Inhibitory Fc-Gamma IIb Receptor Signaling Induced by Multivalent IgG-Fc Is Dependent on Sialylation

Immunoglobulin (IgG) Fc glycosylation has been shown to be important for the biological activity of antibodies. Fc sialylation is important for the anti-inflammatory activity of IgGs. However, evaluating the structure-activity relationship (SAR) of antibody Fc glycosylation has been hindered using simplified in vitro models in which antibodies are often displayed in monomeric forms. Presenting antibodies in monomeric forms may not accurately replicate the natural environment of the antibodies when binding their antigen in vivo. To address these limitations, we used different Fc-containing molecules, displaying their Fc domains in monovalent and multivalent fashion. Given the inhibitory role of Fc gamma receptor IIb (FcγRIIb) in autoimmune and inflammatory diseases, we focused on evaluating the impact of Fc sialylation on the activation of FcγRIIb. We report for the first time that in human cellular systems, sialic acid mediates the induction of FcγRIIb phosphorylation by IgG-Fc when the IgG-Fc is displayed in a multivalent fashion. This effect was observed with different types of therapeutic agents such as sialylated anti-TNFα antibodies, sialylated IVIg and sialylated recombinant multivalent Fc products. These studies represent the first report of the specific effects of Fc sialylation on FcγRIIb signaling on human immune cells and may help in the characterization of the anti-inflammatory activity of Fc-containing therapeutic candidates.

Multiomic study of skin, peripheral blood, and serum: is serum proteome a reflection of disease process at the end-organ level in systemic sclerosis?

BACKGROUND

Serum proteins can be readily assessed during routine clinical care. However, it is unclear to what extent serum proteins reflect the molecular dysregulations of peripheral blood cells (PBCs) or affected end-organs in systemic sclerosis (SSc). We conducted a multiomic comparative analysis of SSc serum profile, PBC, and skin gene expression in concurrently collected samples.

METHODS

Global gene expression profiling was carried out in skin and PBC samples obtained from 49 SSc patients enrolled in the GENISOS observational cohort and 25 unaffected controls. Levels of 911 proteins were determined by Olink Proximity Extension Assay in concurrently collected serum samples.

RESULTS

Both SSc PBC and skin transcriptomes showed a prominent type I interferon signature. The examination of SSc serum profile revealed an upregulation of proteins involved in pro-fibrotic homing and extravasation, as well as extracellular matrix components/modulators. Notably, several soluble receptor proteins such as EGFR, ERBB2, ERBB3, VEGFR2, TGFBR3, and PDGF-Rα were downregulated. Thirty-nine proteins correlated with severity of SSc skin disease. The differential expression of serum protein in SSc vs. control comparison significantly correlated with the differential expression of corresponding transcripts in skin but not in PBCs. Moreover, the differentially expressed serum proteins were significantly more connected to the Well-Associated-Proteins in the skin than PBC gene expression dataset. The assessment of the concordance of between-sample similarities revealed that the molecular profile of serum proteins and skin gene expression data were significantly concordant in patients with SSc but not in healthy controls.

CONCLUSIONS

SSc serum protein profile shows an upregulation of profibrotic cytokines and a downregulation of soluble EGF and other key receptors. Our multilevel comparative analysis indicates that the serum protein profile in SSc correlates more closely with molecular dysregulations of skin than PBCs and might serve as a reflection of disease severity at the end-organ level.

Engineered IgG1-Fc Molecules Define Valency Control of Cell Surface Fcγ Receptor Inhibition and Activation in Endosomes

The inhibition of Fcγ receptors (FcγR) is an attractive strategy for treating diseases driven by IgG immune complexes (IC). Previously, we demonstrated that an engineered tri-valent arrangement of IgG1 Fc domains (SIF1) potently inhibited FcγR activation by IC, whereas a penta-valent Fc molecule (PentX) activated FcγR, potentially mimicking ICs and leading to Syk phosphorylation. Thus, a precise balance exists between the number of engaged FcγRs for inhibition versus activation. Here, we demonstrate that Fc valency differentially controls FcγR activation and inhibition within distinct subcellular compartments. Large Fc multimer clusters consisting of 5-50 Fc domains predominately recruited Syk-mScarlet to patches on the plasma membrane, whereas PentX exclusively recruited Syk-mScarlet to endosomes in human monocytic cell line (THP-1 cells). In contrast, SIF1, similar to monomeric Fc, spent longer periods docked to FcγRs on the plasma membrane and did not accumulate and recruit Syk-mScarlet within large endosomes. Single particle tracking (SPT) of fluorescent engineered Fc molecules and Syk-mScarlet at the plasma membrane imaged by total internal reflection fluorescence microscopy (SPT-TIRF), revealed that Syk-mScarlet sampled the plasma membrane was not recruited to FcγR docked with any of the engineered Fc molecules at the plasma membrane. Furthermore, the motions of FcγRs docked with recombinant Fc (rFc), SIF1 or PentX, displayed similar motions with D ~ 0.15 μm²/s, indicating that SIF1 and PentX did not induce reorganization or microclustering of FcγRs beyond the ligating valency. Multicolor SPT-TIRF and brightness analysis of docked rFc, SIF1 and PentX also indicated that FcγRs were not pre-assembled into clusters. Taken together, activation on the plasma membrane requires assembly of more than 5 FcγRs. Unlike rFc or SIF1, PentX accumulated Syk-mScarlet on endosomes indicating that the threshold for FcγR activation on endosomes is lower than on the plasma membrane. We conclude that the inhibitory effects of SIF1 are mediated by stabilizing a ligated and inactive FcγR on the plasma membrane. Thus, FcγR inhibition can be achieved by low valency ligation with SIF1 that behaves similarly to FcγR docked with monomeric IgG.

Variable blood processing procedures contribute to plasma proteomic variability

Background

Plasma is a potentially rich source of protein biomarkers for disease progression and drug response. Large multi-center studies are often carried out to increase the number of samples analyzed in a given study. This may increase the chances of variation in blood processing and handling, leading to altered proteomic results. This study evaluates the impact of blood processing variation on LC–MS/MS proteomic analysis of plasma.

Methods

Initially two batches of patient plasma samples (120 and 204 samples, respectively) were analyzed using LC–MS/MS shotgun proteomics. Follow-up experiments were designed and carried out on healthy donor blood in order to examine the effects of different centrifugation conditions, length of delay until first centrifugation, storage temperature and anticoagulant type on results from shotgun proteomics.

Results

Variable levels of intracellular proteins were observed in subsets of patient plasma samples from the initial batches analyzed. This observation correlated strongly with the site of collection, implicating variability in blood processing procedures. Results from the healthy donor blood analysis did not demonstrate a significant impact of centrifugation conditions to plasma proteome variation. The time delay until first centrifugation had a major impact on variability, while storage temperature and anticoagulant showed less pronounced but still significant effects. The intracellular proteins associated with study site effect in patient plasma samples were significantly altered by delayed processing also.

Conclusions

Variable blood processing procedures contribute significantly to plasma proteomic variation and may give rise to increased intracellular proteins in plasma. Accounting for these effects can be important both at study design and data analysis stages. This understanding will be valuable to incorporate in the planning of protein-based biomarker discovery efforts in the future.

Characterization of Endogenous Human FcγRIII by Mass Spectrometry Reveals Site, Allele and Sequence Specific Glycosylation

Characterization of endogenous FcγRIII glycosylation from healthy donors with different FcγRIIIb genotypes reveals site specific, and allele specific differences in glycosylation as well as noncananonical sequence specific differences in glycosylation. We propose these differences in glycosylation may influence the differential activity seen for neutrophils across genotypes.

