Role of ω-3 polyunsaturated fatty acids on cyclooxygenase-2 metabolism in brain-metastatic melanoma

Deletion of Elovl5 leads to dyslipidemia and atherosclerosis in LDLR-deficient mice

Atherosclerosis is a chronic inflammatory disease for which hepatic steatosis and atherogenic dyslipidemia are significant risk factors. We investigated the effects of endogenously generated very-long-chain polyunsaturated fatty acids (VL-PUFAs) on dyslipidemia and atherosclerosis development using mice that lack ELOVL5, a PUFA elongase that is required for the synthesis of arachidonic acid, EPA, and DHA from the essential fatty acids linoleic and linolenic acids, and the LDL receptor (LDLR). Elovl5-/-;Ldlr-/- mice manifest increased liver triglyceride and cholesterol concentrations due to the activation of sterol regulatory element binding protein-1, a transcription factor that activates enzymes required for de novo lipogenesis. Plasma levels of triglycerides and cholesterol in VLDL, IDL, and LDL were markedly elevated in Elovl5-/-;Ldlr-/- mice fed a chow and the mice exhibited marked aortic atherosclerotic plaques. Bone marrow-derived monocytes from wild-type (WT) and Elovl5-/- mice were polarized to M1 and M2 macrophages, and the effects of ELOVL5 on inflammatory activity were determined. There were no differences in most of the markers tested for M1 and M2 polarized cells between WT and Elovl5-/- cells, except for a slight increase in PGE2 secretion in Elovl5-/- cells, likely due to elevated Cox-2 expression. These results suggest that the deletion of Elovl5 leads to hepatic steatosis and dyslipidemia, which are the major factors in severe atherosclerosis in Elovl5-/-;Ldlr-/- mice.

The Role of Specialized Pro-Resolving Lipid Mediators in Inflammation-Induced Carcinogenesis

Cancer is a process involving cell mutation, increased proliferation, invasion, and metastasis. Over the years, this condition has represented one of the most concerning health problems worldwide due to its significant morbidity and mortality. At present, the incidence of cancer continues to grow exponentially. Thus, it is imperative to open new avenues in cancer research to understand the molecular changes driving DNA transformation, cell-to-cell interaction derangements, and immune system surveillance decay. In this regard, evidence supports the relationship between chronic inflammation and cancer. In light of this, a group of bioactive lipids derived from polyunsaturated fatty acids (PUFAs) may have a position as novel anti-inflammatory molecules known as the specialized pro-resolving mediators (SPMs), a group of pro-resolutive inflammation agents that could improve the anti-tumor immunity. These molecules have the potential role of chemopreventive and therapeutic agents for various cancer types, and their effects have been documented in the scientific literature. Thus, this review objective centers around understanding the effect of SPMs on carcinogenesis and their potential therapeutic effect.

The Role of Transcription Factor PPAR-γ in the Pathogenesis of Psoriasis, Skin Cells, and Immune Cells

The peroxisome proliferator-activated receptor PPAR-γ is one of three PPAR nuclear receptors that act as ligand-activated transcription factors. In immune cells, the skin, and other organs, PPAR-γ regulates lipid, glucose, and amino acid metabolism. The receptor translates nutritional, pharmacological, and metabolic stimuli into the changes in gene expression. The activation of PPAR-γ promotes cell differentiation, reduces the proliferation rate, and modulates the immune response. In the skin, PPARs also contribute to the functioning of the skin barrier. Since we know that the route from identification to the registration of drugs is long and expensive, PPAR-γ agonists already approved for other diseases may also represent a high interest for psoriasis. In this review, we discuss the role of PPAR-γ in the activation, differentiation, and proliferation of skin and immune cells affected by psoriasis and in contributing to the pathogenesis of the disease. We also evaluate whether the agonists of PPAR-γ may become one of the therapeutic options to suppress the inflammatory response in lesional psoriatic skin and decrease the influence of comorbidities associated with psoriasis.

Diet quality is associated with primary melanoma thickness

Background

Objective

Methods

Results

Conclusions

The Influences of Omega-3 Polyunsaturated Fatty Acids on the Development of Skin Cancers

Dietary nutrition intake is essential for human beings and influences various physiological and pathological actions in the human body. Among various nutritional factors, dietary intake of omega-3 polyunsaturated fatty acids (PUFAs) has been shown to have various beneficial effects against inflammatory diseases. In addition to their therapeutic potency against inflammation, omega-3 PUFAs have also been shown to have anti-tumor effects via various mechanisms, such as cell arrest and apoptosis. To date, limited information is available on these effects in cutaneous malignancies. In this review, we focused on the effect of omega-3 PUFAs on skin cancers, especially malignant melanoma, basal cell carcinoma, lymphoma, and squamous cell carcinoma and discussed the detailed molecular mechanism of the omega-3 PUFA-mediated anti-tumor response. We also explored the molecular mechanisms mediated by epigenetic modifications, cell adhesion molecules, and anti-tumor immune responses.

Anti-inflammatory effects and enhancing immune response of freshwater hybrid catfish oil in RAW264.7 cells

The present study assessed the effect of freshwater hybrid catfish oil (FFO) on the inflammatory status of lipopolysaccharide (LPS)-stimulated RAW264.7 cells and investigated the underlying mechanisms. RAW264.7 cells were supplemented with various concentrations [0.125-2% in 0.5% propylene glycol (v/v)] of FFO with or without LPS (1 µg/ml) for 24 h. Inflammatory cytokines and mediators were quantified using ELISA and reverse transcription-quantitative PCR. The results revealed that FFO treatment inhibited the secretion and mRNA expression of the pro-inflammatory cytokines IL-6, IL-1β, TNF-α. In line with this, FFO suppressed the expression and secretion of the inflammatory mediators cyclooxygenase-2 and prostaglandin E2. FFO also reduced apoptotic body formation and DNA damage. Correspondingly, FFO enhanced the immune response by modulating the cell cycle regulators p53, cyclin D2 and cyclin E2. Accordingly, FFO may be developed as a nutraceutical product to prevent inflammation.

Daily Lifestyle and Cutaneous Malignancies

Daily lifestyle is a fundamental part of human life and its influence accumulates daily in the human body. We observe that a good daily lifestyle has a beneficial impact on our health; however, the actual effects of individual daily lifestyle factors on human skin diseases, especially skin cancers, have not been summarized. In this review, we focused on the influence of daily lifestyle on the development of skin cancer and described the detailed molecular mechanisms of the development or regulation of cutaneous malignancies. Several daily lifestyle factors, such as circadian rhythm disruption, smoking, alcohol, fatty acids, dietary fiber, obesity, and ultraviolet light, are known to be associated with the risk of cutaneous malignancies, malignant melanoma, squamous cell carcinoma, basal cell carcinoma, and Merkel cell carcinoma. Although the influence of some daily lifestyles on the risk of skin cancers is controversial, this review provides us a better understanding of the relationship between daily lifestyle factors and skin cancers.

