Xenobiotic-metabolizing cytochromes P450 convert prostaglandin endoperoxide to hydroxyheptadecatrienoic acid and the mutagen, malondialdehyde

Brain Tumors: Development, Drug Resistance, and Sensitization - An Epigenetic Approach

In this article, we describe contrasting developmental aspects of paediatric and adult brain tumours. We hypothesize that the formation of cancer progenitor cells, for both paediatric and adult, could be due to epigenetic events. However, the progression of adult brain tumours selectively involves more mutations compared to paediatric tumours. We further discuss epigenetic switches, comprising both histone modifications and DNA methylation, and how they can differentially regulate transcription and expression of oncogenes and tumour suppressor genes. Next, we summarize the currently available therapies for both types of brain tumours, explaining the merits and failures leading to drug resistance. We analyse different mechanisms of drug resistance and the role of epigenetics in this process. We then provide a rationale for combination therapy, which includes epigenetic drugs. In the end, we postulate a concept which describes how a combination therapy could be initiated. The timing, doses, and order of individual drug regimens will depend on the individual case. This type of combination therapy will be part of a personalized medicine which will differ from patient to patient.

Interplay of Oxidative Stress, Inflammation, and Autophagy in RAW 264.7 Murine Macrophage Cell Line Challenged with Si/SiO2 Quantum Dots

Quantum dots (QDs) with photostable fluorescence are recommended for imaging applications; however, their effect on living cells is incompletely understood. We aimed to elucidate the RAW 264.7 murine macrophage cell line's response to the Si/SiO₂ QDs challenge. Cells were exposed to 5 and 15 μg/mL Si/SiO₂ QDs for 6 h, 12 h, and 24 h. Cell metabolic activity and viability were assessed by MTT, live/dead, and dye-exclusion assays. Oxidative stress and membrane integrity were assessed by anion superoxide, malondialdehyde, and lactate dehydrogenase activity evaluations. Antioxidative enzyme activities were analyzed by kinetic spectrophotometric methods. Cytokines were analyzed with an antibody-based magnetic bead assay, PGE2 was assessed by ELISA, and Nrf-2, Bcl-2, Beclin 1, and the HSPs were analyzed by western blot. Autophagy levels were highlighted by fluorescence microscopy. The average IC50 dose for 6, 12, and 24 h was 16.1 ± 0.7 μg/mL. Although glutathione S-transferase and catalase were still upregulated after 24 h, superoxide dismutase was inhibited, which together allowed the gradual increase of malondialdehyde, anion superoxide, nitric oxide, and the loss of membrane integrity. G-CSF, IL-6, TNF-α, MIP-1β, MCP-1, Nrf-2, PGE2, and RANTES levels, as well as autophagy processes, were increased at all time intervals, as opposed to caspase 1 activity, COX-2, HSP60, and HSP70, which were only upregulated at the 6-h exposure interval. These results underscore that Si/SiO₂ QDs possess significant immunotoxic effects on the RAW 264.7 macrophage cell line and stress the importance of developing effective strategies to mitigate their adverse impact.

Hepatic stellate cell stearoyl co-A desaturase activates leukotriene B4 receptor 2 - β-catenin cascade to promote liver tumorigenesis

Hepatocellular carcinoma (HCC) is the 3rd most deadly malignancy. Activated hepatic stellate cells (aHSC) give rise to cancer-associated fibroblasts in HCC and are considered a potential therapeutic target. Here we report that selective ablation of stearoyl CoA desaturase-2 (Scd2) in aHSC globally suppresses nuclear CTNNB1 and YAP1 in tumors and tumor microenvironment and prevents liver tumorigenesis in male mice. Tumor suppression is associated with reduced leukotriene B4 receptor 2 (LTB4R2) and its high affinity oxylipin ligand, 12-hydroxyheptadecatrienoic acid (12-HHTrE). Genetic or pharmacological inhibition of LTB4R2 recapitulates CTNNB1 and YAP1 inactivation and tumor suppression in culture and in vivo. Single cell RNA sequencing identifies a subset of tumor-associated aHSC expressing Cyp1b1 but no other 12-HHTrE biosynthetic genes. aHSC release 12-HHTrE in a manner dependent on SCD and CYP1B1 and their conditioned medium reproduces the LTB4R2-mediated tumor-promoting effects of 12-HHTrE in HCC cells. CYP1B1-expressing aHSC are detected in proximity of LTB4R2-positive HCC cells and the growth of patient HCC organoids is blunted by LTB4R2 antagonism or knockdown. Collectively, our findings suggest aHSC-initiated 12-HHTrE-LTB4R2-CTNNB1-YAP1 pathway as a potential HCC therapeutic target.

Therapy resistance mechanisms in hematological malignancies

Hematologic malignancies are model diseases for understanding neoplastic transformation and serve as prototypes for developing effective therapies. Indeed, the concept of systemic cancer therapy originated in hematologic malignancies and has guided the development of chemotherapy, cellular therapies, immunotherapy and modern precision oncology. Despite significant advances in the treatment of leukemias, lymphomas and multiple myelomas, treatment resistance associated with molecular and clinical relapse remains very common. Therapy of relapsed and refractory disease remains extremely difficult, and failure of disease control at this stage remains the leading cause of mortality in patients with hematologic malignancies. In recent years, many efforts have been made to identify the genetic and epigenetic mechanisms that drive the development of hematologic malignancies to the stage of full-blown disease requiring clinical intervention. In contrast, the mechanisms responsible for treatment resistance in hematologic malignancies remain poorly understood. For example, the molecular characteristics of therapy-resistant persisting cells in minimal residual disease (MRD) remain rather elusive. In this mini-review we want to discuss that cellular heterogeneity and plasticity, together with adaptive genetic and epigenetic processes, lead to reduced sensitivity to various treatment regimens such as chemotherapy and pathway inhibitors such as tyrosine kinase inhibitors. However, resistance mechanisms may be conserved across biologically distinct cancer entities. Recent technological advances have made it possible to explore the underlying mechanisms of therapy resistance with unprecedented resolution and depth. These include novel multi-omics technologies with single cell resolution combined with advanced biocomputational approaches, along with artificial intelligence (AI) and sophisticated disease models for functional validation.

The effect of EMPAgliflozin on markers of inflammation in patients with concomitant type 2 diabetes mellitus and Coronary ARtery Disease: the EMPA-CARD randomized controlled trial