The importance of IgG glycosylation, Fc-gamma receptor (FcγR) single nucleotide polymorphisms and FcγR copy number variations in fine tuning the immune response has been well established. There is a growing appreciation of the importance of glycosylation of FcγRs in modulating the FcγR-IgG interaction based on the association between the glycosylation of recombinant FcγRs and the kinetics and affinity of the FcγR-IgG interaction. Although glycosylation of recombinant FcγRs has been recently characterized, limited knowledge exists on the glycosylation of endogenous human FcγRs. In order to improve the structural understanding of FcγRs expressed on human cells we characterized the site specific glycosylation of native human FcγRIII from neutrophils of 50 healthy donors and from matched plasma for 43 of these individuals. Through this analysis we have confirmed site specific glycosylation patterns previously reported for soluble FcγRIII from a single donor, identified FcγRIIIb specific Asn45 glycosylation and an allelic effect on glycosylation at Asn162 of FcγRIIIb. Identification of FcγRIIIb specific glycosylation allows for assignment of FcγRIIIb alleles and relative copy number of the two alleles where DNA/RNA is not available. Intriguingly the types of structures found to be elevated at Asn162 in the NA2 allele have been shown to destabilize the Fc:FcγRIII interaction resulting in a faster dissociation rate. These differences in glycosylation may in part explain the differential activity reported for the two alleles which have similar in vitro affinity for IgG.

Enhancing reproducibility of gene expression analysis with known protein functional relationships: The concept of well-associated protein

Identification of differentially expressed genes (DEGs) is well recognized to be variable across independent replications of genome-wide transcriptional studies. These are often employed to characterize disease state early in the process of discovery and prioritize novel targets aimed at addressing unmet medical need. Increasing reproducibility of biological findings from these studies could potentially positively impact the success rate of new clinical interventions. This work demonstrates that statistically sound combination of gene expression data with prior knowledge about biology in the form of large protein interaction networks can yield quantitatively more reproducible observations from studies characterizing human disease. The novel concept of Well-Associated Proteins (WAPs) introduced herein-gene products significantly associated on protein interaction networks with the differences in transcript levels between control and disease-does not require choosing a differential expression threshold and can be computed efficiently enough to enable false discovery rate estimation via permutation. Reproducibility of WAPs is shown to be on average superior to that of DEGs under easily-quantifiable conditions suggesting that they can yield a significantly more robust description of disease. Enhanced reproducibility of WAPs versus DEGs is first demonstrated with four independent data sets focused on systemic sclerosis. This finding is then validated over thousands of pairs of data sets obtained by random partitions of large studies in several other diseases. Conditions that individual data sets must satisfy to yield robust WAP scores are examined. Reproducible identification of WAPs can potentially benefit drug target selection and precision medicine studies.

Abstract 3244: Improved Fc-mediated effector functions by an anti-CTLA-4 multivalent Fc agent

Numerous therapeutic monoclonal antibodies (mAbs) rely on antibody-dependent cell cytotoxicity (ADCC), antibody-dependent cell phagocytosis (ADCP) and complement-dependent cytotoxicity (CDC) Fc effector functions to deplete target cells and achieve clinical efficacy. It has been previously shown that adding multiple Fc domains to Abs or afucosylating the Fc domain increases Fc effector functions. We have leveraged a proprietary Fc multimerization technology (SIF; selective immunomodulator of Fc receptors) to identify potential novel products designed to improve the immune system’s elimination of tumor and other pathogenic cells. These agents utilize the valency effect of Fc multimerization to increase the binding to Fc receptors and complement, enhancing immune-mediated cytotoxicity mechanisms. CTLA-4 is a clinically validated immune checkpoint inhibitor exemplified by the human IgG1 therapeutic mAb ipilimumab. CTLA-4 is induced upon activation on T cells and constitutively expressed on T regulatory cells (Tregs). Based on data from mouse models of cancer and clinical studies, the proposed mechanisms of action of anti-CTLA-4 mAbs, including ipilimumab, are to block the interaction of CTLA-4 with its ligands CD80 and CD86 resulting in T cell activation and to induce Fc-mediated ADCC of CTLA-4+ cells, mainly intratumoral Tregs. Therefore, we have produced an anti-CTLA-4 multivalent IgG1 Fc agent termed anti-CTLA-4 SIFbody with the purpose of enhancing binding to Fc gamma receptors (FcγRs) and complement and increasing Fc-mediated elimination of intratumoral Tregs. Data from avidity binding to low affinity FcγRs showed more than 100-fold increase with anti-CTLA-4 SIFbody as compared to ipilimumab. In in vitro functional assays using CTLA-4 transfected target cells and primary human effector cells, anti-CTLA-4 SIFbody showed more than 10-fold increase in potency in ADCC and more than 5-fold increase in ADCP as compared to ipilimumab. Anti-CTLA-4 SIFbody induced 80% cell lysis by CDC, whereas ipilimumab failed to show any activity. More importantly, we generated in vitro expanded Tregs with suppressive function and showed that anti-CTLA-4 SIFbody induced significant enhanced ADCC on these cells as compared to ipilimumab and to an afucosylated anti-CTLA-4 mAb. ADCP was also significantly increased on Tregs. Unexpectedly, Tregs were resistant to anti-CTLA-4 SIFbody induced CDC. Notably, the blocking activity of the SIFbody F(ab)s was not altered by the multivalent Fc structure as shown by similar CTLA-4/CD80 and CD86 blockade and induction of IL-2 production upon antigen stimulation of PBMC. In conclusion, these data demonstrate that our Fc multimerization technology applied to an anti-CTLA-4 mAb significantly improves Fc-dependent immune-mediated cytotoxicity and suggest that anti-CTLA-4 SIFbody may represent an optimized novel product to deplete intratumoral Tregs and enhance anti-tumor activity.

Citation Format: Laura Rutitzky, Daniel F. Ortiz, Jonathan C. Lansing, Julia Brown, Joseph Paquette, Kevin Garofalo, Josephine D'Alessandro, Naveen Bhatnagar, Maurice Hains, Abhinav Gupta, Stan Lee, Radouane Zouaoui, Jason Wang, John Schaeck, Salvatore Marchese, Robin Meccariello, Nathaniel Washburn, Kimberly Holte, Carlos J. Bosques, Anthony M. Manning. Improved Fc-mediated effector functions by an anti-CTLA-4 multivalent Fc agent [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3244.

Abstract 561: Discovery of a potential best-in-class anti-CD38 therapeutic utilizing Fc multimerization

CD38 targeting antibodies are at different phases of clinical development, with daratumumab already approved as monotherapy and in combination with standards of care in multiple myeloma (MM). Anti-CD38 monoclonal antibodies (mAbs) induce tumor cell depletion in part by Fc-dependent effector mechanisms such as antibody dependent cellular cytotoxicity (ADCC), antibody dependent cellular phagocytosis (ADCP), and complement dependent cytotoxicity (CDC). However, not all MM patients achieve minimal residual disease (MRD)-negativity and similar clinical response. In addition, some patients on daratumumab develop resistance due to reduced cell surface CD38 and high levels of complement inhibitors (CD55 and CD59). We have leveraged Fc multimerization technology (Ortiz et al Sci Transl Med. 2016; 8: 365) to generate an optimized platform (SIF; selective immunomodulator of Fc receptors) that utilizes the valency effect of Fc multimerization to enhance binding to the Fcγ receptors and complement. We combined the Fab-region of CD38 targeting mAb to SIF platform to generate an anti-CD38 SIFbody to enhance immune and complement mediated cytotoxicity against tumor cells. In several human tumor cell line-based cytotoxic assays using primary human effector cells (NK cells and macrophages) and complement, the anti-CD38 SIFbody demonstrates up to 10-fold increase in efficacy and ≥16-fold increase in potency compared to daratumumab and the surrogate therapeutic anti-CD38 mAb (TAK-079). In isolated whole human blood incubated with tumor cells, the anti-CD38 SIFbody demonstrated 40-100 fold increase in potency and 2-3 fold increase in efficacy. In bone marrow cells isolated from MM patients with >80% plasma cells anti-CD38 SIFbody showed better potency and a 3-5 fold increased efficacy (with 100% plasma cell elimination) than daratumumab, suggesting the SIFbody may be more suitable molecule for achieving greater MRD-negativity rates in MM patients. Daratumumab fails to induce CDC against tumor cell lines with low CD38 and high CD55 and CD59, however the SIFbody achieves 100% efficacy in such settings, suggesting this molecule may be effective in patients who are developing resistance to treatment. In single dose pharmacodynamic and tolerability studies in cynomolgus monkeys SIFbody demonstrated up to 5-fold increase in B cell depletion from peripheral blood compared to TAK-079 across all dose ranges (0.3, 1, & 3 mg/kg) tested without any adverse events. Therefore, by leveraging our Fc multimerization technology we have generated a differentiated potential best-in-class anti-CD38 therapeutic.

