroxidized metabolites, was strongly correlated with the hepatic DHA level. Moreover, unbiased statistical analysis including correlation analyses, hierarchical cluster and projection to latent structure discriminate analysis revealed that the hepatic level of F₄-neuroprostanes was the variable most negatively correlated with the plaque extent (p<0.001) and along with plasma EPA-derived diols was an important mathematical positive predictor of atherosclerosis prevention. Thus, oxygenated n-3 PUFAs, and F₄-neuroprostanes in particular, are potential biomarkers of DHA-associated atherosclerosis prevention. While these may contribute to the anti-atherogenic effects of DHA, further in vitro investigations are needed to confirm such a contention and to decipher the molecular mechanisms of action.

Peroxidation of n-3 Polyunsaturated Fatty Acids Inhibits the Induction of iNOS Gene Expression in Proinflammatory Cytokine-Stimulated Hepatocytes

Eicosapentaenoic acid and docosahexaenoic acid (EPA/DHA), n-3 polyunsaturated fatty acids (PUFAs), have a variety of biological activities including anti-inflammatory and anticancer effects. We hypothesized that their peroxidized products contributed in part to anti-inflammatory effects. In the liver, the production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been implicated as one of the factors in hepatic inflammation and injury. We examined whether the peroxidation of EPA/DHA influences the induction of iNOS and NO production in proinflammatory cytokine-stimulated cultured hepatocytes, which is in vitro liver inflammation model. Peroxidized EPA/DHA inhibited the induction of iNOS and NO production in parallel with the increased levels of their peroxidation, whereas unoxidized EPA/DHA had no effects at all. Peroxidized EPA/DHA reduced the activation of transcription factor, NF-κB, and the expression of the iNOS antisense transcript, which are involved in iNOS promoter transactivation (mRNA synthesis) and its mRNA stabilization, respectively. These findings demonstrated that peroxidized products of EPA/DHA suppressed the induction of iNOS gene expression through both of the transcriptional and posttranscriptional steps, leading to the prevention of hepatic inflammation.

n-3 Fatty acids block TNF-α-stimulated MCP-1 expression in rat mesangial cells

Monocyte chemoattractant protein 1 (MCP-1) is a CC cytokine that fundamentally contributes to the pathogenesis of inflammatory renal disease. MCP-1 is highly expressed in cytokine-stimulated mesangial cells in vitro and following glomerular injury in vivo. Interventions to limit MCP-1 expression are commonly effective in assorted experimental models. Fish oil, an abundant source of n-3 fatty acids, has anti-inflammatory properties, the basis of which remains incompletely defined. We examined potential mechanisms whereby fish oil reduces MCP-1 expression and thereby suppresses inflammatory responses to tissue injury. Cultured mesangial cells were treated with TNF-α in the presence of the n-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA); equimolar concentrations of the n-6 fatty acids LA and OA served as controls. MCP-1 mRNA expression was assessed by Northern blotting, and transcriptional activity of the MCP-1 promoter was assessed by transient transfection. The involvement of the ERK and NF-κB pathways was evaluated through transfection analysis and the use of the MEK inhibitor U0126. DHA and EPA decreased TNF-α-stimulated MCP-1 mRNA expression by decreasing transcription of the MCP-1 gene. DHA and EPA decreased p-ERK expression and nuclear translocation of NF-κB, both of which are necessary for TNF-α-stimulated MCP-1 expression. Both NF-κB and AP-1 sites were involved in transcriptional regulation of the MCP-1 gene by DHA and EPA. We conclude that DHA and EPA inhibit TNF-α-stimulated transcription of the MCP-1 gene through interaction of signaling pathways involving ERK and NF-κB. We speculate that such effects may contribute to the salutary effect of fish oil in renal and vascular disease.