Importance of the Role of ω-3 and ω-6 Polyunsaturated Fatty Acids in the Progression of Brain Cancer

Brain cancer is one of the most malignant types of cancer in both children and adults. Brain cancer patients tend to have a poor prognosis and a high rate of mortality. Additionally, 20-40% of all other types of cancer can develop brain metastasis. Numerous pieces of evidence suggest that omega-3-polyunsaturated fatty acids (ω-PUFAs) could potentially be used in the prevention and therapy of several types of cancer. PUFAs and oxylipins are fundamental in preserving physiological events in the nervous system; it is, therefore, necessary to maintain a certain ratio of ω-3 to ω-6 for normal nervous system function. Alterations in PUFAs signaling are involved in the development of various pathologies of the nervous system, including cancer. It is well established that an omega-6-polyunsaturated fatty acid (ω-6 PUFA)-rich diet has a pro-tumoral effect, whereas the consumption of an ω-3 rich diet has an anti-tumoral effect. This review aims to offer a better understanding of brain cancer and PUFAs and to discuss the role and impact of PUFAs on the development of different types of brain cancer. Considering the difficulty of antitumor drugs in crossing the blood-brain barrier, the therapeutic role of ω-3/ω-6 PUFAs against brain cancer would be a good alternative to consider. We highlight our current understanding of the role of PUFAs and its metabolites (oxylipins) in different brain tumors, proliferation, apoptosis, invasion, angiogenesis, and immunosuppression by focusing on recent research in vitro and in vivo.

Patterns of Omega-3 and Omega-6 Fatty Acid Dietary Intake and Melanoma Thickness at Diagnosis

BACKGROUND

Experimental evidence suggests that dietary intakes of omega-3 and omega-6 polyunsaturated fatty acids have divergent effects on melanoma growth, but epidemiologic evidence on their combined effect is lacking.

METHODS

In 634 Australian patients with primary melanoma, we assessed prediagnosis consumption of 39 food groups by food frequency questionnaires completed within 2 months of diagnosis. We derived, by reduced rank regression, dietary patterns that explained variability in selected omega-3 and omega-6 fatty acid intakes. Prevalence ratios (PR) and 95% confidence intervals (CI) for the association between tertiles of dietary patterns and melanoma thickness >2 mm versus ≤2 mm were estimated using Poisson regression.

RESULTS

Overall omega-3 fatty acid intakes were low. Two major fatty acid dietary patterns were identified: "meat, fish, and fat," positively correlated with intakes of all fatty acids; and "fish, low-meat, and low-fat," positively correlated with long-chain omega-3 fatty acid intake, and inversely with medium-chain omega-3 and omega-6 fatty acid intakes. Prevalence of thick melanomas was significantly higher in those in the highest compared with lowest tertile of the "meat, fish, and fat" pattern (PR, 1.40; 95% CI, 1.01-1.94), especially those with serious comorbidity (PR, 1.83; 95% CI, 1.15-2.92) or a family history (PR, 2.32; 95% CI, 1.00-5.35). The "fish, low-meat, and low-fat" pattern was not associated with melanoma thickness.

CONCLUSIONS

People with high meat, fish, and fat intakes, who thus consumed relatively high levels of omega-3 and high omega-6 fatty acid intakes, are more likely to be diagnosed with thick than thin melanomas.

IMPACT

High omega-3 and omega-6 fatty acid intakes may contribute to patients' presentation with thick melanomas.

Effect of fatty acids on melanogenesis and tumor cell growth in melanoma cells

Fatty acids have various physiological effects on melanoma. For example, palmitic acid (PA) increases melanin levels; linoleic acid and DHA decrease melanin levels; and DHA suppresses tumor growth. In this study, we focused on the relationship between the structure of fatty acids and their physiological effects in melanoma to examine the likely mechanisms of action. We showed that saturated fatty acids and PUFAs display opposing effects on melanin content in melanoma cells. Likewise, PA and EPA have opposing effects in terms of actin polymerization. Our findings suggest that PA and EPA change melanin content in melanoma to alter melanosome trafficking by modulating actin polymerization. Here, we also examined the mechanism of the anti-tumor effect of DHA. We found that DHA interacts with receptor for activated C kinase 1 and represses melanoma cell proliferation by suppressing protein kinase C signaling. Our results suggest a new mechanism to explain the physiological effects of fatty acids.

An omega-3 polyunsaturated fatty acid derivative, 18-HEPE, protects against CXCR4-associated melanoma metastasis

Melanoma has a high propensity to metastasize and exhibits a poor response to classical therapies. Dysregulation of the chemokine receptor gene CXCR4 is associated with melanoma progression, and although n-3 polyunsaturated fatty acids (PUFAs) are known to be beneficial for melanoma prevention, the underlying mechanism of this effect is unclear. Here, we used the n-3 fatty acid desaturase (Fat-1) transgenic mouse model of endogenous n-3 PUFA synthesis to investigate the influence of elevated n-3 PUFA levels in a mouse model of metastatic melanoma. We found that relative to wild-type (WT) mice, Fat-1 mice exhibited fewer pulmonary metastatic colonies and improved inflammatory indices, including reduced serum tumor necrosis factor alpha (TNF-α) levels and pulmonary myeloperoxidase activity. Differential PUFA metabolites in serum were considered a key factor to alter cancer cell travelling to lung, and we found that n-6 PUFAs such as arachidonic acid induced CXCR4 protein expression although n-3 PUFAs such as eicosapentaenoic acid (EPA) decreased CXCR4 levels. In addition, serum levels of the bioactive EPA metabolite, 18-HEPE, were elevated in Fat-1 mice relative to WT mice, and 18-HEPE suppressed CXCR4 expression in B16-F0 cells. Moreover, relative to controls, numbers of pulmonary metastatic colonies were reduced in WT mice receiving intravenous injections either of 18-HEPE or 18-HEPE-pretreated melanoma cells. Our results indicate that 18-HEPE is a potential anticancer metabolite that mediates, at least in part, the preventive effect of n-3 PUFA on melanoma metastasis.

