NF-kappa B inhibition by omega -3 fatty acids modulates LPS-stimulated macrophage TNF-alpha transcription

Lipopolysaccharide-stimulated RAW 264.7 macrophage inducible nitric oxide synthase and nitric oxide production is decreased by an omega-3 fatty acid lipid emulsion

BACKGROUND

Omega-3 fatty acids (omega-3 FA) have been demonstrated to have anti-inflammatory properties, postulated to occur through several principal mechanisms, including (1) displacement of arachidonic acid from the cellular membrane; (2) shifting of prostaglandin E(2) and leukotriene B(4) production; and (3) molecular level alterations including decreased activation of nuclear factor kappa B and activator protein-1. An additional regulator that is likely associated is the production of nitric oxide (NO) by nitric oxide synthetase. NO is a short-lived free radical involved in many biological functions. However, excessive NO production can lead to complications, suggesting that decreased NO production is a potential target for some inflammatory diseases. We hypothesized that pretreating with an omega-3 FA lipid emulsion would decrease the production of NO in macrophages and that this effect would occur through alterations in inducible nitric oxide synthetase (iNOS).

MATERIALS AND METHODS

Greiss reagent was used to assess NO production in RAW 264.7 macrophages following omega-3 or omega-6 FA treatment alone or in combination with lipopolysaccharide (LPS) stimulation for 12 h/24 h. iNOS levels were determined by Western blot. Tumor necrosis factor-alpha levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Following LPS-stimulation, omega-3 FA pretreatment at 12 and 24 h produced significantly less NO (P < 0.05) compared to omega-6 FA or media-only conditions. omega-3 FA pretreatment at 12 and 24 h also had less iNOS protein expression compared to omega-6 FA or media-only conditions. Tumor necrosis factor-alpha production was significantly decreased with omega-3 FA treatment compared to omega-6 FA treatment (P < 0.05) after 24 h LPS stimulation.

CONCLUSION

These experiments demonstrate that, in addition to other anti-inflammatory effects, omega-3 FA lipid emulsions also significantly lower NO production in LPS-stimulated macrophages through altered iNOS protein expression.

Alterations in immune response and PPAR/LXR regulation in cystic fibrosis macrophages

BACKGROUND

Cystic fibrosis (CF) is characterized by an excessive inflammatory response in epithelial cells and macrophages. In CF mice, lung inflammation can be abrogated by oral treatment with docosahexaenoic acid (DHA). Since PPARs and LXRs are important regulators of inflammation and fatty acid metabolism in macrophages, we hypothesized that these pathways are dysregulated in CF macrophages and are corrected with DHA treatment.

METHODS

Peritoneal macrophages were obtained from wild type and cftr(-/-) mice. LPS induced cytokine secretion and NFkappaB activity were analyzed with and without oral DHA treatment. The expression and activity of PPARalpha,gamma, delta and LXRalpha were analyzed by RT-PCR and EMSA.

RESULTS

LPS induced TNFalpha and IL-6 secretion and NFkappaB p65 activity were increased in CF macrophages. This was associated with low basal PPARgamma expression and attenuated LPS induced induction of PPARdelta, LXRalpha and ABCA1. DHA pretreatment in vivo decreased TNFalpha secretion and p65 activity, and increased PPARalpha and gamma expression and function. The effects of DHA could be reproduced by PPAR agonists and blocked by a PPARalpha antagonist.

CONCLUSION

Impaired regulation of nuclear receptors may contribute to the abnormal LPS induced signaling in CF macrophages and is reversed by DHA.

The opposing effects of n-3 and n-6 fatty acids

Polyunsaturated fatty acids (PUFAs) can be classified in n-3 fatty acids and n-6 fatty acids, and in westernized diet the predominant dietary PUFAs are n-6 fatty acids. Both types of fatty acids are precursors of signaling molecules with opposing effects, that modulate membrane microdomain composition, receptor signaling and gene expression. The predominant n-6 fatty acid is arachidonic acid, which is converted to prostaglandins, leukotrienes and other lipoxygenase or cyclooxygenase products. These products are important regulators of cellular functions with inflammatory, atherogenic and prothrombotic effects. Typical n-3 fatty acids are docosahexaenoic acid and eicosapentaenoic acid, which are competitive substrates for the enzymes and products of arachidonic acid metabolism. Docosahexaenoic acid- and eicosapentaenoic acid-derived eicosanoids antagonize the pro-inflammatory effects of n-6 fatty acids. n-3 and n-6 fatty acids are ligands/modulators for the nuclear receptors NFkappaB, PPAR and SREBP-1c, which control various genes of inflammatory signaling and lipid metabolism. n-3 Fatty acids down-regulate inflammatory genes and lipid synthesis, and stimulate fatty acid degradation. In addition, the n-3/n-6 PUFA content of cell and organelle membranes, as well as membrane microdomains strongly influences membrane function and numerous cellular processes such as cell death and survival.

n-3 Fatty acids and cardiovascular disease: actions and molecular mechanisms

Cardiovascular disease and atherosclerosis are a leading cause of morbidity and mortality worldwide. Epidemiological studies and randomized control intervention trials have reported that n-3 fatty acids reduce cardiovascular events. A variety of biologic and molecular effects of n-3 fatty acids can modulate the mechanisms of development and progression of atherosclerosis. These include n-3 fatty acid effects on inflammation, cardiac excitability, platelet function, triglyceride blood levels, blood pressure and the stability of atheroma plaques. The molecular mechanisms are still not fully defined; but might involve changes in membrane fluidity, receptor responses and binding to intracellular receptors regulating gene transcription. Understanding and elucidating these mechanisms is important to development of future strategies for prevention and treatment of cardiovascular disease.

Inhibition of Proliferation by Omega-3 Fatty Acids in Chemoresistant Pancreatic Cancer Cells

BACKGROUND

Pancreatic cancer-gemcitabine (GEM) chemoresistance has been demonstrated to be associated with enhanced NF-kB activation and antiapoptotic protein synthesis. The well-known capacity of omega-3 fatty acids (n-3 FAs) to inhibit NF-kB activation and promote cellular apoptosis has the potential to restore or facilitate gemcitabine chemosensitivity.

METHODS

Four pancreatic cancer cell lines (MIA PaCa-2, BxPC-3, PANC-1, and L3.6), each with distinct basal NF-kB and differing GEM sensitivity profiles, were administered: 100 uM of (1) n-3FA, (2) n-6FA, (3) GEM, (4) n-3FA + GEM, or (5) n-6FA + GEM for 24 and 48 hours. Proliferation was assessed using the WST-1 assay. To define the mechanism(s) of altered proliferation, electron mobility shift assay for NF-kB activity, western blots of phoshoStat3, phosphoIkappaB, and poly(ADP-ribose) polymerase (PARP) cleavage were performed in the MIA PaCa-2 cell line.

