Differential effects of low-dose docosahexaenoic acid and eicosapentaenoic acid on the regulation of mitogenic signaling pathways in mesangial cells

The Renoprotective Effects of Docosahexaenoic Acid as an Add-on Therapy in Patients Receiving Eicosapentaenoic Acid as Treatment for IgA Nephropathy: A Pilot Uncontrolled Trial

Objective Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have been reported to have beneficial effects in patients with IgA nephropathy (IgAN). Although DHA and EPA have different mechanisms of action, no study to date has assessed their individual actions in patients with IgAN. This study therefore analyzed the effects administering DHA in addition to EPA for the treatment of IgAN. Methods Twenty-one IgAN patients who were being treated with EPA (1,800 mg/day) were switched to EPA (1,860 mg/day) and DHA (1,500 mg/day). The changes in their clinical parameters from 6 months before to 6 months after switching treatment were analyzed. Results The triglyceride levels did not change during treatment with EPA alone, but tended to decrease-although not to a statistically significant extent-after the switch. The patients' low-density-lipoprotein cholesterol, blood pressure, proteinuria, and hematuria levels were similar before and after switching. The estimated glomerular filtration rate (eGFR) tended to decrease during EPA therapy, but became stable after switching and the median %⊿eGFR changed from -7.354% during EPA therapy to +1.26% during the 6 months after switching to EPA and DHA therapy (p=0.00132), and renal the function remained stable for another 6 months. Moreover, the median %⊿eGFR during the 6 months after switching was significantly higher in comparison to IgAN patients who were treated with EPA alone as a control (-3.26%, p=0.0361). No clinical parameters were independently associated with a stable renal function without switching to DHA/EPA. Conclusion The addition of DHA to EPA stabilized the renal function of IgAN patients, and it seemed that there were pleiotropic effects beyond the improvement of the clinical parameters.

Effects of polyphenols and lipids from Pennisetum glaucum grains on T-cell activation: modulation of Ca(2+) and ERK1/ERK2 signaling

BACKGROUND

Pearl millet (PM), i.e., Pennisetum glaucum, is widely grown in Africa and known for its anti-oxidant and anti-hyperlipidemic properties.

METHODS

The P. glaucum grains were obtained from the region of Ouled Aïssa (South of Algeria). We assessed the effects of phenolic compounds and lipids, extracted from seeds of P. glaucum, on rat lymphocyte proliferation, activated by phorbol 12-myristate 13-acetate and ionomycin. In order to explore signaling pathway, triggered by these compounds, we assessed interleukin-2 (IL-2) mRNA expression and extracellular signal-regulated kinase-1/2 (ERK1/ERK2) phosphorylation. Finally, we determined increases in free intracellular Ca(2+) concentrations, [Ca(2+)]i, by employing Fura-2/AM in rat lymphocytes.

RESULTS

The composition of P. glaucum grains in polyphenols was estimated to be 1660 µg gallic acid equivalents (GAE)/g. Lipids represented 4.5 %, and more than 72% of the fatty acids belonged to unsaturated family. Our investigation showed that both lipid and phenolic compounds inhibited mitogen-induced T-cell proliferation. Compared with phenolic compounds, lipids exerted weaker effects on ERK-1/ERK2 phosphorylation and Ca(2+) signaling in mitogen-activated T-cells.

CONCLUSION

We conclude that the immunomodulatory effects of P. glaucum could be contributed by its phenolic and lipid contents.

Omega-3 polyunsaturated fatty acids selectively inhibit growth in neoplastic oral keratinocytes by differentially activating ERK1/2

The long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs)—eicosapentaenoic acid (EPA) and its metabolite docosahexaenoic acid (DHA)—inhibit cancer formation in vivo, but their mechanism of action is unclear. Extracellular signal-regulated kinase 1/2 (ERK1/2) activation and inhibition have both been associated with the induction of tumour cell apoptosis by n-3 PUFAs. We show here that low doses of EPA, in particular, inhibited the growth of premalignant and malignant keratinocytes more than the growth of normal counterparts by a combination of cell cycle arrest and apoptosis. The growth inhibition of the oral squamous cell carcinoma (SCC) lines, but not normal keratinocytes, by both n-3 PUFAs was associated with epidermal growth factor receptor (EGFR) autophosphorylation, a sustained phosphorylation of ERK1/2 and its downstream target p90RSK but not with phosphorylation of the PI3 kinase target Akt. Inhibition of EGFR with either the EGFR kinase inhibitor AG1478 or an EGFR-blocking antibody inhibited ERK1/2 phosphorylation, and the blocking antibody partially antagonized growth inhibition by EPA but not by DHA. DHA generated more reactive oxygen species and activated more c-jun N-terminal kinase than EPA, potentially explaining its increased toxicity to normal keratinocytes. Our results show that, in part, EPA specifically inhibits SCC growth and development by creating a sustained signalling imbalance to amplify the EGFR/ERK/p90RSK pathway in neoplastic keratinocytes to a supraoptimal level, supporting the chemopreventive potential of EPA, whose toxicity to normal cells might be reduced further by blocking its metabolism to DHA. Furthermore, ERK1/2 phosphorylation may have potential as a biomarker of n-3 PUFA function in vivo.

