Inhibition of arachidonate 5-lipoxygenase triggers massive apoptosis in human prostate cancer cells

Effect of a low-fat fish oil diet on proinflammatory eicosanoids and cell-cycle progression score in men undergoing radical prostatectomy

We previously reported that a 4- to 6-week low-fat fish oil (LFFO) diet did not affect serum insulin-like growth factor (IGF)-1 levels (primary outcome) but resulted in lower omega-6 to omega-3 fatty acid ratios in prostate tissue and lower prostate cancer proliferation (Ki67) as compared with a Western diet. In this post hoc analysis, the effect of the LFFO intervention on serum pro-inflammatory eicosanoids, leukotriene B4 (LTB4) and 15-S-hydroxyeicosatetraenoic acid [15(S)-HETE], and the cell-cycle progression (CCP) score were investigated. Serum fatty acids and eicosanoids were measured by gas chromatography and ELISA. CCP score was determined by quantitative real-time reverse transcriptase PCR (RT-PCR). Associations between serum eicosanoids, Ki67, and CCP score were evaluated using partial correlation analyses. BLT1 (LTB4 receptor) expression was determined in prostate cancer cell lines and prostatectomy specimens. Serum omega-6 fatty acids and 15(S)-HETE levels were significantly reduced, and serum omega-3 levels were increased in the LFFO group relative to the Western diet group, whereas there was no change in LTB4 levels. The CCP score was significantly lower in the LFFO compared with the Western diet group. The 15(S)-HETE change correlated with tissue Ki67 (R = 0.48; P < 0.01) but not with CCP score. The LTB4 change correlated with the CCP score (r = 0.4; P = 0.02) but not with Ki67. The LTB4 receptor BLT1 was detected in prostate cancer cell lines and human prostate cancer specimens. In conclusion, an LFFO diet resulted in decreased 15(S)-HETE levels and lower CCP score relative to a Western diet. Further studies are warranted to determine whether the LFFO diet antiproliferative effects are mediated through the LTB4/BLT1 and 15(S)-HETE pathways.

Metabolic and protein interaction sub-networks controlling the proliferation rate of cancer cells and their impact on patient survival

Cancer cells can have a broad scope of proliferation rates. Here we aim to identify the molecular mechanisms that allow some cancer cell lines to grow up to 4 times faster than other cell lines. The correlation of gene expression profiles with the growth rate in 60 different cell lines has been analyzed using several genome-scale biological networks and new algorithms. New possible regulatory feedback loops have been suggested and the known roles of several cell cycle related transcription factors have been confirmed. Over 100 growth-correlated metabolic sub-networks have been identified, suggesting a key role of simultaneous lipid synthesis and degradation in the energy supply of the cancer cells growth. Many metabolic sub-networks involved in cell line proliferation appeared also to correlate negatively with the survival expectancy of colon cancer patients.

The eosinophil chemoattractant 5-oxo-ETE and the OXE receptor

5-Oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid) is formed from the 5-lipoxygenase product 5-HETE (5S-hydroxy-6,8,11,14-eicosatetraenoic acid) by 5-hydroxyeicosanoid dehydrogenase (5-HEDH). The cofactor NADP(+) is a limiting factor in the synthesis of 5-oxo-ETE because of its low concentrations in unperturbed cells. Activation of the respiratory burst in phagocytic cells, oxidative stress, and cell death all dramatically elevate both intracellular NADP(+) levels and 5-oxo-ETE synthesis. 5-HEDH is widely expressed in inflammatory, structural, and tumor cells. Cells devoid of 5-lipoxygenase can synthesize 5-oxo-ETE by transcellular biosynthesis using inflammatory cell-derived 5-HETE. 5-Oxo-ETE is a chemoattractant for neutrophils, monocytes, and basophils and promotes the proliferation of tumor cells. However, its primary target appears to be the eosinophil, for which it is a highly potent chemoattractant. The actions of 5-oxo-ETE are mediated by the highly selective OXE receptor, which signals by activating various second messenger pathways through the release of the βγ-dimer from Gi/o proteins to which it is coupled. Because of its potent effects on eosinophils, 5-oxo-ETE may be an important mediator in asthma, and, because of its proliferative effects, may also contribute to tumor progression. Selective OXE receptor antagonists, which are currently under development, could be useful therapeutic agents in asthma and other allergic diseases.

Expression and function of OXE receptor, an eicosanoid receptor, in steroidogenic cells

Hormonal regulation of steroidogenesis involves arachidonic acid (AA) metabolism through the 5-lipoxygenase pathway. One of the products, 5-hydroperoxy-eicosatetraenoic acid (5-HpETE), acts as a modulator of the activity of the steroidogenic acute regulatory (StAR) protein promoter. Besides, an oxoeicosanoid receptor of the leukotriene receptor family named OXE-R is a membrane protein with high affinity and response to 5-HpETE, among other AA derivatives. The aim of our work was to elucidate whether this receptor may be involved in steroidogenesis. RT-PCR and western blot analysis demonstrated the presence of the mRNA and protein of the receptor in human H295R adrenocortical cells. The treatment of H295R or MA-10 cells (murine Leydig cell line) with 8Br-cAMP together with docosahexaenoic acid (DHA, an antagonist of the receptor) partially reduced StAR induction and steroidogenesis. On the contrary, 5-oxo-ETE - the prototypical agonist, with higher affinity and potency on the receptor - increased cAMP-dependent steroid production, StAR mRNA and protein levels. These results lead us to conclude that AA might modulate StAR induction and steroidogenesis, at least in part, through 5-HpETE production and activation of a membrane receptor, such as the OXE-R.

OXER1, a G protein-coupled oxoeicosatetraenoid receptor, mediates the survival-promoting effects of arachidonate 5-lipoxygenase in prostate cancer cells

Inhibition of 5-Lox induces apoptosis in prostate cancer cells by inactivating PKCε which is prevented by 5-oxoETE, and activators of PKCε prevent 5-Lox inhibition-induced apoptosis, suggesting that 5-Lox metabolites exert survival signaling via PKCε. However, mechanisms by which 5-Lox metabolites activate PKCε are not understood yet. We found that prostate cancer cells express high levels of OXER1, a G protein-coupled 5-oxoETE receptor, which delivers signal by generating diacyl-glycerol through phospholipase C-beta. Interestingly, we found that U73122, an inhibitor of PLC-beta, interrupts the apoptosis-preventing effect of 5-oxoETE, and exogenous diacyl-glycerol effectively prevents 5-Lox inhibition-induced apoptosis, suggesting that 5-oxoETE signals via OXER1 to promote prostate cancer cell survival.

