Mechanisms Regulating Tumor Angiogenesis by 12-Lipoxygenase in Prostate Cancer Cells

Mechanism of baicalein in treatment of castration-resistant prostate cancer based on network pharmacology and cell experiments

Objective

Baicalein, one of the most abundant flavonoids found in Chinese herb Scutellaria baicalensis Georgi, exhibits pharmacological activities against various cancers. However, the precise pharmacological mechanism of baicalein in treating castration-resistant prostate cancer (CRPC) remains elusive. This study aimed to elucidate the potential mechanism of baicalein against CRPC through a combination of network pharmacology and experimental approaches, thereby providing new avenues for research in CRPC treatment.

Methods

The pharmacological and molecular properties of baicalein were obtained using the TCMSP database. Baicalein-related targets were collected from multiple sources including SwissTargetPrediction, PharmMapper and CTD. Targets related to CRPC were acquired from DisGeNET, GeneCards, and CTD. The protein-protein interaction (PPI) was analyzed using STRING 11.5, and Cytoscape 3.7.2 software was utilized to explore the core targets of baicalein on CRPC. GO and KEGG pathway enrichment analysis were performed using DAVID database. Cell experiments were carried out to confirm the validity of the targets.

Results

A total of 131 potential targets of baicalein for the treatment of CRPC were obtained. Among them, TP53, AKT1, ALB, CASP3, and HSP90AA1, etc., were recognized as core targets by Cytoscape 3.7.2. GO function enrichment analysis yielded 926 entries, including 703 biological process (BP) terms, 84 cellular component (CC) terms and 139 molecular function (MF) terms. The KEGG pathway enrichment analysis unveiled 159 signaling pathways, mainly involved in Pathways in cancer, prostate cancer, AGE-RAGE signaling pathway in diabetic complications, TP53 signaling pathway, and PI3K-Akt signaling pathway, etc. Cell experiments confirmed that baicalein may inhibit the proliferation of CRPC cells and induce cell cycle arrest in the G1 phase. This effect could be associated with the TP53/CDK2/cyclin E1 pathway. In addition, the results of CETSA suggest that baicalein may directly bind to TP53.

Conclusion

Based on network pharmacology analysis and cell experiments, we have predicted and validated the potential targets and related pathways of baicalein for CRPC treatment. This comprehensive approach provides a scientific basis for elucidating the molecular mechanism underlying the action of baicalein in CRPC treatment. Furthermore, these findings offer valuable insights and serve as a reference for the research and development of novel anti-CRPC drugs.

Arachidonic acid in aging: New roles for old players

BACKGROUND

Arachidonic acid (AA), one of the most ubiquitous polyunsaturated fatty acids (PUFAs), provides fluidity to mammalian cell membranes. It is derived from linoleic acid (LA) and can be transformed into various bioactive metabolites, including prostaglandins (PGs), thromboxanes (TXs), lipoxins (LXs), hydroxy-eicosatetraenoic acids (HETEs), leukotrienes (LTs), and epoxyeicosatrienoic acids (EETs), by different pathways. All these processes are involved in AA metabolism. Currently, in the context of an increasingly visible aging world population, several scholars have revealed the essential role of AA metabolism in osteoporosis, chronic obstructive pulmonary disease, and many other aging diseases.

AIM OF REVIEW

Although there are some reviews describing the role of AA in some specific diseases, there seems to be no or little information on the role of AA metabolism in aging tissues or organs. This review scrutinizes and highlights the role of AA metabolism in aging and provides a new idea for strategies for treating aging-related diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

As a member of lipid metabolism, AA metabolism regulates the important lipids that interfere with the aging in several ways. We present a comprehensivereviewofthe role ofAA metabolism in aging, with the aim of relieving the extreme suffering of families and the heavy economic burden on society caused by age-related diseases. We also collected and summarized data on anti-aging therapies associated with AA metabolism, with the expectation of identifying a novel and efficient way to protect against aging.

Enantioselectivity in some physiological and pathophysiological roles of hydroxyeicosatetraenoic acids

The phenomenon of chirality has been shown to greatly impact drug activities and effects. Different enantiomers may exhibit different effects in a certain biological condition or disease state. Cytochrome P450 (CYP) enzymes metabolize arachidonic acid (AA) into a large variety of metabolites with a wide range of activities. Hydroxylation of AA by CYP hydroxylases produces hydroxyeicosatetraenoic acids (HETEs), which are classified into mid-chain (5, 8, 9, 11, 12, and 15-HETE), subterminal (16-, 17-, 18- and 19-HETE) and terminal (20-HETE) HETEs. Except for 20-HETE, these metabolites exist as a racemic mixture of R and S enantiomers in the physiological system. The two enantiomers could have different degrees of activity or sometimes opposing effects. In this review article, we aimed to discuss the role of mid-chain and subterminal HETEs in different organs, importantly the heart and the kidneys. Moreover, we summarized their effects in some conditions such as neutrophil migration, inflammation, angiogenesis, and tumorigenesis, with a focus on the reported enantiospecific effects. We also reported some studies using genetically modified models to investigate the roles of HETEs in different conditions.

Baicalin and baicalein in modulating tumor microenvironment for cancer treatment: A comprehensive review with future perspectives

Cancer is a leading cause of death worldwide. The burden of cancer incidence and mortality is increasing rapidly. New approaches to cancer prevention and treatment are urgently needed. Natural products are reliable and powerful sources for anticancer drug discovery. Baicalin and baicalein, two major flavones isolated from Scutellaria baicalensis Georgi, a multi-purpose traditional medicinal plant in China, exhibit anticancer activities against multiple cancers. Of note, these phytochemicals exhibit extremely low toxicity to normal cells. Besides their cytotoxic and cytostatic activities toward diverse tumor cells, recent studies demonstrated that baicalin and baicalein modulate a variety of tumor stromal cells and extracellular matrix (ECM) in the tumor microenvironment (TME), which is essential for tumorigenesis, cancer progression and metastasis. In this review, we summarize the therapeutic potential and the mechanism of action of baicalin and baicalein in the regulation of tumor microenvironmental immune cells, endothelial cells, fibroblasts, and ECM that reshape the TME and cancer signaling, leading to inhibition of tumor angiogenesis, progression, and metastasis. In addition, we discuss the biotransformation pathways of baicalin and baicalein, related therapeutic challenges and the future research directions to improve their bioavailability and clinical anticancer applications. Recent advances of baicalin and baicalein warrant their continued study as important natural ways for cancer interception and therapy.

Urine metabolomics for assessing fertility-sparing treatment efficacy in endometrial cancer: a non-invasive approach using ultra-performance liquid chromatography mass spectrometry

OBJECTIVE

This study aimed to reveal the urine metabolic change of endometrial cancer (EC) patients during fertility-sparing treatment and establish non-invasive predictive models to identify patients with complete remission (CR).

METHOD

This study enrolled 20 EC patients prior to treatment (PT) and 22 patients with CR, aged 25-40 years. Eligibility criteria consisted of stage IA high-grade EC, lesions confined to endometrium, normal hepatic and renal function, normal urine test, no contraindication for fertility-sparing treatment and no prior therapy. Urine samples were analyzed using ultraperformance liquid chromatography mass spectrometry (UPLC-MS), a technique chosen for its high sensitivity and resolution, allows for rapid, accurate identification and quantification of metabolites, providing a comprehensive metabolic profile and facilitating the discovery of potential biomarkers. Analytical techniques were employed to determine distinct metabolites and altered metabolic pathways. The statistical analyses were performed using univariate and multivariate analyses, logistic regression and receiver operating characteristic (ROC) curves to discover and validate the potential biomarker models.

RESULTS

A total of 108 different urine metabolomes were identified between CR and PT groups. These metabolites were enriched in ascorbate and aldarate metabolism, one carbon pool by folate, and some amino acid metabolisms pathways. A panel consisting of Baicalin, 5beta-1,3,7 (11)-Eudesmatrien-8-one, Indolylacryloylglycine, Edulitine, and Physapubenolide were selected as biomarkers, which demonstrated the best predictive ability with the AUC values of 0.982/0.851 in training/10-fold-cross-validation group, achieving a sensitivity of 0.975 and specificity of 0.967, respectively.