Distinguishing health benefits of eicosapentaenoic and docosahexaenoic acids

Long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs) are recommended for management of patients with wide-ranging chronic diseases, including coronary heart disease, rheumatoid arthritis, dementia, and depression. Increased consumption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is recommended by many health authorities to prevent (up to 0.5 g/day) or treat chronic disease (1.0 g/day for coronary heart disease; 1.2–4 g/day for elevated triglyceride levels). Recommendations for dietary intake of LC n-3 PUFAs are often provided for α-linolenic acid, and for the combination of EPA and DHA. However, many studies have also reported differential effects of EPA, DHA and their metabolites in the clinic and at the laboratory bench. The aim of this article is to review studies that have identified divergent responses to EPA and DHA, and to explore reasons for these differences. In particular, we review potential contributing factors such as differential membrane incorporation, modulation of gene expression, activation of signaling pathways and metabolite formation. We suggest that there may be future opportunity to refine recommendations for intake of individual LC n-3 PUFAs.

Decoy receptor 3 inhibits renal mononuclear leukocyte infiltration and apoptosis and prevents progression of IgA nephropathy in mice

The progression of IgA nephropathy (IgAN), the most frequent type of primary glomerulonephritis, is associated with high levels of mononuclear leukocyte infiltration into the kidney. These cells consist mainly of T cells and macrophages. Our previous study showed that a decoy receptor 3 (DCR3) gene therapy can prevent the development of a mouse autoimmune glomerulonephritis model by its potent immune modulating effects (Ka SM, Sytwu HK, Chang DM, Hsieh SL, Tsai PY, Chen A. J Am Soc Nephrol 18: 2473-2485, 2007). Here, we tested the hypothesis that DCR3 might prevent the progression of IgAN, an immune complex-mediated primary glomerulonephritis, by inhibiting T cell activation, renal T cell/macrophage infiltration, and protecting the kidney from apoptosis. We used a progressive IgAN (Prg-IgAN) model in B cell-deficient mice, because the mice are characterized by a dramatic proliferation of activated T cells systemically and progressive NF-κB activation in the kidney. We treated the animals with short-term gene therapy with DCR3 plasmids by hydrodynamics-based gene delivery. When the mice were euthanized on day 21, we found that, compared with empty vector-treated (disease control) Prg-IgAN mice, DCR3 gene therapy resulted in 1) systemic inhibition of T cell activation and proliferation; 2) lower serum levels of proinflammatory cytokines; 3) improved proteinuria, renal function, and renal pathology (inhibiting the development of marked glomerular proliferation, crescent formation, glomerulosclerosis, and interstitial inflammation); 5) suppression of T cell and macrophage infiltration into the periglomerular interstitium of the kidney; and 5) a reduction in apoptotic figures in the kidney. On the basis of these findings, DCR3 might be useful therapeutically in preventing the progression of IgAN.

Omega-3 fatty acids induce apoptosis in human breast cancer cells and mouse mammary tissue through syndecan-1 inhibition of the MEK-Erk pathway

Human epidemiological studies have shown that diets enriched in n-3 polyunsaturated fatty acids (n-3 PUFA) are associated with a lower incidence of cancers including breast cancer. Our previous studies showed that the n-3 PUFA, docosahexaenoic acid (DHA), upregulated syndecan-1 (SDC-1) expression to induce apoptosis in the human breast cancer cell line MCF-7. We now present evidence of a signaling pathway that is impacted by SDC-1 in these cells and in mouse mammary tissues to result in apoptosis. In MCF-7 cells and SK-BR-3 cells, DHA and a SDC-1 ectodomain impaired signaling of the p44/42 mitogen-activated protein kinase (MAPK) pathway by inhibiting the phosphorylation of MAPK/Erk (MEK)/extracellular signal-regulated kinase (Erk) and Bad to induce apoptosis. SDC-1 siRNA significantly enhanced phosphorylation of these signal molecules and blocked the inhibitory effects of DHA on their phosphorylation. SDC-1 siRNA diminished apoptosis of MCF-7 cells, an effect that was markedly blocked by MEK inhibitor, PD98059. In vivo studies used (i) Fat-1 mice, a genetic model able to convert n-6 to n-3 PUFA to result in higher SDC-1 levels in Fat-1 mammary tissue compared with that of wild-type (wt) mice. Phosphorylation of MEK, Erk and Bad was lower in the Fat-1 versus wt tissue and (ii) SDC-1(-/-) mice that demonstrated markedly higher levels of phosphorylated MEK, Erk and Bad in mammary gland tissue compared with those of SDC(+/+) mice. These data elucidate a pathway whereby SDC-1, upregulated by DHA, induces apoptosis in breast cancer cells through inhibition of MEK/Erk/Bad signaling.

Novel Anticancer Platinum(IV) Complexes with Adamantylamine: Their Efficiency and Innovative Chemotherapy Strategies Modifying Lipid Metabolism

The impressive impact of cisplatin on cancer on one side and severe side effects, as well as the development of drug resistance during treatment on the other side, were the factors motivating scientists to design and synthesize new more potent analogues lacking disadvantages of cisplatin. Platinum(IV) complexes represent one of the perspective groups of platinum-based drugs. In this review, we summarize recent findings on both in vitro and in vivo effects of platinum(IV) complexes with adamantylamine. Based on a literary overview of the mechanisms of activity of platinum-based cytostatics, we discuss opportunities for modulating the effects of novel platinum complexes through interactions with apoptotic signaling pathways and with cellular lipids, including modulations of the mitochondrial cell death pathway, oxidative stress, signaling of death ligands, lipid metabolism/signaling, or intercellular communication. These approaches might significantly enhance the efficacy of both novel and established platinum-based cytostatics.

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.