Index-based dietary patterns and the risk of prostate cancer in the NIH-AARP diet and health study

Few studies have investigated the relationship between overall diet and the risk of prostate cancer. We examined the association between 3 diet quality indices-the Healthy Eating Index-2005 (HEI-2005), Alternate Healthy Eating Index-2010 (AHEI-2010), and alternate Mediterranean diet score (aMED)-and prostate cancer risk. At baseline, dietary intake was assessed in a cohort of 293,464 US men in the National Institutes of Health (NIH)-AARP Diet and Health Study. Cox proportional hazards regression was used to estimate hazard ratios. Between 1995 and 2006, we ascertained 23,453 incident cases of prostate cancer, including 2,251 advanced cases and 428 fatal cases. Among men who reported a history of prostate-specific antigen testing, high HEI-2005 and AHEI-2010 scores were associated with lower risk of total prostate cancer (for the highest quintile compared with the lowest, hazard ratio (HR) = 0.92, 95% confidence interval (CI): 0.86, 0.98, P for trend = 0.01; and HR = 0.93, 95% CI: 0.88, 0.99, P for trend = 0.05, respectively). No significant association was observed between aMED score and total prostate cancer or between any of the indices and advanced or fatal prostate cancer, regardless of prostate-specific antigen testing status. In individual component analyses, the fish component of aMED and ω-3 fatty acids component of AHEI-2010 were inversely associated with fatal prostate cancer (HR = 0.79, 95% CI: 0.65, 0.96, and HR = 0.94, 95% CI: 0.90, 0.98, respectively).

Cancer-produced metabolites of 5-lipoxygenase induce tumor-evoked regulatory B cells via peroxisome proliferator-activated receptor α

Breast cancer cells facilitate distant metastasis through the induction of immunosuppressive regulatory B cells, designated tBregs. We report in this study that, to do this, breast cancer cells produce metabolites of the 5-lipoxygenase pathway such as leukotriene B4 to activate the peroxisome proliferator-activated receptor α (PPARα) in B cells. Inactivation of leukotriene B4 signaling or genetic deficiency of PPARα in B cells blocks the generation of tBregs and thereby abrogates lung metastasis in mice with established breast cancer. Thus, in addition to eliciting fatty acid oxidation and metabolic signals, PPARα initiates programs required for differentiation of tBregs. We propose that PPARα in B cells and/or tumor 5-lipoxygenase pathways represents new targets for pharmacological control of tBreg-mediated cancer escape.

Effects of flavocoxid, a dual inhibitor of COX and 5-lipoxygenase enzymes, on benign prostatic hyperplasia

BACKGROUND AND PURPOSE

Inflammation plays a key role in the development of benign prostatic hyperplasia (BPH). Eicosanoids derived from the COX and 5-lipoxygenase (5-LOX) pathways are elevated in the enlarging prostate. Flavocoxid is a novel flavonoid-based 'dual inhibitor' of the COX and 5-LOX enzymes. This study evaluated the effects of flavocoxid in experimental BPH.

EXPERIMENTAL APPROACH

Rats were treated daily with testosterone propionate (3 mg·kg(-1)  s.c.) or its vehicle for 14 days to induce BPH. Animals receiving testosterone were randomized to receive vehicle (1 mL·kg(-1) , i.p.) or flavocoxid (20 mg·kg(-1) , i.p.) for 14 days. Histological changes, eicosanoid content and mRNA and protein levels for apoptosis-related proteins and growth factors were assayed in prostate tissue. The effects of flavocoxid were also tested on human prostate carcinoma PC3 cells.

KEY RESULTS

Flavocoxid reduced prostate weight and hyperplasia, blunted inducible expression of COX-2 and 5-LOX as well as the increased production of PGE(2) and leukotriene B(4) (LTB(4) ), enhanced pro-apoptotic Bax and caspase-9 and decreased the anti-apoptotic Bcl-2 mRNA. Flavocoxid also reduced EGF and VEGF expression. In PC3 cells, flavocoxid stimulated apoptosis and inhibited growth factor expression. Flavocoxid-mediated induction of apoptosis was inhibited by the pan-caspase inhibitor, Z-VAD-FMK, in PC3 cells, suggesting an essential role of caspases in flavocoxid-mediated apoptosis during prostatic growth.

CONCLUSION AND IMPLICATIONS

Our results show that a 'dual inhibitor' of the COX and 5-LOX enzymes, such as flavocoxid, might represent a rational approach to reduce BPH through modulation of eicosanoid production and a caspase-induced apoptotic mechanism.

Lipoxygenase inhibitor MK886 potentiates TRAIL-induced apoptosis through CHOP- and p38 MAPK-mediated up-regulation of death receptor 5 in malignant glioma

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers specific apoptosis in tumor cells and is one of the most promising candidates for cancer gene therapy. However, resistance to TRAIL is one of the main impediments to use of TRAIL in cancer treatment. We showed previously that the lipoxygenase inhibitor MK886 in combination with TRAIL exhibits enhanced antitumor activities compared with each agent alone in human glioma cells. In this study, we elucidated the molecular mechanisms responsible for MK886-mediated sensitization to TRAIL-induced apoptosis. We found that MK886 sensitized glioma cells to TRAIL-induced apoptosis by upregulating the death receptor 5 (DR5) and that specific knockdown of DR5 attenuated cell death. The mechanisms underlying this sensitization involved activation of the MK886-induced p38 mitogen-activated protein kinase (MAPK) pathway and subsequent DR5 overexpression. However, treatment with a specific inhibitor or gene silencing of p38 MAPK abolished both the DR5 induction and the increase in apoptosis caused by TRAIL. Taken together, our findings indicate that the increased expression of DR5 in a p38 MAPK-dependent manner plays an important role in the sensitization of MK886 to TRAIL-induced apoptosis.

Lycopodine triggers apoptosis by modulating 5-lipoxygenase, and depolarizing mitochondrial membrane potential in androgen sensitive and refractory prostate cancer cells without modulating p53 activity: signaling cascade and drug-DNA interaction

When the prostate cancer cells become unresponsive to androgen therapy, resistance to chemotherapy becomes imminent, resulting in high mortality. To combat this situation, lycopodine, a pharmacologically important bioactive component derived from Lycopodium clavatum spores, was tested against hormone sensitive (LnCaP) and refractory (PC3) prostate cancer cells in vitro. This study aims to check if lycopodine has demonstrable anti-cancer effects and if it has, to find out the possible mechanism of its action. The MTT assay was performed to evaluate the cytotoxic effect. Depolarization of mitochondrial membrane potential, cell cycle, EGF receptor activity and apoptosis were recorded by FACS; profiles of different anti- and pro-apoptotic genes and their products were studied by semi-quantitative RT-PCR, indirect-ELISA, western blotting. Drug-DNA interaction was determined by CD spectroscopy. Administration of lycopodine down-regulated the expression of 5-lipoxygenase and the 5-oxo-ETE receptor (OXE receptor1) and EGF receptor, and caused up-regulation of cytochrome c with depolarization of mitochondrial inner membrane potential, without palpable change in p53 activity, resulting in apoptosis, cell arrest at G0/G1 stage and ultimately reduced proliferation of cancer cells; concomitantly, there was externalization of phosphotidyl serine residues. CD spectroscopic analysis revealed intercalating property of lycopodine with DNA molecule, implicating its ability to block cellular DNA synthesis. The overall results suggest that lycopodine is a promising candidate suitable for therapeutic use as an anti-cancer drug.

