Signal transduction through NF-kappa B

NF-κB signaling in the brain of autistic subjects

Autism is a neurodevelopmental disorder characterized by problems in communication, social skills, and repetitive behavior. Recent studies suggest that apoptotic and inflammatory mechanisms may contribute to the pathogenesis of this disorder. Nuclear factor-κB (NF-κB) is an important gene transcriptional factor involved in the mediation of inflammation and apoptosis. This study examined the activities of the NF-κB signaling pathway in the brain of autistic subjects and their age-matched controls. The NF-κB activation is also determined in the brain of BTBR mice, which is a promising animal model for study of pathogenic mechanisms responsible for autism. Our results showed that the level of IKKα kinase, which phosphorylates the inhibitory subunit IκBα, is significantly increased in the cerebellum of autistic subjects. However, the expression and phosphorylation of IκBα are not altered. In addition, our results demonstrated that the expression of NF-κB (p65), and the phosphorylation/activation of NF-κB (p65) at Ser536 are not significantly changed in the cerebellum and cortex of both autistic subjects and BTBR mice. Our findings suggest that the NF-κB signaling pathway is not disregulated in the brain of autistic subjects and thus may not be significantly involved in the processes of abnormal inflammatory responses suggested in autistic brain.

Exposure to 16O-particle radiation causes aging-like decrements in rats through increased oxidative stress, inflammation and loss of autophagy

Exposing young rats to particles of high energy and charge (HZE particles), a ground-based model for exposure to cosmic rays, enhances indices of oxidative stress and inflammation, disrupts the functioning of neuronal communication, and alters cognitive behaviors. Even though exposure to HZE particles occurs at low fluence rates, the cumulative effects of long-term exposure result in molecular changes similar to those seen in aged animals. In the present study, we assessed markers of autophagy, a dynamic process for intracellular degradation and recycling of toxic proteins and organelles, as well as stress and inflammatory responses, in the brains of Sprague-Dawley rats irradiated at 2 months of age with 5 and 50 cGy and 1 Gy of ionizing oxygen particles ((16)O) (1000 MeV/n). Compared to nonirradiated controls, exposure to (16)O particles significantly inhibited autophagy function in the hippocampus as measured by accumulation of ubiquitin inclusion bodies such as P62/SQSTM1, autophagosome marker microtubule-associated protein 1 beta light chain 3 (MAP1B-LC3), beclin1 and proteins such as mammalian target of rapamycin (mTOR). The molecular changes measured at short (36 h) and long (75 days) intervals after (16)O-particle exposure indicate that the loss of autophagy function occurred shortly after exposure but was recovered via inhibition of mTOR. However, HZE-particle radiation caused significant sustained loss of protein kinase C alpha (PKC-α), a key G protein modulator involved in neuronal survival and functions of neuronal trophic factors. Exposure to (16)O particles also caused substantial increases in the levels of nuclear factor kappa B (NF-κB) and glial fibrillary acidic protein (GFAP), indicating glial cell activation 75 days after exposure. This is the first report to show the molecular effects of (16)O-particle radiation on oxidative stress, inflammation and loss of autophagy in the brain of young rats.

Okadaic acid induces apoptosis through the PKR, NF-κB and caspase pathway in human osteoblastic osteosarcoma MG63 cells

Okadaic acid (OA) is the major component of diarrheic shellfish poisoning toxins and a potent inhibitor of protein phosphatase 1 and 2A. However, the underlying regulatory mechanisms involved in OA-induced cell death are not well understood. In the present study, we examined the effects of OA on apoptosis of MG63 cells by characterizing apoptotic morphological changes of the cells and DNA fragmentation. The roles of double-stranded RNA-dependent protein kinase (PKR), nuclear factor-κB (NF-κB) and caspase in OA-mediated apoptosis in MG63 cells were also examined. Results showed that OA induced cytotoxicity and apoptosis in MG63 cells at IC50 of 75 nM. A functional PKR pathway is required to induce apoptosis in response to OA treatment. Blockade of NF-κB by ammonium pyrrolidinedithiocarbamate (PDTC) resulted in down-regulation of apoptosis. The caspase-3 and caspase-8 inhibitors blocked apoptosis in MG63 cells. In conclusion, our results imply that OA can induce MG63 cell apoptosis through the PKR, NF-κB and caspase pathway.

Proanthocyanidins from Grape Seeds Modulate the NF-κB Signal Transduction Pathways in Rats with TNBS-Induced Ulcerative Colitis

Abstract To elucidate the molecular mechanisms involved in the therapeutic effects of proanthocyanidins from grape seeds (GSPE), we explore whether GSPE regulates the inflammatory response of TNBS-induced colitis in rats at the levels of NF-κB signal transduction pathway. Rats were intragastrically administered of different doses of GSPE (100, 200 and 400 mg·kg⁻¹) per day for seven days after ulcerative colitis (UC) was induced by intracolonic injection of 2,4,6-trinitrobenzenesulfonic acid (TNBS) dissolved in 50% ethanol. Sulfasalazine (SASP) at 400 mg/kg was used as a positive control drug. The expression of nuclear factor-kappa B (NF-κB), phospho-I kappaB-alpha (pIκBα), inhibitor kappa B kinase (IκK) in the colon tissues were all measured by enzyme-linked immunosorbent assay (ELISA) methods. Treatment with GSPE reduced the expression of NF-κB, pIκBα and IκK in the colon. The results of this study show that GSPE exerts beneficial effects in inflammatory bowel disease by inhibition of NF-κB signal transduction pathways.

Antibody-mediated allograft rejection: the emerging role of endothelial cell signalling and transcription factors

The presence of antibodies against class I human leukocyte antigens (HLA) can cause the development of chronic allograft rejection. Although endothelial cell activation has been identified as a main effector, the mechanisms mediating this process are not fully understood. Exposure of endothelium to antibodies against HLA antigens induces cell activation which promotes rejection. This activation process can be divided into two phases: an early response in which intracellular signalling proteins and transcription factors are activated, and a later change in protein expression and cell function. In this review, antibody-mediated endothelial signalling and the role of transcription factors in organ transplantation will be described with a particular focus on their potential to mediate some of the graft-damaging effects of anti-HLA class I antibodies.

