15-Lipoxygenase-1-mediated metabolism of docosahexaenoic acid is required for syndecan-1 signaling and apoptosis in prostate cancer cells

Evaluation of several farnesyloxycarbostyril derivatives as potential 15-LOX-1 inhibitors for prostate cancer treatment

The impact of 15-lipoxygenase-1 (15-LOX-1) in the progression of prostate cancer (PCa) is noteworthy, as it correlates with the Gleason score of the disease. Thus, development of specific 15-LOX-1 inhibitors would be desirable for targeted therapy of PCa. This study focused on evaluating the anti-prostate cancer potency of three farnesyloxycarbostyril derivatives, 6-, 7- and 8-farnesyloxycarbostyril (6-, 7- and 8-FQ), as potential inhibitors of 15-LOX-1 on PCa cells. To this end, the enzymatic activity of 15-LOX was first assessed in PCa and human dermal fibroblast (HDF) cells. Subsequently, the cytotoxic effects and apoptosis-inducing capabilities of the compounds were assessed through MTT assay and FITC-annexin V/PI staining, respectively. Among the compounds, 8-FQ was selected for further assessment in a mouse model bearing xenograft human PCa tumor. The results demonstrated that the most effective compound, 8-FQ, caused an 84-fold and 15.7-fold reduction in 15-LOX activity in PC-3 cells at 30 and 14 μM concentrations, respectively. The MTT assay revealed a dose- and time-dependent toxicity of the compounds on PCa cells, and flow cytometry results indicated that apoptosis served as the dominant mechanism of cell death. Given the upregulation of 15-LOX-1 in human PCa cells, the study concludes that the heightened sensitivity to 8-FQ is likely associated with elevated levels of 15-LOX-1. In vivo experiments using immunosuppressed C57BL/6 mice bearing human PC-3 tumors revealed that 8-FQ, at a dosage of 10 mg/kg, exhibited strong antitumor effects with minimal side effects, indicating its potential as a promising therapeutic agent for PCa following further optimization.

Research progress on the role of lipoxygenase and its inhibitors in prostate cancer

Prostate cancer (PCa) has become a common disease among middle-aged and elderly men. The lipoxygenase (LOX) pathway plays a crucial role in the occurrence, development, invasion and metastasis of PCa and is therefore considered a new target for the prevention and treatment of PCa. 5-LOX and 12-LOX have a promoting effect on the occurrence, development, invasion and metastasis of PCa. 15-LOX-2 has an inhibitory effect on PCa. LOX inhibitors can effectively inhibit the metabolic activity of LOX. The research aims to review the mechanism of action and inhibitors of LOX in PCa, in order to provide relevant references for the prevention and treatment of PCa.

Colorectal ALOX15 as a host factor determinant of EPA and DHA effects on colorectal carcinogenesis

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), omega-3 polyunsaturated fatty acids (ω-3 PUFAs) derived from fish oil, are widely used as dietary supplements and FDA-approved treatments for hypertriglyceridemia. However, studies investigating the effects of EPA and DHA on colorectal carcinogenesis (CRC) have yielded conflicting results. The factors that determine these discrepant results remain unknown. Resolvins, oxidative metabolites of EPA and DHA, inhibit key pro-tumorigenic cytokine and chemokine signaling of colorectal cancer (e.g., IL-6, IL-1β, and CCL2). 15-lipoxygenase-1 (ALOX15), a critical enzyme for resolvin generation is commonly lost during human CRC. Whether ALOX15 expression, as a host factor, modulates the effects of EPA and DHA on CRC remains unknown. Therefore, we evaluated the effects of ALOX15 transgenic expression in colonic epithelial cells on resolvin generation by EPA and DHA and CRC in mouse models representative of human CRC. Our results revealed that 1) EPA and DHA effects on CRC were diverse, ranging from suppressive to promotive, and these effects were occasionally altered by the formulations of EPA and DHA (free fatty acid, ethyl ester, triglyceride); 2) EPA and DHA uniformly suppressed CRC in the presence of intestinal ALOX15 transgenic expression, which induced the production of resolvins, decreased colonic CCL3-5 and CXCL-5 expression and tumor associated macrophages while increasing CD8 T cell abundance in tumor microenvironment; and 3) RvD5, the predominant resolvin produced by ALOX15, inhibited macrophage generation of pro-tumorigenic cytokines. These findings demonstrate the significance of intestinal ALOX15 expression as a host factor in determining the effects of EPA and DHA on CRC.