Citation Format: Amit Choudhury, Daniel F. Ortiz, Shannon Argueta, Kevin Garofalo, Jonathan C. Lansing, Utsav Jetley, Danice Wilkins, Carlos Bosques, Edward Cochran, Naveen Bhatnagar, Jay Duffner, Abhinav Gupta, Stan Lee, Karunya Srinivasan, Viraj Parge, Radouane Zouaoui, Jason Wang, Anthony M. Manning. Discovery of a potential best-in-class anti-CD38 therapeutic utilizing Fc multimerization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 561.

Circulating Markers of Inflammation Persist in Children and Adults With Giant Aneurysms After Kawasaki Disease

Background:

The sequelae of Kawasaki disease (KD) vary widely with the greatest risk for future cardiovascular events among those who develop giant coronary artery aneurysms (CAA). We sought to define the molecular signature associated with different outcomes in pediatric and adult KD patients.

Methods:

Molecular profiling was conducted using mass spectrometry–based shotgun proteomics, transcriptomics, and glycomics methods on 8 pediatric KD patients at the acute, subacute, and convalescent time points. Shotgun proteomics was performed on 9 KD adults with giant CAA and matched healthy controls. Plasma calprotectin was measured by ELISA in 28 pediatric KD patients 1 year post-KD, 70 adult KD patients, and 86 healthy adult volunteers.

Results:

A characteristic molecular profile was seen in pediatric patients during the acute disease, which resolved at the subacute and convalescent periods in patients with no coronary artery sequelae but persisted in 2 patients who developed giant CAA. We, therefore, investigated persistence of inflammation in KD adults with giant CAA by shotgun proteomics that revealed a signature of active inflammation, immune regulation, and cell trafficking. Correlating results obtained using shotgun proteomics in the pediatric and adult KD cohorts identified elevated calprotectin levels in the plasma of patients with CAA. Investigation of expanded pediatric and adult KD cohorts revealed elevated levels of calprotectin in pediatric patients with giant CAA 1 year post-KD and in adult KD patients who developed giant CAA in childhood.

Conclusions:

Complex patterns of biomarkers of inflammation and cell trafficking can persist long after the acute phase of KD in patients with giant CAA. Elevated levels of plasma calprotectin months to decades after acute KD and infiltration of cells expressing S100A8 and A9 in vascular tissues suggest ongoing, subclinical inflammation. Calprotectin may serve as a biomarker to inform the management of KD patients following the acute illness.

M281, an Anti-FcRn Antibody: Pharmacodynamics, Pharmacokinetics, and Safety Across the Full Range of IgG Reduction in a First-in-Human Study

M281 is a fully human, anti-neonatal Fc receptor (FcRn) antibody that inhibits FcRn-mediated immunoglobulin G (IgG) recycling to decrease pathogenic IgG while preserving IgG production. A randomized, double-blind, placebo-controlled, first-in-human study with 50 normal healthy volunteers was designed to probe safety and the physiological maximum for reduction of IgG. Intravenous infusion of single ascending doses up to 60 mg/kg induced dose-dependent serum IgG reductions, which were similar across all IgG subclasses. Multiple weekly doses of 15 or 30 mg/kg achieved mean IgG reductions of ≈85% from baseline and maintained IgG reductions ≥75% from baseline for up to 24 days. M281 was well tolerated, with no serious or severe adverse events (AEs), few moderate AEs, and a low incidence of infection-related AEs similar to placebo treatment. The tolerability and consistency of M281 pharmacokinetics and pharmacodynamics support further evaluation of M281 in diseases mediated by pathogenic IgG.

Elucidating the interplay between IgG-Fc valency and FcγR activation for the design of immune complex inhibitors

Autoantibody immune complex (IC) activation of Fcγ receptors (FcγRs) is a common pathogenic hallmark of multiple autoimmune diseases. Given that the IC structural features that elicit FcγR activation are poorly understood and the FcγR system is highly complex, few therapeutics can directly block these processes without inadvertently activating the FcγR system. To address these issues, the structure activity relationships of an engineered panel of multivalent Fc constructs were evaluated using sensitive FcγR binding and signaling cellular assays. These studies identified an Fc valency with avid binding to FcγRs but without activation of immune cell effector functions. These observations directed the design of a potent trivalent immunoglobulin G-Fc molecule that broadly inhibited IC-driven processes in a variety of immune cells expressing FcγRs. The Fc trimer, Fc3Y, was highly efficacious in three different animal models of autoimmune diseases. This recombinant molecule may represent an effective therapeutic candidate for FcγR-mediated autoimmune diseases.

Fc-gamma receptors: Attractive targets for autoimmune drug discovery searching for intelligent therapeutic designs

Autoantibody immune complexes (ICs) mediate pathogenesis in multiple autoimmune diseases via direct interference with target function, complement fixation, and interaction with Fc-gamma receptors (FcγRs). Through high avidity interactions, ICs are able to crosslink low affinity FcγRs expressed on a wide variety of effector cells, leading to secretion of pro-inflammatory mediators and inducing cytotoxicity, ultimately resulting in tissue injury. Given their relevance in numerous autoimmune diseases, FcγRs have been considered as attractive therapeutic targets for the last three decades. However, a limited number of investigational drug candidates have been developed targeting FcγRs and only a few approved therapeutics have been associated with impacting FcγRs. This review provides a historical overview of the different therapeutic approaches used to target FcγRs for the treatment of autoimmune and inflammatory diseases.

A Quantitative Microtiter Assay for Sialylated Glycoform Analyses Using Lectin Complexes

Fidelity of glycan structures is a key requirement for biotherapeutics, with carbohydrates playing an important role for therapeutic efficacy. Comprehensive glycan profiling techniques such as liquid chromatography (LC) and mass spectrometry (MS), while providing detailed description of glycan structures, require glycan cleavage, labeling, and paradigms to deconvolute the considerable data sets they generate. On the other hand, lectins as probes on microarrays have recently been used in orthogonal approaches for in situ glycoprofiling but require analyte labeling to take advantage of the capabilities of automated microarray readers and data analysis they afford. Herein, we describe a lectin-based microtiter assay (lectin–enzyme-linked immunosorbent assay [ELISA]) to quantify terminal glycan moieties, applicable to in vitro and in-cell glycan-engineered Fc proteins as well as intact IgGs from intravenous immunoglobulin (IVIG), a blood product containing pooled polyvalent IgG antibodies extracted from plasma from healthy human donors. We corroborate our findings with industry-standard LC-MS profiling. This “customizable” ELISA juxtaposes readouts from multiple lectins, focusing on a subset of glycoforms, and provides the ability to discern single- versus dual-arm glycosylation while defining levels of epitopes at sensitivities comparable to MS. Extendable to other biologics, this ELISA can be used stand-alone or complementary to MS for quantitative glycan analysis.

