Inhibition of p38 MAP kinase- and RICK/NF-kappaB-signaling suppresses inflammatory bowel disease

Inhibition of p38 mitogen-activated protein kinase impairs influenza virus-induced primary and secondary host gene responses and protects mice from lethal H5N1 infection

Highly pathogenic avian influenza viruses (HPAIV) induce severe inflammation in poultry and men. One characteristic of HPAIV infections is the induction of a cytokine burst that strongly contributes to viral pathogenicity. This cell-intrinsic hypercytokinemia seems to involve hyperinduction of p38 mitogen-activated protein kinase. Here we investigate the role of p38 MAPK signaling in the antiviral response against HPAIV in mice as well as in human endothelial cells, the latter being a primary source of cytokines during systemic infections. Global gene expression profiling of HPAIV-infected endothelial cells in the presence of the p38-specific inhibitor SB 202190 revealed that inhibition of p38 MAPK leads to reduced expression of IFNβ and other cytokines after H5N1 and H7N7 infection. More than 90% of all virus-induced genes were either partially or fully dependent on p38 signaling. Moreover, promoter analysis confirmed a direct impact of p38 on the IFNβ promoter activity. Furthermore, upon treatment with IFN or conditioned media from HPAIV-infected cells, p38 controls interferon-stimulated gene expression by coregulating STAT1 by phosphorylation at serine 727. In vivo inhibition of p38 MAPK greatly diminishes virus-induced cytokine expression concomitant with reduced viral titers, thereby protecting mice from lethal infection. These observations show that p38 MAPK acts on two levels of the antiviral IFN response. Initially the kinase regulates IFN induction and, at a later stage, p38 controls IFN signaling and thereby expression of IFN-stimulated genes. Thus, inhibition of MAP kinase p38 may be an antiviral strategy that protects mice from lethal influenza by suppressing excessive cytokine expression.

Oleuropein protects against dextran sodium sulfate-induced chronic colitis in mice

The anti-inflammatory effect of oleuropein (1), the major phenolic secoiridoid in Olea europaea, was evaluated in an experimental model of chronic colitis in mice. Animals were exposed to four repeated cycles of dextran sodium sulfate in drinking water followed by a 7-day rest period. Animals receiving a standard diet supplemented with 0.25% of 1 (equivalent to 500 mg/kg/day) for 56 days exhibited a decrease of inflammatory symptoms, as reflected by improvement of disease activity index and histopathological changes. It was found that 1 decreased inflammatory cell recruitment and the release of inflammatory cytokines interleukin (IL)-1β and IL-6 with increased IL-10 levels in colon tissue. Colon expression of cyclooxygenase-2 and inducible nitric oxide synthase was reduced significantly by 1. The anti-inflammatory molecular mechanism of 1 was associated with the suppression of the phosphorylation of p38 mitogen-activated protein kinase and might be mediated by up-regulation of annexin A1. In addition, 1 ameliorated intestinal wound healing in IEC-18 monolayers. Therefore, oleuropein seems to be a promising active molecule in experimental ulcerative colitis.

RIP2 activity in inflammatory disease and implications for novel therapeutics

The role of NOD2 and RIP2 in inflammatory disease has been paradoxical. Whereas loss-of-function NOD2 polymorphisms cause CD, a granulomatous disease of the gastrointestinal tract, gain-of-function mutations cause EOS-a granulomatous disease primarily affecting the skin, joints, and eyes. Thus, gain-of-function mutations and loss-of-function polymorphisms cause granulomatous inflammatory disease, only in different anatomic locations. The situation is complicated further by the fact that WT NOD2 and WT RIP2 activity has been implicated in diseases such as asthma, inflammatory arthritis and MS. This article reviews the role that the NOD2:RIP2 complex plays in inflammatory disease, with an emphasis on the inhibition of this signaling pathway as a novel pharmaceutical target in inflammatory disease.

Flavonoid naringenin: a potential immunomodulator for Chlamydia trachomatis inflammation

Chlamydia trachomatis, the agent of bacterial sexually transmitted infections, can manifest itself as either acute cervicitis, pelvic inflammatory disease, or a chronic asymptomatic infection. Inflammation induced by C. trachomatis contributes greatly to the pathogenesis of disease. Here we evaluated the anti-inflammatory capacity of naringenin, a polyphenolic compound, to modulate inflammatory mediators produced by mouse J774 macrophages infected with live C. trachomatis. Infected macrophages produced a broad spectrum of inflammatory cytokines (GM-CSF, TNF, IL-1β, IL-1α, IL-6, IL-12p70, and IL-10) and chemokines (CCL4, CCL5, CXCL1, CXCL5, and CXCL10) which were downregulated by naringenin in a dose-dependent manner. Enhanced protein and mRNA gene transcript expressions of TLR2 and TLR4 in addition to the CD86 costimulatory molecule on infected macrophages were modulated by naringenin. Pathway-specific inhibition studies disclosed that p38 mitogen-activated-protein kinase (MAPK) is involved in the production of inflammatory mediators by infected macrophages. Notably, naringenin inhibited the ability of C. trachomatis to phosphorylate p38 in macrophages, suggesting a potential mechanism of its attenuation of concomitantly produced inflammatory mediators. Our data demonstrates that naringenin is an immunomodulator of inflammation triggered by C. trachomatis, which possibly may be mediated upstream by modulation of TLR2, TLR4, and CD86 receptors on infected macrophages and downstream via the p38 MAPK pathway.

The impact of JNK inhibitor D-JNKI-1 in a murine model of chronic colitis induced by dextran sulfate sodium

Purpose:

The c-Jun N-terminal kinases (JNK) are involved in the activation of T cells and the synthesis of proinflammatory cytokines. Several studies have established the relevance of the JNK pathway in inflammatory bowel diseases. The present study analyzed the therapeutic effect of D-JNKI-1, a specific JNK-inhibiting peptide, in a low-dose dextran sulfate sodium (DSS) model of chronic colitis.

Methods:

DSS colitis was induced in female C57/BL6 mice by cyclic administration using different concentrations of DSS (1.0% and 1.5%). Mice in the intervention groups received subcutaneous administration of 1 μg/kg D-JNKI-1 on days 2, 12, and 22. They were monitored daily to assess the severity of colitis, body weight, stool consistency, and the occurrence of occult blood or gross rectal bleeding using evaluation of the disease activity index. The animals were sacrificed after 30 days, and the inflamed intestine was histologically evaluated using a crypt damage score. Immunohistochemical quantification of CD4⁺ and CD8⁺ cells was also carried out.

Results:

Administration of 1 μg/kg D-JNKI-1 resulted in a significant decrease in the disease activity index (P = 0.013 for 1.0% DSS; P = 0.007 for 1.5% DSS). As a mild form of colitis was induced, histological examination did not show any distinct damage to the mucosa and crypts. However, expression of CD4⁺ and CD8⁺ cells was reduced in mice treated with D-JNKI-1 (not significant).

Conclusion:

Administration of D-JNKI-1 resulted in a clinical attenuation of chronic DSS colitis, and a therapeutic effect of D-JNKI-1 must therefore be assumed. The decrease in CD4⁺ and CD8⁺ cells may reflect the influence of D-JNKI-1 on T-cell activation, differentiation, and migration.