Wedelolactone, a medicinal plant-derived coumestan, induces caspase-dependent apoptosis in prostate cancer cells via downregulation of PKCε without inhibiting Akt

Emerging studies indicate that metabolism of arachidonic acid through the 5-lipoxygenase (5-Lox) pathway plays a critical role in the survival of prostate cancer cells raising the possibility that 5-Lox can be targeted for an effective therapy of prostate cancer. Wedelolactone (WDL), a medicinal plant-derived natural compound, is known to inhibit 5-Lox activity in neutrophils. However, its effect on apoptosis in prostate cancer cells has not been addressed. Thus, we tested the effects of WDL on human prostate cancer cells in vitro. We observed that WDL kills both androgen-sensitive as well as androgen-independent prostate cancer cells in a dose-dependent manner by dramatically inducing apoptosis. We also found that WDL-induced apoptosis in prostate cancer cells is dependent on c-Jun N-terminal Kinase (c-JNK) and caspase-3. Interestingly, WDL triggers apoptosis in prostate cancer cells via downregulation of protein kinase Cε (PKCε), but without inhibition of Akt. WDL does not affect the viability of normal prostate epithelial cells (PrEC) at doses that kill prostate cancer cells, and WDL-induced apoptosis is effectively prevented by 5-oxoETE, a metabolite of 5-Lox (but not by 15-oxoETE, a metabolite of 15-Lox), suggesting that the apoptosis-inducing effect of WDL in prostate cancer cells is mediated via inhibition of 5-Lox activity. These findings indicate that WDL selectivity induces caspase-dependent apoptosis in prostate cancer cells via a novel mechanism involving inhibition of PKCε without affecting Akt and suggest that WDL may emerge as a novel therapeutic agent against clinical prostate cancer in human.

Role of mitochondria in programmed cell death mediated by arachidonic acid-derived eicosanoids

Arachidonic acid-derived eicosanoids from cyclooxygenases, lipoxygenases, and cytochrome P450 are important lipid mediators involved in numerous homeostatic and pathophysiological processes. Most eicosanoids act primarily on their respective cell surface G-protein coupled receptors to elicit downstream signaling in an autocrine and paracrine fashion. Emerging evidence indicates that these hormones are also critical in apoptosis in a cell/tissue specific manner. In this review, we summarize the formation of eicosanoids and their roles as mediators in apoptosis, specifically on the roles of mitochondria in mediating these events and the signaling pathways involved. The biological relevance of eicosanoid-mediated apoptosis is also discussed.

Investigations of human platelet-type 12-lipoxygenase: role of lipoxygenase products in platelet activation

Human platelet-type 12-lipoxygenase (12-LOX) has recently been shown to play an important role in regulation of human platelet function by reacting with arachidonic acid (AA). However, a number of other fatty acids are present on the platelet surface that, when cleaved from the phospholipid, can be oxidized by 12-LOX. We sought to characterize the substrate specificity of 12-LOX against six essential fatty acids: AA, dihomo-γ-linolenic acid (DGLA), eicosapentaenoic acid (EPA), α-linolenic acid (ALA), eicosadienoic acid (EDA), and linoleic acid (LA). Three fatty acids were comparable substrates (AA, DGLA, and EPA), one was 5-fold slower (ALA), and two showed no reactivity with 12-LOX (EDA and LA). The bioactive lipid products resulting from 12-LOX oxidation of DGLA, 12-(S)-hydroperoxy-8Z,10E,14Z-eicosatrienoic acid [12(S)-HPETrE], and its reduced product, 12(S)-HETrE, resulted in significant attenuation of agonist-mediated platelet aggregation, granule secretion, αIIbβ3 activation, Rap1 activation, and clot retraction. Treatment with DGLA similarly inhibited PAR1-mediated platelet activation as well as platelet clot retraction. These observations are in surprising contrast to our recent work showing 12(S)-HETE is a prothrombotic bioactive lipid and support our hypothesis that the overall effect of 12-LOX oxidation of fatty acids in the platelet is dependent on the fatty acid substrates available at the platelet membrane.

Gauging the flexibility of the active site in soybean lipoxygenase-1 (SLO-1) through an atom-centered density matrix propagation (ADMP) treatment that facilitates the sampling of rare events

We present a computational methodology to sample rare events in large biological enzymes that may involve electronically polarizing, reactive processes. The approach includes simultaneous dynamical treatment of electronic and nuclear degrees of freedom, where contributions from the electronic portion are computed using hybrid density functional theory and the computational costs are reduced through a hybrid quantum mechanics/molecular mechanics (QM/MM) treatment. Thus, the paper involves a QM/MM dynamical treatment of rare events. The method is applied to probe the effect of the active site elements on the critical hydrogen transfer step in the soybean lipoxygenase-1 (SLO-1) catalyzed oxidation of linoleic acid. It is found that the dynamical fluctuations and associated flexibility of the active site are critical toward maintaining the electrostatics in the regime where the reactive process can occur smoothly. Physical constraints enforced to limit the active site flexibility are akin to mutations and, in the cases studied, have a detrimental effect on the electrostatic fluctuations, thus adversely affecting the hydrogen transfer process.

Arachidonic acid metabolism in human prostate cancer

The arachidonic acid pathway is important in the development and progression of numerous malignant diseases, including prostate cancer. To more fully evaluate the role of individual cyclooxygenases (COXs), lipoxygenases (LOXs) and their metabolites in prostate cancer, we measured mRNA and protein levels of COXs and LOXs and their arachidonate metabolites in androgen-dependent (LNCaP) and androgen-independent (PC-3 and DU145) prostate cancer cell lines, bone metastasis-derived MDA PCa 2a and MDA PCa 2b cell lines and their corresponding xenograft models, as well as core biopsy specimens of primary prostate cancer and nonneoplastic prostate tissue taken ex vivo after prostatectomy. Relatively high levels of COX-2 mRNA and its product PGE2 were observed only in PC-3 cells and their xenografts. By contrast, levels of the exogenous 12-LOX product 12-HETE were consistently higher in MDA PCa 2b and PC-3 cells and their corresponding xenograft tissues than were those in LNCaP cells. More strikingly, the mean endogenous level of 12-HETE was significantly higher in the primary prostate cancers than in the nonneoplastic prostate tissue (0.094 vs. 0.010 ng/mg protein, respectively; p=0.019). Our results suggest that LOX metabolites such as 12-HETE are critical in prostate cancer progression and that the LOX pathway may be a target for treating and preventing prostate cancer.

