Interleukin-4 down-regulates both forms of tumor necrosis factor receptor and receptor-mediated apoptosis, NF-kappaB, AP-1, and c-Jun N-terminal kinase. Comparison with interleukin-13

IL-4 Downregulates PD-L1 Level Via SOCS1 Upregulation-Induced JNK Deactivation to Enhance Antitumor Immunity in In Vitro Colorectal Cancer

Interleukin-4 (IL-4) controls cell growth and immune system regulation in tumorigenesis and can inhibit the growth of colon cancer cell lines, but the possible mechanism is unclear. In this study, we investigated the possible mechanism of IL-4 in colorectal cancer (CRC) through in vitro experiments. CRC cells received treatment with IL-4 (50 ng/mL), investigating the suppressor of cytokine signaling 1 (SOCS1)-related mechanism underlying the role of IL-4 in the progression and immunosuppression of CRC. The malignant processes of CRC cells and CD8+T cell-mediated immune response in CRC cells were determined by CCK-8, Transwell, wound healing, and flow cytometry assays. Programmed death ligand 1 (PD-L1), SOCS1 expressions, and c-Jun N-terminal kinase (JNK) activation in CRC cells were analyzed by quantitative reverse transcription polymerase chain reaction and/or Western blot. IL-4 repressed the malignant processes, yet promoted the apoptosis of CRC cells. Besides, IL-4 downregulated PD-L1 level, upregulated SOCS1 level, and restrained JNK activation in CRC cells, while enhancing CRC cell-killing effect of CD8+T cells. IL-4-induced effects on the aforementioned malignant processes of CRC cells and the killing effect of CD8+T cells toward CRC cells were all reversed when SOCS1 was knocked down in the CRC cells. IL-4 downregulates PD-L1 level via SOCS1 upregulation-induced JNK deactivation to enhance antitumor immunity in in vitro CRC. The study provides a theoretical basis for the clinical application of IL-4 in antitumor immunity in CRC.

IL-4 Switches Microglia/macrophage M1/M2 Polarization and Alleviates Neurological Damage by Modulating the JAK1/STAT6 Pathway Following ICH

Inflammatory damage following ICH is often attributed to microglia/macrophage activation. In many diseases, IL-4 has been proven to switch microglia/macrophages from the pro-inflammatory to the anti-inflammatory subtype. However, the role and underlying mechanism of IL-4 in ICH, especially in neuroprotection, remain unknown. In our study, we constructed a microglia/macrophage polarization model in BV2 cells to verify that the M2 shift of microglia/macrophages was mediated by JAK1/STAT6 after IL-4 treatment and then revealed that in vitro administration of IL-4 decreased M1 markers, pro-inflammatory cytokines and neuroapoptosis markers but significantly increased M2 markers and anti-inflammatory cytokines. Using an ICH model in mice, we observed that IL-4 administration decreased neurological deficits, brain edema and infarct lesions induced by ICH. We verified that IL-4 mediates inflammation by regulating M1/M2 polarization in ICH and explored the underlying mechanism. Furthermore, we discovered that pathway components and apoptosis-related proteins showed consistent trends based on their respective roles, and inferred that the process that TNF-α activates caspase-3 may be the crosstalk that microglia phagocytosis developed into accelerate apoptosis of cells in ICH. In conclusion, our study demonstrates that IL-4 may promote M2 microglia/macrophage polarization partly through the JAK1/STAT6 pathway to alleviate neuroinflammation after ICH.

Analysis of serum inflammatory mediators in type 2 diabetic patients and their influence on renal function

Aim

To evaluate the serum concentrations of inflammatory mediators in patients with type 2 diabetes mellitus (T2DM) with or without renal alteration (RA) function.

Methods

Serum samples from 76 patients with T2DM and 24 healthy individuals were selected. Patients with T2DM were divided into two groups according to eGFR (> or < 60mL/min/1.73m²). Cytokines, chemokines and adipokines levels were evaluated using the Multiplex immunoassay and ELISA.

Results

TNFR1 and leptin were higher in the T2DM group with RA than in the T2DM group without RA and control group. All patients with T2DM showed increased resistin, IL-8, and MIP-1α compared to the control group. Adiponectin were higher and IL-4 decreased in the T2DM group with RA compared to the control group. eGFR positively correlated with IL-4 and negatively with TNFR1, TNFR2, and leptin in patients with T2DM. In the T2DM group with RA, eGFR was negatively correlated with TNFR1 and resistin. TNFR1 was positively correlated with resistin and leptin, as well as resistin with IL-8 and leptin.

Conclusion

Increased levels of TNFR1, adipokines, chemokines and decrease of IL-4 play important role in the inflammatory process developed in T2DM and decreased renal function. We also suggest that TNFR1 is a strong predictor of renal dysfunction in patients with T2DM.

Inflammation induced loss of skeletal muscle

Inflammation is an important contributor to the pathology of diseases implicated in skeletal muscle dysfunction. A number of diseases and disorders including inflammatory myopathies and Chronic Obstructive Pulmonary Disorder (COPD) are characterized by chronic inflammation or elevation of the inflammatory mediators. While these disease states exhibit different pathologies, all have in common the loss of skeletal muscle mass and a deregulated skeletal muscle physiology. Pro-inflammatory cytokines are key contributors to chronic inflammation found in many of these diseases. This section of the review focuses on some of the known inflammatory disorders like COPD, Rheumatoid Arthritis (RA) and inflammatory myopathies that display skeletal muscle atrophy and also provides the reader an overview of the mediators of inflammation, their signaling pathways, and mechanisms of action. This article is part of a Special Issue entitled "Muscle Bone Interactions".

Amelioration of trinitrobenzene sulfonic acid-induced colitis in mice by liquiritigenin

BACKGROUND AND AIM

The anti-inflammatory effects of liquiritigenin, a major flavonoid isolated from Glycyrrhizae uralensis, have been reported in many inflammation models. However, its protective effects have not been reported in a colitis model. This study investigated the anti-inflammatory effect and mechanism of liquiritigenin for trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice.

METHODS

Male mice imprinting control regions (ICR) were randomly divided into five groups: normal, TNBS-induced colitis, colitis treated with liquiritigenin at low dose (10 mg/kg) and high dose (20 mg/kg), or mesalazine (10 mg/kg). TNBS colitis induction was performed except for in the normal group, and they were treated with liquiritigenin or mesalazine except control group. The treatment effect was measured after three days treatment, by body weight, colon length, macroscopic score, histological score, levels of cytokines (tumor necrosis factor-α, interleukin [IL]-1β, IL-6, and IL-10) in colon tissue as well as the nuclear factor kappa-light-chain-enhancer pathway of activated B cells (NF-κB) activation.

RESULTS

Mice treated with high-dose liquiritigenin showed significant body weight gain, inhibition of colon shortening, protective effect on histological damages, and myeloperoxidase activity of colon tissue compared with the control group. Furthermore, mice treated with high-dose liquiritigenin experienced significantly suppressed tumor necrosis factor-α, IL-1β, and IL-6 as well as enhanced IL-10 expression (all P < 0.05). High-dose liquiritigenin treatment group showed significant decreases in TNBS-induced phosphorylation of IKKβ, p65, and IκB-α.

CONCLUSION

Liquiritigenin may ameliorate TNBS-induced colitis in mice by suppressing expression of pro-inflammatory cytokines through NF-κB pathway.

Protective Effect of Flos Lonicerae against Experimental Gastric Ulcers in Rats: Mechanisms of Antioxidant and Anti-Inflammatory Action

Flos Lonicerae is one of the oldest and most commonly prescribed herbs in Eastern traditional medicine to treat various inflammatory diseases. In the present study, we investigated the effects of ethyl acetate fraction of Flos Lonicerae (GC-7101) on experimental gastric ulcer models and its mechanisms of action in gastric ulcer healing. The pharmacological activity of GC-7101 was investigated in rats on HCl/EtOH, indomethacin, water immersion restraint stress induced acute gastric ulcer, and acetic-acid-induced subchronic gastric ulcer. To determine its gastroprotective mechanisms, gastric wall mucus secretion, mucosal PGE₂, mucosal NO content, nuclear translocation of NF-κB, mRNA expression of inflammatory cytokines, lipid peroxidation and glutathione content, and superoxide dismutase and catalase activities were measured. GC-7101 significantly attenuated development of acute gastric ulcer and accelerated the healing of acetic-acid-induced subchronic gastric ulcer. In HCl/EtOH-induced gastric ulcer, GC-7101 markedly enhanced gastric wall mucus content which was accompanied by increased mucosal PGE₂ and NO production. Furthermore, treatment of GC-7101 exhibited anti-inflammatory and antioxidant activities as evidenced by decreased myeloperoxidase activity, NF-κB translocation, inflammatory cytokines mRNA expression, and lipid peroxidation and increased glutathione content and superoxide dismutase and catalase activities. These results demonstrated that GC-7101 possesses strong antiulcerogenic effect by modulating oxidative stress and proinflammatory mediators.