Glutamine on Intestinal Inflammation: A Mechanistic Perspective

Intestinal inflammation is associated with various pathological diseases, such as gastritis from Helicobacter pylori infection, Crohn's and colitis in inflammatory bowel disease, and colorectal cancer. Thus, treatment with anti-inflammatory substances in these inflammation-associated diseases is critical. Increasingly compelling evidence indicates that glutamine is an anti-inflammatory compound candidate because it can influence the long-term outcome of the inflammatory diseases with in a low-risk way. However, before recommending its use in clinical practice, it is important to elucidate the molecular mechanism by which glutamine exerts its roles in modulating intestinal inflammation. In this study, we review the current knowledge on the detailed regulation pathway used by glutamine in its proinflammatory regulation, with a special emphasis on intestinal inflammation. These regulation pathways include nuclear factor kappa B (NF-κB), signal transducer and activator of transcription (STAT), mitogen-activated protein kinases (MAPK), phosphoinositide-3-kinases (PI3K)/PI3K-protein kinase B (Akt), activating protein-1 (AP-1), nitric oxide synthases (NOS)-nitric oxide (NO), peroxisome proliferator-activated receptor-Γ (PPARγ), heat shock factor-1 (HSF-1)- heat shock proteins (HSP) and glutathione (GSH) - reactive oxygen species (ROS). Although some regulatory pathways, such as PI3K/PI3K-Akt, GSH-ROS and AP-1, need to be further investigated, this review provides useful information to utilize glutamine as an immunonutritional or pharmaconutritional drug, not only for inflammation-associated diseases in the intestine, but also possibly for other inflammatory-associated diseases, i.e. arthritis, asthma, type 2 diabetes, etc.

Pharmacological inhibition of p38 mitogen-activated protein kinases affects KC/CXCL1-induced intraluminal crawling, transendothelial migration, and chemotaxis of neutrophils in vivo

p38 mitogen-activated protein kinase (MAPK) signalling is critical in the pathophysiology of a variety of inflammatory processes. Leukocyte recruitment to the site of inflammation is a multistep process governed by specific signalling cascades. After adhesion in the lumen, many leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac-1-dependent manner. The signalling mechanisms that regulate postadhesion steps of intraluminal crawling, transmigration, and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various parameters of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient. Neutrophil-endothelial interactions in microvasculature of murine cremaster muscle were determined using intravital microscopy and time-lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, and transmigration and impaired the initiation of neutrophil crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac-1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.

Inhibition of p38/Mk2 signaling pathway improves the anti-inflammatory effect of WIN55 on mouse experimental colitis

P38/Mk2 (mitogen-activated protein kinase (MAPK)-activated protein kinase-2, also known as MAKAP kinase-2) is a member of the mitogen-activated protein kinases (MAPKs) family, and participates in inflammatory responses directly or indirectly. WIN55, 212-2 (WIN55) is a synthetic non-selective agonist of cannabinoid (CB) receptors with remarkable anti-inflammatory properties. This study was to explore the roles of WIN55 and p38/Mk2 signaling pathway in dextran sodium sulfate (DSS)-induced mouse colitis and ascertain their anti-inflammatory mechanisms. Colitis was induced in C57BL Mk2 gene homozygous deletion (Mk2-/-) and wild-type mice by replacing the drinking water with 4% DSS solution for 7 days. DSS-treated mice developed bloody stool, weight loss, and eye-visible multiple bleeding ulcers on colon mucosa. The mRNA expressions levels of TNF-α and IL-6, as well as the protein levels of p38 and its phosphorylated form (p-p38), were upregulated in the colon. The plasma levels of TNF-α, IL-6, cytokine-induced neutrophil chemoattractant-1 (CINC-1), monocyte chemoattractant protein-1 (MCP-1), and lung myeloperoxidase (MPO) activities were raised; however, all these changes were less severe in Mk2-/- mice. After WIN55 intervention, the Mk2-/- mice recovered faster and better from the induced colitis than their wild-type counterparts. The results indicate that the Mk2 homozygous deletion in mice impedes the induction of experimental colitis by DSS, confirming the notion that p38/Mk2 is involved in this inflammatory response. WIN55 protects mice against DSS-induced colitis, in particular when the p38/Mk2 pathway is obstructed, implying that the activation of CB system, together with blocking of p38/Mk2 pathway, serves as a potential drug target for colitis treatment.

Knockout of the c-Jun N-terminal Kinase 2 aggravates the development of mild chronic dextran sulfate sodium colitis independently of expression of intestinal cytokines TNFα, TGFB1, and IL-6

Introduction

The c-Jun N-terminal kinases (JNKs) are involved in signal transduction of inflammatory bowel diseases. The aim of this study was to examine the function of JNKs by using a low-dose dextran sulfate sodium (DSS) model in JNK1 knockout mice (Mapk8−/−), JNK2 knockout mice (Mapk9−/−), and wild-type controls (WT1, WT2).

Methods

The animals were evaluated daily using a disease activity index. After 30 days, the intestine was evaluated histologically with a crypt damage score. CD4+ and CD8+ cells were quantified using immunofluorescence. Analysis of tumor necrosis factor-α (TNFα), interleukin-6 (IL-6), and transforming growth factor β1 (TGFB1) expression was carried out using LightCycler^® real-time polymerase chain reaction.

Results

Cyclic administration of low-dose DSS (1%) was not able to induce features of chronic colitis in Mapk8−/− WT2 mice. By contrast, DSS administration significantly increased the disease activity index in WT1 and Mapk9−/− mice. In Mapk9−/− mice, the crypt damage score and the number of CD4+ and CD8+ cells as features of chronic colitis/inflammation were also significantly elevated. Expression of TNFα, IL-6, and TGFB1 was not altered by the JNK knockout.

Conclusion

Administering DSS at a defined low concentration that is unable to induce colitis in WT animals leads to clinically and histologically detectable chronic colitis in Mapk9−/− mice. The reason for this disease-inducing effect resulting from the loss of JNK2 remains to be elucidated. Expression of TNFα, IL-6, and TGFB1 does not appear to be involved; proapoptotic JNK2 may prolong the activity of proinflammatory immune cells, leading to perpetuation of the inflammation.

Clinical use and mechanisms of infliximab treatment on inflammatory bowel disease: a recent update

The pathogenesis and treatment of inflammatory bowel disease (IBD) have been recently advanced, while it is still challenged with high morbidity and poor prognosis. Infliximab, a monoclonal antibody of tumor necrosis factor (TNF), has emerged as an efficient treatment with many clinical benefits such as quick disease activity reduction and IBD patient life quality improvement. However, the biological effects of infliximab on IBD need to be elucidated. This paper reviewed the clinical use and recently advanced biological action of infliximab on IBD. By forming the stable complex with the soluble or the membrane form of TNF in fluid environment or on cell surface of immune cell, fibroblast, endothelium, and epithelium, infliximab quenches TNF activity and performs the important biological actions which lead to amelioration and remission of immune responses. The mechanisms of infliximab treatment for IBD were intensively discussed. The recent advances on two topics including predictors and side effects of infliximab treatment were also reviewed.