RESULTS

All cell lines demonstrated a time/dose-dependent inhibition of proliferation in response to n-3FA. For MIA PaCa-2 cells, n-3FA and n-3FA + GEM treatment resulted in reduction of I-kB phosphorylation and NF-kB activation when compared with n-6FA control. n-3FA and combination treatment also significantly decreased Stat3 phosphorylation, whereas GEM alone had no effect. n-3FAs and n-3FA + GEM groups demonstrated increased PARP cleavage, mirroring NF-kB activity and Stat3 phosphorylation.

CONCLUSIONS

n-3 FA treatment is specifically associated with inhibition of proliferation in these four pancreatic cell lines irrespective of varied gemcitabine resistance. An experimental paradigm to screen for potential contributory mechanism(s) in altered pancreatic cancer cellular proliferation was defined, and using this approach the co-administration of n-3 FA with GEM inhibited GEM-induced NF-kB activation and restored apoptosis in the MIA PaCa-2 cell-line.

Genetic polymorphisms of tumor necrosis factor-alpha modify the association between dietary polyunsaturated fatty acids and fasting HDL-cholesterol and apo A-I concentrations

BACKGROUND

Heterogeneity in circulating lipid concentrations in response to dietary polyunsaturated fatty acids (PUFAs) may be due, in part, to genetic variations. Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that can induce hyperlipidemia and is known to be modulated by dietary PUFAs.

OBJECTIVE

The objective was to determine whether TNF-alpha genotypes modify the association between dietary PUFA intake and serum lipid concentrations.

DESIGN

The study involved 53 men and 56 women aged 42-75 y with type 2 diabetes. Dietary intakes were assessed with the use of a 3-d food record, and blood samples were collected to determine fasting serum lipids. DNA was isolated from blood for genotyping by polymerase chain reaction-restriction fragment length polymorphism for the TNF-alpha -238G-->A and -308G-->A polymorphisms.

RESULTS

PUFA intake was positively associated with serum HDL cholesterol in carriers of the -238A allele (beta = 0.06 +/- 0.03 mmol/L per 1% of energy from PUFAs; P = 0.03), but negatively associated in those with the -238GG genotype (beta = -0.03 +/- 0.01, P = 0.03) (P = 0.004 for interaction). PUFA intake was inversely associated with HDL cholesterol in carriers of the -308A allele (beta = -0.07 +/- 0.02, P = 0.002), but not in those with the -308GG genotype (beta = 0.02 +/- 0.02, P = 0.13) (P = 0.001 for interaction). A stronger gene x diet interaction was observed when the polymorphisms at the 2 positions (-238/-308) were combined (P = 0.0003). Similar effects were observed for apolipoprotein A-I, but not with other dietary fatty acids and serum lipids.

CONCLUSION

TNF-alpha genotypes modify the relation between dietary PUFA intake and HDL-cholesterol concentrations. These findings suggest that genetic variations affecting inflammation may explain some of the inconsistencies between previous studies relating PUFA intake and circulating HDL.

Attenuation of iNOS in an LPS-stimulated macrophage model by omega-3 fatty acids is independent of COX-2 derived PGE2

BACKGROUND

Omega-3 fatty acids (n-3 FA) demonstrate significant anti-inflammatory properties thought to occur through three principal mechanisms; (1) displacement of arachidonic acid from the cellular membrane, (2) differential prostaglandin E2 (PGE2) and LTB4 production, and (3) molecular level alterations such as diminished nuclear factor kappa B and AP-1 activation. Recently, n-3 FA have been demonstrated to significantly decrease nitric oxide (NO) production in a lipopolysaccharide (LPS)-stimulated M Phi model. We hypothesized that decreased NO production by n-3 FA occurs through inhibition of cyclooxygenase-2 (COX-2) derived PGE2 and that repletion of the system with PGE2 would obliterate these effects. Selective COX-2 inhibitor (L-748,731) experiments and separate PGE2 repletion studies were used to test this hypothesis.

METHODS

NO production was assessed following 24 h with or without LPS/PGE2 in the presence of n-3 FA, L-748,731 (a selective COX-2 inhibitor), or combination (n-3 FA + L-748,731) treatment. Western blots were used to assess inducible NO synthase protein expression.

RESULTS

Independently or in the presence of LPS, treatment with a COX-2 inhibitor significantly increased NO production compared with control, n-3 FA, and combination treatment. NO production in combination treatment is slightly increased compared to n-3 FA treatment. In control cells treated with LPS, PGE2 repletion resulted in a significant decrease in NO. All other treatment groups repleted with PGE2 demonstrated no significant alterations in NO production. Inducible NO synthase protein expression levels were similar to NO production across all treatments.

CONCLUSION

These experiments disproved our original hypothesis that the decrease in NO production associated with n-3 FA treatment occurs through a COX-2 derived PGE2 dependent mechanism. Eliminating COX-2 derived PGE2 by a selective inhibitor actually increased NO production. Exogenous PGE2 repletion did not restore the system. Therefore, mechanisms other than n-3 FA associated alterations in COX-2 derived PGE2 are likely involved in decreasing NO production in LPS stimulated M Phi.

Arachidonic acid but not eicosapentaenoic acid (EPA) and oleic acid activates NF-kappaB and elevates ICAM-1 expression in Caco-2 cells

In patients with inflammatory bowel disease (IBD), intestinal activation of the transcription factor NF-κB as well as intercellular adhesion molecule (ICAM)-1 expression, which is involved in recruiting leukocytes to the side of inflammation is increased. Moreover, colonic arachidonic acid (ARA) proportions are increased and oleic acid (OA) proportions are decreased. Fish oils are protective in IBD patients however, a side-by-side comparison between effects of fish oils, ARA and OA has not been made. We therefore, compared effects of eicosapentaenoic acid (EPA) versus ARA and OA on ICAM-1 expression in Caco-2 enterocytes. To validate our model we showed that dexamethasone, sulfasalazine and PPARα (GW7647) or PPARγ (troglitazone) agonists significantly lowered ICAM-1 expression. ICAM-1 expression of non-stimulated and cytokine stimulated Caco-2 cells cultured for 22 days with ARA was significant higher as compared to EPA and OA. Furthermore, ARA increased NF-κB activation in a reporter cell-line as compared to EPA. Antibody array analysis of multiple inflammatory proteins particularly showed an increased monocyte chemotactic protein (MCP)-1 and angiogenin production and a decreased interleukin (IL)-6 and IL-10 production by ARA as compared to EPA. Our results showed that ARA but not EPA and OA activates NF-κB and elevates ICAM-1 expression in Caco-2 enterocytes. It suggests that replacement of ARA by EPA or OA in the colon mucosa might have beneficial effects for IBD patients. Finally, we suggest that the pro-inflammatory effects of ARA versus EPA and OA are not related to PPARγ activation and/or eicosanoid formation.

