Activation Of Proinflammatory Transcription Factor Research Articles

Antioxidant activity of carvedilol in cardiovascular disease

Oxidative and inflammatory stresses are cardinal in the pathogenesis of hypertension and atherosclerosis. Oxidative stress also leads to the induction of inflammation through the activation of proinflammatory transcription factors. Understanding the mechanisms leading to oxidative stress and the means of suppressing it are important in controlling complications related to atherogenesis, since oxidative and inflammatory stress are important in the pathogenesis of atherosclerosis. The failure of chemical antioxidants [which scavenge reactive oxygen species (ROS)], such as vitamins E and C, has led to further exploration of the ROS-suppressive effects of drugs used in the treatment of cardiovascular disease. Carvedilol has been shown to possess both ROS-scavenging and ROS-suppressive effects, and its use is associated with a reduction in oxidative stress. Furthermore, anti-inflammatory effects of carvedilol have now been described. Although further clinical investigations are required, these properties may contribute to the improvement in clinical outcomes observed with carvedilol.

Cause-effect relationships between zymogen activation and other early events in secretagogue-induced acute pancreatitis

We have hypothesized that the colocalization of digestive zymogens with lysosomal hydrolases, which occurs during the early stages of every experimental pancreatitis model, facilitates activation of those zymogens by lysosomal hydrolases such as cathepsin B and that this activation triggers acute pancreatitis by leading to acinar cell injury. Some, however, have argued that the colocalization phenomenon may be the result, rather than the cause, of zymogen activation during pancreatitis. To resolve this controversy and explore the causal relationships between zymogen activation and other early pancreatitis events, we induced pancreatitis in mice by repeated supramaximal secretagogue stimulation with caerulein. Some animals were pretreated with the cathepsin B inhibitor CA-074 me to inhibit cathepsin B, prevent intrapancreatic activation of digestive zymogens, and reduce the severity of pancreatitis. We show that inhibition of cathepsin B by pretreatment with CA-074 me prevents intrapancreatic zymogen activation and reduces organellar fragility, but it does not alter the caerulein-induced colocalization phenomenon or subcellular F-actin redistribution or prevent caerulein-induced activation of NF-kappaB, ERK1/2, and JNK or upregulated expression of cytochemokines. We conclude 1) that the colocalization phenomenon, F-actin redistribution, activation of proinflammatory transcription factors, and upregulated expression of cytochemokines are not the results of zymogen activation, and 2) that these early events in pancreatitis are not dependent on cathepsin B activity. In contrast, zymogen activation and increased subcellular organellar fragility during caerulein-induced pancreatitis are dependent on cathepsin B activity.

Regulation of Polymorphonuclear Leukocyte-Intestinal Epithelial Cell Interactions: Signalling Events and Potential Drug Targets

A crucial event in the inflammatory response is recruitment of polymorphonuclear leukocytes (PMNL) to a site of infection or injury. PMNL-epithelial interactions involve many fundamental cell processes, including adhesion, migration, secretion, phagocytosis and apoptosis. Thus, migration of PMNL across epithelial-lined organs is a primary event component of host defense. Moreover, PMNL transepithelial migration often results in disease symptoms. New insights into leukocyte-epithelial signalling mechanisms have emerged that are beginning to shed light on the role of many molecular interactions in regulating the rate of PMNL transepithelial migration. Knowledge of the basic mechanisms that control the activation of pro-inflammatory transcription factors, and how these innate immune signalling pathways lead to an activation of the adaptative immune response that maintains the chronically inflamed state, is essential for pharmacological manipulation of intestinal inflammation. This review highlights recent advances in our understanding of the different mechanisms of PMNL-epithelial cell adhesive interactions at the level of cell surface protein-protein binding events, and in intracellular signal transduction pathways that regulate the PMNL transepithelial migration. Finally, the potential modulation of these different signal pathways as possible therapeutic goals will be discussed. Keywords: Intestinal epithelial cell, neutrophil, signalling, drugs, large bowel, Crohn'disease, ulcerative colitis, idiopathic inflammatory bowel diseases

Melagatran Reduces Advanced Atherosclerotic Lesion Size and May Promote Plaque Stability in Apolipoprotein E– Deficient Mice