Formation of highly reactive cyclopentenone isoprostane compounds (A3/J3-isoprostanes) in vivo from eicosapentaenoic acid

Omega-3 (omega-3) polyunsaturated fatty acids (PUFAs) found in marine fish oils are known to suppress inflammation associated with a wide variety of diseases. Eicosapentaenoic acid (EPA) is one of the most abundant omega-3 fatty acids in fish oil, but the mechanism(s) by which EPA exerts its beneficial effects is unknown. Recent studies, however, have demonstrated that oxidized EPA, rather than native EPA, possesses anti-atherosclerotic, anti-inflammatory, and anti-proliferative effects. Very few studies to date have investigated which EPA oxidation products are responsible for this bioactivity. Our research group has previously reported that anti-inflammatory prostaglandin A(2)-like and prostaglandin J(2)-like compounds, termed A(2)/J(2)-isoprostanes (IsoPs), are produced in vivo by the free radical-catalyzed peroxidation of arachidonic acid and represent one of the major products resulting from the oxidation of this PUFA. Based on these observations, we questioned whether cyclopentenone-IsoP compounds are formed from the oxidation of EPA in vivo. Herein, we report the formation of cyclopentenone-IsoP molecules, termed A(3)/J(3)-IsoPs, formed in abundance in vitro and in vivo from EPA peroxidation. Chemical approaches coupled with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) were used to structurally characterize these compounds as A(3)/J(3)-IsoPs. We found that levels of these molecules increase approximately 200-fold with oxidation of EPA in vitro from a basal level of 0.8 +/- 0.4 ng/mg EPA to 196 +/- 23 ng/mg EPA after 36 h. We also detected these compounds in significant amounts in fresh liver tissue from EPA-fed rats at basal levels of 19 +/- 2 ng/g tissue. Amounts increased to 102 +/- 15 ng/g tissue in vivo in settings of oxidative stress. These studies have, for the first time, definitively characterized novel, highly reactive A/J-ring IsoP compounds that form in abundance from the oxidation of EPA in vivo.

In Vivo and in Vitro Lipid Peroxidation of Arachidonate Esters: The Effect of Fish Oil ω-3 Lipids on Product Distribution

The effect of lipid composition on the distribution of free radical oxidation products derived from arachidonic acid (20:4) esters has been studied in vitro and in vivo. Pro-inflammatory prostaglandin (PG) F2-like compounds, termed F2-isoprostanes (IsoPs), are produced in vivo and in vitro by the free radical-catalyzed peroxidation of arachidonic acid. Controlled free radical oxidation of mixtures of fatty acid esters in vitro showed that the formation of IsoPs from arachidonate is dramatically influenced by the presence of other fatty acid esters in the reaction mixture. Thus, three lipid mixtures containing the same arachidonate concentration but different amounts of other fatty esters (16:0; 18:1; 18:2; 20:5, and 22:6) were oxidized, and the product yields were determined by GC and LC/MS/MS analysis. The yield of F2-IsoP formed after 1 h of oxidation was 18% (based on arachidonate consumed) for mixtures containing arachidonate as the only oxidizable PUFA, but yields of these biologically active compounds dropped to 6% in polyunsaturated fatty acid (PUFA) mixtures typical of those found in tissues of fish oil-fed animals. F2-IsoP levels were also monitored in the livers of mice on diets supplemented with eicosapentaenoic acid (C20:5 omega-3; EPA), the PUFA most abundant in fish oil. While the level of arachidonic acid present in livers was not significantly different from that in control animals, levels of IsoPs in the liver were reduced in the EPA-fed mice compared to those in controls under conditions of oxidative stress (60 +/- 25% reduction, n = 5) or at baseline (48 +/- 14% reduction, n = 5). These results suggest that dietary omega-3 PUFAs may influence the formation of bio-active peroxidation products derived from omega-6 PUFAs by channeling the free radical pathway away from the F2-IsoPs.