Effects of atrazine and chlorpyrifos on the mRNA levels of IL-1 and IFN-γ2b in immune organs of common carp

Atrazine (ATR) and chlorpyrifos (CPF) are widely used in agriculture has resulted in a series of toxicological and environmental problems. The aim of this study was to investigate the effects of ATR, CPF and their mixture on the mRNA levels of interleukin-1β (IL-1β), interleukin receptor I (IL-1RI) and interferon gamma (IFN-γ2b) in both spleen and head kidney of Common carp. In this study, juvenile common carp were exposed to ATR (at concentrations of 4.28, 42.8 and 428 μg/L), CPF (at concentrations of 1.16, 11.6 and 116 μg/L), and their mixture (at concentrations of 1.16, 11.6 and 116 μg/L). The mRNA levels of IL-1β, IL-1R1 and IFN-γ2b in spleen and head kidney were detected by using RT-PCR. Our results indicated that IL-1β, IL-1R1 expression significantly increased after exposure in high concentration ATR, CPF and their mixture, but IFN-γ2b mRNA shown different expression trends. Our results suggested that ATR, CPF and their mixture probably induced damages on spleen and head kidney may be association with increasing IL-1β, IL-1R1 mRNA synthesis. After 20-day recovery test, IL-1β, IL-1R1 and IFN-γ2b mRNA expression remain at high level in majority of the treated groups, we concluded that the restoration of tissue and immune system damage probably needs longer time.

Microglial phagocytosis induced by fibrillar β-amyloid is attenuated by oligomeric β-amyloid: implications for Alzheimer's disease

Background

Reactive microglia are associated with β-amyloid (Aβ) deposit and clearance in Alzhiemer's Disease (AD). Paradoxically, entocranial resident microglia fail to trigger an effective phagocytic response to clear Aβ deposits although they mainly exist in an "activated" state. Oligomeric Aβ (oAβ), a recent target in the pathogenesis of AD, can induce more potent neurotoxicity when compared with fibrillar Aβ (fAβ). However, the role of the different Aβ forms in microglial phagocytosis, induction of inflammation and oxidation, and subsequent regulation of phagocytic receptor system, remain unclear.

Results

We demonstrated that Aβ(1-42) fibrils, not Aβ(1-42) oligomers, increased the microglial phagocytosis. Intriguingly, the pretreatment of microglia with oAβ(1-42) not only attenuated fAβ(1-42)-triggered classical phagocytic response to fluorescent microspheres but also significantly inhibited phagocytosis of fluorescent labeled fAβ(1-42). Compared with the fAβ(1-42) treatment, the oAβ(1-42) treatment resulted in a rapid and transient increase in interleukin 1β (IL-1β) level and produced higher levels of tumor necrosis factor-α (TNF-α), nitric oxide (NO), prostaglandin E₂ (PGE₂) and intracellular superoxide anion (SOA). The further results demonstrated that microglial phagocytosis was negatively correlated with inflammatory mediators in this process and that the capacity of phagocytosis in fAβ(1-42)-induced microglia was decreased by IL-1β, lippolysaccharide (LPS) and tert-butyl hydroperoxide (t-BHP). The decreased phagocytosis could be relieved by pyrrolidone dithiocarbamate (PDTC), a nuclear factor-κB (NF-κB) inhibitor, and N-acetyl-L-cysteine (NAC), a free radical scavenger. These results suggest that the oAβ-impaired phagocytosis is mediated through inflammation and oxidative stress-mediated mechanism in microglial cells. Furthermore, oAβ(1-42) stimulation reduced the mRNA expression of CD36, integrin β1 (Itgb1), and Ig receptor FcγRIII, and significantly increased that of formyl peptide receptor 2 (FPR2) and scavenger receptor class B1 (SRB1), compared with the basal level. Interestingly, the pre-stimulation with oAβ(1-42) or the inflammatory and oxidative milieu (IL-1β, LPS or t-BHP) significantly downregulated the fAβ(1-42)-induced mRNA over-expression of CD36, CD47 and Itgb1 receptors in microglial cells.

Conclusion

These results imply that Aβ oligomers induce a potent inflammatory response and subsequently disturb microglial phagocytosis and clearance of Aβ fibrils, thereby contributing to an initial neurodegenerative characteristic of AD. Antiinflammatory and antioxidative therapies may indeed prove beneficial to delay the progression of AD.

Protein kinase Ctheta is a specific target for inhibition of the HIV type 1 replication in CD4+ T lymphocytes

Integration of HIV-1 genome in CD4(+) T cells produces latent reservoirs with long half-life that impedes the eradication of the infection. Control of viral replication is essential to reduce the size of latent reservoirs, mainly during primary infection when HIV-1 infects CD4(+) T cells massively. The addition of immunosuppressive agents to highly active antiretroviral therapy during primary infection would suppress HIV-1 replication by limiting T cell activation, but these agents show potential risk for causing lymphoproliferative disorders. Selective inhibition of PKC, crucial for T cell function, would limit T cell activation and HIV-1 replication without causing general immunosuppression due to PKC being mostly expressed in T cells. Accordingly, the effect of rottlerin, a dose-dependent PKC inhibitor, on HIV-1 replication was analyzed in T cells. Rottlerin was able to reduce HIV-1 replication more than 20-fold in MT-2 (IC(50) = 5.2 μM) and Jurkat (IC(50) = 2.2 μM) cells and more than 4-fold in peripheral blood lymphocytes (IC(50) = 4.4 μM). Selective inhibition of PKC, but not PKCδ or -ζ, was observed at <6.0 μM, decreasing the phosphorylation at residue Thr(538) on the kinase catalytic domain activation loop and avoiding PKC translocation to the lipid rafts. Consequently, the main effector at the end of PKC pathway, NF-κB, was repressed. Rottlerin also caused a significant inhibition of HIV-1 integration. Recently, several specific PKC inhibitors have been designed for the treatment of autoimmune diseases. Using these inhibitors in combination with highly active antiretroviral therapy during primary infection could be helpful to avoid massive viral infection and replication from infected CD4(+) T cells, reducing the reservoir size at early stages of the infection.