Inflammatory mechanisms are involved in atherosclerotic plaque rupture and subsequent thrombin formation. Thrombin not only plays a central role in thrombus formation and platelet activation, but also in the induction of inflammatory processes. We assessed the hypothesis that melagatran, a direct thrombin inhibitor, attenuates plaque progression and promotes stability of advanced atherosclerotic lesions. Melagatran (500 micromol/kg/d) or control diet was administered to apolipoprotein E-deficient mice (n=54) with advanced atherosclerotic lesions. Treatment reduced lesion progression in brachiocephalic arteries (P<0.005). Morphometric analysis confirmed that thrombin inhibition promoted plaque stability and resulted in thicker fibrous caps (28.4+/-14.2 microm versus 20.8+/-12.0 microm; P<0.05), increased media thickness (29.3+/-9.6 microm versus 24.4+/-6.7 microm; P<0.05), and smaller necrotic cores (73,537+/-41,301 microm2 versus 126,819+/-51,730 microm2; P<0.0005). Electro mobility shift assays revealed reduced binding activity of nuclear factor kappaB (P<0.05) and activator protein-1 (P<0.05) in aortas of treated mice. Furthermore, immunohistochemistry demonstrated reduced staining for matrix metalloproteinase (MMP)-9 (P<0.05). Melagatran had no significant effect on early lesion formation in C57BL/6J mice. The direct thrombin inhibitor melagatran reduces lesion size and may promote plaque stability in apolipoprotein E-deficient mice, possibly through reduced activation of proinflammatory transcription factors and reduced synthesis of MMP-9.

P-852: Hyperglycemia stimulates proatherogenic inflammation pathways in polycystic ovary syndrome

Activation of the proinflammatory transcription factors activator protein-1 (AP-1) and early growth response-1 (EGR-1) culminate in the transcription of tissue factor (TF) and metalloproteinase-2 (MMP-2), respectively. Atherosclerotic plaque rupture and thrombosis are promoted in the process. We examined the effect of glucose challenge on AP-1 activation and proinflammatory, proatherogenic protein expression in mononuclear cells (MNC) of women with Polycystic Ovary Syndrome (PCOS) compared to ovulatory controls, and the relationship of this effect with body composition.

Long term environmental tobacco smoke activates nuclear transcription factor-kappa B, activator protein-1, and stress responsive kinases in mouse brain

Environmental tobacco smoke (ETS) is a key mediator of several diseases. Tobacco smoke contains a mixture of over 4700 chemical components many of which are toxic and have been implicated in the etiology of oxidative stress related diseases such as chronic obstructive pulmonary disease, Parkinson's disease, asthma, cancer and cardiovascular disease. However, the mechanism of action of cigarette smoke in the onset of these diseases is still largely unknown. Previous studies have revealed that the free radicals generated by cigarette smoke may contribute to many of these chronic health problems and this study sought to address the role of environmental tobacco smoke in oxidative stress related damage in different regions of the mouse brain. In this study, male mice were exposed for 7 h/day, 7 days/week, for 6 months. Our results show that tobacco smoke led to increased generation of reactive oxygen species with an increase in NF-κB activation. Gel shift analysis also revealed the elevated level of the oxidative stress sensitive proinflammatory nuclear transcription factor-kappa B and activator protein-1 in different regions of the brain of cigarette smoke exposed mice. Tobacco smoke led to activation of COX-2 in all the regions of the brain. Activation of mitogen activated protein kinase and c-Jun N-terminal kinase were also observed in various regions of brain of ETS exposed mice. Overall our results indicate that exposure to long-term cigarette smoke induces oxidative stress leading to activation of stress induced kinases and activation of proinflammatory transcription factors.

The human cytomegalovirus-encoded receptor US28 increases the activity of the major immediate-early promoter/enhancer

The activation of the major immediate-early promoter (MIEP) is a key event in the cytomegalovirus replication cycle and is dependent on cellular transcription factors which are partially activated by viral proteins. Expression of the viral chemokine receptor homolog US28 results in constitutive activation of pro-inflammatory transcription factors that may be involved in the activation of the major immediate-early promoter/enhancer. Using reporter gene assays in human embryonic kidney cells, we found that US28 signaling was responsible for increased major immediate-early promoter/enhancer activity which was independent of β-chemokine binding. Inhibition of nuclear factor-κB (NF-κB) only partially blocked the effect of US28, whereas treatment with a specific p38 mitogen activated kinase (MAPK) inhibitor fully abrogated the US28-induced enhancement of promoter activity. Our results suggest that during human cytomegalovirus (HCMV) infection, US28 in epithelial cells transactivates the major immediate-early promoter/enhancer via the activation of p38 MAPK and downstream signaling that partially involves NF-κB.

Are transcription factors NF-κB and AP-1 involved in the ANG II-stimulated production of proinflammatory cytokines induced by LPS in dehydrated rats?