CONCLUSION

The urine metabolic analysis revealed the metabolic changes in EC patients during the fertility-sparing treatment. The predictive biomarkers present great potential diagnostic value in fertility-sparing treatments for EC patients, offering a less invasive means of monitoring treatment efficacy. Further research should explore the mechanistic underpinnings of these metabolic changes and validate the biomarker panel in larger, diverse populations due to the small sample size and single-institution nature of our study.

A review on the relationship between Arachidonic acid 15-Lipoxygenase (ALOX15) and diabetes mellitus

Arachidonic acid 15-lipoxygenase (ALOX15), as one of the lipoxygenase family, is mainly responsible for catalyzing the oxidation of various fatty acids to produce a variety of lipid components, contributing to the pathophysiological processes of various immune and inflammatory diseases. Studies have shown that ALOX15 and its related products are widely distributed in human tissues and related to multiple diseases such as liver, cardiovascular, cerebrovascular diseases, diabetes mellitus and other diseases. Diabetes mellitus (DM), the disease studied in this article, is a metabolic disease characterized by a chronic increase in blood glucose levels, which is significantly related to inflammation, oxidative stress, ferroptosis and other mechanisms, and it has a high incidence in the population, accompanied by a variety of complications. Figuring out how ALOX15 is involved in DM is critical to understanding its role in diseases. Therefore, ALOX15 inhibitors or combination therapy containing inhibitors may deliver a novel research direction for the treatment of DM and its complications. This article aims to review the biological effect and the possible function of ALOX15 in the pathogenesis of DM.

Biology and pharmacology of platelet-type 12-lipoxygenase in platelets, cancer cells, and their crosstalk

Platelet-type lipoxygenase (pl12-LOX), encoded by ALOX12, catalyzes the production of the lipid mediator 12S-hydroperoxyeicosa-5,8,10,14-tetraenoic acid (12S-HpETE), which is quickly reduced by cellular peroxidases to form 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12S-HETE). Platelets express high levels of pl12-LOX and generate considerable amounts of 12S-HETE from arachidonic acid (AA; C20:4, n-6). The development of sensitive chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods has allowed the accurate quantification of 12S-HETE in biological samples. Moreover, advances in the knowledge of the mechanism of action of 12S-HETE have been achieved. The orphan G-protein-coupled receptor 31 (GPR31) has been identified as the high-affinity 12S-HETE receptor. Moreover, upon platelet activation, 12S-HETE is produced, and significant amounts are found esterified to membrane phospholipids (PLs), such as phosphatidylethanolamine (PE) and phosphatidylcholine (PC), promoting thrombin generation. Platelets play many roles in cancer metastasis. Among them, the platelets' ability to interact with cancer cells and transfer platelet molecules by the release of extracellular vesicles (EVs) is noteworthy. Recently, it was found that platelets induce epithelial-mesenchymal transition(EMT) in cancer cells, a phenomenon known to confer high-grade malignancy, through the transfer of pl12-LOX contained in platelet-derived EVs. These cancer cells now generate 12-HETE, considered a key modulator of cancer metastasis. Interestingly, 12-HETE was mainly found esterified in plasmalogen phospholipids of cancer cells. This review summarizes the current knowledge on the regulation and functions of pl12-LOX in platelets and cancer cells and their crosstalk.Novel approaches to preventing cancer and metastasis by the pharmacological inhibition of pl12-LOX and the internalization of mEVs are discussed.

ML355 Modulates Platelet Activation and Prevents ABT-737 Induced Apoptosis in Platelets

12-lipoxigenase (12-LOX) is implicated in regulation of platelet activation processes and can be a new promising target for antiplatelet therapy. However, investigations of 12-LOX were restricted by the lack of specific and potent 12-LOX inhibitors and by controversial data concerning the role of 12-LOX metabolites in platelet functions. A novel specific 12-LOX inhibitor ML355 was shown to inhibit platelet aggregation without adverse side effects on hemostasis; however, the molecular mechanisms of its action on platelets are poorly understood. Here, we showed that ML355 inhibited platelet activation induced by thrombin or thromboxane A2, but not by collagen-related peptide. ML355 blocked protein kinase B, phosphoinositide 3-kinase, and extracellular signal-regulated kinase, but not p38 kinase, spleen tyrosine kinase (Syk), or phospholipase Cγ2 phosphorylation in activated platelets. The main inhibitory effect of low doses of ML355 (1-20 μM) on thrombin activated platelets was mediated by the decrease in reactive oxygen species level, whereas high doses of ML355 (50 μM) caused cyclic adenosine monophosphate activation. ML355 did not affect the activity of nitric oxide-dependent soluble guanylyl cyclase, nor did it affect the relaxation of preconstricted aortic rings in mice. ML355 itself did not affect platelet viability, but at 50 μM dose blocked caspase-dependent apoptosis induced by B-cell lymphoma II inhibitor ABT-737. SIGNIFICANCE STATEMENT: The current paper provides novel and original data concerning molecular mechanisms of 12-LOX inhibitor ML355 action on platelets. These data reveal antiplatelet and protective effects of ML355 on platelets and may be of importance for both antiplatelet and anticancer therapy.

An overview of pharmacological activities of baicalin and its aglycone baicalein: New insights into molecular mechanisms and signaling pathways

The flavonoids, baicalin, and its aglycone baicalein possess multi-fold therapeutic properties and are mainly found in the roots of Oroxylum indicum (L.) Kurz and Scutellaria baicalensis Georgi. These flavonoids have been reported to possess various pharmacological properties, including antibacterial, antiviral, anticancer, anticonvulsant, anti-oxidant, hepatoprotective, and neuroprotective effects. The pharmacological properties of baicalin and baicalein are due to their abilities to scavenge reactive oxygen species (ROS) and interaction with various signaling molecules associated with apoptosis, inflammation, autophagy, cell cycle, mitochondrial dynamics, and cytoprotection. In this review, we summarized the molecular mechanisms underlying the chemopreventive and chemotherapeutic applications of baicalin and baicalein in the treatment of cancer and inflammatory diseases. In addition, the preventive effects of baicalin and baicalein on mitochondrial dynamics and functions were highlighted with a particular emphasis on their anti-oxidative and cytoprotective properties. The current review highlights could be useful for future prospective studies to further improve the pharmacological applications of baicalein and baicalin. These studies should define the threshold for optimal drug exposure, dose optimization and focus on therapeutic drug monitoring, objective disease markers, and baicalin/baicalein drug levels.

Targeting Lipid Peroxidation for Cancer Treatment

Cancer is one of the highest prevalent diseases in humans. The chances of surviving cancer and its prognosis are very dependent on the affected tissue, body location, and stage at which the disease is diagnosed. Researchers and pharmaceutical companies worldwide are pursuing many attempts to look for compounds to treat this malignancy. Most of the current strategies to fight cancer implicate the use of compounds acting on DNA damage checkpoints, non-receptor tyrosine kinases activities, regulators of the hedgehog signaling pathways, and metabolic adaptations placed in cancer. In the last decade, the finding of a lipid peroxidation increase linked to 15-lipoxygenases isoform 1 (15-LOX-1) activity stimulation has been found in specific successful treatments against cancer. This discovery contrasts with the production of other lipid oxidation signatures generated by stimulation of other lipoxygenases such as 5-LOX and 12-LOX, and cyclooxygenase (COX-2) activities, which have been suggested as cancer biomarkers and which inhibitors present anti-tumoral and antiproliferative activities. These findings support the previously proposed role of lipid hydroperoxides and their metabolites as cancer cell mediators. Depletion or promotion of lipid peroxidation is generally related to a specific production source associated with a cancer stage or tissue in which cancer originates. This review highlights the potential therapeutical use of chemical derivatives to stimulate or block specific cellular routes to generate lipid hydroperoxides to treat this disease.