Pamapimod, a novel p38 mitogen-activated protein kinase inhibitor: preclinical analysis of efficacy and selectivity

P38alpha is a protein kinase that regulates the expression of inflammatory cytokines, suggesting a role in the pathogenesis of diseases such as rheumatoid arthritis (RA) or systemic lupus erythematosus. Here, we describe the preclinical pharmacology of pamapimod, a novel p38 mitogen-activated protein kinase inhibitor. Pamapimod inhibited p38alpha and p38beta enzymatic activity, with IC(50) values of 0.014 +/- 0.002 and 0.48 +/- 0.04 microM, respectively. There was no activity against p38delta or p38gamma isoforms. When profiled across 350 kinases, pamapimod bound only to four kinases in addition to p38. Cellular potency was assessed using phosphorylation of heat shock protein-27 and c-Jun as selective readouts for p38 and c-Jun NH(2)-terminal kinase (JNK), respectively. Pamapimod inhibited p38 (IC(50), 0.06 microM), but inhibition of JNK was not detected. Pamapimod also inhibited lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) alpha production by monocytes, interleukin (IL)-1beta production in human whole blood, and spontaneous TNFalpha production by synovial explants from RA patients. LPS- and TNFalpha-stimulated production of TNFalpha and IL-6 in rodents also was inhibited by pamapimod. In murine collagen-induced arthritis, pamapimod reduced clinical signs of inflammation and bone loss at 50 mg/kg or greater. In a rat model of hyperalgesia, pamapimod increased tolerance to pressure in a dose-dependent manner, suggesting an important role of p38 in pain associated with inflammation. Finally, an analog of pamapimod that has equivalent potency and selectivity inhibited renal disease in lupus-prone MRL/lpr mice. Our study demonstrates that pamapimod is a potent, selective inhibitor of p38alpha with the ability to inhibit the signs and symptoms of RA and other autoimmune diseases.

Transcription inhibitors in inflammation

Advances in molecular medicine have revealed a key role for altered gene expression in the aetiology of many inflammatory diseases, including asthma, rheumatoid arthritis, inflammatory bowel disease and sepsis. Until recently, however, modulation of gene transcription has not been the subject of directed pharmaceutical research efforts. Notwithstanding, it is clear that the efficacy of several well-established anti-inflammatory therapeutics is mediated through their ability to modulate gene transcription. Understanding the mechanisms of action of these therapeutics and defining new gene regulatory pathways has stimulated a new wave of anti-inflammatory drug discovery. This update aims to cover our current understanding of transcription inhibitors in inflammation, including the mechanism of action of established therapeutics and the properties of new chemical entities recently described in the literature.

Targeting JNK for therapeutic benefit: from junk to gold?

The c-Jun NH(2)-terminal kinases (JNKs) phosphorylate and activate members of the activator protein-1 (AP-1) transcription factor family and other cellular factors implicated in regulating altered gene expression, cellular survival and proliferation in response to cytokines and growth factors, noxious stimuli and oncogenic transformation. Because these events are commonly associated with the pathogenesis of a number of human diseases, the potential of JNK inhibitors as therapeutics has attracted considerable interest. Here we discuss the evidence supporting the application of JNK inhibitors in inflammatory, vascular, neurodegenerative, metabolic and oncological diseases in humans, and describe the present status of drug discovery targeting JNK.

Differential requirement for NF-kappaB-inducing kinase in the induction of NF-kappaB by IL-1beta, TNF-alpha, and Fas

In this study, we examined the role of the nuclear factor-kappaB (NF-kappaB)-inducing kinase (NIK) in distinct signaling pathways leading to NF-kappaB activation. We show that a dominant-negative form of NIK (dnNIK) delivered by adenoviral (Ad5dnNIK) vector inhibits Fas-induced IkappaBalpha phosphorylation and NF-kappaB-dependent gene expression in HT-29 and HeLa cells. Interleukin (IL)-1beta- and tumor necrosis factor-alpha (TNF-alpha)-induced NF-kappaB activation and kappaB-dependent gene expression are inhibited in HeLa cells but not in Ad5dnNIK-infected HT-29 cells. Moreover, Ad5dnNIK failed to sensitize HT-29 cells to TNF-alpha-induced apoptosis at an early time point. However, cytokine- and Fas-induced signals to NF-kappaB are finally integrated by the IkappaB kinase (IKK) complex, since IkappaBalpha phosphorylation, NF-kappaB DNA binding activity, and IL-8 gene expression were strongly inhibited in HT-29 and HeLa cells overexpressing dominant-negative IKKbeta (Ad5dnIKKbeta). Our findings support the concept that cytokine signaling to NF-kappaB is redundant at the level of NIK. In addition, this study demonstrates for the first time the critical role of NIK and IKKbeta in Fas-induced NF-kappaB signaling cascade.

SP600125, an anthrapyrazolone inhibitor of Jun N-terminal kinase

Jun N-terminal kinase (JNK) is a stress-activated protein kinase that can be induced by inflammatory cytokines, bacterial endotoxin, osmotic shock, UV radiation, and hypoxia. We report the identification of an anthrapyrazolone series with significant inhibition of JNK1, -2, and -3 (K(i) = 0.19 microM). SP600125 is a reversible ATP-competitive inhibitor with >20-fold selectivity vs. a range of kinases and enzymes tested. In cells, SP600125 dose dependently inhibited the phosphorylation of c-Jun, the expression of inflammatory genes COX-2, IL-2, IFN-gamma, TNF-alpha, and prevented the activation and differentiation of primary human CD4 cell cultures. In animal studies, SP600125 blocked (bacterial) lipopolysaccharide-induced expression of tumor necrosis factor-alpha and inhibited anti-CD3-induced apoptosis of CD4(+) CD8(+) thymocytes. Our study supports targeting JNK as an important strategy in inflammatory disease, apoptotic cell death, and cancer.

Electrolyte disorders

Abnormal electrolyte concentrations occur commonly in hospitalized patients and may produce a variety of clinical symptoms, cause lack of response to therapeutics for primary clinical conditions, and affect clinical outcome. Recognition of electrolyte disturbances requires a high index of suspicion by the clinician for such a disturbance and prompt therapy to ensure a positive and timely outcome for the patient. This article discusses electrolyte abnormalities that occur in critically ill patients, with a review of diseases commonly associated with each electrolyte disturbance, and their recommended management.

TAK1/JNK and p38 have opposite effects on rat hepatic stellate cells

After liver injury, hepatic stellate cells (HSCs) undergo a process of activation with expression of smooth muscle alpha-actin (alpha-SMA), an increased proliferation rate, and a dramatic increase in synthesis of type I collagen. The intracellular signaling mechanisms of activation and perpetuation of the activated phenotype in HSCs are largely unknown. In this study the role of the stress-activated protein kinases, c-Jun N-terminal kinase (JNK) and p38, were evaluated in primary cultures of rat HSCs. The effect of JNK was assessed by using an adenovirus expressing a dominant negative form of transforming growth factor beta (TGF-beta)-activated kinase 1 (TAK1) (Ad5dnTAK1) and a new selective pharmacologic inhibitor SP600125. The effect of p38 was assessed with the selective pharmacologic inhibitor SB203580. These kinases were inhibited starting either in quiescent HSCs (culture day 1) or in activated HSCs (culture day 5). Although blocking TAK1/JNK and p38 decreased the expression of alpha-SMA protein in early stages of HSC activation, no effect was observed when TAK1/JNK or p38 were inhibited in activated HSCs. JNK inhibition increased and p38 inhibition decreased collagen alpha1(I) mRNA level as measured by RNase protection assays, with maximal effects observed in early stages of HSC activation. Furthermore, TAK1/JNK inhibition decreased HSC proliferation, whereas p38 inhibition led to an increased proliferation rate of HSCs, independently of its activation status. These results show novel roles for the TAK1/JNK pathway and p38 during HSC activation in culture. Despite similar activators of TAK1/JNK and p38, their functions in HSCs are distinct and opposed.

Inhibitor of nuclear factor kappaB kinase beta is a key regulator of synovial inflammation

OBJECTIVE

Inhibitor of nuclear factor kappaB kinase beta (IkappaB kinase beta, or IKKbeta) has emerged as a key regulator of the transcription factor nuclear factor kappaB (NF-kappaB). Since IKKbeta could have both pro- and antiinflammatory activity, we examined whether its constitutive activation was sufficient to cause a chronic inflammatory disease such as rheumatoid arthritis.