The effects of omega-3 polyunsaturated fatty acids on TNF-alpha and IL-10 secretion by murine peritoneal cells in vitro

Omega-3 polyunsaturated fatty acids (PUFA) affect immune response, partly by affecting cytokine secretion. Omega-3 PUFA decrease tumor necrosis factor (TNF)-alpha secretion by RAW 264.7 macrophages but increase TNF-alpha secretion by primary elicited peritoneal macrophages in vitro. In this study, the effects of omega-3 and omega-6 PUFA on lipopolysaccharide induced TNF-alpha and interleukin (IL)-10 secretion by murine primary resident and elicited peritoneal macrophages and by RAW 264.7 macrophages, were examined in vitro using an enzyme-linked immunosorbent assay. In addition, the effects of dietary omega-3 PUFA on the number of cells secreting these cytokines were examined with enzyme-linked immunospot assay. All cell types secreted more TNF-alpha but similar amounts of IL-10 when incubated with the omega-3 PUFA, eicosapentaenoic acid or docosahexaenoic acid, compared with that when incubated with the omega-6 PUFA, linoleic acid or arachidonic acid. Dietary fish oil did not affect the number of TNF-alpha secreting resident peritoneal macrophages but decreased the number of macrophages secreting IL-10 ex vivo. These results show that dietary omega-3 PUFA and omega-3 PUFA added to cells in vitro increase TNF-alpha secretion by resident peritoneal macrophages, probably by a direct effect on the cells. In contrast, omega-3 PUFA did not affect IL-10 secretion by the cells but decreased the number of cells secreting IL-10 ex vivo, possibly by affecting cell recruitment, maturation or proliferation.

Mechanisms by which fatty acids regulate leucocyte function

Fatty acids (FAs) have been shown to alter leucocyte function and thus to modulate inflammatory and immune responses. In this review, the effects of FAs on several aspects of lymphocyte, neutrophil and macrophage function are discussed. The mechanisms by which FAs modulate the production of lipid mediators, activity of intracellular signalling pathways, activity of lipid-raft-associated proteins, binding to TLRs (Toll-like receptors), control of gene expression, activation of transcription factors, induction of cell death and production of reactive oxygen and nitrogen species are described in this review. The rationale for the use of specific FAs to treat patients with impaired immune function is explained. Substantial improvement in the therapeutic usage of FAs or FA derivatives may be possible based on an improvement in the understanding of the precise molecular mechanisms of action with respect to the different leucocyte types and outcome with respect to the inflammatory responses.

A meta-analysis of the analgesic effects of omega-3 polyunsaturated fatty acid supplementation for inflammatory joint pain

Between 40% and 60% of Americans use complementary and alternative medicine to manage medical conditions, prevent disease, and promote health and well-being. Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) have been used to treat joint pain associated with several inflammatory conditions. We conducted a meta-analysis of 17 randomized, controlled trials assessing the pain relieving effects of omega-3 PUFAs in patients with rheumatoid arthritis or joint pain secondary to inflammatory bowel disease and dysmenorrhea. Meta-analysis was conducted with Cochrane Review Manager 4.2.8. for six separate outcomes using standardized mean differences (SMDs) as a measure of effect size: (1) patient assessed pain, (2) physician assessed pain, (3) duration of morning stiffness, (4) number of painful and/or tender joints, (5) Ritchie articular index, and (6) nonselective nonsteroidal anti-inflammatory drug consumption. Supplementation with omega-3 PUFAs for 3-4 months reduces patient reported joint pain intensity (SMD: -0.26; 95% CI: -0.49 to -0.03, p=0.03), minutes of morning stiffness (SMD: -0.43; 95% CI: -0.72 to -0.15, p=0.003), number of painful and/or tender joints (SMD: -0.29; 95% CI: -0.48 to -0.10, p=0.003), and NSAID consumption (SMD: -0.40; 95% CI: -0.72 to -0.08, p=0.01). Significant effects were not detected for physician assessed pain (SMD: -0.14; 95% CI: -0.49 to 0.22, p=0.45) or Ritchie articular index (SMD: 0.15; 95% CI: -0.19 to 0.49, p=0.40) at 3-4 months. The results suggest that omega-3 PUFAs are an attractive adjunctive treatment for joint pain associated with rheumatoid arthritis, inflammatory bowel disease, and dysmenorrhea.

Omega-3 fatty acids alleviate chemically induced acute hepatitis by suppression of cytokines

Cytokines such as tumor necrosis factor alpha (TNF-alpha) are key factors in liver inflammation. Supplementation with essential omega-3 polyunsaturated fatty acids (n-3 PUFA) has been demonstrated to lower TNF-alpha and IL-1 production in mononuclear cells. An inflammation-dampening effect has been observed with increased omega-3 fatty acid supplementation in several inflammatory diseases. In this study, we used the transgenic fat-1 mouse, expressing a Caenorhabditis elegans desaturase endogenously forming n-3 PUFA from n-6 PUFA, to analyze the effect of an increased n-3 PUFA tissue status in the macrophage-dependent acute D-galactosamine/lipopolysaccaride (D-GalN/LPS) hepatitis model. We show less severe inflammatory liver injury in fat-1 mice with a balanced n-6/n-3 PUFA ratio as evidenced by reduced serum alanine aminotransferase levels and less severe histological liver damage. This decreased inflammatory response was associated with decreased plasma TNF-alpha levels and with reduced hepatic gene expression of TNF-alpha, IL-1beta, IFN-gamma and IL-6 in fat-1 mice, leading to a decreased rate of apoptosis in livers from fat-1 animals, as measured by DAPI-staining.

CONCLUSION

The results of this study offer evidence for an inflammation dampening effect of omega-3 polyunsaturated fatty acids in the context of liver inflammation.

Essential polyunsaturated fatty acids, inflammation, atherosclerosis and cardiovascular diseases

Atherosclerosis is the primary cause of coronary and cardiovascular diseases (CVD). Epidemiological studies have revealed several important environmental (especially nutritional) factors associated with atherosclerosis. However, progress in defining the cellular and molecular interactions involved has been hindered by the etiological complexity of the disease. Nevertheless, our understanding of CVD has improved significantly over the past decade owing to the availability of new randomized trial data. In particular, the failure of antioxidant and anti-inflammatory treatments to consistently reduce the rate of CVD complications suggests that theories of atherosclerosis may have considerably exaggerated the importance of oxidized lipoprotein and vascular inflammation. In that context, one new and basic question is whether the biology of essential dietary lipids may help us understand the role of the inflammatory process in CVD. Essential dietary lipids of the omega-6 and omega-3 families are the precursors of major mediators of inflammation such as eicosanoids that regulate the production of inflammatory cytokines and the expression of some major inflammation genes. On the other hand, non-essential lipids (omega-9 and saturated fatty acids) interfere with biological activities of essential lipids. Finally, essential omega-3 and omega-6 fatty acids have different, often antagonistic, effects on inflammation, and their effects can vary according to the type of cells and target organs involved, as well as their respective amounts in the diet. Because of the extreme complexity in the etiology of CVD, the best strategy may be to monitor the main features of dietary patterns, such as the Mediterranean diet, that are known to be associated with a low prevalence of both CVD and chronic inflammatory diseases.