Microsomal Prostaglandin E2 Synthase-1

The prostanoids and leukotrienes (LTs) formed from arachidonic acid (AA) via the cyclooxygenase (COX)-1/2 and 5-lipoxygenase (5-LO) pathway, respectively, mediate inflammatory responses, chronic tissue remodelling, cancer, asthma and autoimmune disorders, but also possess homeostatic functions in the gastrointestinal tract, uterus, brain, kidney, vasculature and host defence. Based on the manifold functions of these eicosanoids, the clinical use of non-steroidal anti-inflammatory drugs (NSAIDs), a class of drugs that block formation of all prostanoids, is hampered by severe side-effects including gastrointestinal injury, renal irritations and cardiovascular risks. Therefore, anti-inflammatory agents interfering with eicosanoid biosynthesis require a well-balanced pharmacological profile to minimize these on-target side-effects. Current anti-inflammatory research aims at identifying compounds that can suppress the massive formation of pro-inflammatory prostaglandin (PG)E2 without affecting homeostatic PGE2 and PGI2 synthesis. The inducible microsomal prostaglandin E2 synthase-1 (mPGES-1) is one promising target enzyme. We will give an overview about the structure, regulation and function of mPGES-1 and then present novel inhibitors of mPGES-1 that may possess a promising pharmacological profile.

6'-Hydroxyoxosorbicillinol, a new lipoxygenase inhibitor and PGD2/LTB4 release suppressor from Penicillium sp

A new lipoxygenase inhibitor, 6'-hydroxyoxosorbicillinol (1, C(14) H(16)O(6)), was identified from a culture of Penicillium sp. A known compound, oxosorbicillinol (2, C(14)H(16)O(5)), was also isolated. Compound 1 showed an approximately 10 times greater inhibitory effect on soybean lipoxygenase (IC(50), 16 µM) than 2 (IC(50), 150 µM), and also showed prostaglandin D(2) (PGD(2)) and leucotriene B(4) (LTB(4)) release suppression activity (IC(50), 10 µM for PGD(2) and 100 µM for LTB(4)).

Oxidative stress and antioxidant defenses in pregnant women

OBJECTIVES

Oxidative stress (OS) is defined as an imbalance in the production of reactive oxygen species and the capacity of antioxidant defenses. The objective of this work was to investigate OS and antioxidant capacity in pregnant women.

METHODS

Parameters of the oxidative status and antioxidant capacity in serum and whole blood were evaluated in thirty-nine women with normal pregnancy.

RESULTS

The assessment of antioxidants indicated an increase in superoxide dismutase and catalase activities (P<0.05 and P<0.01) and a decrease in ascorbic acid levels and the total content of sulfhydryl (P<0.05 and P<0.001). Additionally, when the pro-oxidant system was investigated we found an increase (P<0.01) in malondialdehyde and no significant change (P>0.05) in protein carbonylation.

DISCUSSION

This study demonstrates that there is a change in the pro-oxidant and antioxidant defenses associated with body and circulation changes that are inherent to the pregnancy process.

Polyunsaturated fatty acid metabolism in prostate cancer

Polyunsaturated fatty acids (PUFA) play important roles in the normal physiology and in pathological states including inflammation and cancer. While much is known about the biosynthesis and biological activities of eicosanoids derived from ω6 PUFA, our understanding of the corresponding ω3 series lipid mediators is still rudimentary. The purpose of this review is not to offer a comprehensive summary of the literature on fatty acids in prostate cancer but rather to highlight some of the areas where key questions remain to be addressed. These include substrate preference and polymorphic variants of enzymes involved in the metabolism of PUFA, the relationship between de novo lipid synthesis and dietary lipid metabolism pathways, the contribution of cyclooxygenases and lipoxygenases as well as terminal synthases and prostanoid receptors in prostate cancer, and the potential role of PUFA in angiogenesis and cell surface receptor signaling.

Prevalence of 5-lipoxygenase expression in canine osteosarcoma and the effects of a dual 5-lipoxygenase/cyclooxygenase inhibitor on osteosarcoma cells in vitro and in vivo

Canine osteosarcoma is an insidious disease with few effective treatment modalities; therefore, use of pharmacologic intervention to improve mortality or morbidity is constantly sought. The use of cyclooxygenase enzyme inhibitors has been an area of interest with limited efficacy based on retrospective examination of tumor expression and in vivo cell proliferation models. Recently, examination of dual cyclooxygenase and 5-lipoxygenase inhibitors in human and canine oncology suggests that 5-lipoxygenase inhibitors may be an effective approach in vitro and during tumor induction in rodent models. Therefore, the authors decided to examine 5-lipoxygenase expression in primary canine osteosarcoma samples and have shown that approximately 65% of osteosarcomas label positive for cytoplasmic 5-lipoxygenase. Further examination of a cell culture and xenograft model shows similar 5-lipoxygenase expression. Surprisingly, a canine 5-lipoxygenase inhibitor (tepoxalin) significantly reduced cell proliferation at physiologic doses in vitro and diminished xenograft tumor growth in nude mice, suggesting that further investigation is needed. Traditionally, 5-lipoxygense leads to production of lipid mediators, such as leukotriene B(4) and 5-oxo-eicosatetraenoic acid, which, when added back to the media of tepoxalin-treated cells, did not recover cell proliferation. The lack of nuclear staining in primary and xenografted tumors and the lack of response to eicoasanoids suggest that lipid mediator production is not the primary means by which tepoxalin acts to alter proliferation. Regardless of the mechanisms involved in retarding cell proliferation, future investigation is warranted.

Regulation of inflammation in cancer by eicosanoids

Inflammation in the tumor microenvironment is now recognized as one of the hallmarks of cancer. Endogenously produced lipid autacoids, locally acting small molecule lipid mediators, play a central role in inflammation and tissue homeostasis, and have recently been implicated in cancer. A well-studied group of autacoid mediators that are the products of arachidonic acid metabolism include: the prostaglandins, leukotrienes, lipoxins and cytochrome P450 (CYP) derived bioactive products. These lipid mediators are collectively referred to as eicosanoids and are generated by distinct enzymatic systems initiated by cyclooxygenases (COX 1 and 2), lipoxygenases (5-LOX, 12-LOX, 15-LOXa, 15-LOXb), and cytochrome P450s, respectively. These pathways are the target of approved drugs for the treatment of inflammation, pain, asthma, allergies, and cardiovascular disorders. Beyond their potent anti-inflammatory and anti-cancer effects, non-steroidal anti-inflammatory drugs (NSAIDs) and COX-2 specific inhibitors have been evaluated in both preclinical tumor models and clinical trials. Eicosanoid biosynthesis and actions can also be directly influenced by nutrients in the diet, as evidenced by the emerging role of omega-3 fatty acids in cancer prevention and treatment. Most research dedicated to using eicosanoids to inhibit tumor-associated inflammation has focused on the COX and LOX pathways. Novel experimental approaches that demonstrate the anti-tumor effects of inhibiting cancer-associated inflammation currently include: eicosanoid receptor antagonism, overexpression of eicosanoid metabolizing enzymes, and the use of endogenous anti-inflammatory lipid mediators. Here we review the actions of eicosanoids on inflammation in the context of tumorigenesis. Eicosanoids may represent a missing link between inflammation and cancer and thus could serve as therapeutic target(s) for inhibiting tumor growth.