We recently reported an involvement of ANG II and the ANG II type 1 (AT1) receptor in the hepatic expression of IL-1beta induced in dehydrated rats by LPS. Here, we first confirmed that ANG II and AT1 receptors contribute to the LPS-induced increase in the splenic concentration of IL-1beta in dehydrated rats. We then investigated whether ANG II contributes to IL-1 production through a modulating effect on the activation of proinflammatory transcription factors (NF-kappaB and AP-1) that is induced in the dehydrated rat's liver and spleen by intravenous injection of LPS. Surprisingly, LPS markedly increased the hepatic activation of NF-kappaB, an effect that was significantly enhanced (rather than reduced) by pretreatment with an ANG-converting-enzyme (ACE) inhibitor or AT1-receptor antagonist. Furthermore, the same ACE inhibitor and AT1-receptor antagonist each increased the resting NF-kappaB activity in the liver and spleen, although they had no effect on the LPS-induced splenic expression of NF-kappaB. Both hepatic and splenic AP-1 expressions were enhanced by LPS. This response was significantly augmented by pretreatment with the AT1-receptor antagonist (but not with the ACE inhibitor) in the spleen, while in the liver, neither drug had any effect. These results suggest that the endogenous ANG II or AT1 receptor suppresses the activation of hepatic or splenic transcription factors in dehydrated rats given LPS. Our results seem not to support the idea that NF-kappaB and AP-1 play key roles in the ANG II-induced enhancement of the production of proinflammatory cytokines that is induced by LPS in dehydrated rats.

Protective Effect of Endotoxin Preconditioning in Pancreas: Analysis With DNA Chip Arrays

Recently we demonstrated a protective effect of endotoxin preconditioning 24 hours before pancreatic ischemia-reperfusion injury, which has also been described for other organs. The mechanisms underlying this phenomenon, such as differential gene expression, are poorly investigated. We chose to approach this question by investigating differential gene expression in the rat pancreas over the time course of endotoxin pretreatment. Male Wistar rats (5 groups, 5 animals per group) were pretreated with endotoxin intraperitoneally (1 mg/kg of body weight). After treatment at 30 minutes, and at 3 and 24 hours the pancreas was removed. Untreated animals and animals with injection of saline solution served as controls. After RNA isolation, RNA was pooled and hybridized to Affymetrix chips to measure the relative mRNA levels of 7000 genes and 1000 expression sequence tags. Three hours after administration of endotoxin there was an activation of proinflammatory transcription factors and other proinflammatory genes. After 24 hours there was a clear decrease of these proinflammatory genes, but a remaining and increasing upregulation of important antiapoptotic genes, antiproteases, and other probably protective genes. There was also a significant upregulation of complement factors. It was surprising that heat-shock proteins and other typical immediate early genes of the AP-1 complex were not upregulated. Our data show that 24 hours after endotoxin stress there is a regulation of a network of genes that represents a multifaceted preconditioning. As most important factors, inhibition of apoptosis and antiproteatic strategies are identified. Heat-shock proteins seem to play no important role in the mechanism of endotoxin preconditioning.

Asthma and cigarette smoking

In most developed countries approximately 25% of adults with asthma are current cigarette smokers. Asthma and active cigarette smoking interact to cause more severe symptoms, accelerated decline in lung function, and impaired short-term therapeutic response to corticosteroids. Cigarette smoking may modify inflammation that is associated with asthma, although there is limited published data on airway pathology in smokers with asthma. To date, the evidence points towards a combination of both heightened and suppressed inflammatory responses in smokers compared with nonsmokers with asthma. The mechanisms of corticosteroid resistance in asthmatic smokers are unexplained, but could be as a result of alterations in airway inflammatory cell phenotypes (e.g. increased neutrophils or reduced eosinophils), changes in the glucocorticoid receptor-alpha to -beta ratio (e.g. overexpression of glucocorticoid receptor beta), and increased activation of pro-inflammatory transcription factors (e.g. nuclear factor-kappaB) or reduced histone deacetylase activity. In conclusion, every effort should be made to encourage asthmatics who smoke to stop, although the effects of smoking cessation upon reversing the adverse effects of tobacco smoke on asthma control, therapeutic response to corticosteroids and airway pathology have yet to be fully elucidated. Alternative or additional therapies to inhaled corticosteroids are needed for asthmatic patients who are unable to quit smoking.