Evidence for regulated interleukin-4 expression in chondrocyte-scaffolds under in vitro inflammatory conditions

Objective

To elucidate the anti-inflammatory and anabolic effects of regulated expression of IL-4 in chondrocyte-scaffolds under in vitro inflammatory conditions.

Methods

Mature articular chondrocytes from dogs (n = 3) were conditioned through transient transfection using pcDNA3.1.cIL-4 (constitutive) or pCOX-2.cIL-4 (cytokine-responsive) plasmids. Conditioned cells were seeded in alginate microspheres and rat-tail collagen type I matrix (CaReS®) to generate two types of tissue-engineered 3-dimensional scaffolds. Inflammatory arthritis was simulated in the packed chondrocytes through exogenous addition of recombinant canine (rc) IL-1β (100 ng/ml) plus rcTNFα (50 ng/ml) in culture media for 96 hours. Harvested cells and culture media were analyzed by various assays to monitor the anti-inflammatory and regenerative (anabolic) properties of cIL-4.

Results

cIL-4 was expressed from COX-2 promoter exclusively on the addition of rcIL-1β and rcTNFα while its expression from CMV promoter was constitutive. The expressed cIL-4 downregulated the mRNA expression of IL-1β, TNFα, IL-6, iNOS and COX-2 in the cells and inhibited the production of NO and PGE₂ in culture media. At the same time, it up-regulated the expression of IGF-1, IL-1ra, COL2a1 and aggrecan in conditioned chondrocytes in both scaffolds along with a diminished release of total collagen and sGAG into the culture media. An increased amount of cIL-4 protein was detected both in chondrocyte cell lysate and in concentrated culture media. Neutralizing anti-cIL-4 antibody assay confirmed that the anti-inflammatory and regenerative effects seen are exclusively driven by cIL-4. There was a restricted expression of IL-4 under COX-2 promoter possibly due to negative feedback loop while it was over-expressed under CMV promoter (undesirable). Furthermore, the anti-inflammatory /anabolic outcomes from both scaffolds were reproducible and the therapeutic effects of cIL-4 were both scaffold- and promoter-independent.

Conclusions

Regulated expression of therapeutic candidate gene(s) coupled with suitable scaffold(s) could potentially serve as a useful tissue-engineering tool to devise future treatment strategies for osteoarthritis.

Non-FcεR bearing mast cells secrete sufficient interleukin-4 to control Francisella tularensis replication within macrophages

Mast cells have classically been implicated in the triggering of allergic and anaphylactic reactions. However, recent findings have elucidated the ability of these cells to selectively release a variety of cytokines leading to bacterial clearance through neutrophil and dendritic cell mobilization, and suggest an important role in innate host defenses. Our laboratory has established a primary bone marrow derived mast cell-macrophage co-culture system and found that mast cells mediated a significant inhibition of Francisella tularensis live vaccine strain (LVS) uptake and replication within macrophages through contact and the secreted product interleukin-4 (IL-4). In this study, we utilized P815 mast cells and J774 macrophages to further investigate whether mast cell activation by non-FcεR driven signals could produce IL-4 and control intramacrophage LVS replication. P815 supernatants collected upon activation by the mast cell activating peptide MP7, as well as P815 cells co-cultured with J774 macrophages, exhibited marked inhibition of bacterial uptake and replication, which correlated with the production of IL-4. The inhibition noted in vitro was titratable and preserved at ratios relevant to cellular infiltration events following pulmonary challenge. Collectively, our data suggest that both primary mast cell and P815 mast cell (lacking FcεR) secreted IL-4 can control intramacrophage Francisella replication.

Azadirachtin interacts with the tumor necrosis factor (TNF) binding domain of its receptors and inhibits TNF-induced biological responses

The role of azadirachtin, an active component of a medicinal plant Neem (Azadirachta indica), on TNF-induced cell signaling in human cell lines was investigated. Azadirachtin blocks TNF-induced activation of nuclear factor kappaB (NF-kappaB) and also expression of NF-kappaB-dependent genes such as adhesion molecules and cyclooxygenase 2. Azadirachtin inhibits the inhibitory subunit of NF-kappaB (IkappaB alpha) phosphorylation and thereby its degradation and RelA (p65) nuclear translocation. It blocks IkappaB alpha kinase (IKK) activity ex vivo, but not in vitro. Surprisingly, azadirachtin blocks NF-kappaB DNA binding activity in transfected cells with TNF receptor-associated factor (TRAF)2, TNF receptor-associated death domain (TRADD), IKK, or p65, but not with TNFR, suggesting its effect is at the TNFR level. Azadirachtin blocks binding of TNF, but not IL-1, IL-4, IL-8, or TNF-related apoptosis-inducing ligand (TRAIL) with its respective receptors. Anti-TNFR antibody or TNF protects azadirachtin-mediated down-regulation of TNFRs. Further, in silico data suggest that azadirachtin strongly binds in the TNF binding site of TNFR. Overall, our data suggest that azadirachtin modulates cell surface TNFRs thereby decreasing TNF-induced biological responses. Thus, azadirachtin exerts an anti-inflammatory response by a novel pathway, which may be beneficial for anti-inflammatory therapy.

Type 2 Diabetes Impairs Insulin Receptor Substrate-2-Mediated Phosphatidylinositol 3-Kinase Activity in Primary Macrophages to Induce a State of Cytokine Resistance to IL-4 in Association with Overexpression of Suppressor of Cytokine Signaling-3

Chronic elevation of proinflammatory markers in type 2 diabetes (T2D) is well defined, but the role of anti-inflammatory cytokines in T2D is less clear. In this study, we report that normal IL-4-dependent elaboration of IL-1 receptor antagonist (IL-1RA) requires IRS-2-mediated PI3K activity in primary macrophages. We also show that macrophages isolated from obese/diabetic db/db mice have impaired IRS-2-mediated PI3K activity and constitutively overexpress suppressor of cytokine signaling (SOCS)-3, which impairs an important IL-4 anti-inflammatory function. Peritoneal proinflammatory cytokine levels were examined in diabese (db/db) mice, and IL-6 was found to be nearly 7-fold higher than in nondiabese (db/+) control mice. Resident peritoneal macrophages were isolated from db/db mice and were found to constitutively overexpress IL-6 and were unable to elaborate IL-1RA in response to IL-4-like db/+ mouse macrophages. Inhibition of PI3K with wortmannin or blockage of IRS-2/PI3K complex formation with a cell permeable IRS-2-derived tyrosine phosphopeptide inhibited IL-4-dependent IL-1RA production in db/+ macrophages. Examination of IL-4 signaling in db/db macrophages revealed that IL-4-dependent IRS-2/PI3K complex formation and IRS-2 tyrosine phosphorylation was reduced compared with db/+ macrophages. SOCS-3/IL-4 receptor complexes, however, were increased in db/db mouse macrophages compared with db/+ mice macrophages as was db/db mouse macrophage SOCS-3 expression. These results indicate that in the db/db mouse model of T2D, macrophage expression of SOCS-3 is increased, and impaired IL-4-dependent IRS-2/PI3K formation induces a state of IL-4 resistance that disrupts IL-4-dependent production of IL-1RA.

The chemopreventive polyphenol Curcumin prevents hematogenous breast cancer metastases in immunodeficient mice

Dissemination of metastatic cells probably occurs long before diagnosis of the primary tumor. Metastasis during early phases of carcinogenesis in high risk patients is therefore a potential prevention target. The plant polyphenol Curcumin has been proposed for dietary prevention of cancer. We therefore examined its effects on the human breast cancer cell line MDA-MB-231 in vitroand in a mouse metastasis model. Curcumin strongly induces apoptosis in MDA-MB-231 cells in correlation with reduced activation of the survival pathway NFkappaB, as a consequence of diminished IotakappaB and p65 phosphorylation. Curcumin also reduces the expression of major matrix metalloproteinases (MMPs) due to reduced NFkappa B activity and transcriptional downregulation of AP-1. NFkappa B/p65 silencing is sufficient to downregulate c-jun and MMP expression. Reduced NFkappa B/AP-1 activity and MMP expression lead to diminished invasion through a reconstituted basement membrane and to a significantly lower number of lung metastases in immunodeficient mice after intercardiac injection of 231 cells (p=0.0035). 68% of Curcumin treated but only 17% of untreated animals showed no or very few lung metastases, most likely as a consequence of down-regulation of NFkappa B/AP-1 dependent MMP expression and direct apoptotic effects on circulating tumor cells but not on established metastases. Dietary chemoprevention of metastases appears therefore feasible.