METHODS

Normal Lewis rats were evaluated for paw swelling by plethysmometry and histologic assessment after intraarticular injection of an adenoviral construct encoding the IKKbeta wild-type gene (Ad.IKKbeta-wt); controls received an adenoviral construct encoding green fluorescent protein (Ad.GFP). The rats were killed after 7 days. Additionally, rats were killed 48 hours after intraarticular injection of Ad.IKKbeta-wt or Ad.GFP for studies of IKK activity and NF-kappaB binding. For studies of the effects of inhibition of IKKbeta activity, Lewis rats were immunized with Mycobacterium tuberculosis in mineral oil. The ankle joints were injected on day 12 with an adenoviral construct encoding IKKbeta K-->M (dominant negative, IKKbeta-dn) or Ad.GFP. We evaluated paw swelling and NF-kappaB expression on day 25.

RESULTS

Intraarticular gene transfer of IKKbeta-wt into the joints of normal rats resulted in significant paw swelling and histologic evidence of synovial inflammation. Increased IKK activity was detectable in the IKKbeta-wt-injected ankle joints, coincident with enhanced NF-kappaB DNA binding activity. Intraarticular gene transfer of IKKbeta-dn significantly ameliorated the severity of adjuvant arthritis, accompanied by a significant decrease in NF-kappaB DNA expression in the joints of Ad.IKKbeta-dn-treated animals.

CONCLUSION

IKKbeta plays a key role in rodent synovial inflammation. Intraarticular gene therapy to inhibit IKKbeta activity represents an attractive strategy for the treatment of chronic arthritis.

c-Jun N-terminal kinase is required for metalloproteinase expression and joint destruction in inflammatory arthritis

Mitogen-activated protein kinase (MAPK) cascades are involved in inflammation and tissue destruction in rheumatoid arthritis (RA). In particular, c-Jun N-terminal kinase (JNK) is highly activated in RA fibroblast-like synoviocytes and synovium. However, defining the precise function of this kinase has been difficult because a selective JNK inhibitor has not been available. We now report the use of a novel selective JNK inhibitor and JNK knockout mice to determine the function of JNK in synoviocyte biology and inflammatory arthritis. The novel JNK inhibitor SP600125 (anthra[1,9-cd]pyrazol-6(2H)-one) completely blocked IL-1--induced accumulation of phospho-Jun and induction of c-Jun transcription in synoviocytes. Furthermore, AP-1 binding and collagenase mRNA accumulation were completely suppressed by SP600125. In contrast, complete inhibition of p38 had no effect, and ERK inhibition had only a modest effect. The essential role of JNK was confirmed in cultured synoviocytes from JNK1 knockout mice and JNK2 knockout mice, each of which had a partial defect in IL-1--induced AP-1 activation and collagenase-3 expression. Administration of SP600125 modestly decreased the rat paw swelling in rat adjuvant-induced arthritis. More striking was the near-complete inhibition of radiographic damage that was associated with decreased AP-1 activity and collagenase-3 gene expression. Therefore, JNK is a critical MAPK pathway for IL-1--induced collagenase gene expression in synoviocytes and in joint arthritis, indicating that JNK is an important therapeutic target for RA.

Evaluation of the survival prediction index as a model of risk stratification for clinical research in dogs admitted to intensive care units at four locations

OBJECTIVE

To prospectively evaluate a survival prediction index (SPI) in dogs admitted to intensive care units (ICU) and to generate and test an improved SPI (ie, SPI2).

SAMPLE POPULATION

Medical records of 624 critically ill dogs admitted to an ICU.

PROCEDURE

Data were collected from dogs within 24 hours after admission to an ICU. Variables recorded reflected function of vital organ systems, severity of underlying physiologic derangement, and extent of physiologic reserve; outcome was defined as dogs that survived or did not survive until 30 days after admission to the ICU. Probabilities of survival were calculated, using an established model (SPI). We then performed another logistic regression analysis, thereby reestimating the variables to create the new SPI2. Cross-validation of the models obtained was performed by randomly assigning the total sample of 624 dogs into an estimation group of 499 dogs and validation group of 125 dogs.

RESULTS

Testing of SPI resulted in an area under the curve (AUC) of 0.723. Testing of SPI2 revealed an AUC of 0.773. A backwards-elimination procedure was used to create a model containing fewer variables, and variables were sequentially eliminated. The AUC for the reduced model of SPI2 was 0.76, indicating little loss in predictive accuracy.

CONCLUSIONS AND CLINICAL RELEVANCE

The new SPI2 objectively stratified clinical patients into groups according to severity of disease. This index could provide an important tool for clinical research.

NF-kappaB stimulates inducible nitric oxide synthase to protect mouse hepatocytes from TNF-alpha- and Fas-mediated apoptosis

BACKGROUND AND AIMS

Hepatocyte apoptosis is induced by tumor necrosis factor alpha (TNF-alpha) and Fas ligand. Although nuclear factor-kappaB (NF-kappaB) activation protects hepatocytes from TNF-alpha-mediated apoptosis, the NF-kappaB responsive genes that protect hepatocytes are unknown. Our aim was to study the role of NF-kappaB activation and inducible nitric oxide synthases (iNOSs) in TNF-alpha- and Fas-mediated apoptosis in hepatocytes.

METHODS

Primary cultures of hepatocytes from wild-type and iNOS knockout mice were treated with TNF-alpha, the Fas agonistic antibody Jo2, a nitric oxide (NO) donor (S-nitroso-N-acetylpenicillamine), an NO inhibitor (N(G)-methyl-L-arginine acetate), and/or adenovirus-expressing NF-kappaB inhibitors.

RESULTS

The IkappaB superrepressor and a dominant-negative form of IkappaB kinase beta (IKKbeta) inhibited NF-kappaB binding activity by TNF-alpha or Jo2 and sensitized hepatocytes to TNF-alpha- and Jo2-mediated apoptosis. TNF-alpha and Jo2 induced iNOS messenger RNA and protein levels through the induction of NF-kappaB. S-nitroso-N-acetylpenicillamine inhibited Bid cleavage, the mitochondrial permeability transition, cytochrome c release, and caspase-8 and -3 activity, and reduced TNF-alpha- and Fas-mediated death in hepatocytes expressing IkappaB superrepressor. N(G)-methyl-L-arginine acetate partially sensitized hepatocytes to TNF-alpha- and Fas-mediated cell killing. TNF-alpha alone or Jo2 alone induced moderate cell death in hepatocytes from iNOS(-)/(-) mice.

CONCLUSIONS

NO protects hepatocytes from TNF-alpha- and Fas-mediated apoptosis. Endogenous iNOS, which is activated by NF-kappaB via IKKbeta, provides partial protection from apoptosis.

Differential role of I kappa B kinase 1 and 2 in primary rat hepatocytes

Nuclear factor-kappa B (NF-kappa B) protects hepatocytes from undergoing apoptosis during embryonic development and during liver regeneration. Activation of NF-kappa B is mediated through phosphorylation of its inhibitor, I kappa B, by a kinase complex that contains 2 I kappa B kinases. We analyzed the differential role of I kappa B kinase 1 (IKK1) and I kappa B kinase 2 (IKK2) in tumor necrosis factor alpha (TNF-alpha)- and interleukin-1 beta (IL-1 beta)-mediated NF-kappa B activation in primary rat hepatocytes. Maximal induction of IKK activity was observed 5 minutes after TNF-alpha and 15 minutes after IL-1 beta treatment, and activated IKK was able to phosphorylate GST-I kappa B (1-54) and GST-p65 (354-551), but not a GST-p65 (354-551) substrate with a serine-to-alanine substitution at position 536. Infection with an adenovirus containing catalytically inactive IKK2K44M (Ad5IKK2dn) completely blocked both TNF-alpha- and IL-1 beta-induced GST-I kappa B and GST-p65 phosphorylation, I kappa B degradation, and NF-kappa B DNA binding. Adenovirally transduced, catalytically inactive IKK1K44M (Ad5IKK1dn) reduced IKK activity and NF-kappa B DNA binding only slightly. Accordingly, Ad5IKK2dn induced apoptosis in 75% (+/-6%) of hepatocytes after 12 hours of TNF-alpha, which was accompanied by activation of caspases 3 and 8, nuclear fragmentation, and DNA laddering. In contrast, Ad5IKK1dn led to 21% (+/-2%) apoptosis in TNF-alpha-treated hepatocytes after 12 hours and comparatively low activity of caspases 3 and 8. Furthermore, Ad5IKK2dn completely blocked the induction of inducible nitric oxide synthase (iNOS), whereas Ad5IKK1dn had no influence on the expression of iNOS. Thus, IKK2 is the main mediator for cytokine-induced NF-kappa B activation in primary hepatocytes and protects against TNF-alpha-induced apoptosis, whereas IKK1 kinase activity is not required for NF-kappa B activation.