Significance

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are widely used as dietary supplements and FDA-approved treatments for hypertriglyceridemia. Studies of EPA and DHA effects on colorectal carcinogenesis (CRC) have revealed inconsistencies; factors determining the direction of their impact on CRC have remained unidentified. Our data show that EPA and DHA effects on CRC were divergent and occasionally influenced by their formulations. More importantly, intestinal 15-lipoxgenase-1 (ALOX15) expression modulated EPA and DHA effects on CRC, leading to their consistent suppression of CRC. ALOX15 promoted EPA and DHA oxidative metabolism to generate resolvins, which inhibited key pro-tumorigenic inflammatory cytokines and chemokines, including IL-6. IL-1β, and CCL2. ALOX15 is therefore an important host factor in determining EPA and DHA effects on CRC.

Baicalein and luteolin inhibit ischemia/reperfusion-induced ferroptosis in rat cardiomyocytes

BACKGROUND

Ischemia/reperfusion (I/R) is associated with severe cellular damage and death. Ferroptosis, a new form of regulated cell death caused by the accumulation of iron-mediated lipid peroxidation, has been found in several diseases including I/R injury, which was reported to be suppressed by flavonoids. Baicalein (BAI) and luteolin (Lut) are flavonoids and were shown to reduce the myocardial I/R injury. BAI was found to suppress ferroptosis in cancer cells via reducing reactive oxygen species (ROS) generation. However, the anti-ferroptosis effect of Lut on ferroptosis has not been reported. This study aimed to investigate whether ferroptosis reduction contributes to the BAI- and Lut-protected cardiomyocytes.

METHODS

This research used erastin, RSL3, and Fe-SP to induce ferroptosis. Cell viability was examined using MTT assay. Annexin V-FITC, CM-H₂DCFDA, and Phen Green SK diacetate (PGSK) fluorescent intensity were detected to analyze apoptotsis, ROS levels, and Fe²⁺ concentrations, respectively. qPCR and Western blot analysis were conducted to detect the levels of mRNA and protein, respectively.

RESULTS

Our data show that BAI and Lut protected cardiomyocytes against ferroptosis caused by ferroptosis inducers and I/R. Moreover, both BAI and Lut decreased ROS and malondialdehyde (MDA) generation and the protein levels of ferroptosis markers, and restored Glutathione peroxidase 4 (GPX4) protein levels in cardiomyocytes reduced by ferroptosis inducers. BAI and Lut reduced the I/R-induced myocardium infarction and decreased the levels of Acsl4 and Ptgs2 mRNA.

CONCLUSIONS

BAI and Lut could protect the cardiomyocytes against the I/R-induced ferroptosis via suppressing accumulation of ROS and MDA.

Arachidonate 15-lipoxygenase type B: Regulation, function, and its role in pathophysiology

As a lipoxygenase (LOX), arachidonate 15-lipoxygenase type B (ALOX15B) peroxidizes polyenoic fatty acids (PUFAs) including arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linoleic acid (LA) to their corresponding fatty acid hydroperoxides. Distinctive to ALOX15B, fatty acid oxygenation occurs with positional specificity, catalyzed by the non-heme iron containing active site, and in addition to free PUFAs, membrane-esterified fatty acids serve as substrates for ALOX15B. Like other LOX enzymes, ALOX15B is linked to the formation of specialized pro-resolving lipid mediators (SPMs), and altered expression is apparent in various inflammatory diseases such as asthma, psoriasis, and atherosclerosis. In primary human macrophages, ALOX15B expression is associated with cellular cholesterol homeostasis and is induced by hypoxia. Like in inflammation, the role of ALOX15B in cancer is inconclusive. In prostate and breast carcinomas, ALOX15B is attributed a tumor-suppressive role, whereas in colorectal cancer, ALOX15B expression is associated with a poorer prognosis. As the biological function of ALOX15B remains an open question, this review aims to provide a comprehensive overview of the current state of research related to ALOX15B.