Mutant human tumor suppressor p53 modulates the activation of mitogen-activated protein kinase and nuclear factor-kappaB, but not c-Jun N-terminal kinase and activated protein-1

The roles of the mitogen-activated kinase protein (MAPK) pathway, nuclear factor-kappa B (NF-kappaB), and activator protein-1 (AP-1) in cellular responses to growth factors and mitogen are well established. However, the manner by which these proliferative pathways are affected by the tumor suppressor protein p53 is not fully understood. We report here the results of an investigation of the status of p53 on two human melanoma cell lines with wild-type p53 (SK-Mel-186) or mutant p53 (SK-Mel-110). The basal levels of the activated extracellular-signal regulated kinases 1 and 2 (ERK1/2) were high in cells with wild-type p53, but low in cells with mutant p53. The 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced activation of ERK1/2 through the phosphorylation of threonine and tyrosine at 202 and 204, respectively, was demonstrated in both cell lines, however, in a discrete manner. TPA-induced activation of ERK1/2 was sustained in wild-type p53 cells, while only a transient activation was seen in mutant p53 cells. Inhibition of MAPK kinase (MEK), an upstream kinase, by U0126, blocked TPA-induced activation of ERK1/2 in wild-type p53 cells and in mutant p53 cells. Treatment of wild-type p53 (SK-Mel 186) cells with small interfering RNA (siRNA) of p53 displayed a transient induction of activation of ERK1/2 following TPA treatment, indicating that p53 has a role in the regulation of the activation of ERK1/2. NF-kappaB activity decreased significantly in cells with wild-type p53, while enhanced NF-kappaB activity was evident in cells with mutant p53. The expression of either wild-type or mutant p53 had a similar effect on TPA-induced Jun N-terminal kinase (JNK) activation, indicating specificity for the ERK pathway. Similarly, AP-1 binding activity showed a transient variation in both cell lines after TPA treatment but with different kinetics. These observations suggest that both wild-type and mutant p53 can modulate the activation pathways for ERK1/2, and NF-kappaB distinctively, while modulating the pathways of JNK and AP-1 similarly. These differences may influence cellular processes such as proliferation, differentiation, and apoptosis.

α-melanocyte-stimulating hormone down-regulates CXC receptors through activation of neutrophil elastase

Considering the role of interleukin-8 (IL-8) in a large number of acute and chronic inflammatory diseases, the regulation of IL-8-mediated biological responses is important. Alpha-melanocyte-stimulating hormone (alpha-MSH), a tridecapeptide, inhibits most forms of inflammation by an unknown mechanism. In the present study, we have found that alpha-MSH interacts predominantly with melanocortin-1 receptors and inhibits several IL-8-induced biological responses in macrophages and neutrophils. It down-regulated receptors for IL-8 but not for TNF, IL-4, IL-13 or TNF-related apoptosis-inducing ligand (TRAIL) in neutrophils. It down-regulated CXCR type 1 and 2 but not mRNA levels. alpha-MSH did not inhibit IL-8 binding in purified cell membrane or affinity-purified CXCR. IL-8 or anti-CXCR Ab protected against alpha-MSH-mediated inhibition of IL-8 binding. The level of neutrophil elastase, a specific serine protease, but not cathepsin G or proteinase 3 increased in alpha-MSH-treated cells, and restoration of CXCR by specific neutrophil elastase or serine protease inhibitors indicates the involvement of elastase in alpha-MSH-induced down-regulation of CXCR. These studies suggest that alpha-MSH inhibits IL-8-mediated biological responses by down-regulating CXCR through induction of serine protease and that alpha-MSH acts as a potent immunomodulator in neutrophil-driven inflammatory distress.

Cardiac glycoside inhibits IL-8-induced biological responses by downregulating IL-8 receptors through altering membrane fluidity

Considering the potential role of interleukin-8 (IL-8) in inflammation, angiogenesis, tumorogenesis, and metastasis, and the involvement of different cell types especially neutrophils and macrophages in those processes, the regulation of IL-8-mediated biological responses is important. In this report we provide evidences that oleandrin, a cardiac glycoside potentially inhibited IL-8-, formyl peptide (FMLP)-, EGF-, or nerve growth factor (NGF)-, but not IL-1- or TNF-induced NF-kappaB activation in macrophages. Oleandrin inhibited IL-8-, but not TNF-induced NF-kappaB-dependent genes expression. Oleandrin inhibited the binding of IL-8, EGF, or NGF, but not IL-1 or TNF. It decreased almost 79% IL-8 binding without altering affinity towards IL-8 receptors and this inhibition of IL-8 binding was observed in isolated membrane. The IL-8, anti-IL-8Rs antibodies, or protease inhibitors were unable to protect oleandrin-mediated inhibition of IL-8 binding. Phospholipids significantly protected oleandrin-mediated inhibition of IL-8 binding thereby restoring IL-8-induced NF-kappaB activation. Oleandrin altered the membrane fluidity as detected by microviscosity parameter and a decrease in diphenylhexatriene, a lipid binding fluorophore binding in a dose-dependent manner. Overall, our results suggest that oleandrin inhibits IL-8-mediated biological responses in diverse cell types by modulating IL-8Rs through altering membrane fluidity and microviscosity. The study might help to regulate IL-8-mediated biological responses involved in inflammation, metastasis, and neovascularization.

Anti-inflammatory Effect of Pitavastatin on NF-.KAPPA.B Activated by TNF-.ALPHA. in Hepatocellular Carcinoma Cells

As nuclear factor-kappa B (NF-kappaB) is essential for promoting inflammation-associated cancer, it is a potential target for cancer prevention in chronic inflammatory diseases. Here we examined the anti-inflammatory effect of pitavastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on NF-kappaB activated by TNF-alpha in hepatocellular carcinoma (HCC) cells. Western blot revealed that the treatment of Huh 7 cells with pitavastatin at 0.1 microM inhibited the nuclear expression of NF-kappaB p65 induced by TNF-alpha. Furthermore, electrophoretic mobility shift assay showed that after the cells were incubated with pitavastatin alone or with pitavastatin and TNF-alpha for 24 h, pitavastatin significantly decreased the DNA binding activity of NF-kappaB induced by TNF-alpha. Subsequently, luciferase assay revealed that pitavastatin suppressed the transcriptional activity of the NF-kappaB promoter, which was clearly related to the HMG-CoA reductase activity because the addition of mevalonic acid (MEV) elevated the TNF-alpha activity. Moreover, the Rho kinase inhibitor Y27632 had no major effect on the NF-kappaB inhibitory activity of pitavastatin. The inhibitory effect of pitavastatin is possibly independent of the Rho kinase pathway in inflammation-associated HCC cells is. Finally, the addition of TNF-alpha significantly increased IL-6 protein production, which was suppressed by the addition of pitavastatin. These results suggest that pitavastatin at a low dose (0.1 microM) inhibits NF-kappaB activation and decreases IL-6 production induced by TNF-alpha, and is therefore expected to be a new strategy for treating HCC.

Interleukin-4 downregulates TNFalpha-induced IL-8 production in keratinocytes

Interleukin (IL)-8 is a CXC chemokine induced by pro-inflammatory cytokines such as TNFalpha, IL-1beta and IL-6 in different cell types including keratinocytes. IL-4 regulation of TNFalpha-induced IL-8 expression is cell-type specific. In this study, we show that in the keratinocyte cell line HaCaT, IL-4 decreases TNFalpha-induced IL-8 mRNA expression. We then investigated the mechanism of IL-4 effect and showed that IL-4 downregulates TNFalpha-induced IL-8 promoter activity in luciferase reporter assays. Moreover, overexpression of either the endogenous JAK inhibitor SOCS-1 or a dominant negative form of the STAT6 transcription factor (STAT6DeltaC) interferes with the IL-4 inhibitory effect on IL-8 promoter. Finally we demonstrate, using a NF-kappaB-dependent promoter luciferase construct that IL-4 interferes, at least in part, with NF-kappaB transcriptional activity. Overall our results suggest that IL-4 regulates TNFalpha-induced IL-8 expression at a transcriptional level and this mechanism involves STAT6 and NF-kappaB transcription factors.

