Deoxynivalenol-induced mitogen-activated protein kinase phosphorylation and IL-6 expression in mice suppressed by fish oil

N terminus and C terminus of Arabidopsis P4-ATPase AtALA1 facilitate the detoxification of the mycotoxin deoxynivalenol in wheat

Fusarium head blight (FHB) is a devastating disease affecting many important cereal crops. The disease is mainly caused by Fusarium graminearum, which produces mycotoxins, e.g., deoxynivalenol (DON), that contaminate grains, leading to serious issues in food safety worldwide. Here, we demonstrate that expressing the Arabidopsis P4-ATPase flippase gene, AtALA1, significantly increases wheat resistance to FHB, while substantially reducing DON content in grains. However, expressing TaALA1s, the wheat homologs of AtALA1, does not enhance the resistance. We discovered that the N terminus and C terminus of AtALA1 are crucial for its role in DON detoxification. The motif [DE]nX1-2FXX[FL]XXXR, found exclusively in the N terminus of ALA1s in Brassicaceae species, facilitates AtALA1-associated vesicle transport by binding with AP-2. Meanwhile the DON-stimulated phosphorylation at three key sites in the C terminus is responsible for promoting DON trafficking into vacuoles. Our findings suggest a great potential for vesicle-associated detoxification in FHB resistance and food safety.

Deciphering roles of protein post-translational modifications in IgA nephropathy progression and potential therapy

Immunoglobulin A nephropathy (IgAN), one type of glomerulonephritis, displays the accumulation of glycosylated IgA in the mesangium. Studies have demonstrated that both genetics and epigenetics play a pivotal role in the occurrence and progression of IgAN. Post-translational modification (PTM) has been revealed to critically participate in IgAN development and progression because PTM dysregulation results in impaired degradation of proteins that regulate IgAN pathogenesis. A growing number of studies identify that PTMs, including sialylation, o-glycosylation, galactosylation, phosphorylation, ubiquitination and deubiquitination, modulate the initiation and progression of IgAN. Hence, in this review, we discuss the functions and mechanisms of PTMs in regulation of IgAN. Moreover, we outline numerous compounds that govern PTMs and attenuate IgAN progression. Targeting PTMs might be a useful strategy to ameliorate IgAN.

Does chronic dietary exposure to the mycotoxin deoxynivalenol affect the porcine hepatic transcriptome when an acute-phase response is initiated through first or second-pass LPS challenge of the liver?

The sensitivity of pigs to deoxynivalenol (DON) might be increased by systemic inflammation (SI), which also has consequences for hepatic integrity. Liver lesions and a dys-regulated gene network might hamper hepatic handling and elimination of DON whereby the way of initiation of hepatic inflammation might play an additional role. First and second-pass exposure of the liver with LPS for triggering a SI was achieved by LPS infusion via pre- or post-hepatic venous route, respectively. Each infusion group was pre-conditioned either with a control diet (0.12 mg DON/kg diet) or with a DON-contaminated diet (4.59 mg DON/kg diet) for 4 wk. Liver transcriptome was evaluated at 195 min after starting infusions. DON exposure alone failed to modulate the mRNA expression significantly. However, pre- and post-hepatic LPS challenges prompted transcriptional responses in immune and metabolic levels. The mRNAs for B-cell lymphoma 2-like protein 11 as a key factor in apoptosis and IFN-γ released by T cells were clearly up-regulated in DON-fed group infused with LPS post-hepatically. On the other hand, mRNAs for nucleotide binding oligomerization domain containing 2, IFN-α and eukaryotic translation initiation factor 2α kinase 3 as ribosomal stress sensors were exclusively up-regulated in control pigs with pre-hepatic LPS infusion. These diverse effects were traced back to differences in TLR4 signalling.

Anti-inflammatory effects of resolvins in diabetic nephropathy: Mechanistic pathways

The incidence of diabetes mellitus is growing rapidly. The exact pathophysiology of diabetes is unclear, but there is increasing evidence of the role of the inflammatory response in both developing diabetes as well as its complications. Resolvins are naturally occurring polyunsaturated fatty acids that are found in fish oil and sea food that have been shown to possess anti-inflammatory actions in several tissues including the kidneys. The pathways by which resolvins exert this anti-inflammatory effect are unclear. In this review we discuss the evidence showing that resolvins can suppress inflammatory responses via at least five molecular mechanisms through inhibition of the nucleotide-binding oligomerization domain protein 3 inflammasome, inhibition of nuclear factor κB molecular pathways, improvement of oxidative stress, modulation of nitric oxide synthesis/release and prevention of local and systemic leukocytosis. Complete understanding of these molecular pathways is important as this may lead to the development of new effective therapeutic strategies for diabetes and diabetic nephropathy.

Effects of Mycotoxins on Neuropsychiatric Symptoms and Immune Processes

PURPOSE

The effects of air pollutants have been receiving increased attention both clinically and in the media. One such pollutant is mold, fungal growth in the form of multicellular filaments known as hyphae. The growth of molds is omnipresent not only in outdoor settings but also in indoor environments containing excessive amounts of moisture.

METHODS

PubMed was searched for relevant articles using terms such as mold, mycotoxins, fungi, immunity, inflammation, neurodevelopment, cognition, Alzheimer's, and autism.

FINDINGS

Exposure to molds is most commonly associated with allergies and asthma. However, it is now thought to be associated with many complex health problems, since some molds, especially Trichoderma, Fusarium and Stachybotrys spp, produce mycotoxins that are absorbed from the skin, airways, and intestinal lining. People exposed to molds and mycotoxins present with symptoms affecting multiple organs, including the lungs, musculoskeletal system, as well as the central and peripheral nervous systems. Furthermore, evidence has recently implicated exposure to mycotoxins in the pathogenesis of autism spectrum disorder. The effects of mycotoxins can be mediated via different pathways that include the secretion of pro-inflammatory cytokines, especially from mast cells.

IMPLICATIONS

The information reviewed indicates that exposure to mold and mycotoxins can affect the nervous system, directly or through immune cell activation, thus contributing to neurodevelopmental disorders such as autism spectrum disorder.

Eicosapentaenoic and docosahexaenoic acids have different effects on peripheral phospholipase A2 gene expressions in acute depressed patients

INTRODUCTION

Omega-3 polyunsaturated fatty acids (PUFAs) have been proven critical in the development and management of major depressive disorder (MDD) by a number of epidemiological, clinical and preclinical studies, but the molecular mechanisms underlying this therapeutic action are yet to be understood. Although eicosapentaenoic acid (EPA) seems to be the active component of omega-3 PUFAs' antidepressant effects, the biological research about the difference of specific genetic regulations between EPA and docosahexaenoic acid (DHA), the two main components of omega-3 PUFAs, is still lacking in human subjects.

METHODS

We conducted a 12-week randomized-controlled trial comparing the effects of EPA and DHA on gene expressions of phospholipase A2 (cPLA2) and cyclooxygenase-2 (COX2), serotonin transporter (5HTT), and Tryptophan hydroxylase 2 (TPH-2) in 27 MDD patients. In addition, the erythrocyte PUFA compositions and the candidate gene expressions were also compared between these 27 MDD patients and 22 healthy controls.