Fatty acids and their lipid mediators in the induction of cellular apoptosis in cancer cells

The oxygenation of polyunsaturated fatty acids such as arachidonic and linoleic acid through enzymes like lipoxygenases (LOXs) are common and often leads to the production of various bioactive lipids that are important both in acute inflammation and its resolution and thus in disease progression. Amongst the several isoforms of LOX that are expressed in mammals, 15-lipoxygenase (15-LOX) has shown to be crucial in the context of inflammation. Moreover, being expressed in cells of the immune system, as well as in epithelial cells; the enzyme has been shown to crosstalk with a number of important signalling pathways. Mounting evidences from recent reports suggest that 15-LOX has anti-cancer activities which are dependent or independent of its metabolites, and is executed through several downstream pathways like cGMP, PPAR, p53, p21 and NAG-1. However, it is still unclear whether the up-regulation of 15-LOX is associated with cancer cell apoptosis. Monoamine oxidase A (MAO-A), on the other hand, is a mitochondrial flavoenzyme which is believed to be involved in the pathogenesis of atherosclerosis and inflammation and in many other neurological disorders. MAO-A has also been reported as a potential therapeutic target in different types of cancers like prostate cancer, lung cancer etc. In this review, we discussed about the role of fatty acids and their lipid mediators in cancer cell apoptosis. Here we particularly focused on the contribution of oxidative enzymes like 15-LOX and MAO-A in mediating apoptosis in lung cancer cell after fatty acid induction.

8-Geranyloxycarbostyril as a potent 15-LOX-1 inhibitor showed great anti-tumor effects against prostate cancer

Carbostyrils are quinolone derivatives, with possible growth inhibition properties on cancer cells. Unlike many tumors, 15-Lipoxygenase-1 (15-LOX-1) is highly expressed in prostate cancer (PCa) cells and has oncogenic properties. Here, with the hypothesis that 6-, 7- and 8-geranyloxycarbostyril (GQ) have inhibitory properties on 15-LOX-1, their effects were assessed on PCa cells. Their cytotoxic effects were evaluated by MTT assay and mechanism of cell death was investigated using annexin V/PI staining. Finally, the anti-tumor properties of 8-GQ were assessed in immunocompromised C57BL/6 mice bearing human PCa cells. Accordingly, these compounds could effectively inhibit 15-LOX activity in PCa cells. MTT and flow cytometry tests confirmed their toxic effects on PCa cells, with no significant toxicity on normal cells, and apoptosis was the main mechanism of cell death. In vivo results indicated that use of 8-GQ at 50 mg/kg had stronger anti-tumor effects than 5 mg/kg cisplatin, with fewer side effects on normal tissues. Therefore, 8-GQ can be introduced as a potential drug candidate with 15-LOX-1 inhibitory potency, which can be effective in treatment of prostate cancer, and should be considered for further drug screening investigations.

Involvement of Syndecan-1 and Heparanase in Cancer and Inflammation

The cell surface heparan sulfate proteoglycan Syndecan-1 acts as an important co-receptor for receptor tyrosine kinases and chemokine receptors, and as an adhesion receptor for structural glycoproteins of the extracellular matrix. It serves as a substrate for heparanase, an endo-β-glucuronidase that degrades specific domains of heparan sulfate carbohydrate chains and thereby alters the functional status of the proteoglycan and of Syndecan-1-bound ligands. Syndecan-1 and heparanase show multiple levels of functional interactions, resulting in mutual regulation of their expression, processing, and activity. These interactions are of particular relevance in the context of inflammation and malignant disease. Studies in animal models have revealed a mechanistic role of Syndecan-1 and heparanase in the regulation of contact allergies, kidney inflammation, multiple sclerosis, inflammatory bowel disease, and inflammation-associated tumorigenesis. Moreover, functional interactions between Syndecan-1 and heparanase modulate virtually all steps of tumor progression as defined in the Hallmarks of Cancer. Due to their prognostic value in cancer, and their mechanistic involvement in tumor progression, Syndecan-1 and heparanase have emerged as important drug targets. Data in preclinical models and preclinical phase I/II studies have already yielded promising results that provide a translational perspective.

Resolvin D1 and D2 inhibit tumour growth and inflammation via modulating macrophage polarization