Omega-3 Polyunsaturated Fatty Acid Derived Lipid Mediators and their Application in Drug Discovery

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) play crucial and often opposing regulatory roles in health and in pathological conditions. n-3 and n-6 PUFA undergo biotransformation to parallel series of lipid mediators that are potent modulators of many cellular processes. A wide range of biological actions have been attributed to lipid mediators derived from n-6 PUFA, and these mediators have served as lead compounds in the development of numerous clinically approved drugs, including latanoprost (Xalatan: Pfizer), which is listed on the WHO Model List of Essential Medicines. n-3 PUFA-derived mediators have received less attention, in part because early studies suggested that n-3 PUFA act simply as competitive substrates for biotransformation enzymes and decrease the formation of n-6 PUFA-derived lipid mediators. However, more recent studies suggest that n-3 PUFA-derived mediators are biologically important in their own right. It is now emerging that many n-3 PUFA-derived lipid mediators have potent and diverse activities that are distinct from their n-6 counterparts. These findings provide new opportunities for drug discovery. Herein, we review the biosynthesis of n-3 PUFA-derived lipid mediators and highlight their biological actions that may be exploited for drug development. Lastly, we provide examples of medicinal chemistry research that has utilized n-3 PUFA-derived lipid mediators as novel lead compounds in drug design.

Analysis of Vascular Cell Response to Hypertension Induced by Pressure Loading and Its Application as a Tool for Exploring Pharmacological Modes of Action

Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression is induced by interleukin-1β (IL-1β) stimulation in vascular smooth muscle cells (VSMCs), resulting in the production of nitric oxide and prostaglandins such as PGI₂. The expression of iNOS and COX-2 in cultured VSMCs isolated from 6-7-week-old stroke-prone spontaneously hypertensive rats (SHRSP) is significantly lower than in cells of normotensive Wistar Kyoto rats (WKY). These reductions are also found in cells exposed to pulsatile atmospheric pressure between 80-160 mmHg at a rate of 4 cycles/min, which simulates systolic hypertension. Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, potentiates IL-1β-induced iNOS and COX-2 expression in VSMCs isolated from WKY, but not those from SHRSP. In response to endothelial injury at a local site, iNOS and COX-2 induction in VSMCs may function primarily as a defensive and compensatory mechanism for endothelial dysfunction by preventing the development of pathological conditions. Thus, in certain pathological conditions associated with hypertension, vascular walls with reduced iNOS and COX-2 expression may aggravate or initiate further vascular injury. In this situation, DHA may contribute to maintaining homeostasis in VSMCs by potentiating iNOS and COX-2 expression. Using cells isolated from a genetic pathological animal model alongside cells exposed to experimental pathological conditions can be an effective tool for the analysis of cell response to hypertension and exploring pharmacological modes of action in vitro.

Role of β-catenin signaling in the anti-invasive effect of the omega-3 fatty acid DHA in human melanoma cells

BACKGROUND

We previously found that docosahexaenoic acid (DHA), a dietary polyunsaturated fatty acid present at high level in fatty fish, inhibited cell growth and induced differentiation of melanoma cells in vitro by increasing nuclear β-catenin content. An anti-neoplastic role of nuclear β-catenin was suggested in melanoma, and related to the presence in the melanocyte lineage of the microphtalmia transcription factor (MITF), which interferes with the transcription of β-catenin/TCF/LEF pro-invasive target genes.

OBJECTIVE

In the present work we investigated if DHA could inhibit the invasive potential of melanoma cells, and if this effect could be related to DHA-induced alterations of the Wnt/β-catenin signaling, including changes in MITF expression.

METHODS

WM115 and WM266-4 human melanoma, and B16-F10 murine melanoma cell lines were used. Cell invasion was evaluated by Wound Healing and Matrigel transwell assays. Protein expression was analyzed by Western Blotting and β-catenin phosphorylation by immunoprecipitation. The role of MITF in the anti-invasive effect of DHA was analyzed by siRNA gene silencing.

RESULTS

We found that DHA inhibited anchorage-independent cell growth, reduced their migration/invasion in vitro and down-regulated several Matrix Metalloproteinases (MMP: MMP-2, MT1-MMP and MMP-13), known to be involved in melanoma invasion. We related these effects to the β-catenin increased nuclear expression and PKA-dependent phosphorylation, as well as to the increased expression of MITF.

CONCLUSION

The data obtained further support the potential role of dietary DHA as suppressor of melanoma progression to invasive malignancy through its ability to enhance MITF expression and PKA-dependent nuclear β-catenin phosphorylation.

Endogenously synthesized n-3 fatty acids in fat-1 transgenic mice prevent melanoma progression by increasing E-cadherin expression and inhibiting β-catenin signaling

Malignant melanoma is the most lethal form of skin cancer. Although preclinical studies have shown that n-3 polyunsaturated fatty acids (PUFAs) are beneficial for prevention of melanoma, the molecular mechanisms underlying the protective effects of n‑3 PUFAs on melanoma remain largely unknown. In the present study, endogenously increased levels of n-3 PUFAs in the tumor tissues of omega‑3 fatty acid desaturase (fat‑1) transgenic mice was associated with a reduction in the growth rate of melanoma xenografts. This reduction in tumor growth in fat‑1 mice compared with wild‑type controls may have been associated, in part, to the: i) Increased expression of E‑cadherin and the reduced expression of its transcriptional repressors, the zinc finger E‑box binding homeobox 1 and snail family transcriptional repressor 1; ii) significant repression of the epidermal growth factor receptor/Akt/β‑catenin signaling pathway; and iii) formation of significant levels of n‑3 PUFA‑derived lipid mediators, particularly resolvin D2 and E1, maresin 1 and 15‑hydroxyeicosapentaenoic acid. In addition, vitamin E administration counteracted n‑3 PUFA‑induced lipid peroxidation and enhanced the antitumor effect of n‑3 PUFAs, which suggests that the protective role of n‑3 PUFAs against melanoma is not mediated by n‑3 PUFAs‑induced lipid peroxidation. These results highlight a potential role of n‑3 PUFAs supplementation for the chemoprevention of melanoma in high‑risk individuals, and as a putative adjuvant agent in the treatment of malignant melanoma.

Omega-3 Fatty Acids and Cancer Cell Cytotoxicity: Implications for Multi-Targeted Cancer Therapy

Cancer is a major disease worldwide. Despite progress in cancer therapy, conventional cytotoxic therapies lead to unsatisfactory long-term survival, mainly related to development of drug resistance by tumor cells and toxicity towards normal cells. n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), can exert anti-neoplastic activity by inducing apoptotic cell death in human cancer cells either alone or in combination with conventional therapies. Indeed, n-3 PUFAs potentially increase the sensitivity of tumor cells to conventional therapies, possibly improving their efficacy especially against cancers resistant to treatment. Moreover, in contrast to traditional therapies, n-3 PUFAs appear to cause selective cytotoxicity towards cancer cells with little or no toxicity on normal cells. This review focuses on studies investigating the cytotoxic activity of n-3 PUFAs against cancer cells via apoptosis, analyzing the molecular mechanisms underlying this effective and selective activity. Here, we highlight the multiple molecules potentially targeted by n-3 PUFAs to trigger cancer cell apoptosis. This analysis can allow a better comprehension of the potential cytotoxic therapeutic role of n-3 PUFAs against cancer, providing specific information and support to design future pre-clinical and clinical studies for a better use of n-3 PUFAs in cancer therapy, mainly combinational therapy.