RESULTS

EPA was associated with a significant decrease in HAM-D scores (CI: -13 to -21, p<0.001) and significant increases in erythrocyte levels of EPA (CI: +1.0% to +2.9%, p=0.001) and DHA (CI: +2.9% to +5.6%, p=0.007). DHA treatment was associated with a significant decrease in HAM-D scores (CI: -6 to -14, p<0.001) and a significant increase in DHA levels (CI: +0.2% to +2.3%, p=0.047), but not of EPA levels. The cPLA2 gene expression levels were significantly increased in patients received EPA (1.9 folds, p=0.038), but not DHA (1.08 folds, p=0.92). There was a tendency for both EPA and DHA groups to decrease COX-2 gene expressions. The gene expressions of COX-2, cPLA2, TPH-2 and 5-HTT did not differ between MDD cases and healthy controls.

CONCLUSIONS

EPA differentiates from DHA in clinical antidepressant efficacy and in upregulating cPLA2 gene regulations, which supports the clinical observation showing the superiority of EPA's antidepressant effects.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02615405.

Primary and Immortalized Human Respiratory Cells Display Different Patterns of Cytotoxicity and Cytokine Release upon Exposure to Deoxynivalenol, Nivalenol and Fusarenon-X

The type B trichothecene mycotoxins deoxynivalenol (DON), nivalenol (NIV) and fusarenon-X (FX) are structurally related secondary metabolites frequently produced by Fusarium on wheat. Consequently, DON, NIV and FX contaminate wheat dusts, exposing grain workers to toxins by inhalation. Those trichothecenes at low, relevant, exposition concentrations have differential effects on intestinal cells, but whether such differences exist with respiratory cells is mostly unknown, while it is required to assess the combined risk of exposure to mycotoxins. The goal of the present study was to compare the effects of DON, NIV and FX alone or in combination on the viability and IL-6 and IL-8-inducing capacity of human epithelial cells representative of the respiratory tract: primary human airway epithelial cells of nasal (hAECN) and bronchial (hAECB) origin, and immortalized human bronchial (16HBE14o-) and alveolar (A549) epithelial cell lines. We report that A549 cells are particularly resistant to the cytotoxic effects of mycotoxins. FX is more toxic than DON and NIV for all epithelial cell types. Nasal and bronchial primary cells are more sensitive than bronchial and alveolar cell lines to combined mycotoxin mixtures at low concentrations, although they are less sensitive to mycotoxins alone. Interactions between mycotoxins at low concentrations are rarely additive and are observed only for DON/NIV and NIV/FX on hAECB cells and DON/NIV/FX on A549 cells. Most interactions at low mycotoxin concentrations are synergistic, antagonistic interactions being observed only for DON/FX on hAECB, DON/NIV on 16HBE14o- and NIV/FX on A549 cells. DON, NIV and FX induce, albeit at different levels, IL-6 and IL-8 release by all cell types. However, NIV and FX at concentrations of low cytotoxicity induce IL-6 release by hAECB and A549 cells, and IL-8 release by hAECN cells. Overall, these data suggest that combined exposure to mycotoxins at low concentrations have a stronger effect on primary nasal epithelial cells than on bronchial epithelial cells and activate different inflammatory pathways. This information is particularly relevant for future studies about the hazard of occupational exposure to mycotoxins by inhalation and its impact on the respiratory tract.

NLRP3 inflammasome as a novel target for docosahexaenoic acid metabolites to abrogate glomerular injury

The nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome has been implicated in podocyte injury and glomerular sclerosis during hyperhomocysteinemia (hHcys). However, it remains unclear whether the NLRP3 inflammasome can be a therapeutic target for treatment of hHcys-induced kidney injury. Given that DHA metabolites-resolvins have potent anti-inflammatory effects, the present study tested whether the prototype, resolvin D1 (RvD1), and 17S-hydroxy DHA (17S-HDHA), an intermediate product, abrogate hHcys-induced podocyte injury by targeting the NLRP3 inflammasome. In vitro, confocal microscopy demonstrated that 17S-HDHA (100 nM) and RvD1 (60 nM) prevented Hcys-induced formation of NLRP3 inflammasomes, as shown by reduced colocalization of NLRP3 with apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) or caspase-1. Both DHA metabolites inhibited Hcys-induced caspase-1 activation and interleukin-1β production. However, DHA had no significant effect on these Hcys-induced changes in podocytes. In vivo, DHA lipoxygenase metabolites substantially inhibited podocyte NLRP3 inflammasome formation and activation and consequent glomerular sclerosis in mice with hHcys. Mechanistically, RvD1 and 17S-HDHA were shown to suppress Hcys-induced formation of lipid raft redox signaling platforms and subsequent O2·- production in podocytes. It is concluded that inhibition of NLRP3 inflammasome activation is one of the important mechanisms mediating the beneficial action of RvD1 and 17S-HDHA on Hcys-induced podocyte injury and glomerular sclerosis.

Eicosapentaenoic acid abolishes inhibition of insulin-induced mTOR phosphorylation by LPS via PTP1B downregulation in skeletal muscle

Dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) increase insulin signaling in skeletal muscle. In the current study, we investigated the effect of eicosapentaenoic acid (EPA) on insulin-induced mammalian target of rapamycin (mTOR) phosphorylation in myotubes. We showed that EPA did not affect basal and insulin-induced mTOR phosphorylation in myotubes. However, EPA abolished lipopolysaccharide (LPS) -induced deficiency in insulin signaling (P < 0.05). Pre-incubation of nuclear factor κB (NF-κΒ) and c-Jun N-terminal kinases (JNK) inhibitors prevented the decreased insulin-induced mTOR phosphorylation elicited by LPS (P < 0.05). In addition, in protein tyrosine phosphatase-1B (PTP1B) knockdown myotubes, LPS failed to decrease insulin-induced mammalian target of rapamycin (mTOR) phosphorylation in myotubes (P > 0.05). In myotubes, LPS stimulated PTP1B expression via NF-κB and activation protein-1 (AP1). Pre-incubation of 50 μM EPA prevented the LPS-induced activation of AP1 and NF-κΒ as well as PTP1B expression (P < 0.05). Interestingly, incubation of peroxisome proliferator-activated receptor γ (PPARγ) antagonist (GW9662) prior to EPA treatment, the effect of EPA on insulin-induced mTOR phosphorylation was blocked. Accordingly, EPA did not inhibit the LPS-induced activation of AP1 or NF-κΒ as well as PTP1B expression when incubation of GW9662 prior to EPA treatment. The in vivo study showed that EPA prevented LPS-induced PTPT1B expression and a decrease in insulin-induced mTOR phosphorylation in muscle of mice. In summary, EPA abolished LPS inhibition of insulin-induced mTOR phosphorylation in myotubes, and one of the key mechanisms was to inhibit AP1 and NF-κB activation and PTP1B transcription.

Enhanced anti-inflammatory effects of DHA and quercetin in lipopolysaccharide-induced RAW264.7 macrophages by inhibiting NF-κB and MAPK activation

The aim of the present study was to investigate the anti-inflammatory effects of docosahexaenoic acid (DHA) + quercetin (QE) used in combination. DHA and QE are natural compounds derived from various foods and have been demonstrated to exert anti‑inflammatory effects The protein mRNA expression involved in the nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) signalling pathway was analyzed by western blot analysis and reverse transcription-polymerase chain reaction methods respectively, other cytokines were detected by an enzyme‑linked immunosorbent assay kit. The results of the present study demonstrated that combined treatment of lipopolysaccharide (LPS)‑stimulated RAW264.7 cells with DHA + QE decreased the levels of pro‑inflammatory mediators to a greater extent than QE or DHA alone. Additionally, DHA + QE synergistically suppressed nitric oxide, prostaglandin E2 and cyclooxygenase-2 levels. Molecular‑level studies indicated that the DHA + QE combination can significantly inhibit the mRNA expression of NF‑κB subunits p50 and p65, extracellular signal‑regulated kinase (ERK) 1/2 and c‑JUN N‑terminal kinase (JNK) 1/2, which suggests that the NF‑κB signalling pathway is involved in the synergistic effects observed. Furthermore, western blot analysis demonstrated that DHA + QE synergistically inhibit the phosphorylation of p50, p65, ERK1/2 and JNK1/2. This finding indicates that the enhanced anti‑inflammatory effects of the combined compounds are achieved by suppressing NF‑κB and MAPK signalling in LPS‑stimulated RAW264.7 cells. The results of the present study suggest that DHA and QE in combination may be utilized as potent anti‑inflammatory compounds, with potential preventative or palliative effects on obesity, atherosclerosis and cardiovascular diseases.