Plastic polarization of macrophage is involved in tumorigenesis. M1-polarized macrophage mediates rapid inflammation, entity clearance and may also cause inflammation-induced mutagenesis. M2-polarized macrophage inhibits rapid inflammation but can promote tumour aggravation. ω-3 long-chain polyunsaturated fatty acid (PUFA)-derived metabolites show a strong anti-inflammatory effect because they can skew macrophage polarization from M1 to M2. However, their role in tumour promotive M2 macrophage is still unknown. Resolvin D1 and D2 (RvD1 and RvD2) are docosahexaenoic acid (DHA)-derived docosanoids converted by 15-lipoxygenase then 5-lipoxygenase successively. We found that although dietary DHA can inhibit prostate cancer in vivo, neither DHA (10 μmol/L) nor RvD (100 nmol/L) can directly inhibit the proliferation of prostate cancer cells in vitro. Unexpectedly, in a cancer cell-macrophage co-culture system, both DHA and RvD significantly inhibited cancer cell proliferation. RvD1 and RvD2 inhibited tumour-associated macrophage (TAM or M2d) polarization. Meanwhile, RvD1 and RvD2 also exhibited anti-inflammatory effects by inhibiting LPS-interferon (IFN)-γ-induced M1 polarization as well as promoting interleukin-4 (IL-4)-mediated M2a polarization. These differential polarization processes were mediated, at least in part, by protein kinase A. These results suggest that regulation of macrophage polarization using RvDs may be a potential therapeutic approach in the management of prostate cancer.

Stylosin and some of its synthetic derivatives induce apoptosis in prostate cancer cells as 15-lipoxygenase enzyme inhibitors

Overexpression of 15-lipoxygenase-1 (15-LOX-1) enzyme has been reported in prostate tumors, and its expression levels are associated with the degree of cancer malignancy. The aim of this study was to investigate inhibitory effects of stylosin and some similar synthetic monoterpenoids on 15-LOX and also their cytotoxic and anti-cancer activities on prostate cancer cells. Cytotoxicity of compounds was evaluated on prostate cancer cell line "PC-3" and normal human fibroblast "HFF3" cells using AlamarBlue reduction test. The inhibitory effects of the compounds against soybean 15-LOX, a commercially available enzyme, were also assessed. Finally, mechanism of cell death was investigated by flow cytometry. Some of these terpenoids had cytotoxic effects on PC-3 cells, and strong positive correlation was observed between the 15-LOX-1 inhibition potential and the cytotoxicity of the compounds. Moreover, flow cytometry results indicated that apoptosis was the predominant mechanism of induced cell death, which emphasizes the potential of these compounds in prostate cancer therapy. Among studied terpenoids, "fenchyl ferulate" exhibited about three times more cytotoxicity than cisplatin. Strong positive correlation observed between 15-LOX inhibition potential and cytotoxicity of the compounds indicates selective anti-cancer properties of the compounds might be exerted via inhibition of 15-LOX-1 in PC-3 cells. Furthermore, observed cytotoxicity is mediated through apoptosis, which is probably triggered via 15-LOX-1 inhibition.

Emerging role of 12/15-Lipoxygenase (ALOX15) in human pathologies

12/15-lipoxygenase (12/15-LOX) is an enzyme, which oxidizes polyunsaturated fatty acids, particularly omega-6 and -3 fatty acids, to generate a number of bioactive lipid metabolites. A large number of studies have revealed the importance of 12/15-LOX role in oxidative and inflammatory responses. The in vitro studies have demonstrated the ability of 12/15-LOX metabolites in the expression of various genes and production of cytokine related to inflammation and resolution of inflammation. The studies with the use of knockout and transgenic animals for 12/15-LOX have further shown its involvement in the pathogenesis of a variety of human diseases, including cardiovascular, renal, neurological and metabolic disorders. This review summarizes our current knowledge on the role of 12/15-LOX in inflammation and various human diseases.

12-HETE facilitates cell survival by activating the integrin-linked kinase/NF-κB pathway in ovarian cancer

Background

The dysfunction of cell apoptosis is an important event in the progression of cancer, and the growth of cancer cells is negatively regulated by cell apoptosis. In different types of cancers, inhibition of cellular apoptosis is often observed in the cancerous tissue, and increased resistance to apoptosis is a hallmark of cancer. Although previous studies have shown that 12-lipoxygenase (12-LOX)/12-hydroxyeicosatetraenoic acid (12-HETE) is activated and upregulated in different types of cancers, the consequences of 12-LOX/12-HETE upregulation and its precise roles in the survival of ovarian carcinoma cells are still unknown.

Methods

MTT assays, caspase activity assays, lactate dehydrogenase (LDH) assays, and Western blot analysis were the methods used in this study.

Results

In our study, we found that 12-HETE, a major metabolic product of arachidonic acid using 12-LOX catalysis, inhibited cell apoptosis in a dose-dependent manner and that the effects of 12-HETE on cell apoptosis were mediated by the integrin-linked kinase (ILK) pathway. Moreover, the downstream target of 12-HETE-activated ILK was nuclear factor kappa-B (NF-κB) in ovarian carcinoma. The inhibitory effects of 12-HETE on cell apoptosis were attenuated by the inhibition of the NF-κB pathway.