Druggable Lipid GPCRs: Past, Present, and Prospects

G protein-coupled receptors (GPCRs) have seven transmembrane spanning domains and comprise the largest superfamily with ~800 receptors in humans. GPCRs are attractive targets for drug discovery because they transduce intracellular signaling in response to endogenous ligands via heterotrimeric G proteins or arrestins, resulting in a wide variety of physiological and pathophysiological responses. The endogenous ligands for GPCRs are highly chemically diverse and include ions, biogenic amines, nucleotides, peptides, and lipids. In this review, we follow the KonMari method to better understand druggable lipid GPCRs. First, we have a comprehensive tidying up of lipid GPCRs including receptors for prostanoids, leukotrienes, specialized pro-resolving mediators (SPMs), lysophospholipids, sphingosine 1-phosphate (S1P), cannabinoids, platelet-activating factor (PAF), free fatty acids (FFAs), and sterols. This tidying up consolidates 46 lipid GPCRs and declutters several perplexing lipid GPCRs. Then, we further tidy up the lipid GPCR-directed drugs from the literature and databases, which identified 24 clinical drugs targeting 16 unique lipid GPCRs available in the market and 44 drugs under evaluation in more than 100 clinical trials as of 2019. Finally, we introduce drug designs for GPCRs that spark joy, such as positive or negative allosteric modulators (PAM or NAM), biased agonism, functional antagonism like fingolimod, and monoclonal antibodies (MAbs). These strategic drug designs may increase the efficacy and specificity of drugs and reduce side effects. Technological advances will help to discover more endogenous lipid ligands from the vast number of remaining orphan GPCRs and will also lead to the development novel lipid GPCR drugs to treat various diseases.

The enzymology of human eicosanoid pathways: the lipoxygenase branches

Eicosanoids are short-lived derivatives of polyunsaturated fatty acids that serve as autocrine and paracrine signaling molecules. They are involved numerous biological processes of both the well state and disease states. A thorough understanding of the progression the disease state and homeostasis of the well state requires a complete evaluation of the systems involved. This review examines the enzymology for the enzymes involved in the production of eicosanoids along the lipoxygenase branches of the eicosanoid pathways with particular emphasis on those derived from arachidonic acid. The enzymatic parameters, protocols to measure them, and proposed catalytic mechanisms are presented in detail.

Nordihydroguaiaretic Acid: From Herbal Medicine to Clinical Development for Cancer and Chronic Diseases

Nordihydroguaiaretic acid (NDGA) is a phenolic lignan obtained from Larrea tridentata, the creosote bush found in Mexico and USA deserts, that has been used in traditional medicine for the treatment of numerous diseases such as cancer, renal, cardiovascular, immunological, and neurological disorders, and even aging. NDGA presents two catechol rings that confer a very potent antioxidant activity by scavenging oxygen free radicals and this may explain part of its therapeutic action. Additional effects include inhibition of lipoxygenases (LOXs) and activation of signaling pathways that impinge on the transcription factor Nuclear Factor Erythroid 2-related Factor (NRF2). On the other hand, the oxidation of the catechols to the corresponding quinones my elicit alterations in proteins and DNA that raise safety concerns. This review describes the current knowledge on NDGA, its targets and side effects, and its synthetic analogs as promising therapeutic agents, highlighting their mechanism of action and clinical projection towards therapy of neurodegenerative, liver, and kidney disease, as well as cancer.

12-Lipoxygenase promotes epithelial-mesenchymal transition via the Wnt/β-catenin signaling pathway in gastric cancer cells

Background

12-Lipoxygenase (12-LOX) plays a major role in the progression and metastasis of various types of cancer. In gastric cancer (GC), the expression level of 12-LOX is significantly up-regulated; however, its function, and underlying mechanism of action remain unclear.

Methods

The mRNA and protein expression levels of 12-LOX were assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analyses, respectively, in GC cell lines. 12-LOX expression was stably up-regulated using lentiviral vector in BGC823 and MGC803 cells, and cell-counting kit-8 (CCK8), colony formation, and invasion assays were performed to verify the function of 12-LOX in proliferation and metastasis. In addition, the expression levels of epithelial-mesenchymal transition (EMT) differentiation markers and downstream targets of the Wnt/β-catenin signaling pathway were examined by Western blotting. A nude mouse model of tumor growth and metastasis was established to investigate the role of 12-LOX in vivo.

Results

Our findings demonstrate that 12-LOX mRNA and protein were highly expressed in GC cell lines. 12-LOX overexpression promoted GC cell proliferation, migration, and invasion both in vitro and in vivo. In addition, up-regulation of 12-LOX promoted the EMT in GC cells, as reflected by a decrease in E-cadherin expression and an increase in N-cadherin and Snail expression. 12-LOX overexpression in GC cells also increased the expression of multiple downstream targets of the Wnt/β-catenin signaling pathway.

Conclusion

These findings revealed that 12-LOX functions as an oncogene in promoting GC cell proliferation and metastasis in vitro and in vivo. In addition, 12-LOX might regulate the EMT via the Wnt/β-catenin signaling pathway, indicating a potential role for 12-LOX as a target in GC treatment.

Eicosanoids in prostate cancer

Many epidemiological studies revealed an association of dietary consumption of fatty acids and prostate cancer. Linoleic acid and alpha-linolenic acid and their derivatives such as arachidonic acid and eicosapentanoic acid are important polyunsaturated fatty acids in animal fats and in many vegetable oils. Their metabolism at the cellular level by enzymes such as lipoxygenases and cycloxygenases produces the group of eicosanoids molecules with many biological roles and activities in a variety of human diseases including cancer. In this review, we describe the biological activities of lipids with focus in eicosanoids and prostate cancer.

Fatty Acids and Calcium Regulation in Prostate Cancer

Prostate cancer is a widespread malignancy characterized by a comparative ease of primary diagnosis and difficulty in choosing the individualized course of treatment. Management of prostate cancer would benefit from a clearer understanding of the molecular mechanisms behind the transition to the lethal, late-stage forms of the disease, which could potentially yield new biomarkers for differential prognosis and treatment prioritization in addition to possible new therapeutic targets. Epidemiological research has uncovered a significant correlation of prostate cancer incidence and progression with the intake (and often co-intake) of fatty acids and calcium. Additionally, there is evidence of the impact of these nutrients on intracellular signaling, including the mechanisms mediated by the calcium ion as a second messenger. The present review surveys the recent literature on the molecular mechanisms associated with the critical steps in the prostate cancer progression, with special attention paid to the regulation of these processes by fatty acids and calcium homeostasis. Testable hypotheses are put forward that integrate some of the recent results in a more unified picture of these phenomena at the interface of cell signaling and metabolism.

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.

Targeting arachidonic acid pathway by natural products for cancer prevention and therapy

Arachidonic acid (AA) pathway, a metabolic process, plays a key role in carcinogenesis. Hence, AA pathway metabolic enzymes phospholipase A₂s (PLA₂s), cyclooxygenases (COXs) and lipoxygenases (LOXs) and their metabolic products, such as prostaglandins and leukotrienes, have been considered novel preventive and therapeutic targets in cancer. Bioactive natural products are a good source for development of novel cancer preventive and therapeutic drugs, which have been widely used in clinical practice due to their safety profiles. AA pathway inhibitory natural products have been developed as chemopreventive and therapeutic agents against several cancers. Curcumin, resveratrol, apigenin, anthocyans, berberine, ellagic acid, eugenol, fisetin, ursolic acid, [6]-gingerol, guggulsteone, lycopene and genistein are well known cancer chemopreventive agents which act by targeting multiple pathways, including COX-2. Nordihydroguaiaretic acid and baicalein can be chemopreventive molecules against various cancers by inhibiting LOXs. Several PLA₂s inhibitory natural products have been identified with chemopreventive and therapeutic potentials against various cancers. In this review, we critically discuss the possible utility of natural products as preventive and therapeutic agents against various oncologic diseases, including prostate, pancreatic, lung, skin, gastric, oral, blood, head and neck, colorectal, liver, cervical and breast cancers, by targeting AA pathway. Further, the current status of clinical studies evaluating AA pathway inhibitory natural products in cancer is reviewed. In addition, various emerging issues, including bioavailability, toxicity and explorability of combination therapy, for the development of AA pathway inhibitory natural products as chemopreventive and therapeutic agents against human malignancy are also discussed.