Diet in dermatology: Part II. Melanoma, chronic urticaria, and psoriasis

The roles of dietary factors in aggravating, preventing, or treating skin diseases are common questions encountered in dermatology practice. Part II of this two-part series reviews dietary modifications that can potentially be utilized in the management of melanoma, chronic urticaria, and psoriasis patients. Specifically, we examine the effect of alcohol consumption and supplementation with vitamins D and E, polyunsaturated fatty acids, selenium, green tea, resveratrol, and lycopene on melanoma risk. The relationships between chronic urticaria symptoms and dietary pseudoallergens, gluten, and vitamin D are analyzed. We explore weight loss, reduced alcohol consumption, and gluten avoidance as means of reducing psoriasis-associated morbidity, as well as the possible utility of supplementation with polyunsaturated fatty acids, folic acid, vitamin D, and antioxidants. With proper knowledge of the role of diet in these cutaneous disease processes, dermatologists can better answer patient inquiries and consider implementation of dietary modifications as adjuncts to other treatments and preventative measures.

ω-3 polyunsaturated fatty acids-derived lipid metabolites on angiogenesis, inflammation and cancer

Epidemiological and pre-clinical studies support the anti-tumor effects of ω-3 PUFAs; however, the results from human trials are mixed, making it difficult to provide dietary guidelines or recommendations of ω-3 PUFAs for disease prevention or treatment. Understanding the molecular mechanisms by which ω-3 PUFAs inhibit cancer could lead to better nutritional paradigms and human trials to clarify their health effects. The ω-3 PUFAs exert their biological activities mainly through the formation of bioactive lipid metabolites. Here we discuss the biology of cyclooxygenase, lipoxygenase and cytochrome P450 enzymes-derived ω-3-series lipid metabolites on angiogenesis, inflammation and cancer.

Pulmonary delivery of docosahexaenoic acid mitigates bleomycin-induced pulmonary fibrosis

BACKGROUND

Pulmonary fibrosis is an untreatable, fatal disease characterized by excess deposition of extracellular matrix and inflammation. Although the etiology of pulmonary fibrosis is unknown, recent studies have implicated dysregulated immune responses and wound healing. Since n-3 polyunsaturated fatty acids (n-3 PUFAs) may beneficially modulate immune responses in a variety of inflammatory disorders, we investigated the therapeutic role of docosahexaenoic acid (DHA), a single n-3 PUFA, in lung fibrosis.

METHODS

Intratracheal DHA or PBS was administered to mouse lungs 4 days prior to intratracheal bleomycin treatment. Body weight and survival were monitored for 21 days. Bronchoalveolar fluid (BALF) and lung inflammatory cells, cytokines, eicosanoids, histology and lung function were determined on serial days (0, 3, 7, 14, 21) after bleomycin injury.

RESULTS

Intratracheal administration of DHA mitigated bleomycin-induced lung injury. Mice pretreated with DHA had significantly less weight loss and mortality after bleomycin injury. The lungs from DHA-pretreated mice had markedly less fibrosis. DHA pretreatment also protected the mice from the functional changes associated with bleomycin injury. Bleomycin-induced cellular inflammation in BALF and lung tissue was blunted by DHA pretreatment. These advantageous effects of DHA pretreatment were associated with decreased IL-6, LTB4, PGE2 and increased IL-10.

CONCLUSIONS

Our findings demonstrate that intratracheal administration of DHA, a single PUFA, protected mice from the development of bleomycin-induced pulmonary inflammation and fibrosis. These results suggest that further investigations regarding the role of n-3 polyunsaturated fatty acids in fibrotic lung injury and repair are needed.

Potential of long-chain n-3 polyunsaturated fatty acids in melanoma prevention

The possible antineoplastic activity of dietary long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) has been supported by ample preclinical studies that have identified a number of molecular factors and pathways affected by these fatty acids and involved in cell growth, apoptosis, invasion, and angiogenesis. The aim of this critical review is to assess the current state of knowledge on the potential anticancer effects of LC n-3 PUFAs against malignant melanoma, one of the most common cancers among Western populations. The results of preclinical as well as human observational and interventional studies investigating the effects of LC n-3 PUFAs in melanoma were examined. Overall, the analysis of the literature reveals that, even though a large body of information is available, further effort is needed to identify the main molecular targets of LC n-3 PUFAs in melanoma. Moreover, additional well-designed human observational studies are essential to shed further light on the issue. The results of these studies could provide support and specific information for the development of clinical studies, especially those performed in combination with conventional or innovative antineoplastic therapies.

Prostaglandin E3 metabolism and cancer

The anticancer activity of n-3 fatty acids, especially those derived from fish, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid) (DHA), has been studied for centuries. While there is a growing body of evidence that EPA and DHA may influence cancer initiation and development through targeting multiple events of tumor development, the underlying mechanisms responsible for these activities are still not fully understood. A number of studies have suggested that the anticancer activities of EPA and DHA are associated with their effects on eicosanoid metabolism by which they inhibit prostaglandin E2 (PGE2) production. In contrast to DHA, EPA can function as a substrate for cyclooxygenases (COXs) to synthesize unique 3-series prostaglandin compounds, especially PGE3. With advance technology in mass spectrometry, there is renewed interest in studying the role of PGE3 in EPA elicited anti-proliferative activity in various cancers, with some promising results. Here, we summarize the regulation of PGE3 synthesis in cancer cells and its role in EPA elicited anticancer activity. The development of PGE3 and its metabolites as potential biomarkers for future clinical evaluation of EPA and fish oil in cancer care is discussed.

Docosahexaenoic acid, G protein-coupled receptors, and melanoma: is G protein-coupled receptor 40 a potential therapeutic target?

BACKGROUND

To determine the effect of docosahexaenoic acid (DHA) on the growth of human melanoma in vitro and in vivo and to better understand the potential role of the G protein-coupled receptors (GPRs) in mediating this effect.

MATERIALS AND METHODS

For in vitro studies, human melanoma and control fibroblast cells were treated with DHA and TAK-875 (selective GPR40 agonist) and a cell viability assay was performed to determine cell counts. A murine subcutaneous xenograft model of human melanoma was used to test the effect of dietary treatment with an omega-3 fatty acid (FA) rich diet compared with an omega-6 FA rich diet on the growth of human melanoma in vivo. A similar animal model was used to test the effect of oral TAK-875 on the growth of established melanoma tumors in vivo.