Conclusion

These results indicate that 12-HETE participates in the inhibition of cell apoptosis by activating the ILK/NF-κB pathway, implying an important underlying mechanism that promotes the survival of ovarian cancer cells.

Do lipoxygenases occur in viruses?: Expression and characterization of a viral lipoxygenase-like protein did not provide evidence for the existence of functional viral lipoxygenases

Lipoxygenases are lipid peroxidizing enzymes, which frequently occur in higher plants and animals. In bacteria, these enzymes are rare and have been introduced via horizontal gene transfer. Since viruses function as horizontal gene transfer vectors and since lipoxygenases may be helpful for releasing assembled virus particles from host cells we explored whether these enzymes may actually occur in viruses. For this purpose we developed a four-step in silico screening strategy and searching the publically available viral genomes for lipoxygenase-like sequences we detected a single functional gene in the genome of a mimivirus infecting Acantamoeba polyphaga. The primary structure of this protein involved two putative metal ligand clusters but the recombinant enzyme did neither contain iron nor manganese. Most importantly, it did not exhibit lipoxygenase activity. These data suggests that this viral lipoxygenase-like sequence does not encode a functional lipoxygenase and that these enzymes do not occur in viruses.

12/15 lipoxygenase: A crucial enzyme in diverse types of cell death

The 12/15-lipoxygenase (12/15-LOX) enzymes react with polyunsaturated fatty acids producing active lipid metabolites that are involved in plethora of human diseases including neurological disorders. A great many of elegant studies over the last decades have contributed to unraveling the mechanism how 12/15-lipoxygenase play a role in these diseases. And the way it works is mainly through apoptosis. However, recent years have found that the way 12/15-lipoxygenase works is also related to autophagy and ferroptosis, a newly defined type of cell death by Stockwell's lab in 2012. Figuring out how 12/15-lipoxygenase participate in these modes of cell death is of vital importance to understand its role in disease. The review aims to give a sight on our current knowledge on the role of this enzyme in apoptosis, autophagy and ferroptosis. And the relevant diseases that 12/15-lipoxygenase may be involved.

Anti-Inflammatory Effects of Omega-3 Fatty Acids in the Brain: Physiological Mechanisms and Relevance to Pharmacology

Classically, polyunsaturated fatty acids (PUFA) were largely thought to be relatively inert structural components of brain, largely important for the formation of cellular membranes. Over the past 10 years, a host of bioactive lipid mediators that are enzymatically derived from arachidonic acid, the main n-6 PUFA, and docosahexaenoic acid, the main n-3 PUFA in the brain, known to regulate peripheral immune function, have been detected in the brain and shown to regulate microglia activation. Recent advances have focused on how PUFA regulate the molecular signaling of microglia, especially in the context of neuroinflammation and behavior. Several active drugs regulate brain lipid signaling and provide proof of concept for targeting the brain. Because brain lipid metabolism relies on a complex integration of diet, peripheral metabolism, including the liver and blood, which supply the brain with PUFAs that can be altered by genetics, sex, and aging, there are many pathways that can be disrupted, leading to altered brain lipid homeostasis. Brain lipid signaling pathways are altered in neurologic disorders and may be viable targets for the development of novel therapeutics. In this study, we discuss in particular how n-3 PUFAs and their metabolites regulate microglia phenotype and function to exert their anti-inflammatory and proresolving activities in the brain.

Fish-Derived Omega-3 Fatty Acids and Prostate Cancer: A Systematic Review

BACKGROUND

The use of natural health products in prostate cancer (PrCa) is high despite a lack of evidence with respect to safety and efficacy. Fish-derived omega-3 fatty acids possess anti-inflammatory effects and preclinical data suggest a protective effect on PrCa incidence and progression; however, human studies have yielded conflicting results.

METHODS

A search of OVID MEDLINE, Pre-MEDLINE, Embase, and the Allied and Complementary Medicine Database (AMED) was completed for human interventional or observational data assessing the safety and efficacy of fish-derived omega-3 fatty acids in the incidence and progression of PrCa.