The Putative Role of Viruses, Bacteria, and Chronic Fungal Biotoxin Exposure in the Genesis of Intractable Fatigue Accompanied by Cognitive and Physical Disability

Patients who present with severe intractable apparently idiopathic fatigue accompanied by profound physical and or cognitive disability present a significant therapeutic challenge. The effect of psychological counseling is limited, with significant but very slight improvements in psychometric measures of fatigue and disability but no improvement on scientific measures of physical impairment compared to controls. Similarly, exercise regimes either produce significant, but practically unimportant, benefit or provoke symptom exacerbation. Many such patients are afforded the exclusionary, non-specific diagnosis of chronic fatigue syndrome if rudimentary testing fails to discover the cause of their symptoms. More sophisticated investigations often reveal the presence of a range of pathogens capable of establishing life-long infections with sophisticated immune evasion strategies, including Parvoviruses, HHV6, variants of Epstein-Barr, Cytomegalovirus, Mycoplasma, and Borrelia burgdorferi. Other patients have a history of chronic fungal or other biotoxin exposure. Herein, we explain the epigenetic factors that may render such individuals susceptible to the chronic pathology induced by such agents, how such agents induce pathology, and, indeed, how such pathology can persist and even amplify even when infections have cleared or when biotoxin exposure has ceased. The presence of active, reactivated, or even latent Herpes virus could be a potential source of intractable fatigue accompanied by profound physical and or cognitive disability in some patients, and the same may be true of persistent Parvovirus B12 and mycoplasma infection. A history of chronic mold exposure is a feasible explanation for such symptoms, as is the presence of B. burgdorferi. The complex tropism, life cycles, genetic variability, and low titer of many of these pathogens makes their detection in blood a challenge. Examination of lymphoid tissue or CSF in such circumstances may be warranted.

Omega-3 fatty acids in the prevention of interferon-alpha-induced depression: results from a randomized, controlled trial

BACKGROUND

Interferon (IFN)-α therapy for chronic hepatitis C virus infection is frequently associated with depression. The routine prophylaxis with antidepressants might expose patients to adverse effects, hence, the need for alternative preventive interventions. Omega-3 polyunsaturated fatty acids are safe and effective essential nutritional compounds used for the treatment of depression, putatively through an anti-inflammatory action. In addition, lower erythrocyte levels of omega-3 polyunsaturated fatty acids have been associated with an increased risk of IFN-induced depression.

METHODS

We conducted a 2-week, double-blind, placebo-controlled trial comparing eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and placebo for the prevention of IFN-α-induced depression. A total of 162 patients consented to participate and were randomized to the study. All of the patients completed the 2-week trial; 152 participants were followed throughout the 24 weeks of IFN-α treatment and were included in the analysis.

RESULTS

Compared with placebo, the incident rates of IFN-α-induced depression were significantly lower in EPA-treated but not in DHA-treated patients (10% and 28%, respectively, versus 30% for placebo, p = .037). Both EPA and DHA significantly delayed the onset of IFN-induced depression (week of onset: 12.0 and 11.7, respectively, versus 5.3 for placebo, p = .002). EPA and DHA were both well tolerated in this population. EPA treatment increased both EPA and DHA erythrocyte levels, but DHA only increased DHA erythrocyte levels.

CONCLUSIONS

EPA is effective in the prevention of depression in hepatitis C virus patients received IFN-α therapy. Our study confirms the notion that anti-inflammatory strategies are effective antidepressants in the context of depression associated with inflammation.

Molecular and Genetic Studies ofFusariumTrichothecene Biosynthesis: Pathways, Genes, and Evolution

Trichothecenes are a large family of sesquiterpenoid secondary metabolites of Fusarium species (e.g., F. graminearum) and other molds. They are major mycotoxins that can cause serious problems when consumed via contaminated cereal grains. In the past 20 years, an outline of the trichothecene biosynthetic pathway has been established based on the results of precursor feeding experiments and blocked mutant analyses. Following the isolation of the pathway gene Tri5 encoding the first committed enzyme trichodiene synthase, 10 biosynthesis genes (Tri genes; two regulatory genes, seven pathway genes, and one transporter gene) were functionally identified in the Tri5 gene cluster. At least three pathway genes, Tri101 (separated alone), and Tri1 and Tri16 (located in the Tri1-Tri16 two-gene cluster), were found outside of the Tri5 gene cluster. In this review, we summarize the current understanding of the pathways of biosynthesis, the functions of cloned Tri genes, and the evolution of Tri genes, focusing on Fusarium species.

Mechanisms of mycotoxin-induced neurotoxicity through oxidative stress-associated pathways

Among many mycotoxins, T-2 toxin, macrocyclic trichothecenes, fumonisin B(1) (FB(1)) and ochratochin A (OTA) are known to have the potential to induce neurotoxicity in rodent models. T-2 toxin induces neuronal cell apoptosis in the fetal and adult brain. Macrocyclic trichothecenes bring about neuronal cell apoptosis and inflammation in the olfactory epithelium and olfactory bulb. FB(1) induces neuronal degeneration in the cerebral cortex, concurrent with disruption of de novo ceramide synthesis. OTA causes acute depletion of striatal dopamine and its metabolites, accompanying evidence of neuronal cell apoptosis in the substantia nigra, striatum and hippocampus. This paper reviews the mechanisms of neurotoxicity induced by these mycotoxins especially from the viewpoint of oxidative stress-associated pathways.

Toxicological mechanisms and potential health effects of deoxynivalenol and nivalenol

Produced by the mould genus Fusarium, the type B trichothecenes include deoxynivalenol (DON), nivalenol (NIV) and their acetylated precursors. These mycotoxins often contaminate cereal staples, posing a potential threat to public health that is still incompletely understood. Understanding the mechanistic basis by which these toxins cause toxicity in experimental animal models will improve our ability to predict the specific thresholds for adverse human effects as well as the persistence and reversibility of these effects. Acute exposure to DON and NIV causes emesis in susceptible species such as pigs in a manner similar to that observed for certain bacterial enterotoxins. Chronic exposure to these mycotoxins at low doses causes growth retardation and immunotoxicity whereas much higher doses can interfere with reproduction and development. Pathophysiological events that precede these toxicities include altered neuroendocrine responses, upregulation of proinflammatory gene expression, interference with growth hormone signalling and disruption of gastrointestinal tract permeability. The underlying molecular mechanisms involve deregulation of protein synthesis, aberrant intracellular cell signalling, gene transactivation, mRNA stabilisation and programmed cell death. A fusion of basic and translational research is now needed to validate or refine existing risk assessments and regulatory standards for DON and NIV. From the perspective of human health translation, biomarkers have been identified that potentially make it possible to conduct epidemiological studies relating DON consumption to potential adverse human health effects. Of particular interest will be linkages to growth retardation, gastrointestinal illness and chronic autoimmune diseases. Ultimately, such knowledge can facilitate more precise science-based risk assessment and management strategies that protect consumers without reducing availability of critical food sources.