Comparative toxicity of fatty acids on a macrophage cell line (J774)

In the present study, the cytotoxicity of palmitic, stearic, oleic, linoleic, arachidonic, docosahexaenoic and eicosapentaenoic acids on a macrophage cell line (J774) was investigated. The induction of toxicity was investigated by changes in cell size, granularity, membrane integrity, DNA fragmentation and phosphatidylserine externalization by using flow cytometry. Fluorescence microscopy was used to determine the type of cell death (Acridine Orange/ethidium bromide assay). The possible mechanisms involved were examined by measuring mitochondrial depolarization, lipid accumulation and PPARgamma (peroxisome-proliferator-activated receptor gamma) activation. The results demonstrate that fatty acids induce apoptosis and necrosis of J774 cells. At high concentrations, fatty acids cause macrophage death mainly by necrosis. The cytotoxicity of the fatty acids was not strictly related to the number of double bonds in the molecules: palmitic acid>docosahexaenoic acid>stearic acid=eicosapentaenoic acid=arachidonic acid>oleic acid>linoleic acid. The induction of cell death did not involve PPARgamma activation. The mechanisms of fatty acids to induce cell death involved changes in mitochondrial transmembrane potential and intracellular neutral lipid accumulation. Fatty acids poorly incorporated into triacylglycerol had the highest toxicity.

A priori dietary omega-3 lipid supplementation results in local pancreatic macrophage and pulmonary inflammatory response attenuation in a model of experimental acute edematous pancreatitis (AEP)

BACKGROUND

Acute pancreatitis is often complicated by multiorgan dysfunction, which is postulated to occur in part by macrophage infiltration into the pancreas. Eicosapentaenoic acid (EPA), an omega-3 fatty acid, is the principal biologic component of fish oil and has clinically and experimentally been demonstrated to be anti-inflammatory. We hypothesized that dietary EPA supplementation before the induction of pancreatitis would attenuate both M-mediated local pancreatic and systemic pulmonary inflammatory response in an in vivo model of acute edematous pancreatitis (AEP).

METHODS

Male Sprague-Dawley (SD) rats were pretreated 2 times per day with oral gavage with EPA (omega-3 fatty acid; 5 mg/kg/dose) or omega-6 fatty acid control (5 mg/kg/dose) or saline (equal volume) for 2 weeks. AEP was induced in omega-3, omega-6, and saline pretreated rats by 5 hourly subcutaneous (SC) injections of cerulein. Pancreas, lung, and serum were harvested 3 hours after the last cerulein injection. Severity of pancreatitis was confirmed by serum amylase and by histopathologic score. Pancreatic macrophage infiltration was assessed by confocal fluorescent microscopy, and pulmonary leukocyte respiratory burst (LRB) analysis was performed on mononuclear cells obtained from bronchioalveolar lavage (BAL).

RESULTS

All animals demonstrated acute pancreatitis through hyperamylasemia and histopathologic examination. Confocal analysis demonstrated significantly lower macrophage infiltration, and BAL analysis by flow cytometry demonstrated significantly lower (p < .05) LRB in the omega-3-treated group compared with the omega-6 and the saline pancreatitis group.

CONCLUSIONS

Attenuation of both pancreatic MPhi inflammatory response and pulmonary leukocyte respiratory burst in AEP by EPA supports further investigation into the potential role for EPA dietary supplementation in the progression of pancreatitis-associated sequelae.

Omega-3 fatty acids for the treatment of cancer cachexia: issues in designing clinical trials of dietary supplements

Complementary and alternative medicine (CAM) is increasingly popular, despite the limited evidence of the efficacy and safety of some forms of CAM. Cancer patients often turn to CAM therapies for the relief of treatment- induced side-effects and comorbidities. Cancer-associated weight loss commonly results in decreased functional status, life expectancy, and quality of life. Despite the high morbidity and mortality associated with cancer cachexia, mainstream treatments do not sustain weight. Although nutritional supplements are commonly used, many of these have not been tested in clinical trials. The issues faced in dietary supplement research differ from those in pharmaceutical drug trials. These include problems with standardization, contamination, and compliance documentation. A double-blind, randomized, placebo-controlled trial is proposed to evaluate the efficacy and safety of fish oil supplementation for the treatment of cachexia in pancreatic cancer patients. The primary outcome measure will be lean body mass; secondary outcomes include functional status and quality of life. The methodology of the clinical trial is reviewed here and the unique problems faced by investigators in designing studies of dietary supplements are discussed.

n-3 fatty acids and gene expression

Accumulating evidence in both humans and animal models clearly indicates that a group of very-long-chain polyunsaturated fatty acids, the n-3 fatty acids (or omega-3), have distinct and important bioactive properties compared with other groups of fatty acids. n-3 Fatty acids are known to reduce many risk factors associated with several diseases, such as cardiovascular diseases, diabetes, and cancer. The mechanisms whereby n-3 fatty acids affect gene expression are complex and involve multiple processes. As examples, n-3 fatty acids regulate 2 groups of transcription factors, such as sterol-regulatory-element binding proteins and peroxisome proliferator-activated receptors, that are critical for modulating the expression of genes controlling both systemic and tissue-specific lipid homeostasis. Modulation of specific genes by n-3 fatty acids and cross-talk between these genes are responsible for many effects of n-3 fatty acids.

Intestinal anti-inflammatory activity of combined quercitrin and dietary olive oil supplemented with fish oil, rich in EPA and DHA (n-3) polyunsaturated fatty acids, in rats with DSS-induced colitis

BACKGROUND AND AIMS

Previous studies have described the intestinal anti-inflammatory effects exerted by the bioflavonoid quercitrin (QR) and by an n-3 polyunsaturated fatty acids (PUFA)-enriched diet in experimental models of rat colitis. The aim of the present study was to test if the combination of both treatments would result in an improvement in the intestinal anti-inflammatory effect achieved separately.

METHODS

Colitis was induced in female Wistar rats by incorporating dextran sodium sulfate (DSS) in drinking water at 5% (w/v) for 5 days and at 2% (w/v) for the following 10 days. Five groups of rats (n=10) were used: two of them received an olive-oil-based diet with fish oil, rich in n-3 PUFA (FO diet) for 2 weeks before colitis induction and until the end of the experiment, and one of those also was administered daily QR (1mg/kg, PO), starting when DSS concentration was changed. DSS colitis was induced in other two groups fed with standard rat diet, one of them being administered QR as before. A non-colitic group fed standard diet was also included. After that period, the rats were sacrificed and colonic damage was assessed both histologically and biochemically.