Eicosapentaenoic acid inhibits endothelial cell migration in vitro

BACKGROUND

As n-3 Polyunsaturated Fatty Acids exert a beneficial action on the cardiovascular system, it is important to investigate their effects on endothelial cell responses that (like migration) contribute to repairing vascular lesions.

METHODS

To this purpose, using functional and morphological in vitro assays, we have examined the effect of n-3 Polyunsaturated Fatty Acids on the migration of endothelial cells.

RESULTS

We report here that incubation of endothelial cells with n-3 Polyunsaturated Fatty Acids impaired cell migration into a wound, triggered peripheral distribution of focal adhesions and caused partial disassembly of actin filaments. We also found that eicosapentaenoic acid and docosahexaenoic acid exerted similar effects on the focal adhesions, but that eicosapentaenoic acid was sufficient for inhibiting cell migration.

CONCLUSIONS

Given the importance of endothelial cell migration in the repair of vascular injuries, these in vitro findings call for in vivo evaluation of vascular repair in response to different dietary ratios of eicosapentaenoic to docosahexaenoic acid.

Omega-3 polyunsaturated fatty acids in the treatment of kidney disease

After more than 25 years of published investigation, including randomized controlled trials, the role of omega-3 polyunsaturated fatty acids in the treatment of kidney disease remains unclear. In vitro and in vivo experimental studies support the efficacy of omega-3 polyunsaturated fatty acids on inflammatory pathways involved with the progression of kidney disease. Clinical investigations have focused predominantly on immunoglobulin A (IgA) nephropathy. More recently, lupus nephritis, polycystic kidney disease, and other glomerular diseases have been investigated. Clinical trials have shown conflicting results for the efficacy of omega-3 polyunsaturated fatty acids in IgA nephropathy, which may relate to varying doses, proportions of eicosapentaenoic acid and docosahexaenoic acid, duration of therapy, and sample size of the study populations. Meta-analyses of clinical trials using omega-3 polyunsaturated fatty acids in IgA nephropathy have been limited by the quality of available studies. However, guidelines suggest that omega-3 polyunsaturated fatty acids should be considered in progressive IgA nephropathy. Omega-3 polyunsaturated fatty acids decrease blood pressure, a known accelerant of kidney disease progression. Well-designed, adequately powered, randomized, controlled clinical trials are required to further investigate the potential benefits of omega-3 polyunsaturated fatty acids on the progression of kidney disease and patient survival.

Studies on the protective effect of dietary fish oil on uranyl-nitrate-induced nephrotoxicity and oxidative damage in rat kidney

Human and animal exposure demonstrates that uranium is nephrotoxic. However, attempts to reduce it were not found suitable for clinical use. Dietary fish oil (FO) enriched in omega-3 fatty acids reduces the severity of cardiovascular and renal diseases. Present study investigates the protective effect of FO on uranyl nitrate (UN)-induced renal damage. Rats prefed with experimental diets for 15 days, given single nephrotoxic dose of UN (0.5mg/kg body weight) intraperitoneally. After 5d of UN treatment, serum/urine parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM), oxidative stress and phosphate transport were analyzed in rat kidney. UN nephrotoxicity was characterized by increased serum creatinine and blood urea nitrogen. UN increased the activity of lactate dehydrogenase and NADP-malic enzyme whereas decreased malate, isocitrate and glucose-6-phophate dehydrogenases; glucose-6-phophatase, fructose-1, 6-bisphosphatase and BBM enzyme activities. UN caused oxidant/antioxidant imbalances as reflected by increased lipid peroxidation, activities of superoxide dismutase, glutathione peroxidase and decreased catalase activity. Feeding FO alone increased activities of enzymes of glucose metabolism, BBM, oxidative stress and Pi transport. UN-elicited alterations were prevented by FO feeding. However, corn oil had no such effects and was not similarly effective. In conclusion, FO appears to protect against UN-induced nephrotoxicity by improving energy metabolism and antioxidant defense mechanism.

Antineoplastic effects of n-3 polyunsaturated fatty acids in combination with drugs and radiotherapy: preventive and therapeutic strategies

Many data support the beneficial effect of n-3 polyunsaturated fatty acids (PUFAs) as chemopreventive and chemotherapeutic agents in the treatment of several chronic pathologies including cancer. Different molecular mechanisms have been proposed to explain their effects, including alterations in arachidonic acid oxidative metabolism and metabolic conversion of n-3 PUFAs to novel discovered bioactive derivatives; modification of oxidative stress; changes in cell membrane fluidity and structure and altered metabolism and function of membrane proteins. Considerable knowledge has been recently gathered on the possible beneficial effects of n-3 PUFAs administered in combination with different antineoplastic drugs and radiotherapy against melanoma, leukemia, neuroblastoma, and colon, breast, prostate, and lung cancer. The efficacy of these combinations has been demonstrated both in vivo and in vitro, and clinical trials have also been conducted. The aim of this review is to analyze all the n-3 PUFA combinations investigated so far, their efficacy, and the possible molecular mechanisms involved. It would be highly auspicable that the detailed analysis of the literature in this field could further support the common use of n-3 PUFAs in combination with other chemopreventive agents and warrant more clinical investigations designed to test the effectiveness of n-3 PUFA treatments coupled with conventional antineoplastic therapies.