Dietary extra virgin olive oil polyphenols supplementation modulates DSS-induced chronic colitis in mice

We evaluated the protective effect of dietary extra virgin olive oil (EVOO) polyphenol extract (PE) supplementation in the inflammatory response associated to chronic colitis model. Six-week-old mice were randomized in four dietary groups: standard diet (SD), EVOO diet and both enriched with PE (850 ppm) (SD+PE and EVOO+PE). After 30 days, animals that were exposed to dextran sodium sulfate (DSS) (3%) followed by 3 weeks of drinking water developed chronic colitis, which was evaluated by disease activity index (DAI) and histology. Cell proliferation was analyzed by immunohistochemical and changes in monocyte chemotactic protein (MCP)-1 and tumor necrosis factor (TNF)-α mRNA expression by quantitative real-time polymerase chain reaction. Colonic expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, mitogen-activated protein kinases (MAPKs), IκBα inhibitory and peroxisome proliferator-activated receptor gamma (PPARγ) were determined by western blotting. SD-DSS group showed a significant increase of DAI, histological damage and cell proliferation, as well as an up-regulation of TNF-α, MCP-1, COX-2 and iNOS proteins. p38 and JNK MAPKs phosphorylation, IκBα degradation and PPARγ deactivation were also observed. However, in DSS-treated and EVOO+PE-fed mice, DAI and cell proliferation were significantly reduced, as well as MCP-1, TNF-α, COX-2 and iNOS expression levels. In addition, this dietary group, notably down-regulated JNK phosphorylation, prevented IκBα degradation and PPARγ deactivation. These results demonstrated, for the first time, that EVOO-PE supplementation possessed marked protective effects on experimental colitis through PPARγ up-regulation and nuclear transcription factor-kappa B and MAPK signaling pathway inhibition, decreasing the inflammatory cascade. We concluded that PE-enriched EVOO diet could be a beneficial functional food on ulcerative colitis.

Attenuated expression of the tight junction proteins is involved in clopidogrel-induced gastric injury through p38 MAPK activation

Bleeding complications and delayed healing of gastric ulcer associated with use of clopidogrel is a common clinical concern; however, the underlying mechanisms remain to be determined. This study aimed to clarify whether clopidogrel could cause the damage of the human gastric epithelial cells and to further elucidate the mechanisms involved. After human gastric epithelial cell line GES-1 had been treated with clopidogrel (0.5-2.5 mM), the cell proliferation was examined by MTT assay, apoptosis was measured with DAPI staining and flow cytometry analysis, and the barrier function of the tight junctions (TJ) was evaluated by permeability measurement and transmission electron microscopy. Moreover, expression of the TJ proteins occludin and ZO-1 and the phosphorylation of the mitogen-activated protein kinases (MAPK) p38, ERK, and JNK were examined by western blot. In addition, three MAPK inhibitors specific to p38, ERK and JNK were used, respectively, to verify the signaling pathways responsible for regulating the expression of the TJ proteins being tested. Results showed that clopidogrel significantly increased dextran permeability, induced apoptosis, suppressed GES-1 cell viability, and reduced the expression of the TJ proteins (occludin and ZO-1), acting through p38 MAPK phosphorylation. Furthermore, these observed effects were partially abolished by SB-203580 (a p38 MAPK inhibitor), rather than by either U-0126 (an ERK inhibitor) or SP-600125 (a JNK inhibitor), suggesting that clopidogrel-induced disruption in the gastric epithelial cells is mediated by the p38 MAPK pathway. It is concluded that attenuated expression of the TJ proteins occludin and ZO-1 in human gastric epithelial cells could be involved in clopidogrel-induced gastric mucosal injury through activation of the p38 MAPK pathway.

Murine cytomegalovirus (MCMV) infection upregulates P38 MAP kinase in aortas of Apo E KO mice: a molecular mechanism for MCMV-induced acceleration of atherosclerosis

Multiple studies suggest an association between cytomegalovirus (CMV) infection and atherogenesis; however, the molecular mechanisms by which viral infection might exacerbate atherosclerosis are not well understood. Aortas of MCMV-infected and uninfected Apo E knockout (KO) mice were analyzed for atherosclerotic lesion development and differential gene expression. Lesions in the infected mice were larger and showed more advanced disease compared to the uninfected mice. Sixty percent of the genes in the MAPK pathway were upregulated in the infected mice. p38 and ERK 1/2 MAPK genes were 5.6- and 2.0-fold higher, respectively, in aortas of infected vs. uninfected mice. Levels of VCAM-1, ICAM-1, and MCP-1 were ~2.0-2.6-fold higher in aortas of infected vs. uninfected mice. Inhibition of p38 with SB203580 resulted in lower levels of pro-atherogenic molecules and MCMV viral load in aortas of infected mice. MCMV-induced upregulation of p38 may drive the virus-induced acceleration of atherogenesis observed in our model.

Expression of TNFAIP3 in intestinal epithelial cells protects from DSS- but not TNBS-induced colitis

Intestinal epithelial cells (IEC) maintain gastrointestinal homeostasis by providing a physical and functional barrier between the intestinal lumen and underlying mucosal immune system. The activation of NF-κB and prevention of apoptosis in IEC are required to maintain the intestinal barrier and prevent colitis. How NF-κB activation in IEC prevents colitis is not fully understood. TNFα-induced protein 3 (TNFAIP3) is a NF-κB-induced gene that acts in a negative-feedback loop to inhibit NF-κB activation and also to inhibit apoptosis; therefore, we investigated whether TNFAIP3 expression in the intestinal epithelium impacts susceptibility of mice to colitis. Transgenic mice expressing TNFAIP3 in IEC (villin-TNFAIP3 Tg mice) were exposed to dextran sodium sulfate (DSS) or 2,4,6-trinitrobenzene sulfonic acid (TNBS), and the severity and characteristics of mucosal inflammation and barrier function were compared with wild-type mice. Villin-TNFAIP3 Tg mice were protected from DSS-induced colitis and displayed reduced production of NF-κB-dependent inflammatory cytokines. Villin-TNFAIP3 Tg mice were also protected from DSS-induced increases in intestinal permeability and induction of IEC death. Villin-TNFAIP3 Tg mice were not protected from colitis induced by TNBS. These results indicate that TNFAIP3 expression in IEC prevents colitis involving DSS-induced IEC death, but not colitis driven by T cell-mediated inflammation. As TNFAIP3 inhibits NF-κB activation and IEC death, expression of TNFAIP3 in IEC may provide an avenue to inhibit IEC NF-κB activation without inducing IEC death and inflammation.

Targeting IL-8 in colorectal cancer

INTRODUCTION

Colorectal cancer is the leading cause of death from gastrointestinal malignancy in the US. Chemokines and their receptors are being recognized as key regulators of cancers and increasingly as therapeutic targets for metastatic cancers, including colorectal cancer. Several studies have demonstrated that IL-8 and its receptor CXCR2 are two of the most significantly upregulated chemokines in colorectal cancer. IL-8 through binding to its receptors can act not only on inflammatory responses and infectious diseases, but also on cancer cells via their receptors to promote migration, invasion and proliferation, and in vivo angiogenesis. Therefore, IL-8 and CXCR2 may be important therapeutic targets against colorectal cancer.

AREAS COVERED

This review provides an update on the roles of IL-8 and its receptors in colorectal cancer preclinical models and translational relevance: i) Increased expression of IL-8 and/or its receptors has been characterized in colon cancer cells; ii) IL-8 signaling pathway in colorectal cancer cells; iii) targeting IL-8 expression, or receptor-targeted strategies in colorectal cancer, eliminates the redundant function of IL-8 signaling and determines the effects of suppressing IL-8 signaling on tumor progression and development.

EXPERT OPINION

IL-8 and its receptor CXCR2 may function as significant regulatory factors within the tumor microenvironment and be important therapeutic targets in colorectal cancers. Not only may they lead to antitumor properties, but also they may chemosensitize the tumor toward the current chemotherapy.