Inhibitors of NF-kappaB and AP-1 gene expression: SAR studies on the pyrimidine portion of 2-chloro-4-trifluoromethylpyrimidine-5-[N-(3', 5'-bis(trifluoromethyl)phenyl)carboxamide]

We investigated the structure-activity relationship studies of N-[3, 5-bis(trifluoromethyl)phenyl][2-chloro-4-(trifluoromethyl)pyrimidin-5 -yl]carboxamide (1), an inhibitor of transcription mediated by both NF-kappaB and AP-1 transcription factors, with the goal of improving its potential oral bioavailability. Compounds were examined for cell-based activity, were fit to Lipinski's rule of 5, and were examined for potential gastrointestinal permeability using the intestinal epithelial cell line, Caco-2. Selected groups were substituted at the 2-, 4-, and 5-positions of the pyrimidine ring using solution-phase combinatorial methodology. The introduction of a fluorine in the place of 2-chlorine of 1 resulted in a compound with comparable activity. However, other substitutions at the 2-position resulted in a loss of activity. The trifluoromethyl group at the 4-position could be replaced with a methyl, ethyl, chlorine, or phenyl without a substantial loss of activity. The carboxamide group at the 5-position is critical for activity. If it was moved to the 6-position, the activity was lost. The 2-methyl analogue of 1 (81) showed comparable in vitro activity and improved Caco-2 permeability compared to 1.

Novel inhibitors of AP-1 and NF-kappaB mediated gene expression: structure-activity relationship studies of ethyl 4-[(3-methyl-2,5-dioxo(3-pyrrolinyl))amino]-2-(trifluoromethyl)++ +pyrimidi ne-5-carboxylate

In an effort to identify novel inhibitors of AP-1 and NF-kappaB mediated transcriptional activation, several analogues of ethyl 4-[(3-methyl-2,5-dioxo(3-pyrrolinyl))amino]-2-(trifluoromethyl)pyr imidine-5-carboxylate (1) were synthesized and tested in two in vitro assays. The 2-(2'-thienyl) substituted compound (11) was identified as the most potent in this series.

The effect of a T cell-specific NF-kappa B inhibitor on in vitro cytokine production and collagen-induced arthritis

NF-kappa B plays a key role in the production of cytokines in inflammatory diseases. The effects of a novel T cell-specific NF-kappa B inhibitor, SP100030, were evaluated in cultured Jurkat cells and in murine collagen-induced arthritis (CIA). Chemical libraries were screened for NF-kappa B-inhibitory activity. SP100030, a compound identified in this process, inhibited NF-kappa B activation in PMA/PHA-activated Jurkat cells by EMSA at a concentration of 1 microM. Jurkat cells and the monocytic cell line THP-1 were transfected with an NF-kappa B promotor/luciferase construct and activated. SP100030 inhibited luciferase production in the Jurkat cells (IC50 = 30 nM). ELISA and RT-PCR confirmed that IL-2, IL-8, and TNF-alpha production by activated Jurkat and other T cell lines were inhibited by SP100030. However, cytokine expression was not blocked by the compound in THP-1 cells, fibroblasts, endothelial cells, or epithelial cells. Subsequently, DBA/1J mice were immunized with type II collagen. Treatment with SP100030 (10 mg/kg/day i.p. beginning on day 21) significantly decreased arthritis severity from onset of clinical signs to the end of the study on day 34 (arthritis score, 5.6 +/- 1.7 for SP100030 and 9.8 +/- 1.5 for control; p < 0.001). Histologic evaluation demonstrated a trend toward improvement in SP100030-treated animals. EMSA of arthritic mouse ankles in CIA showed that synovial NF-kappa B binding was suppressed in the SP100030-treated mice. SP100030 inhibits NF-kappa B activation in T cells, resulting in reduced NF-kappa B-regulated gene expression and decreased CIA. Its selectivity for T cells could provide potent immunosuppression with less toxicity than other NF-kappa B inhibitors.

Primary human CD4+ T cells contain heterogeneous I kappa B kinase complexes: role in activation of the IL-2 promoter

NF-kappa B transcription factors play an important role in the activation of the IL-2 gene in response to TCR ligation. The release of NF-kappa B factors to the nucleus requires phosphorylation and degradation of the inhibitory kappa-B proteins (I kappa Bs). I kappa B alpha and I kappa B beta phosphorylation is dependent on dual signaling by the TCR and the CD28 accessory receptor. This pathway involves a multisubunit I kappa B kinase (IKK) complex, which includes the IKK alpha (IKK-1) and IKK beta (IKK-2) kinases. We demonstrate that stimulation of primary human CD4+ T cells by CD3/CD28 activates two distinct endogenous IKK complexes, a heterodimeric IKK alpha/beta and a homodimeric IKK beta complex. IKK beta overexpression in a Jurkat cell line resulted in the formation of a constitutively active IKK complex, which was CD3/CD28 inducible. In contrast, ectopic expression of IKK alpha assembled into a complex with negligible I kappa B kinase activity. Moreover, IKK beta, but not IKK alpha, overexpression enhanced transcriptional activation of the CD28 response element in the IL-2 promoter. Conversely, only kinase-inactive IKK beta interfered in the activation of the IL-2 promoter. Sodium salicylate, an inhibitor of IKK beta, but not IKK alpha, activity, inhibited IL-2 promoter activation as well as IL-2 secretion and interfered in activation of both the heterodimeric as well as the homodimeric IKK complexes in primary CD4+ T cells. Taken together, these data demonstrate the presence of an IKK beta-mediated signaling pathway that is activated by TCR and CD28 coligation and regulates IL-2 promoter activity.

Primary Human CD4+ T Cells Contain Heterogeneous IκB Kinase Complexes: Role in Activation of the IL-2 Promoter

NF-κB transcription factors play an important role in the activation of the IL-2 gene in response to TCR ligation. The release of NF-κB factors to the nucleus requires phosphorylation and degradation of the inhibitory κ-B proteins (IκBs). IκBα and IκBβ phosphorylation is dependent on dual signaling by the TCR and the CD28 accessory receptor. This pathway involves a multisubunit IκB kinase (IKK) complex, which includes the IKKα (IKK-1) and IKKβ (IKK-2) kinases. We demonstrate that stimulation of primary human CD4+ T cells by CD3/CD28 activates two distinct endogenous IKK complexes, a heterodimeric IKKα/β and a homodimeric IKKβ complex. IKKβ overexpression in a Jurkat cell line resulted in the formation of a constitutively active IKK complex, which was CD3/CD28 inducible. In contrast, ectopic expression of IKKα assembled into a complex with negligible IκB kinase activity. Moreover, IKKβ, but not IKKα, overexpression enhanced transcriptional activation of the CD28 response element in the IL-2 promoter. Conversely, only kinase-inactive IKKβ interfered in the activation of the IL-2 promoter. Sodium salicylate, an inhibitor of IKKβ, but not IKKα, activity, inhibited IL-2 promoter activation as well as IL-2 secretion and interfered in activation of both the heterodimeric as well as the homodimeric IKK complexes in primary CD4+ T cells. Taken together, these data demonstrate the presence of an IKKβ-mediated signaling pathway that is activated by TCR and CD28 coligation and regulates IL-2 promoter activity.