AMPA receptor-mediated cell death is reduced by docosahexaenoic acid but not by eicosapentaenoic acid in area CA1 of hippocampal slice cultures

Over the last decade, several studies have shown that high levels of polyunsaturated fatty acids (PUFAs) in the brain might limit neuronal damage in various pathological conditions. For example, in animal models of Alzheimer's disease, omega-3 type PUFAs such as docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids have been proposed to decrease both the cognitive and the cellular manifestations of premature ageing. The mechanisms by which they promote brain integrity remain to be established, and the experiments on cultured hippocampal slices described here examine the possibility that omega-3 fatty acids can modulate brain cell viability by interacting with glutamate receptors. We observed, by lactate dehydrogenase release and propidium iodide (PI) uptake, that excitotoxicity triggered by an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor agonist was markedly reduced in hippocampal slices treated with DHA. PI uptake experiments also revealed that neuroprotection by DHA was restricted to the hippocampal CA1 region and could not be reproduced by EPA or arachidonic acid, an omega-6 PUFA. Moreover, the beneficial effect of DHA was specific to AMPA receptor stimulation, insofar as the toxicity induced by N-methyl-D-aspartate or kainate receptor agonists was not diminished by DHA preincubation. Biotinylation experiments finally indicated that the neuroprotective actions of DHA could result from down-regulation of AMPA receptors in hippocampal membranes. This investigation thus provides the first indication that a beneficial outcome of DHA on the brain could derive from specific modulation of AMPA-mediated toxicity, reinforcing the notion that dietary DHA uptake might be useful in preventing neurodegenerative diseases.

Chemopreventive and renal protective effects for docosahexaenoic acid (DHA): implications of CRP and lipid peroxides

Background

The fish oil-derived ω-3 fatty acids, like docosahexanoic (DHA), claim a plethora of health benefits. We currently evaluated the antitumor effects of DHA, alone or in combination with cisplatin (CP) in the EAC solid tumor mice model, and monitored concomitant changes in serum levels of C-reactive protein (CRP), lipid peroxidation (measured as malondialdehyde; MDA) and leukocytic count (LC). Further, we verified the capacity of DHA to ameliorate the lethal, CP-induced nephrotoxicity in rats and the molecular mechanisms involved therein.

Results

EAC-bearing mice exhibited markedly elevated LC (2-fold), CRP (11-fold) and MDA levels (2.7-fold). DHA (125, 250 mg/kg) elicited significant, dose-dependent reductions in tumor size (38%, 79%; respectively), as well as in LC, CRP and MDA levels. These effects for CP were appreciably lower than those of DHA (250 mg/kg). Interestingly, DHA (125 mg/kg) markedly enhanced the chemopreventive effects of CP and boosted its ability to reduce serum CRP and MDA levels. Correlation studies revealed a high degree of positive association between tumor growth and each of CRP (r = 0.85) and leukocytosis (r = 0.89), thus attesting to a diagnostic/prognostic role for CRP.

On the other hand, a single CP dose (10 mg/kg) induced nephrotoxicity in rats that was evidenced by proteinuria, deterioration of glomerular filtration rate (GFR, -4-fold), a rise in serum creatinine/urea levels (2–5-fold) after 4 days, and globally-induced animal fatalities after 7 days. Kidney-homogenates from CP-treated rats displayed significantly elevated MDA- and TNF-α-, but reduced GSH-, levels. Rats treated with DHA (250 mg/kg, but not 125 mg/kg) survived the lethal effects of CP, and showed a significant recovery of GFR; while their homogenates had markedly-reduced MDA- and TNF-α-, but -increased GSH-levels. Significant association was detected between creatinine level and those of MDA (r = 0.81), TNF-α ) r = 0.92) and GSH (r = -0.82); implying causal relationships.

Conclusion

DHA elicited prominent chemopreventive effects on its own, and appreciably augmented those of CP as well. The extent of tumor progression in various mouse groups was highly reflected by CRP levels (thus implying a diagnostic/prognostic role for CRP). Further, this study is the first to reveal that DHA can obliterate the lethal CP-induced nephrotoxicity and renal tissue injury. At the molecular level, DHA appears to act by reducing leukocytosis, systemic inflammation, and oxidative stress.

Docosahexaenoic acid induces apoptosis in lung cancer cells by increasing MKP-1 and down-regulating p-ERK1/2 and p-p38 expression

Different agents able to modulate apoptosis have been shown to modify the expression of the MAP-kinase-phosphatase-1 (MKP-1). The expression of this phosphatase has been considered a potential positive prognostic factor in lung cancer, and smoke was shown to reduce the levels of MKP-1 in ferret lung. Our aim was to assess whether the n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA), known to inhibit the growth of several cancer cells mainly inducing apoptosis, may exert pro-apoptotic effect in lung cancer cells by modifying MKP-1 expression. We observed that DHA increased MKP-1 protein and mRNA expression and induced apoptosis in different lung cancer cell lines (mink Mv1Lu adenocarcinoma cells, human A549 adenocarcinoma and human BEN squamous carcinoma cells). We inhibited the pro-apoptotic effect of DHA by treating the cells with the phosphatase inhibitor Na(3)VO(4) or by silencing the MKP-1 gene with the specific siRNA. This finding demonstrated that the induction of apoptosis by DHA involved a phosphatase activity, specifically that of MKP-1. DHA reduced also the levels of the phosphorylated MAP-kinases, especially ERK1/2 and p38. Such an effect was not observed when the MKP-1 gene was silenced. Altogether, the data provide evidence that the DHA-induced overexpression of MKP-1 and the resulting decrease of MAP-kinase phosphorylation by DHA may underlie the pro-apoptotic effect of this fatty acid in lung cancer cells. Moreover, they support the hypothesis that DHA may exert chemopreventive action in lung cancer.