Docosahexaenoic acid suppresses neuroinflammatory responses and induces heme oxygenase-1 expression in BV-2 microglia: implications of antidepressant effects for ω-3 fatty acids

Accumulating evidence suggests that the pathophysiology of depression might be associated with neuroinflammation, which could be attenuated by pharmacological treatment for depression. Omega-3 polyunsaturated fatty acids (PUFAs) are anti-inflammatory and exert antidepressant effects. The aim of this study was to identify the molecular mechanisms through which docosahexaenoic acid (DHA), the main omega-3 PUFA in the brain, modulates oxidative reactions and inflammatory cytokine production in microglial and neuronal cells. The results of this study showed that DHA reduced expressions of tumor necrosis factor-α, interleukin-6, nitric oxide synthase, and cyclo-oxygenase-2, induced by interferon-γ, and induced upregulation of heme oxygenase-1 (HO-1) in BV-2 microglia. The inhibitory effect of DHA on nitric oxide production was abolished by HO-1 inhibitor zinc protoporphyrin IX. In addition, DHA caused AKT and ERK activation in a time-dependent manner, and the DHA-induced HO-1 upregulation could be attenuated by PI-3 kinase/AKT and MEK/ERK inhibitors. DHA also increased IKKα/β phosphorylation, IκBα phosphorylation, and IκBα degradation, whereas both nuclear factor-κB and IκB protease inhibitors could inhibit DHA-induced HO-1 expressions. The other major n-3 PUFA, eicosapentaenoic acid, showed similar effects of DHA on inflammation and HO-1 in repeated key experiments. In connecting with inflammation hypothesis of depression and clinical studies supporting the antidepressant effects of omega-3 PUFAs, this study provides a novel implication of the antidepressant mechanisms of DHA.

Deoxynivalenol-induced proinflammatory gene expression: mechanisms and pathological sequelae

The trichothecene mycotoxin deoxynivalenol (DON) is commonly encountered in human cereal foods throughout the world as a result of infestation of grains in the field and in storage by the fungus Fusarium. Significant questions remain regarding the risks posed to humans from acute and chronic DON ingestion, and how to manage these risks without imperiling access to nutritionally important food commodities. Modulation of the innate immune system appears particularly critical to DON's toxic effects. Specifically, DON induces activation of mitogen-activated protein kinases (MAPKs) in macrophages and monocytes, which mediate robust induction of proinflammatory gene expression-effects that can be recapitulated in intact animals. The initiating mechanisms for DON-induced ribotoxic stress response appear to involve the (1) activation of constitutive protein kinases on the damaged ribosome and (2) autophagy of the chaperone GRP78 with consequent activation of the ER stress response. Pathological sequelae resulting from chronic low dose exposure include anorexia, impaired weight gain, growth hormone dysregulation and aberrant IgA production whereas acute high dose exposure evokes gastroenteritis, emesis and a shock-like syndrome. Taken together, the capacity of DON to evoke ribotoxic stress in mononuclear phagocytes contributes significantly to its acute and chronic toxic effects in vivo. It is anticipated that these investigations will enable the identification of robust biomarkers of effect that will be applicable to epidemiological studies of the human health effects of this common mycotoxin.

n-3 polyunsaturated fatty acids and autoimmune-mediated glomerulonephritis

Consumption of n-3 polyunsaturated fatty acids (PUFAs) found in fish oil suppresses inflammatory processes making these fatty acids attractive candidates for both the prevention and amelioration of several organ-specific and systemic autoimmune diseases. Both pre-clinical and clinical studies have been conducted to determine whether fish oils containing the n-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) can be used in the prevention and treatment of immunoglobulin A nephropathy (IgAN) and lupus nephritis. In a toxin-induced mouse model that mimics the early stages of IgAN, n-3 PUFA consumption suppresses aberrant interleukin (IL)-6-driven IgA production and mesangial IgA immune complex deposition by impairing phosphorylation of upstream kinases and activation of transcription factors essential for IL-6 gene transcription. n-3 PUFAs can also suppress production of anti-double-stranded DNA IgG antibodies and the resultant development of lupus nephritis in the NZBW F1 mouse and related models. These effects have been linked in part to impaired expression of proinflammatory cytokines and adhesion molecules as well as increases in antioxidant enzymes in kidney and immune organs. Several recent clinical trials have provided compelling evidence that n-3 PUFA supplementation could be useful in treatment of human IgAN and lupus nephritis, although some other studies suggest such supplementation might be without benefit. Future investigations employing genomics/proteomics and novel genetically altered mice should provide further insight into how n-3 PUFAs modulate these diseases as well help to identify clinically relevant biomarkers. The latter could be employed in future well-designed, long-term clinical studies that will resolve current controversies on n-3 PUFA efficacy in autoimmune-mediated glomerulonephritis.

n-3 PUFA improves fatty acid composition, prevents palmitate-induced apoptosis, and differentially modifies B cell cytokine secretion in vitro and ex vivo

n-3 polyunsaturated fatty acids (PUFAs) modify T-cell activation, in part by remodeling lipid composition; however, the relationship between n-3 PUFA and B-cell activation is unknown. Here we tested this relationship in vitro and ex vivo by measuring upregulation of B-cell surface molecules, the percentage of cells activated, and cytokine secreted in response to lipopolysaccharide (LPS) activation. In vitro, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) improved the membrane n-6/n-3 PUFA ratio, and DHA lowered interleukin (IL)-6 secretion; overall, n-3 PUFAs did not suppress B-cell activation compared with BSA, oleate, or elaidate treatment. Palmitate treatment suppressed the percentage of B cells activated through lipoapoptosis, which was differentially prevented by cosupplementing cells with MUFAs and PUFAs. Ex vivo, we tested the hypothesis with mice fed a control or high-fat saturated, hydrogenated, MUFA or n-3 PUFA diets. n-3 PUFAs had no effect on the percentage of B cells activated. Unexpectedly, the n-3 PUFA diet increased B-cell CD69 surface expression, IL-6 and IFNgamma secretion, and it significantly increased body weight gain. Overall, we propose that changes in lipid composition with n-3 PUFA and suppression of lymphocyte activation is not universal. The study highlights that high-fat n-3 PUFA diets can promote pro-inflammatory responses, at least from one cell type.

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.

Docosahexaenoic acid downregulates phenobarbital-induced cytochrome P450 2B1 gene expression in rat primary hepatocytes via the c-Jun NH2-terminal kinase mitogen-activated protein kinase pathway

Mitogen-activated protein kinase (MAPK) pathways play central roles in the transduction of extracellular stimuli into cells and the regulation of expression of numerous genes. Docosahexaenoic acid (DHA) was shown to be involved in the regulation of expression of drug metabolizing enzymes (DMEs) in rat primary hepatocytes in response to xenobiotics. Cytochrome P450 2B1 (CYP 2B1) is a DME that is dramatically induced by phenobarbital-type inducers. The constitutive androstane receptor (CAR) plays a critical role in regulating the expression of DMEs, and the phosphorylation/dephosphorylation of CAR is an important event in CYP 2B1 expression. In the present study, we determined the effect of DHA on MAPK transactivation and its role in CYP 2B1 expression induced by phenobarbital. c-Jun NH2-terminal kinase (JNK) JNK1/2 and ERK1/2 were activated by phenobarbital in a dose-dependent manner. DHA (100 muM) inhibited JNK1/2 and ERK2 activation induced by phenobarbital in a time-dependent manner. Both SP600125 (a JNK inhibitor) and SB203580 (a p38 MAPK inhibitor) inhibited CYP 2B1 protein and mRNA expression induced by phenobarbital. SB203580 significantly increased the intracellular 3'-5'-cyclic adenosine monophosphate (cAMP) concentration compared with a control group (p < 0.05). Our results suggest that inhibition of JNK activation by DHA is at least part of the mechanisms of DHA's downregulation of CYP 2B1 expression induced by phenobarbital.