NF-kappaB as a primary regulator of the stress response

A myriad of unrelated exogenous or endogenous agents that represent a threat to the organism are capable of inducing NF-kappaB activity, including viral infection, bacterial lipids, DNA damage, oxidative stress and chemotherapuetic agents. Likewise, NF-kappaB regulates the expression of an equally diverse array of cellular genes. These findings are indicative of the widespread significance of NF-kappaB as a mediator of cellular stress. Remarkably, the NF-kappaB pathway displays the capacity to activate, in a cell- and stimulus-specific manner, only a subset of the total repertoire of NF-kappaB-responsive genes. The seemingly promiscuous nature of NF-kappaB activation poses a regulatory quagmire as to how specificity is achieved at the level of gene expression. The review will summarize recent findings and explore how they further our understanding of the mechanism by which stimulus-specific activation of NF-kappaB is achieved in response to cellular stress.

Jun N-terminal kinase in rheumatoid arthritis

Potential mechanisms of joint destruction in rheumatoid arthritis (RA) were examined by studying the regulation of mitogen-activated protein kinases and collagenase gene expression in fibroblast-like synoviocytes (FLS). The three main mitogen-activated protein kinase families [p38, Jun N-terminal kinase (JNK), and extracellular signal-regulated kinases (ERKs)] were constitutively expressed in RA and osteoarthritis (OA) FLS. p38 and ERK1/2 were readily phosphorylated in both RA and OA FLS after interleukin-1 (IL-1) stimulation. JNK was phosphorylated in RA FLS but not OA FLS after IL-1 stimulation. Reverse transcription-polymerase chain reaction studies suggested that JNK2 is the major isoform of the JNK family expressed by FLS. Northern blot analysis of collagenase gene expression demonstrated that RA FLS contained significantly more collagenase mRNA than OA FLS after IL-1 stimulation. The roles of JNK and p38 kinase were evaluated with the p38/JNK inhibitor SB 203580. Low concentrations of SB 203580 (1 microM, a concentration that only inhibits p38) had no significant effect on IL-1-induced collagenase expression in RA FLS whereas 25 microM (which inhibits p38, JNK2, and c-raf) blocked collagenase mRNA accumulation. IL-1-stimulated AP-1 binding was also inhibited by 25 microM SB 203580 in RA FLS. These studies suggest that OA and RA FLS have a different pattern of JNK phosphorylation, which might lead to enhanced collagenase gene expression in RA.

New targets for anti-inflammatory drugs

Inflammatory and autoimmune diseases, including rheumatoid arthritis, inflammatory bowel diseases, multiple sclerosis, psoriasis and asthma, provide drug discoverers with a tremendous challenge. The precise causes of these diseases are not known, but our understanding of the molecular and cellular mechanisms associated with inflammatory diseases has increased dramatically. As a consequence, a wide array of gene targets have emerged that control cell influx and activation, inflammatory mediator release and activity, and tissue proliferation and degradation. Since multiple gene products have been identified at the sites of inflammation, there has been a surge of interest in identifying intracellular signaling targets, including transcription factors that control inflammatory gene expression and which are amenable to drug discovery.

NF-κB Regulation by IκB Kinase in Primary Fibroblast-Like Synoviocytes

NF-κB is a key regulator of inflammatory gene transcription and is activated in the rheumatoid arthritis (RA) synovium. In resting cells, NF-κB is retained as an inactive cytoplasmic complex by its inhibitor, IκB. Phosphorylation of IκB targets it for proteolytic degradation, thereby releasing NF-κB for nuclear translocation. Recently, two related IκB kinases (IKK-1 and IKK-2) were identified in immortalized cell lines that regulate NF-κB activation by initiating IκB degradation. To determine whether IKK regulates NF-κB in primary cells isolated from a site of human disease, we characterized IKK in cultured fibroblast-like synoviocytes (FLS) isolated from synovium of patients with RA or osteoarthritis. Immunoreactive IKK protein was found to be abundant in both RA and osteoarthritis FLS by Western blot analysis. Northern blot analysis showed that IKK-1 and IKK-2 genes were constitutively expressed in all FLS lines. IKK function in FLS extracts was determined by measuring phosphorylation of recombinant IκB in vitro. IKK activity in both RA and osteoarthritis FLS was strongly induced by TNF-α and IL-1 in a concentration-dependent manner. Activity was significantly increased within 10 min of stimulation and declined to near basal levels within 80 min. Activation of IKK in FLS was accompanied by phosphorylation and degradation of endogenous IκBα as determined by Western blot analysis. Concomitant activation and nuclear translocation of NF-κB was documented by EMSA and immunohistochemistry. Transfection with a dominant negative IKK-2 mutant prevented TNF-α-mediated NF-κB nuclear translocation, whereas a dominant negative IKK-1 mutant had no effect. This is the first demonstration that IKK-2 is a pivotal regulator of NF-κB in primary human cells.

NF-kappa B regulation by I kappa B kinase in primary fibroblast-like synoviocytes

NF-kappa B is a key regulator of inflammatory gene transcription and is activated in the rheumatoid arthritis (RA) synovium. In resting cells, NF-kappa B is retained as an inactive cytoplasmic complex by its inhibitor, I kappa B. Phosphorylation of I kappa B targets it for proteolytic degradation, thereby releasing NF-kappa B for nuclear translocation. Recently, two related I kappa B kinases (IKK-1 and IKK-2) were identified in immortalized cell lines that regulate NF-kappa B activation by initiating I kappa B degradation. To determine whether IKK regulates NF-kappa B in primary cells isolated from a site of human disease, we characterized IKK in cultured fibroblast-like synoviocytes (FLS) isolated from synovium of patients with RA or osteoarthritis. Immunoreactive IKK protein was found to be abundant in both RA and osteoarthritis FLS by Western blot analysis. Northern blot analysis showed that IKK-1 and IKK-2 genes were constitutively expressed in all FLS lines. IKK function in FLS extracts was determined by measuring phosphorylation of recombinant I kappa B in vitro. IKK activity in both RA and osteoarthritis FLS was strongly induced by TNF-alpha and IL-1 in a concentration-dependent manner. Activity was significantly increased within 10 min of stimulation and declined to near basal levels within 80 min. Activation of IKK in FLS was accompanied by phosphorylation and degradation of endogenous I kappa B alpha as determined by Western blot analysis. Concomitant activation and nuclear translocation of NF-kappa B was documented by EMSA and immunohistochemistry. Transfection with a dominant negative IKK-2 mutant prevented TNF-alpha-mediated NF-kappa B nuclear translocation, whereas a dominant negative IKK-1 mutant had no effect. This is the first demonstration that IKK-2 is a pivotal regulator of NF-kappa B in primary human cells.

Multiple signals converging on NF-kappaB

The recent identification of molecular components of the signal transduction pathway regulating activation of nuclear factor-kappaB (NF-kappaB) in response to cytokines such as tumor necrosis factor alpha and interleukin-1beta allows the evaluation of how other diverse stimuli impinge on the NF-kappaB activation pathway. These studies suggest a basis for specificity in activation of specific Rel-related family members and the genetic responses they promote.

IkappaB kinase (IKK)-associated protein 1, a common component of the heterogeneous IKK complex

Activation of the transcription factor NF-kappaB is controlled by the sequential phosphorylation, ubiquitination, and degradation of its inhibitory subunit, IkappaB. We recently purified a large multiprotein complex, the IkappaB kinase (IKK) signalsome, which contains two regulated IkappaB kinases, IKK1 and IKK2, that can each phosphorylate IkappaBalpha and IkappaBbeta. The IKK signalsome contains several additional proteins presumably required for the regulation of the NFkappaB signal transduction cascade in vivo. In this report, we demonstrate reconstitution of IkappaB kinase activity in vitro by using purified recombinant IKK1 and IKK2. Recombinant IKK1 or IKK2 forms homo- or heterodimers, suggesting the possibility that similar IKK complexes exist in vivo. Indeed, in HeLa cells we identified two distinct IKK complexes, one containing IKK1-IKK2 heterodimers and the other containing IKK2 homodimers, which display differing levels of activation following tumor necrosis factor alpha stimulation. To better elucidate the nature of the IKK signalsome, we set out to identify IKK-associated proteins. To this end, we purified and cloned a novel component common to both complexes, named IKK-associated protein 1 (IKKAP1). In vitro, IKKAP1 associated specifically with IKK2 but not IKK1. Functional analyses revealed that binding to IKK2 requires sequences contained within the N-terminal domain of IKKAP1. Mutant versions of IKKAP1, which either lack the N-terminal IKK2-binding domain or contain only the IKK2-binding domain, disrupt the NF-kappaB signal transduction pathway. IKKAP1 therefore appears to mediate an essential step of the NF-kappaB signal transduction cascade. Heterogeneity of IKK complexes in vivo may provide a mechanism for differential regulation of NF-kappaB activation.