RESULTS

DHA has an inhibitory effect on the growth of human melanoma both in vitro and in vivo. Tumors from animals on the omega-3 FA rich diet were 69% smaller in weight (P = 0.005) and 76% smaller in volume compared with tumors from animals on the omega-6 FA rich diet. TAK-875 has an inhibitory effect on the growth of human melanoma both in vitro and in vivo. Tumors from animals treated with TAK-875 were 46% smaller in weight (P = 0.07), 62% smaller in volume (P = 0.03), and grew 77% slower (P = 0.04) compared with the placebo group.

CONCLUSIONS

DHA and TAK-875 have a profound and selective inhibitory effect on the growth of human melanoma both in vitro and in vivo.

Flaxseed enriched diet-mediated reduction in ovarian cancer severity is correlated to the reduction of prostaglandin E(2) in laying hen ovaries

Prevention of ovarian cancer is the best approach for reducing the impact of this deadly disease. The laying hen is a robust model of spontaneous ovarian cancer that recapitulates the human disease. Dietary intervention with flaxseed, the richest vegetable source of omega-3 fatty acids (OM-3FAs) and phytoestrogen lignans, demonstrate the potential for effective prevention and amelioration of ovarian cancer by targeting inflammatory prostaglandin pathways. Prostaglandin E2 (PGE2) is the most pro-inflammatory ecoisanoid and one of the downstream products of two isoforms of cyclooxygenase (COX) enzymes: COX-1 and COX-2. Our objective was to investigate the effect of flaxseed supplementation for one year on ovarian cancer and correlate its effects to expression of COX enzymes and concentrations of prostaglandins. White Leghorn hens were fed 10% flaxseed-enriched or standard diet for one year. The severity of ovarian cancer was determined by gross pathology and histology. COX-1 and COX-2 localization and protein and mRNA expression and PGE2 and PGE3 concentrations in ovaries were measured by IHC, western blot, quantitative real-time PCR and LC-MS-MS, respectively. The results demonstrated a significant reduction in late stage ovarian tumors in the flaxseed-fed hens compared with the control diet-fed hens. In correlation with decreased ovarian cancer severity, concentrations of PGE2 and expression of COX-2 were diminished in ovaries of flaxseed-fed hens. PGE3 concentrations were below the level of detection. The results demonstrated that in normal ovaries, COX-1 was localized to the granulosa cell layer surrounding the follicles and ovarian surface epithelium (OSE) whereas COX-2 protein was localized to the granulosa cell layer in the follicle. Extensive COX-1 and COX-2 protein expression was found throughout the ovarian carcinoma. Our findings suggest that the flaxseed-mediated reduction in the severity of ovarian cancer in hens is correlated to the reduction in PGE2 in the ovaries of flaxseed-fed hens. These findings may provide the basis for clinical trials of dietary intervention targeting prostaglandin biosynthesis for the prevention and treatment of ovarian cancer.

Interaction of brain fatty acid-binding protein with the polyunsaturated fatty acid environment as a potential determinant of poor prognosis in malignant glioma

Malignant gliomas are the most common adult brain cancers. In spite of aggressive treatment, recurrence occurs in the great majority of patients and is invariably fatal. Polyunsaturated fatty acids are abundant in brain, particularly ω-6 arachidonic acid (AA) and ω-3 docosahexaenoic acid (DHA). Although the levels of ω-6 and ω-3 polyunsaturated fatty acids are tightly regulated in brain, the ω-6:ω-3 ratio is dramatically increased in malignant glioma, suggesting deregulation of fundamental lipid homeostasis in brain tumor tissue. The migratory properties of malignant glioma cells can be modified by altering the ratio of AA:DHA in growth medium, with increased migration observed in AA-rich medium. This fatty acid-dependent effect on cell migration is dependent on expression of the brain fatty acid binding protein (FABP7) previously shown to bind DHA and AA. Increased levels of enzymes involved in eicosanoid production in FABP7-positive malignant glioma cells suggest that FABP7 is an important modulator of AA metabolism. We provide evidence that increased production of eicosanoids in FABP7-positive malignant glioma growing in an AA-rich environment contributes to tumor infiltration in the brain. We discuss pathways and molecules that may underlie FABP7/AA-mediated promotion of cell migration and FABP7/DHA-mediated inhibition of cell migration in malignant glioma.

Dietary ω -3 polyunsaturated fatty acid DHA: a potential adjuvant in the treatment of cancer

ω-3 Polyunsaturated fatty acids (PUFAs), mainly present in fish oil, are part of the human diet. Among PUFAs, docosahexaenoic acid (DHA) has received particular attention for its anti-inflammatory, antiproliferative, proapoptotic, antiangiogenetic, anti-invasion, and antimetastatic properties. These data suggest that DHA can exert antitumor activity potentially representing an effective adjuvant in cancer chemotherapy. This review is focused on current knowledge supporting the potential use of DHA for the enhancement of the efficacy of anticancer treatments in relation to its ability to enhance the uptake of anticancer drugs, regulate the oxidative status of tumor cells, and inhibit tumor cell invasion and metastasis.

Identification of oligomer proanthocyanidins (F2) isolated from grape seeds as a formyl peptide receptor 1 partial agonist

Formyl peptide receptor 1 (FPR1) plays an important role in the rapid progression of glioblastoma and has been considered as a molecular target for the treatment. Previously, we have shown that oligomer proanthocyanidins (F2, degree of polymerization 2-15), isolated from grape seeds, inhibited FPR1-mediated chemotaxis of U-87 glioblastoma cells. In the present study, we investigated the capacity of F2 to interact with FPR1. The cross attenuation of chemotaxis revealed that F2 shared FPR1 with formyl-methionyl-leucyl-phenylalanine (fMLF), which is a prototype agonist of FPR1. F2 was chemotactic for U-87 cells, and the chemotactic response was abolished when FPR1 gene was silenced or FPR1 was competitively occupied. We further show that F2 specifically blocked the binding of fluorescent agonist to FPR1. Interestingly, F2 exhibited the characteristic of a partial agonist for FPR1, as shown by its capacity to activate FPR1-mediated PI3K-PKC-MAPK pathways. Meanwhile, F2 also attenuated fMLF-triggered MAPK activation, suggesting that F2 could antagonize the effect of an agonist. Furthermore, F2 abolished the invasion of U-87 cells induced by fMLF. Thus, we have identified F2 as a novel, partial agonist for FPR1, which may be useful for glioblastoma therapy.