Overexpression of human histone methylase MLL1 upon exposure to a food contaminant mycotoxin, deoxynivalenol

Mixed lineage leukemias (MLLs) are histone-methylating enzymes with critical roles in gene expression, epigenetics and cancer. Although MLLs are important gene regulators little is known about their own regulation. Herein, to understand the effects of toxic stress on MLL gene regulation, we treated human cells with a common food contaminant mycotoxin, deoxynivalenol (DON). Our results demonstrate that MLLs and Hox genes are overexpressed upon exposure to DON. Studies using specific inhibitors demonstrated that Src kinase families are involved in upstream events in DON-mediated upregulation of MLL1. Sequence analysis demonstrated that the MLL1 promoter contains multiple Sp1-binding sites and importantly, the binding of Sp1 is enriched in the MLL1 promoter upon exposure to DON. Moreover, antisense-mediated knockdown of Sp1 diminished DON-induced MLL1 upregulation. These results demonstrated that MLL1 gene expression is sensitive to toxic stress and Sp1 plays crucial roles in the stress-induced upregulation of MLL1.

Uncoupling of interleukin-6 from its signalling pathway by dietary n-3-polyunsaturated fatty acid deprivation alters sickness behaviour in mice

Sickness behaviour is an adaptive behavioural response to the activation of the innate immune system. It is mediated by brain cytokine production and action, especially interleukin-6 (IL-6). Polyunsaturated fatty acids (PUFA) are essential fatty acids that are highly incorporated in brain cell membranes and display immunomodulating properties. We hypothesized that a decrease in n-3 (also known as omega3) PUFA brain level by dietary means impacts on lipopolysaccharide (LPS)-induced IL-6 production and sickness behaviour. Our results show that mice exposed throughout life to a diet containing n-3 PUFA (n-3/n-6 diet) display a decrease in social interaction that does not occur in mice submitted to a diet devoid of n-3 PUFA (n-6 diet). LPS induced high IL-6 plasma levels as well as expression of IL-6 mRNA in the hippocampus and cFos mRNA in the brainstem of mice fed either diet, indicating intact immune-to-brain communication. However, STAT3 and STAT1 activation, a hallmark of the IL-6 signalling pathway, was lower in the hippocampus of LPS-treated n-6 mice than n-3/n-6 mice. In addition, LPS did not reduce social interaction in IL-6-knockout (IL-6-KO) mice and failed to induce STAT3 activation in the brain of IL-6-KO mice. Altogether, these findings point to alteration in brain STAT3 as a key mechanism for the lack of effect of LPS on social interaction in mice fed with the n-6 PUFA diet. The relative deficiency of Western diets in n-3 PUFA could impact on behavioural aspects of the host response to infection.

Eicosapentaenoic acid is more effective than docosahexaenoic acid in inhibiting proinflammatory mediator production and transcription from LPS-induced human asthmatic alveolar macrophage cells

BACKGROUND & AIMS

The purpose of the study was to determine which of the active constituents of fish oil, eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), is most effective in suppressing proinflammatory mediator generation and cytokine expression from LPS-stimulated human asthmatic alveolar macrophages (AMphi).

METHODS

The AMphi were obtained from twenty-one asthmatic adults using fiberoptic bronchoscopy. Cells were pretreated with DMEM, pure EPA, an EPA-rich media (45% EPA/10% DHA), pure DHA, a DHA-rich media (10% EPA/50% DHA) or Lipovenos (n-6 PUFA), and then exposed to Dulbecco's Modified Eagle's Medium (DMEM) (-) or LPS (+). Supernatants were analyzed for leukotriene (LT)B(4), prostaglandin (PG)D(2), tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta production. Detection of TNF-alpha and IL-1beta mRNA expression levels was quantified by reverse transcriptase polymerase chain reaction.

RESULTS

120 microM pure EPA and EPA-rich media significantly (p<0.05) suppressed TNF-alpha and IL-1beta mRNA expression and the production of LTB(4), PGD(2) and TNF-alpha and IL-1beta in LPS-stimulated primary AMphi cells obtained from asthmatic patients to a much greater extent than 120 microM pure DHA and DHA-rich media respectively.

CONCLUSIONS

This study has shown for the first time that EPA is a more potent inhibitor than DHA of inflammatory responses in human asthmatic AMphi cells.

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.

Reduction in Cerebral Atrophy Associated with Ethyl-Eicosapentaenoic Acid Treatment in Patients with Huntington's Disease

Ultra-pure ethyl-eicosapentaenoic acid (ethyl-EPA), a semi-synthetic ethyl ester of eicosapentaenoic acid, is associated with clinical improvement in motor functioning in Huntington's disease. The aim was to determine the extent to which it might reduce the rate of progress of cerebral atrophy. High-resolution cerebral magnetic resonance imaging scans were acquired at baseline, 6 months and 1 year in up to 34 patients with stage I or II Huntington's disease who took part in a randomized, double-blind, placebo-controlled trial of ethyl-EPA. For each subject and each pair of structural images, the two-timepoint brain volume change was calculated in a double-blind manner. Significant group-level reductions in brain atrophy were observed in the head of the caudate nucleus and the posterior thalamus. These findings show that treatment with ethyl-EPA is associated with significant reduction in brain atrophy, particularly in the caudate and thalamus. No other drug tested in Huntington's disease has shown this effect.

Mechanisms of deoxynivalenol-induced gene expression and apoptosis

Fusarium infection of agricultural staples such as wheat, barley and corn with concurrent production of deoxynivalenol (DON) and other trichothecene mycotoxins is an increasingly common problem worldwide. In addition to its emetic effects, chronic dietary exposure to DON causes impaired weight gain, anorexia, decreased nutritional efficiency and immune dysregulation in experimental animals. Trichothecenes are both immunostimulatory or immunosuppressive depending on dose, frequency and duration of exposure as well as type of immune function assay. Monocytes, macrophages, as well as T- and B-lymphocytes of the immune system can be cellular targets of DON and other trichothecenes. In vitro exposure to low trichothecene concentrations upregulates expression both transcriptionally and post-transcriptionally of cytokines, chemokines and inflammatory genes with concurrent immune stimulation, whereas exposure to high concentrations promotes leukocyte apoptosis with concomitant immune suppression. DON and other trichothecenes, via a mechanism known as the 'ribotoxic stress response', bind to ribosomes and rapidly activate mitogen-activated protein kinases (MAPKs). The latter are important transducers of downstream signalling events related to immune response and apoptosis. Using cloned macrophages, two critical upstream transducers of DON-induced MAPK activation have been identified. One transducer is double-stranded RNA (dsRNA)-activated protein kinase (PKR), a widely expressed serine/threonine protein kinase that can be activated by dsRNA, interferon and other agents. The other transducer is haematopoetic cell kinase (Hck), a non-receptor associated Src oncogene family kinase. Pharmacological inhibitors and gene suppression studies have revealed that Hck and PKR contribute to DON-induced gene expression and apoptosis. PKR, Hck and other kinases bind to the ribosome and are activated following DON interaction. Future studies will focus on the sequence of molecular events at the ribosome level that drive selective activation of these upstream kinases.