Anti-obesity effects of conjugated linoleic acid, docosahexaenoic acid, and eicosapentaenoic acid

Obesity has become a prevailing epidemic throughout the globe. Effective therapies for obesity become attracting. Food components with beneficial effects on "weight loss" have caught increasing attentions. Conjugated linoleic acid (CLA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) belong to different families of polyunsaturated fatty acids (PUFA). However, they have similar effects on alleviating obesity and/or preventing from obesity. They influence the balance between energy intake and expenditure; and reduce body weight and/or fat deposition in animal models, but show little effect in healthy human subjects. They inhibit key enzymes responsible for lipid synthesis, such as fatty acid synthase and stearoyl-CoA desaturase-1, enhance lipid oxidation and thermogenesis, and prevent free fatty acids from entering adipocytes for lipogenesis. PUFA also exert suppressive effects on several key factors involved in adipocyte differentiation and fat storage. Despite their similar effects and shared mechanisms, they display differences in the regulation of lipid metabolism. Moreover, DHA and EPA exhibit "anti-obesity" effect as well as improving insulin sensitivity, while CLA induces insulin resistance and fatty liver in most cases. A deeper and more detailed investigation into the complex network of anti-obesity regulatory pathways by different PUFA will improve our understanding of the mechanisms of body weight control and reduce the prevalence of obesity.

Studies on the protective effect of dietary fish oil on gentamicin-induced nephrotoxicity and oxidative damage in rat kidney

Gentamicin (GM)-induced nephrotoxicity limits its long-term clinical use. Several agents/strategies were attempted to prevent GM nephrotoxicity but were not found suitable for clinical practice. Dietary fish oil (FO) retard the progression of certain types of cancers, cardiovascular and renal disorders. We aimed to evaluate protective effect of FO on GM-induced renal proximal tubular damage. The rats were pre-fed experimental diets for 10 days and then received GM (80 mg/kg body weight/day) treatment for 10 days while still on diet. Serum/urine parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM), oxidative stress and phosphate transport in rat kidney were analyzed. GM nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. GM increased the activities of lactate and glucose-6-phosphate dehydrogenases whereas decreased malate, isocitrate dehydrogenases; glucose-6 and fructose-1,6-bisphosphatases; superoxide dismutase, catalase, glutathione peroxidase and BBM enzymes. In contrast, FO alone increased enzyme activities of carbohydrate metabolism, BBM and oxidative stress. FO feeding to GM treated rats markedly enhanced resistance to GM elicited deleterious effects and prevented GM-induced decrease in 32Pi uptake across BBM. Dietary FO supplementation ameliorated GM-induced specific metabolic alterations and oxidative damage due to its intrinsic biochemical/antioxidant properties.

Signaling pathways modulated by fish oil in salt-sensitive hypertension

Although many studies have indicated that fish oil (FO) improves cardiovascular risk factors and reduces histopathological manifestations of injury in experimental renal injury models, potential mechanisms underlying this protective effect have not been adequately defined. The objective of this study was to identify potential signaling pathways that confer protection in the Dahl rat model of salt-sensitive hypertension. Male Dahl salt-sensitive rats (n = 10/group) were provided with formulated diets containing 8% NaCl, 20% protein, and 25% FO or 25% corn oil (CO) for 28 days. FO reduced blood pressure (-11% at 4 wk; P < 0.05), urine protein excretion (-45% at 4 wk; P < 0.05), plasma cholesterol and triglyceride levels (-54%, P < 0.001; and -58%, P < 0.05), and histopathological manifestations of renal injury, including vascular hypertrophy, segmental and global glomerular sclerosis, interstitial fibrosis, and tubular atrophy. Interstitial inflammation was significantly reduced by FO (-32%; P < 0.001), as assessed by quantitative analysis of ED1-positive cells in sections of the renal cortex. FO reduced tubulointerstitial proliferative activity, as assessed by Western blot analysis of cortical homogenates for PCNA (-51%; P < 0.01) and quantitative analysis of Mib-1-stained sections of the renal cortex (-42%; P < 0.001). Decreased proliferative activity was associated with reduced phospho-ERK expression (-37%; P < 0.005) and NF-kappaB activation (-42%; P < 0.05). FO reduced cyclooxygenase (COX)-2 expression (-63%; P < 0.01) and membrane translocation of the NADPH oxidase subunits p47(phox) and p67(phox) (-26 and -34%; P < 0.05). We propose that FO ameliorates renal injury in Dahl salt-sensitive rats through the inhibition of ERK, decreased NF-kappaB activation, inhibition of COX-2 expression, and decreased NADPH oxidase activation.

In utero and postnatal exposure to long chain (n-3) PUFA enhances intestinal glucose absorption and energy stores in weanling pigs