Neural cell adhesion molecule function is regulated by metalloproteinase-mediated ectodomain release

The neural cell adhesion molecule (NCAM) is involved in development of the nervous system, in brain plasticity associated with learning and memory, and in neuronal regeneration. NCAM regulates these processes by influencing cell adhesion, cell migration, and neurite outgrowth. NCAM activates intracellular signaling upon homophilic NCAM binding, and this is a prerequisite for NCAM-stimulated neurite outgrowth. NCAM is synthesized in three main membrane-bound isoforms, NCAM-120, NCAM-140, and NCAM-180. Soluble forms of NCAM in blood and cerebrospinal fluid have also been found, although the functional significance of these forms remains unclear. In this report, we demonstrate that NCAM can be released from primary hippocampal neurons in culture. The release was enhanced by application of ATP and inhibited by the metalloproteinase inhibitor BB-3103. ATP also induced metalloproteinase-dependent release of all three major NCAM isoforms from NCAM-transfected fibroblastoid L-cells. In this model system, the extracellular ATP-binding site of NCAM was shown not to be necessary for ATP-induced NCAM release. Furthermore, inhibition of serine, cysteine, and aspartic proteinases could not prevent ATP-induced down-regulation of NCAM in L-cells, suggesting that NCAM is cleaved directly by a metalloproteinase. Aggregation of hippocampal neurons in culture was increased in the presence of the metalloproteinase inhibitor GM 6001, consistent with a metalloproteinase-dependent shedding of NCAM occurring in these cells. Moreover, NCAM-dependent neurite outgrowth was significantly reduced by application of GM 6001. Taken together, these results suggest that membrane-bound NCAM can be cleaved extracellularly by a metalloproteinase and that metalloproteinase-dependent shedding of NCAM regulates NCAM-mediated neurite outgrowth.

IL-4 Inhibits Bone-Resorbing Activity of Mature Osteoclasts by Affecting NF-κB and Ca2+ Signaling

IL-4 is an important immune cytokine that regulates bone homeostasis. We investigated the molecular mechanism of IL-4 action on bone-resorbing mature osteoclasts. Using a highly purified population of mature osteoclasts, we show that IL-4 dose-dependently inhibits receptor activator of NF-kappaB ligand (RANKL)-induced bone resorption by mature osteoclasts. We detected the existence of IL-4R mRNA in mature osteoclasts. IL-4 decreases TRAP expression without affecting multinuclearity of osteoclasts, and inhibits actin ring formation and migration of osteoclasts. Interestingly, IL-4 inhibition of bone resorption occurs through prevention of RANKL-induced nuclear translocation of p65 NF-kappaB subunit, and intracellular Ca(2+) changes. Moreover, IL-4 rapidly decreases RANKL-stimulated ionized Ca(2+) levels in the blood, and mature osteoclasts in IL-4 knockout mice are sensitive to RANKL action to induce bone resorption and hypercalcemia. Furthermore, IL-4 inhibits bone resorption and actin ring formation by human mature osteoclasts. Thus, we reveal that IL-4 acts directly on mature osteoclasts and inhibits bone resorption by inhibiting NF-kappaB and Ca(2+) signaling.

Differential effect of interleukin-10 on hepatocyte apoptosis

Current data suggests that hepatocyte apoptosis is an essential feature contributing to several chronic liver diseases. It has been shown that IL-10 has diverse and potentially pleiotropic actions that suggest that it may have a direct effect on apoptosis. It has been established that NF-kappaB activation is essential to protect hepatocytes from apoptosis. The purpose of the present work is to evaluate the effect of the anti-inflammatory cytokine, IL-10 on the activation of NF-kappaB in primary cultured rat hepatocytes and hepatoblastoma (HepG2) cell line and explore its consequences on apoptosis. Apoptosis was induced by TNF-alpha and cicloheximide in HepG2 hepatoblastoma cells and by ethanol and a glutathione depletor in primary cultured rat hepatocytes. NF-kappaB activation was determined by EMSA. IL-10 increased ethanol induced apoptosis in primary culture rat hepatocytes (28%). These effects were enhanced when the cells were pre-treated with IL-10 under conditions of oxidative stress (glutathione depletion). The effects of IL-10 on primary cultured hepatocytes were independent of NF-kappaB activation. When apoptosis was induced by cicloheximide and TNF-alpha in hepatoblastoma cells, pretreatment with IL-10 was accompanied by a decrease of 38% in apoptosis. IL-10 did not have any effect on the signaling cascade of apoptosis but caused a significant increase in NF-kappaB activation. When NF-kappaB activation was inhibited by sulfazalazine the decrease in apoptosis was reversed. The present study demonstrates the importance of differential cell marking when trying to characterize the effects of cytokines in their contribution to liver cell apoptosis. The study provides insight into the mechanisms by which IL-10 affects apoptosis through a differential effect on NF-kappaB activation.

Activation of c-Jun-N-terminal kinase is critical in mediating lipopolysaccharide-induced changes in the rat hippocampus

Lipopolysaccharide (LPS) exerts a myriad of effects in rat hippocampus; it increases the concentration of the proinflammatory cytokine, interleukin-1beta (IL-1beta), and signalling via the IL-1 type I receptor (IL-1RI) resulting in phosphorylation of the stress-activated protein kinase, c-jun-N-terminal kinase (JNK) and impairment in long-term potentiation (LTP). This study was designed to establish whether activation of JNK is a pivotal event in mediating the effects of LPS in hippocampus and therefore LPS-treated rats were injected intracerebroventricularly with saline, the JNK inhibitor D-JNKI1, or with the anti-inflammatory cytokine IL-4, which antagonizes the effects of IL-1beta upstream of JNK activation. We report that IL-4 blocked the LPS-induced increase in IL-1RI expression and associated increases in phosphorylation of JNK and c-jun, whereas D-JNKI1 inhibited the LPS-induced phosphorylation of c-jun. Both IL-4 and D-JNKI1 inhibited the increase in caspase-3 staining which was associated with LPS treatment, and both abrogated the LPS-induced inhibition of LTP in perforant path-granule cell synapses. The data presented are consistent with the proposal that JNK activation, probably as a result of increased IL-1RI activation, is a critical step in mediating the detrimental effects of LPS in hippocampus.

Differential modulation of interleukin 8 by interleukin 4 and interleukin 10 in HepG2 cells treated with acetaldehyde

BACKGROUND/AIM

Pro-inflammatory cytokines and chemokines, such as interleukin (IL) 8, are important mediators of hepatic injury and repair following an insult. The purpose of this work was to study the regulation of IL-8 by IL-10 and IL-4 in HepG2 cells treated with acetaldehyde (Ac).

METHODS

HepG2 cells were pretreated with IL-10 or IL-4 before exposure to Ac, examining IL-8 expression by reverse transcription polymerase chain reaction and Western blot.

RESULTS

Ac treatment produced an increment in IL-8 induction and secretion that was prevented by IL-4 pretreatment, while IL-10 pretreatment failed to decrease Ac-induced IL-8 production. Consistent with these findings Ac increased NF-kappa B and AP-1 activation that were prevented by IL-4 but not by IL-10, findings accompanied by greater I kappa B-alpha levels in IL-4 but not IL-10 pretreated cells. In contrast to the pro-inflammatory role of IL-10 in HepG2, IL-10 did not show any change in the activation of NF-kappa B by Ac in WRL-68 cells, a human fetal hepatic cell line. Moreover, IL-10 did not induce the degradation of I kappa B-alpha in cellular extract from rat primary cultured cells.

CONCLUSIONS

While the present findings demonstrate the anti-inflammatory role of IL-4 in preventing the expression of IL-8 by Ac, the regulation of chemokines by anti-inflammatory cytokines is complex and depends on the cellular lineage.