Systemic inflammation and oxidative burden in patients with type 2 diabetes mellitus (T2DM) causes deleterious cardiovascular outcomes. We sought to investigate the clinical antioxidative and anti-inflammatory effects of empagliflozin. Platelet function, oxidant and antioxidant biomarkers and pro-inflammatory agents at baseline and at 26 weeks were measured. A total of 95 patients (41.05% male, mean age 62.85 ± 7.91 years, mean HbA_1c 7.89 ± 0.96%) with concomitant T2DM and coronary artery disease (CAD) were randomized (1:1) to receive empagliflozin (10 mg/daily) or placebo. Patients treated with empagliflozin had lower levels of interleukin 6 (IL-6) (adjusted difference (adiff): - 1.06 pg/mL, 95% CI - 1.80; - 0.32, P = 0.006), interleukin 1β (IL-1β) and high-sensitive C-reactive protein (Hs-CRP) (adiff: - 4.58 pg/mL and - 2.86 mg/L; P = 0.32 and 0.003, respectively) compared to placebo. There were elevations in super oxidase dismutase (SOD) activity, glutathione (GSHr), and total antioxidant capacity (TAC) with empagliflozin (adiff: 3.7 U/mL, 0.57 muM, and 124.08 mmol/L, 95% CI 1.36; 6.05, 0.19; 0.95, and 47.98; 200.18, P = 0.002, 0.004, and 0.002, respectively). While reactive oxygen species (ROS) improved significantly (adiff: - 342.51, 95% CI - 474.23; - 210.79, P < 0.001), the changes in catalase activity (CAT), malondialdehyde (MDA), or protein carbonyl groups (PCG) were not significant. Moreover, the P-selectin antigen expression on platelet surface was significantly reduced (adiff: - 8.81, 95% CI - 14.87; - 2.75, P = 0.005). Markers of glycemic status (fasting blood glucose, HbA_1c, and HOMA-IR (homeostatic model assessment for insulin resistance) significantly improved (P < 0.001). Among patients with T2DM and CAD, 6-month treatment with empagliflozin can mitigate inflammation, platelet activity and oxidative stress and is associated with clinical cardiovascular benefits.Trial Registration Iranian Registry of Clinical Trials. www.IRCT.ir , Identifier: IRCT20190412043247N2. Registration Date: 6/13/2020. Registration timing: prospective.

Quantitative Assessment of the Impact of Crohn's Disease on Protein Abundance of Human Intestinal Drug-Metabolising Enzymes and Transporters

Crohn's disease affects the mucosal layer of the intestine, predominantly ileum and colon segments, with the potential to affect the expression of intestinal enzymes and transporters, and consequently, oral drug bioavailability. We carried out a quantitative proteomic analysis of inflamed and non-inflamed ileum and colon tissues from Crohn's disease patients and healthy donors. Homogenates from samples in each group were pooled and protein abundance determined by liquid chromatography-mass spectrometry (LC-MS). In inflamed Crohn's ileum, CYP3A4, CYP20A1, CYP51A1, ADH1B, ALPI, FOM1, SULT1A2, SULT1B1 and ABCB7 showed ≥10-fold reduction in abundance compared with healthy baseline. By contrast, only MGST1 showed ≥10 fold reduction in inflamed colon. Ileal UGT1A1, MGST1, MGST2, and MAOA levels increased by ≥2 fold in Crohn's patients, while only ALPI showed ≥2 fold increase in the colon. Counter-intuitively, non-inflamed ileum had a higher magnitude of fold change than inflamed tissue when compared with healthy tissue. Marked but non-uniform alterations were observed in the expression of various enzymes and transporters in ileum and colon compared with healthy samples. Modelling will allow improved understanding of the variable effects of Crohn's disease on bioavailability of orally administered drugs.

Pros and Cons of Pharmacological Manipulation of cGMP-PDEs in the Prevention and Treatment of Breast Cancer

The cyclic nucleotides, cAMP and cGMP, are ubiquitous second messengers responsible for translating extracellular signals to intracellular biological responses in both normal and tumor cells. When these signals are aberrant or missing, cells may undergo neoplastic transformation or become resistant to chemotherapy. cGMP-hydrolyzing phosphodiesterases (PDEs) are attracting tremendous interest as drug targets for many diseases, including cancer, where they regulate cell growth, apoptosis and sensitization to radio- and chemotherapy. In breast cancer, PDE5 inhibition is associated with increased intracellular cGMP levels, which is responsible for the phosphorylation of PKG and other downstream molecules involved in cell proliferation or apoptosis. In this review, we provide an overview of the most relevant studies regarding the controversial role of PDE inhibitors as off-label adjuvants in cancer therapy.

In vivo Study of a Newly Synthesized Chromen-4-one Derivative as an Antitumor Agent against HCC

BACKGROUND

Chromenes are a wide group of natural compounds that can be synthesized chemically. The chromen-4-one nucleus acts as a skeleton for varieties of additional active groups that makes the chromene activity vary between antioxidant and anti-inflammatory agents. In the present study, a newly synthesized chromene compound exhibits different behaviors other than anti-inflammatory and antioxidant activities that it is the first time that a member of chromen-4-one compound can control the cancer progress. Inflammation is the first step in tumor development where the severity grade can potentiate tumor growth and progression. In many tumors, pro-inflammatory genes record high expression level such as tumor necrosis factor (TNF-α) and vascular endothelial growth factors (VEGF). These pro-inflammatory factors act as rate limiting steps in tumor initiation, and controlling its expression acts as an early therapeutic way to control the tumor proliferation. The chromone derivatives have biological activities such as anti-inflammatory and anti-tumor activity.

METHODS

In the present study, hepatocellular cancer (HCC) induced by diethylnitrosamine (DEN) in rats and then treated with the new chromene derivative and the parameters TNF-α, VEGF, p53, Cyt C, MMP-9, Bcl2, and Bax were measured.

RESULTS

The treatment strategy Ch compound is to downregulate pro-inflammatory gene expression of early genes as TNF-α as well as VEGF and subsequently control other factors such as p53, Cyt C, and MMP-9. Also, retrieve the balance between Bcl2 and Bax proteins in DEN-induced HCC in rats.

CONCLUSION

The ability of the new Ch derivative to control the primary initiators of HCC such as TNF-α offers this derivative an anti-tumor activity and encourages further researches to follow and monitor its effect on the molecular level.

Calculation of CYP450 protein-ligand binding and dissociation free energy paths

The function of an enzyme depends on its dynamic structure, and the catalytic mechanism has long been an active focus of research. The principle for interpreting protein selectivity and fidelity stems from optimization of the active site upon protein-substrate complexation, i.e., a lock-and-key configuration, on which most protein-substrate molecule binding recognition, and hence drug discovery, relies. Yet another thought has been to incorporate the protein folding interior tunnels for stereo- and regio-selectivity along the protein-substrate or protein-ligand/inhibitor binding process. Free energy calculations provide valuable information for molecular recognition and protein-ligand binding dynamics and kinetics. In this study, we focused on the kinetics of cytochrome P450 proteins (CYP450s) and the protein interior tunnel structure-dynamics relationship in terms of the substrate binding and leaving mechanism. A case in point is given by the prostaglandin H₂ (PGH₂) homologous isomerase of prostacyclin synthase. To calculate the reactant and product traversing the tunnels to and from the heme site, the free energy paths and tunnel potentials of mean force are constructed from steered molecular dynamics simulations and adaptive basing force umbrella sampling simulations. We explore the binding tunnels and critical residue lining characteristics for the ligand traverse and the underlying mechanism of CYP450 activity. Our theoretical analysis provides insights into the decisive role of the substrate tunnel binding process of the CYP450 mechanism and may be useful in drug design and protein engineering contexts.

Genetic and Epigenetic Modulation of Drug Resistance in Cancer: Challenges and Opportunities

Cancer is a complex disease that has the ability to develop resistance to traditional therapies. The current chemotherapeutic treatment has become increasingly sophisticated, yet it is not 100% effective against disseminated tumours. Anticancer drugs resistance is an intricate process that ascends from modifications in the drug targets suggesting the need for better targeted therapies in the therapeutic arsenal. Advances in the modern techniques such as DNA microarray, proteomics along with the development of newer targeted drug therapies might provide better strategies to overcome drug resistance. This drug resistance in tumours can be attributed to an individual's genetic differences, especially in tumoral somatic cells but acquired drug resistance is due to different mechanisms, such as cell death inhibition (apoptosis suppression) altered expression of drug transporters, alteration in drug metabolism epigenetic and drug targets, enhancing DNA repair and gene amplification. This review also focusses on the epigenetic modifications and microRNAs, which induce drug resistance and contributes to the formation of tumour progenitor cells that are not destroyed by conventional cancer therapies. Lastly, this review highlights different means to prevent the formation of drug resistant tumours and provides future directions for better treatment of these resistant tumours.