Deletion of apoptosis signal-regulating kinase-1 prevents ventilator-induced lung injury in mice

Both hyperoxia and mechanical ventilation can independently cause lung injury. In combination, these insults produce accelerated and severe lung injury. We recently reported that pre-exposure to hyperoxia for 12 hours, followed by ventilation with large tidal volumes, induced significant lung injury and epithelial cell apoptosis compared with either stimulus alone. We also reported that such injury and apoptosis are inhibited by antioxidant treatment. In this study, we hypothesized that apoptosis signal-regulating kinase-1 (ASK-1), a redox-sensitive, mitogen-activated protein kinase kinase kinase, plays a role in lung injury and apoptosis in this model. To determine the role of ASK-1 in lung injury, the release of inflammatory mediators and apoptosis, attributable to 12 hours of hyperoxia, were followed by large tidal volume mechanical ventilation with hyperoxia. Wild-type and ASK-1 knockout mice were subjected to hyperoxia (Fi(O(2)) = 0.9) for 12 hours before 4 hours of large tidal mechanical ventilation (tidal volume = 25 μl/g) with hyperoxia, and were compared with nonventilated control mice. Lung injury, apoptosis, and cytokine release were measured. The deletion of ASK-1 significantly inhibited lung injury and apoptosis, but did not affect the release of inflammatory mediators, compared with the wild-type mice. ASK-1 is an important regulator of lung injury and apoptosis in this model. Further study is needed to determine the mechanism of lung injury and apoptosis by ASK-1 and its downstream mediators in the lung.

Role of miR-150-targeting c-Myb in colonic epithelial disruption during dextran sulphate sodium-induced murine experimental colitis and human ulcerative colitis

Chronic inflammatory bowel diseases (IBDs) are associated with differential expression of genes involved in inflammation and tissue remodelling. We surveyed the expression profile of apoptosis-related microRNAs by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) in a dextran sulphate sodium (DSS) murine model of colitis. We found that miR-150 was strongly elevated, whereas c-Myb, a transcription factor and a target gene of miR-150, was significantly reduced in colon tissue after DSS treatment. Interestingly, elevation of miR-150 and down-regulation of c-Myb were also observed in human colon with active ulcerative colitis compared to the normal colon. Supporting the observation of DSS treatment inducing colonic cell apoptosis, Bcl-2, an anti-apoptotic protein known to be regulated by c-Myb, was reduced in colon tissue of DSS-treated mice. Furthermore, forced expression of pre-miR-150 in colonic epithelial HT29 cells strongly elevated miR-150 levels and decreased c-Myb and Bcl-2 levels, thus enhancing cell apoptosis induced by serum deprivation. Together, the present study presents the first evidence that miR-150 and its targeting of c-Myb may serve as a new mechanism underlying the colonic epithelial disruption in DSS-induced murine experimental colitis and in active human IBD.

Evaluation of p38 MAPK pathway as a molecular signature in ulcerative colitis

Early diagnosis and treatment of ulcerative colitis (UC) is clinically challenging. To overcome this problem, we explored the interrelated multiplex signaling pathway to identify molecular signatures in UC by using integrated strategy in proteomics. Intestinal mucosa of 12 UC cases and 12 normal controls underwent comparative proteomic analysis. A total of 26 unique differential proteins were identified, including 12 up-regulated and 14 down-regulated in UC group. A differential protein cluster, consisting of 11 proteins involved in p38 mitogen-activated protein kinase (MAPK) pathway, was deduced and validated by Western blot. Furthermore, three proteins elicited from the protein cluster, phosphorylated p38, MAWBP and galectin-3, as a molecular signature, were analyzed by immunohistochemistry on 118 UC and normal samples. Increased expression of P-p38 and down-regulated MAWBP and/or galectin-3 were detected in UC compared to normal samples (p < 0.001). This signature correlated with disease progression of UC (p < 0.01), and classified UC risk with high sensitivity (94.83 ± 2.91%) and specificity (98.33 ± 1.65%). In addition, P38 MAPK pathway modulated the expression of the protein clusters in macrophage cell line as evidenced by the alteration with specific inhibitor SB203580. These results indicate that molecular signature of P38 MAPK pathway might be a potential biomarker for evaluating UC risk.

Acetylation of a conserved lysine residue in the ATP binding pocket of p38 augments its kinase activity during hypertrophy of cardiomyocytes

Like phosphorylation, acetylation of lysine residues within a protein is considered a biologically relevant modification that controls the activity of target proteins. During stress of cells, massive protein acetylation takes place. Here, we show that p38 mitogen-activated protein kinase (MAPK), which controls many biological functions during stress, is reversibly acetylated by PCAF/p300 and HDAC3. We identified two acetylated lysine residues, K152 and K53, located in the substrate binding domain and in the ATP-binding pocket of p38, respectively. Acetylation of lysine 53 enhanced the activity of p38 by increasing its affinity for ATP binding. The enhanced acetylation and activation of p38 were found to be in parallel with reduced intracellular ATP levels in cardiomyocytes under stress, as well as in vivo models of cardiac hypertrophy. Thus, our data show, for the first time, that p38 activity is critically regulated by, in addition to phosphorylation, reversible acetylation of a lysine residue, which is conserved in other kinases, implying the possibility of a similar mechanism regulating their activity.

Targeting the innate immune system in pediatric inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is complex and involves both innate and adaptive immune responses. This article addresses, in a selective and speculative fashion, the topic of how the various components of the intestinal innate immune system can be manipulated for the purpose of developing new therapeutic approaches. These various components include: agents that stimulate mucosal innate immune responses, such as food components and the gut microbiota; cells that directly respond to these stimuli, including epithelial cells, macrophages and dendritic cells; and molecules that mediate innate immune responses, such as Toll-like receptors and protein kinases. Downregulation of excessive innate immune responses makes therapeutic sense in both pediatric and adult IBD. However, because IBD is complex and characteristically chronic, major alterations of adaptive immunity are also involved in the mediation of inflammation. Thus, novel and truly effective approaches to treat IBD will undoubtedly require intervening in the innate as well as the adaptive branches of the mucosal immunity.

Cell death gene expression profile: role of RIPK2 in dengue virus-mediated apoptosis

Dengue virus (DENV) is a major emerging arthropod-borne pathogen, which infects individuals in both subtropical and tropical regions. Patients with DENV infection exhibit evidence of hepatocyte injury. However, the mechanisms of hepatocyte injury are unclear. Therefore we examined the expression of cell death genes during DENV-infection of HepG2 cells using real-time PCR arrays. The expression changes were consistent with activation of apoptosis and autophagy. Expression of the up-regulated genes, including RIPK2, HRK, TGF-β, PERK, and LC3B, was confirmed by quantitative real-time PCR. RIPK2 belongs to the receptor-interacting protein family of serine/threonine protein kinases, which is a crucial mediator of multiple stress responses that leads to the activation of caspase, NF-κB and MAP kinases including JNK and p38. RIPK2 activity is inhibited by the p38 MAPK pathway inhibitor SB203580. The effect of SB203580 on RIPK2 expression and DENV-induced apoptosis was tested in DENV-infected HepG2 cells. The inhibition of RIPK2 expression by SB203580 significantly reduced apoptosis. SB203580 also significantly reduced DENV capsid protein (DENVC)-mediated apoptosis. Suppression of endogenous RIPK2 in DENV-infected HepG2 cells by small interfering RNA (siRNA) significantly decreased apoptosis suggesting for the first time that RIPK2 plays a role in DENV-mediated apoptosis.