Effect of polyunsaturated fatty acids on drug-sensitive and resistant tumor cells in vitro

Previous studies showed that γ-linolenic acid (GLA, 18: 3 ω-6), arachidonic acid (AA, 20:4 ω -6), eicosapentaenoic acid (EPA, 20: 5 ω -3) and docosahexaenoic acid (DHA, 22:6 ω -3) have selective tumoricidal action. In the present study, it was observed that dihomo-gamma-linolenic acid (DGLA) and AA, EPA and DHA have cytotoxic action on both vincristine-sensitive (KB-3-1) and resistant (KB-Ch^R-8-5) cancer cells in vitro that appeared to be a free-radical dependent process but not due to the formation of prostaglandins, leukotrienes and thromboxanes. Uptake of vincristine and fatty acids was higher while their efflux was lower in KB-3-1 cells compared with KB-Ch^R-8-5 cells, suggesting that drug resistant cells have an effective efflux pump. GLA, DGLA, AA, EPA and DHA enhanced the uptake and decreased efflux in both drug-sensitive and drug-resistant cells and augmented the susceptibility of tumor cells especially, of drug-resistant cells to the cytotoxic action of vincristine. These results suggest that certain polyunsaturated fatty acids have tumoricidal action and are capable of enhancing the cytotoxic action of anti-cancer drugs specifically, on drug-resistant cells by enhancing drug uptake and reducing its efflux. Thus, polyunsaturated fatty acids either by themselves or in combination with chemotherapeutic drugs have the potential as anti-cancer molecules.

Inhibition of 5-lipoxygenase triggers apoptosis in prostate cancer cells via down-regulation of protein kinase C-epsilon

Previous studies have shown that human prostate cancer cells constitutively generate 5-lipoxygenase (5-LOX) metabolites from arachidonic acid, and inhibition of 5-LOX blocks production of 5-LOX metabolites and triggers apoptosis in prostate cancer cells. This apoptosis is prevented by exogenous metabolites of 5-LOX, suggesting an essential role of 5-LOX metabolites in the survival of prostate cancer cells. However, downstream signaling mechanisms which mediate the survival-promoting effects of 5-LOX metabolites in prostate cancer cells are still unknown. Recently, we reported that MK591, a specific inhibitor of 5-LOX activity, induces apoptosis in prostate cancer cells without inhibition of Akt, or ERK, two well-characterized regulators of pro-survival mechanisms, suggesting the existence of an Akt and ERK-independent survival mechanism in prostate cancer cells regulated by 5-LOX. Here, we report that 5-LOX inhibition-induced apoptosis in prostate cancer cells occurs via rapid inactivation of protein kinase C-epsilon (PKCε), and that exogenous 5-LOX metabolites prevent both 5-LOX inhibition-induced down-regulation of PKCε and induction of apoptosis. Interestingly, pre-treatment of prostate cancer cells with diazoxide (a chemical activator of PKCε), or KAE1-1 (a cell-permeable, octa-peptide specific activator of PKCε) prevents 5-LOX inhibition-induced apoptosis, which indicates that inhibition of 5-LOX triggers apoptosis in prostate cancer cells via down-regulation of PKCε. Altogether, these findings suggest that metabolism of arachidonic acid by 5-LOX activity promotes survival of prostate cancer cells via signaling through PKCε, a pro-survival serine/threonine kinase.

The target of arachidonic acid pathway is a new anticancer strategy for human prostate cancer

Recent epidemiological studies and animal experiments have demonstrated that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the incidence of colorectal carcinoma. Cyclooxygenase (COX) is the principal target of NSAIDs. COX is the first oxidase in the process of prostaglandin production from arachidonic acid. COX enzyme may be involved in the initiation and/or the promotion of carcinogenesis due to NSAIDs inhibition of COX. Lipoxygenase (LOX) is also an initial enzyme in the pathway for producing leukotrienes from arachidonic acid. Similar to COX, LOX enzyme may also be involved in the initiation and/or promotion of carcinogenesis. Peroxisome proliferator activator-receptor (PPAR)-γ is a ligand-activated transcriptional factor belonging to the steroid receptor superfamily. PPAR-γ plays a role in both adipocyte differentiation and carcinogenesis. PPAR-γ is one target for cell growth modulation of NSAIDs. In this review, we report the expression of COX-2, LOX and PPAR-γ in human prostate cancer tissues as well as the effects of COX-2 and LOX inhibitors and PPAR-γ ligand.

Discovery of potent and selective inhibitors of human platelet-type 12- lipoxygenase

We report the discovery of novel small molecule inhibitors of platelet-type 12-human lipoxygenase, which display nanomolar activity against the purified enzyme, using a quantitative high-throughput screen (qHTS) on a library of 153607 compounds. These compounds also exhibit excellent specificity, >50-fold selectivity vs the paralogues, 5-human lipoxygenase, reticulocyte 15-human lipoxygenase type-1, and epithelial 15-human lipoxygenase type-2, and >100-fold selectivity vs ovine cyclooxygenase-1 and human cyclooxygenase-2. Kinetic experiments indicate this chemotype is a noncompetitive inhibitor that does not reduce the active site iron. Moreover, chiral HPLC separation of two of the racemic lead molecules revealed a strong preference for the (-)-enantiomers (IC(50) of 0.43 ± 0.04 and 0.38 ± 0.05 μM) compared to the (+)-enantiomers (IC(50) of >25 μM for both), indicating a fine degree of selectivity in the active site due to chiral geometry. In addition, these compounds demonstrate efficacy in cellular models, which underscores their relevance to disease modification.

Determinants of sensitivity to DZNep induced apoptosis in multiple myeloma cells

The 3-Deazaneplanocin A (DZNep), one of S-adenosylhomocysteine (AdoHcy) hydrolase inhibitors, has shown antitumor activities in a broad range of solid tumors and acute myeloid leukemia. Here, we examined its effects on multiple myeloma (MM) cells and found that, at 500 nM, it potently inhibited growth and induced apoptosis in 2 of 8 MM cell lines. RNA from un-treated and DZNep treated cells was profiled by Affymetrix HG-U133 Plus 2.0 microarray and genes with a significant change in gene expression were determined by significance analysis of microarray (SAM) testing. ALOX5 was the most down-regulated gene (5.8-fold) in sensitive cells and was expressed at low level in resistant cells. The results were corroborated by quantitative RT-PCR. Western-blot analysis indicated ALOX5 was highly expressed only in sensitive cell line H929 and greatly decreased upon DZNep treatment. Ectopic expression of ALOX5 reduced sensitivity to DZNep in H929 cells. Furthermore, down-regulation of ALOX5 by RNA interference could also induce apoptosis in H929. Gene expression analysis on MM patient dataset indicated ALOX5 expression was significantly higher in MM patients compared to normal plasma cells. We also found that Bcl-2 was overexpressed in DZNep insensitive cells, and cotreatment with DZNep and ABT-737, a Bcl-2 family inhibitor, synergistically inhibited growth and induced apoptosis of DZNep insensitive MM cells. Taken together, this study shows one of mechanisms of the DZNep efficacy on MM correlates with its ability to down-regulate the ALOX5 levels. In addition, DZNep insensitivity might be associated with overexpression of Bcl-2, and the combination of ABT-737 and DZNep could synergistically induced apoptosis. These results suggest that DZNep may be exploited therapeutically for a subset of MM.