MCP-1-induced protein attenuates endotoxin-induced myocardial dysfunction by suppressing cardiac NF-кB activation via inhibition of IкB kinase activation

Myocardial contractile dysfunction is a major consequence of septic shock, which is mainly mediated by nuclear factor-kappa B (NF-кB)-dependent production of inflammatory mediators in the heart. A novel zinc-finger protein, MCP-1-induced protein (MCPIP), is thought to have NF-кB inhibitory activity in certain cell cultures, but its pathophysiological consequence in vivo remains undefined. This study aims to clarify whether the anti-inflammatory potency of MCPIP contribute to amelioration of septic myocardial inflammation and dysfunction in vivo. Transgenic mice (TG) with cardiac-specific expression of MCPIP and their littermate wild-type (WT) controls were challenged with Escherichia coli LPS (10mg/kg ip) and myocardial function was assessed 18 h later using echocardiography. LPS administration markedly deteriorated myocardial contractile function evidenced by reduction of the percentage of left ventricular fractional shortening, which was significantly attenuated by myocardial expression of MCPIP. MCPIP TG mice exhibited a markedly reduced myocardial inflammatory cytokines, less of iNOS expression and peroxynitrite formation, decreased caspase-3/7 activities and apoptotic cell death compared with LPS-treated WT mice. Activation of cardiac NF-кB observed in LPS-challenged WT mice was suppressed by the presence of MCPIP, as evidenced by decreased phosphorylation of IкB kinase (IKKα/β), reduced degradation of the cytosolic IкBα, and decreased nuclear translocation of NF-кB p65 subunit and its target DNA-binding activity. These results suggest that MCPIP has therapeutic values to protect heart from inflammatory pathologies, possibly through inhibition of IкB kinase complex, leading to blockade of NF-кB activation, and subsequently, attenuation of the proinflammatory state and nitrosative stress in the myocardium.

Lipopolysaccharide stimulates syntheses of toll-like receptor 2 and surfactant protein-A in human alveolar epithelial A549 cells through upregulating phosphorylation of MEK1 and ERK1/2 and sequential activation of NF-κB

Surfactant proteins (SPs) and toll-like receptors (TLRs) contribute to regulation of sepsis-induced acute lung injury. Lipopolysaccharide (LPS) is one of the major causes of septic shock. This study was designed to evaluate the effects of LPS on the regulation of tlr-2 and sp-a gene expression in human alveolar epithelial A549 cells and the possible mechanisms. Exposure of A549 cells to LPS increased the expressions of TLR2 and SP-A mRNA and protein in time-dependent manners. A search using a bioinformatic approach found that there are several nuclear factor kappa-B (NF-κB)-DNA-binding motifs in the promoter region of the tlr2 and sp-a genes. Immunoblotting analyses revealed that exposure to LPS time-dependently enhanced the translocation of NF-κB from the cytoplasm to nuclei. Analyses of an electrophoretic mobility shift assay further showed that LPS augmented the transactivation activity of NF-κB to its consensus oligonucleotides in A549cells. Sequentially, treatment of A549 cells with LPS increased phosphorylation of extracellular signal-regulated kinase (ERK)1/2, p38-mitogen-activated protein kinase (p38MAPK), and MAPK kinase-1 (MEK1). Pretreatment with PD98059, an inhibitor of ERK1/2, significantly decreased LPS-induced TLR2 and SP-A mRNA expression.

Berberine chloride mediates its anti-leishmanial activity via differential regulation of the mitogen activated protein kinase pathway in macrophages

Background

A complex interplay between Leishmania and macrophages influences parasite survival and necessitates disruption of signaling molecules, eventually resulting in impairment of macrophage function. In this study, we demonstrate the immunomodulatory activity of Berberine chloride in Leishmania infected macrophages.

Principal Findings

The IC₅₀ of Berberine chloride, a quaternary isoquinoline alkaloid was tested in an amastigote macrophage model and its safety index measured by a cell viability assay. It eliminated intracellular amastigotes, the IC₅₀ being 2.8 fold lower than its IC₅₀ in promastigotes (7.10 µM vs. 2.54 µM) and showed a safety index >16. Levels of intracellular and extracellular nitric oxide (NO) as measured by flow cytometry and Griess assay respectively showed that Berberine chloride in Leishmania infected macrophages increased production of NO. Measurement of the mRNA expression of iNOS, IL-12 and IL-10 by RT-PCR along with levels of IL-12p40 and IL-10 by ELISA showed that in infected macrophages, Berberine chloride enhanced expression of iNOS and IL-12p40, concomitant with a downregulation of IL-10. The phosphorylation status of extracellular signal related kinase (ERK1/2) and p38 mitogen activated protein kinase (p38 MAPK) was studied by western blotting. In infected macrophages, Berberine chloride caused a time dependent activation of p38 MAPK along with deactivation of ERK1/2; addition of a p38 MAPK inhibitor SB203580 inhibited the increased generation of NO and IL-12p40 by Berberine chloride as also prevented its decrease of IL-10.

Conclusions

Berberine chloride modulated macrophage effector responses via the mitogen activated protein kinase (MAPK) pathway, highlighting the importance of MAPKs as an antiparasite target.

Isolation of immunomodulatory triterpene acids from a standardized rose hip powder (Rosa canina L.)

A previously published systematic review and a metaanalysis have concluded that the consumption of standardized rose hip powder (Rosa canina L.) can reduce pain in osteoarthritis patients. Synovial inflammation has been suggested to play an important role in the pathogenesis of osteoarthritis and mainly to involve infiltration of the synovial membrane by macrophages. Therefore, the immunomodulatory effect of standardized rose hip powder of Rosa canina L. was investigated and active principles isolated using the Mono Mac 6 cell line as a model for human macrophages. Treatment of Mono Mac 6 cells with the residue of a crude dichloromethane extract of rose hip powder significantly and concentration dependently inhibited the lipopolysaccharide induced interleukin-6 release. Through bioassay-guided fractionation the immunomodulatory effect of the dichloromethane extract was correlated to a mixture of three triterpene acids; oleanolic acid, betulinic acid and ursolic acid (IC(50) 21 ± 6 µm). Further studies revealed that only oleanolic acid and ursolic acid, but not betulinic acid, could inhibit the lipopolysaccharide induced interleukin-6 release from Mono Mac 6 cells when tested separately. Combination of either oleanolic acid or ursolic acid with betulinic acid enhanced the immunomodulatory effect of the two triterpene acids.

Pneumococcal peptidoglycan-polysaccharides regulate Toll-like receptor 2 in the mouse middle ear epithelial cells

Toll-like receptor 2 (TLR2) plays a key role in the host defense against Gram staining positive (Gram) bacteria and their cell wall envelope components. However, little is known about the expression of TLR2 in the middle ear under otitis media (OM) conditions, and its role in the persistent otitis media with effusion (OME). In this study, we demonstrated that the pneumococcal cell wall component, peptidoglycan-polysaccharides (PGPS), activated the expression of TLR2 in the middle ear epithelial cells through the nuclear factor kappa B (NF-κB)-cytokine signaling pathway while I kappa B alpha mutant (IκBαM), a dominant negative inhibitor of NF-κB, abrogated the expression of TLR2 induced by PGPS. This study suggests that the existence of residual PGPS may maintain a low profile of cytokine production in the middle ear mucosa and thus contribute to the pathogenesis of OME.