Corticotropin-releasing factor regulates TLR4 expression in the colon and protects mice from colitis

BACKGROUND & AIMS

Defects in the colonic innate immune response have been associated with inflammatory bowel disease (IBD). Corticotropin-releasing hormone (CRH, or corticotropin-releasing factor [CRF]) is a neuropeptide that mediates the stress response in humans, is an immunomodulatory factor with proinflammatory effects, and regulates transcription of Toll-like receptors (TLR)-2 and TLR4. We investigated the role of CRF in an innate immunity-dependent mouse model of IBD.

METHODS

Crh(-/-) and wild-type (Crh(+/+)) mice, which are glucocorticoid insufficient, were given dextran sodium sulfate in their drinking water to induce colitis; in some experiments, mice were also given glucocorticoids. Phenotypes of mice were compared; tissues were analyzed by histology and for expression of immune mediators.

RESULTS

Crh(-/-) mice had more colonic inflammation than Crh(+/+) mice, characterized by reduced numbers of crypts and severe epithelial damage and ulcerations. Colonic tissue levels of the proinflammatory factors interleukin-12 and prostaglandin E(2) were increased in the Crh(-/-) mice. Colons of Crh(-/-) mice expressed lower levels of Tlr4 than wild-type mice before, but not after, colitis was induced. Administration of glucocorticoid at low levels did not prevent Crh(-/-) mice from developing severe colitis. Crh(-/-) mice were unable to recover from acute colitis, as indicated by their increased death rate.

CONCLUSIONS

Mice deficient in CRF down-regulate TLR4 and are more susceptible to dextran sodium sulfate-induced colitis. CRF has anti-inflammatory effects in innate immunity-dependent colitis and its recovery phase; these are independent of glucocorticoid administration. CRF might therefore be developed as a therapeutic target for patients with IBD.

Down-regulation of p38 mitogen-activated protein kinase activation and proinflammatory cytokine production by mitogen-activated protein kinase inhibitors in inflammatory bowel disease

Crohn's disease and ulcerative colitis are inflammatory bowel diseases (IBD) characterized by chronic relapsing mucosal inflammation. Tumour necrosis factor (TNF)-α, a known agonist of the mitogen-activated protein kinase (MAPK) pathway, is a key cytokine in this process. We aimed first to determine whether p38 MAPK is activated in IBD inflamed mucosa, and then studied the effect of four different p38α inhibitory compounds on MAPK phosphorylation and secretion of proinflammatory cytokines by IBD lamina propria mononuclear cells (LPMCs) and organ culture biopsies. In vivo phospho-p38α and p38α expression was evaluated by immunoblotting on intestinal biopsies from inflamed areas of patients affected by Crohn's disease and ulcerative colitis, and from normal mucosa of sex- and age-matched control subjects. Both mucosal biopsies and isolated LPMCs were incubated with four different p38α selective inhibitory drugs. TNF-α, interleukin (IL)-1β and IL-6 were measured in the organ and cell culture supernatants by enzyme-linked immunosorbent assay. We found higher levels of phospho-p38α in the inflamed mucosa of IBD patients in comparison to controls. All the p38α inhibitory drugs inhibited p38α phosphorylation and secretion of TNF-α, IL-1β and IL-6 from IBD LPMCs and biopsies. Activated p38α MAPK is up-regulated in the inflamed mucosa of patients with IBD. Additionally, all the p38α selective inhibitory drugs significantly down-regulated the activation of the MAPK pathway and the secretion of proinflammatory cytokines.

Paired immunoglobulin-like receptor B (PIR-B) negatively regulates macrophage activation in experimental colitis

BACKGROUND & AIMS

Innate and adaptive immune responses are regulated by cross talk between activation and inhibitory signals. Dysregulation of the inhibitory signal can lead to aberrant chronic inflammatory diseases such as the inflammatory bowel diseases (IBD). Little is known about negative regulation of innate intestinal immune activation. We examined the role of the inhibitory receptor paired immunoglobulin-like receptor B (PIR-B) in the regulation of macrophage function in innate intestinal immunity.

METHODS

We examined the susceptibility of Pirb-/- and wild-type (WT) mice to dextran sodium sulfate (DSS)-induced colitis. We assessed proinflammatory cytokine release and mitogen-activated protein kinase (MAPK) and nuclear factor kappaB (NF-kappaB) activation in Pirb-/- and WT macrophages following Escherichia coli stimulation. Macrophage transfer experiments were performed to define the role of PIR-B in the negative regulation of macrophage function in DSS-induced colitis. We also assessed expression of PIR-B human homologues (immunoglobulin-like transcript [ILT]-2 and ILT-3) in colon biopsy samples from healthy individuals (controls) and patients with IBD.

RESULTS

Pirb-/- mice had increased susceptibility to DSS-induced colitis. In vitro analysis showed increased production of proinflammatory cytokines (interleukin-6, interleukin-1beta, and tumor necrosis factor alpha) and activation of MAPK and NF-kappaB in Pirb-/- macrophages following bacterial activation. Adoptive transfer of bone marrow-derived Pirb-/- macrophages into WT mice was sufficient to increase disease susceptibility. ILT-2 and ILT-3 were expressed on CD68+ and CD68- mononuclear cells and intestinal epithelium in colon biopsy samples from patients and controls.

CONCLUSIONS

PIR-B negatively regulates macrophage functions in response to pathogenic bacteria and chronic intestinal inflammatory responses. Inhibitory receptors such as PIR-B might be used as therapeutic targets for treatment of patients with IBD.

Oxazolone-induced over-expression of focal adhesion kinase in colonic epithelial cells of colitis mouse model

We examined the change of protein tyrosine kinases (PTKs) expression levels in colonic epithelial cells isolated from mice in which colitis was induced by oxazolone administration, using the monoclonal antibody YK34, which cross-reacts with a wide variety of PTKs. We identified focal adhesion kinase (FAK) and found the expression level increased due to the induction of colitis. Furthermore, we found that there was a positive correlation between FAK expression and the severity of colitis. Also, FAK expression localized in the colonic epithelium but not in the lamina propria, implying FAK functions in epithelial cells during colitis formation and/or wound repairing.

Targeting signaling pathways with small molecules to treat autoimmune disorders

Chronic activation of immune responses, mediated by inflammatory mediators and involving different effector cells of the innate and acquired immune system characterizes autoimmune disorders, such as rheumatoid arthritis, inflammatory bowel disease, psoriasis and septic shock syndrome. MAPKs are crucial intracellular mediators of inflammation. MAPK inhibitors are attractive anti-inflammatory drugs, because they are capable of reducing the synthesis of inflammation mediators at multiple levels and are effective in blocking proinflammatory cytokine signaling. Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway converts cytokine signals into genomic responses regulating proliferation and differentiation of the immune cells. JAK inhibitors are a new class of immunomodulatory agents with immunosuppressive, anti-inflammatory and antiallergic properties. This review discusses the rationale behind current strategies of targeting MAPK and JAK/STAT signaling pathways, and the overall effects of signal transduction inhibitors in animal models of inflammatory disorders. Signal transduction inhibitors are small molecules that can be administered orally, and initial results of clinical trials have shown clinical benefits in patients with chronic inflammatory disorders.