Pyrazole-based sulfonamide and sulfamides as potent inhibitors of mammalian 15-lipoxygenase

A series of inhibitors of mammalian 15-lipoxygenase (15-LO) based on a 3,4,5-tri-substituted pyrazole scaffold is described. Replacement of a sulfonamide functionality in the lead series with a sulfamide group resulted in improved physicochemical properties generating analogs with enhanced inhibition in cell-based and whole blood assays.

A comparative study of tissue ω-6 and ω-3 polyunsaturated fatty acids (PUFA) in benign and malignant pathologic stage pT2a radical prostatectomy specimens

OBJECTIVE

To analyze different polyunsaturated fatty acid (PUFA) tissue levels in malignant compared with benign prostatic tissue from the same prostate specimens.

MATERIALS AND METHODS

Fresh frozen benign and malignant prostatic tissue was obtained from radical prostatectomy specimens in 49 men with pathologic stage pT2a prostate cancer. Histopathologic examination confirmed that all tissues from each prostate being analyzed were either completely benign or almost totally malignant. The PUFA composition in these tissues was determined by gas-liquid chromatography on a capillary column. The relative amount of each PUFA (% of total fatty acids) was quantified by integrating the area under the peak and dividing the result by the total area of all fatty acids.

RESULTS

Tissue levels of dihomo-γ-linolenic acid, (C20:3w6), an ω-6 PUFA and a major precursor of ω-6 PUFA metabolites, were significantly higher in malignant compared with benign tissues (P = 0.002). Tissue levels of the downstream ω-6 metabolites, arachidonic acid (AA) (20:4ω6), and adrenic acid, (22:4ω6), were significantly lower in cancer tissues, (P < 0.0001 and P = 0.013, respectively). Overall, the total levels of ω-6 PUFA were lower in cancer (P = 0.001).

CONCLUSION

We found that the ω-6 PUFA AA and adrenic acid are decreased in malignant prostatic tissues compared with benign tissues from the same prostates. These findings provide additional evidence that dietary fat is associated with prostatic carcinogenesis.

Enhanced formation of 5-oxo-6,8,11,14-eicosatetraenoic acid by cancer cells in response to oxidative stress, docosahexaenoic acid and neutrophil-derived 5-hydroxy-6,8,11,14-eicosatetraenoic acid

The 5-lipoxygenase (5-LO) product 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), which is a potent chemoattractant for myeloid cells, is known to promote the survival of prostate cancer cells. In the present study, we found that PC3 prostate cancer cells and cell lines derived from breast (MCF7) and lung (A-427) cancers contain 5-hydroxyeicosanoid dehydrogenase (5-HEDH) activity and have the ability to synthesize 5-oxo-ETE from its precursor 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) when added as an exogenous substrate. H(2)O(2) strongly stimulated the synthesis of 5-oxo-ETE and induced dramatic increases in the levels of both glutathione disulfide and NADP(+). The effects of H(2)O(2) on 5-oxo-ETE and NADP(+) were blocked by N-ethylmaleimide (NEM), indicating that this effect was mediated by the glutathione reductase-dependent generation of NADP(+), the cofactor required by 5-HEDH. 5-Oxo-ETE synthesis was also stimulated by agents that have cytotoxic effects on tumor cells, including 4,7,10,13,16,19-docosahexaenoic acid, tamoxifen and MK-886. Because PC3 cells have only modest 5-LO activity compared with inflammatory cells, we investigated their ability to contribute to the transcellular biosynthesis of 5-oxo-ETE from neutrophil-derived 5-HETE. Stimulation of neutrophils with arachidonic acid and calcium ionophore in the presence of PC3 cells led to a large and selective increase in 5-oxo-ETE synthesis compared with controls in which PC3 cell 5-oxo-ETE synthesis was selectively blocked by pretreatment with NEM. The ability of prostate tumor cells to synthesize 5-oxo-ETE may contribute to tumor cell proliferation as well as the influx of inflammatory cells, which may further induce cell proliferation through the release of cytokines. 5-Oxo-ETE may be an attractive target in cancer therapy.

5-lipoxygenase: underappreciated role of a pro-inflammatory enzyme in tumorigenesis

Leukotrienes constitute a group of bioactive lipids generated by the 5-lipoxygenase (5-LO) pathway. An increasing body of evidence supports an acute role for 5-LO products already during the earliest stages of pancreatic, prostate, and colorectal carcinogenesis. Several pieces of experimental data form the basis for this hypothesis and suggest a correlation between 5-LO expression and tumor cell viability. First, several independent studies documented an overexpression of 5-LO in primary tumor cells as well as in established cancer cell lines. Second, addition of 5-LO products to cultured tumor cells also led to increased cell proliferation and activation of anti-apoptotic signaling pathways. 5-LO antisense technology approaches demonstrated impaired tumor cell growth due to reduction of 5-LO expression. Lastly, pharmacological inhibition of 5-LO potently suppressed tumor cell growth by inducing cell cycle arrest and triggering cell death via the intrinsic apoptotic pathway. However, the documented strong cytotoxic off-target effects of 5-LO inhibitors, in combination with the relatively high concentrations of 5-LO products needed to achieve mitogenic effects in cell culture assays, raise concern over the assignment of the cause, and question the relationship between 5-LO products and tumorigenesis.

Phase I/II study of oncolytic herpes simplex virus NV1020 in patients with extensively pretreated refractory colorectal cancer metastatic to the liver

This multicenter phase I/II study evaluated the safety, pharmacokinetics, and antitumor effects of repeated doses of NV1020, a genetically engineered oncolytic herpes simplex virus, in patients with advanced metastatic colorectal cancer (mCRC). Patients with liver-dominant mCRC received four fixed NV1020 doses via weekly hepatic artery infusion, followed by two or more cycles of conventional chemotherapy. Phase I included cohorts receiving 3 × 10(6), 1 × 10(7), 3 × 10(7), and 1 × 10(8) plaque-forming units (PFU)/dose to determine the optimal biological dose (OBD) for phase II. Blind independent computed tomography scan review was based on RECIST (response evaluation criteria in solid tumors) to assess hepatic tumor response. Phase I and II enrolled 13 and 19 patients, respectively. Patients experienced transient mild-moderate febrile reactions after each NV1020 infusion. Grade 3/4 virus-related toxicity was limited to transient lymphopenia in two patients. NV1020 shedding was not detected. Simultaneous cytokine and grade 1 coagulation perturbations were dose-limiting at 1 × 10(8) PFU/dose, considered the OBD. All 22 OBD patients had previously received 5-fluorouracil; most had received oxaliplatin or irinotecan (50% had both), many with at least one targeted agent. After NV1020 administration, 50% showed stable disease. The best overall tumor control rate after chemotherapy was 68% (1 partial response, 14 stable disease); this did not correlate with baseline variables or chemotherapy. Median time to progression was 6.4 months (95% confidence interval: 2, 8.9); median overall survival was 11.8 months (95% confidence interval: 8.3, 20.7). One-year survival was 47.2%. We conclude that NV1020 stabilizes liver metastases with minimal toxicity in mCRC. It may resensitize metastases to salvage chemotherapy and extend overall survival. A randomized phase II/III trial now appears justified.