Role of tumor necrosis factor-alpha in the development of spontaneous hepatic toxicity in Long-Evans Cinnamon rats

The objective of this study was to evaluate the potential role of TNF-alpha in the onset of acute hepatitis in the Long-Evans Cinnamon (LEC) rat, an animal model for inherited copper (Cu) toxicosis. In LEC rats, Cu is accumulated in the liver with age, and clinical signs of acute hepatitis were observed as, icterus, reduced body weight, nasal bleeding, dehydration, and reduced food intake at 12 weeks of age. Cellular changes such as apoptosis in the liver were evident in these rats with increasing age. Positive TNF-alpha and TNFR1 immunostainings were observed in hepatocytes and Kupffer cells in LEC rats. Hepatic levels of caspase-3 activity, TNF-alpha mRNA, and protein were also increased in LEC rats from 6 to 12 weeks of age as compared with control Long-Evans (LE) rats. The neutralization of TNF-alpha by passive immunization or the inhibition of caspase activity can block the apoptotic process initiated by TNF-alpha. In this study, we evaluated the effects of passive immunization of LEC rats with weekly administration of anti-rat TNF-alpha on Cu-induced acute hepatitis. This treatment resulted in a reduction of the percentage of apoptotic cells in the liver, decreased activity of caspase-3, and also in down-regulation of the TNF-alpha gene expression. Thus, these results suggest a major role for TNF-alpha on the pathogenesis of Cu-induced acute hepatitis in LEC rats.

Curcumin (diferuloylmethane) inhibits receptor activator of NF-kappa B ligand-induced NF-kappa B activation in osteoclast precursors and suppresses osteoclastogenesis

Numerous studies have indicated that inflammatory cytokines play a major role in osteoclastogenesis, leading to the bone resorption that is frequently associated with cancers and other diseases. Gene deletion studies have shown that receptor activator of NF-kappaB ligand (RANKL) is one of the critical mediators of osteoclastogenesis. How RANKL mediates osteoclastogenesis is not fully understood, but an agent that suppresses RANKL signaling has potential to inhibit osteoclastogenesis. In this report, we examine the ability of curcumin (diferuloylmethane), a pigment derived from turmeric, to suppress RANKL signaling and osteoclastogenesis in RAW 264.7 cells, a murine monocytic cell line. Treatment of these cells with RANKL activated NF-kappaB, and preexposure of the cells to curcumin completely suppressed RANKL-induced NF-kappaB activation. Curcumin inhibited the pathway leading from activation of IkappaBalpha kinase and IkappaBalpha phosphorylation to IkappaBalpha degradation. RANKL induced osteoclastogenesis in these monocytic cells, and curcumin inhibited both RANKL- and TNF-induced osteoclastogenesis and pit formation. Curcumin suppressed osteoclastogenesis maximally when added together with RANKL and minimally when it was added 2 days after RANKL. Whether curcumin inhibits RANKL-induced osteoclastogenesis through suppression of NF-kappaB was also confirmed independently, as RANKL failed to activate NF-kappaB in cells stably transfected with a dominant-negative form of IkappaBalpha and concurrently failed to induce osteoclastogenesis. Thus overall these results indicate that RANKL induces osteoclastogenesis through the activation of NF-kappaB, and treatment with curcumin inhibits both the NF-kappaB activation and osteoclastogenesis induced by RANKL.

Determination of binding constant of transcription factor myc-max/max-max and E-box DNA: the effect of inhibitors on the binding

The truncated myc and max proteins, only containing basic regions and helix-loop-helix/zipper (b/HLH/Zip) regions were over-expressed in E. coli and used for the determination of the binding constant and of the inhibitory mechanism on myc-max (or max-max)-DNA complex formation. The association kinetic constants (k(1) and k(-1)) of truncated max-max or myc-max dimer and DNA were determined as k(1)=(1.7+/-0.6)x10(5) M(-1) s(-1), k(-1)=(3.4+/-1.2)x10(-2) s(-1) for max-max and DNA or k(1)=(2.1+/-0.7)x10(5) M(-1) s(-1), k(-1)=(3.2+/-1.4)x10(-2) s(-1) for myc-max and DNA. The equilibrium binding constant (K(1)) was determined using these kinetic parameters [K(XXD)=(7.8+/-2.6)x10(6) M(-1) for max-max and DNA or K(XYD)=(6.9+/-2.2)x10(6) M(-1) for myc-max and DNA]. The binding constants of myc-max or max-max dimer formation were K(XX)=(2.6+/-0.9)x10(5) M(-1) or K(XY)=(1.3+/-0.4)x10(4) M(-1), respectively. When truncated proteins were used, the max-max dimer formation was easier than the myc-max dimer formation, contrary to the physiologically determined case. This leads us to deduce that domains other than b/HLH/Zip are very important for the transcriptional regulatory activity in physiological conditions. The truncated myc and max proteins, which were expressed in E. coli and contained only b/HLH/Zip regions were also used for the screening of inhibitors of myc-max-DNA complex formation. A synthesized curcuminoid, 1,7-bis(4-methyl-3-nitrophenyl)-1,6-heptadiene-3,5-dione (curcuminoid 004), showed the most potent inhibition out of the synthesized curcuminoids, in competition with DNA. The dissociation constant of max-max dimer and the inhibitor was 9 microM, when investigated using in vitro expressed b/HLH/Zip dimer proteins. The curcuminoid 004 showed an inhibitory effect on the binding of myc-max protein to the E-box element in SNU16 cells, and suppressed the expression of myc target genes including ornithine decarboxylase (ODC), cdc25a and c-myc in myc over-expressed human stomach cancer cell line SNU16.

Reprogramming of human postmitotic neutrophils into macrophages by growth factors

It is generally recognized that postmitotic neutrophils give rise to polymorphonuclear neutrophils alone. We obtained evidence for a lineage switch of human postmitotic neutrophils into macrophages in culture. When the CD15+CD14- cell population, which predominantly consists of band neutrophils, was cultured with granulocyte macrophage-colony-stimulating factor, tumor necrosis factor-alpha, interferon-gamma, and interleukin-4, and subsequently with macrophage colony-stimulating factor alone, the resultant cells had morphologic, cytochemical, and phenotypic features of macrophages. In contrast to the starting population, they were negative for myeloperoxidase, specific esterase, and lactoferrin, and they up-regulated nonspecific esterase activity and the expression of macrophage colony-stimulating factor receptor, mannose receptor, and HLA-DR. CD15+CD14- cells proceeded to macrophages through the CD15-CD14- cell population. Microarray analysis of gene expression also disclosed the lineage conversion from neutrophils to macrophages. Macrophages derived from CD15+CD14- neutrophils had phagocytic function. Data obtained using 3 different techniques, including Ki-67 staining, bromodeoxyuridine incorporation, and cytoplasmic dye labeling, together with the yield of cells, indicated that the generation of macrophages from CD15+CD14- neutrophils did not result from a contamination of progenitors for macrophages. Our data show that in response to cytokines, postmitotic neutrophils can become macrophages. This may represent another differentiation pathway toward macrophages in human postnatal hematopoiesis.

Overexpression of MEKK3 confers resistance to apoptosis through activation of NFkappaB

Many cancers have constitutively activated NFkappaB, the elevation of which contributes to cancer cell resistance to chemotherapeutic agent-induced apoptosis. Although mitogen-activated protein kinase/extracellular-regulated kinase kinase kinase-3 (MEKK3) has been shown to participate in the activation of NFkappaB, its relations to apoptosis and cancer are unclear. In this study, we established cell model systems to examine whether stable expression of MEKK3 could lead to increased NFkappaB activity and confer resistance to apoptosis. In addition, we investigated in breast and ovarian cancers whether MEKK3 expression may be altered and correlated with aberrant NFkappaB activity. We show that stable cell lines overexpressing MEKK3 not only had elevated levels of NFkappaB binding activity but also were more responsive to cytokine stimulation. These stable cells showed 2-4-fold higher basal expression of Bcl-2 and xIAP than the parental cells. Consistent with this increased expression of cell survival genes, MEKK3 stable cells showed reduced activation of caspases 3 and 8 and poly(ADP-ribose) polymerase cleavage and dramatically increased resistance to apoptosis induced by tumor necrosis factor-related apoptosis-inducing ligand, doxorubicin, daunorubicin, camptothecin, and paclitaxel. Intriguingly, analysis of human breast and ovarian cancers showed that a significant fraction of these samples have elevated MEKK3 protein levels with corresponding increases in NFkappaB binding activities. Thus, our results established that elevated expression of MEKK3 appears to be a frequent occurrence in breast and ovarian cancers and that overexpression of MEKK3 in cells leads to increased NFkappaB activity and increased expression of cell survival factors and ultimately contributes to their resistance to apoptosis. As such, MEKK3 may serve as a therapeutic target to control cancer cell resistance to cytokine- or drug-induced apoptosis.

alpha-Melanocyte-stimulating hormone induces cell death in mast cells: involvement of NF-kappaB

Mast cells play a major role in the initiation of inflammation and allergic reactions. As cell numbers are tightly controlled by the interplay of factors affecting cell proliferation, development, and death the regulation of mast cell number may be important. Melanocyte-stimulating hormone inhibits most forms of inflammation by an unknown mechanism. In the present study, we have found that the alpha-melanocyte-stimulating hormone (alpha-MSH) inhibited endotoxin-mediated nuclear transcription factor kappaB (NF-kappaB) activation in different cells correlated with the expression of alpha-MSH receptors. We have also found for the first time that it induces cell death alone or in endotoxin-stimulated mast cells. alpha-MSH-mediated apoptosis was not observed in NF-kappaB overexpressed cells. The inhibitory effect of alpha-MSH was mediated through generation of cAMP, as inhibitors of adenylate cyclase and of protein kinase A reversed its inhibitory effect. Overall, our results suggest that NF-kappaB is the key molecule involved in alpha-MSH-mediated cell death and this may help to regulate mast cell-mediated inflammation.