Anti-cancer effects of baicalein in non-small cell lung cancer in-vitro and in-vivo

Background

Baicalein is a widely used Chinese herbal medicine derived from Scutellaria baicalenesis, which has been traditionally used as anti-inflammatory and anti-cancer therapy. In this study we examined the anti-tumour pathways activated following baicalein treatment in non-small cell lung cancer (NSCLC), both in-vitro and in-vivo.

Methods

The effect of baicalein treatment on H-460 cells in-vitro was assessed using both BrdU assay (cell proliferation) and High Content Screening (multi-parameter apoptosis assay). A xenograft nude mouse model was subsequently established using these cells and the effect of baicalein on tumour growth and survival assessed in-vivo. Tumours were harvested from these mice and histological tissue analysis carried out. VEGF, 12-lipoxygenase and microvessel density (CD-31) were assessed by immunohistochemistry (IHC), while H and E staining was carried out to assess mitotic index. Gene expression profiling was carried out on corresponding RNA samples using Human Cancer Pathway Finder Arrays and qRT-PCR, with further gene expression analysis carried out using qRT-PCR.

Results

Baicalein significantly decreased lung cancer proliferation in H-460 cells in a dose dependent manner. At the functional level, a dose-dependent induction in apoptosis associated with decreased cellular f-actin content, an increase in nuclear condensation and an increase in mitochondrial mass potential was observed. Orthotopic treatment of experimental H-460 tumours in athymic nude mice with baicalein significantly (p < 0.05) reduced tumour growth and prolonged survival. Histological analysis of resulting tumour xenografts demonstrated reduced expression of both 12-lipoxygenase and VEGF proteins in baicalein-treated tumours, relative to untreated. A significant (p < 0.01) reduction in both mitotic index and micro-vessel density was observed following baicalein treatment. Gene expression profiling revealed a reduction (p < 0.01) in both VEGF and FGFR-2 following baicalein treatment, with a corresponding increase (p < 0.001) in RB-1.

Conclusion

This study is the first to demonstrate efficacy of baicalein both in-vitro and in-vivo in NSCLC. These effects may be mediated in part through a reduction in both cell cycle progression and angiogenesis. At the molecular level, alterations in expression of VEGF, FGFR-2, and RB-1 have been implicated, suggesting a molecular mechanism underlying this in-vivo effect.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2740-0) contains supplementary material, which is available to authorized users.

Leukotriene B4 Receptor 2 Is Critical for the Synthesis of Vascular Endothelial Growth Factor in Allergen-Stimulated Mast Cells

Mast cells are among the principal effector cells in the pathogenesis of allergic asthma. In allergic reactions, allergen (Ag)-induced cross-linking of IgE bound to FcεRI on mast cells results in the production of vascular endothelial growth factor (VEGF), which is essential for the initiation and development of the allergic response. Despite the central role of VEGF in allergic asthma, the signaling events responsible for the production of VEGF remain unclear, particularly in Ag-stimulated mast cells. In the present study, we observed that blocking leukotriene B4 receptor 2 (BLT2) completely abrogated the production of VEGF in Ag-stimulated bone marrow-derived mast cells (BMMCs). The synthesis of BLT2 ligands (leukotriene B4 and 12(S)-hydroxyeicosatetraenoic acid) was also required for VEGF production, suggesting a mediating role of an autocrine BLT2 ligands-BLT2 axis in the production of VEGF in mast cells. The NADPH oxidase 1-reactive oxygen species-NF-κB cascade is downstream of BLT2 during Ag signaling to VEGF synthesis in mast cells. Furthermore, the level of VEGF synthesis in genetically mast cell-deficient Kit(W/Wv) mice was significantly lower than that in wild-type mice in the OVA-induced asthma model, suggesting that mast cells play a critical role in the synthesis of VEGF in OVA-induced allergic asthma. Importantly, VEGF production was restored to the levels observed in wild-type mice after adoptive transfer of normal BMMCs into Kit(W/Wv) mice but was not restored in BLT2(-/-) BMMC-reconstituted Kit(W/Wv) mice in the OVA-induced asthma model. Taken together, our results suggest that BLT2 expression in mast cells is essential for the production of VEGF in OVA-induced allergic asthma.

12-HETER1/GPR31, a high-affinity 12(S)-hydroxyeicosatetraenoic acid receptor, is significantly up-regulated in prostate cancer and plays a critical role in prostate cancer progression

Previously we identified and deorphaned G-protein-coupled receptor 31 (GPR31) as the high-affinity 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] receptor (12-HETER1). Here we have determined its distribution in prostate cancer tissue and its role in prostate tumorigenesis using in vitro and in vivo assays. Data-mining studies strongly suggest that 12-HETER1 expression positively correlates with the aggressiveness and progression of prostate tumors. This was corroborated with real-time PCR analysis of human prostate tumor tissue arrays that revealed the expression of 12-HETER1 positively correlates with the clinical stages of prostate cancers and Gleason scores. Immunohistochemistry analysis also proved that the expression of 12-HETER1 is positively correlated with the grades of prostate cancer. Knockdown of 12-HETER1 in prostate cancer cells markedly reduced colony formation and inhibited tumor growth in animals. To discover the regulatory factors, 5 candidate 12-HETER1 promoter cis elements were assayed as luciferase reporter fusions in Chinese hamster ovary (CHO) cells, where the putative cis element required for gene regulation was mapped 2 kb upstream of the 12-HETER1 transcriptional start site. The data implicate 12-HETER1 in a critical new role in the regulation of prostate cancer progression and offer a novel alternative target for therapeutic intervention.-Honn, K. V., Guo, Y., Cai, Y., Lee, M.-J., Dyson, G., Zhang, W., Tucker, S. C. 12-HETER1/GPR31, a high-affinity 12(S)-hydroxyeicosatetraenoic acid receptor, is significantly up-regulated in prostate cancer and plays a critical role in prostate cancer progression.

(5Z,11Z,15R)-15-Hydroxyeicosa-5,11-dien-13-ynoic acid: A stable isomer of 15(S)-HETE that retains key vasoconstrictive and antiproliferative activity

15(S)-Hydroxyeicosa-(5Z,8Z,11Z,13E)-tetraenoic acid (15(S)-HETE) is a metabolite of arachidonic acid that elicits a number of biological effects including vasoconstriction and angiogenesis. (5Z,11Z,15R)-15-Hydroxyeicosa-5,11-dien-13-ynoic acid (HETE analog 1) is a synthetic isomer of 15(S)-HETE that is much more stable to autoxidation. Using isometric recording of isolated pulmonary arteries from male and female rabbits, HETE analog 1 and 15(S)-HETE were found to elicit concentration-dependent contractions that were slightly greater in females compared to males. The maximal response in females was greater with 15(S)-HETE. HETE analog 1 and 15(S)-HETE increased [(3)H]-thymidine incorporation in vascular smooth muscle cells cultured from male rabbit pulmonary arteries; both the maximal response and potency were greater with 15(S)-HETE. In contrast, HETE analog 1 produced a concentration-dependent inhibition in proliferation and migration of human hormone-independent prostate carcinoma PC-3 cells. The protocol for synthesis of HETE analog 1 is reported. The stability of this substance and its similar biological profile to 15(S)-HETE support future studies in eicosanoid research.

Expression of cyclooxygenase-2, 12-lipoxygenase, and inducible nitric oxide synthase in head and neck squamous cell carcinoma

AIM

The objective of this study was to investigate whether cyclooxygenase-2 (COX-2), 12-lipoxygenase (12-LOX), and inducible nitric oxide synthase (iNOS) have a role in carcinogenesis of head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

Twenty-two patients with HNSCC were included in the study. Cancer tissues and adjacent normal mucosa were obtained from each patient. Real-time PCR was used to assess the expression of COX-2, 12-LOX, and iNOS.