5-Lipoxygenase inhibitors induce potent anti-proliferative and cytotoxic effects in human tumour cells independently of suppression of 5-lipoxygenase activity

BACKGROUND AND PURPOSE

Certain 5-lipoxygenase (5-LO) inhibitors exhibit anti-carcinogenic activities against 5-LO overexpressing tumour types and cultured tumour cells. It has been proposed therefore that 5-LO products significantly contribute to tumour cell proliferation. To date, the relationship between the inhibitory mechanisms of 5-LO inhibitors, which vary widely, and tumour cell viability has not been evaluated. This study addresses the anti-proliferative and cytotoxic potency of a number of 5-LO inhibitors with different inhibitory mechanisms in 5-LO-positive and 5-LO-negative tumour cells.

EXPERIMENTAL APPROACH

Cell viability was measured by the WST-1 assay; cell proliferation was assessed using the bromodeoxyuridine (BrdU) incorporation assay. Cell death was analysed by annexin V staining, Western blot analysis of PARP (poly ADP-ribose polymerase) cleavage and a cytotoxicity assay. 5-LO product formation was quantified by a 5-LO activity assay.

KEY RESULTS

The common 5-LO inhibitors AA-861, Rev-5901 and MK-886 induced cytotoxic and anti-proliferative effects in 5-LO-positive Capan-2 pancreatic cancer cells; BWA4C and CJ-13,610 only caused anti-proliferative effects, while zileuton failed to impair cell viability. Moreover, the concentrations of the 5-LO inhibitors required to induce anti-proliferation and cytotoxicity highly exceeded those for suppression of 5-LO. Supplementation with mitogenic 5-LO products failed to protect Capan-2 cells from the effects of 5-LO inhibitors. Finally, the cytotoxic and anti-proliferative 5-LO inhibitors also potently reduced the viability of 5-LO-deficient tumour cell lines (HeLa, Panc-1 and U937).

CONCLUSIONS AND IMPLICATIONS

Certain 5-LO inhibitors cause cytotoxic and anti-proliferative effects independently of suppression of 5-LO activity. Thus, the role of 5-LO overexpression in tumour cell viability remains unclear and requires further elucidation.

Discovery of potent and selective inhibitors of human reticulocyte 15-lipoxygenase-1

There are a variety of lipoxygenases in the human body (hLO), each having a distinct role in cellular biology. Human reticulocyte 15-lipoxygenase-1 (15-hLO-1), which catalyzes the dioxygenation of 1,4-cis,cis-pentadiene-containing polyunsaturated fatty acids, is implicated in a number of diseases including cancer, atherosclerosis, and neurodegenerative conditions. Despite the potential therapeutic relevance of this target, few inhibitors have been reported that are both potent and selective. To this end, we have employed a quantitative high-throughput (qHTS) screen against ∼74000 small molecules in search of reticulocyte 15-hLO-1 selective inhibitors. This screen led to the discovery of a novel chemotype for 15-hLO-1 inhibition, which displays nM potency and is >7500-fold selective against the related isozymes, 5-hLO, platelet 12-hLO, epithelial 15-hLO-2, ovine cyclooxygenase-1, and human cyclooxygenase-2. In addition, kinetic experiments were performed which indicate that this class of inhibitor is tight binding, reversible, and appears not to reduce the active-site ferric ion.

Role of leukotriene B4 in celecoxib-mediated anticancer effect

Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, has anticancer effect on many cancers associated with chronic inflammation by both COX-2-dependent and COX-2-independent mechanisms. The non-COX-2 targets of celecoxib, however, are still a matter of research. Leukotriene B4 (LTB4) has been implicated in prostate and colon carcinogenesis, but little is known about the potential role of LTB4 in celecoxib-mediated anticancer effect. In this study, we evaluated whether LTB4 was involved in celecoxib-mediated inhibitory effect on human colon cancer HT-29 cells and human prostate cancer PC-3 cells. Our data showed that survival of both cell lines was obviously suppressed after celecoxib treatment for 72 h in a concentration-dependent manner. However, only in HT-29 cells, this inhibitory effect could be reversed by LTB4, which promoted survival of HT-29 cells rather than PC-3 cells. Consistent with these results, lioxygenase (LOX) potent inhibitor nordihydroguaiaretic acid (NDGA) had a higher inhibitory effect on HT-29 cells than PC-3 cells. Additionally, ELISA results showed that celecoxib could suppress expression of LTB4 in both cell lines, whereas, inhibition of PGE2 was only detected in HT-29 cells. These results indicate that the anticancer effect of celecoxib is COX-2-independent in HT-29 and PC-3 cells and in HT-29 cells primarily via down-regulating LTB4 production.

Induction of VEGF by tepoxalin does not lead to increased tumour growth in a canine osteosarcoma xenograft

The purpose of this study was to determine the impact of the non-steroidal anti-inflammatory drug tepoxalin on canine tumour cell growth and describe the changes associated with tepoxalin treatment. In vitro experiments were performed to assess tepoxalin-associated alterations in tumour cell growth. Clinically achievable tepoxalin concentrations did not significantly alter tumour cell growth in vitro. Vascular endothelial growth factor (VEGF) production and hypoxia-inducible factor-1α dose-dependently increased in vitro in the presence of tepoxalin. A canine osteosarcoma xenograft was used to determine in vivo effects of tepoxalin on tumour growth and angiogenesis. Despite increased VEGF in vitro, there was a significant growth delay associated with tepoxalin treatment. Normal dogs were administered tepoxalin to assess effects on systemic VEGF production, but not found to have significantly increased VEGF. These data suggest that tepoxalin may moderately inhibit tumour growth and may be administered as an analgesic to tumour-bearing dogs.

Overexpression of 5-lipoxygenase in sporadic colonic adenomas and a possible new aspect of colon carcinogenesis

PURPOSE

We aimed to study the intracellular expression of 5-lipoxygenase (5-LOX), the primary competitor with cyclooxygenase-2 in arachidonic acid metabolism, as inflammatory enzymes may be involved in blocking apoptosis and promoting cancer growth by changing arachidonic acid metabolism within cells. Our purpose was to investigate the possible connection between 5-LOX expression and colon carcinogenesis by characterizing 5-LOX expression in histologically different colonic adenomas, determining the relationship between high expression of 5-LOX and various conventional clinicopathological features of adenomas, and finally characterizing the histological localization of cells with 5-LOX overexpression.