Sulfuretin protects against cytokine-induced beta-cell damage and prevents streptozotocin-induced diabetes

NF-kappaB activation has been implicated as a key signaling mechanism for pancreatic beta-cell damage. Sulfuretin is one of the main flavonoids produced by Rhus verniciflua, which is reported to inhibit the inflammatory response by suppressing the NF-kappaB pathway. Therefore, we isolated sulfuretin from Rhus verniciflua and evaluated if sulfuretin could inhibit cytokine- or streptozotocin-induced beta-cell damage. Rat insulinoma RINm5F cells and isolated rat islets were treated with IL-1 beta and IFN-gamma to induce cytotoxicity. Incubation of cells and islets with sulfuretin resulted in a significant reduction of cytokine-induced NF-gamma B activation and its downstream events, iNOS expression, and nitric oxide production. The cytotoxic effects of cytokines were completely abolished when cells or islets were pretreated with sulfuretin. The protective effect of sulfuretin was further demonstrated by normal insulin secretion of cytokine-treated islets in response to glucose. Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was further evidenced by immunohistochemical staining of islets. However, the diabetogenic effects of streptozotocin were completely prevented when mice were pretreated with sulfuretin. The anti-diabetogenic effects of sulfuretin were also mediated by suppression of NF-kappaB activation. Collectively, these results indicate that sulfuretin may have therapeutic value in preventing beta-cell damage.

Inhibition of nuclear factor κB regresses cardiac hypertrophy by modulating the expression of extracellular matrix and adhesion molecules

Myocardial remodeling denotes a chronic pathological condition of dysfunctional myocardium that occurs in cardiac hypertrophy (CH) and heart failure (HF). Reactive oxygen species (ROS) are major initiators of excessive collagen and fibronectin deposition in cardiac fibrosis. Increased production of ROS and nuclear factor κB (NF-κB) activation provide a strong link between oxidative stress and extracellular matrix (ECM) remodeling in cardiac hypertrophy. The protective inhibitory actions of pyrrolidine dithiocarbamate (PDTC), a pharmacological inhibitor of NF-κB and a potent antioxidant, make this a good agent to evaluate the role of inhibition of NF-κB and prevention of excessive ECM deposition in maladaptive cardiac remodeling during HF. In this report, we used a transgenic mouse model (Myo-Tg) that has cardiac-specific overexpression of myotrophin. This overexpression of myotrophin in the Myo-Tg model directs ECM deposition and increased NF-κB activity, which result in CH and ultimately HF. Using the Myo-Tg model, our data showed upregulation of profibrotic genes (including collagen types I and III, connective tissue growth factor, and fibronectin) in Myo-Tg mice, compared to wild-type mice, during the progression of CH. Pharmacological inhibition of NF-κB by PDTC in the Myo-Tg mice resulted in a significant reduction in cardiac mass, NF-κB activity, and profibrotic gene expression and improved cardiac function. To the best of our knowledge, this is the first report of ECM regulation by inhibition of NF-κB activation by PDTC. The study highlights the importance of the NF-κB signaling pathway and therapeutic benefits of PDTC treatment in cardiac remodeling.

The effect of acute hyperoxia in vivo on NF kappa B expression in human PBMC

The mechanisms of hyperbaric oxygen (HBO) therapy have not been fully elucidated. It is presumed that breathing 100% oxygen at pressure generates free radicals and the cellular response to these may confer protection. A crucial signalling molecule, nuclear transcription factor kappa B (NFκB), translocates from the cytoplasm to the nucleus and activates a raft of pathways in response to various stimuli, and plays a role in inflammatory processes. This study focussed upon the expression of NFκB in isolated human peripheral blood mononuclear cells (PBMC) following HBO. Ten healthy male volunteers underwent a single HBO treatment, breathing 100% oxygen at a pressure of 2.8 ATA for 1 h. EDTA blood samples were taken pre-, post- and 4-h post-HBO. PBMC were isolated, nuclear extracts prepared and assayed using a NFkBp50 transcription factor ELISA. Mean NFκB expression of 0.27 (0.20-0.34, 95%CI) absorbance units (mg protein)(-1) was observed pre-HBO and this increased to 0.29 (0.20-0.38, 95%CI) immediately post-HBO. A significant increase in NFκB expression within PBMC was observed 4-h post-HBO, in comparison to pre-HBO (mean 0.38, 0.30-0.47, 95%CI, p = 0.027). This study demonstrates that HBO induces NFκB activation in human PBMC, which could be a crucial step in the mechanism of HBO treatment.

Connecting chronic and recurrent stress to vascular dysfunction: no relaxed role for the renin-angiotensin system

The renin-angiotensin system (RAS) is classically considered to be a protective system for volume balance and is activated during states of volume depletion. Interestingly, one of the major pathways activating the system is the sympathetic nervous system, also the primary mediator of the acute stress response. When one further examines the cells mediating the immune site of the response, which is primarily an inflammatory response leading to defense at a locally injured area, these cells all express the ANG II type 1 receptor (AGTR1). Scattered throughout the literature are reports indicating that acute and chronic stress can activate renin and increase plasma levels of components of the RAS. Moreover, there are reports describing that ANG II can modulate the distribution and function of immune cells. Since the inflammatory response is also implicated to be central in the initiation and progression of vascular damage, we propose in this review that recurrent acute stress and chronic stress can induce a state with inflammation, due to ANG II-mediated activation of inflammatory cells, specifically monocytes and lymphocytes. Such a proposal would explain a lot of the observations regarding RAS components in inflammatory cells. Despite its attractiveness, substantial research in this area would be required to substantiate this hypothesis.

Detection of ubiquityl-calmodulin conjugates with a novel high-molecular weight ubiquitylprotein-isopeptidase in rabbit tissues

The selective degradation of many proteins in eukaryotic cells is carried out by the ubiquitin system. In this pathway, proteins are targeted for degradation by covalent ligation to ubiquitin, a highly conserved protein [1]. Ubiquitylated proteins were degraded by the 26S proteasome in an ATP-depended manner. The degradation of ubiquitylated proteins were controlled by isopeptidase cleavage. A well characterised system of ubiquitylation and deubiquitylation is the calmodulin system in vitro [2]. Detection of ubiquityl-calmodulin conjugtates in vivo have not been shown so far. In this article we discuss the detection of ubiquitin calmodulin conjugates in vivo by incubation with a novel high-molecular weight ubiquitylprotein-isopeptidase in rabbit tissues. Proteins with a molecular weight of ubiquityl-calmodulin conjugates could be detected in all organs tested. Incubation with ubiquitylprotein-isopeptidase showed clearly a decrease of ubiquitin calmodulin conjugates in vivo with an origination of unbounded ubiquitin. These results suggest that only few ubiquitin calmodulin conjugates exist in rabbit tissues.