LC-MS Quantification of Malondialdehyde-Dansylhydrazine Derivatives in Urine and Serum Samples

We developed a robust analytical method for quantification of malondialdehyde (MDA) in urine and serum samples using dansylhydrazine (DH) as a derivatizing reagent. The derivatization procedure was partially carried out using an autosampler injection program to minimize errors associated with the low-volume addition of reagents and was optimized to yield a stable hydrazone derivative of MDA and its labeled d2-MDA analogue. The target MDA-DH derivatives were separated on an Agilent Zorbax Eclipse Plus Phenyl-Hexyl (3.0 × 100 mm, 3.5 μm) column. The mass-to-charge ratios of the target derivatives [(M+H)+ of 302 and 304 for MDA-DH and d2-MDA-DH, respectively] were analyzed in single ion monitoring mode using a single quadrupole mass spectrometer operated under positive electrospray ionization. The method limits of quantification were 5.63 nM (or 0.405 ng/mL) for urine analysis and 5.68 nM (or 0.409 ng/mL) for serum analysis. The quantification range for urine analysis was 5.63-500 nM (0.405-36.0 ng/mL) while the quantification range for serum analysis was 5.68-341 nM (0.409-24.6 ng/mL). The method showed good relative recoveries (98-103%), good accuracies (92-98%), and acceptable precisions (relative standard deviations 1.8-7.3% for inter-day precision; 1.8-6.1% for intra-day precision) as observed from the repeat analysis of quality control samples prepared at different concentrations. The method was used to measure MDA in individual urine samples (n = 287) and de-identified archived serum samples (n = 22) to assess the overall performance of the method. The results demonstrated that our method is capable of measuring urinary and serum levels of MDA, allowing its future application in epidemiologic investigations.

Oxygen Surrogate Systems for Supporting Human Drug-Metabolizing Cytochrome P450 Enzymes

Oxygen surrogates (OSs) have been used to support cytochrome P450 (P450) enzymes for diverse purposes in drug metabolism research, including reaction phenotyping, mechanistic and inhibition studies, studies of redox partner interactions, and to avoid the need for NADPH or a redox partner. They also have been used in engineering P450s for more cost-effective, NADPH-independent biocatalysis. However, despite their broad application, little is known of the preference of individual P450s for different OSs or the substrate dependence of OS-supported activity. Furthermore, the biocatalytic potential of OSs other than cumene hydroperoxide (CuOOH) and hydrogen peroxide (H₂O₂) is yet to be explored. Here, we investigated the ability of the major human drug-metabolizing P450s, namely CYP3A4, CYP2C9, CYP2C19, CYP2D6, and CYP1A2, to use the following OSs: H₂O₂, tert-butyl hydroperoxide (tert-BuOOH), CuOOH, (diacetoxyiodo)benzene, and bis(trifluoroacetoxy)iodobenzene. Overall, CuOOH and tert-BuOOH were found to be the most effective at supporting these P450s. However, the ability of P450s to be supported by OSs effectively was also found to be highly dependent on the substrate used. This suggests that the choice of OS should be tailored to both the P450 and the substrate under investigation, underscoring the need to employ screening methods that reflect the activity toward the substrate of interest to the end application. SIGNIFICANCE STATEMENT: Cytochrome P450 (P450) enzymes can be supported by different oxygen surrogates (OSs), avoiding the need for a redox partner and costly NADPH. However, few data exist comparing relative activity with different OSs and substrates. This study shows that the choice of OS used to support the major drug-metabolizing P450s influences their relative activity and regioselectivity in a substrate-specific fashion and provides a model for the more efficient use of P450s for metabolite biosynthesis.

DNA Adducts as Biomarkers To Predict, Prevent, and Diagnose Disease-Application of Analytical Chemistry to Clinical Investigations

Characterization of the chemistry, structure, formation, and metabolism of DNA adducts has been one of the most significant contributions to the field of chemical toxicology. This work provides the foundation to develop analytical methods to measure DNA adducts, define their relationship to disease, and establish clinical tests. Monitoring exposure to environmental and endogenous toxicants can predict, diagnose, and track disease as well as guide therapeutic treatment. DNA adducts are one of the most promising biomarkers of toxicant exposure owing to their stability, appearance in numerous biological matrices, and characteristic analytical properties. In addition, DNA adducts can induce mutations to drive disease onset and progression and can serve as surrogate markers of chemical exposure. In this perspective, we highlight significant advances made within the past decade regarding DNA adduct quantitation using mass spectrometry. We hope to expose a broader audience to this field and encourage analytical chemistry laboratories to explore how specific adducts may be related to various pathologies. One of the limiting factors in developing clinical tests to measure DNA adducts is cohort size; ideally, the cohort would allow for model development and then testing of the model to the remaining cohort. The goals of this perspective article are to (1) provide a summary of analyte levels measured using state-of-the-art analytical methods, (2) foster collaboration, and (3) highlight areas in need of further investigation.

Determination of oxidative stress levels and some antioxidant enzyme activities in prostate cancer

In this study, the antioxidant enzyme activities such as (SOD, GSH, and CAT) and malondialdehyde (MDA) level which is the end product of lipid peroxidation, were determined from the serum samples taken from patients diagnosed with prostate cancer Van Yuzuncu Yıl University Medical Faculty of Educational Research and Training Hospital and İstanbul Bagcilar Education Research Hospital. The SOD, GSH, and CAT activity of patient groups was found significantly lower than the healthy control group in patients with prostate cancer (p < .05). Serum MDA level is found significantly high when compared to control groups. MDA levels increased in patients that suffer prostate cancer disorder. Whereas, firstly antioxidant enzymes activity of SOD, GSH and CAT have been decreased in control groups. Thus, we concluded that the cause of development of prostate cancer may be the result of an imbalance between the antioxidants and oxidative stress. As a result, SOD, CAT, GSH, and MDA may play an important role in the etiopathogenesis of prostate cancer.

Arylpropionic acid-derived NSAIDs: New insights on derivatization, anticancer activity and potential mechanism of action

NSAIDs displayed chemopreventive and anticancer effects against several types of cancers. Moreover, combination of NSAIDs with anticancer agents resulted in enhanced anticancer activity. These findings have attracted much attention of researchers working in this field. The 2-arylpropionic acid-derived NSAIDs represent one of the most widely used anti-inflammatory agents. Additionally, they displayed antiproliferative activities against different types of cancer cells. Large volume of research was performed to identify molecular targets responsible for this activity. However, the exact mechanism underlying the anticancer activity of profens is still unclear. In this review article, the anticancer potential, structure activity relationship and synthesis of selected profen derivatives were summarized. This review is focused also on non-COX targets which can mediate the anticancer activity of this derivatives. The data in this review highlighted profens as promising lead compounds in future research to develop potent and safe anticancer agents.