RESULTS

COX-2 and 12-LOX mRNA expressions are significantly increased in HNSCC compared with adjacent normal mucosa. Expression of iNOS was not significantly elevated in overall head and neck cancer tissues compared with normal mucosa. However, iNOS expression was found to be significantly elevated in patients with laryngeal cancer.

CONCLUSION

These data suggest that COX-2 and 12-LOX may play a role in carcinogenesis of head and neck cancer. iNOS as well as COX-2 and 12-LOX may play a role in carcinogenesis of laryngeal cancer.

Biosynthesis, biological effects, and receptors of hydroxyeicosatetraenoic acids (HETEs) and oxoeicosatetraenoic acids (oxo-ETEs) derived from arachidonic acid

Arachidonic acid can be oxygenated by a variety of different enzymes, including lipoxygenases, cyclooxygenases, and cytochrome P450s, and can be converted to a complex mixture of oxygenated products as a result of lipid peroxidation. The initial products in these reactions are hydroperoxyeicosatetraenoic acids (HpETEs) and hydroxyeicosatetraenoic acids (HETEs). Oxoeicosatetraenoic acids (oxo-ETEs) can be formed by the actions of various dehydrogenases on HETEs or by dehydration of HpETEs. Although a large number of different HETEs and oxo-ETEs have been identified, this review will focus principally on 5-oxo-ETE, 5S-HETE, 12S-HETE, and 15S-HETE. Other related arachidonic acid metabolites will also be discussed in less detail. 5-Oxo-ETE is synthesized by oxidation of the 5-lipoxygenase product 5S-HETE by the selective enzyme, 5-hydroxyeicosanoid dehydrogenase. It actions are mediated by the selective OXE receptor, which is highly expressed on eosinophils, suggesting that it may be important in eosinophilic diseases such as asthma. 5-Oxo-ETE also appears to stimulate tumor cell proliferation and may also be involved in cancer. Highly selective and potent OXE receptor antagonists have recently become available and could help to clarify its pathophysiological role. The 12-lipoxygenase product 12S-HETE acts by the GPR31 receptor and promotes tumor cell proliferation and metastasis and could therefore be a promising target in cancer therapy. It may also be involved as a proinflammatory mediator in diabetes. In contrast, 15S-HETE may have a protective effect in cancer. In addition to GPCRs, higher concentration of HETEs and oxo-ETEs can activate peroxisome proliferator-activated receptors (PPARs) and could potentially regulate a variety of processes by this mechanism. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Platelet 12-LOX is essential for FcγRIIa-mediated platelet activation

Platelets are essential in maintaining hemostasis following inflammation or injury to the vasculature. Dysregulated platelet activity often results in thrombotic complications leading to myocardial infarction and stroke. Activation of the FcγRIIa receptor leads to immune-mediated thrombosis, which is often life threatening in patients undergoing heparin-induced thrombocytopenia or sepsis. Inhibiting FcγRIIa-mediated activation in platelets has been shown to limit thrombosis and is the principal target for prevention of immune-mediated platelet activation. In this study, we show for the first time that platelet 12(S)-lipoxygenase (12-LOX), a highly expressed oxylipin-producing enzyme in the human platelet, is an essential component of FcγRIIa-mediated thrombosis. Pharmacologic inhibition of 12-LOX in human platelets resulted in significant attenuation of FcγRIIa-mediated aggregation. Platelet 12-LOX was shown to be essential for FcγRIIa-induced phospholipase Cγ2 activity leading to activation of calcium mobilization, Rap1 and protein kinase C activation, and subsequent activation of the integrin αIIbβ3. Additionally, platelets from transgenic mice expressing human FcγRIIa but deficient in platelet 12-LOX, failed to form normal platelet aggregates and exhibited deficiencies in Rap1 and αIIbβ3 activation. These results support an essential role for 12-LOX in regulating FcγRIIa-mediated platelet function and identifies 12-LOX as a potential therapeutic target to limit immune-mediated thrombosis.

Liquid chromatography-tandem mass spectrometry for simultaneous measurement of thromboxane B2 and 12(S)-hydroxyeicosatetraenoic acid in serum

Arachidonic acid (AA) is metabolized in human platelets by two main pathways: via cyclooxygenase (COX-1) to prostaglandins and thromboxane (TX)A2 and via 12-lipoxygenase (12-LOX) to 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE). While COX products are known to regulate platelet reactivity, the role of 12-LOX metabolites is still controversial. To better understand the platelet enzymatic pathways, we developed a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the simultaneous measurement of both platelet metabolites in human serum. After the addition of deuterated d4-TXB2 and d8-12(S)-HETE as internal standards and the solid-phase extraction of serum samples, analytes were resolved using reversed-phase C18 column and quantified using negative ion electrospray ionization-tandem mass spectrometry. Intra and interassay imprecisions were less than 10% for both analytes. The lower limits of quantification were 0.244ng/ml and 0.976ng/ml for TXB2 and 12(S)-HETE, respectively. This method was applied to measure platelet metabolites in healthy subjects (n=35). LC-MS/MS allows rapid, simultaneous, sensitive and accurate quantification of both platelet AA products in human serum with a small sample volume required and a minimal sample preparation.

Analysis, physiological and clinical significance of 12-HETE: a neglected platelet-derived 12-lipoxygenase product

While the importance of cyclooxygenase (COX) in platelet function has been amply elucidated, the identification of the role of 12-lipoxygenase (12-LOX) and of its stable metabolite, 12-hydroxyeicosatretraenoic acid (12-HETE), has not been clarified as yet. Many studies have analysed the implications of 12-LOX products in different pathological disorders but the information obtained from these works is controversial. Several analytical methods have been developed over the years to simultaneously detect eicosanoids, and specifically 12-HETE, in different biological matrices, essentially enzyme-linked immunosorbent assays (ELISA), radioimmunoassays (RIA), high performance liquid chromatography (HPLC) and mass spectrometry coupled with both gas and liquid chromatography methods (GC- and LC-MS). This review is aimed at summarizing the up to now known physiological and clinical features of 12-HETE together with the analytical methods used for its determination, focusing on the critical issues regarding its measurement.

The obesity-inflammation-eicosanoid axis in breast cancer

Inflammation of the adipose tissues occurs in association with obesity. This inflammatory process leads to the induction of cyclooxygenase-2 (COX-2) expression and a consequent elevation in prostaglandin (PG) production, which, together with proinflammatory cytokines, induce aromatase expression and estrogen synthesis. Infiltrating macrophages support the growth of breast epithelial cells and vascular endothelial cells by producing a milieu of cytokines and growth factors. This scenario creates a microenvironment favorable to breast cancer growth and invasion. The eicosanoids promote further development and growth of breast cancers indirectly by the induction of aromatase, particularly in estrogen positive breast cancers, or by direct stimulatory effect of PGE2 and lipoxygenase (LOX) products on the more aggressive, estrogen-independent tumors. Beyond this, the local production of estrogens and proinflammatory cytokines which occurs in association with breast adipose tissue inflammation, and consequent activation of the estrogen receptor and nuclear factor-κB, provides a mechanism by which breast cancers develop resistance to selective estrogen receptor modulation and aromatase inhibitor therapy. The obesity-inflammation-eicosanoid axis in breast cancer does offer a therapeutic target for the prevention of relapse in breast cancer by improving the efficacy of antiaromatase therapy using COX/LOX inhibitors; however, careful consideration of menopausal status and obesity in patients is warranted.

The concentration of 12-lipoxygenase in platelet rich plasma as an indication of cancer of the prostate

Aim of the study

The aim of this study was to determine whether measuring concentrations of 12-LOX in platelet-rich plasma patients can:

Differentiate between the group of patients with prostate cancer and healthy men.

Correlate the degree of severity of the disease and the concentration of the enzyme.