Essential fatty acids: biochemistry, physiology and pathology

Essential fatty acids (EFAs), linoleic acid (LA), and alpha-linolenic acid (ALA) are essential for humans, and are freely available in the diet. Hence, EFA deficiency is extremely rare in humans. To derive the full benefits of EFAs, they need to be metabolized to their respective long-chain metabolites, i.e., dihomo-gamma-linolenic acid (DGLA), and arachidonic acid (AA) from LA; and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from ALA. Some of these long-chain metabolites not only form precursors to respective prostaglandins (PGs), thromboxanes (TXs), and leukotrienes (LTs), but also give rise to lipoxins (LXs) and resolvins that have potent anti-inflammatory actions. Furthermore, EFAs and their metabolites may function as endogenous angiotensin-converting enzyme and 3-hdroxy-3-methylglutaryl coenzyme A reductase inhibitors, nitric oxide (NO) enhancers, anti-hypertensives, and anti-atherosclerotic molecules. Recent studies revealed that EFAs react with NO to yield respective nitroalkene derivatives that exert cell-signaling actions via ligation and activation of peroxisome proliferator-activated receptors. The metabolism of EFAs is altered in several diseases such as obesity, hypertension, diabetes mellitus, coronary heart disease, schizophrenia, Alzheimer's disease, atherosclerosis, and cancer. Thus, EFAs and their derivatives have varied biological actions and seem to be involved in several physiological and pathological processes.

Formation of F-ring isoprostane-like compounds (F3-isoprostanes) in vivo from eicosapentaenoic acid

Eicosapentaenoic acid (EPA, C20:5, omega-3) is the most abundant polyunsaturated fatty acid (PUFA) in fish oil. Recent studies suggest that the beneficial effects of fish oil are due, in part, to the generation of various free radical-generated non-enzymatic bioactive oxidation products from omega-3 PUFAs, although the specific molecular species responsible for these effects have not been identified. Our research group has previously reported that pro-inflammatory prostaglandin F2-like compounds, termed F2-isoprostanes (IsoPs), are produced in vivo by the free radical-catalyzed peroxidation of arachidonic acid and represent one of the major products resulting from the oxidation of this PUFA. Based on these observations, we questioned whether F2-IsoP-like compounds (F3-IsoPs) are formed from the oxidation of EPA in vivo. Oxidation of EPA in vitro yielded a series of compounds that were structurally established to be F3-IsoPs using a number of chemical and mass spectrometric approaches. The amounts formed were extremely large (up to 8.7 + 1.0 microg/mg EPA) and greater than levels of F2-IsoPs generated from arachidonic acid. We then examined the formation of F3-IsoPs in vivo in mice. Levels of F3-IsoPs in tissues such as heart are virtually undetectable at baseline, but supplementation of animals with EPA markedly increases quantities up to 27.4 + 5.6 ng/g of heart. Interestingly, EPA supplementation also markedly reduced levels of pro-inflammatory arachidonate-derived F2-IsoPs by up to 64% (p < 0.05). Our studies provide the first evidence that identify F3-IsoPs as novel oxidation products of EPA that are generated in vivo. Further understanding of the biological consequences of F3-IsoP formation may provide valuable insights into the cardioprotective mechanism of EPA.

Oxidized omega-3 fatty acids inhibit pro-inflammatory responses in glomerular endothelial cells

BACKGROUND

Omega-3 fatty acids have beneficial effects in chronic inflammatory diseases that are characterized by accumulation of leukocytes and leukocyte-mediated tissue injury. Accumulation of leukocytes occurs, in part, due to pro-inflammatory responses in endothelial cells, such as increase in expression of leukocyte adhesion receptors and chemokines, such as MCP-1 and IL-8.

METHODS

omega-3 fatty acids, such as EPA, are highly polyunsaturated and readily undergo auto-oxidation. We studied the effect of oxidized EPA and unoxidized (native) EPA on leukocyte-glomerular endothelial cell interactions using adhesion assays, ELISA assays and transmigration assays. We used electrophoresis mobility shift assays to determine the effect of oxidized and unoxidized EPA on cytokine-induced nuclear factor-kappaB (NF-kappaB) activation.

RESULTS

Oxidized EPA but not unoxidized EPA dose-dependently inhibits cytokine-induced leukocyte adhesion receptors on glomerular endothelial cells, which correlates with inhibition of leukocyte-glomerular endothelial cell interactions. Oxidized EPA but not unoxidized EPA inhibits cytokine-induced glomerular endothelial and mesangial cell expression of MCP-1, and to a lesser extent IL-8. Transmigration assays show that oxidized EPA but not unoxidized EPA inhibits leukocyte transmigration across glomerular endothelial cells. Oxidized EPA but not unoxidized EPA potently inhibited cytokine-induced activation of NF-kappaB in glomerular endothelial and mesangial cells.