Sensitization of Drug Resistant Cancer Cells: A Matter of Combination Therapy

Cancer drug resistance is an enormous problem. It is responsible for most relapses in cancer patients following apparent remission after successful therapy. Understanding cancer relapse requires an understanding of the processes underlying cancer drug resistance. This article discusses the causes of cancer drug resistance, the current combination therapies, and the problems with the combination therapies. The rational design of combination therapy is warranted to improve the efficacy. These processes must be addressed by finding ways to sensitize the drug-resistant cancers cells to chemotherapy, and to prevent formation of drug resistant cancer cells. It is also necessary to prevent the formation of cancer progenitor cells by epigenetic mechanisms, as cancer progenitor cells are insensitive to standard therapies. In this article, we emphasize the role for the rational development of combination therapy, including epigenetic drugs, in achieving these goals.

Optical study of chemotherapy efficiency in cancer treatment via intracellular structural disorder analysis using partial wave spectroscopy

As cancer progresses, macromolecules, such as DNA, RNA or lipids, inside cells undergo spatial structural rearrangements and alterations. Mesoscopic light transport-based optical partial wave spectroscopy (PWS) was recently introduced to quantify changes in the nanoscale structural disorder in biological cells. The PWS measurement is performed using a parameter termed as "disorder strength" (L _d ), which represents the degree of nanoscale structural disorder inside the cells. It was shown that cancerous cells have higher disorder strength than normal cells. In this work, we first used the PWS to analyze the hierarchy of different types of prostate cancer cells, namely, C4-2, DU-145 and PC-3, by quantifying their average disorder strengths. Results expectedly showed that L _d values increases in accordance with the increasing aggressiveness/tumorigenicity levels of these cells. Using the L _d parameter, we then analyzed the chemoresistance properties of these prostate cancer cells to docetaxel drug compared to their chemosensitivity. Results show that chemoresistant cancer cells have increased L _d values, that is, higher disorder strength, relative to chemosensitive cancer cells. Thus, use of the L _d metric can be effective in determining the efficacy of particular chemotherapy.

The relationships between cytochromes P450 and H2O2: Production, reaction, and inhibition

In this review we address the relationship between cytochromes P450 (P450) and H2O2. This association can affect biology in three distinct ways. First, P450s produce H2O2 as a byproduct either during catalysis or when no substrate is present. This reaction, known as uncoupling, releases reactive oxygen species that may have implications in disease. Second, H2O2 is used as an oxygen-donating co-substrate in peroxygenase and peroxidase reactions catalyzed by P450s. This activity has proven to be important mainly in reactions involving prokaryotic P450s, and investigators have harnessed this reaction with the aim of adaptation for industrial use. Third, H2O2-dependent inhibition of human P450s has been studied in our laboratory, demonstrating heme destruction and also the inactivating oxidation of the heme-thiolate ligand to a sulfenic acid (-SOH). This reversible oxidative modification of P450s may have implications in the prevention of uncoupling and may give new insights into the oxidative regulation of these enzymes. Research has elucidated many of the chemical mechanisms involved in the relationship between P450 and H2O2, but the application to biology is difficult to evaluate. Further studies are needed reveal both the harmful and protective natures of reactive oxygen species in an organismal context.

Formation and Cleavage of C-C Bonds by Enzymatic Oxidation-Reduction Reactions

Many oxidation-reduction (redox) enzymes, particularly oxygenases, have roles in reactions that make and break C-C bonds. The list includes cytochrome P450 and other heme-based monooxygenases, heme-based dioxygenases, nonheme iron mono- and dioxygenases, flavoproteins, radical S-adenosylmethionine enzymes, copper enzymes, and peroxidases. Reactions involve steroids, intermediary metabolism, secondary natural products, drugs, and industrial and agricultural chemicals. Many C-C bonds are formed via either (i) coupling of diradicals or (ii) generation of unstable products that rearrange. C-C cleavage reactions involve several themes: (i) rearrangement of unstable oxidized products produced by the enzymes, (ii) oxidation and collapse of radicals or cations via rearrangement, (iii) oxygenation to yield products that are readily hydrolyzed by other enzymes, and (iv) activation of O₂ in systems in which the binding of a substrate facilitates O₂ activation. Many of the enzymes involve metals, but of these, iron is clearly predominant.

AHR-related activities in a creosote-adapted population of adult atlantic killifish, Fundulus heteroclitus, two decades post-EPA superfund status at the Atlantic Wood Site, Portsmouth, VA USA

Atlantic killifish, Fundulus heteroclitus, are adapted to creosote-based PAHs at the US EPA Superfund site known as Atlantic Wood (AW) on the southern branch of the Elizabeth River, VA USA. Subsequent to the discovery of the AW population in the early 1990s, these fish were shown to be recalcitrant to CYP1A induction by PAHs under experimental conditions, and even to the time of this study, killifish embryos collected from the AW site are resistant to developmental deformities typically associated with exposure to PAHs in reference fish. Historically, however, 90 +% of the adult killifish at this site have proliferative hepatic lesions including cancer of varying severity. Several PAHs at this site are known to be ligands for the aryl hydrocarbon receptor (AHR). In this study, AHR-related activities in AW fish collected between 2011 and 2013 were re-examined nearly 2 decades after first discovery. This study shows that CYP1A mRNA expression is three-fold higher in intestines of AW killifish compared to a reference population. Using immunohistochemistry, CYP1A staining in intestines was uniformly positive compared to negative staining in reference fish. Livers of AW killifish were examined by IHC to show that CYP1A and AHR2 protein expression reflect lesions-specific patterns, probably representing differences in intrinsic cellular physiology of the spectrum of proliferative lesions comprising the hepatocarcinogenic process. We also found that COX2 mRNA expression levels were higher in AW fish livers compared to those in the reference population, suggesting a state of chronic inflammation. Overall, these findings suggest that adult AW fish are responsive to AHR signaling, and do express CYP1A and AHR2 proteins in intestines at a level above what was observed in the reference population.

Effect of ketoconazole and diltiazem on the pharmacokinetics of apixaban, an oral direct factor Xa inhibitor

AIM

Apixaban is an orally active inhibitor of coagulation factor Xa and is eliminated by multiple pathways, including renal and non-renal elimination. Non-renal elimination pathways consist of metabolism by cytochrome P450 (CYP) enzymes, primarily CYP3A4, as well as direct intestinal excretion. Two single sequence studies evaluated the effect of ketoconazole (a strong dual inhibitor of CYP3A4 and P-glycoprotein [P-gp]) and diltiazem (a moderate CYP3A4 inhibitor and a P-gp inhibitor) on apixaban pharmacokinetics in healthy subjects.

METHOD

In the ketoconazole study, 18 subjects received apixaban 10 mg on days 1 and 7, and ketoconazole 400 mg once daily on days 4-9. In the diltiazem study, 18 subjects received apixaban 10 mg on days 1 and 11 and diltiazem 360 mg once daily on days 4-13.

RESULTS

Apixaban maximum plasma concentration and area under the plasma concentration-time curve extrapolated to infinity increased by 62% (90% confidence interval [CI], 47, 78%) and 99% (90% CI, 81, 118%), respectively, with co-administration of ketoconazole, and by 31% (90% CI, 16, 49%) and 40% (90% CI, 23, 59%), respectively, with diltiazem.

CONCLUSION

A 2-fold and 1.4-fold increase in apixaban exposure was observed with co-administration of ketoconazole and diltiazem, respectively.