Anticancer activity of fish oils against human lung cancer is associated with changes in formation of PGE2 and PGE3 and alteration of Akt phosphorylation

The beneficial effects of omega-3 fatty acids are believed to be due in part to selective alteration of arachidonate metabolism that involves cyclooxygenase (COX) enzymes. Here we investigated the effect of eicosapentaenoic acid (EPA) on the proliferation of human non-small cell lung cancer A549 (COX-2 over-expressing) and H1299 (COX-2 null) cells as well as their xenograft models. While EPA inhibited 50% of proliferation of A549 cells at 6.05 µM, almost 80 µM of EPA was needed to reach similar levels of inhibition of H1299 cells. The formation of prostaglandin (PG)E3 in A549 cells was almost threefold higher than that of H1299 cells when these cells were treated with EPA (25 µM). Intriguingly, when COX-2 expression was reduced by siRNA or shRNA in A549 cells, the antiproliferative activity of EPA was reduced substantially compared to that of control siRNA or shRNA transfected A549 cells. In line with this, dietary menhaden oil significantly inhibited the growth of A549 tumors by reducing tumor weight by 58.8 ± 7.4%. In contrast, a similar diet did not suppress the development of H1299 xenograft. Interestingly, the ratio of PGE3 to PGE2 in A549 was about 0.16 versus only 0.06 in H1299 xenograft tissues. Furthermore, PGE2 up-regulated expression of pAkt, whereas PGE3 downregulated expression of pAkt in A549 cells. Taken together, the results of our study suggest that the ability of EPA to generate PGE3 through the COX-2 enzyme might be critical for EPA-mediated tumor growth inhibition which is at least partly due to down-regulation of Akt phosphorylation by PGE3.

Tackling the aging process with bio-molecules: a possible role for caloric restriction, food-derived nutrients, vitamins, amino acids, peptides, and minerals

Aging is a multifactorial process leading to general deterioration in many tissues and organs, accompanied by an increased incidence and severity of a wide variety of chronic, incurable, and often fatal diseases. A possibility of slowing down the aging process and improving the quality of life in old age by nutritional intervention has renewed the interest of the scientific world in anti-aging therapies. These include potential dietary interventions, adherence to nutrition, hormonal and cell-based therapies, genetic manipulations, and anti-aging supplements or nutrients. This review addresses strategies to slow the aging process by caloric restriction and the use of nutritional supplements.

Omega-3 but not omega-6 unsaturated fatty acids inhibit the cancer-specific ENOX2 of the HeLa cell surface with no effect on the constitutive ENOX1

Epidemiological and laboratory studies suggest that dietary fatty acids (oleic acid (in olive oil), eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) (in fish oil)) play important roles in carcinogenesis. The most potent antitumor effects of all fatty acids are given by fatty acid conjugated linoleic acid (CLA). The antitumor effects of CLA may be mediated through enhanced apoptosis. While CLA, EPA, and DHA (omega-3 polyunsaturated fatty acids) have inhibitory effects on cancer cells, omega-6 fatty acids have often shown negative or potentiating effects on cancer cells. Linoleic acid (an omega-6) is desaturated in the cell by delta 6 and 5 destaturases to form arachidonic acid. COX 1 and 2 isoforms then act on arachidonic acid to form prostaglandins and other related regulatory molecules. It is normally thought that what is important to the development of the cancerous phenotype is some balance of these various metabolites. In experiments with surface NOX proteins released from HeLa cells, spectrophotometric measurements of the oxidation of NADH revealed inhibition of the cancer-specific ENOX2 activity by CLA and the omega-3 fatty acids, eicosapentaenoic, docosahexaenoic, and α-linolenic acids. The constitutive ENOX1 activity was not inhibited. In contrast, the omega-6 fatty acids, linoleic acid, and arachidonic acid inhibited neither ENOX1 nor ENOX2. The findings indicate the possibility that a direct effect of CLA and omega-3 fatty acids on ENOX2 may be responsible for the potent activity of CLA and omega-3 fatty acids in cancer prevention and therapy.

Peroxisome proliferator-activated receptors (PPARs) in dermatology: Challenge and promise

Since their discovery it has become clear that peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors involved in the genetic regulation of the lipid metabolism and energy homoeostasis. Subsequently, accumulating evidence suggests a role of PPARs in genomic pathways including the regulation of cell growth, apoptosis and differentiation. These findings indicate that PPARs and PPAR agonists play an important role in inflammatory responses and tumor promotion. Because of their diverse biologic activities on keratinocytes and other skin cells, PPARs represent a major research target for the understanding and treatment of many skin pathologies, such as hyperproliferative and inflammatory diseases. Overmore recent clinical trials identified PPARs as promising drug targets for the prevention and treatment of various diseases in the field of dermatology. The present review summarizes the current knowledge of PPAR functions in various skin disorders particularly those involving inflammation and epidermal hyperproliferation (i.e., psoriasis, atopic dermatitis, acne, scleroderma, skin malignancies).

Docosahexaenoic acid inhibits invasion of human RT112 urinary bladder and PT45 pancreatic carcinoma cells via down-modulation of granzyme B expression

Fish oil-derived n-3 polyunsaturated fatty acids (n-3 PUFAs) inhibit invasion of some tumor cell types in vitro and in vivo. The mechanisms underlying this activity are unclear. Here, we examined the capability of n-3 PUFA-docosahexaenoic acid (22:6n-3; DHA) to affect the invasiveness of human RT112 urinary bladder and PT45 pancreatic carcinoma cell lines in vitro and the mechanism underlying this activity; n-6 PUFA-arachidonic acid (20:4n-6; AA) served as control. We showed that, in contrast to AA, 25, 50 and 100 μM DHA significantly inhibited in a dose-dependent manner the invasion through Matrigel of both RT112 and PT45 cells. Then, we analyzed whether the serine proteinase granzyme B (GrB), originally known as cytotoxic molecule of lymphocytes and recently also characterized for its extracellular functions such as invasion promotion of bladder cancer cells, might be involved in the invasion inhibitory activity exerted by DHA. We demonstrated that, accordingly to RT112 bladder cancer cells, PT45 cells expressed GrB and GrB promoted their invasion, since stealth RNA interference-mediated down-regulation of GrB dramatically suppressed PT45 cell invasion. Notably, we also showed that, in contrast to AA, 25, 50 and 100 μM DHA induced a dose-dependent down-modulation of GrB expression in both RT112 and PT45 cells. In conclusion, DHA can reduce the invasive phenotype of bladder and pancreatic carcinoma cells, and we provide the first evidence for a possible causative role of GrB in DHA-induced inhibition of cancer cell invasion. The potential use of fish oil as adjuvant antibladder and antipancreatic cancer agent may be suggested.