The aim of this research was to determine whether feeding gestating and lactating sows (n-3) PUFA [eicosapentaenoic acid (EPA) and/or docosahexenoic acid (DHA)] or coconut fat (saturated fat) influences ex vivo glucose absorption in the proximal jejunum and glucose and glycogen concentration of liver and muscle of their offspring at weaning. Sows were fed 1 of 4 diets for 150 d, which included the entire gestation and lactation periods. The diets consisted of basal corn/soybean meal (CONT), CONT + protected EPA and DHA-rich fish oil (PFO), CONT + DHA Gold fat (DHAGF), and CONT + coconut fat (COCO). All tissues were collected from piglets (n = 4 per treatment) following a 24-h period of food deprivation, which was initiated at weaning. Proximal jejunum samples were mounted in modified Ussing chambers for transport determinations. Relative to the CONT (7 muA/cm(2)), active glucose transport was greater (P = 0.013) in piglets from sows fed the PFO (30 microA/cm(2)) and DHAGF (40 microA/cm(2)) diets, but not the COCO diet (19 microA/cm(2); pooled SEM = 5). Likewise, jejunum expression of glucose transporter 2 and sodium glucose transporter 1 protein tended (P < 0.10) to be greater in piglets from dams fed the PFO and DHAGF diets, as did AMP-activated protein kinase activity. Piglets' muscle glycogen was greater than in CONT (34 +/- 5.2 mg/g wet tissue) only in piglets from dams fed the DHAGF (46 +/- 5.2 mg/g wet tissue; P < 0.05). These results indicate that (n-3) PUFA, particularly DHA, improves intestinal glucose absorption and muscle glycogen concentrations in newly weaned pigs. These findings may also have important implications for human mothers and infants.

Ethyl-EPA in Huntington disease: potentially relevant mechanism of action

The pathomechanisms involved in the neuronal dysfunction in Huntington disease (HD) are still unresolved and may be heterogeneous. One potential mechanism might be related to the induction of mitochondrial dysfunction in the CNS. This might lead firstly to neuronal dysfunction and finally to the activation of apoptotic pathways. Several compounds, which should alleviate mitochondrial dysfunction, have been tested in preclinical models as well as in clinical trials of different scale. Recently we reported the efficacy of Ethyl-eicosapentaenoic acid (Ethyl-EPA) in patients with HD. Ethyl-EPA is a polyunsaturated fatty acid from the n-3 group, which is in clinical development for HD and melancholic depression. In our trial with Ethyl-EPA in HD responding patients could be characterized by either a lower CAG repeat number or a chorea-predominant clinical expression of the disease. Here we would like to describe some evidence on the potential mechanism of action of Ethyl-EPA in HD. We specifically focus on pathways, which are known to be influenced in HD and are modified by Ethyl-EPA and which points to an involvement of mitochondrial function as a common target. Some attention is given to the NF-kappa B pathway and the c-Jun amino-terminal kinases (JNK) pathway, which both may lead to an activation of the antiproliferative factor p53 and consequently mitochondrial dysfunction. Further the effects of EPA or Ethyl-EPA in preclinical models of HD are described. The evidence from these studies led to the design of phase III clinical trials, which are ongoing.

Neuroblastoma cell death in response to docosahexaenoic acid: Sensitization to chemotherapy and arsenic-induced oxidative stress

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid vital for the developing nervous system and significantly decreased in neuroblastoma cells compared to nontransformed nervous tissue. We investigated whether supplementation of DHA affects the susceptibility of neuroblastoma cells to oxidative stress generated endogenously and in response to cytotoxic therapy. DHA, but not the monounsaturated oleic acid (OA), induced dose- and time-dependent neuroblastoma cell death. DHA supplementation was associated with depolarization of the mitochondrial membrane potential, production of reactive oxygen species (ROS) and accumulation of DNA in sub-G1 phase of the cell cycle. The antioxidant, vitamin E, inhibited mitochondrial depolarization and subsequent cell death induced by DHA, whereas, the mitochondrial pore inhibitor, cyclosporin A, partly inhibited DHA-induced neuroblastoma cell death. Depletion of glutathione by L-buthionine-sulfoximine significantly enhanced the cytotoxic effects of DHA. Nontransformed fibroblasts were not substantially affected by DHA. DHA, but not OA, significantly enhanced the cytotoxicity of cisplatin, doxorubicin and irinotecan both in chemosensitive and in multidrug-resistant neuroblastoma cells. DHA potently sensitized neuroblastoma cells to a clinically relevant concentration (1 microM) of arsenic trioxide (As2O3) and enhanced the effect of the nonsteroidal antiinflammatory drug (NSAID), diclofenac. These findings provide experimental evidence that the omega-3 fatty acid, DHA, is cytotoxic to drug-resistant neuroblastoma. The potent action of DHA with arsenic trioxide, NSAID and chemotherapeutic agents suggests clinical testing of this therapeutic concept in children with neuroblastoma.

Comparative toxicity of oleic and linoleic acid on human lymphocytes

Commercially available lipid emulsions for parenteral nutrition are mainly composed by long chain triacylglycerol containing a high proportion of linoleic acid (LA) or oleic acid (OA). The immunological impact of such therapy is particularly important because parenteral diets are often administered to critically ill patients as a mechanism to supply adequate nutrition during catabolic stress conditions. The comparative toxicity of OA and LA on human lymphocytes and the type of cell death induced by these fatty acids were determined in vitro. Parameters of cell death were investigated by flow cytometry-cell viability, DNA fragmentation, phosphatidylserine externalization, mitochondrial depolarization, neutral lipid accumulation and production of reactive oxygen species-and by fluorescence microscopy-chromatin condensation. Additionally a spectrofluorometric assay was employed to determine the activities of caspase--3, 6 and 8. Evidence is presented herein that OA is less toxic to human lymphocytes than LA. However, both fatty acids promoted apoptosis and necrosis of these cells. The mechanism of cell death induced by OA involved activation of caspase 3 while the mechanism of death induced by LA involved mitochondrial depolarization and ROS production. Importantly, neutral lipid accumulation may be a mechanism to protect lymphocytes against the toxicity induced by OA. OA may offer an immunological less problematic alternative to LA with respect to fatty acid composition of parenteral nutritional emulsions.