Material and methods

The study group comprised 88 men (40–88 years), including 54 patients diagnosed with prostate cancer. The population was divided into 4 groups:

group 1 (22 men, aged 55–84 years) –with a negative biopsy,

group 2 (36 men, aged 54–88 years) – with a positive biopsy result,

group 3 (18 participants aged 58–83) – patients with cancer metastatic disease,

group 4 of healthy men (12 people aged 40–66 years) – biopsy was not performed.

Routine PSA, morphology and CRP analysis were performed and platelet rich plasma was used for 12(S)LOX determination using an ELISA kit.

Results

There was a weak (r = 0.0487) positive correlation between the number of blood platelets and plasma 12(S)LOX.

An inverse relationship between 12(S)LOX and Gleason grade was found.

Heterogeneity of 12(S)LOX in the group with prostate cancer metastatic disease may suggest differences in the response to the treatment carried out.

There were no statistically significant differences in concentrations of 12(S)LOX in different groups of patients.

Conclusions

Our results suggest that 12(S)LOX is relevant in prostate cancer; however, further study should include a larger, more select group of men with prostate cancer.

Platelet-type 12-lipoxygenase induces MMP9 expression and cellular invasion via activation of PI3K/Akt/NF-κB

Prostate cancer is the most frequently diagnosed cancer and the second leading cause of death in males in the United States. Using human prostate cancer specimens, the authors have previously shown that elevated expression levels of 12-lipoxygenase (12-LOX) occurred more frequently in advanced stage, high-grade prostate cancer, suggesting that 12-LOX expression is associated with carcinoma progression and invasion. Previous reports from their group and others have shown that 12-LOX is a positive modulator of invasion and metastasis; however, the mechanism remains unclear. In this work, a new link between 12-LOX and the matrix metalloproteinase 9 (MMP9) in prostate cancer angiogenesis is reported. This study demonstrated that overexpression of 12-LOX in prostate cancer PC-3 cells resulted in elevated expression of MMP9 mRNA, protein and secretion. Exogenous addition of 12(S)-hydroxy eicosatetraenoic acid, the sole and stable end product of arachidonic acid metabolism by 12-LOX, is able to increase MMP9 expression in wild-type PC-3 cells. Furthermore, using pharmacological and genetic inhibition approaches, it was found that 12-LOX activates phosphoinositol 3 kinase (PI3K)/Akt, which results in nuclear factor-kappa B (NF-κB)-driven MMP9 expression, ensuing in enhanced chemoattraction of endothelial cells. Specific inhibitors of 12-LOX, PI3K or NF-κB inhibited MMP9 expression in 12-LOX-expressing PC-3 cells and resulted in the blockade of the migratory ability of endothelial cells. In summary, the authors have identified a new pathway by which overexpression of 12-LOX in prostate cancer cells leads to augmented production of MMP9 via activation of PI3K/Akt/NF-κB signaling. The role of 12-LOX-mediated MMP9 secretion in endothelial cell migration may account for the proangiogenic function of 12-LOX in prostate cancer.

Non-synonymous polymorphism (Gln261Arg) of 12-lipoxygenase in colorectal and thyroid cancers

12-lipoxygenase (12-LOX) pathway which produces 12-HETE and hepoxiline HXA3 and HXB3, and induces production of reactive oxygen species and inflammation is increasingly being implicated in variety of cancers, including those of colorectal and thyroid cancers. Hence, we examined whether the functional polymorphism of 12-LOX (mRNA A835G; Protein Gln261Arg) has any association with human colorectal and thyroid cancers. In this communication, we report that the mutation is linked to colorectal cancer and thyroid cancers. Further, we also observed that the heterozygous mutant (AG) is more prevalent in females than in males. Frequencies of AA, AG and GG, respectively were 62.5, 36.2 and 1.3 % in controls, 36.5, 61.5 and 2.0 % in colorectal cancer cases and 35.6, 62.4 and 2.0 % in thyroid cancer cases. The results obtained suggested a significant association of the heterogenous variant (AG) with the cancers. Relative risk of the cancers with the presence of the AG variant was found to be 2.9 and 4.0 for colorectal and thyroid cancers, respectively. However, the association of the variant (AG) was significant only in male colorectal cancer patients but not in female patients. On the other hand, prevalence of the AG variant is significantly higher in control females than in male control subjects. To the best of our knowledge, this is the first study that links the 12-LOX gene polymorphism with thyroid cancer and reveals a gender bias in the prevalence of the polymorphic variants in controls and colorectal cancer patients.

Targeting 20-HETE producing enzymes in cancer - rationale, pharmacology, and clinical potential

Studies demonstrate that lipid mediator 20-Hydroxyeicosatetraenoic acid (20-HETE) synthesis and signaling are associated with the growth of cancer cells in vitro and in vivo. Stable 20-HETE agonists promote the proliferation of cancer cells, whereas selective inhibitors of the 20-HETE-producing enzymes of the Cytochrome (CYP450)4A and CYP4F families can block the proliferation of glioblastoma, prostate, renal cell carcinoma, and breast cancer cell lines. A recent observation that the expression of CYP4A/4F genes was markedly elevated in thyroid, breast, colon, and ovarian cancer further highlights the significance of 20-HETE-producing enzymes in the progression of different types of human cancer. These findings provide the rationale for targeting 20-HETE-producing enzymes in human cancers and set the basis for the development of novel therapeutic strategies for anticancer treatment.

Radiosensitivity of human prostate cancer cells can be modulated by inhibition of 12-lipoxygenase

Nearly 30% of prostate cancer (PCa) patients treated with potentially curative doses relapse at the sites of irradiation. How some tumor cells acquire radioresistance is poorly understood. The platelet-type 12-lipoxygenases (12-LOX)-mediated arachidonic acid metabolism is important in PCa progression. Here we show that 12-LOX confers radioresistance upon PCa cells. Treatment with 12-LOX inhibitors baicalein or BMD122 sensitizes PCa cells to radiation, without radiosensitizing normal cells. 12-LOX inhibitors and radiation, when combined, have super additive or synergistic inhibitory effects on the colony formation of both androgen-dependent LNCaP and androgen-independent PC-3 PCa cells. In vivo, the combination therapy significantly reduced tumor growth.

Gan-Lu-Yin Inhibits Proliferation and Migration of Murine WEHI-3 Leukemia Cells and Tumor Growth in BALB/C Allograft Tumor Model

The aim of this study was to explore the antitumor effect of Gan-Lu-Yin (GLY), a traditional Chinese herbal formula, on leukemia. Ethanolic extract of GLY was applied to evaluate its regulatory mechanisms in proliferation, migration, and differentiation of WEHI-3 leukemic cells as well as antitumor effect on BALB/c mice model. The results showed that GLY markedly reduced cell proliferation and migration with induced differentiation of WEHI-3 cells. The expression level of phosphorylated FAK, Akt, ERK1/2, and Rb was decreased p21 expression while level was increased in WEHI-3 treated with GLY. The results of cell cycle analysis revealed that GLY treatment could markedly induce G1 phase arrest and decrease cell population in S phase. Moreover, experimental results demonstrated that GLY decreased the protein expression and enzyme activity of MMP-2 and MMP-9. GLY treatment also reduced WEHI-3 leukemic infiltration in liver and spleen and tumor growth in animal model. Accordingly, GLY demonstrated an inhibitory effect on tumor growth with a regulatory mechanism partially through inhibiting FAK, Akt, and ERK expression in WEHI-3 cells. GLY may provide a promising antileukemic approach in the clinical application.

Inhibiting delta-6 desaturase activity suppresses tumor growth in mice

Recent studies have shown that a tumor-supportive microenvironment is characterized by high levels of pro-inflammatory and pro-angiogenic eicosanoids derived from omega-6 (n−6) arachidonic acid (AA). Although the metabolic pathways (COX, LOX, and P450) that generate these n−6 AA eicosanoids have been targeted, the role of endogenous AA production in tumorigenesis remains unexplored. Delta-6 desaturase (D6D) is the rate-limiting enzyme responsible for the synthesis of n−6 AA and increased D6D activity can lead to enhanced n−6 AA production. Here, we show that D6D activity is upregulated during melanoma and lung tumor growth and that suppressing D6D activity, either by RNAi knockdown or a specific D6D inhibitor, dramatically reduces tumor growth. Accordingly, the content of AA and AA-derived tumor-promoting metabolites is significantly decreased. Angiogenesis and inflammatory status are also reduced. These results identify D6D as a key factor for tumor growth and as a potential target for cancer therapy and prevention.