CONCLUSIONS

These studies show that the beneficial effects of fish oil in chronic inflammatory diseases, including IgA nephropathy, may result from the inhibitory effects of oxidized omega-3 fatty acids on pro-inflammatory events in endothelial cells via inhibition of NF-kappaB activation.

Oxidized omega-3 fatty acids inhibit NF-kappaB activation via a PPARalpha-dependent pathway

OBJECTIVE

The aim of this study was to determine the effects of oxidized versus native omega-3 fatty acids on the endothelial expression of chemokines MCP-1 and IL-8, and, if effective in inhibiting chemokine expression, to determine the mechanism for the inhibition of chemokine expression.

METHODS AND RESULTS

Using enzyme-linked immunosorbent assays, we show that oxidized EPA and DHA but not unoxidized EPA or DHA inhibit cytokine-induced endothelial expression of monocyte chemoattractant protein (MCP)-1 and, to a lesser extent, IL-8. In electrophoretic mobility shift assays, oxidized EPA but not unoxidized EPA potently inhibited cytokine-induced activation of endothelial nuclear factor-kappaB (NF-kappaB). Using Western blot analyses, we show that the inhibition of NF-kappaB activation was not caused by prevention of phosphorylation of IkappaBalpha because oxidized EPA did not inhibit cytokine-induced phosphorylation and ubiquination of IkappaBalpha. Furthermore, oxidized EPA inhibited NF-kappaB activation in endothelial cells derived from wild-type mice but had no inhibitory effects on NF-kappaB activation in endothelial cells derived from peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice, indicating that oxidized EPA requires PPARalpha for its inhibitory effects on NF-kappaB.

CONCLUSIONS

These studies show that the antiinflammatory effects of fish oil may result from the inhibitory effects of oxidized omega-3 fatty acids on NF-kappaB activation via a PPARalpha-dependent pathway.

Inhibition of leukocyte-endothelial interactions by oxidized omega-3 fatty acids: a novel mechanism for the anti-inflammatory effects of omega-3 fatty acids in fish oil

Omega-3 fatty acids which are abundant in fish oil improve the prognosis of several chronic inflammatory diseases that are characterized by leukocyte-mediated tissue injury. The omega-3 fatty acids, such as eicosapentaenoic acid (EPA), are highly polyunsaturated and readily undergo oxidation. Our data suggest that the beneficial effects of fish oil may be due to the oxidative modification of omega-3 fatty acids. The oxidized products inhibit leukocyte adhesion receptor expression and leukocyte-endothelial interactions. Oxidized EPA is a potent inhibitor of leukocyte interactions with the endothelium compared to native EPA, both in vitro and in an in vivo context of inflammation. The effects of oxidized EPA are mediated through activation of PPARalpha and subsequent inhibition of NF-kappaB, leading to the down-regulation of leukocyte adhesion receptor expression required for leukocyte-endothelial interactions. We propose that oxidation of EPA and its activation of PPARalpha and subsequent inhibition of NF-kappaB is the underlying mechanism for the beneficial effects of fish oil.

The natural activities of cells, the role of reactive oxygen species, and their relation to antioxidants, nutraceuticals, botanicals, and other biologic therapies

There have been remarkable advances in molecular and cell biology that define the mechanisms of how various supplements function in and around cells. Current evidence strongly supports the probability that cellular functions and cellular responses that pertain to inflammation, disease, and life and death activity can be modulated with supplementation; however, the complexity of each individual's reaction and the vast differences in physiologic influences makes clinical research difficult in regard to clinical studies using antioxidant and biologic therapies. Not enough is known specifically about each supplement and its interactions with cells, nor is enough understood about how the body compensates or reacts to such applications. What works well in one individual or species might work differently in another. In addition, not all antioxidants are created equally, and discrepancies in purity and absorption can occur. It must also be determined whether or not less than optimum levels or infrequent usage will produce the same physiological effects. Not everyone--nor every species of animal--responds in the same manner to supplements, which might account for the variations in clinical research. The cellular effects of antioxidants and other supplements are well defined and meaningful, and their clinical application looks promising despite individual variations. Combinations of antioxidants are synergistic and support cellular functions, effects that are often not apparent with individual agents. Such combinations offer a variety of mechanisms for reducing oxygen metabolites in tissues, altering signaling pathways, and modulating transcription factors, and they might play key roles in reducing the damage afforded by ROS. It is the author's opinion that combinations of antioxidants are best suited for clinical application in modulating disease and reducing premature aging when caused by excessive free radical accumulation. Clinicians should approach clinical application of these supplements based on the best available scientific research and species-specific information available.