Down-regulation of endothelial TLR4 signalling after apo A-I gene transfer contributes to improved survival in an experimental model of lipopolysaccharide-induced inflammation

The protective effects of high-density lipoprotein (HDL) under lipopolysaccharide (LPS) conditions have been well documented. Here, we investigated whether an effect of HDL on Toll-like receptor 4 (TLR4) expression and signalling may contribute to its endothelial-protective effects and to improved survival in a mouse model of LPS-induced inflammation and lethality. HDL cholesterol increased 1.7-fold (p < 0.005) and lung endothelial TLR4 expression decreased 8.4-fold (p < 0.005) 2 weeks after apolipoprotein (apo) A-I gene transfer. Following LPS administration in apo A-I gene transfer mice, lung TLR4 and lung MyD88 mRNA expression, reflecting TLR4 signalling, were 3.0-fold (p < 0.05) and 2.1-fold (p < 0.05) lower, respectively, than in LPS control mice. Concomitantly, LPS-induced lung neutrophil infiltration, lung oedema and mortality were significantly attenuated following apo A–I transfer. In vitro, supplementation of HDL or apo A–I to human microvascular endothelial cells-1 24 h before LPS administration reduced TLR4 expression, as assessed by fluorescent-activated cell sorting, and decreased the LPS-induced MyD88 mRNA expression and NF-κB activity, independently of LPS binding. In conclusion, HDL reduces TLR4 expression and signalling in endothelial cells, which may contribute significantly to the protective effects of HDL in LPS-induced inflammation and lethality.

Preparation and characterization of chitosan-heparin composite matrices for blood contacting tissue engineering

Chitosan has been widely used for biomaterial scaffolds in tissue engineering because of its good mechanical properties and cytocompatibility. However, the poor blood compatibility of chitosan has greatly limited its biomedical utilization, especially for blood contacting tissue engineering. In this study, we exploited a polymer blending procedure to heparinize the chitosan material under simple and mild conditions to improve its antithrombogenic property. By an optimized procedure, a macroscopically homogeneous chitosan-heparin (Chi-Hep) blended suspension was obtained, with which Chi-Hep composite films and porous scaffolds were fabricated. X-ray photoelectron spectroscopy and sulfur elemental analysis confirmed the successful immobilization of heparin in the composite matrices (i.e. films and porous scaffolds). Toluidine blue staining indicated that heparin was distributed homogeneously in the composite matrices. Only a small amount of heparin was released from the matrices during incubation in normal saline for 10 days. The composite matrices showed improved blood compatibility, as well as good mechanical properties and endothelial cell compatibility. These results suggest that the Chi-Hep composite matrices are promising candidates for blood contacting tissue engineering.

The cysteine protease domain of porcine reproductive and respiratory syndrome virus nonstructural protein 2 possesses deubiquitinating and interferon antagonism functions

Porcine reproductive and respiratory syndrome (PRRS) virus nonstructural protein 2 (nsp2) contains a cysteine protease domain at its N terminus, which belongs to the ovarian tumor (OTU) protease family. In this study, we demonstrated that the PRRSV nsp2 OTU domain antagonizes the type I interferon induction by interfering with the NF-kappaB signaling pathway. Further analysis revealed that the nsp2 OTU domain possesses ubiquitin-deconjugating activity. This domain has the ability to inhibit NF-kappaB activation by interfering with the polyubiquitination process of IkappaBalpha, which subsequently prevents IkappaBalpha degradation. To determine whether the nsp2 protein antagonist function can be ablated from the virus, we introduced point mutations into the OTU domain region by use of reverse genetics. The D458A, S462A, and D465A mutations targeting on a B-cell epitope in the OTU domain region generated the viable recombinant viruses, and the S462A and D465A mutants were attenuated for growth in cell culture. The OTU domain mutants were examined to determine whether mutations in the nsp2 OTU domain region altered virus ability to inhibit NF-kappaB activation. The result showed that certain mutations lethal to virus replication impaired the ability of nsp2 to inhibit NF-kappaB activation but that the viable recombinant viruses, vSD-S462A and vSD-D465A, were unable to inhibit NF-kappaB activation as effectively as the wild-type virus. This study represents a fundamental step in elucidating the role of nsp2 in PRRS pathogenesis and provides an important insight in future modified live-virus vaccine development.

Novel guggulsterone derivative GG-52 inhibits NF-kappaB signaling in intestinal epithelial cells and attenuates acute murine colitis

We already showed that the plant sterol guggulsterone has been reported to inhibit nuclear factor-kappaB (NF-kappaB) signaling in intestinal epithelial cells (IECs) and to attenuate dextran sulfate sodium (DSS)-induced colitis. This study investigates the anti-inflammatory effects of novel guggulsterone derivatives on IEC and preventive and therapeutic murine models of DSS-induced colitis. Novel guggulsterone derivates with high lipophilicity were designed and four derivates, including GG-46, GG-50B, GG-52, and GG-53, were synthesized. Two guggulsterone derivatives, GG-50B and GG-52, significantly inhibited the activated NF-kappaB signals and the upregulated expression of interleukin-8 (IL-8) in COLO 205 cells stimulated with tumor necrosis factor-alpha (TNF-alpha). Pretreatment with GG-50B and GG-52 attenuated the increased IkappaB kinase (IKK) and IkappaBalpha phsophorylation induced by TNF-alpha. In preventive and therapeutic models of murine colitis, administration of GG-52 significantly reduced the severity of DSS-induced colitis, as assessed by disease activity index, colon length, and histology. In contrast, GG-50B did not show a significant reduction in the colitis severity. Moreover, the efficacy on attenuating colitis by GG-52 was comparable to that by sulfasalazine or prednisolone. These results indicate that the novel guggulsterone derivative GG-52 blocks NF-kappaB activation in IEC and ameliorates DSS-induced acute murine colitis, which suggests that GG-52 is a potential therapeutic agent for the treatment of inflammatory bowel diseases.

NFkappaB, cytokines, TLR 3 and 7 expression in human end-stage HCV and alcoholic liver disease

BACKGROUND/AIMS

Conflicting observations exist concerning the role of nuclear factor kappa B (NFjB) in alcoholic liver disease (ALD) in animal models. To date no studies have examined this aspect in human liver tissue. We here assessed cytokines and toll-like receptors (TLRs) expressions in conjunction with NFkappaB activation in non-active end-stage human ALD compared with normal livers and hepatitis C virus (HCV) related end-stage disease.