Following experimental stroke, the recovering brain is vulnerable to lipoxygenase-dependent semaphorin signaling

Recovery from stroke is limited, in part, by an inhibitory environment in the postischemic brain, but factors preventing successful remodeling are not well known. Using cultured cortical neurons from mice, brain endothelial cells, and a mouse model of ischemic stroke, we show that signaling from the axon guidance molecule Sema3A via eicosanoid second messengers can contribute to this inhibitory environment. Either 90 nM recombinant Sema3A, or the 12/15-lipoxygenase (12/15-LOX) metabolites 12-HETE and 12-HPETE at 300 nM, block axon extension in neurons compared to solvent controls, and decrease tube formation in endothelial cells. The Sema3A effect is reversed by inhibiting 12/15-LOX, and neurons derived from 12/15-LOX-knockout mice are insensitive to Sema3A. Following middle cerebral artery occlusion to induce stroke in mice, immunohistochemistry shows both Sema3A and 12/15-LOX are increased in the cortex up to 2 wk. To determine whether a Sema3A-dependent damage pathway is activated following ischemia, we injected recombinant Sema3A into the striatum. Sema3A alone did not cause injury in normal brains. But when injected into postischemic brains, Sema3A increased cortical damage by 79%, and again, this effect was reversed by 12/15-LOX inhibition. Our findings suggest that blocking the semaphorin pathway should be investigated as a therapeutic strategy to improve stroke recovery.

Synthesis and biological evaluation of N-aryl-4-aryl-1,3-thiazole-2-amine derivatives as direct 5-lipoxygenase inhibitors

Biological evaluation of N-aryl-4-aryl-1,3-thiazole-2-amine derivatives was examined for anti-inflammatory activity in in vitro and in vivo assays. The thiazole compounds showed direct inhibition of 5-lipoxygenase (LOX) that is a key enzyme of leukotrienes synthesis and involved in the inflammation-related diseases, including asthma and rheumatoid arthritis. To optimize biological activity, we synthesized 1,3-thiazole-2-amine derivatives and investigated for structure and activity relationship. Especially, N-(3,5-dimethylphenyl)-4-(4-chlorophenyl)-1,3-thiazole-2-amine was shown to have a potent anti-inflammatory activity as a 5-LOX inhibitor.

Cyclooxygenases and lipoxygenases in cancer

Cancer initiation and progression are multistep events that require cell proliferation, migration, extravasation to the blood or lymphatic vessels, arrest to the metastatic site, and ultimately secondary growth. Tumor cell functions at both primary or secondary sites are controlled by many different factors, including growth factors and their receptors, chemokines, nuclear receptors, cell-cell interactions, cell-matrix interactions, as well as oxygenated metabolites of arachidonic acid. The observation that cyclooxygenases and lipoxygenases and their arachidonic acid-derived eicosanoid products (prostanoids and HETEs) are expressed and produced by tumor cells, together with the finding that these enzymes can regulate cell growth, survival, migration, and invasion, has prompted investigators to analyze the roles of these enzymes in cancer progression. In this review, we focus on the contribution of cyclooxygenase- and lipoxygenase-derived eicosanoids to tumor cell function in vitro and in vivo and discuss hope and tribulations of targeting these enzymes for cancer prevention and treatment.

Up-regulation of BLT2 is critical for the survival of bladder cancer cells

The incidence rates of urinary bladder cancer continue to rise yearly, and thus new therapeutic approaches and early diagnostic markers for bladder cancer are urgently needed. Thus, identifying the key mediators and molecular mechanisms responsible for the survival of bladder cancer has valuable implications for the development of therapy. In this study, the role of BLT2, a receptor for leukotriene B((4)) (LTB((4))) and 12(S)-hydroxyeicosatetraenoic acid (HETE), in the survival of bladder cancer 253J-BV cells was investigated. We found that the expression of BLT2 is highly elevated in bladder cancer cells. Also, we observed that blockade of BLT2 with an antagonist or BLT2 siRNA resulted in cell cycle arrest and apoptotic cell death, suggesting a role of BLT2 in the survival of human bladder cancer 253J-BV cells. Further experiments aimed at elucidating the mechanism by which BLT2 mediates survival revealed that enhanced level of reactive oxygen species (ROS) are generated via a BLT2-dependent up-regulation of NADPH oxidase members NOX1 and NOX4. Additionally, we observed that inhibition of ROS generation by either NOX1/4 siRNAs or treatment with an ROS-scavenging agent results in apoptotic cell death in 253J-BV bladder cancer cells. These results demonstrated that a 'BLT2-NOX1/4-ROS' cascade plays a role in the survival of this aggressive bladder cancer cells, thus pointing to BLT2 as a potential target for anti-bladder cancer therapy.

cPLA(2)α gene activation by IL-1β is dependent on an upstream kinase pathway, enzymatic activation and downstream 15-lipoxygenase activity: a positive feedback loop

Cytosolic phospholipase A(2)α (cPLA(2)α) is the most widely studied member of the Group IV PLA(2) family. The enzyme is Ca(2+)-dependent with specificity for phospholipid substrates containing arachidonic acid. As the pinnacle of the arachidonic acid pathway, cPLA(2)α has a primary role in the biosynthesis of a diverse family of eicosanoid metabolites, with potent physiological, inflammatory and pathological consequences. cPLA(2)α activity is regulated by pro-inflammatory stimuli through pathways involving increased intracellular Ca(2+) levels, phosphorylation coupled to increased enzymatic activity and de novo gene transcription. This study addresses the signal transduction pathways for protein phosphorylation and gene induction following IL-1β stimulation in human fetal lung fibroblasts. Our results utilizing both inhibitors and kinase-deficient cells demonstrate that cPLA(2)α is phosphorylated within 10min of IL-1β treatment, an event requiring p38 MAPK as well as the upstream kinase, MKK3/MKK6. Inhibition of p38 MAPK also blocks the phosphorylation of a downstream, nuclear kinase, MSK-1. Our results further demonstrate that the activities of both cPLA(2)α and a downstream lipoxygenase (15-LOX2) are required for IL-1β-dependent induction of cPLA(2)α mRNA expression. Overall, these data support an MKK3/MKK6→p38 MAPK→MSK-1→cPLA(2)α→15-LOX2-dependent, positive feedback loop where a protein's enzymatic activity is required to regulate its own gene induction by a pro-inflammatory stimulus.

Identification of the orphan G protein-coupled receptor GPR31 as a receptor for 12-(S)-hydroxyeicosatetraenoic acid

Hydroxy fatty acids are critical lipid mediators involved in various pathophysiologic functions. We cloned and identified GPR31, a plasma membrane orphan G protein-coupled receptor that displays high affinity for the human 12-lipoxygenase-derived product 12-(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE). Thus, GPR31 is named 12-(S)-HETE receptor (12-HETER) in this study. The cloned 12-HETER demonstrated high affinity binding for 12-(S)-[(3)H]HETE (K(d) = 4.8 ± 0.12 nm). Also, 12-(S)-HETE efficiently and selectively stimulated GTPγS coupling in the membranes of 12-HETER-transfected cells (EC(50) = 0.28 ± 1.26 nm). Activating GTPγS coupling with 12-(S)-HETE proved to be both regio- and stereospecific. Also, 12-(S)-HETE/12-HETER interactions lead to activation of ERK1/2, MEK, and NFκB. Moreover, knocking down 12-HRTER specifically inhibited 12-(S)-HETE-stimulated cell invasion. Thus, 12-HETER represents the first identified high affinity receptor for the 12-(S)-HETE hydroxyl fatty acids.