Docosahexaenoic acid ameliorates murine ischemic acute renal failure and prevents increases in mRNA abundance for both TNF-alpha and inducible nitric oxide synthase

This study demonstrates that intraperitoneal injections of DHA (all cis 4,7,10,13,16,19 docosahexaenoic acid C22: n-3) bound to bovine serum albumin ameliorate murine acute renal failure (ARF) induced by temporary occlusion of the renal artery. Three micromoles of DHA decreased serum creatinine (Scr) from 2.3 mg/dl to 1.1 mg/dl 24 h after reperfusion (n = 15; P < 0.05). Scr of the treated animals were significantly lower than controls throughout a 7-d time course. Although lower doses of DHA were less effective, higher doses were not more effective. Ribonuclease (RNase) protection assays showed that ischemia increased mRNA abundance for TNF-alpha and inducible nitric oxide synthase (iNOS) at 24 h. This increase was prevented by DHA administration. Because TNF-alpha and iNOS contribute to renal ischemic injury, their inhibition may contribute to DHA's salutary effect. In addition, the data may have therapeutic implications, because the DHA improves ARF even when administered at 4 h after reperfusion.

Oxidized omega-3 fatty acids in fish oil inhibit leukocyte-endothelial interactions through activation of PPAR alpha

Omega-3 fatty acids, which are abundant in fish oil, improve the prognosis of several chronic inflammatory diseases although the mechanism for such effects remains unclear. These fatty acids, such as eicosapentaenoic acid (EPA), are highly polyunsaturated and readily undergo oxidation. We show that oxidized, but not native unoxidized, EPA significantly inhibited human neutrophil and monocyte adhesion to endothelial cells in vitro by inhibiting endothelial adhesion receptor expression. In transcriptional coactivation assays, oxidized EPA potently activated the peroxisome proliferator-activated receptor alpha (PPAR alpha), a member of the nuclear receptor family. In vivo, oxidized, but not native, EPA markedly reduced leukocyte rolling and adhesion to venular endothelium of lipopolysaccharide (LPS)-treated mice. This occurred via a PPAR alpha-dependent mechanism because oxidized EPA had no such effect in LPS-treated PPAR alpha-deficient mice. Therefore, the beneficial effects of omega-3 fatty acids may be explained by a PPAR alpha-mediated anti-inflammatory effect of oxidized EPA.

Assessment of omega-fatty-acid-supplemented human platelets for potential improvement in long-term storage

Uptake of omega (omega)-3 fatty acids can influence membrane stability and cell mobility. We investigated the effects of omega-3 and -6 fatty acids on the hemostatic efficacy of human platelets using an in vivo rabbit bleeding model. In vitro assays such as platelet aggregation, vWF bead-mediated ATP release and platelet adhesion to beads (measured by the residual platelet count [RPC] [free platelet count after reacting with the beads]/[baseline platelet count]x 100=%RPC; a high %RPC indicates reduced platelet function) were conducted on platelets treated with 1% fish oil (omega-3); 2% fish oil emulsion or 1% soy oil (omega-6). Oil treatment of platelets reduced the vWF bead-induced ATP release insignificantly. Addition of omega-3 agents reduced physical reactivity (%RPC) with the vWF beads by a factor of 1.2 (oil) and 1.9 (emulsion). The omega-6 oil enhanced reactivity by a factor of 1.7. After washing to remove excess reagent, platelet resuspension was most efficient with the omega-3 emulsion. Platelet function was higher with the omega-3-treated platelets (%RPC=52.3%, omega-3 oil; 63.3%, omega-3 emulsion vs. 85%, omega-6 oil; 82% untreated platelets). Ethyl-palmitate-treated thrombocytopenic rabbits were infused with human platelets. Survival times of the treated platelets, as monitored by flow cytometry (6.2-8.2 h) were comparable to untreated platelets (8.6 h). In the rabbit kidney injury model, blood loss after infusion of the treated platelets was similar to that of saline-infused rabbits (75.3+/-3.4 g). However, platelets washed prior to infusion reduced blood loss to a value comparable to that of fresh platelets (48.3+/-5 g). Furthermore, the presence of the infused platelets at the injury site was clearly visualized using FITC-tagged anti CD42a antibody. Thus, the omega-3-based agents protect the platelets from damage during the washing procedure as demonstrated in vitro by improved platelet resuspension, low %RPC, high stimulus-responsive ATP secretion and a reduction in blood loss in vivo.