Monooxygenase, peroxidase and peroxygenase properties and reaction mechanisms of cytochrome P450 enzymes

This review examines the monooxygenase, peroxidase and peroxygenase properties and reaction mechanisms of cytochrome P450 (CYP) enzymes in bacterial, archaeal and mammalian systems. CYP enzymes catalyze monooxygenation reactions by inserting one oxygen atom from O2 into an enormous number and variety of substrates. The catalytic versatility of CYP stems from its ability to functionalize unactivated carbon-hydrogen (C-H) bonds of substrates through monooxygenation. The oxidative prowess of CYP in catalyzing monooxygenation reactions is attributed primarily to a porphyrin π radical ferryl intermediate known as Compound I (CpdI) (Por•+FeIV=O), or its ferryl radical resonance form (FeIV-O•). CYP-mediated hydroxylations occur via a consensus H atom abstraction/oxygen rebound mechanism involving an initial abstraction by CpdI of a H atom from the substrate, generating a highly-reactive protonated Compound II (CpdII) intermediate (FeIV-OH) and a carbon-centered alkyl radical that rebounds onto the ferryl hydroxyl moiety to yield the hydroxylated substrate. CYP enzymes utilize hydroperoxides, peracids, perborate, percarbonate, periodate, chlorite, iodosobenzene and N-oxides as surrogate oxygen atom donors to oxygenate substrates via the shunt pathway in the absence of NAD(P)H/O2 and reduction-oxidation (redox) auxiliary proteins. It has been difficult to isolate the historically elusive CpdI intermediate in the native NAD(P)H/O2-supported monooxygenase pathway and to determine its precise electronic structure and kinetic and physicochemical properties because of its high reactivity, unstable nature (t½~2 ms) and short life cycle, prompting suggestions for participation in monooxygenation reactions of alternative CYP iron-oxygen intermediates such as the ferric-peroxo anion species (FeIII-OO-), ferric-hydroperoxo species (FeIII-OOH) and FeIII-(H2O2) complex.

Cyclooxygenase-2 and the inflammogenesis of breast cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that constitutive overexpression of cyclooxygenase-2 (COX-2) is a ubiquitous driver of mammary carcinogenesis, and reciprocally, that COX-2 blockade has strong potential for breast cancer prevention and therapy. Key findings include the following: (1) COX-2 is constitutively expressed throughout breast cancer development and expression intensifies with stage at detection, cancer progression and metastasis; (2) essential features of mammary carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis and immunosuppression) are linked to COX-2-driven prostaglandin E2 (PGE-2) biosynthesis; (3) upregulation of COX-2 and PGE-2 expression induces transcription of CYP-19 and aromatase-catalyzed estrogen biosynthesis which stimulates unbridled mitogenesis; (4) extrahepatic CYP-1B1 in mammary adipose tissue converts paracrine estrogen to carcinogenic quinones with mutagenic impact; and (5) agents that inhibit COX-2 reduce the risk of breast cancer in women without disease and reduce recurrence risk and mortality in women with breast cancer. Recent sharp increases in global breast cancer incidence and mortality are likely driven by chronic inflammation of mammary adipose and upregulation of COX-2 associated with the obesity pandemic. The totality of evidence clearly supports the supposition that mammary carcinogenesis often evolves as a progressive series of highly specific cellular and molecular changes in response to induction of constitutive over-expression of COX-2 and the prostaglandin cascade in the “inflammogenesis of breast cancer”.

Drug resistance in cancer: an overview

Cancers have the ability to develop resistance to traditional therapies, and the increasing prevalence of these drug resistant cancers necessitates further research and treatment development. This paper outlines the current knowledge of mechanisms that promote or enable drug resistance, such as drug inactivation, drug target alteration, drug efflux, DNA damage repair, cell death inhibition, and the epithelial-mesenchymal transition, as well as how inherent tumor cell heterogeneity plays a role in drug resistance. It also describes the epigenetic modifications that can induce drug resistance and considers how such epigenetic factors may contribute to the development of cancer progenitor cells, which are not killed by conventional cancer therapies. Lastly, this review concludes with a discussion on the best treatment options for existing drug resistant cancers, ways to prevent the formation of drug resistant cancers and cancer progenitor cells, and future directions of study.

Urinary biomarkers of oxidative status

Oxidative damage produced by reactive oxygen species (ROS) has been implicated in the etiology and pathology of many health conditions, including a large number of chronic diseases. Urinary biomarkers of oxidative status present a great opportunity to study redox balance in human populations. With urinary biomarkers, specimen collection is non-invasive and the organic/metal content is low, which minimizes the artifactual formation of oxidative damage to molecules in specimens. Also, urinary levels of the biomarkers present intergraded indices of redox balance over a longer period of time compared to blood levels. This review summarizes the criteria for evaluation of biomarkers applicable to epidemiological studies and evaluation of several classes of biomarkers that are formed non-enzymatically: oxidative damage to lipids, proteins, DNA, and allantoin, an oxidative product of uric acid. The review considers formation, metabolism, and exertion of each biomarker, available data on validation in animal and clinical models of oxidative stress, analytical approaches, and their intra- and inter-individual variation. The recommended biomarkers for monitoring oxidative status over time are F₂-isoprostanes and 8-oxodG. For inter-individual comparisons, F₂-isoprostanes are recommended, whereas urinary 8-oxodG levels may be confounded by differences in the DNA repair capacity. Promising urinary biomarkers include allantoin, acrolein-lysine, and dityrosine.

Human CYP2S1 metabolizes cyclooxygenase- and lipoxygenase-derived eicosanoids

CYP2S1 is a recently described dioxin-inducible cytochrome P450. We previously demonstrated that human CYP2S1 oxidizes a number of carcinogens but only via the peroxide shunt. In this article, we investigated whether human CYP2S1 can metabolize cyclooxygenase- and lipoxygenase-derived lipid peroxides in a NADPH-independent fashion. Human CYP2S1 metabolizes prostaglandin G(2) (PGG(2)) (K(m) = 0.267 ± 0.072 μM) into several products including 12S-hydroxy-5Z,8E,10E-heptadecatrienoic acid (12-HHT). It also metabolizes prostaglandin H(2) (PGH(2)) (K(m) = 11.7 ± 2.8 μM) into malondialdehyde, 12-HHT, and thromboxane A(2) (TXA(2)). The turnover to 12-HHT by human CYP2S1 (1.59 ± 0.04 min(-1)) is 40-fold higher than that of TXA(2) (0.04 min(-1)). In addition to PGG(2) and PGH(2) metabolism, human CYP2S1 efficiently metabolizes the hydroperoxyeicosatetraenoic acids (5S-, 12S-, and 15S-) and 13S-hydroperoxyoctadecadienoic acid into 5-oxo-eicosatetraenoic acid (turnover = 16.7 ± 0.3 min(-1)), 12-oxo-eicosatetraenoic acid 1 (11.5 ± 0.9 min(-1)), 15-oxo-eicosatetraenoic acid (16.9 ± 0.8 min(-1)), and 13-octadecadienoic acid (20.2 ± 0.9 min(-1)), respectively. Other cytochromes P450 such as CYP1A1, 1A2, 1B1, and 3A4 underwent similar conversions but at slower rates. The fatty acid hydroperoxides were also converted by human CYP2S1 to several epoxyalcohols. Our data indicate that fatty acid endoperoxides and hydroperoxides represent endogenous substrates of CYP2S1 and suggest that the enzyme CYP2S1 may play an important role in the inflammatory process because some of the products that CYP2S1 produces play important roles in inflammation.