Use of p38 MAPK Inhibitors for the Treatment of Werner Syndrome

Werner syndrome provides a convincing model for aspects of the normal ageing phenotype and may provide a suitable model for therapeutic interventions designed to combat the ageing process. Cultured primary fibroblast cells from Werner syndrome patients provide a powerful model system to study the link between replicative senescence in vitro and in vivo pathophysiology. Genome instability, together with an increased pro-oxidant state, and frequent replication fork stalling, all provide plausible triggers for intracellular stress in Werner syndrome cells, and implicates p38 MAPK signaling in their shortened replicative lifespan. A number of different p38 MAPK inhibitor chemotypes have been prepared rapidly and efficiently using microwave heating techniques for biological study in Werner syndrome cells, including SB203580, VX-745, RO3201195, UR-13756 and BIRB 796, and their selectivity and potency evaluated in this cellular context. Werner syndrome fibroblasts treated with a p38 MAPK inhibitor reveal an unexpected reversal of the accelerated ageing phenotype. Thus the study of p38 inhibition and its effect upon Werner pathophysiology is likely to provide new revelations into the biological mechanisms operating in cellular senescence and human ageing in the future.

Inhibition of p38 MAPK improves intestinal disturbances and oxidative stress induced in a rabbit endotoxemia model

BACKGROUND

Lipopolysaccharide (LPS) decreases intestinal contractility and induces the release of reactive oxygen species, which play an important role in the pathogenesis of sepsis. p38 mitogen-activated protein kinase (MAPK) can be activated by a variety of stimuli such as LPS. The aims of this study were: (i) to investigate the role of p38 MAPK in the effect of LPS on (a) the acetylcholine, prostaglandin E(2) and KCl-induced contractions of rabbit duodenum and (b) the oxidative stress status; (ii) to localize the active form of p38 in the intestine.

METHODS

Rabbits were injected with (i) saline, (ii) LPS, (iii) SB203580, a specific p38 MAPK inhibitor or (iv) SB203580 + LPS. Duodenal contractility was studied in an organ bath. SB203580 was also tested in vitro. The protein expression of p-p38 and total p38 was measured by Western blot and p-p38 was localized by immunohistochemistry. The formation of products of oxidative damage to proteins (carbonyls) and lipids (MDA+4-HDA) was quantified in intestine and plasma.

KEY RESULTS

ACh, PGE(2) and KCl-induced contractions decreased with LPS. LPS increased phospho-p38 expression and the levels of carbonyls and MDA+4-HDA. SB203580 blocked the effect of LPS on the ACh, PGE(2) and KCl-induced contractions in vivo and in vitro and the levels of carbonyls and MDA+4-HDA. P-p38 was detected in neurons of the myenteric plexus and smooth muscle cells of duodenum.

CONCLUSIONS & INFERENCES

Lipopolysaccharide decreases the duodenal contractility in rabbits and increases the production of free radicals. p38 MAPK is a mediator of these effects.

Distinct effects of p38alpha deletion in myeloid lineage and gut epithelia in mouse models of inflammatory bowel disease

BACKGROUND & AIMS

p38Alpha is a mitogen-activated protein kinase that mediates inflammatory responses, but its role in inflammatory bowel disease is unclear. The effects of p38alpha inhibitors have been inconsistent in animal models and clinical studies of inflammatory bowel disease, possibly arising from the different functions of p38alpha in different tissues or cell types. We investigated the effects of p38alpha inhibition in myeloid versus colonic epithelium.

METHODS

We studied mice with myeloid cell-specific and intestinal epithelial cell-specific disruption of p38alpha (LtrLys(Cre)-p38alpha(Delta/Delta) mice and Villin(Cre)-p38alpha(Delta/Delta) mice), as well as p38beta, gamma, and delta knockout. Colitis was induced using dextran sodium sulfate or trinitrobenzene sulfonic acid (TNBS).

RESULTS

Mice with myeloid cell-specific deletion of p38alpha had less inflammation and an improved disease condition compared with wild-type mice, whereas mice with intestinal epithelial cell-specific deletion of p38alpha had increased progression of colitis that resulted from disrupted intestinal epithelial homeostasis. The distinct effects of p38alpha disruption in different tissue types might underlie the unsuccessful therapeutic application of p38 inhibitors to colitis. We found that a gamma-secretase inhibitor, which functions opposite that of a p38 inhibitor in the regulation of intestinal epithelial homeostasis, can significantly improve the effects of a p38 inhibitor in reducing colitis.

CONCLUSIONS

p38Alpha has distinct functions in mouse myeloid cells versus colonic epithelium; these differences should be taken into consideration in defining the role of p38alpha in inflammation and developing p38 inhibitors as therapeutics.

Apoptosis signal-regulating kinase 1 regulates colitis and colitis-associated tumorigenesis by the innate immune responses

BACKGROUND & AIMS

Mitogen-activated protein kinase (MAPK) signaling pathways regulate multiple cellular functions and are implicated in the pathogenesis of inflammatory bowel disease and colitis-associated cancer (CAC). Apoptosis signal-regulating kinase 1 (ASK1) is a MAPK kinase kinase; little is known about the role of ASK1 in colonic disease. We assessed the involvement of ASK1 in the development of intestinal inflammation and CAC.

METHODS

Dextran sodium sulfate (DSS) or Citrobacter rodentium was used to induce colitis in wild-type (WT) and ASK1 knock-out (ASK1(-/-)) mice; CAC was induced by azoxymethane injection followed by repeated intake of DSS by the mice. Primary macrophages were isolated from WT and ASK1(-/-) mice and used to investigate the involvement of ASK1 in innate immune responses. Bone marrow chimeric mice were used to study the contribution of myeloid cells to colitis activity.

RESULTS

ASK1 deficiency increased susceptibility to colonic inflammation in both models of colitis. In vitro, ASK1(-/-) macrophages were impaired in their ability to kill bacteria and had increased susceptibility to bacterial-induced apoptosis, because p38 was inactivated. Expression of antiapoptotic genes was greatly reduced in ASK1(-/-) macrophages. WT mice given transplants of ASK1(-/-) mouse-derived bone marrow cells developed more severe DSS-induced colitis than mice with WT-derived bone marrow cells. In the CAC model, ASK1(-/-) mice developed more numerous and larger tumors than WT mice through increased colonic inflammation.

CONCLUSIONS

ASK1 controls the development of intestinal inflammation and CAC through the regulation of innate immunity.

Prophylactic treatment with Hypoxis hemerocallidea corm (African potato) methanolic extract ameliorates Brachyspira hyodysenteriae-induced murine typhlocolitis

Brachyspira hyodysenteriae is the causative agent of swine dysentery and induces a characteristic mucosal inflammation resulting in pronounced typhlocolitis in swine and mice. Hypoxis hemerocallidea corm (African potato) is a traditional medicine in southern Africa. An African potato methanolic extract (APME) and one of its major constituents, hypoxoside, have been shown in vitro to possess an anti-inflammatory property. The aim of this study is to evaluate the ability of APME to prevent or ameliorate B. hyodysenteriae-induced typhlocolitis. Mice were orally treated with APME for seven days prior to B. hyodysenteriae infection and the treatments continued daily for seven days postinfection (DPI). At the termination of the experiment, weight loss, gross and histological lesions, myeloperoxidase (MPO) activity, and intestinal epithelial proliferation were evaluated. In addition, the protein level of activated p65 subunit of nuclear factor- κB (NF- κB) and mRNA expression of NF- κB-associated genes were also measured. APME treatment significantly ( P < 0.05) reduced weight loss, the severity of typhlocolitis, mucosal MPO activity and intestinal epithelial proliferation subsequent to B. hyodysenteriae infection. Mucosal protein levels of active p65 and expression levels of NF- κB-associated genes following B. hyodysenteriae infection were also decreased by the oral treatment with APME. In conclusion, prophylactic treatment with APME ameliorated B. hyodysenteriae-induced typhlocolitis, suggesting H. hemerocallidea corm methanolic extract may have potential for ameliorating enteropathies that are mediated by overactive host inflammatory processes.