Inhibitory effects of S-(-) and R-(+) bupivacaine on neutrophil function

BACKGROUND

Local anesthetics inhibit migration, enzyme release and superoxide anion generation of polymorphonuclear leukocytes (PMN). Due to their ability to phagocytose and kill bacteria PMN represent a major defense mechanism in the circulating blood. In this study we determined the influence of racemic bupivacaine and its enantiomers on neutrophil phagocytic activity, oxidative burst as well as surface expression of complement and Fcgamma receptors.

METHODS

Venous blood was pre-incubated with different concentrations of either racemic bupivacaine, R-(+) or S-(-) bupivacaine. Fluoresceine isothiocyanate (FITC)-labeled antibodies against Fcgamma receptor III (CD16), complement receptor 1 (CD35) and complement receptor 3 (CD11b) were used to determine surface receptor expression. Phagocytic activity was measured by ingestion of FITC-labeled vital Staphylococcus aureus. Oxidative burst was determined by conversion of nonfluorescent dihydrorhodamine 123 into fluorescent rhodamine 123. Fluorescent intensity of each sample was determined by flow cytometry.

RESULTS

Racemic bupivacaine inhibited surface receptor expression, phagocytosis, and oxidative burst in a time- and concentration-dependent manner. Although the S-(-) enantiomer exerted significantly less inhibitory action on neutrophil function compared to R-(+) and racemic bupivacaine, these effects were small compared to the overall changes.

CONCLUSION

These findings suggest that bupivacaine impairs surface receptor expression and may thereby contribute to reduced phagocytic activity and oxidative burst. Enantiomer-specific effects of bupivacaine may play a minor role in the inhibition of these leukocyte functions.

n-3 polyunsaturated fatty acid supplementation, monocyte adhesion molecule expression and pro-inflammatory mediators in Type 2 diabetes mellitus

AIMS

To examine the effect of n-3 polyunsaturated fatty acid supplements on the monocyte surface expression of adhesion molecules involved in proatherogenic monocyte-endothelial interactions, and on pro-inflammatory mediators in Type 2 diabetes mellitus.

METHODS

Twenty-nine subjects with Type 2 diabetes and 21 controls without diabetes were studied. Monocyte expression of leucocyte function-associated antigens 1 and 3, intercellular adhesion molecule-1, and the major histocompatibility complex class II molecule HLA-DR were measured using a laser flow cytometric method. Supplementation with 2.08 g n-3 fatty acids for 21 days was undertaken and measurements repeated. Plasma soluble adhesion molecule concentrations, plasminogen activator inhibitor-1 activity and antigen and pro-inflammatory mediators (cysteinyl leukotriene and monocyte leukotriene B4) were also measured.

RESULTS

Groups did not differ in monocyte expression of adhesion molecules or HLA-DR, or in leukotriene production although plasma soluble adhesion molecule concentrations were higher in the diabetes groups (P<0.05). n-3 fatty acid supplementation influenced neither the expression of these molecules nor plasma soluble adhesion molecule concentrations or leukotriene production.

CONCLUSIONS

This study does not support increased monocyte adhesion molecule expression or abnormal monocyte production of pro-inflammatory mediators as mechanisms for increased atherogenic risk in Type 2 diabetes. Cardioprotective actions of n-3 fatty acids may not be mediated through these mechanisms.

