Eicosanoids and cancer

Eicosanoids are 20-carbon bioactive lipids derived from the metabolism of polyunsaturated fatty acids, which can modulate various biological processes including cell proliferation, adhesion and migration, angiogenesis, vascular permeability and inflammatory responses. In recent years, studies have shown the importance of eicosanoids in the control of physiological and pathological processes associated with several diseases, including cancer. The polyunsaturated fatty acid predominantly metabolized to generate 2-series eicosanoids is arachidonic acid, which is the major n-6 polyunsaturated fatty acid found in animal fat and in the occidental diet. The three main pathways responsible for metabolizing arachidonic acid and other polyunsaturated fatty acids to generate eicosanoids are the cyclooxygenase, lipoxygenase and P450 epoxygenase pathways. Inflammation plays a decisive role in various stages of tumor development including initiation, promotion, invasion and metastasis. This review will focus on studies that have investigated the role of prostanoids and lipoxygenase-derived eicosanoids in the development and progression of different tumors, highlighting the findings that may provide insights into how these eicosanoids can influence cell proliferation, cell migration and the inflammatory process. A better understanding of the complex role played by eicosanoids in both tumor cells and the tumor microenvironment may provide new markers for diagnostic and prognostic purposes and identify new therapeutic strategies in cancer treatment.

High-throughput screening assays for cyclooxygenase-2 and 5-lipoxygenase, the targets for inflammatory disorders.

High-throughput screening (HTS) involves testing of compound libraries against validated drug targets using quantitative bioassays to identify ‘hit’ molecules that modulate the activity of target, which forms the starting point of a drug discovery effort. Eicosanoids formed via cyclooxygenase (COX) and lipoxygenase (LOX) pathways are major players in various inflammatory disorders. As the conventional non-steroidal anti-inflammatory drugs (NSAIDs) that inhibit both the constitutive (COX-1) and the inducible (COX-2) isoforms have gastric and renal side effects and the recently developed COX-2 selective anti-inflammatory drugs (COXIBs) have cardiac side effects, efforts are being made to develop more potent and safer anti-inflammatory drugs. Current assay methods for these enzymes, such as oxygraphic, radioisotopic, spectrophotometric etc. are not compatible for screening of large number of compounds as in drug discovery programs. In the present study, HTS-compatible assays for COX-1, COX-2 and 5-LOX were developed for screening of compound libraries with the view to identify potential anti-inflammatory drug candidates. A spectrophotometric assay involving co-oxidation of tetramethyl-p-phenylene diamine (TMPD) during the reduction of prostaglandin G2 (PGG2) to PGH2 was adopted and standardized for screening of compounds against COX-1 and COX-2. Similarly, the HTS-compatible FOX (ferrous oxidation-xylenol orange) based spectrophotometric assay involving the formation of Fe3+/xylenol orange complex showing absorption in the visible range was developed for screening of compounds against 5-LOX.

Angiotensin II induces NF-κB, JNK and p38 MAPK activation in monocytic cells and increases matrix metalloproteinase-9 expression in a PKC- andRho kinase-dependent manner