RESULTS

The concurrent administration of FO diet and QR exhibited an intestinal anti-inflammatory effect, as evidenced by a significant improvement of all biochemical parameters of colonic inflammation assayed in comparison with non-treated colitic rats. Thus, both colonic myeloperoxidase (MPO) and alkaline phosphatase (AP) activities were significantly reduced compared with untreated colitic rats. In addition, a complete restoration of colonic glutathione content, which was depleted as a consequence of the colonic insult, was obtained in rats treated with QR plus FO diet; this content was even higher than that obtained when colitic rats were treated with FO diet alone. When compared with the control colitic group, the combined treatment was also associated with a lower colonic nitric oxide synthase and cyclooxygenase-2 expression as well as with a significant reduction in different colonic proinflammatory mediators assayed, i.e. leukotriene B(4), tumor necrosis factor alpha and interleukin 1beta, showing a significantly greater inhibitory effect of the latter in comparison with rats receiving FO diet without the flavonoid.

CONCLUSIONS

These results support the potential synergism between the administration of the flavonoid and the incorporation of olive oil and n-3 PUFA to the diet for the treatment of these intestinal inflammatory disorders.

Inflammation and conjugated linoleic acid: mechanisms of action and implications for human health

Data from a number of studies and trials have shown that different conjugated linoleic acids (CLA's) may produce beneficial effects on cancer, atherosclerosis, hypertension, diabetes and changes in body composition. Despite the increasing knowledge about CLA's implications on health, the mechanism of action of these fatty acids is not completely understood. Moreover, human studies indicate that some of these beneficial effects are considerably less evident than anticipated from mice studies, while the efficacy and safety of dietary supplements containing CLA have been questioned in some intervention trials. Recently, it has been suggested that the anti-carcinogenic and anti-atherosclerosis effects of CLA's stem from its anti-inflammatory properties. Because inflammatory responses are associated with the pathophysiology of many diseases, including obesity and the metabolic syndrome, the investigation in this area is of growing interest in recent years.

Dietary polyunsaturated fatty acids in asthma- and exercise-induced bronchoconstriction

Despite progress that has been made in the treatment of asthma, the prevalence and burden of this disease has continued to increase. While pharmacological treatment of asthma is usually highly effective, medications may have significant side effects or exhibit tachyphylaxis. Alternative therapies for treatment that reduce the dose requirements of pharmacological interventions would be beneficial, and could potentially reduce the public health burden of this disease. Ecological and temporal data suggest that dietary factors may have a role in recent increases in the prevalence of asthma. A possible contributing factor to the increased incidence of asthma in Western societies may be the consumption of a proinflammatory diet. In the typical Western diet, 20- to 25-fold more omega (n)-6 polyunsaturated fatty acids (PUFA) than n-3 PUFA are consumed, which promotes the release of proinflammatory arachidonic acid metabolites (leukotrienes and prostanoids). This review will analyze the evidence for the health effects of n-3 PUFA in asthma- and exercise-induced bronchoconstriction (EIB). While clinical data evaluating the effect of omega-3 fatty acid supplementation in asthma has been equivocal, it has recently been shown that fish oil supplementation, rich in n-3 PUFA, reduces airway narrowing, medication use, and proinflammatory mediator generation in nonatopic elite athletes with EIB. These findings are provocative and suggest that dietary fish oil supplementation may be a viable treatment modality and/or adjunct therapy in asthma and EIB.

Nutritional influences on inflammation and type 2 diabetes risk

There is a clear role for inflammation in the development of type 2 diabetes and its associated co-morbidities. Circulating inflammatory markers such as C-reactive protein, sialic acid, and interleukin- 6 are all significant independent predictors of disease. A number of nutritional components are hypothesized to modulate inflammation, and hence impact on disease risk. The most extensively studied nutrients are the long-chain n-3 polyunsaturated fatty acids. However, evidence is also emerging with respect to whole grain or low glycemic index foods and antioxidant vitamins. Obesity, resulting from long-term dietary energy excess, is also strongly linked to raised inflammatory status and type 2 diabetes. To date, much of the evidence for the effect of nutrients or foods on disease risk has been based on epidemiological associations. However, the links among diet, inflammation, and type 2 diabetes are supported by some data from human dietary intervention trials and/or mechanistic studies in animals. Further research is required to quantify the precise role and refine the evidence base. However, the proposed "anti-inflammatory" strategies to tackle type 2 diabetes are broadly consistent with current public health nutrition guidelines: to achieve and maintain a healthy weight, to reduce saturated fat, to increase the proportion of less refined forms of carbohydrate, and to increase intake of fruits and vegetables.

Experimental studies defining omega-3 fatty acid antiinflammatory mechanisms and abrogation of tumor-related syndromes

Clinical and experimental evidence has supported a benefit for the inclusion of fish oils (a primary source of omega-3 fatty acids) as a component of a normal healthy diet. Polyunsaturated omega-3 fatty acids have been demonstrated to be of benefit in a number of inflammation-associated disease states, including atherosclerosis, autoimmune disorders, malignancy, and sepsis. The beneficial effects of omega-3 fatty acids are thought to occur through the postulated antiinflammatory actions of omega-3 fats; however, the specific mechanism(s) of action has not been completely defined. In this review, we discuss the recent progress made in our laboratory on defining the mechanisms of omega-3 fatty acids activity.

Mechanisms of omega-3 fatty acid-induced growth inhibition in MDA-MB-231 human breast cancer cells

The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), inhibit the growth of human breast cancer cells in animal models and cell lines, but the mechanism by which this occurs is not well understood. In order to explore possible mechanisms for the modulation of breast cancer cell growth by omega-3 fatty acids, we examined the effects of EPA and DHA on the human breast cancer cell line MDA-MB-231. Omega-3 fatty acids (a combination of EPA and DHA) inhibited the growth of MDA-MB-231 cells by 30-40% (p<0.05) in both the presence and absence of linoleic acid, an essential omega-6 fatty acid. When provided individually, DHA was more potent than EPA in inhibiting the growth of MDA-MB-231 cells (p<0.05). EPA and DHA treatment decreased tumor cell proliferation (p<0.05), as estimated by decreased [methyl-(3)H]-thymidine uptake and expression of proliferation-associated proteins (proliferating cell nuclear antigen, PCNA, and proliferation-related kinase, PRK). In addition, EPA and DHA induced apoptosis, as indicated by a loss of mitochondrial membrane potential, increased caspase activity and increased DNA fragmentation (p<0.05). Cells incubated with omega-3 fatty acids demonstrated decreased Akt phosphorylation, as well as NFkappaB DNA binding activity (p<0.05). The results of this study indicate that omega-3 fatty acids decrease cell proliferation and induce apoptotic cell death in human breast cancer cells, possibly by decreasing signal transduction through the Akt/NFkappaB cell survival pathway.