Activation of the nucleotide oligomerization domain signaling pathway by the non-bacterially derived xanthone drug 5'6-dimethylxanthenone-4-acetic acid (Vadimezan)

The cytosolic nucleotide-binding oligomerization domain 1 (NOD1)/CARD4 and NOD2/CARD15 proteins are members of NOD-like receptors recognizing specific motifs within peptidoglycans of both Gram-negative and Gram-positive bacteria. NOD1 and NOD2 signal via the downstream adaptor serine/threonine kinase RIP2/CARDIAK/RICK to initiate NF-kappaB activation and the release of inflammatory cytokines/chemokines. In this report, we show that 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a cell-permeable, small molecule that has anti-tumor activity, can also activate NOD1 and NOD2. This was demonstrated: 1) by using human embryonic kidney epithelial (HEK) 293 cells transfected with a NF-kappaB reporter plasmid in combination with NOD1 or NOD2 expression plasmids; 2) by inhibiting DMXAA-induced chemokine (CXCL10) mRNA and protein production in the AB12 mesothelioma cell line using a pharmacological inhibitor of RICK kinase, SB20358; and 3) by using small interfering RNA to knock down NOD2 and lentiviral short hairpin RNA to knock down RICK. These findings expand the potential ligands for the NOD-like receptors, suggesting that other xanthone compounds may act similarly and could be developed as anti-tumor agents. This information also expands our knowledge on the mechanisms of action of the anti-tumor agent DMXAA (currently in clinical trials) and may be important for its biological activity.

Effects of p38 MAPK inhibition on early stages of diabetic retinopathy and sensory nerve function

Purpose. p38 mitogen-activated protein kinase (MAPK) is known to play a regulatory role in inflammatory processes in disease. Inflammation has been linked also to the development of diabetic retinopathy in rodents. This study was conducted to evaluate the effect of a p38 MAPK inhibitor on the development of early stages of diabetic retinopathy in rats. Methods. Streptozotocin-diabetic rats were assigned to two groups-treated with the p38 MAPK inhibitor PHA666859 (Pfizer, New York, NY) and untreated-and compared with age-matched nondiabetic control animals. Results. At 2 months of diabetes, insulin-deficient diabetic control rats exhibited significant increases in retinal superoxide, nitric oxide (NO), cyclooxygenase (COX)-2, and leukostasis within retinal microvessels. All these abnormalities were significantly inhibited by the p38 MAPK inhibitor (25 mg/kgBW/d). At 10 months of diabetes, significant increases in the number of degenerate (acellular) capillaries and pericyte ghosts were measured in control diabetic rats versus those in nondiabetic control animals, and pharmacologic inhibition of p38 MAPK significantly inhibited all these abnormalities (all P < 0.05). This therapy also had beneficial effects outside the eye in diabetes, as evidenced by the inhibition of a diabetes-induced hypersensitivity of peripheral nerves to light touch (tactile allodynia). Conclusions. p38 MAPK plays an important role in diabetes-induced inflammation in the retina, and inhibition of p38 MAPK offers a novel therapeutic approach to inhibiting the development of early stages of diabetic retinopathy and other complications of diabetes.

CD14 signaling restrains chronic inflammation through induction of p38-MAPK/SOCS-dependent tolerance

Current thinking emphasizes the primacy of CD14 in facilitating recognition of microbes by certain TLRs to initiate pro-inflammatory signaling events and the importance of p38-MAPK in augmenting such responses. Herein, this paradigm is challenged by demonstrating that recognition of live Borrelia burgdorferi not only triggers an inflammatory response in the absence of CD14, but one that is, in part, a consequence of altered PI3K/AKT/p38-MAPK signaling and impaired negative regulation of TLR2. CD14 deficiency results in increased localization of PI3K to lipid rafts, hyperphosphorylation of AKT, and reduced activation of p38. Such aberrant signaling leads to decreased negative regulation by SOCS1, SOCS3, and CIS, thereby compromising the induction of tolerance in macrophages and engendering more severe and persistent inflammatory responses to B. burgdorferi. Importantly, these altered signaling events and the higher cytokine production observed can be mimicked through shRNA and pharmacological inhibition of p38 activity in CD14-expressing macrophages. Perturbation of this CD14/p38-MAPK-dependent immune regulation may underlie development of infectious chronic inflammatory syndromes.

Macrophages express CD14 which partners with Toll-like receptor 2/1 to recognize bacterial lipoproteins such as those of Borrelia burgdorferi, the causative agent of Lyme disease. In vitro evidence demonstrates that blocking CD14 recognition of bacterial components ablates innate host cell inflammatory responses. Similarly, blocking downstream p38 kinase activity dampens the cellular response to these same microbial stimuli. This body of work underpins two well-established paradigms which cite the primacy of CD14 in facilitating TLR recognition of microbes to initiate proinflammatory signaling events and the importance of p38 in augmenting such responses. However, contrary to these paradigms, our prior study using a mouse model of Lyme disease demonstrated an association between CD14 deficiency, increased bacterial burden, and more severe and persistent disease. Herein, we provide a mechanistic explanation for this unanticipated host immune response implicating impaired negative regulation of inflammatory signaling pathways as an underlying cause. Consequent to impaired negative regulation the host becomes “intolerant” of continued exposure to bacteria and thus mounts a perpetual inflammatory response to their presence. An intriguing question raised by these findings is whether individual differences in the severity and clinical course of infection might reflect the susceptibility of the patient's innate immune system to tolerization.

Gadd45 proteins as critical signal transducers linking NF-kappaB to MAPK cascades

The growth arrest and DNA damage-inducible 45 (Gadd45) proteins are a group of critical signal transducers that are involved in regulations of many cellular functions. Accumulated data indicate that all three Gadd45 proteins (i.e., Gadd45alpha, Gadd45beta, and Gadd45gamma) play essential roles in connecting an upstream sensor module, the transcription Nuclear Factor-kappaB (NF-kappaB), to a transcriptional regulating module, mitogen-activated protein kinase (MAPK). This NF-kappaB-Gadd45(s)-MAPK pathway responds to various kinds of extracellular stimuli and regulates such cell activities as growth arrest, differentiation, cell survival, and apoptosis. Defects in this pathway can also be related to oncogenesis. In the first part of this review, the functions of Gadd45 proteins, and briefly NF-kappaB and MAPK, are summarized. In the second part, the mechanisms by which Gadd45 proteins are regulated by NF-kappaB, and how they affect MAPK activation, are reviewed.

Mitogen activated protein kinases: a role in inflammatory bowel disease?

Since their discovery more than 15 years ago, the mitogen activated protein kinases (MAPK) have been implicated in an ever-increasingly diverse array of pathways, including inflammatory signalling cascades. Inflammatory bowel diseases (IBD), such as ulcerative colitis and Crohn's disease, are characterized by the perpetual production of inflammatory mediators. Research into the transduction pathway behind this over-production has highlighted the potential mediating role for the MAPKs and their related signalling components. This review highlights some of the research into the role for the MAPKs and their related signalling proteins in influencing the progression of IBD.