Mechanisms for suppression of interleukin-6 expression in peritoneal macrophages from docosahexaenoic acid-fed mice

Consumption of the trichothecene mycotoxin deoxynivalenol (DON) induces interleukin-6 (IL-6)-dependent IgA nephropathy (IgAN) in mice. This effect can be prevented by feeding long-chain n-3 polyunsaturated fatty acids (PUFAs) found in fish oil. The purpose of this study was to identify the signal transduction pathways by which DON up-regulates IL-6 in the peritoneal macrophage and how consumption of fish oil enriched with the n-3 PUFA docosahexaenoic acid (DHA) suppresses these processes. Incubation with DON induced IL-6 expression in naïve macrophages maximally at 3 h. Knockdown of the transcription factor cAMP response element-binding protein (CREB) or pharmacologic inhibition of the CREB kinases Akt1/2, MSK1 and RSK1 down-regulated this expression. Inhibition of double-stranded RNA-activated protein kinase (PKR) suppressed not only IL-6 expression but also phosphorylation of CREB and its upstream kinases, Akt1, MSK1 and RSK1. Phosphorylations of PKR, CREB kinases and CREB were markedly impaired in peritoneal macrophages isolated from mice that consumed DHA-enriched fish oil for 6 to 8 weeks. DHA's effects were not explainable by increased activity of protein phosphatase 1 and 2A since both were suppressed in mice consuming the DHA diet. Although cells cultured directly with DHA expressed less IL-6 compared to cells cultured with arachidonic acid (AA), neither fatty acid treatment affected DON-induced protein phosphorylation. Furthermore, DHA and AA similarly inhibited cell-free protein kinase activity. These data suggest that DON-induced IL-6 expression is CREB mediated and PKR dependent, and that requisite kinase activities for these pathways were suppressed in macrophages from mice fed DHA for an extended period.

Comparative induction of 28S ribosomal RNA cleavage by ricin and the trichothecenes deoxynivalenol and T-2 toxin in the macrophage

Ribosome-inactivating proteins (RIPs) and sesquiterpenoid trichothecene mycotoxins are known to bind to eukaryotic ribosomes, inhibit translation and activate mitogen-activated protein kinases. Here we compared the capacities of the RIP ricin to promote 28S ribosomal RNA (rRNA) cleavage with that of the trichothecenes, deoxynivalenol (DON), and T-2 toxin (T-2). In a cell-free model, exposure to ricin at 300 ng/ml for 30 min depurinated yeast 28S rRNA, however, neither DON (< or = 4 microg/ml) nor T-2 (< or = 2 microg/ml) exhibited this N-glycosidase activity. Incubation of RAW 264.7 macrophages with ricin (20-320 ng/ml), DON (250-5000 ng/ml), or T-2 (2-80 ng/ml) for 6 h, however, generated 28S rRNA-specific products consistent with cleavage sites near the 3' terminal end of murine 28S rRNA. Oligonucleotide extension analysis of treated RAW 264.7 cells revealed that ricin evoked 28S rRNA damage at one site in the alpha-sarcin/ricin (S/R)-loop (A4256) and two other sites (A3560 and A4045) in the peptidyl transferase center. Although DON or T-2 did not damage the S/R loop, these trichothecenes did promote cleavage at A3560 and A4045. In addition, incubation of the cells with ricin (> or = 20 ng/ml), DON (> or = 250 ng/ml), or T-2 (> or = 10 ng/ml) induced RNase activity as well as RNase L mRNA and protein expression. These data suggest that only ricin directly damaged 28S rRNA under cell-free conditions but that ricin, DON, and T-2 promoted intracellular 28S rRNA cleavage, potentially by facilitating the action of endogenous RNases and/or by upregulating RNase expression.

Stachybotrys chartarum, trichothecene mycotoxins, and damp building-related illness: new insights into a public health enigma

Damp building-related illnesses (DBRI) include a myriad of respiratory, immunologic, and neurologic symptoms that are sometimes etiologically linked to aberrant indoor growth of the toxic black mold, Stachybotrys chartarum. Although supportive evidence for such linkages is limited, there are exciting new findings about this enigmatic organism relative to its environmental dissemination, novel bioactive components, unique cellular targets, and molecular mechanisms of action which provide insight into the S. chartarum's potential to evoke allergic sensitization, inflammation, and cytotoxicity in the upper and lower respiratory tracts. Macrocyclic trichothecene mycotoxins, produced by one chemotype of this fungus, are potent translational inhibitors and stress kinase activators that appear to be a critical underlying cause for a number of adverse effects. Notably, these toxins form covalent protein adducts in vitro and in vivo and, furthermore, cause neurotoxicity and inflammation in the nose and brain of the mouse. A second S. chartarum chemotype has recently been shown to produce atranones-mycotoxins that can induce pulmonary inflammation. Other biologically active products of this fungus that might contribute to pathophysiologic effects include proteinases, hemolysins, beta-glucan, and spirocyclic drimanes. Solving the enigma of whether Stachybotrys inhalation indeed contributes to DBRI will require studies of the pathophysiologic effects of low dose chronic exposure to well-characterized, standardized preparations of S. chartarum spores and mycelial fragments, and, coexposures with other environmental cofactors. Such studies must be linked to improved assessments of human exposure to this fungus and its bioactive constituents in indoor air using both state-of-the-art sampling/analytical methods and relevant biomarkers.

Dietary docosahexaenoic acid and docosapentaenoic acid ameliorate amyloid-beta and tau pathology via a mechanism involving presenilin 1 levels

The underlying cause of sporadic Alzheimer disease (AD) is unknown, but a number of environmental and genetic factors are likely to be involved. One environmental factor that is increasingly being recognized as contributing to brain aging is diet, which has evolved markedly over modern history. Here we show that dietary supplementation with docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, in the 3xTg-AD mouse model of AD reduced the intraneuronal accumulation of both amyloid-beta (Abeta) and tau. In contrast, combining DHA with n-6 fatty acids, either arachidonic acid or docosapentaenoic acid (DPAn-6), diminished the efficacy of DHA over a 12 month period. Here we report the novel finding that the mechanism accounting for the reduction in soluble Abeta was attributable to a decrease in steady-state levels of presenilin 1, and not to altered processing of the amyloid precursor protein by either the alpha- or beta-secretase. Furthermore, the presence of DPAn-6 in the diet reduced levels of early-stage phospho-tau epitopes, which correlated with a reduction in phosphorylated c-Jun N-terminal kinase, a putative tau kinase. Collectively, these results suggest that DHA and DPAn-6 supplementations could be a beneficial natural therapy for AD.