METHODS

mRNA and protein expression were examined by quantitative PCR and Western blotting, DNA-binding by electrophoretic mobility shift assays and NFkappaB sub-cellular localization by immunofluorescent staining of livers.

RESULTS

NFkappaB mRNA and protein expression as well as strong DNA-binding were preserved in ALD but significantly down-regulated in HCV compared with normal livers. P50 immunofluorescence was found in hepatocytes and bile ducts in ALD and normal livers, whereas a shift was observed in p65 staining from non-parenchymal cells in normal livers to hepatocytes in ALD. NFkappaB responsive genes mRNA levels IkBalpha and interleukin 6 were significantly higher in ALD compared with HCV. Tumour necrosis factor alpha (TNFalpha), TLRs 3 and 7 mRNA were up-regulated in ALD and HCV compared with normal liver with TNFalpha and TLR7 being the highest in HCV. Strong induction of interferon beta was found in HCV but not in ALD or normal liver tissue.

CONCLUSIONS

Persistent NFkappaB activation together with high pro-inflammatory cytokine expression and upregulation of TLR3 and TLR7 is associated with end-stage ALD in humans and could contribute to disease progression even in absence of alcohol intake.

Leishmania major: anti-leishmanial activity of Nuphar lutea extract mediated by the activation of transcription factor NF-κB

Here we report the effect of a partially purified alkaloid fraction (NUP) of Nuphar lutea on nuclear factor kappa B (NF-κB) expression and studied its mechanism of toxicity against Leishmania major in C3H mice peritoneal macrophages. NUP was found to be a mixture of thermo-stable dimeric sesquiterpene thioalkaloids containing mainly thionupharidines. The anti-leishmanial activity was shown to be mediated through the activation of NF-κB and increased iNOS production. Additionally, the nitric oxide inhibitor, N(G)-monomethyl-L-arginine (0.5mM) totally reverted the anti-leishmanial effect of NUP (0.25 and 0.5μg/ml). NUP was also shown to act as an anti-oxidant, almost completely inhibiting the macrophage respiratory burst activity. However, no elevated lysozyme (EC3.2.1.17) or β-galactosidase (EC3.2.1.23) activities were demonstrated in macrophages treated with NUP. This study suggests, that the activity of NUP is mediated by NF-κB activation and the production of nitric oxide which is dependent on the L-arginine:NO pathway.

Molecular basis of lysophosphatidic acid-induced NF-κB activation

PKC, β-arrestin 2, CARMA3, BCL10, MALT1, TRAF6 and MEKK3 are signaling proteins that have a key role in G protein-coupled receptor (GPCR)-mediated activation of nuclear factor-κB (NF-κB) pathway in nonhematopoietic cells in response to lysophosphatidic acid (LPA) stimulation. The PKC, β-arrestin 2, CARMA3-BCL10-MALT1-TRAF6 signalosome, and MEKK3 functions as a link between GPCR signaling and IKK-NF-κB activation. Here we briefly summarize recent progress in the understanding of the molecular and biological functions of these proteins in GPCR-mediated NF-κB activation in nonhematopoietic cells.

Inhibitory effect of glycoprotein isolated from Opuntia ficus-indica var. saboten MAKINO on activities of allergy-mediators in compound 48/80-stimulated mast cells

The present study was performed to investigate the anti-allergy potentials of glycoprotein (90kDa) isolated from Opuntia ficus-indica var. saboten MAKINO (OFI glycoprotein) in vivo (ICR mice) and in vitro (RBL-2H3 cells). At first, to know whether the OFI glycoprotein has an inhibitory ability for allergy in vivo, we evaluated the activities of allergy-related factors such as histamine and beta-hexosaminidase release, lactate dehydrogenase (LDH), and interleukin 4 (IL-4) in compound 48/80 (8 ml/kg BW)-treated ICR mice. After that, we studied to found the effect for anti-allergy in vitro such as nuclear factor kappa B (NF-kappaB) and inducible nitric oxide synthase (iNOS), extracellular signal-regulated kinase (ERK) 1/2, arachidonic acid, and cyclooxygenase-2 (COX-2) in compound 48/80 (5 microg/ml)-treated RBL-2H3 cells. Our results showed that the OFI glycoprotein (5 mg/kg) inhibited histamine and beta-hexosaminidase release, lactate dehydrogenase (LDH), and interleukin 4 (IL-4) in mice serum. Also OFI glycoprotein (25 microg/ml) has suppressive effects on the expression of MAPK (ERK1/2), and on protein expression of anti-allergic proteins (iNOS and COX-2). Thus, we speculate that the OFI glycoprotein is an example of natural compound that blocks anti-allergic signal transduction pathways.

Protein phosphatase 2A acts as a mitogen-activated protein kinase kinase kinase 3 (MEKK3) phosphatase to inhibit lysophosphatidic acid-induced IkappaB kinase beta/nuclear factor-kappaB activation

MEKK3 is a central intermediate signaling component in lysophosphatidic acid (LPA)-induced activation of the nuclear factor-kappaB (NF-kappaB). However, the precise mechanism for the termination of MEKK3 kinase activity is not fully understood. Using a functional genomic approach, we have identified a protein serine/threonine phosphatase, protein phosphatase 2A (PP2A), as a MEKK3 phosphatase. Overexpression of PP2A catalytic subunit (PP2Ac) beta-isoform results in dephosphorylation of MEKK3 at Thr-516 and Ser-520 and termination of MEKK3-mediated NF-kappaB activation. PP2Ac associates with the phosphorylated form of MEKK3 and the interaction between PP2Ac and MEKK3 is induced by LPA in a transient fashion in the cells. Furthermore, knockdown of PP2Ac expression enhances LPA-induced MEKK3-mediated IkappaB kinase beta (IKKbeta) phosphorylation and NF-kappaB activation. These data suggest that PP2A plays an important role in the termination of LPA-mediated NF-kappaB activation through dephosphorylating and inactivating MEKK3.