10t,12c-conjugated linoleic acid inhibits lipopolysaccharide-induced cyclooxygenase expression in vitro and in vivo

Previous data demonstrated that conjugated linoleic acid (CLA) reduced eicosanoid release from select organs. We hypothesized that one active CLA isomer was responsible for the reduced prostaglandin release and that the mechanism was through the inhibition of inducible cyclooxygenase-2 (COX-2). Here, we examined the effects of 10t,12c-CLA and 9c,11t-CLA on COX-2 protein/mRNA expression, prostaglandin E(2) (PGE(2)) production, and the mechanism by which CLA affects COX-2 expression and prostaglandin release. The COX-2 protein expression level was inhibited 80% by 10t, 12c-CLA and 26% by 9c,11t-CLA at 100 microM in vitro. PGE(2) production was decreased from 5.39 to 1.12 ng/2 x 10(6) cells by 10t,12c-CLA and from 5.7 to 4.5 ng/2 x 10(6) cells by 9c,11t-CLA at 100 microM. Mice fed 10t,12c-CLA but not 9c,11t-CLA were found to have a 34% decrease in COX-2 protein and a 43% reduction of PGE(2) release in the lung. 10t,12c-CLA reduced COX-2 mRNA expression level by 30% at 100 microM in vitro and by 30% in mouse lung in vivo. Reduced COX-2 mRNA was attributable to an inhibition of the nuclear factor kappaB (NF-kappaB) pathway by 10t,12c-CLA. These data suggested that the inhibition of NF-kappaB was one of the mechanisms for the reduced COX-2 expression and PGE(2) release by 10t,12c-CLA.

Omega-3 fatty acids and anorexia

PURPOSE OF REVIEW

To review the mechanisms of action of omega-3 fatty acids and their role in the brain, as well as their therapeutic implications in anorexia.

RECENT FINDINGS

Recent studies have demonstrated that omega-3 fatty acids modulate changes in the concentrations and actions of several orexigenic and anorexigenic neuropeptides in the brain, including neuropeptide Y, alpha-melanocyte stimulating hormone and the neurotransmitters serotonin and dopamine. In patients with acute and chronic inflammatory conditions, low tissue concentrations of omega-3 fatty acids and high concentrations of proinflammatory cytokines are found, in association with anorexia and decreased food intake. The data suggest that omega-3 fatty acid supplementation suppresses proinflammatory cytokine production and improves food intake by normalizing hypothalamic orexigenic peptides and neurotransmitters.

SUMMARY

Based on current data, omega-3 fatty acid supplementation has a role in the treatment of anorexia by stimulating the production and release of orexigenic neurotransmitters in food intake regulatory nuclei in the hypothalamus.

n-3 fatty acids, inflammation, and immunity--relevance to postsurgical and critically ill patients

Excessive or inappropriate inflammation and immunosuppression are components of the response to surgery, trauma, injury, and infection in some individuals and these can lead, progressively, to sepsis and septic shock. The hyperinflammation is characterized by the production of inflammatory cytokines, arachidonic acid-derived eicosanoids, and other inflammatory mediators, while the immunosuppression is characterized by impairment of antigen presentation and of T helper cell type-1 responses. Long-chain n−3 FA from fish oil decrease the production of inflammatory cytokines and eicosanoids. They act both directly (by replacing arachidonic acid as an eicosanoid substrate and by inhibiting arachidonic acid metabolism) and indirectly (by altering the expression of inflammatory genes through effects on transcription factor activation). Thus, long-chain n−3 FA are potentially useful anti-inflammatory agents and may be of benefit in patients at risk of developing sepsis. As such, an emerging application of n−3 FA is in surgical or critically ill patients where they may be added to parenteral or enteral formulas. Parenteral or enteral nutrition including n−3 FA appears to preserve immune function better than standard formulas and appears to partly prevent some aspects of the inflammatory response. Studies to date are suggestive of clinical benefits from these approaches, especially in postsurgical patients.

Omega-3 Fatty acids and airway hyperresponsiveness in asthma

Despite the progress that has been made in the treatment of asthma, the prevalence and burden of this disease has continued to increase. Exercise is a powerful trigger of asthma symptoms and reversible airflow obstruction and may result in the avoidance of physical activity by patients with asthma, resulting in detrimental consequences to their health. Approximately 90% of patients with asthma are hyperresponsive to exercise and experience exercise-induced bronchoconstriction (EIB). While pharmacologic treatment of asthma is usually highly effective, medications often have significant side-effects or exhibit tachyphylaxis. Alternative therapies for treatment (complementary medicine) that reduce the dose requirements of pharmacologic interventions would be beneficial, and could potentially reduce the public health burden of this disease. There is accumulating evidence that dietary modification has potential to influence the severity of asthma and reduce the prevalence and incidence of this condition. A possible contributing factor to the increased incidence of asthma in Western societies may be the consumption of a proinflammatory diet. In the typical Western diet, 20- to 25-fold more omega- 6 polyunsaturated fatty acids (PUFA) than omega-3 PUFA are consumed, which causes the release of proinflammatory arachidonic acid metabolites (leukotrienes and prostanoids). This review analyzes the existing literature on omega-3 PUFA supplementation as a potential modifier of airway hyperresponsiveness in asthma and includes studies concerning the efficacy of omega-3 PUFA supplementation in EIB. While clinical data evaluating the effect of omega-3 PUFA supplementation in asthma has been equivocal, it has recently been shown that pharmaceutical-grade fish oil (omega-3 PUFA) supplementation reduces airway hyperresponsiveness after exercise, medication use, and proinflammatory mediator generation in nonatopic elite athletes with EIB. These findings are provocative and suggest that dietary omega-3 PUFA supplementation may be a viable treatment modality and/or adjunct therapy in airway hyperresponsiveness. Further studies are needed to confirm these results and understand their mechanism of action.

NF-kappaB mediates proteolysis-inducing factor induced protein degradation and expression of the ubiquitin-proteasome system in skeletal muscle

Loss of skeletal muscle in cancer cachexia has a negative effect on both morbidity and mortality. The role of nuclear factor-κB (NF-κB) in regulating muscle protein degradation and expression of the ubiquitin–proteasome proteolytic pathway in response to a tumour cachectic factor, proteolysis-inducing factor (PIF), has been studied by creating stable, transdominant-negative, muscle cell lines. Murine C₂C₁₂ myoblasts were transfected with plasmids with a CMV promoter that had mutations at the serine phosphorylation sites required for degradation of I-κBα, an NF-κB inhibitory protein, and allowed to differentiate into myotubes. Proteolysis-inducing factor induced degradation of I-κBα, nuclear accumulation of NF-κB and an increase in luciferase reporter gene activity in myotubes containing wild-type, but not mutant, I-κBα proteins. Proteolysis-inducing factor also induced total protein degradation and loss of the myofibrillar protein myosin in myotubes containing wild-type, but not mutant, plasmids at the same concentrations as those causing activation of NF-κB. Proteolysis-inducing factor also induced increased expression of the ubiquitin–proteasome pathway, as determined by ‘chymotrypsin-like’ enzyme activity, the predominant proteolytic activity of the β-subunits of the proteasome, protein expression of 20S α-subunits and the 19S subunits MSS1 and p42, as well as the ubiquitin conjugating enzyme, E2_14k, in cells containing wild-type, but not mutant, I-κBα. The ability of mutant I-κBα to inhibit PIF-induced protein degradation, as well as expression of the ubiquitin–proteasome pathway, confirms that both of these responses depend on initiation of transcription by NF-κB.