Free radicals, cytokines and nitric oxide in cardiac failure and myocardial infarction

Myocardial infarction is the most common cause of congestive cardiac failure. Free radicals, cytokines, nitric oxide (NO) and antioxidants play a major role both in atherosclerosis and myocardial damage and preservation. In the early stages of atherosclerosis, neutrophils and monocytes infiltrate the intima and generate free radicals which damage the endothelial cells. As a result, production of NO and prostacyclin by the endothelial cells declines, which have cardioprotective actions. This also has relevance to the beneficial action of aspirin since, it can modulate both prostanoid and L-arginine-NO systems and NF-kB translocation. In both acute myocardial infarction and chronic congestive cardiac failure, the plasma levels of various inflammatory mediators such as interleukins and tumour necrosis factor-alpha (TNFalpha) are elevated. TNFalpha, produced by the inflammatory cells and the myocardium, can suppress myocardial contractility and induce the production of free radicals, which in turn can further damage the myocardium. Transforming growth factor beta (TGFbeta), polyunsaturated fatty acids and the glucose-insulin-potassium regimen can antagonize the harmful actions of TNFalpha and protect the myocardium. This explains why efforts made to reduce the levels of pro-inflammatory cytokines have beneficial action and preserve the myocardium.

Novel functional sets of lipid-derived mediators with antiinflammatory actions generated from omega-3 fatty acids via cyclooxygenase 2-nonsteroidal antiinflammatory drugs and transcellular processing

Aspirin therapy inhibits prostaglandin biosynthesis without directly acting on lipoxygenases, yet via acetylation of cyclooxygenase 2 (COX-2) it leads to bioactive lipoxins (LXs) epimeric at carbon 15 (15-epi-LX, also termed aspirin-triggered LX [ATL]). Here, we report that inflammatory exudates from mice treated with omega-3 polyunsaturated fatty acid and aspirin (ASA) generate a novel array of bioactive lipid signals. Human endothelial cells with upregulated COX-2 treated with ASA converted C20:5 omega-3 to 18R-hydroxyeicosapentaenoic acid (HEPE) and 15R-HEPE. Each was used by polymorphonuclear leukocytes to generate separate classes of novel trihydroxy-containing mediators, including 5-series 15R-LX(5) and 5,12,18R-triHEPE. These new compounds proved to be potent inhibitors of human polymorphonuclear leukocyte transendothelial migration and infiltration in vivo (ATL analogue > 5,12,18R-triHEPE > 18R-HEPE). Acetaminophen and indomethacin also permitted 18R-HEPE and 15R-HEPE generation with recombinant COX-2 as well as omega-5 and omega-9 oxygenations of other fatty acids that act on hematologic cells. These findings establish new transcellular routes for producing arrays of bioactive lipid mediators via COX-2-nonsteroidal antiinflammatory drug-dependent oxygenations and cell-cell interactions that impact microinflammation. The generation of these and related compounds provides a novel mechanism(s) for the therapeutic benefits of omega-3 dietary supplementation, which may be important in inflammation, neoplasia, and vascular diseases.

Oleic Acid Increases Cell Surface Expression and Activity of CD11b on Human Neutrophils

Traumatic bone injury frequently results in the release of marrow-derived fatty material into the circulation. This may lead to the syndrome of fat embolism, associated with the generation of free fatty acids, the sequestration of neutrophils in the lungs, and the subsequent development of acute respiratory distress. Neutrophil accumulation in tissues requires their adherence to vascular endothelial cells and involves the β2 integrin, CD11b/CD18 (Mac-1). We now report that the exposure of isolated human neutrophils to oleic acid causes a rapid increase in the cell surface expression and affinity state of CD11b, particularly under acidic conditions that are typical of inflammatory sites. Oleic acid also triggers neutrophil aggregation and neutrophil adherence to both fibrinogen-coated surfaces and confluent cultures of HUVEC. These processes are blocked by CD11b-specific inhibitors, including neutrophil-inhibitory factor and mAbs to CD11b. These observations may help explain the etiology of so-called fat embolism wherein trauma-induced release of fatty material causes pulmonary neutrophil accumulation and the development of acute respiratory distress.

Lipids and the immune response

The effects of fatty acids on immune responses have been studied since the early 1970s, but much controversy still remains. The present review examines recent studies in both animals and in humans, and highlights some new and exciting ideas concerning the mechanism by which fatty acids may affect immune responses in both normal and pathological situations, an area which is likely to progress rapidly over the next few years.