Bile acids induce hepatic stellate cell proliferation via activation of the epidermal growth factor receptor

BACKGROUND & AIMS

Hepatic stellate cell (HSC) proliferation is a key event in the development of liver fibrosis. In many liver diseases, HSCs are exposed to inflammatory cytokines, reactive oxygen species, and bile acids. Although inflammatory cytokines and reactive oxygen species are known to promote proliferation of HSCs, nothing is known about the effects of bile acids on HSC proliferation or apoptosis. The aim of this study was to investigate the effects of bile acids on HSC proliferation.

METHODS

HSCs were exposed to bile acids with different hydrophobicity (5-200 micromol/L). HSC proliferation and cell cycle-related events were assessed by bromodeoxyuridine incorporation, cell counting and proliferating cell nuclear antigen and cyclin E expression, apoptosis by caspase-3 activity assay, immunocytochemistry for active caspase-3 and acridine orange staining, and activation of signal transduction pathways by Western blot using phospho-specific antibodies. Uptake of bile acids was investigated using fluorescent bile acids.

RESULTS

All bile acids, at concentrations >25 micromol/L, induce a 2.5- to 3-fold increase in HSC proliferation via activation of the epidermal growth factor receptor. Bile acid-induced proliferation is mediated by activation of a protein kinase C/extracellular signal-regulated kinase/p70S6K-dependent pathway. Bile acids did not induce apoptosis in HSCs. HSCs do not take up fluorescent bile acids and do not express the bile acid importer ntcp.

CONCLUSIONS

Bile acids at levels reached in cholestatic conditions are an independent profibrogenic factor. Bile acids induce HSC proliferation via the activation of the epidermal growth factor receptor, whereas HSCs are protected against bile acid-induced apoptosis by excluding bile acids.

The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina

In this work we advance the hypothesis that omega-3 (omega-3) long-chain polyunsaturated fatty acids (LCPUFAs) exhibit cytoprotective and cytotherapeutic actions contributing to a number of anti-angiogenic and neuroprotective mechanisms within the retina. omega-3 LCPUFAs may modulate metabolic processes and attenuate effects of environmental exposures that activate molecules implicated in pathogenesis of vasoproliferative and neurodegenerative retinal diseases. These processes and exposures include ischemia, chronic light exposure, oxidative stress, inflammation, cellular signaling mechanisms, and aging. A number of bioactive molecules within the retina affect, and are effected by such conditions. These molecules operate within complex systems and include compounds classified as eicosanoids, angiogenic factors, matrix metalloproteinases, reactive oxygen species, cyclic nucleotides, neurotransmitters and neuromodulators, pro-inflammatory and immunoregulatory cytokines, and inflammatory phospholipids. We discuss the relationship of LCPUFAs with these bioactivators and bioactive compounds in the context of three blinding retinal diseases of public health significance that exhibit both vascular and neural pathology. How is omega-3 LCPUFA status related to retinal structure and function? Docosahexaenoic acid (DHA), a major dietary omega-3 LCPUFA, is also a major structural lipid of retinal photoreceptor outer segment membranes. Biophysical and biochemical properties of DHA may affect photoreceptor membrane function by altering permeability, fluidity, thickness, and lipid phase properties. Tissue DHA status affects retinal cell signaling mechanisms involved in phototransduction. DHA may operate in signaling cascades to enhance activation of membrane-bound retinal proteins and may also be involved in rhodopsin regeneration. Tissue DHA insufficiency is associated with alterations in retinal function. Visual processing deficits have been ameliorated with DHA supplementation in some cases. What evidence exists to suggest that LCPUFAs modulate factors and processes implicated in diseases of the vascular and neural retina? Tissue status of LCPUFAs is modifiable by and dependent upon dietary intake. Certain LCPUFAs are selectively accreted and efficiently conserved within the neural retina. On the most basic level, omega-3 LCPUFAs influence retinal cell gene expression, cellular differentiation, and cellular survival. DHA activates a number of nuclear hormone receptors that operate as transcription factors for molecules that modulate reduction-oxidation-sensitive and proinflammatory genes; these include the peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and the retinoid X receptor. In the case of PPAR-alpha, this action is thought to prevent endothelial cell dysfunction and vascular remodeling through inhibition of: vascular smooth muscle cell proliferation, inducible nitric oxide synthase production, interleukin-1 induced cyclooxygenase (COX)-2 production, and thrombin-induced endothelin 1 production. Research on model systems demonstrates that omega-3 LCPUFAs also have the capacity to affect production and activation of angiogenic growth factors, arachidonic acid (AA)-based vasoregulatory eicosanoids, and MMPs. Eicosapentaenoic acid (EPA), a substrate for DHA, is the parent fatty acid for a family of eicosanoids that have the potential to affect AA-derived eicosanoids implicated in abnormal retinal neovascularization, vascular permeability, and inflammation. EPA depresses vascular endothelial growth factor (VEGF)-specific tyrosine kinase receptor activation and expression. VEGF plays an essential role in induction of: endothelial cell migration and proliferation, microvascular permeability, endothelial cell release of metalloproteinases and interstitial collagenases, and endothelial cell tube formation. The mechanism of VEGF receptor down-regulation is believed to occur at the tyrosine kinase nuclear factor-kappa B (NFkappaB). NFkappaB is a nuclear transcription factor that up-regulates COX-2 expression, intracellular adhesion molecule, thrombin, and nitric oxide synthase. All four factors are associated with vascular instability. COX-2 drives conversion of AA to a number angiogenic and proinflammatory eicosanoids. Our general conclusion is that there is consistent evidence to suggest that omega-3 LCPUFAs may act in a protective role against ischemia-, light-, oxygen-, inflammatory-, and age-associated pathology of the vascular and neural retina.