Baicalein potently suppresses angiogenesis induced by vascular endothelial growth factor through the p53/Rb signaling pathway leading to G1/S cell cycle arrest

Vascular endothelial growth factor (VEGF) is a key modulator of angiogenesis. Recent studies have shown that VEGF stimulates endothelial cell growth and modulates the cell cycle by reactivation of G0 cells and by reducing the duration of the G1 phase. This study examined the effect of baicalein, a well-known flavonoid, on VEGF-induced angiogenesis and further investigated the role of cell cycle regulators on the antiangiogenic effects of baicalein. Classic in vivo and in vitro models, including a rat aortic ring model, a wound healing model and a tube formation model were used to evaluate angiogenesis in vivo and in vitro. Baicalein exerted marked inhibition of angiogenesis, significantly inhibited migration of human umbilical vein endothelial cells (HUVECs), suppressed tube formation and reduced new blood vessel growth inducted by VEGF. Baicalein reduced phosphorylation of VEGF receptor 2 and extracellular signal-regulated protein kinase, two major signaling elements modulating endothelial cell proliferation. Baicalein also inhibited colony formation by HUVECs, further confirming the suppression of proliferation. Cell cycle analysis demonstrated that baicalein-treated HUVECs were arrested in the G1/S phase. Baicalein also induced a decline in the expression of G1-related proteins that normally promote transition from the G1 phase to the S phase, including cyclin D, cyclin E, cdk-4, cdk-6 and p-Rb. In contrast, several proteins upstream of cdks and cyclins, including p16, p21, p27 and p53, were up-regulated by baicalein, indicating that baicalein may inhibit angiogenesis, at least in part, by effects on the p53/Rb signaling pathway. Baicalein could exert antitumor effects by inhibiting VEGF-induced angiogenesis and endothelial cell proliferation.

Baicalein significantly protects human retinal pigment epithelium cells against H₂O₂-induced oxidative stress by scavenging reactive oxygen species and downregulating the expression of matrix metalloproteinase-9 and vascular endothelial growth factor

PURPOSE

Age-related macular degeneration is a leading cause of blindness in the elderly. At a later stage, neovascular or exudative age-related macular degeneration can lead to severe central vision loss that is related to aging-associated cumulative oxidative stress of the human retinal pigment epithelium (hRPE) cells. Early prevention with antioxidants is mandatory. The aim of this study was to determine whether and how baicalein can act as an antioxidant.

METHODS

The methods used included lactate dehydrogenase, 2′,7′-dichloro-fluorescein diacetate, or enzyme-linked immunosorbent assay to measure cell viability, oxygen free radical levels, or the levels of vascular endothelial growth factor (VEGF)/matrix metalloproteinase-9 (MMP-9), respectively.

RESULTS

H₂O₂ dose-dependently reduced the cell viability of hRPE cells. This negative effect was dose-dependently (with a lower effect at 20µM) and significantly counteracted by pretreatment with baicalein (50µM). Treatment with H₂O₂ significantly stimulated the formation of oxygen free radicals. This increase was dose-dependently and significantly blunted by baicalein. Further, treatment with a sublethal dose of H₂O₂ was associated with an upregulation in the levels of VEGF and MMP-9. The increases in these proteins were also dose-dependently (with a lower effect at 20µM) and significantly (50µM) blunted by pretreatment with baicalein.

CONCLUSION

This study supports an antioxidative role for baicalein whereby it protects hRPE cells against H₂O₂-induced oxidative stress by downregulating the levels of VEGF and MMP-9, which are increased by H₂O₂.

Increased expression and activity of 12-lipoxygenase in oxygen-induced ischemic retinopathy and proliferative diabetic retinopathy: implications in retinal neovascularization

OBJECTIVE

Arachidonic acid is metabolized by 12-lipoxygenase (12-LOX) to 12-hydroxyeicosatetraenoic acid (12-HETE) and has an important role in the regulation of angiogenesis and endothelial cell proliferation and migration. The goal of this study was to investigate whether 12-LOX plays a role in retinal neovascularization (NV).

RESEARCH DESIGN AND METHODS

Experiments were performed using retinas from a murine model of oxygen-induced ischemic retinopathy (OIR) that was treated with and without the LOX pathway inhibitor, baicalein, or lacking 12-LOX. We also analyzed vitreous samples from patients with and without proliferative diabetic retinopathy (PDR). Western blotting and RT-PCR were used to assess the expression of 12-LOX, vascular endothelial growth factor (VEGF), and pigment epithelium-derived factor (PEDF). Liquid chromatography-mass spectrometry was used to assess the amounts of HETEs in the murine retina and human vitreous samples. The effects of 12-HETE on VEGF and PEDF expression were evaluated in Müller cells (rMCs), primary mouse retinal pigment epithelial cells, and astrocytes.

RESULTS

Retinal NV during OIR was associated with increased 12-LOX expression and 12-, 15-, and 5-HETE production. The amounts of HETEs also were significantly higher in the vitreous of diabetic patients with PDR. Retinal NV was markedly abrogated in mice treated with baicalein or mice lacking 12-LOX. This was associated with decreased VEGF expression and restoration of PEDF levels. PEDF expression was reduced in 12-HETE-treated rMCs, astrocytes, and the retinal pigment epithelium. Only rMCs and astrocytes showed increased VEGF expression by 12-HETE.

CONCLUSIONS

12-LOX and its product HETE are important regulators of retinal NV through modulation of VEGF and PEDF expression and could provide a new therapeutic target to prevent and treat ischemic retinopathy.

Association of a functional polymorphism (Gln261Arg) in 12-lipoxygenase with breast cancer

The overexpression of arachidonyl lipoxygenase-12 (ALOX12) in breast cancer has been reported. Hence, we examined whether a non-synonymous polymorphism of ALOX12 (mRNA, A835G; Gln261Arg) is associated with breast cancer in females. The polymorphism was detected in genomic DNA by PCR-RFLP. The association between the A835G polymorphism and breast cancer risk was measured by odds ratio (OR) with 95% confidence intervals (CIs) using Fisher's exact test, and differences were considered significant at p<0.05. The frequencies of AA (wild-type), GG (homozygous variant) and AG (heterozygous variant) were 59.5, 0.9 and 39.6% in the controls, and 39.3, 2.5 and 58.2% in the breast cancer cases, respectively. The frequency of the AG genotype was higher in the patients compared to the controls (p<0.0014). The frequency of the GG variant was 2.5 and 0.9% in the cancer subjects and controls, respectively. The relative risk of breast cancer was 2 times greater (OR=2.227) at 95% CI when compared to the relative risk of the heterozygous variant. For the GG genotype, the risk was 4 times greater (OR=4.125) at 95% CI than that of the controls, suggesting a positive association of the AG genotype with the occurrence of breast cancer. The frequencies of the polymorphism were different in different populations. The Arg/Gln and Arg/Arg variants were associated with an increased risk of breast cancer, and the frequencies of the variants differed considerably among various populations. The identification of a gene with links to breast cancer may impact screening, diagnosis and drug development.

Regulation of endothelial cell functions by basement membrane- and arachidonic acid-derived products

Angiogenesis, the formation of new blood vessels from preexisting vasculature, is required for normal physiological as well as pathological events. The angiogenic process requires endothelial cells to proliferate, migrate, and undergo tubulogenesis. These multistep processes necessitate secretion of pro-angiogenic growth factors, activation of specific intracellular signaling, and interaction of endothelial cells with basement membrane (BM) extracellular matrix components. The generation and release of angiogenic molecules are highly regulated and are influenced by numerous factors, including BM-derived fragments, proteolytic enzymes, as well as metabolites of arachidonic acid (AA). The interactions between these key modulators of angiogenesis is extremely complex, as AA metabolites can regulate the synthesis of soluble angiogenic factors, BM components, as well as enzymes capable of cleaving BM components, which result in the generation of pro- and/or anti-angiogenic products. Furthermore, some BM-derived fragments can alter the expression of AA-converting enzymes and consequently the synthesis of angiogenic factors. In this review we describe the relationship between BM components and AA metabolites with respect to the regulation of endothelial cell functions in health and disease.