Angiotensin II (ANG II), the main effector of the renin-angiotensin system, is implicated in endothelial permeability, recruitment and activation of the immune cells, and also vascular remodeling through induction of inflammatory genes. Matrix metalloproteinases (MMPs) are considered to be important inflammatory factors. Elucidation of ANG II signaling pathways and of possible cross-talks between their components is essential for the development of efficient inhibitory medications. The current study investigates the inflammatory signaling pathways activated by ANG II in cultures of human monocytic U-937 cells, and the effects of specific pharmacological inhibitors of signaling intermediates on MMP-9 gene (MMP-9) expression and activity. MMP-9 expression was determined by real-time PCR and supernatants were analyzed for MMP-9 activity by ELISA and zymography methods. A multi-target ELISA kit was employed to evaluate IκB, NF-κB, JNK, p38, and STAT3 activation following treatments. Stimulation with ANG II (100 nM) significantly increased MMP-9 expression and activity, and also activated NF-κB, JNK, and p38 by 3.8-, 2.8- and 2.2-fold, respectively (P < 0.01). ANG II-induced MMP-9 expression was significantly reduced by 75 and 67 percent, respectively, by co-incubation of the cells with a selective inhibitor of protein kinase C (GF109203X, 5 µM) or of rho kinase (Y-27632, 15 µM), but not with inhibitors of phosphoinositide 3-kinase (wortmannin, 200 nM), tyrosine kinases (genistein, 100 µM) or of reactive oxygen species (α-tocopherol, 100 µM). Thus, protein kinase C and Rho kinase are important components of the inflammatory signaling pathways activated by ANG II to increase MMP-9 expression in monocytic cells. Both signaling molecules may constitute potential targets for effective management of inflammation.

T-cell protein tyrosine phosphatase: a role in inflammation and autoimmunity

A cDNA of PTPN2 encoding for T-cell protein tyrosine phosphate [TC-PTP] was isolated and characterized as long as 20 years ago. However, findings suggesting a potentially exciting role of this enzyme in general autoimmunity have only recently been obtained. Genome-wide association scans of the human genome revealed the involvement of PTPN2 in susceptibility to a several autoimmune disorders such as Crohn's disease, type 1 diabetes, and Graves' disease. Functional studies in immune cells revealed a key role of this enzyme in down-regulation of cytokine expression and inflammatory response, which provides an essential background to explaining the pathophysiological role of TC-PTP in autoimmunity. Thus, in addition to PTPN22, PTPN2 is likely to represent a second member of the broad family of non-receptor PTPs contributing to general autoimmunity

Rebamipide-induced downregulation of phospholipase D inhibits inflammation and proliferation in gastric cancer cells

Rebamipide a gastroprotective drug, is clinically used for the treatment of gastric ulcers and gastritis, but its actions on gastric cancer are not clearly understood. Phospholipase D (PLD) is overexpressed in various types of cancer tissues and has been implicated as a critical factor in inflammation and carcinogenesis. However, whether rebamipide is involved in the regulation of PLD in gastric cancer cells is not known. In this study, we showed that rebamipide significantly suppressed the expression of both PLD1 and PLD2 at a transcriptional level in AGS and MKN-1 gastric cancer cells. Downregulation of PLD expression by rebamipide inhibited its enzymatic activity. In addition, rebamipide inhibited the transactivation of nuclear factor kappa B (NFkappaB), which increased PLD1 expression. Rebamipide or PLD knockdown significantly suppressed the expression of genes involved in inflammation and proliferation and inhibited the proliferation of gastric cancer cells. In conclusion, rebamipide-induced downregulation of PLD may contribute to the inhibition of inflammation and proliferation in gastric cancer.

New Directions in Inflammation and Immunity: The Multi-functional Role of the Extracellular RNA/RNase System.

In the mid-eighties of the last century, extracellular-proteolipid complexes have been identified in tumor patients and circulating RNA was suggested to represent a specific secretory product of cancer cells. The presence of specific types of RNA in a variety of cancer types proved to be useful in cancer diagnosis. It has been suggested that extracellular RNA and DNA are not inert molecules, but contain biological activities. Recent data have demonstrated that extracellular RNA is likely to present the up to now undefined “natural foreign surface”, serving as an initiating factor in blood coagulation in vivo. Yet, extracellular RNA seems to have even more functions. Investigations on blood-brain-barrier have shown that extracellular RNA mediates endothelial permeability. Ample success has been achieved in administrating RNase in different animal models of vascular diseases, thereby significantly delaying thrombus formation and reducing cerebral edema formation with neuroprotection in acute stroke models. Furthermore, extracellular mammalian RNA was found to decrease tumor yield in a murine model system, suggesting that extracellular RNA might trigger immune response. Finally, extracellular nucleic acids were identified as danger signals involved in innate immunity related to neutrophil-mediated bacterial killing and haemocyte activation and coagulation in the insects. Thus, a new area of research on extracellular RNA functions with promising future perspectives just started in the field of inflammation and immunity.