RESULTS

Of 1776 citations screened, 54 publications reporting on 44 studies were included for review and analysis: 4 reports of 3 randomized controlled trials, 1 nonrandomized clinical trial, 20 reports of 14 cohort studies, 26 reports of 23 case-control studies, and 3 case-cohort studies. The interventional studies using fish oil supplements in patients with PrCa showed no impact on prostate-specific antigen levels; however, 2 studies showed a decrease in inflammatory or other cancer markers. A small number of mild adverse events were reported and interactions with other interventions were not assessed. Cohort and case-control studies assessing the relationship between dietary fish intake and the risk of PrCa were equivocal. Cohort studies assessing the risk of PrCa mortality suggested an association between higher intake of fish and decreased risk of prostate cancer-related death.

CONCLUSIONS

Current evidence is insufficient to suggest a relationship between fish-derived omega-3 fatty acid and risk of PrCa. An association between higher omega-3 intake and decreased PrCa mortality may be present but more research is needed. More intervention trials or observational studies with precisely measured exposure are needed to assess the impact of fish oil supplements and dietary fish-derived omega-3 fatty acid intake on safety, PrCa incidence, treatment, and progression.

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.

Toxic effects of n-3 polyunsaturated fatty acids in human lung A549 cells

N-3 polyunsaturated fatty acids (PUFAs), particularly eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6) are crucial for the prevention of lung cancer. PUFAs may act through alteration of membrane fluidity and cell surface receptor functions; modulation of cyclooxygenase activity; and increased cellular oxidative stress, which may induce apoptosis and autophagy. Therefore the aim of the study was to investigate whether EPA and DHA (25-100 μM) are able to reduce human lung cancer cell growth through oxidative stress influence on autophagy and apoptosis. It was found that both EPA and DHA in the concentration-dependent manner suppressed the cell viability, enhanced cell death, induced activation of caspase-3/7 and potentiated intracellular oxidative DNA and protein damage. In response to PUFAs intracellular autophagic vacuolization occurred and the observed effect was reverted when the autophagy inhibitor 3-methyladenine (3-MA) was applied. The inhibition of the autophagic process enhanced the cell viability, suppressed cell death, and decreased activation of caspase-3/7 indicating that EPA and DHA-induced autophagy amplified A549 apoptotic cell death.

Mammalian lipoxygenases and their biological relevance

Lipoxygenases (LOXs) form a heterogeneous class of lipid peroxidizing enzymes, which have been implicated not only in cell proliferation and differentiation but also in the pathogenesis of various diseases with major public health relevance. As other fatty acid dioxygenases LOXs oxidize polyunsaturated fatty acids to their corresponding hydroperoxy derivatives, which are further transformed to bioactive lipid mediators (eicosanoids and related substances). On the other hand, lipoxygenases are key players in the regulation of the cellular redox homeostasis, which is an important element in gene expression regulation. Although the first mammalian lipoxygenases were discovered 40 years ago and although the enzymes have been well characterized with respect to their structural and functional properties the biological roles of the different lipoxygenase isoforms are not completely understood. This review is aimed at summarizing the current knowledge on the physiological roles of different mammalian LOX-isoforms and their patho-physiological function in inflammatory, metabolic, hyperproliferative, neurodegenerative and infectious disorders. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

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.

The omega-3 polyunsaturated fatty acid DHA induces simultaneous apoptosis and autophagy via mitochondrial ROS-mediated Akt-mTOR signaling in prostate cancer cells expressing mutant p53

Docosahexaenoic acid (DHA) induces autophagy-associated apoptotic cell death in wild-type p53 cancer cells via regulation of p53. The present study investigated the effects of DHA on PC3 and DU145 prostate cancer cell lines harboring mutant p53. Results show that, in addition to apoptosis, DHA increased the expression levels of lipidated form LC3B and potently stimulated the autophagic flux, suggesting that DHA induces both autophagy and apoptosis in cancer cells expressing mutant p53. DHA led to the generation of mitochondrial reactive oxygen species (ROS), as shown by the mitochondrial ROS-specific probe mitoSOX. Similarly, pretreatment with the antioxidant N-acetyl-cysteine (NAC) markedly inhibited both the autophagy and the apoptosis triggered by DHA, indicating that mitochondrial ROS mediate the cytotoxicity of DHA in mutant p53 cells. Further, DHA reduced the levels of phospho-Akt and phospho-mTOR in a concentration-dependent manner, while NAC almost completely blocked that effect. Collectively, these findings present a novel mechanism of ROS-regulated apoptosis and autophagy that involves Akt-mTOR signaling in prostate cancer cells with mutant p53 exposed to DHA.