Autolytic processing at Glu586-Ser587 within the cysteine-rich domain of human adamalysin 19/disintegrin-metalloproteinase 19 is necessary for its proteolytic activity

We investigated the regulation of the proteolytic activity of human adamalysin 19 (a disintegrin and metalloproteinase 19, hADAM19). It was processed at Glu(586)(P1)-Ser(587)(P1') site in the cysteine-rich domain as shown by protein N-terminal sequencing. This truncation was autolytic as illustrated by its R199A/R200A or E346A mutation that prevented the zymogen activation by furin or abolished the catalytic activity. Reagents that block furin-mediated activation of pro-hADAM19, decRVKR-CMK, and brefeldin A abrogated this processing. The sizes of the side chains of the P1 and P1' residues are critical for the processing of hADAM19. The amount of processing product in the E586Q or S587A mutant with a side chain almost the same size as that in the wild type was almost equal. Conversely, very little processing was observed when the size of the side chain was changed significantly, such as in the E586A, E586G, or S587F mutants. Two mutants with presumably subtle structural distinctions from wild type hADAM19, E586D and S587T, displayed rare or little processing and had very low capacities to cleave alpha2-macroglobulin and a peptide substrate. Therefore, this processing is necessary for hADAM19 to exert its proteolytic activities. Moreover, a new peptide substrate, Ac-RPLE-SNAV, which is identical to the processing site sequence, was cleaved at the E-S bond by soluble hADAM19 containing the catalytic and disintegrin domains. This enzyme cleaved the substrate with K(m), k(cat), and k(cat)/K(m) of 2.0 mm, 2.4/min, and 1200 m(-1) min(-1), respectively, using a fluorescamine assay. Preliminary studies showed that a protein kinase C activator, phorbol 12-myristate 13-acetate, promoted the cellular processing of hADAM19; however, three calmodulin antagonists, trifluoperazine, W7, and calmidazolium, impaired this cleavage, indicating complex signal pathways may be involved in the processing.

TNF receptor subtype signalling: differences and cellular consequences

Tumour necrosis factor-alpha (TNF alpha) is a multifunctional cytokine belonging to a family of ligands with an associated family of receptor proteins. The pleiotropic actions of TNF range from proliferative responses such as cell growth and differentiation, to inflammatory effects and the mediation of immune responses, to destructive cellular outcomes such as apoptotic and necrotic cell death mechanisms. Activated TNF receptors mediate the association of distinct adaptor proteins that regulate a variety of signalling processes including kinase or phosphatase activation, lipase stimulation, and protease induction. Moreover, the cytokine regulates the activities of transcription factors, heterotrimeric or monomeric G-proteins and calcium ion homeostasis in order to orchestrate its cellular functions. This review addresses the structural basis of TNF signalling, the pathways employed with their cellular consequences, and focuses on the specific role played by each of the two TNF receptor isotypes, TNFR1 and TNFR2.

Nuclear transcription factor-kappaB as a target for cancer drug development

Nuclear factor kappa B (NF-kappaB) is a family of inducible transcription factors found virtually ubiquitously in all cells. Since its discovery by Sen and Baltimore in 1986, much has been discovered about its mechanisms of activation, its target genes, and its function in a variety of human diseases including those related to inflammation, asthma, atherosclerosis, AIDS, septic shock, arthritis, and cancer. Due to its role in a wide variety of diseases, NF-kappaB has become one of the major targets for drug development. Here, we review our current knowledge of NF-kappaB, the possible mechanisms of its activation, its potential role in cancer, and various strategies being employed to target the NF-kappaB signaling pathway for cancer drug development.

Interleukin-4 reversibly inhibits osteoclastogenesis via inhibition of NF-kappa B and mitogen-activated protein kinase signaling

To define the molecular mechanism(s) by which interleukin (IL)-4 reversibly inhibits formation of osteoclasts (OCs) from bone marrow macrophages (BMMs), we examined the capacity of this T cell-derived cytokine to impact signals known to modulate osteoclastogenesis, which include those initiated by macrophage colony-stimulating factor (M-CSF), receptor for activation of NF-kappa B ligand (RANKL), tumor necrosis factor (TNF), and IL-1. We find that although pretreatment of BMMs with IL-4 does not alter M-CSF signaling, it reversibly blocks RANKL-dependent activation of the NF-kappa B, JNK, p38, and ERK signals. IL-4 also selectively inhibits TNF signaling, while enhancing that of IL-1. Contrary to previous reports, we find that MEK inhibitors dose-dependently inhibit OC differentiation. To identify more proximal signals mediating inhibition of OC formation by IL-4, we used mice lacking STAT6 or SHIP1, two adapter proteins that bind the IL-4 receptor. IL-4 fails to inhibit RANKL/M-CSF-induced osteoclastogenesis by BMMs derived from STAT6-, but not SHIP1-, knockout mice. Consistent with this observation, the inhibitory effects of IL-4 on RANKL-induced NF-kappa B and mitogen-activated protein kinase activation are STAT6-dependent. We conclude that IL-4 reversibly arrests osteoclastogenesis in a STAT6-dependent manner by 1) preventing I kappa B phosphorylation and thus NF-kappa B activation, and 2) blockade of the JNK, p38, and ERK mitogen-activated protein kinase pathways.

Proapoptotic and antiapoptotic markers in cutaneous T-cell lymphoma skin infiltrates and lymphomatoid papulosis

BACKGROUND

In cutaneous T-cell lymphoma (CTCL) lesions, both reactive T cells and malignant T cells intermingle. The disease progression is mostly slow. Recent evidence suggests that even if clinical remission is reached, malignant cells persist and a relapse follows sooner or later. To wha extent tumour cell apoptosis occurs in the skin lesions either due to the reactive T cells or t therapeutic efforts is not known.

OBJECTIVES

To determine the extent of tumour cell apoptosis and the expression of proapoptotic an antiapoptotic markers in serial skin lesion samples from patients with CTCL, and to compare th findings with those in patients with lymphomatoid papulosis (LyP).

METHODS

Thirty-four skin samples were obtained from 12 patients with CTCL at the time o diagnosis and at a mean of 1.6, 3 and 6 years later. The patients received psoralen plus ultraviolet (PUVA), electron beam or cytostatic treatments. In addition, fresh post-treatment samples fro three patients with CTCL undergoing PUVA therapy were obtained. For comparison, skin biopsies o five patients with LyP were studied. Immunohistochemical demonstration of the expression of th following markers was performed on formalin-fixed skin sections: Fas (CD95), Fas ligand (FasL) bcl-2, granzyme B, the tumour-suppressor protein PTEN and the effector caspase, caspase-3. Th malignant cells were identified morphologically, and apoptotic cells were identified with th terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling method on parallel sections.

RESULTS

In untreated CTCL lesions, apoptotic lymphocytes were extremely rare, and no increase in the number of apoptotic cells was observed after any of the treatments used. In LyP, apoptotic cell were more frequent, comprising on average 5% of the infiltrate. The apoptosis-associated marker Fas, FasL, caspase-3 and granzyme B were expressed by morphologically neoplastic cells in CTCL and by large atypical cells in LyP, with no significant differences. However, only a few reactive cell in CTCL infiltrates expressed granzyme B while about 10% of the corresponding cells were positive in LyP. The expression of antiapoptotic bcl-2 was more frequent in CTCL than in LyP, while PTE expression was high in both instances. The number of bcl-2 + cells tended to decrease after therapy When comparing the findings between the first and the last samples, a decrease in the number of bcl-2+ cells and an increase in Fas+ cells was associated with disease progression, despite therapy, while the opposite was true for remissions.