Inflammation: Nutritional, Botanical, and Mind-body Influences

Chronic inflammation is becoming an important risk factor to identify in regard to inhibiting disease onset and its progression. Nutritional science attempted to improve health by manipulating fats so that we could consume "healthy" nonsaturated fats while simultaneously allowing foods to have a longer shelf-life. However, despite our good intentions, trans-fats and partially hydrogenated oils have been found to promote inflammation and adversely affect health. This article reviews how essential fatty acids, the ratio of omega-3 to omega-6 fatty acids, glycemic load, the Mediterranean diet, specific foods and botanicals, and the mind-body relation influence the inflammatory cascade.

Induction of proteasome expression in skeletal muscle is attenuated by inhibitors of NF-kappaB activation

The potential for inhibitors of nuclear factor-κB (NF-κB) activation to act as inhibitors of muscle protein degradation in cancer cachexia has been evaluated both in vitro and in vivo. Activation of NF-κB is important in the induction of proteasome expression and protein degradation by the tumour factor, proteolysis-inducing factor (PIF), since the cell permeable NF-κB inhibitor SN50 (18 μM) attenuated the expression of 20S proteasome α-subunits, two subunits of the 19S regulator MSS1 and p42, and the ubiquitin-conjugating enzyme, E2_14k, as well as the decrease in myosin expression in murine myotubes. To assess the potential therapeutic benefit of NF-κB inhibitors on muscle atrophy in cancer cachexia, two potential inhibitors were employed; curcumin (50 μM) and resveratrol (30 μM). Both agents completely attenuated total protein degradation in murine myotubes at all concentrations of PIF, and attenuated the PIF-induced increase in expression of the ubiquitin–proteasome proteolytic pathway, as determined by the ‘chymotrypsin-like’ enzyme activity, proteasome subunits and E2_14k. However, curcumin (150 and 300 mg kg⁻¹) was ineffective in preventing weight loss and muscle protein degradation in mice bearing the MAC16 tumour, whereas resveratrol (1 mg kg⁻¹) significantly attenuated weight loss and protein degradation in skeletal muscle, and produced a significant reduction in NF-κB DNA-binding activity. The inactivity of curcumin was probably due to a low bioavailability. These results suggest that agents which inhibit nuclear translocation of NF-κB may prove useful for the treatment of muscle wasting in cancer cachexia.

Metabolic Syndrome, a Cardiovascular Disease Risk Factor: Role of Adipocytokines and Impact of Diet and Physical Activity

The metabolic syndrome comprises an array of cardiovascular disease (CVD) risk factors such as abdominal obesity, dyslipidemia, hypertension, and glucose intolerance. Insulin resistance and/or increased abdominal (visceral) obesity have been suggested as potential etiological factors. More recently, increasing evidence has associated insulin resistance and subclinical inflammation involving cytokines derived from adipose tissue, or adipocytokines. Despite the fact that precise mechanisms have yet to be established, there is a significant role for both diet and physical activity to improve the many factors associated with the metabolic syndrome, including modulation of various adipocytokines. Although both diet and physical activity have been studied for their ability to modify cytokines in more traditional inflammatory conditions, such as rheumatoid arthritis, they have been less studied in relation to inflammation as an underlying cause of the metabolic syndrome and/or CVD. A more thorough understanding of the clustering of metabolic abnormalities and their underlying etiology will help to define diet and physical activity guidelines for preventing and treating the metabolic syndrome, an important aspect of CVD prevention. This paper will address potential underlying causes of the metabolic syndrome, with a focus on the putative mechanistic role of adipocytokines, and will discuss the impact of diet and physical activity on the metabolic syndrome. Key words: insulin resistance syndrome, obesity, adipose tissue, skeletal muscle, cytokines, TNF-α, IL-6, PAI-1, inflammation, nutrition, exercise

Fatty acid regulation of gene transcription

Dietary fat has a dual role in human physiology: a) it functions as a source of energy and structural components for cells; b) it functions as a regulator of gene expression that impacts lipid, carbohydrate, and protein metabolism, as well as cell growth and differentiation. Fatty acid effects on gene expression are cell-specific and influenced by fatty acid structure and metabolism. Fatty acids interact with the genome through several mechanisms. They regulate the activity or nuclear abundance of several transcription factors, including PPAR, LXR, HNF-4, NFkappaB, and SREBP. Fatty acids or their metabolites bind directly to specific transcription factors to regulate gene transcription. Alternatively, fatty acids indirectly act on gene expression through their effects on a) specific enzyme-mediated pathways, such as cyclooxygenase, lipoxygenase, protein kinase C, or sphingomyelinase signal transduction pathways; or b) pathways that involve changes in membrane lipid/lipid raft composition that affect G-protein receptor or tyrosine kinase-linked receptor signaling. Further definition of these fatty acid-regulated pathways will provide insight into the role dietary fat plays in human health and the onset and progression of several chronic diseases, like coronary artery disease and atherosclerosis, dyslipidemia and inflammation, obesity and diabetes, cancer, major depressive disorders, and schizophrenia.

Effects of n-3 Fatty Acids on Serum Interleukin-6, Tumour Necrosis Factor-α and Soluble Tumour Necrosis Factor Receptor p55 in Active Rheumatoid Arthritis

We investigated the effects of a low n-6 fatty acid (FA) diet supplemented with fish oil on serum pro-inflammatory cytokine concentrations and clinical variables in patients with active rheumatoid arthritis (RA). Sixty patients were randomly assigned to receive a diet low in n-6 FAs and n-3 FAs supplement (fish oil group), a diet low in n-6 FAs and placebo (placebo group), or no special diet or intervention (control group). Serum cytokines and clinical and biochemical variables were evaluated at baseline and various timepoints. At week 18 the fish oil group had significant reductions in linoleic acid, C-reactive protein (CRP) and soluble tumour necrosis factor receptor p55 (sTNF-R p55), and significant elevations in eicosapentaenoic acid and docosahexaenoic acid compared with baseline. There were no significant differences in the clinical variables between the three groups. At week 24 there were significant reductions in interleukin-6 and TNF-α in the fish oil and placebo groups. Supplementation with n-3 FA and a low n-6 FA intake decreased serum sTNF-R p55 and CRP levels in patients with RA.

Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer

BACKGROUND

Laboratory studies have shown that n-3 fatty acids inhibit and n-6 fatty acids stimulate prostate tumor growth, but whether the dietary intake of these fatty acids affects prostate cancer risk in humans remains unclear.

OBJECTIVE

We prospectively evaluated the association between intakes of alpha-linolenic (ALA; 18:3n-3), eicosapentaenoic (EPA; 20:5n-3), docosahexaenoic (DHA; 22:6n-3), linoleic (LA; 18:2n-6), and arachidonic (AA; 20:4n-6) acids and prostate cancer risk.

DESIGN

A cohort of 47 866 US men aged 40-75 y with no cancer history in 1986 was followed for 14 y.