Characterization of covalent adducts of nucleosides and DNA formed by reaction with levuglandin

Enhanced expression of cyclooxygenase-2 (COX-2) is associated with development of several cancers. The product of COX-2, prostaglandin H(2) (PGH(2)), can undergo spontaneous rearrangement and nonenzymatic ring cleavage to form the highly reactive levuglandin E(2) (LGE(2)) or D(2) (LGD(2)). Incubation with LGE(2) causes DNA-protein cross-linking in cultured cells, suggesting that levuglandins can directly react with DNA. We report the identification by liquid chromatography-tandem mass spectrometry of a stable levuglandin-deoxycytidine (LG-dC) adduct that forms upon reaction of levuglandin with DNA. We found that LGE(2) reacted with deoxycytidine, deoxyadenosine, or deoxyguanosine in vitro to form covalent adducts with a dihydroxypyrrolidine structure, as deduced from selective ion fragmentation. For LG-deoxycytidine adducts, the initial dihydroxypyrrolidine structure converted to a pyrrole structure over time. Reaction of LG with DNA yielded a stable LG-dC adduct with a pyrrole structure. These results describe the first structure of levuglandinyl-DNA adducts and provide the tools with which to evaluate the potential for LG-DNA adduct formation in vivo.

Up-regulation of inflammatory signalings by areca nut extract and role of cyclooxygenase-2 -1195G>a polymorphism reveal risk of oral cancer

Because the mRNA expression of cyclooxygenase-2 (COX-2) is up-regulated by arecoline in human gingival fibroblasts, as shown in our previous study, we further investigated the mRNA expression level of COX-2 and its upstream effectors in three oral epithelial carcinoma cell lines (KB, SAS, and Ca9-22) by using areca nut extract (ANE) and saliva-reacted ANE (sANE). A case-control study of 377 oral squamous cell carcinoma (OSCC) patients and 442 controls was conducted to evaluate the gene-environment interaction between COX-2 promoter polymorphisms and substance use of alcohol, betel quid, and cigarettes (ABC) in risk of OSCC. The heterogeneous characteristics of the oral site and the COX-2 -1195G>A polymorphism in these cell lines showed diverse inflammatory response (KB>>Ca9-22>SAS) after 24-hour ANE/sANE treatments, and the COX-2 up-regulation might be mostly elicited from alternative nuclear factor-kappaB activation. In the case-control study, betel chewing [adjusted odds ratios (aOR), 42.2] posed a much higher risk of OSCC than alcohol drinking and cigarette smoking (aORs, 2.4 and 1.8, respectively), whereas the COX-2 -1195A/A homozygote presented a potential genetic risk (OR, 1.55). The strongest joint effect for OSCC was seen in betel chewers with -1195A/A homozygote (aOR, 79.44). In the non-betel chewing group, the -1195A/G and A/A genotypes together with the combined use of alcohol and cigarettes increased risk to 15.1-fold and 32.1-fold, respectively, compared with the G/G genotype without substance use. Taken together, these findings illustrate a valuable insight into the potential role of the COX-2 promoter region in contributing to the development of betel-related OSCC, including ANE/sANE-induced transcriptional effects and enhanced joint effects of COX-2 -1195A allele with substance use of ABC.

Cytochrome P450 oxidation of the thiophene-containing anticancer drug 3-[(quinolin-4-ylmethyl)-amino]-thiophene-2-carboxylic acid (4-trifluoromethoxy-phenyl)-amide to an electrophilic intermediate

Compounds that are enzymatically transformed to reactive intermediates are common in nature. Some drugs and many phytochemicals that contain a thiophene ring are oxidized by cytochrome P450 to biological reactive intermediates (BRI) that can covalently bind to thiol nucleophiles. The investigational anticancer agent 3-[(quinolin-4-ylmethyl)-amino]-thiophene-2-carboxylic acid (4-trifluoromethoxy-phenyl)-amide (OSI-930) contains a thiophene moiety that can be oxidized by P450s to an apparent sulfoxide, which can react via Michael-addition to the 5-position of the thiophene ring, as demonstrated by mass spectral characterization of several thioether conjugates of the presumed thiophene S-oxide. Furthermore, a stable deuterium isotope retention experiment in which solvent deuterium was incorporated into the thiophene verifies the sulfoxide pathway. Various thiol nucleophiles are shown by tandem mass spectra to bind with this BRI, which is activated by P450 3A4 and to a slight degree, P450 2D6. Yet various safe drugs, phytochemicals, and endogenous molecules, all noted for their activation to BRI, are not toxic at a normal dose. Thus, multiple features determine any consequence of a BRI, with these complexities determining why one BRI is benign while another is not. The retention of covalent protein adducts of radio-labeled intermediate rat tissue has a half-life of about 1-1.5 days; hence, modified protein is cleared and replaced relatively quickly.

Cyclooxygenase-2 (cox-2) and the inflammogenesis of cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that aberrant induction of COX-2 and up-regulation of the prostaglandin cascade play a significant role in carcinogenesis, and reciprocally, blockade of the process has strong potential for cancer prevention and therapy. Supporting evidence includes the following: [1] expression of constitutive COX-2-catalyzed prostaglandin biosynthesis is induced by most cancer-causing agents including tobacco smoke and its components (polycylic aromatic amines, heterocyclic amines, nitrosamines), essential polyunsaturated fatty acids (unconjugated linoleic acid), mitogens, growth factors, proinflammatory cytokines, microbial agents, tumor promoters, and other epigenetic factors, [2] COX-2 expression is a characteristic feature of all premalignant neoplasms, [3] COX-2 expression is a characteristic feature of all malignant neoplasms, and expression intensifies with stage at detection and cancer progression and metastasis, [4] all essential features of carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis, and immunosuppression) are linked to COX-2-driven prostaglandin (PGE-2) biosynthesis, [5] animal studies show that COX-2 up-regulation (in the absence of genetic mutations) is sufficient to stimulate the transformation of normal cells to invasive cancer and metastatic disease, [6] non-selective COX-2 inhibitors, such as aspirin and ibuprofen, reduce the risk of human cancer and precancerous lesions, and [7] selective COX-2 inhibitors, such as celecoxib, reduce the risk of human cancer and precancerous lesions at all anatomic sites thus far investigated. Results confirming that COX-2 blockade is effective for both cancer prevention and therapy have been tempered by observations that some COX2 inhibitors pose a risk to the cardiovascular system, and more studies are needed in order to determine if certain of these drugs can be taken at dosages that prevent cancer without increasing cardiovascular risk. It is emphasized that the "inflammogenesis model of cancer" is not mutually exclusive and may in fact be synergistic with the accumulation of somatic mutations in tumor suppressor genes and oncogenes or epigenetic factors in the development of cancer.

Effect of Chia oil (Salvia Hispanica) rich in omega-3 fatty acids on the eicosanoid release, apoptosis and T-lymphocyte tumor infiltration in a murine mammary gland adenocarcinoma

We investigated the effects of certain dietary polyunsaturated fatty acids (PUFAs) and related eicosanoids on the growth and metastasis formation of a murine mammary gland adenocarcinoma. Salvia hispanica (ChO) and Carthamus tinctorius (SaO) vegetable oil sources of omega-3 and -6 PUFAs and a commercial diet as control (CO), were used. We analysed fatty acids of neoplastic cells (NC) membranes by GLC; the eicosanoids 12- HETE and 12-HHT (LOX and COX metabolites) by HPLC and apoptosis and T-lymphocyte infiltration by flow cytometry and microscopy. NC from ChO groups showed lower levels of arachidonic acid and of both eicosanoids compared to SaO and CO (p<0.05). The ChO diet decreased the tumor weight and metastasis number (p<0.05). Apoptosis and T-lymphocyte infiltration were higher and mitosis decreased with respect to the other diets (p<0.05). Present data showed that ChO, an ancient and almost unknown source of omega-3, inhibits growth and metastasis in this tumor model.