AP-1 and NF-kappaB regulation in rheumatoid arthritis and murine collagen-induced arthritis

OBJECTIVE

To determine the expression and regulation of nuclear transcription factors AP-1 and NF-kappaB in rheumatoid arthritis and in collagen-induced arthritis in mice.

METHODS

AP-1 and NF-kappaB expression and function were determined in RA, OA and normal synovial tissue by electrophoretic mobility shift assay (EMSA) and immunohistochemistry. The kinetics of transcription factor expression were then examined in collagen-induced arthritis (CIA) in mice. EMSAs were performed with the nuclear extracts obtained from paws of CIA mice from 10 to 45d after immunization to determine AP-1 and NF-kappaB binding activity. The expression of collagenase-3 (MMP13) and stromelysin (MMP3) mRNA was examined by northern blot analysis.

RESULTS

Immunohistochemistry showed that NF-kappaB expression was increased in both RA and OA synovial intimal lining. AP-1 components Jun and Fos were also present in the intimal lining and was significantly greater in RA than OA. The DNA binding activities of both AP-1 and NF-kappaB were significantly higher RA patients compared with OA. In CIA, AP-1 and NF-kappaB expression increased by day 20, which was 1-2 weeks before onset of clinical arthritis. However, collagenase and stromelysin gene expression did not increase until day 35.

CONCLUSION

The DNA binding activity of AP-1 and NF-kappaB are markedly increased in both CIA and RA. In CIA, activation of AP-1 and NF-kappaB precede both clinical arthritis and metalloproteinase gene expression. NF-kappaB expression correlated better than AP-1 with metalloproteinase expression.

Identification of the receptor component of the IkappaBalpha-ubiquitin ligase

NF-kappaB, a ubiquitous, inducible transcription factor involved in immune, inflammatory, stress and developmental processes, is retained in a latent form in the cytoplasm of non-stimulated cells by inhibitory molecules, IkappaBs. Its activation is a paradigm for a signal-transduction cascade that integrates an inducible kinase and the ubiquitin-proteasome system to eliminate inhibitory regulators. Here we isolate the pIkappaBalpha-ubiquitin ligase (pIkappaBalpha-E3) that attaches ubiquitin, a small protein which marks other proteins for degradation by the proteasome system, to the phosphorylated NF-kappaB inhibitor pIkappaBalpha. Taking advantage of its high affinity to pIkappaBalpha, we isolate this ligase from HeLa cells by single-step immunoaffinity purification. Using nanoelectrospray mass spectrometry, we identify the specific component of the ligase that recognizes the pIkappaBalpha degradation motif as an F-box/WD-domain protein belonging to a recently distinguished family of beta-TrCP/Slimb proteins. This component, which we denote E3RSIkappaB (pIkappaBalpha-E3 receptor subunit), binds specifically to pIkappaBalpha and promotes its in vitro ubiquitination in the presence of two other ubiquitin-system enzymes, E1 and UBC5C, one of many known E2 enzymes. An F-box-deletion mutant of E3RS(IkappaB), which tightly binds pIkappaBalpha but does not support its ubiquitination, acts in vivo as a dominant-negative molecule, inhibiting the degradation of pIkappaBalpha and consequently NF-kappaB activation. E3RS(IkappaB) represents a family of receptor proteins that are core components of a class of ubiquitin ligases. When these receptor components recognize their specific ligand, which is a conserved, phosphorylation-based sequence motif, they target regulatory proteins containing this motif for proteasomal degradation.

Role of IKK1 and IKK2 in lipopolysaccharide signaling in human monocytic cells

Mononuclear phagocytes play a major role in immune and inflammatory responses. Bacterial lipopolysaccharide (LPS) induces monocytes to express a variety of genes by activating the NF-kappaB/Rel transcription factor family. Recently, we have reported that the tumor necrosis factor and interleukin 1 signaling pathways activate two kinases, IKK1 and IKK2. Phosphorylation of the IkappaB cytoplasmic inhibitors, IkappaBalpha, IkappaBbeta, and IkappaBepsilon, by these kinases triggers proteolytic degradation and the release of NF-kappaB/Rel proteins into the nucleus. At present, the role of the IKKs in LPS signaling has not been investigated. Here, we report that LPS induces IKK activity in human monocytes and THP-1 monocytic cells. The kinetics of activation of kinase activity in monocytic cells are relatively slow with maximal activity observed at 60 min, which coincides with the degradation of IkappaBs and the nuclear translocation of NF-kappaB. In transfection experiments, overexpression of wild type IKK1, a dominant negative mutant IKK1 (K44M), or wild type IKK2 did not affect LPS-induced kappaB-dependent transcription in monocytic cells. In contrast, a dominant negative mutant of IKK2 inhibited LPS induction of kappaB-dependent transcription in a dose-dependent manner. These results indicate that LPS induction of kappaB-dependent gene expression in human monocytic cells requires activation of IKK2.

Selective inhibition of TNF-alpha induced cell adhesion molecule gene expression by tanapox virus

Poxviruses encode virulence factors that have been identified as proteins that are secreted from infected host cells. Some of these secretory proteins impede host immune defences. We have previously demonstrated that tanapox virus (TPV) infected cells secrete an early 38 kDa glycopeptide that binds to human (h) interferon-gamma, hIL-2, and hIL-5. We now show an additional activity in the supernatant from TPV infected cells that down-regulates the expression of tumour necrosis factor-alpha (TNF-alpha) induced cell adhesion molecule gene expression. This activity was not detected in mock infected cells. Enzyme linked immunosorbent assays (ELISA) on primary human endothelial cells, show the induction of E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) following TNF-alpha or IL-1 beta treatment, as expected. Supernatant from TPV infected cells significantly decreased the TNF-alpha but not IL-1 beta-induced expression of these molecules. Mobility shift assays and Northern blot analyses further show that the supernatant from TPV infected cells inhibited TNF-alpha-induced activation of the nuclear transcription factor-kappa B (NF-kappa B) and transcriptional activation of the E-selectin, VCAM-1 and ICAM-1 genes. Based on TNF-alpha affinity chromatography, this activity appears to be associated with a 38 kDa glycopeptide.

Inhibition of NF-kappa-B cellular function via specific targeting of the I-kappa-B-ubiquitin ligase

Activation of the transcription factor NF-kappa B is a paradigm for signal transduction through the ubiquitin-proteasome pathway: ubiquitin-dependent degradation of the transcriptional inhibitor I kappa B in response to cell stimulation. A major issue in this context is the nature of the recognition signal and the targeting enzyme involved in the proteolytic process. Here we show that following a stimulus-dependent phosphorylation, and while associated with NF-kappa B, I kappa B is targeted by a specific ubiquitin-ligase via direct recognition of the signal-dependent phosphorylation site; phosphopeptides corresponding to this site specifically inhibit ubiquitin conjugation of I kappa B and its subsequent degradation. The ligase recognition signal is functionally conserved between I kappa B alpha and I kappa B beta, and does not involve the nearby ubiquitination site. Microinjection of the inhibitory peptides into stimulated cells abolished NF-kappa B activation in response to TNF alpha and the consequent expression of E-selectin, an NF-kappa B-dependent cell-adhesion molecule. Inhibition of NF-kappa B function by specific blocking of ubiquitin ligase activity provides a novel approach for intervening in cellular processes via regulation of unique proteolytic events.