Polyunsaturated fatty acid supplementation alters proinflammatory gene expression and reduces the incidence of necrotizing enterocolitis in a neonatal rat model

Although supplementation of preterm formula with polyunsaturated fatty acids (PUFA) has been shown to reduce the incidence of necrotizing enterocolitis (NEC) in animal models and clinical trials, the mechanisms remain elusive. We hypothesized that the protective effect of PUFA on NEC may be due to the ability of PUFA to suppress Toll-like receptor (TLR) 4 and platelet-activating factor receptor (PAFR) gene expression (molecules that are important in the pathogenesis of NEC) in epithelial cells. To investigate the efficacy of different PUFA preparations on NEC in a neonatal rat model, we compared the incidence of NEC among the four PUFA supplemented groups--A: arachidonic acid and docosahexaenoic acid (AA+DHA), B: egg phospholipids (EP), C: DHA, and D: control without PUFA. PUFA supplementation reduced the incidence of NEC and inhibited intestinal PAFR and TLR4 gene expression compared with the controls. To validate the in vivo observations, IEC-6 cells were exposed to PAF after pretreatment with AA or DHA. Both AA and DHA supplementation blocked PAF-induced TLR4 and PAFR mRNA expression in these enterocytes. These results suggest that PUFA modulates gene expression of key factors involved in experimental NEC pathogenesis. These effects might in part explain the protective effect of PUFA on neonatal NEC.

Mycotoxins in pet food: a review on worldwide prevalence and preventative strategies

Mycotoxins contaminate cereal grains worldwide, and their presence in pet food has been a potential health threat to companion animals. Aflatoxins, ochratoxin A, and Fusarium mycotoxins have been found in both raw ingredients and final products of pet food around the globe. Aflatoxin, a hepatotoxin and carcinogen, has caused several food poisoning outbreaks in dogs, and aflatoxin content is regulated in pet food in many countries. Ochratoxin A and Fusarium mycotoxins including trichothecenes, zearalenone, and fumonisins may have chronic effects on the health of companion animals. Grain processing, sampling error, analytical methods, conjugated mycotoxins, storage conditions, and synergistic interactions are common challenges faced by the pet food industry. Food-processing techniques such as sieving, washing, pearling, ozonation, and acid-based mold inhibition reduce the mycotoxin content of cereal grains. Dietary supplementation with large neutral amino acids, antioxidants, and omega-3 polysaturated fatty acids as well as inclusion of mycotoxin-sequestering agents and detoxifying microbes may ameliorate the harmful effects of mycotoxins in contaminated pet food.

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.

Eicosapentaenoic acid prevents endothelin-1-induced cardiomyocyte hypertrophy in vitro through the suppression of TGF-beta 1 and phosphorylated JNK

The cardiovascular benefit of fish oil in humans and experimental animals has been reported. Endothelin (ET)-1 is a well-known cardiac hypertrophic factor. However, although many studies link a fish oil extract, eicosapentaenoic acid (EPA), to cardiac protection, the effects of EPA on cardiac hypertrophy and underlying mechanism(s) are unclear. The present study investigated whether EPA prevents ET-1-induced cardiomyocyte hypertrophy; the potential pathways likely to underlie such an effect were also investigated. Cardiomyocytes were isolated from neonatal rat heart, cultured for 3 days, and then treated for 24 h with vehicle only (control), treated with 0.1 nM ET-1 only, or pretreated with 10 microM EPA and then treated with 0.1 nM ET-1. The cells were harvested, and changes in cell surface area, protein synthesis, expression of a cytoskeletal (alpha-actinin) protein, and cell signaling were analyzed. ET-1 induced a 97% increase in cardiomyocyte surface area, a 72% increase in protein synthesis rate, and an increase in expression of alpha-actinin and signaling molecule [transforming growth factor-beta 1 (TGF-beta 1), c-Jun NH2-terminal kinase (JNK), and c-Jun]. Development of these ET-1-induced cellular changes was attenuated by EPA. Moreover, the hypertrophied cardiomyocytes showed a 1.5- and a 1.7-fold increase in mRNA expression of atrial and brain natriuretic peptides, the classical molecular markers of cardiac hypertrophy, respectively; these changes were also suppressed by EPA. Here we show that ET-1 induces cardiomyocyte hypertrophy and expression of hypertrophic markers, possibly mediated by JNK and TGF-beta 1 signaling pathways. These ET-1-induced effects were blocked by EPA, a major fish oil ingredient, suggesting that fish oil may have beneficial protective effects on cardiac hypertrophy.

Docosahexaenoic acid consumption inhibits deoxynivalenol-induced CREB/ATF1 activation and IL-6 gene transcription in mouse macrophages

The mycotoxin deoxynivalenol (DON) induces IgA nephropathy in mice by upregulating IL-6 expression, which is suppressed by (n-3) PUFA consumption. The purpose of this study was to test the hypothesis that consumption of the (n-3) PUFA docosahexaenoic acid (DHA) interferes with DON-induced transcriptional and post-transcriptional upregulation of IL-6 mRNA in murine macrophages. DON evoked expression of IL-6 mRNA and IL-6 heterogenous nuclear RNA (hnRNA), an indicator of ongoing IL-6 transcription, in macrophages elicited from mice fed control AIN-93G diet for 4 wk, whereas expression of both RNA species was suppressed in macrophages from mice fed AIN-93G modified to contain 30 g DHA/kg diet for the same time period. DON enhanced IL-6 mRNA stability similarly in macrophages from control and DHA-fed mice suggesting that (n-3) PUFA effects were not post-transcriptional. DON upregulated binding activity of cAMP response element binding protein (CREB) and activator protein (AP-1) to their respective consensus sequences in nuclear extracts from control-fed mice, whereas both activities were suppressed in nuclear extracts from DHA-fed mice. DON induced phosphorylation of CREB at Ser-133 and ATF1 at Ser-63 as well as intranuclear binding of phospho-CREB/ATF1 to the cis element of the IL-6 promoter in control macrophages, whereas both activities were inhibited in macrophages from DHA-fed mice. DHA consumption blocked DON-induced phosphorylation of the CREB kinase AKT. Inhibition of AKT suppressed both CREB/ATF1 phosphorylation and IL-6 transcription. These data suggest that DHA consumption suppresses DON-induced IL-6 transcription in macrophages in part by interfering with AKT-dependent phosphorylation and subsequent binding of CREB/ATF1 to the IL-6 promoter.

In vitro and in vivo effects of deoxynivalenol (DNV) on regulators of cap dependent translation control in porcine endometrium

Deoxynivalenol (DNV) is the most frequently encountered trichothecene in grain-based foods, and is able to produce toxic effects resulting in various diseases in farm and laboratory animals. The molecular mechanisms that control this mycotoxin mediated effects in porcine endometrial cells are far from being completely understood. Recent results show that DNV inhibits protein synthesis in actively proliferating tissues. Therefore, the present study investigated the effects of this mycotoxin on a cellular level in an in vivo and in vitro system. The abundance and phosphorylation state (activity) of the cell cycle dependent kinases MAPk and Akt (PKB) and their potential targets eIF-4E (eukaryotic initiation factor 4E) and 4E-BP1 (4E binding protein, eIF4E repressor protein) were examined. In previous investigations it was found that these factors are involved in initiation of mRNA translation. The results show that DNV in vitro strongly reduce the abundance of p38 MAPk, protein kinase Akt and the alpha- and beta-4E-BP1 bands. The phosphorylation state of these proteins was obviously not modulated. In contrast, the eIF4E phosphorylation was strongly reduced in DNV treated cells. In summary, our in vitro results let assume that DNV potentially influences gene expression, but this work does not present a direct proof that DNV alters processes, which are involved in the initiation of mRNA translation. Surprisingly in vivo, an influence of DNV feeding on the investigated molecular events could not be demonstrated.