Inducible NOS inhibition, eicosapentaenoic acid supplementation, and angiotensin II–induced renal damage

BACKGROUND

Cytochrome P450(CYP)-dependent hydroxylation and epoxygenation metabolites of arachidonic acid (AA) influence renal vascular tone, salt excretion, and inflammation. Transgenic rats over expressing both human renin and angiotensinogen genes (dTGR) feature angiotensin II (Ang II)-induced organ damage, increased expression of inducible nitric oxide synthase (iNOS), decreased AA hydroxylation, and epoxygenation. As nitric oxide production via iNOS can inhibit CYP AA metabolism, we tested the hypothesis that by blocking iNOS or by supplementing eicosapentanoic acid (EPA), which can serve as an alternative CYP substrate, Ang II-induced vasculopathy could be ameliorated.

METHODS

We treated dTGR with the iNOS inhibitor L-N(6)-(1-iminoethyl) lysine (L-NIL), EPA, and the combination of both treatments from week 4 to 7.

RESULTS

Immunohistochemistry showed that L-NIL and EPA reduced glomerular iNOS toward control levels. L-NIL-treated dTGR showed cardiac hypertrophy and albuminuria similar to untreated dTGR. EPA and the combination of EPA + L-NIL, ameliorated organ damage without lowering blood pressure. EPA and EPA + L-NIL reduced cardiac hypertrophy, albuminuria, renal fibronectin expression, and infiltration of monocytes/macrophages, compared to L-NIL and untreated dTGR. Reactive oxygen species were detected in glomeruli of untreated and L-NIL-treated dTGR, but was reduced in the EPA groups. EPA treatment reduced activator protein-1 (AP-1) activation and partially inhibited nuclear factor-kappaB (NF-kappaB) activity in kidneys of dTGR.

CONCLUSION

These results demonstrate that iNOS inhibition does not protect against Ang II-induced end-organ damage, while EPA treatment does. Our electromobility shift assay experiments revealed that EPA protection may involve inhibition of AP-1- and NF-kappaB-dependent pathways.

Docosahexaenoic acid attenuates mycotoxin-induced immunoglobulin a nephropathy, interleukin-6 transcription, and mitogen-activated protein kinase phosphorylation in mice

The purpose of this investigation was to evaluate the dose-dependent effects of docosahexaenoic acid (DHA) on deoxynivalenol (DON)-induced IgA nephropathy in mice and their relation to proinflammatory gene expression and mitogen-activated protein kinase (MAPK) activation. Consumption of a modified AIN-93G diet containing 1, 5, and 30 g/kg DHA resulted in dose-dependent increases of DHA in liver phospholipids with concomitant decreases in arachidonic acid compared with control diets. DHA dose dependently inhibited increases in serum IgA and IgA immune complexes (IC) as well as IgA deposition in the kidney in DON-fed mice; the 30 g/kg DHA diet had the earliest detectable effects and maximal efficacy. Both splenic interleukin-6 (IL-6) mRNA and heterogeneous nuclear RNA (hnRNA), an indicator of IL-6 transcription, were significantly reduced in DON-fed mice that consumed 5 and 30 g/kg DHA; a similar reduction was observed for cyclooxygenase (COX-2) mRNA. In a subsequent study, acute DON exposure (25 mg/kg body weight) induced splenic IL-6 mRNA and hnRNA as well as COX-2 mRNA in mice fed the control diet, whereas induction of both RNA species was significantly inhibited in mice fed 30 g/kg DHA. These latter inhibitory effects corresponded to a reduction in DON-induced phosphorylation of p38, extracellular-signal related kinase 1/2, and c-Jun N-terminal kinase 1/2 MAPKs in the spleen. Taken together, the results indicate that DHA dose-dependently inhibited DON-induced IgA dysregulation and nephropathy, and that impairment of MAPK activation and expression of COX-2 and IL-6 are potential critical upstream mechanisms.

Effects of EPA and DHA on proliferation, cytokine production, and gene expression in Raji cells

The effects of EPA and DHA on the function and gene expression of a B-lymphocyte cell line (Raji) were investigated. Proliferation; production of interleukin-10 (IL-10), tumor necrosis factor (TNF)-alpha, and interferon (INF)-gamma; and expression of pleiotropic genes were evaluated. Cell proliferation was increased in the presence of 12.5 microM EPA (approximately twofold) and 12.5 microM DHA (approximately 1.5-fold). EPA and DHA (25 microM) also decreased production of the key immunoregulatory cytokines IL-10, TNF-alpha, and INF-gamma. EPA and DHA changed the expression of specific genes, but this effect was more marked for EPA (25.9% of genes investigated) compared with DHA (8.4% of genes investigated). EPA and DHA affected the expression of genes clustered as: cytokines, signal transduction, transcription, cell cycle, defense and repair, apoptosis, cell adhesion, cytoskeleton, and hormones. The most remarkable changes were observed in the genes of signal transduction and transcription. These results led us to conclude that the mechanism of DHA and EPA effects on B-lymphocyte functions includes regulation of gene expression. Thus, the ingestion of fish oil, a rich source of EPA and DHA, may have a strong effect on B-lymphocyte function in vivo. However, remarkable differences were observed between DHA and EPA, demonstrating that specific effects of these FA may be responsible for the marked differences in edible oil effects on immune function in vivo reported by others.

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).