RESULTS

During follow-up, 2965 new cases of total prostate cancer were ascertained, 448 of which were advanced prostate cancer. ALA intake was unrelated to the risk of total prostate cancer. In contrast, the multivariate relative risks (RRs) of advanced prostate cancer from comparisons of extreme quintiles of ALA from nonanimal sources and ALA from meat and dairy sources were 2.02 (95% CI: 1.35, 3.03) and 1.53 (0.88, 2.66), respectively. EPA and DHA intakes were related to lower prostate cancer risk. The multivariate RRs of total and advanced prostate cancer from comparisons of extreme quintiles of the combination of EPA and DHA were 0.89 (0.77, 1.04) and 0.74 (0.49, 1.08), respectively. LA and AA intakes were unrelated to the risk of prostate cancer. The multivariate RR of advanced prostate cancer from a comparison of extreme quintiles of the ratio of LA to ALA was 0.62 (0.45, 0.86).

CONCLUSIONS

Increased dietary intakes of ALA may increase the risk of advanced prostate cancer. In contrast, EPA and DHA intakes may reduce the risk of total and advanced prostate cancer.

Cyclooxygenase-1-dependent prostaglandin synthesis modulates tumor necrosis factor-alpha secretion in lipopolysaccharide-challenged murine resident peritoneal macrophages

Comprehensive studies of prostaglandin (PG) synthesis in murine resident peritoneal macrophages (RPM) responding to bacterial lipopolysaccharide (LPS) revealed that the primary PGs produced by RPM were prostacyclin and PGE(2). Detectable increases in net PG formation occurred within the first hour, and maximal PG formation had occurred by 6-10 h after LPS addition. Free arachidonic acid levels rose and peaked at 1-2 h after LPS addition and then returned to baseline. Cyclooxygenase-2 (COX-2) and microsomal PGE synthase levels markedly increased upon exposure of RPM to LPS, with the most rapid increases in protein expression occurring 2-6 h after addition of the stimulus. RPM constitutively expressed high levels of COX-1. Studies using isoform-selective inhibitors and RPM from mice bearing targeted deletions of ptgs-1 and ptgs-2 demonstrated that COX-1 contributes significantly to PG synthesis in RPM, especially during the initial 1-2 h after LPS addition. Selective inhibition of either COX isoform resulted in increased secretion of tumor necrosis factor-alpha (TNF-alpha); however, this effect was much greater with the COX-1 than with the COX-2 inhibitor. These results demonstrate autocrine regulation of TNF-alpha secretion by endogenous PGs synthesized primarily by COX-1 in RPM and suggest that COX-1 may play a significant role in the regulation of the early response to endotoxemia.

The role of fish oil/omega-3 fatty acids in the treatment of IgA nephropathy

Beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFA) have been reported in recent epidemiologic studies and randomized clinical trials in a variety of cardiovascular and autoimmune diseases. Fish and marine oils are the most abundant and convenient sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the two major n-3 fatty acids that serve as substrates for cyclooxygenase and lipoxygenase pathways leading to less potent inflammatory mediators than those produced through the n-6 PUFA substrate, arachidonic acid. N-3 PUFA can also suppress inflammatory and/or immunologic responses through eicosanoid-independent mechanisms. Although the pathophysiology of IgA nephropathy is incompletely understood, it is likely that n-3 PUFA prevents renal disease progression by interfering with a number of effector pathways triggered by mesangial immune-complex deposition. In addition, potential targets of n-3 PUFA relevant to renal disease progression could be similar to those involved in preventing the development and progression of cardiovascular disease by lowering blood pressure, reducing serum lipid levels, decreasing vascular resistance, or preventing thrombosis. In IgA nephropathy, efficacy of n-3 PUFA contained in fish oil supplements has been tested with varying results. The largest randomized clinical trial performed by our collaborative group provided strong evidence that treatment for 2 years with a daily dose of 1.8 g of EPA and 1.2 g of DHA slowed the progression of renal disease in high-risk patients. These benefits persisted after 6.4 years of follow up. With safety, composition, and dosing convenience in mind, we can recommend two products that are available as pharmaceutical-grade fish-oil concentrates, Omacor (Pronova Biocare, Oslo, Norway) and Coromega (European Reference Botanical Laboratories, Carlsbad, CA).

Inhibition of LPS- and CpG DNA-induced TNF-alpha response by oxidized phospholipids

Lipid oxidation is commonly seen in the innate immune response, in which reactive oxygen intermediates are generated to kill pathogenic microorganisms. Although oxidation products of phospholipids have generally been regarded to play a role in a number of chronic inflammatory processes, several studies have shown that oxidized phospholipids inhibit the LPS-induced acute proinflammatory response in cultured macrophages and endothelial cells. We report in this study that oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (PAPC), but not nonoxidized PAPC, significantly inhibits the LPS-induced TNF-alpha response in intact mice. Oxidized PAPC also inhibits the 2'-deoxyribo(cytidine-phosphate-guanosine) (CpG) DNA-induced TNF-alpha response in cultured macrophages and intact mice. To elucidate the mechanisms of action, we show that oxidized PAPC, but not nonoxidized PAPC, inhibits the LPS- and CpG-induced activation of p38 MAPK and the NF-kappaB cascade. These results suggest a role for oxidized lipids as a negative regulator in controlling the magnitude of the innate immune response. Further studies on the mechanisms of action may lead to development of a new type of anti-inflammatory drug for treatment of acute inflammatory diseases such as sepsis.

Habitual dietary intake of n-3 and n-6 fatty acids in relation to inflammatory markers among US men and women

BACKGROUND

Polyunsaturated fatty acid intake favorably affects chronic inflammatory-related diseases such as cardiovascular disease; however, high intake of n-6 fatty acids may attenuate the known beneficial effects of n-3 fatty acids.

METHODS AND RESULTS

We investigated habitual dietary n-3 fatty acid intake and its interaction with n-6 fatty acids in relation to the plasma inflammatory markers C-reactive protein, interleukin 6, and soluble tumor necrosis factor receptors 1 and 2 (sTNF-R1 and R2) among 405 healthy men and 454 healthy women. After adjustment for other predictors of inflammation, intake of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was inversely associated with plasma levels of sTNF-R1 and sTNF-R2 (P=0.03 and P<0.001, respectively) and somewhat less so for C-reactive protein (P=0.08). n-3 alpha-linolenic acid and n-6 cis-linoleic acid were not significantly related to the inflammatory markers. We found little if any association between n-3 fatty acid (EPA+DHA) intake and tumor necrosis factor receptors among participants with low intake of n-6 but a strong inverse association among those with high n-6 intake (P=0.04 and 0.002 for interaction of n-3 with n-6 on sTNF-R1 and sTNF-R2, respectively).

CONCLUSIONS

These results suggest that n-6 fatty acids do not inhibit the antiinflammatory effects of n-3 fatty acids and that the combination of both types of fatty acids is associated with the lowest levels of inflammation. The inhibition of inflammatory cytokines may be one possible mechanism for the observed beneficial effects of these fatty acids on chronic inflammatory-related diseases.