Associação entre fatores de risco cardiovascular e proteína C-reativa em mulheres idosas / Association between cardiovascular risk factors and C-reactive protein in aged women

INTRODUÇÃO: O processo inflamatório desempenha um importante papel na etiologia das doenças cardiovasculares. Muitos estudos demonstram que níveis elevados de proteína C-reativa (PCR), uma proteína hepática de fase aguda, estão associados ao risco de tais eventos. Objetivos: Investigar a existência de associação entre PCR e fatores de risco cardiovascular em mulheres idosas MATERIAL E MÉTODO: Foram realizadas avaliações antropométricas, impedanciometria, verificação de pressão arterial, mensurações de perfil lipídico, glicemia em jejum e PCR. RESULTADOS: Observou-se que a PCR esteve relacionada com índice de massa corporal (p = 0,001) e com percentual de gordura corporal (p = 0,015), não apresentando relação significativa com nenhuma outra variável estudada. DISCUSSÃO: A associação entre PCR e marcadores de obesidade é consenso na literatura, podendo, no entanto, não significar verdadeira progressão da aterosclerose ou de um estado inflamatório. Em relação à inexistência de associação com os demais fatores de risco cardiovascular observada neste estudo, os dados encontrados são conflitantes. Há autores que indicam a correlação entre PCR e tais fatores; outros apontam sua inexistência. CONCLUSÕES: Este trabalho demonstra a associação da PCR a marcadores de obesidade, mas não a outros fatores de risco cardiovascular.

BACKGROUND: The inflammatory process plays an important role in the etiology of cardiovascular diseases. Several studies have shown that high levels of C-reactive protein (CRP), a hepatic acute phase protein, are associated with the risk of such diseases. OBJECTIVES: In this study we investigated the existence of association between CRP and cardiovascular risk factors in elderly women. MATERIAL AND METHOD: Anthropometric data, body impedance, blood pressure, lipid profiles, fasting glucose and CRP levels were evaluated. RESULTS: We observed that CRP was linked with body mass index (p = 0.001) and body fat percentage (p = 0.015) and there was no significant connection with any other studied variable. DISCUSSION: The association between CRP and measures of obesity is a consensus in literature. However, it may not show a true progression of atherosclerosis or an inflammatory state. Regarding the inexistence of association with other cardiovascular risk factors observed in this study, the gathered data are conflicting. Some authors indicate correlation between PCR and such factors, whereas others point out its inexistence. CONCLUSIONS: This study demonstrates the association of CRP with obesity, but not with other cardiovascular risk factors.

The Expression of Thymidine Phosphorylase in Cancer-infiltrating Inflammatory Cells in Stomach Cancer

Thymidine phosphorylase (TP) has shown to be up-regulated in several cancers and to play a role in angiogenesis and invasion. Most studies regarding TP have focused on cancer cells. Recently, evidences suggest that TP in cancer-infiltrating inflammatory cells (CIICs) also affect the cancer cell behavior. To evaluate the significance of TP expression of CIICs in gastric cancer, we assessed TP expression of cancer cells and CIICs separately using immunohistochemical assay on 116 paraffin-embedded tissue samples from stomach cancer patients and investigated their clinical significance. When subjects were divided into 4 groups according to the TP expression: cancer/matrix (+/+), C/M (+/-), C/M (-/+), and C/M (-/-), intratumoral microvessel density scores were higher in the C/M (+/-) group than in the C/M (-/-) group (p=0.02). For lymph node metastasis and survival, there were no significant differences among the 4 groups. However, there were significant differences in survival (p=0.035) and LN metastasis (p=0.023) between the two groups divided by TP expression of CIICs alone irrespective of TP expression of cancer cells. Taken together, this study suggested the TP expression in CIICs could affect lymph node metastasis and patients' survival in gastric cancer.