Differential effect of covalent protein modification and glutathione depletion on the transcriptional response of Nrf2 and NF-kappaB

Liver injury associated with exposure to therapeutic agents that undergo hepatic metabolism can involve the formation of reactive metabolites. These may cause redox perturbation which can result in oxidative stress as well as protein modification leading to activation or inhibition of cellular transcriptional responses. Nevertheless, the effects of these challenges on more than one transcriptional pathway simultaneously remain unclear. We have investigated two transcription factors known to be sensitive to electrophilic stress and redox perturbation, Nrf2 and NF-κB, in mouse liver cells. Cellular stress was induced by the probes: N-acetyl-p-benzoquinineimine (NAPQI), the reactive metabolite of acetaminophen; dinitrochlorobenzene (DNCB), a model electrophile; and buthionine (S,R)-sulfoximine (BSO), an inhibitor of glutamate-cysteine ligase. NAPQI, DNCB and BSO can all cause glutathione (GSH) depletion; however only NAPQI and DNCB can covalently bind proteins. We also employed RNAi to manipulate Keap1 (the inhibitor of Nrf2), Nrf2 itself and NF-κB-p65, to understand their roles in the response to drug stress. All three chemicals induced Nrf2, but NF-κB binding activity was only increased after BSO treatment. In fact, NF-κB binding activity decreased after exposure to NAPQI and DNCB. While RNAi depletion of Keap1 led to reduced toxicity following exposure to DNCB, depletion of Nrf2 and NF-κB augmented toxicity. Interestingly, increased Nrf2 caused by Keap1 depletion was reversed by co-depletion of NF-κB. We demonstrate that Keap1/Nrf2 and NF-κB respond differently to electrophiles that bind proteins covalently and the redox perturbation associated with glutathione depletion, and that crosstalk may enable NF-κB to partly influence Nrf2 expression during cellular stress.

Neurotrophins regulate bone marrow stromal cell IL-6 expression through the MAPK pathway

BACKGROUND

The host's response to infection is characterized by altered levels of neurotrophins and an influx of inflammatory cells to sites of injured tissue. Progenitor cells that give rise to the differentiated cellular mediators of inflammation are derived from bone marrow progenitor cells where their development is regulated, in part, by cues from bone marrow stromal cells (BMSC). As such, alteration of BMSC function in response to elevated systemic mediators has the potential to alter their function in biologically relevant ways, including downstream alteration of cytokine production that influences hematopoietic development.

METHODOLOGY/PRINCIPAL FINDINGS

In the current study we investigated BMSC neurotrophin receptor expression by flow cytometric analysis to determine differences in expression as well as potential to respond to NGF or BDNF. Intracellular signaling subsequent to neurotrophin stimulation of BMSC was analyzed by western blot, microarray analysis, confocal microscopy and real-time PCR. Analysis of BMSC Interleukin-6 (IL-6) expression was completed using ELISA and real-time PCR.

CONCLUSION

BMSC established from different individuals had distinct expression profiles of the neurotrophin receptors, TrkA, TrkB, TrkC, and p75(NTR). These receptors were functional, demonstrated by an increase in Akt-phosphorylation following BMSC exposure to recombinant NGF or BDNF. Neurotrophin stimulation of BMSC resulted in increased IL-6 gene and protein expression which required activation of ERK and p38 MAPK signaling, but was not mediated by the NFkappaB pathway. BMSC response to neurotrophins, including the up-regulation of IL-6, may alter their support of hematopoiesis and regulate the availability of inflammatory cells for migration to sites of injury or infection. As such, these studies are relevant to the growing appreciation of the interplay between neurotropic mediators and the regulation of hematopoiesis.

USP11 negatively regulates TNFalpha-induced NF-kappaB activation by targeting on IkappaBalpha

IkappaBalpha serves as a central anchoring molecule in the sequestration of NF-kappaB transcription factor in the cytoplasm. Ubiquitination-mediated IkappaBalpha degradation immediately precedes and is required for NF-kappaB nuclear translocation and activation. However, the precise mechanism for the deubiquitination of IkappaBalpha is still not fully understood. Using a proteomic approach, we have identified Ubiquitin Specific Peptidase 11 (USP11) as an IkappaBalpha associated deubiquitinase. Overexpression of USP11 inhibits IkappaBalpha ubiquitination. Recombinant USP11 catalyzes deubiquitination of IkappaBalpha in vitro. Moreover, knockdown of USP11 expression enhances TNFalpha-induced IkappaBalpha ubiquitination and NF-kappaB activation. These data demonstrate that USP11 plays an important role in the downregulation of TNFalpha-mediated NF-kappaB activation through modulating IkappaBalpha stability. In addition, overexpression of a catalytically inactive USP11 mutant partially inhibits TNFalpha- and IKKbeta-induced NF-kappaB activation, suggesting that USP11 also exerts a non-catalytic function in its negative regulation of TNFalpha-mediated NF-kappaB activation. Thus, IkappaBalpha ubiquitination and deubiquitination processes function as a Yin-Yang regulatory mechanism on TNFalpha-induced NF-kappaB activation.

The effect of vitamin e succinate on ischemia reperfusion injury

Ischemia-reperfusion (I/R) injury is, in part, related to the burst of reactive oxygen species (ROS) generated after reperfusion. Vitamin E has been shown to exert its biological effects as an antioxidant, inhibiting the ROS. In this report, the effect of Vitamin E succinate (VES) on ischemia/reperfusion injury and NF-κB expression was studied in a rat skeletal muscle model during reperfusion following a 4-h ischemic period. The study group consisted of muscle flaps infused with 150 mg/kg of VES given intraperitoneally 1 h post-initiation of ischemia. Muscle viability based on nitroblue tetrazolium staining, edema, and Doppler blood flow was measured in a control and a study group. Muscle samples were analyzed by standard gel shift assay. The VES experimental group showed an increase in muscle viability compared to controls (average of 44.675% versus 31.925%, respectively, p = 0.0415). Blood flow, measured by Doppler 24 h after reperfusion, was increased in the VES study group compared to controls (10.3 vs. 5.1 ml/g/s p = 0.00355). Additionally, the VES group showed a trend of decreasing edema compared with the control; however, not at a level that was statistically significant (p = 0.1267). The VES-treated group showed a decreased expression of NF-κB as compared to controls (p < 0.05). These results show that vitamin E succinate has a protective effect in preventing I/R injury as measured by increased muscle viability and reperfusion blood flow. Vitamin E can exert its efforts as an antioxidant as well as other biological roles, including inhibition of NF-κB.