METHODS

A total of 111 patients were examined and 120 histologically different colonic adenomas analyzed (including four cases of intramucosal adenocarcinoma in a polyp). Immunohistochemical staining with polyclonal anti-5-LOX antibodies was performed.

RESULTS

There was a significant correlation between high 5-LOX expression and patient age, increased polyp size, high grade of intraepithelial neoplasia, villous and tubulovillous adenoma, and histological epithelial localization.

CONCLUSIONS

We observed a strong positive correlation between 5-LOX overexpression and the appearance of typical high-risk factors for malignant transformation in adenomatous polyps. The results support the role of 5-LOX in early stages of colon carcinogenesis.

Prophylactic efficacy of Coriandrum sativum (Coriander) on testis of lead-exposed mice

Lead poisoning is a worldwide health problem, and its treatment is under investigation. The aim of this study was to access the efficacy of Coriandrum sativum (coriander) in reducing lead-induced changes in mice testis. Animal exposed to lead nitrate showed significant decrease in testicular SOD, CAT, GSH, total protein, and tissue lead level. This was accompanied by simultaneous increase in the activities of LPO, AST, ALT, ACP, ALP, and cholesterol level. Serum testosterone level and sperm density were suppressed in lead-treated group compared with the control. These influences of lead were prevented by concurrent daily administration of C. sativum extracts to some extent. Treating albino mice with lead-induced various histological changes in the testis and treatment with coriander led to an improvement in the histological testis picture. The results thus led us to conclude that administration of C. sativum significantly protects against lead-induced oxidative stress. Further work need to be done to isolate and purify the active principle involved in the antioxidant activity of this plant.

Influence of Vascular Oxidative Stress and Inflammation on the Development and Progression of Atherosclerosis

Cardiovascular disease (CVD) risk factors such as hypertension, diabetes, dyslipidemia, smoking, physical inactivity, and obesity increase production of vascular reactive oxygen species (ROS), which results in a reduction of bioavailable nitric oxide and ultimately endothelial dysfunction and endothelial cell activation. ROS appears to mediate the inflammatory pathways that participate in the development and progression of atherosclerosis. There are numerous markers of oxidative stress and inflammation available for assessing the therapeutic response to interventions, but few are currently recommended for clinical use. Exercise training improves endothelial function via several mechanisms, including increased endothelial nitric oxide synthase—nitric oxide (eNOS-NO)— mediated production, increased activity and amount of antioxidants, attenuated ROS production, and an apparent reduction in systemic inflammation, possibly related to an increase in myokines resulting from skeletal muscle activation. Dietary antioxidant supplementation may improve endothelial function, oxidative stress, and inflammation, but much controversy exists regarding the use of antioxidant supplementation in primary and secondary CVD prevention. The purpose of this article is to review the contribution of vascular oxidative stress and activation of the inflammatory pathways in the pathogenesis of CVD and to review common methods used in clinical research to assess vascular oxidative stress and inflammation in response to therapeutic lifestyle interventions.

Impact of distal mutation on hydrogen transfer interface and substrate conformation in soybean lipoxygenase

The impact of distal mutation on the hydrogen transfer interface properties and on the substrate mobility, conformation, and orientation in soybean lipoxygenase-1 (SLO) is examined. SLO catalyzes a hydrogen abstraction reaction that occurs by a proton-coupled electron transfer mechanism. Mutation of isoleucine 553 to less bulky residues has been found experimentally to increase the magnitude and temperature dependence of the kinetic isotope effect for this reaction. This residue borders the linoleic acid substrate but is approximately 15 A from the active site iron. In the present study, we model these experimental data with a vibronically nonadiabatic theory and perform all-atom molecular dynamics simulations on the complete solvated wild-type and mutant enzymes. Our calculations indicate that the proton transfer equilibrium distance increases and the associated frequency decreases as residue 553 becomes less bulky. The molecular dynamics simulations illustrate that this mutation impacts the mobility, geometrical conformation, and orientation of the linoleic acid within the active site. In turn, these effects alter the proton donor-acceptor equilibrium distance and frequency, leading to the experimentally observed changes in the magnitude and temperature dependence of the kinetic isotope effect. This study provides insight into how the effects of distal mutations may be transmitted in enzymes to ultimately impact the catalytic rates.

15-HETE protects rat pulmonary arterial smooth muscle cells from apoptosis via the PI3K/Akt pathway

15-Hydroxyeicosatetraenoic acid (15-HETE), a metabolic product of arachidonic acid (AA), plays an important role in pulmonary vascular smooth muscle remodeling. Although its effects on the apoptotic responses are known, the underlying mechanisms are still poorly understood. Since Akt is a critical regulator of cell survival and vascular remodeling, there may be a crosstalk between 15-HETE anti-apoptotic process and PI3K/Akt survival effect in rat pulmonary arterial smooth muscle cells (PASMCs). To test this hypothesis, we studied the effect of 15-HETE on cell survival and apoptosis using Western blot, cell viability measurement, nuclear morphology determination, TUNEL assay and mitochondrial potential analysis. We found that activation of the PI3K/Akt signaling system was necessary for the 15-HETE to suppress PASMC apoptosis and improve cell survival. Our results indicated that 15-HETE inhibited the apoptotic responses of PASMCs, including morphological alterations, mitochondrial depolarization and the expression apoptosis-specific proteins. These effects were likely to be mediated through the activation of PI3K/Akt. Two downstream signal molecules of PI3K/Akt were identified. Both FasL and Bad were down-regulated by 15-HETE and 15-HETE phosphorylated Bad. These changes depended on the PI3K/Akt signaling pathway in PASMCs. Thus a signal transduction pathway was demonstrated which is necessary for the effects of 15-HETE in protection PASMCs from apoptosis.

Polymorphisms of pro-inflammatory genes and prostate cancer risk: a pharmacogenomic approach

In this paper, we consider the role of the genetics of inflammation in the pathophysiology of prostate cancer (PCa). This paper is not an extensive review of the literature, rather it is an expert opinion based on data from authors' laboratories on age-related diseases and inflammation. The aim is the detection of a risk profile that potentially allows both the early identification of individuals at risk for disease and the possible discovery of potential targets for medication. In fact, a major goal of clinical research is to improve early detection of age-related diseases, cancer included, by developing tools to move diagnosis backward in disease temporal course, i.e., before the clinical manifestation of the malady, where treatment might play a decisive role in preventing or significantly retarding the manifestation of the disease. The better understanding of the function and the regulation of inflammatory pathway in PCa may help to know the mechanisms of its formation and progression, as well as to identify new targets for the refinement of new treatment such as the pharmacogenomics approach.