CONCLUSIONS

Apoptosis was found to be a rare event in CTCL lesions irrespective of precedin therapy During patient follow-up, no significant differences in the expression of apoptotic marker was observed while in most cases a lower level of antiapoptotic bcl-2 expression was observed after all types of therapies and in association with disease progression when compared with high expression in the untreated lesions. The absence of apoptosis and high expression of bcl-2 together with a low expression of apoptosis-inducing granzyme B in the reactive lymphocytes in CTC could explain the chronic nature of the disease and the poor response to therapy, while th more frequent occurrence of granzyme B and apoptosis together with a lower level of expressio of bcl-2 by the large atypical cells in LyP could contribute to the favourable outcome of the latter.

IL-4 abrogates osteoclastogenesis through STAT6-dependent inhibition of NF-kappaB

IL-4, an anti-inflammatory cytokine, inhibits osteoclast differentiation, but the basis of this effect has been unclear. Osteoclastogenesis requires activation of RANK, which exerts its biologic effect via activation of NF-kappaB. NF-kappaB activation is manifested by nuclear translocation and binding to DNA, events secondary to phosphorylation and dissociation of IkappaBalpha. It is shown here that IL-4 reduces NF-kappaB nuclear translocation by inhibiting IkappaB phosphorylation, thus markedly inhibiting NF-kappaB DNA binding activity and blocking osteoclastogenesis entirely. Residual translocation of NF-kappaB in the presence of IL-4, however, suggests that nuclear mechanisms must primarily account for inhibition of NF-kappaB DNA binding and blockade of osteoclastogenesis. To address this issue, this study examined whether IL-4-induced STAT6 transcription factor blocks NF-kappaB transactivation. The results show that excess unlabeled consensus sequence STAT6, but not its mutated form, inhibits NF-kappaB binding. Furthermore, exogenously added STAT6 protein inhibits NF-kappaB/DNA interaction. Further supporting a role for STAT6 in this process are the findings that IL-4 fails to block osteoclastogenesis in STAT6(-/-) mice but that this blockade can be restored with addition of exogenous STAT6. Thus, IL-4 obliterates osteoclast differentiation by antagonizing NF-kappaB activation in a STAT6-dependent manner.

Chromosomally clonal T cells in the skin, blood, or lymph nodes of two Sezary syndrome patients express CD45RA, CD45RO, CDw150, and interleukin-4, but no interleukin-2 or interferon-gamma

Cutaneous T cell lymphomas are considered to represent a clonal malignancy of mature T lymphocytes of the T helper memory subtype. A method enabling the direct identification of clonal malignant cells in tissue and, at the same time, identification of the surface molecules they express has not been available, however. We have developed an application of the FICTION technique (simultaneous fluorescence immunophenotyping and interphase cytogenetics) to be used on fresh blood, skin, and lymph node samples. A prerequisite for this method is the characterization of a moleculocytogenetic clone in order to select the proper probes. With this method, we demonstrate that the true malignant cells express CD3, CD4, and CD45RO in the blood, skin, and lymph nodes of two Sezary syndrome patients. The majority of these cells express also CD45RA (albeit of varying intensity) and CDw150. The cytokine expression pattern of the clonal cells in skin and lymph nodes was interleukin-2 and interferon-gamma negative and interleukin-4 positive. Interleukin-10 expression varied. The malignant cells did not express granzyme B, thus indicating that they do not have cytotoxic properties. Clonal cells with the same constant phenotype could be found even in lymph nodes with not yet morphologically identifiable malignant cells. This is the first report of the FICTION method applied directly on skin tissue. With this method we demonstrated that the chromosomally clonal cells in these two cases of Sezary syndrome could be intermediate forms between naïve CD45RA+ and CD45RO+ Th2 cells.

Interleukin-4/STAT6 represses STAT1 and NF-kappa B-dependent transcription through distinct mechanisms

STAT6 mediates interleukin-4 (IL-4)-dependent positive and negative regulation of inflammatory gene expression. In the present report we examined the molecular mechanisms involved in IL-4-induced repression of reporter gene transcription driven by STAT1 and/or NF-kappaB. Transient expression of STAT6 in a STAT6-deficient cell line (HEK 293) conferred sensitivity to IL-4 for STAT6-dependent transcription and for repression of interferon-gamma (IFNgamma)/STAT1- and/or tumor necrosis factor-alpha (TNFalpha)/NF-kappaB-driven reporter gene expression. In cells transfected with a deletion mutant of STAT6 lacking its transactivating domain, IL-4 could not mediate either positive or negative control of reporter gene expression. Overexpression of CREB-binding protein dramatically enhanced IL-4/STAT6-stimulated transcription and overcame IL-4-mediated repression of TNFalpha/NF-kappaB-dependent but not IFNgamma/STAT1-dependent transcription. A single amino acid change in the DNA-binding domain of STAT6 (H415A) selectively reduced the affinity of STAT6 for IL-4-responsive STAT sequence motifs (N4) without affecting the affinity for IFNgamma-responsive (GAS) sequences (N3) and, accordingly, eliminated transcription from an IL-4-responsive promoter. Interestingly, this mutation eliminated IL-4-mediated suppression of reporter gene transcription stimulated by TNFalpha/NF-kappaB but retained nearly full capacity to suppress IFNgamma/STAT1-stimulated transcription. Taken together these results demonstrate that STAT6 mediates suppression of STAT1 and NF-kappaB-dependent transcription by distinct mechanisms. Both processes are dependent upon the STAT6 transactivation domain and may involve sequestration of necessary but different transcriptional coactivator proteins. These two suppressive mechanisms are controlled differentially by the nature of the STAT6 DNA-binding site (i.e. N3 versus N4).

Ras oncoprotein induces CD44 cleavage through phosphoinositide 3-OH kinase and the rho family of small G proteins

CD44 is a cell surface adhesion molecule for several extracellular matrix components. We previously showed that CD44 expressed in cancer cells is proteolytically cleaved at the ectodomain through membrane-anchored metalloproteases and that CD44 cleavage plays a critical role in cancer cell migration. Therefore, cellular signals that promote the migration and metastatic activity of cancer cells may regulate the CD44 ectodomain cleavage. Here, we demonstrate that the expression of the dominant active mutant of Ha-Ras (Ha-Ras(Val-12)) induces redistribution of CD44 to the newly generated membrane ruffling area and CD44 ectodomain cleavage. The migration assay revealed that the CD44 cleavage contributes to the Ha-Ras(Val-12)-induced migration of NIH3T3 cells on hyaluronate substrate. Treatment with LY294002, an inhibitor for phosphoinositide 3-OH kinase (PI3K), significantly inhibits Ha-Ras(Val-12)-induced CD44 cleavage, whereas that with PD98059, an inhibitor for MEK, does not. The active mutant p110 subunit of PI3K has also been shown to enhance the CD44 cleavage, suggesting that PI3K mediates the Ras-induced CD44 cleavage. Moreover, the expression of dominant negative mutants of Cdc42 and Rac1 inhibits the Ha-Ras(Val-12)-induced CD44 cleavage. These results suggest that Ras > PI3K > Cdc42/Rac1 pathway plays an important role in CD44 cleavage and may provide a novel molecular basis to explain how the activated Ras facilitates cancer cell migration.

Interactions between phosphatidylinositol 3-kinase and nitric oxide: explaining the paradox

Nitric oxide (NO) and the many derivatives and reactive oxygen intermediates thereof are all molecules that are utilised by mammalian cells in the war against microbial pathogens and tumours. They are potentially toxic molecules and, with damage control being crucial, the production and metabolism of nitric oxide is a tightly regulated process. The duality of NO is well documented. On the one hand, beneficial effects include normal healing in the skin and intestinal mucosa, killing of certain bacteria, regulating T cell proliferation and differentiation (Th1 vs Th2), and regulating leukocyte recruitment, by affecting adhesion molecule expression. On the other hand, persistent high levels of NO can lead to the production of toxic metabolites (peroxynitrite and hydroxyls), which can have detrimental effects, such as increased microvascular and epithelial permeability, increased oxidative stress (which can damage DNA), and damage to iron-sulphur proteins in mitochondria. NO has been reported to modulate its own production and the mechanisms involved in this self-regulation are being hotly pursued. The purpose of this review is to update recent intriguing advances in our understanding of the interaction of the phosphatidylinositol (PI) 3-kinase-dependent signal transduction pathway in regulating the activity of the enzymes that generate NO, namely, the nitric oxide synthases.