PGH2 Degradation Pathway Catalyzed by GSH−Heme Complex Bound Microsomal Prostaglandin E2 Synthase Type 2: The First Example of a Dual-Function Enzyme,

Prostaglandin E2 synthase (PGES) catalyzes the isomerization of PGH2 to PGE2. PGES type 2 (mPGES-2) is a membrane-associated enzyme, whose N-terminal section is apparently inserted into the lipid bilayer. Both intact and N-terminal truncated enzymes have been isolated and have similar catalytic activity. The recombinant N-terminal truncated enzyme purified from Escherichia coli HB101 grown in LB medium containing delta-aminolevulinate and Fe(NO3)3 has a red color, while the same enzyme purified from the same E. coli grown in minimal medium has no color. The red-colored enzyme has been characterized by mass, fluorescence, and EPR spectroscopies and X-ray crystallography. The enzyme is found to contain bound glutathione (GSH) and heme. GSH binds to the active site with six H-bonds, while a heme is complexed with bound GSH forming a S-Fe coordination bond with no polar interaction with mPGES-2. There is a large open space between the heme and the protein, where a PGH2 might be able to bind. The heme dissociation constant is 0.53 microM, indicating that mPGES-2 has relatively strong heme affinity. Indeed, expression of mPGES-2 in E. coli stimulates heme biosynthesis. Although mPGES-2 has been reported to be a GSH-independent PGES, the crystal structure and sequence analysis indicate that mPGES-2 is a GSH-binding protein. The GSH-heme complex-bound enzyme (mPGES-2h) catalyzes formation of 12(S)-hydroxy-5(Z),8(E),10(E)-heptadecatrienoic acid and malondialdehyde from PGH2, but not formation of PGE2. The following kinetic parameters at 37 degrees C were determined: KM = 56 microM, kcat = 63 s-1, and kcat/KM = 1.1 x 10(6) M-1 s-1. They suggest that mPGES-2h has significant catalytic activity for PGH2 degradation. It is possible that both GSH-heme complex-free and -bound enzymes are present in the same tissues. mPGES-2 in heme-rich liver is most likely to become the form of mPGES-2h and might be involved in degradation reactions similar to that of cytochrome P450. Since mPGES-2 is an isomerase and mPGES-2h is a lyase, mPGES-2 cannot simply be classified into one of six classes set by the International Union of Biochemistry and Molecular Biology.

The role of cytochrome P450 enzymes in endogenous signalling pathways and environmental carcinogenesis

Some cytochrome P450 (CYP) heme-thiolate enzymes participate in the detoxication and, paradoxically, the formation of reactive intermediates of thousands of chemicals that can damage DNA, as well as lipids and proteins. CYP expression can also affect the production of molecules derived from arachidonic acid, and alters various downstream signal-transduction pathways. Such changes can be precursors to malignancy. Recent studies in mice have changed our perceptions about the function of CYP1 enzymes. We suggest a two-tiered system to predict an overall inter-individual risk of tumorigenesis based on DNA variants in certain 'early defence' CYP genes, combined with polymorphisms in various downstream target genes.

Potential pathogenetic implications of cyclooxygenase-2 overexpression in B chronic lymphoid leukemia cells

Evidence suggests that cyclooxygenase-2 (COX-2) increases tumorigenic potential by promoting resistance to apoptosis. Because B chronic lymphoid leukemia (B-CLL) cells exhibit a defective apoptotic response, we analyzed CD19(+) B lymphocytes purified from the peripheral blood of B-CLL patients. Microarray analysis showed a variable (up to 38-fold) increase in the steady-state mRNA levels of COX-2 in B-CLL lymphocytes compared with normal CD19(+) B lymphocytes. The up-regulation of COX-2 in B-CLL cells was confirmed by reverse transcriptase-polymerase chain reaction and Western blot analyses. Moreover, immunohistochemical analysis of B-CLL bone marrow infiltrates confirmed clear expression of COX-2 in leukemic cells. Ex vivo treatment with the COX-2 inhibitor NS-398 significantly decreased the survival of leukemic cells by increasing the rate of spontaneous apoptosis in 13 of 16 B-CLL samples examined, but it did not affect the survival of normal lymphocytes. Pretreatment with NS-398 significantly potentiated the cytotoxicity induced by chlorambucil in 8 of 16 B-CLL samples examined. Moreover, although recombinant tumor necrosis factor-related apoptosis inducing ligand (TRAIL)/Apo2L showed little cytotoxic effect in most B-CLL samples examined, pretreatment with NS-398 sensitized 8 of 16 B-CLL samples to TRAIL-induced apoptosis. Taken together, our data indicate that COX-2 overexpression likely represents an additional mechanism of resistance to apoptosis in B-CLL and that pharmacological suppression of COX-2 might enhance chemotherapy-mediated apoptosis.

Redirection of Eicosanoid Metabolism in mPGES-1-deficient Macrophages

Microsomal prostaglandin E synthase (mPGES)-1 is one of several prostaglandin E synthases involved in prostaglandin H2 (PGH2) metabolism. In the present report, we characterize the contribution of mPGES-1 to cellular PGH2 metabolism in murine macrophages by studying the synthesis of eicosanoids and expression of eicosanoid metabolism enzymes in wild type and mPGES-1-deficient macrophages. Thioglycollate-elicited macrophages isolated from mPGES-1-/- animals and genetically matched wild type controls were stimulated with diverse pro-inflammatory stimuli. Prostaglandins were released in the following order of decreasing abundance from wild type macrophages stimulated with lipopolysaccharide: prostaglandin E2 (PGE2)>thromboxane B2 (TxB2)>6-keto prostaglandin F1alpha (PGF1alpha), prostaglandin F(2alpha) (PGF2alpha), and prostaglandin D2 (PGD2). In contrast, we detected in mPGES-1-/- macrophages a >95% reduction in PGE2 production resulting in the following altered prostaglandin profile: TxB2>6-keto PGF1alpha and PGF2alpha>PGE2, despite the comparable release of total prostaglandins. No significant change in expression pattern of key prostaglandin-synthesizing enzymes was detected between the genotypes. We then further profiled genotype-related differences in the eicosanoid profile using macrophages pre-stimulated with lipopolysaccharide followed by a 10-min incubation with 10 microm [3H]arachidonic acid. Eicosanoid products were subsequently identified by reverse phase high pressure liquid chromatography. The dramatic reduction in [3H]PGE2 formation from mPGES-1-/- macrophages compared with controls resulted in TxB2 and 6-keto PGF1alpha becoming the two most abundant prostaglandins in these samples. Our results also suggest a 5-fold increase in 12-[3H]hydroxyheptadecatrienoic acid release in mPGES-1-/- samples. Our data support the hypothesis that mPGES-1 induction in response to an inflammatory stimulus is essential for PGE2 synthesis. The redirection of prostaglandin production in mPGES-1-/- cells provides novel insights into how a cell processes the unstable endoperoxide PGH2 during the inactivation of a major metabolic outlet.