Role of matrix metalloproteinases in the development of airway inflammation and remodeling

Matrix metalloproteinases (MMPs) are a major group of proteases known to regulate extracellular matrix (ECM) turnover and so they have been suggested to be important in the process of lung disease associated with tissue remodeling. This has led to the concept that modulation of airway remodeling including excessive proteolysis damage to the tissue may be of interest for future treatment. Within the MMP family, macrophage elastase (MMP-12) is able to degrade ECM components such as elastin and is involved in tissue remodeling processes in chronic obstructive pulmonary disease including emphysema. Pulmonary fibrosis has an aggressive course and is usually fatal within an average of 3 to 6 years after the onset of symptoms. Pulmonary fibrosis is associated with deposition of ECM components in the lung interstitium. The excessive airway remodeling as a result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of ECM components could justify anti-protease treatments. Indeed, the correlation of the differences in hydroxyproline levels in the lungs of bleomycin-treated mice strongly suggests that a reduced molar pro-MMP-9/TIMP-1 ratio in bronchoalveolar lavage fluid is associated with collagen deposition, beginning as early as the inflammatory events at day 1 after bleomycin administration. Finally, these observations emphasize that effective treatment of these disorders must be started early during the natural history of the disease, prior to the development of extensive lung destruction and fibrosis.

Macrophage elastase (MMP-12): a pro-inflammatory mediator?

As many metalloproteinases (MMPs), macrophage elastase (MMP-12) is able to degrade extracellular matrix components such as elastin and is involved in tissue remodeling processes. Studies using animal models of acute and chronic pulmonary inflammatory diseases, such as pulmonary fibrosis and chronic obstrutive pulmonary disease (COPD), have given evidences that MMP-12 is an important mediator of the pathogenesis of these diseases. However, as very few data regarding the direct involvement of MMP-12 in inflammatory process in the airways were available, we have instilled a recombinant form of human MMP-12 (rhMMP-12) in mouse airways. Hence, we have demonstrated that this instillation induced a severe inflammatory cell recruitment characterized by an early accumulation of neutrophils correlated with an increase in proinflammatory cytokines and in gelatinases and then by a relatively stable recruitment of macrophages in the lungs over a period of ten days. Another recent study suggests that resident alveolar macrophages and recruited neutrophils are not involved in the delayed macrophage recruitment. However, epithelial cells could be one of the main targets of rhMMP-12 in our model. We have also reported that a corticoid, dexamethasone, phosphodiesterase 4 inhibitor, rolipram and a non-selective MMP inhibitor, marimastat could reverse some of these inflammatory events. These data indicate that our rhMMP-12 model could mimic some of the inflammatory features observed in COPD patients and could be used for the pharmacological evaluation of new anti-inflammatory treatment. In this review, data demonstrating the involvement of MMP-12 in the pathogenesis of pulmonary fibrosis and COPD as well as our data showing a pro-inflammatory role for MMP-12 in mouse airways will be summarized.

Protease-activated receptors and inflammatory hyperalgesia

Recent advances in basic science pointed to a role for proteinases, through the activation of proteinase-activated receptors (PARs) in nociceptive mechanisms. Activation of PAR1, PAR2 and PAR4 either by proteinases or by selective agonists causes inflammation inducing most of the cardinal signs of inflammation: swelling, redness, and pain. Sub-inflammatory doses of PAR2 agonist still induced hyperalgesia and allodynia while PAR2 has been shown to be implicated in the generation of hyperalgesia in different inflammatory models. In contrast, sub-inflammatory doses of PAR1 increases nociceptive threshold, inhibiting inflammatory hyperalgesia, thereby acting as an analgesic agent. PARs are present and functional on sensory neurons, where they participate either directly or indirectly to the transmission and/or inhibition of nociceptive messages. Taken together, the results discussed in this review highlight proteinases as signaling molecules to sensory nerves. We need to consider proteinases and the receptors that are activated by proteinases as important potential targets for the development of analgesic drugs in the treatment of inflammatory pain.