Effect of eicosapentaenoic acid on E-type prostaglandin synthesis and EP4 receptor signaling in human colorectal cancer cells

The omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA), in the free fatty acid (FFA) form, has been demonstrated to reduce adenoma number and size in patients with familial adenomatous polyposis. However, the mechanistic basis of the antineoplastic activity of EPA in the colorectum remains unclear. We tested the hypothesis that EPA-FFA negatively modulates synthesis of and signaling by prostaglandin (PG) E(2) in human colorectal cancer (CRC) cells. EPA-FFA induced apoptosis of cyclooxygenase (COX)-2-positive human HCA-7 CRC cells in vitro. EPA-FFA in cell culture medium was incorporated rapidly into phospholipid membranes of HCA-7 human CRC cells and acted as a substrate for COX-2, leading to reduced synthesis of PGE(2) and generation of PGE(3). Alone, PGE(3) bound and activated the PGE(2) EP4 receptor but with reduced affinity and efficacy compared with its "natural" ligand PGE(2). However, in the presence of PGE(2), PGE(3) acted as an antagonist of EP4 receptor-dependent 3',5' cyclic adenosine monophosphate induction in naturally EP4 receptor-positive LoVo human CRC cells and of resistance to apoptosis in HT-29-EP4 human CRC cells overexpressing the EP4 receptor. We conclude that EPA-FFA drives a COX-2-dependent "PGE(2)-to-PGE(3) switch" in human CRC cells and that PGE(3) acts as a partial agonist at the PGE(2) EP4 receptor.

Cox-2 expression, PGE(2) and cytokines production are inhibited by endogenously synthesized n-3 PUFAs in inflamed colon of fat-1 mice

There is great interest in the role of polyunsaturated fatty acids (PUFAs) in promoting (n-6 class) or inhibiting (n-3 class) inflammation. Mammalian cells are devoid of desaturase that converts n-6 to n-3 PUFAs. Consequently, essential n-3 fatty acids must be supplied with the diet. We have studied the effect of endogenously produced n-3 PUFAs on colitis development in fat-1 transgenic mice carrying the Caenorhabditis elegans fat-1 gene encoding n-3 desaturase. Colonic cell lipid profile was measured by capillary gas chromatography in fat-1 and wild-type (WT) littermates fed standard diet supplemented with 10% (w/w) safflower oil rich (76%) in n-6 polyunsaturated linoleic acid (LA). Experimental colitis was induced by administrating 3% dextran sodium sulphate (DSS). Colitis was scored by histopatological analysis. Cyclooxygenase-2 (Cox-2) expression was evaluated by real time polymerase chain reaction. Prostaglandin E(2) (PGE(2)) levels and cytokine production were determined by enzyme and microsphere-based immunoassays, respectively. The n-6/n-3 PUFA ratios in colonic cells of fat-1 mice were markedly lower (9.83±2.62) compared to WT (54.5±9.24, P<.001). Results also showed an attenuation of colonic acute and chronic inflammation in fat-1 mice with significant decreases in PGE(2) production (P<.01) and Cox-2 expression (P<.01). High levels of colitis-induced proinflammatory cytokines, interleukin (IL)-18, IL-1α, IL-1β, IL-6, monocytes chemotactic proteins 1, 2 and 3 (MCP 1,2,3), matrix metalloproteinase 9 and tumor necrosis factor α (TNF-α) were down-regulated in DSS acutely and chronically treated fat-1 mice. The expression of fat-1 gene in the colon was associated with endogenous n-3 PUFAs production, decreased Cox-2 expression, increased PGE(2) and cytokine production.

Angiogenesis as a potential target of pharmaconutrients in cancer therapy

PURPOSE OF REVIEW

The aim of this review is to provide insight into tumor angiogenesis inhibition by pharmaconutrients through description of the most relevant and recent findings in cancer research.

RECENT FINDINGS

Cancer growth needs oxygen and nutrients supplied through blood vessels to the tumor site. New vessel formation named angiogenesis can be prevented to avoid cancer invasion. Epidemiological studies suggested that specific food intakes could decrease incidence of many cancers. Recently, scientists were interested in the potential antitumor effects of nutrients because of their safety and general acceptance. Many excellent publications demonstrated that a large class of natural compounds including pharmaconutrients exhibits antitumoral activities in selected cancer types. This review focuses on the antiangiogenic role of natural products in cancer treatment, used alone or in combination with conventional chemotherapy.

SUMMARY

There is strong evidence that natural diets influence cancer development by modulating signaling pathways. Our goal is to highlight the specific impact of specific nutrients in the modulation of vascular network leading to tumor angiogenesis inhibition.

beta-oxidation modulates metabolic competition between eicosapentaenoic acid and arachidonic acid regulating prostaglandin E(2) synthesis in rat hepatocytes-Kupffer cells

The ability of n-3 PUFA to competitively inhibit the use of arachidonic acid (AA) for membrane phospholipid synthesis and prostaglandin E(2) (PGE(2)) production has been well demonstrated in single cell models. In the present study, we investigated the metabolic competition between AA and eicosapentaenoic acid (EPA) for PGE(2) synthesis in a rat hepatocyte-Kupffer cell (HPC/KC) co-culture system when the cellular oxidation capacity was enhanced by exogenous l-carnitine. We demonstrate that in the absence of l-carnitine, 1) beta-oxidation rates of EPA and AA were comparable in HPCs and in KCs; 2) AA and not EPA was preferentially incorporated into glycerolipids; and 3) addition of EPA significantly decreased AA-dependent PGE(2) synthesis in HPCs and cyclooxygenase-2 (COX-2) expression in co-cultured HPCs/KCs. However, enhancing the cellular oxidation capacity by the addition of l-carnitine 1) significantly increased beta-oxidation of EPA in HPCs, but only marginally elevated the oxidation of AA in HPCs and the oxidation of both fatty acids in KCs; 2) decreased the esterification, but did not alter the preferential incorporation of AA into glycerolipids; and 3) alleviated the significant competitive inhibition of AA-dependent PGE(2) synthesis and COX-2 expression by EPA. Taken together, the results strongly suggest that l-carnitine affects competition between AA and EPA in PG synthesis in liver cells by enhancing oxidation of EPA in HPCs. This implies that the beneficial effects of n-3 PUFA, especially EPA, are affected by the cellular oxidation capacity.

Dietary docosahexaenoic acid supplementation modulates hippocampal development in the Pemt-/- mouse

The development of fetal brain is influenced by nutrients such as docosahexaenoic acid (DHA, 22:6) and choline. Phosphatidylethanolamine-N-methyltransferase (PEMT) catalyzes the biosynthesis of phosphatidylcholine from phosphatidylethanolamine enriched in DHA and many humans have functional genetic polymorphisms in the PEMT gene. Previously, it was reported that Pemt(-/-) mice have altered hippocampal development. The present study explores whether abnormal phosphatidylcholine biosynthesis causes altered incorporation of DHA into membranes, thereby influencing brain development, and determines whether supplemental dietary DHA can reverse some of these changes. Pregnant C57BL/6 wild type (WT) and Pemt(-/-) mice were fed a control diet, or a diet supplemented with 3 g/kg of DHA, from gestational day 11 to 17. Brains from embryonic day 17 fetuses derived from Pemt(-/-) dams fed the control diet had 25-50% less phospholipid-DHA as compared with WT (p < 0.05). Also, they had 60% more neural progenitor cell proliferation (p < 0.05), 60% more neuronal apoptosis (p < 0.01), and 30% less calretinin expression (p < 0.05; a marker of neuronal differentiation) in the hippocampus compared with WT. The DHA-supplemented diet increased fetal brain Pemt(-/-) phospholipid-DHA to WT levels, and abrogated the neural progenitor cell proliferation and apoptosis differences. Although this diet did not change proliferation in the WT group, it halved the rate of apoptosis (p < 0.05). In both genotypes, the DHA-supplemented diet increased calretinin expression 2-fold (p < 0.05). These results suggest that the changes in hippocampal development in the Pemt(-/-) mouse could be mediated by altered DHA incorporation into membrane phospholipids, and that maternal dietary DHA can influence fetal brain development.