Cross-talk between phosphatidylinositol 3-kinase and sphingomyelinase pathways as a mechanism for cell survival/death decisions

Peptide hormones act to regulate apoptosis through activation of multiple pro- and anti-apoptotic signaling cascades of which lipid signaling events represent an important facet of the cellular rheostat that determines survival and death decisions. Activation of sphingomyelinase, which generates ceramide, is an intermediate in cellular stress responses and induction of apoptosis in many systems. Conversely, phosphatidylinositol 3-kinase (PI3K) is a critical signaling molecule involved in regulating cell survival and proliferation pathways. In the present study, we investigate cross-talk between the PI3K and sphingomyelinase pathways as a mechanism for regulation of cell survival/death decisions. We show that phorbol ester, insulin-like growth factor 1, and a constitutively active PI3K suppress both tumor necrosis factor-induced apoptosis and ceramide generation. Conversely, inhibition of the PI3K pathway with expression of a kinase-dead PI3K both prevented survival signaling and enhanced tumor necrosis factor-induced ceramide generation. The ability of exogenous sphingomyelinase to induce ceramide generation was partially suppressed by expression of constitutively active PI3K and enhanced by inhibition of PI3K suggesting that cross-talk between PI3K and ceramide generation within cells is regulated subsequent to activation of sphingomyelinase.

Syndecan-1 shedding is enhanced by LasA, a secreted virulence factor of Pseudomonas aeruginosa

Microbial pathogens frequently take advantage of host systems for their pathogenesis. Shedding of cell surface molecules as soluble extracellular domains (ectodomains) is one of the host responses activated during tissue injury. In this study, we examined whether pathogenic bacteria can modulate shedding of syndecan-1, the predominant syndecan of host epithelia. Our studies found that overnight culture supernatants of Pseudomonas aeruginosa and Staphylococcus aureus enhanced the shedding of syndecan-1 ectodomains, whereas culture supernatants of several other Gram-negative and Gram-positive bacteria had only low levels of activity. Because supernatants from all tested strains of P. aeruginosa (n = 9) enhanced syndecan-1 shedding by more than 4-fold above control levels, we focused our attention on this Gram-negative bacterium. Culture supernatants of P. aeruginosa increased shedding of syndecan-1 in both a concentration- and time-dependent manner, and augmented shedding by various host cells. A 20-kDa shedding enhancer was partially purified from the supernatant through ammonium sulfate precipitation and gel chromatography, and identified by N-terminal sequencing as LasA, a known P. aeruginosa virulence factor. LasA was subsequently determined to be a syndecan-1 shedding enhancer from the findings that (i) immunodepletion of LasA from the partially purified sample resulted in abrogation of its activity to enhance shedding and (ii) purified LasA increased shedding in a concentration-dependent manner. Our results also indicated that LasA enhances syndecan-1 shedding by activation of the host cell's shedding mechanism and not by direct interaction with syndecan-1 ectodomains. Enhanced syndecan-1 shedding may be a means by which pathogenic bacteria take advantage of a host mechanism to promote their pathogenesis.

Inflammatory cytokines and cell response in surgery

The systemic inflammatory response as mediated by the cytokine network is undoubtedly complex. While inflammatory cytokines are indispensable in wound healing and the restoration of homeostasis, it is often the excessive activity of either proinflammatory or anti-inflammatory cytokines that causes injury to the host or renders the host immunocompromised, respectively. Central to the functional biology of cytokines in surgical injury and infections are the responses of immune cells to such insults. It is clear that immunocytes are the source of cytokine production, and these products possess important autocrine, as well as systemic activities. The ability to alter immunocyte function through extracellular hormonal influences or by manipulating intracellular signaling mechanisms are potential strategies for regulating the inflammatory cytokine response during injury.

Diverse agents act at multiple levels to inhibit the Rel/NF-kappaB signal transduction pathway

Rel/NF-kappaB transcription factors regulate several important physiological processes, including developmental processes, inflammation and immune responses, cell growth, cancer, apoptosis, and the expression of certain viral genes. Therefore, they have also been sought-after molecular targets for pharmacological intervention. As details of the Rel/NF-kappaB signal transduction pathway are revealed, it is clear that modulators of this pathway can act at several levels. Inhibitors of the Rel/NF-kappaB pathway include a variety of natural and designed molecules, including anti-oxidants, proteasome inhibitors, peptides, small molecules, and dominant-negative or constitutively active polypeptides in the pathway. Several of these molecules act as general inhibitors of Rel/NF-kappaB induction, whereas others inhibit specific pathways of induction. Inhibitors of Rel/NF-kappaB are likely to gain stature as treatments for certain cancers and neurodegenerative and inflammatory diseases.

TNF-induced signaling in apoptosis

Out of the almost 17 members of the TNF superfamily, TNF is probably the most potent inducer of apoptosis. TNF activates both cell-survival and cell-death mechanisms simultaneously. Activation of NF-kB-dependent genes regulates the survival and proliferative effects pf TNF, whereas activation of caspases regulates the apoptotic effects. TNF-induced apoptosis is mediated primarily through the activation of type I receptors, the death domain of which recruits more than a dozen different signaling proteins, which together are considered part of an apoptotic cascade. This cascade does not, however, account for the role of reactive oxygen intermediates, ceramide, phospholipases, and serine proteases which are also implicated in TNF-induced apoptosis. This cascade also does not explain how type II TNF receptors which lack the death domain, induce apoptosis. Nevertheless, this review of apoptosis signaling will be limited to those proteins that makeup the cascade.

Downregulation of endothelin-1 by interleukin-4 during gastric ulcer healing

We investigated the course of events associated with gastric ulcer healing by analyzing mucosal expression of interleukin-4 (IL-4), endothelin-1 (ET-1), tumor necrosis factor-alpha (TNF-alpha), and the activity of constitutive (cNOS) and inducible nitric oxide synthase (NOS-2). Ulcer onset was characterized by a massive epithelial apoptosis associated with a 5.7-fold increase in TNF-alpha, a 17.5-fold increase in NOS-2, and a 3.9-fold increase in ET-1, while mucosal expression of cNOS showed a 7.6-fold drop and IL-4 fell by 37.2%. Healing was accompanied by a rapid raise in IL-4; decrease in apoptosis, TNF-alpha, ET-1, and NOS-2; and a slow recovery in cNOS. The expression of IL-4 returned to control levels by the 7th day of healing and that of ET-1 and TNF-alpha by the 14th day, while apoptotic DNA fragmentation and the activity of NOS-2 remained significantly elevated beyond the 14-day period. The results suggest that a decrease in the mucosal level of IL-4 at ulcer onset may well be a key factor causing dysregulation of ET-1 production, induction of TNF-alpha, and triggering the apoptotic events that affect the efficiency of mucosal repair.

The Human B Cell Response to IL-13 Is Dependent on Cellular Phenotype as Well as Mode of Activation

Normal mature quiescent human B lymphocytes, isolated as a function of buoyant density, require activation for up-regulation of IL-13R constituents. Cell activation through a combination of surface Ig and CD40 receptor ligation leads to the most substantial message production for IL-13Rα1. Functional consequences of this receptor variation, in initially quiescent cells, includes demonstrable effects on cellular proliferation in response to ligand exposure. Variations in the method of surface activation, with particular emphasis on the CD40 receptor, reveals that immobilized CD40 ligand may be sufficient, in and of itself, to up-regulate IL-13Rα1, which may bear significance for B-lymphocyte bystander proliferation. Regulation of the IL-13Rα1 protein and message also differs as a function of cellular phenotype. Although values are greater in memory than naive B cells, as they are initially isolated from extirpated tonsils, variations in the magnitude of message and protein, as a function of surface stimulation, are more substantial in the naive subset. The magnitude of variation in message production in naive cells is associated with a more vigorous proliferative response to IL-13 than seen in memory lymphocytes. The cellular response to IL-13, as a function of activation and phenotype, is the converse of that demonstrated for IL-2. Evaluation of proliferation, receptor message, ligand binding protein production, and the response to putatively synergistic cytokines reveals that IL-2 is the predominant lymphokine utilized by memory cells. This is in contradistinction to IL-13, which along with IL-4, are the predominant moieties for naive lymphocytes.