Cyclooxygenase inhibition in cancer prevention and treatment

Several lines of evidence suggest that the cyclooxygenase enzymes (specifically COX-2) might be an important molecular target for the intervention of cancer at both early and late stages of some cancers, providing an opportunity for both cancer prevention and therapy. COX-2 is overexpressed during carcinogenesis, and appears to have a role in both tumour initiation and promotion and is amenable to intervention. This review discusses the importance of COX modulation via non-specific, as well as COX-2 specific COX inhibitors (NSAIDs and COX-2 selective inhibitors [COXIB]). A brief discussion on the pharmacoeconomic considerations of NSAID and COXIB use and safety issues that have recently been the focus of debate, will be presented.

Transcriptional Control of COX-2 via C/EBPbeta

Cyclooxygenase-2 (COX-2) is a highly inducible enzyme exerting diverse actions on cell functions, including proliferation, migration, and DNA damage. Enhanced COX-2 expression may be protective, but excessive expression may be harmful, causing inflammation, atheromatous plaque instability, and intimal hyperplasia. COX-2 transcriptional activation by proinflammatory mediators has been extensively characterized. In this review, the role of C/EBP in regulating COX-2 transcription is highlighted. Recent advances in control of COX-2 transcription by aspirin and salicylate and by a cell cycle-dependent endogenous mechanism are described. The recent progress sheds light on the pathophysiological mechanisms of COX-2 and new transcription-based strategy for controlling COX-2 overexpression and COX-2-mediated cardiovascular diseases.

Hepatocellular bioactivation and cytotoxicity of the synthetic endoperoxide antimalarial arteflene

Arteflene is a synthetic endoperoxide antimalarial. Its peroxide bridge undergoes iron(II)-mediated reduction in vitro which yields a carbon-centered cyclohexyl radical and a mixture of cis- and trans-alpha,beta-unsaturated ketones (enones). The enones are biliary metabolites in rats and therefore surrogate markers of bioactivation. Arteflene is reported to be more cytotoxic to primary rat hepatocytes than some non-endoperoxide antimalarials. Hepatic metabolism of arteflene was investigated in recirculating isolated perfused rat livers, and the drug's metabolism and cytotoxicity were compared using hepatocytes from male rats. Both preparations metabolized [(14)C]arteflene to cis- and trans-[(14)C]enone, 8-hydroxyarteflene glucuronide and an unassigned isomeric glucuronide. During a 2 h liver perfusion, the cis- and trans-enones recovered in bile represented 8.1 +/- 3.4 and 11.3 +/- 4.6% (mean +/- S.D., N=6), respectively, of the [(14)C]arteflene (52 microM) added to the perfusate. After a 3 h incubation of [(14)C]arteflene (10 microM) with hepatocytes in suspension, the cis- and trans-enones comprised, respectively, 14.8 +/- 7.1 and 2.1 +/- 1.0% (N = 4) of the recovered radioactivity; the corresponding data for cultured hepatocytes being 18.6 +/- 6.9 and 3.3 +/- 2.2%. Arteflene was significantly (P < 0.05) toxic to isolated hepatocytes with reference to extramitochondrial reductase activity (tetrazolium reduction) but not enzyme leakage when the cells were exposed to drug concentrations > or =50 microM for 24 h. Cellular glutathione was depleted under these conditions. Therefore arteflene was acutely cytotoxic, though only at relatively high concentrations, when it was metabolized via a pathway which generates carbon-centered radicals.

Selective and powerful stress gene expression in Arabidopsis in response to malondialdehyde

The provenance, half-life and biological activity of malondialdehyde (MDA) were investigated in Arabidopsis thaliana. We provide genetic confirmation of the hypothesis that MDA originates from fatty acids containing more than two methylene-linked double bonds, showing that tri-unsaturated fatty acids are the in vivo source of up to 75% of MDA. The abundance of the combined pool of free and reversibly bound MDA did not change dramatically in stress, although a significant increase in the free MDA pool under oxidative conditions was observed. The half-life of infiltrated MDA indicated rapid metabolic turnover/sequestration. Exposure of plants to low levels of MDA using a recently developed protocol powerfully upregulated many genes on a cDNA microarray with a bias towards those implicated in abiotic/environmental stress (e.g. ROF1 and XERO2). Remarkably, and in contrast to the activities of other reactive electrophile species (i.e. small vinyl ketones), none of the pathogenesis-related (PR) genes tested responded to MDA. The use of structural mimics of MDA isomers suggested that the propensity of the molecule to act as a cross-linking/modifying reagent might contribute to the activation of gene expression. Changes in the concentration/localisation of unbound MDA in vivo could strongly affect stress-related transcription.

Increased cyclooxygenase-2 (COX-2): a potential role in the pathogenesis of lymphoma

B cell lymphomas are a diverse group of clinicopathologic diseases with an increasing incidence. As with other malignancies, the accumulation of genetic abnormalities are required for malignant transformation of human lymphocytes. Cyclooxygenase-2 (COX-2) is a key biosynthetic enzyme in prostaglandin synthesis and has been implicated in the pathogenesis of numerous malignancies including colon, breast, and lung cancer. There is little data on the potential role of COX-2 in lymphoma pathogenesis. In this study, several B lymphoma cell lines and primary B cells obtained from normal volunteer controls were examined for COX-2 protein expression. Immunoblot analysis demonstrated between an approximately 2.2-4.3-fold increase in COX-2 protein expression relative to primary B cells in all lymphoma cell lines examined. Increased COX-2 phosphorylation was found in the BJAB, BL41, and Raji cells whereas the levels in Daudi, Namalwa, and Ramos did not differ from that of primary B cells. Treatment with 25-100 microM celecoxib (CEL) resulted in decreased proliferation as measured by [3H]thymidine in all cell lines examined, and the effect was dose-dependent, and not significantly enhanced by chlorambucil (CHL). The effect of COX-2 inhibition on apoptosis in lymphoma cells was examined and revealed apoptotic induction of greater than 85% in all cell lines examined at 50 microM celecoxib. The pro-apoptotic effect was dose-dependent, and was not significantly enhanced by chlorambucil. Examination of apoptosis-related proteins by immunoblot analysis revealed levels of BCL-2, BCL-X(L), and Bax to be unaffected by celecoxib. In contrast, levels of Akt, MCL-1, and phosphorylated SAP-kinase were all decreased after incubation with 50 microM celecoxib. These findings suggest that increased COX-2 expression and activity, contributes to the pathogenesis of B cell lymphomas and point to a possible role for COX-2 inhibition in their treatment.

Inhibitors of cyclo-oxygenase 2: a new class of anticancer agents?

Experimental studies have shown that cyclo-oxygenase 2 (COX2) is involved in tumour development and progression. Selective inhibitors of COX2 (coxibs) block tumour growth through many mechanisms, especially by antiangiogenic and proapoptotic effects. In experimental models, coxibs potentiate the activity of cytotoxic agents, hormones, and radiotherapy. Large clinical studies have shown chemopreventive activity of coxibs in colorectal cancer. The findings of preclinical studies coupled with the overexpression of COX2 observed in advanced human tumours are the basis for new therapeutic anticancer strategies based on combinations of coxibs with other anticancer treatment modalities. Early clinical studies have documented the feasibility, good tolerability, and promising activity of coxibs combined with chemotherapy in patients with advanced colorectal and non-small-cell lung cancers. Here, we describe the recent findings on the antitumour effects of coxibs with particular focus on the opportunities that have emerged for treatment of cancer.