Role of protease-activated receptor-2 in inflammation, and its possible implications as a putative mediator of periodontitis

Proteinase-activated receptor-2 (PAR2) belongs to a novel subfamily of G-protein-coupled receptors with seven-transmembrane domains. This receptor is widely distributed throughout the body and seems to be importantly involved in inflammatory processes. PAR2 can be activated by serine proteases such as trypsin, mast cell tryptase, and bacterial proteases, such as gingipain produced by Porphyromonas gingivalis. This review describes the current stage of knowledge of the possible mechanisms that link PAR2 activation with periodontal disease, and proposes future therapeutic strategies to modulate the host response in the treatment of periodontitis.

Correlation of indices of activity of inflammatory joint disease with nucleoside triphosphate pyrophosphohydrolase

Osteoarthritis [OA] and rheumatoid arthritis [RA] are the most common diseases affecting the joints. Up till now, good understanding of their pathology and a specific diagnostic laboratory abnormality is required. In recent years the role of the enzyme nucleoside triphosphate pyrophosphohydrolase [NTPPase] has been clarified. In the present study, the activity levels of this enzyme in the serum, plasma and urine were determined in 32 patients with bilateral knee OA as well as 18 patients with RA together with 10 healthy subjects comparable in age to patients representing a control group. Meanwhile, serum hyaluronan and sialic acid levels were determined in all participants. The study revealed significantly increased levels of NTPPase in the sera, plasma and urine of patients with knee OA and RA as compared to controls. The activity levels were significantly higher in the sera, plasma and urine of patients with knee OA as compared to RA. No differences in the enzymatic activity could be observed between plasma and serum enzyme activity, ruling out the participation of platelets as a source of this enzyme. The increased activity levels in OA and RA could originate from an accelerated proteolysis associated with inflammatory arthritis, accompanied with enhanced lymphatic clearance from the affected joints with release of soluble degradation products into the blood. Meanwhile, the significantly higher enzymatic activity levels in OA as compared with RA could indicate different inflammatory mechanisms. Serum levels of hyaluronan and sialic acid were significantly increased in either OA or Ra as compared with controls but the levels were significantly higher in RA when compared with OA. The levels of all indices studied increased with the duration of knee OA and RA, but the differences were significant only in OA. The levels also reflected X-ray grading in either OA or RA. Significant positive correlations existed between serum and NTPPase with hyaluronic acid and sialic acid. In conclusion, the present study further clarified the differences in pathological nature between OA and RA as evidenced by significantly higher NTPPase in OA compared with RA but significantly increased hyaluronan and sialic acid in RA as compared with OA. Therefore, therapeutic interventions are totally different in the 2 conditions. The severity of RA can be predicted better from hyaluronan and sialic acid while OA from NTPPase

Role of human placental extract on succinic dehydrogenase activity in carrageenin-induced edema in rats in vivo and its effect on erythrocyte lysis, platelet aggregation and trypsin activity in vitro.

Significant increase of liver succinic dehydrogenase (SDH, EC 1.3.99.1) activity was produced by carrageenin-induced edema in rats. Pretreatment with human placental extract inhibited the increased liver SDH activity in a dose-dependent manner. Placental extract was found to have little or no effect on the liver SDH activity in normal rats. Furthermore, heat-induced erythrocyte lysis was inhibited to a substantial extent by the extract and was found to be dose-responsive. However, adenosine diphosphate (ADP)-induced platelet aggregation and trypsin activity were not changed by the placental extract in vitro. The study indicates that the membrane stabilization and depletion of adenosine triphosphate (ATP) synthesis may contribute to antiinflammatory effect of the extract.