Mechanical stretch activates nuclear factor‐kappaB, activator protein‐1, and mitogen‐activated protein kinases in lung parenchyma: implications in asthma

We investigated the effects of mechanical stretch and induced stimulation of lung parenchyma on the activation of proinflammatory transcription factors in normal mice and in a mouse model of asthma. Mechanical stretching of lung parenchyma led to increased activation of NF-kappaB and AP-1 transcription factors. Incubation of lung parenchyma with methacholine increased the activation of NF-kappaB, which was further augmented by stretch. Activation of NF-kappaB in response to mechanical stretch was associated with the phosphorylation and degradation of IkappaBalpha and the activation of IkappaB kinase. Stretch-induced activation of NF-kappaB involves activation of stretch-activated (SA) channels and the production of free radicals. Mechanical stretch and/or treatment with methacholine resulted in an increased activation of ERK1/2 and p38 MAP kinase, and the inhibition of the activity of these kinases partially blocked the stretch-induced NF-kappaB and AP-1 activation. A greater level of NF-kappaB and ERK1/2 activity was observed in the asthmatic mice, which was further increased by mechanical stretching. The level of cyclooxygenase-2, an NF-kappaB-regulated enzyme, was also higher in lung parenchyma from asthmatic mice than in normal mice. Our data suggest that mechanical stretching of lung parenchyma activates NF-kappaB and AP-1, at least in part, through the activation of MAP kinase signaling pathways.

Identification of a functional peroxisome proliferator-activated receptor response element in the rat catalase promoter.

Peroxisomal proliferator-activated receptor (PPAR)gamma has been shown to decrease the inflammatory response via transrepression of proinflammatory transcription factors. However, the identity of PPARgamma responsive genes that decrease the inflammatory response has remained elusive. Because generation of the reactive oxygen species hydrogen peroxide (H(2)O(2)) plays a role in the inflammatory process and activation of proinflammatory transcription factors, we wanted to determine whether the antioxidant enzyme catalase might be a PPARgamma target gene. We identified a putative PPAR response element (PPRE) containing the canonical direct repeat 1 motif, AGGTGA-A-AGTTGA, in the rat catalase promoter. In vitro translated PPARgamma and retinoic X receptor-alpha proteins were able to bind to the catalase PPRE. Promoter deletion analysis revealed that the PPRE was functional, and a heterologous promoter construct containing a multimerized catalase PPRE demonstrated that the PPRE was necessary and sufficient for PPARgamma-mediated activation. Treatment of microvascular endothelial cells with PPARgamma ligands led to increases in catalase mRNA and activity. These results demonstrate that PPARgamma can alter catalase expression; this occurs via a PPRE in the rat catalase promoter. Thus, in addition to transrepression of proinflammatory transcription factors, PPARgamma may also be modulating catalase expression, and hence down-regulating the inflammatory response via scavenging of reactive oxygen species.

Parenchymal cell apoptosis as a signal for sinusoidal sequestration and transendothelial migration of neutrophils in murine models of endotoxin and Fas-antibody-induced liver injury.

Endotoxin (ET) induces neutrophil sequestration in hepatic sinusoids, the activation of proinflammatory transcription factors (nuclear factor KB [NF-kappaB]) with up-regulation of adhesion molecules on sinusoidal endothelial cells and hepatocytes. However, if galactosamine (Gal) is co-administered with ET, neutrophils transmigrate and attack parenchymal cells. This suggests that a signal from parenchymal cells triggers neutrophil transmigration. In this study, we tested the hypothesis that parenchymal cell apoptosis may induce neutrophil transendothelial migration in the Gal/ET model. Treatment of C3Heb/FeJ mice with 700 mg/kg Gal and 100 microg/kg ET induced tumor necrosis factor alpha (TNF-alpha) formation (13.25 +/- 0.75 ng/mL) and hepatic NF-kappaB activation at 90 minutes; the generation of the C-X-C chemokine KC (2.86 +/- 0.30 ng/mL at 5 hours); sinusoidal neutrophil sequestration (380 +/- 21 polymorphonuclear leukocytes/50 high-power fields) and apoptosis (925% +/- 29% increase of DNA fragmentation; and a 45-fold increase of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells) at 6 hours, followed by transmigration of neutrophils and development of substantial necrosis (38% +/- 3% of hepatocytes; alanine transaminase [ALT]: 1,500 +/- 300 U/L) at 7 hours. Administration of uridine (1,000 mg/kg) did not reduce plasma levels of TNF-alpha and KC, NF-kappaB activation, or polymorphonuclear leukocyte sequestration, but attenuated apoptosis by 90% to 94%. In these livers, neutrophils did not transmigrate and liver injury was prevented (necrosis: < 5%; ALT: 40 +/- 3 U/L). However, massive apoptosis and liver injury initiated by the anti-Fas antibody, Jo2, did not recruit neutrophils into the liver. We conclude that excessive parenchymal cell apoptosis represents an important signal for transmigration of primed neutrophils sequestered in sinusoids during endotoxemia in vivo. However, apoptosis per se does not cause neutrophil sequestration in the liver vasculature.