In vivo profiling endogenous interactions with knock-out in mammalian cells

To precisely identify and screen target-specific protein-protein interactions at the endogenous level, here we introduce a novel quantitative proteomic method we have termed in vivo Profiling Endogenous Interactions with Knock-out (iPEIK). In our design, mouse embryonic fibroblasts (MEFs) derived from target gene knockout (KO) mice can be stable isotope-tagged and serve as a target-free background to "light-up" the target protein-specific protein complex formed in the corresponding wild-type (WT) cells. In mass spectrometric analysis of the pairs of non-labeled versus heavy isotope-labeled peptide signals derived from WT versus KO cells, respectively, we then quantitatively measured the abundance differences of the proteins in the complex immunoprecipitated (IP) from the target-expressing WT versus target-absent KO cells, respectively. Those proteins detected with little or no presence in the cells of KO origin were determined as target-specific interacting partners. Further, dynamic interactors could be identified through different IP mixing schemes. Using iPEIK we identified multiple interacting partners both previously known and unknown to be associated with mitogen-activated protein kinase kinase kinase 2 (MEKK2). Because of the availability of a large library of knockout mice models with various target proteins of biological interests our method is generally applicable to screen any endogenous target-specific PPIs of physiological relevance.

Ste20-related proline/alanine-rich kinase (SPAK) regulated transcriptionally by hyperosmolarity is involved in intestinal barrier function

The Ste20-related protein proline/alanine-rich kinase (SPAK) plays important roles in cellular functions such as cell differentiation and regulation of chloride transport, but its roles in pathogenesis of intestinal inflammation remain largely unknown. Here we report significantly increased SPAK expression levels in hyperosmotic environments, such as mucosal biopsy samples from patients with Crohn's disease, as well as colon tissues of C57BL/6 mice and Caco2-BBE cells treated with hyperosmotic medium. NF-kappaB and Sp1-binding sites in the SPAK TATA-less promoter are essential for SPAK mRNA transcription. Hyperosmolarity increases the ability of NF-kappaB and Sp1 to bind to their binding sites. Knock-down of either NF-kappaB or Sp1 by siRNA reduces the hyperosmolarity-induced SPAK expression levels. Furthermore, expression of NF-kappaB, but not Sp1, was upregulated by hyperosmolarity in vivo and in vitro. Nuclear run-on assays showed that hyperosmolarity increases SPAK expression levels at the transcriptional level, without affecting SPAK mRNA stability. Knockdown of SPAK expression by siRNA or overexpression of SPAK in cells and transgenic mice shows that SPAK is involved in intestinal permeability in vitro and in vivo. Together, our data suggest that SPAK, the transcription of which is regulated by hyperosmolarity, plays an important role in epithelial barrier function.

Inhibition of p38 mitogen-activated protein kinase pathway as prophylaxis of postoperative ileus in mice

BACKGROUND & AIMS

Postoperative ileus, an iatrogenic complication of abdominal surgery, is mediated by severe inflammation of the tunica muscularis. Macrophages that reside in the muscularis have important roles in initiating the inflammation. We investigated whether activation of the p38 mitogen-activated protein kinase (MAPK) and stress-activated protein kinase is involved in the genesis of postoperative ileus, and whether p38-MAPK inhibition by the macrophage-specific inhibitor semapimod prevents intestinal dysmotility.

METHODS

Postoperative ileus was induced by intestinal manipulation of the small bowel in mice. Protein kinase phosphorylation was assessed by immunoblotting of muscularis externa preparations. Proinflammatory gene expression was quantified by real-time polymerase chain reaction. Myeloperoxidase histochemistry for neutrophils was performed in jejunal segments. Nitric oxide production was measured by Griess reaction in smooth-muscle organ culture supernatants. Jejunal contractility was assessed within an organ bath setup. Intestinal motility was analyzed by gastrointestinal and colonic transit measurements.

RESULTS

High levels of p38-MAPK and stress-activated protein kinase phosphorylation were observed immediately after intestinal manipulation. Semapimod treatment led to a significant decrease of p38-MAPK phosphorylation in macrophages; proinflammatory gene expression of macrophage inflammatory protein-1alpha, interleukin-6, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1; and neutrophil infiltration. Furthermore, semapimod completely abrogated nitric oxide production within the tunica muscularis. Subsequently, semapimod prevented the suppression of smooth muscle contractility and small intestinal and colonic motility after intestinal manipulation.

CONCLUSION

A single preoperative semapimod administration prevents intestinal macrophage activation and subsequent gastrointestinal dysmotility induced by abdominal surgery. Semapimod inhibits p38-MAPK and nitric oxide production in macrophages, making it a promising strategy for prophylaxis of postoperative ileus.

Synthesis and characterization of novel quinazoline type inhibitors for mutant and wild-type EGFR and RICK kinases

The development of selective protein kinase inhibitors has become an important area of drug discovery for the treatment of different diseases. We report the synthesis and characterization of a series of novel quinazoline derivatives against three therapeutically important and pharmacologically related kinases: 1) epidermal growth factor receptor (EGFR; wild type and mutant) in the field of cancer, 2) receptor-interacting caspase-like apoptosis-regulatory kinase (RICK) in the field of inflammation, and 3) pUL97 of human cytomegalovirus (HCMV). For reference purpose we have synthesized the four clinically relevant quinazolines, including the lead compounds, which we previously identified for RICK and pUL97. A total of 52 quinazoline derivatives were synthesized and tested on the basis of these leads to specifically target the hydrophobic pocket of the ATP-binding site. Selected compounds were tested on wild-type and mutant forms of EGFR, RICK, and pUL97 kinases; their logP and logS values for assessing suitability as drugs were calculated and hit or lead compounds identified.

Combined glutamine and arginine decrease proinflammatory cytokine production by biopsies from Crohn's patients in association with changes in nuclear factor-kappaB and p38 mitogen-activated protein kinase pathways

Glutamine (Gln) and arginine (Arg) are conditionally essential amino acids with immunomodulatory properties. The aim of the study was to assess the effects of Gln and Arg alone or in combination on cytokine release by cultured colonic biopsies from patients with active Crohn's disease (CD). Ten consecutive patients [mean (range) age 26 (18-39) y] with active colonic CD (mean CD activity index: 383.7 +/- 129.8) were prospectively included in the study. Eight colonic biopsies were obtained via a colonoscopy and incubated during 18 h with low (physiological) or high (pharmacological) doses of Arg (0.1 or 2 mmol/L designated as Arg(low) or Arg(high), respectively) and Gln (0.6 or 10 mmol/L designated as Gln(low) or Gln(high), respectively). The concentrations of cytokines [interleukin (IL)-4, IL-10, IL-8, IL-6, tumor necrosis factor-alpha (TNFalpha), IL-1beta, interferon-gamma) were assessed by ELISA, and nitric oxide (NO) production was evaluated by Griess assay. Nuclear factor (NF)-kappaB p65 subunit, inhibitor of NFkappaB-alpha, and p38 mitogen-activated protein kinase (MAPK) were assessed by immunoblotting. Arg(high)/Gln(high) decreased the production of TNFalpha, IL-1beta, IL-8, and IL-6 (each P < 0.01). Arg(low)/Gln(high) decreased IL-6 and IL-8 production (both P < 0.01), whereas Arg(high)/Gln(low) did not affect cytokine and NO production. Arg(low)/Gln(high) and Arg(high)/Gln(high) decreased NF-kappaB p65 subunit expression, whereas p38 MAPK was decreased only by Arg(high)/Gln(high). Combined pharmacological doses of Arg and Gln decreased TNFalpha and the main proinflammatory cytokines release in active colonic CD biopsies via NF-kappaB and p38 MAPK pathways. These results could be the basis of prospective studies evaluating the effects of enteral supply of combined Arg and Gln during active CD.