Long-term moderate intervention with n-3 long-chain PUFA-supplemented dairy products: effects on pathophysiological biomarkers in patients with rheumatoid arthritis

n-3 long-chain PUFA (n-3 LC-PUFA) may improve cardiovascular and inflammatory diseases. The effects of n-3 LC-PUFA-supplemented dairy products on inflammation and immunological parameters, biomarkers of oxidative stress, serum lipids, and on disease activity were determined in patients with rheumatoid arthritis (RA). Forty-five subjects (forty-three females and two males) were randomly divided into two groups in a double-blind, placebo-controlled cross-over study. Both groups received placebo or verum products consecutively for 3 months with a 2-month washout phase between the two periods. Blood samples were taken at the beginning and at the end of each period. The dairy products generally improved serum lipids by increasing HDL and lowering lipoprotein a. The n-3 LC-PUFA supplements act to lower TAG. Additionally, a decreased lipopolysaccharide-stimulated cylo-oxygenase-2 expression was found in patients who had consumed the enriched dairy products. The majority of the CD analysed were not influenced, although n-3 LC-PUFA did suppress the immune response as lymphocytes and monocytes were found to be significantly decreased. The n-3 LC-PUFA did not increase the biomarkers of oxidative stress such as 8-iso-PGF(2alpha) and 15-keto-dihydro PGF(2alpha), and DNA damage like 7,8-dihydro-8-oxo-2'-deoxyguanosine. The long-term consumption of dairy products (2 x 12 weeks) diminished the excretion of hydroxypyridinium crosslinks, and favoured the diastolic blood pressure. The consumption of moderate doses of n-3 LC-PUFA in combination with dairy products did not improve the disease activity. However, there is evidence of cardioprotective effects. Furthermore, the long-term consumption of dairy products acts against the cartilage and bone destruction in RA.

Inhibition of arachidonic acid metabolism and its implication on cell proliferation and tumour-angiogenesis

Arachidonic acid (AA) and its metabolites have recently generated a heightened interest due to growing evidence of their significant role in cancer biology. Thus, inhibitors of the AA cascade, first and foremost COX inhibitors, which have originally been of interest in the treatment of inflammatory conditions and certain types of cardiovascular disease, are now attracting attention as an arsenal against cancer. An increasing number of investigations support their role in cancer chemoprevention, although the precise molecular mechanisms that link levels of AA, and its metabolites, with cancer progression have still to be elucidated. This article provides an overview of the AA cascade and focuses on the roles of its inhibitors and their implication in cancer treatment. In particular, emphasis is placed on the inhibition of cell proliferation and neo-angiogenesis through inhibition of the enzymes COX-2, 5-LOX and CYP450. Downstream effects of inhibition of AA metabolites are analysed and the molecular mechanisms of action of a selected number of inhibitors of catalytic pathways reviewed. Lastly, the benefits of dietary omega-3 fatty acids and their mechanisms of action leading to reduced cancer risk and impeded cancer cell growth are mentioned. Finally, a proposal is put forward, suggesting a novel and integrated approach in viewing the molecular mechanisms and complex interactions responsible for the involvement of AA metabolites in carcinogenesis and the protective effects of omega-3 fatty acids in inflammation and tumour prevention.

Neuroprotective activity of omega-3 fatty acids against epilepsy-induced hippocampal damage: Quantification with immunohistochemical for calcium-binding proteins

To investigate whether n-3 polyunsaturated fatty acids (n-3 PUFAs) would promote different morphological changes in the hippocampal formation of rats with epilepsy, we performed an immunocytochemical study using parvalbumin (PV) and calretinin (CR) distribution as a marker. Animals subjected to the experimental model of epilepsy with a single dose of pilocarpine were randomly divided into the following groups: animals with epilepsy treated daily with vehicle (EV) and animals with epilepsy treated daily with 85 mg/kg n-3 PUFAs (EW). Control animals administered saline were also randomly divided into two other groups: animals treated daily with vehicle (CV) and animals treated daily with 85 mg/kg n-3 PUFAs (CW). A larger number of PV-positive neurons were observed in EW when compared with EV, CV, and CW. Similarly, there were significantly more CR-positive neurons in EW than in EV. These findings demonstrate that omega-3 fatty acids prevent status epilepticus-associated neuropathological changes in the hippocampal formation of rats with epilepsy.

Effects of a fish oil-based emulsion on rat hepatoma cell invasion in culture

OBJECTIVE

Total parenteral nutrition containing a lipid emulsion is often employed after surgical tumor resection. This study investigated the effects of a fish oil-based infusion on rat hepatoma cell invasion.

METHODS

Rat ascites hepatoma cell line AH109A was precultured with a fish oil-based or safflower oil-based emulsion for 48 h. Changes in membranous fatty acid composition were evaluated by gas chromatography. The invasiveness of hepatoma cells was assessed by coculturing with mesentery-derived mesothelial cells. To examine ex vivo effects of the fish oil-based infusion on hepatoma invasion, sera were prepared from rats infused with fish oil- or safflower oil-based emulsion and the effects of these sera were assessed. To clarify the mechanism of inhibition of invasion by the fish oil-based emulsion, the effects of prostaglandin (PG) E(2) and PGE(3) on invasion were examined.

RESULTS

Pretreatment with the fish oil-based emulsion reduced invasiveness without affecting growth compared with the safflower oil-based emulsion. Pretreatment with the sera from rats infused with the fish oil-based emulsion also reduced invasiveness compared with the sera from rats infused with the safflower oil-based emulsion. The addition of PGE(2) eliminated the inhibitory effect of the fish oil-based emulsion, and the addition of PGE(3) reduced the invasiveness of hepatoma cells pretreated with the safflower oil-based emulsion.

CONCLUSION

These results suggest that the fish oil-based emulsion may have anti-invasive effects. Changes in the membranous fatty acid composition and consequent changes in the prostaglandins produced may be involved in this inhibitory effect.