Protective effect of glycoprotein isolated from Ulmus davidiana Nakai on carbon tetrachloride-induced mouse liver injury

This study was carried out to evaluate the hepatoprotective activity of glycoprotein isolated from the stems of Ulmus davidiana Nakai (UDN), which has been used as an anti-inflammatory agent in folk medicine. We evaluated lipid peroxidation in glucose/glucose oxidase (G/GO)-induced BNL CL.2 cells and measured thiobarbituric acid reactive substances (TBARS), lactate dehydrogenase (LDH), nitric oxide (NO), antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)), activity of cytotoxic-related signals (hepatic cytochrome c, nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1)) and levels of plasma lipids (triglyceride (TG) and total cholesterol (TC)) in carbon tetrachloride (CCl4, 1.0 mL kg−1)-induced A/J mouse. The results in G/GO-induced BNL CL.2 cells showed that UDN glycoprotein had a dose-dependent inhibitory effect on lipid peroxidation. The results in carbon tetrachloride (CCl4, 1.0 mL kg−1)-induced A/J mouse indicated that treatment with UDN glycoprotein (40 mg kg−1) lowered LDH activity and TBARS formation, and increased NO production and antioxidant enzymes activity, compared with control. Also, our finding from CCl4-treated mice after pretreatment with UDN glycoprotein demonstrated that the activity of cytotoxic-related signals decreased but the levels of plasma lipids increased, compared with CCl4 treatment alone. Here, we speculate that UDN glycoprotein has a protective character to CCl4-induced mouse liver injury.

Ischemic injury enhances dendritic cell immunogenicity via TLR4 and NF-kappa B activation

Ischemic (isc) injury during the course of transplantation enhances the immunogenicity of allografts and thus results in poorer graft outcome. Given the central role of dendritic cells (DCs) in mounting alloimmune responses, activation of donor DCs by ischemia may have a primary function in the increased immunogenicity of isc allografts. In this study, we sought to investigate the effect of ischemia on DC activity in vitro. Following induction of ischemia, bone marrow-derived DCs were shown to augment allogeneic T cell proliferation as well as the IFN-gamma response. Isc DCs produced greater levels of IL-6, and isc insult was concurrent with NF-kappaB activation. TLR4 ligation was also shown to occur in isc DCs, most likely in response to the endogenous ligand heat shock protein 70, which was found to be elevated in DCs following isc injury, and lack of TLR4 abrogated the observed effects of isc DCs. As compared with control DCs, isc DCs injected into the footpads of mice demonstrated enhanced migration, which was concomitant with increased recipient T cell activity. Moreover, isc DCs underwent a greater degree of apoptosis in the lymph nodes of injected mice, which may further demonstrate enhanced immunogenicity of isc DCs. We thus show that isc injury of DCs enhances DC function, augments the allogeneic T cell response, and occurs via ligation of TLR4, followed by activation of NF-kappaB. These data may serve to identify novel therapeutic targets to attenuate graft immunogenicity following ischemia.

Calcium channel blockers differentially modulate cytokine production by peripheral blood mononuclear cells

BACKGROUND

Calcium channel blockers (CCB) are known to modulate immune reactions, so the present study was performed to examine the effects of various CCBs that have shown different effects on transcription factors and on the production of pro-inflammatory cytokines by human peripheral blood mononuclear cells (PBMC).

METHODS AND RESULTS

PBMC from healthy volunteers were isolated by Ficoll-paque density centrifugation. To study the effect of CCBs, the PBMC were stimulated with lipopolysaccharide or concanavalin A. After 24 h of incubation, the supernatants were harvested and the interleukin (IL)-1alpha, -1beta, and -6, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma levels were determined by specific enzyme-linked immunosorbent assay. The production of IL-1alpha and -1beta stimulated with lipopolysaccharide was significantly increased in the presence of amlodipine. In contrast, nifedipine and verapamil suppressed the production of IL-1beta, TNF-alpha, and IFN-gamma. Amlodipine and diltiazem significantly increased production of IL-1alpha stimulated with concanavalin A. Nifedipine inhibited production of IL-1alpha, IL-6, and IFN-gamma. Verapamil suppressed production of IFN-gamma.

CONCLUSIONS

Differential modulation of cytokine production was seen with various CCBs, and the suppressive effect of nifedipine was most prominent.

A preferential p110alpha/gamma PI3K inhibitor attenuates experimental inflammation by suppressing the production of proinflammatory mediators in a NF-kappaB-dependent manner

A promising therapeutic approach to diminish pathological inflammation is to inhibit the increased production and/or biological activity of proinflammatory cytokines (e.g., TNF-alpha, IL-6). The production of proinflammatory cytokines is controlled at the gene level by the activity of transcription factors, such as NF-kappaB. Phosphatidylinositol 3-kinase (PI3K), a lipid kinase, is known to induce the activation of NF-kappaB. Given this, we hypothesized that inhibitors of PI3K activation would demonstrate anti-inflammatory potential. Accordingly, we studied the effects of a preferential p110alpha/gamma PI3K inhibitor (compound 8C; PIK-75) in inflammation-based assays. Mechanism-based assays utilizing human cells revealed that PIK-75-mediated inhibition of PI3K activation is associated with dramatic suppression of downstream signaling events, including AKT phosphorylation, IKK activation, and NF-kappaB transcription. Cell-based assays revealed that PIK-75 potently and dose dependently inhibits in vitro and in vivo production of TNF-alpha and IL-6, diminishes the induced expression of human endothelial cell adhesion molecules (E-selectin, ICAM-1, and VCAM-1), and blocks human monocyte-endothelial cell adhesion. Most importantly, PIK-75, when administered orally in a therapeutic regimen, significantly suppresses the macroscopic and histological abnormalities associated with dextran sulfate sodium-induced murine colitis. The efficacy of PIK-75 in attenuating experimental inflammation is mediated, at least in part, due to the downregulation of pertinent inflammatory mediators in the colon. Collectively, these results provide first evidence that PIK-75 possesses anti-inflammatory potential. Given that PIK-75 is known to exhibit anti-cancer activity, the findings from this study thus reinforce the cross-therapeutic functionality of potential drugs.

Phosphorylation of Thr-516 and Ser-520 in the kinase activation loop of MEKK3 is required for lysophosphatidic acid-mediated optimal IkappaB kinase beta (IKKbeta)/nuclear factor-kappaB (NF-kappaB) activation

MEKK3 serves as a critical intermediate signaling molecule in lysophosphatidic acid-mediated nuclear factor-kappaB (NF-kappaB) activation. However, the precise regulation for MEKK3 activation at the molecular level is still not fully understood. Here we report the identification of two regulatory phosphorylation sites at Thr-516 and Ser-520 within the kinase activation loop that is essential for MEKK3-mediated IkappaB kinase beta (IKKbeta)/NF-kappaB activation. Substitution of these two residues with alanine abolished the ability of MEKK3 to activate IKKbeta/NF-kappaB, whereas replacement with acidic residues rendered MEKK3 constitutively active. Furthermore, substitution of these two residues with alanine abolished the ability of MEKK3 to mediate lysophosphatidic acid-induced optimal IKKbeta/NF-kappaB activation.