Truncated deoxynivalenol-induced splenic immediate early gene response in mice consuming (n-3) polyunsaturated fatty acids

Expression profiling has previously revealed that acute exposure to the common foodborne mycotoxin deoxynivalenol (DON) induces a large number of immediate early genes in murine lymphoid tissues that potentially affect immune function. The purpose of this study was to test the hypothesis that consumption of (n-3) polyunsaturated fatty acids (PUFAs) found in fish oil interferes with DON-induced immediate early gene expression. Mice were fed AIN-93G diet containing 1% corn oil (CO) plus 6% oleic acid (control) or a diet containing 1% CO, 2% fish oil enriched in the (n-3)-PUFAs docosahexaenoic and eicosapentaenoic acid and 4% oleic acid. After 12 weeks, the mice were gavaged orally with 25 mg/kg DON and the kinetics of immediate early gene expression in spleen monitored over 8 h by real-time polymerase chain reaction (PCR). Deoxynivalenol was found to readily induce expression of cytokines (IL-1alpha, IL-1beta, and IL-6 and IL-11), chemokines (MCP-1, MCP-3, CINC-1 and MIP-2), components of the activator protein-1 (AP-1) transcription factor complex (c-Fos, Fra-2, c-Jun and JunB), as well as two hydrolases (MKP1, CnAbeta). Expression of these genes was transient, peaking within 2-4 h and declining thereafter, with the single exception being IL-11 that was elevated at 8 h. (n-3)-PUFA consumption significantly suppressed DON-induced expression of IL-1alpha, IL-6, IL-11, MCP-1, MCP-3, MIP-2 and Fra-2 at 8 h. In contrast, mice fed (n-3)-PUFA exhibited significant increases in MKP1 and CnAbeta expression. Taken together, these data suggest that dietary supplementation with (n-3)-PUFAs prematurely truncated cytokine, chemokine and transcription factor expression responses to DON that may impact its previously described capacity to disrupt immune function including immunoglobulin A (IgA) production. Since expression of many of these genes has been linked to mitogen-activated protein kinase (MAPK) activation, enhanced expression of MKP1, a negative MAPK regulator in (n-3)-PUFA-fed mice might contribute to this suppression.

Induction of competing apoptotic and survival signaling pathways in the macrophage by the ribotoxic trichothecene deoxynivalenol

Deoxynivalenol (DON) and other ribotoxic trichothecenes cause immune stimulation and suppression in leukocytes by upregulating gene expression and apoptosis, respectively. The purpose of this study was to test the hypothesis that MAPKs mediate both apoptosis and survival in DON-exposed macrophages. At concentrations which partially inhibit translation, DON induced phosphorylation of p38 and ERK 1/2 mitogen activated protein kinases within 15 min in RAW 264.7 macrophages and these effects lasted up to 3 h. DON-exposed cells exhibited marked caspase 3-dependent DNA fragmentation after 6 h which was suppressed and attenuated by the p38 inhibitor SB203580 and ERK inhibitor PD98059, respectively. DON readily induced the phosphorylation and activity of p53 and this was inhibitable by SB203580. DON exposure evoked BAX translocation to mitochondria and corresponding cytochrome C release but did not alter mitochondrial membrane potential. The p53 inhibitor PFTalpha reduced both DON-induced phosphorylation of p53 and p53 binding activity. Moreover, both PFTalpha and p53 siRNA transfection suppressed DON-induced caspase-3 activity and subsequent DNA fragmentation. Concurrent with p53 activation, DON activated two anti-apoptotic survival pathways as evidenced by both ERK-dependent p90 Rsk and AKT activation. Taken together, the results indicate that DON initiates competing apoptotic (p38/p53/Bax/Mitochondria/Caspase-3) and survival (ERK/AKT/p90Rsk/Bad) pathways in the macrophage.

Modulation of Murine Host Response to Enteric Reovirus Infection by the Trichothecene Deoxynivalenol

Based on the known capacity of deoxynivalenol (DON) to target gut lymphoid tissue and IgA production, it was hypothesized that this mycotoxin interferes with the immune response to enteric reovirus infection. When mice were orally gavaged, first with 25 mg/kg bw DON, and then with reovirus serotype 1, strain Lang (T1/L) 2 or 12 h later, viral titers in the GI tract were 10-fold higher than control mice after 5 days. Virus was almost completely cleared in both treatment and control groups from intestinal tissue after 10 days. Real-time PCR indicated that, in infected control mice, reovirus lambda2 core spike (L2 gene) RNA per g feces in infected mice that were pretreated with DON was significantly higher at 1, 3, and 5 days than in infected mice only. In reovirus-infected mice, DON at doses of 10 and 25 mg/kg bw but not 2 and 5 mg/kg bw increased fecal L2 RNA, whereas DON doses as low as 2 mg/kg potentiated L2 RNA levels in Peyer's patches (PP). Reovirus-specific IgA levels in feces of mice treated with DON were significantly elevated, as were specific IgA responses in lamina propria and PP fragment cultures. Similar effects were observed for serum IgA and IgG. DON suppressed IFN-gamma responses in PP to reovirus at 3 and 5 days as compared to infected controls, while IL-2 mRNA concentrations were unaffected. Although reovirus alone did not induce Th2 cytokine mRNAs in PP, DON exposure significantly elevated IL-4, IL-6, and IL-10 mRNA expression at various times during the infection. ELISPOT revealed that mRNA expression data corresponded to suppression of IFN-gamma- and enhancement of IL-4-producing cell responses in PP cultures from DON-treated mice. Taken together, these data suggest that DON transiently increased both severity of the reovirus infection and shedding in feces as well as elevated reovirus IgA responses. These effects corresponded to suppressed Th1 and enhanced Th2 cytokine expression.

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.

n-3 PUFAs reduce VEGF expression in human colon cancer cells modulating the COX-2/PGE2 induced ERK-1 and -2 and HIF-1alpha induction pathway

n-3 Polyunsaturated fatty acids (PUFAs) inhibit the development of microvessels in mammary tumors growing in mice. Human colorectal tumors produce vascular endothelial growth factor (VEGF) whose expression is up-regulated in tumor cells by both cyclooxygenase-2 (COX-2) and PGE(2) and directly correlated to neoangiogenesis and clinical outcome. The goal of this study was to examine the capability of n-3 PUFAs to regulate VEGF expression in HT-29 human colorectal cells in vitro and in vivo. Constitutive VEGF expression was augmented in cultured HT-29 cells by serum starvation and the effects of eicosapentaenoic (EPA) or docosahexaenoic acid (DHA) on VEGF, COX-2, phosphorylated extracellular signal-regulated kinase (ERK)-1 and -2 and hypoxia-inducible-factor 1-alpha (HIF-1alpha) expression and PGE(2) levels were assessed. Tumor growth, VEGF, COX and PGE(2) analysis were carried out in tumors derived from HT-29 cells transplanted in nude mice fed with either EPA or DHA. Both EPA and DHA reduced VEGF and COX-2 expression and PGE(2) levels in HT-29 cells cultured in vitro. Moreover, they inhibited ERK-1 and -2 phosphorylation and HIF-1alpha protein over-expression, critical steps in the PGE(2)-induced signaling pathway leading to the augmented expression of VEGF in colon cancer cells. EPA always showed higher efficacy than DHA in vitro. Both fatty acids decreased the growth of the tumors obtained by inoculating HT-29 cells in nude mice, microvessel formation and the levels of VEGF, COX-2 and PGE(2) in tumors. The data provide evidence that these n-3 PUFAs are able to inhibit VEGF expression in colon cancer cells and suggest that one possible mechanism involved may be the negative regulation of the COX-2/PGE(2) pathway. Their potential clinical application as anti-angiogenic compounds in colon cancer therapy is proposed.