Metformin and 2-Deoxyglucose Collaboratively Suppress Human CD4+ T Cell Effector Functions and Activation-Induced Metabolic Reprogramming.

Metabolic reprogramming plays a central role in T cell activation and differentiation, and the inhibition of key metabolic pathways in activated T cells represents a logical approach for the development of new therapeutic agents for treating autoimmune diseases. The widely prescribed antidiabetic drug metformin and the glycolytic inhibitor 2-deoxyglucose (2-DG) have been used to study the inhibition of oxidative phosphorylation and glycolysis, respectively, in murine immune cells. Published studies have demonstrated that combination treatment with metformin and 2-DG was efficacious in dampening mouse T cell activation-induced effector processes, relative to treatments with either metformin or 2-DG alone. In this study, we report that metformin + 2-DG treatment more potently suppressed IFN-γ production and cell proliferation in activated primary human CD4+ T cells than either metformin or 2-DG treatment alone. The effects of metformin + 2-DG on human T cells were accompanied by significant remodeling of activation-induced metabolic transcriptional programs, in part because of suppression of key transcriptional regulators MYC and HIF-1A. Accordingly, metformin + 2-DG treatment significantly suppressed MYC-dependent metabolic genes and processes, but this effect was found to be independent of mTORC1 signaling. These findings reveal significant insights into the effects of metabolic inhibition by metformin + 2-DG treatment on primary human T cells and provide a basis for future work aimed at developing new combination therapy regimens that target multiple pathways within the metabolic networks of activated human T cells.

Innate immune recognition of an AT-rich stem-loop DNA motif in the Plasmodium falciparum genome.

Although Toll-like receptor 9 (TLR9) has been implicated in cytokine and type I interferon (IFN) production during malaria in humans and mice, the high AT content of the Plasmodium falciparum genome prompted us to examine the possibility that malarial DNA triggered TLR9-independent pathways. Over 6000 ATTTTTAC ("AT-rich") motifs are present in the genome of P. falciparum, which we show here potently induce type I IFNs. Parasite DNA, parasitized erythrocytes and oligonucleotides containing the AT-rich motif induce type I IFNs via a pathway that did not involve the previously described sensors TLR9, DAI, RNA polymerase-III or IFI16/p204. Rather, AT-rich DNA sensing involved an unknown receptor that coupled to the STING, TBK1 and IRF3-IRF7 signaling pathway. Mice lacking IRF3, IRF7, the kinase TBK1 or the type I IFN receptor were resistant to otherwise lethal cerebral malaria. Collectively, these observations implicate AT-rich DNA sensing via STING, TBK1 and IRF3-IRF7 in P. falciparum malaria.

Efficacy and Pharmacology of the NLRP3 Inflammasome Inhibitor CP-456,773 (CRID3) in Murine Models of Dermal and Pulmonary Inflammation.

A critical component of innate immune response to infection and tissue damage is the NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome, and this pathway and its activation products have been implicated in the pathophysiology of a variety of diseases. NLRP3 inflammasome activation leads to the cleavage of pro-IL-1ß and pro-IL-18, as well as the subsequent release of biologically active IL-1ß, IL-18, and other soluble mediators of inflammation. In this study, we further define the pharmacology of the previously reported NLRP3 inflammasome-selective, IL-1ß processing inhibitor CP-456,773 (also known as MCC950), and we demonstrate its efficacy in two in vivo models of inflammation. Specifically, we show that in human and mouse innate immune cells CP-456,773 is an inhibitor of the cellular release of IL-1ß, IL-1α, and IL-18, that CP-456,773 prevents inflammasome activation induced by disease-relevant soluble and crystalline NLRP3 stimuli, and that CP-456,773 inhibits R848- and imiquimod-induced IL-1ß release. In mice, CP-456,773 demonstrates potent inhibition of the release of proinflammatory cytokines following acute i.p. challenge with LPS plus ATP in a manner that is proportional to the free/unbound concentrations of the drug, thereby establishing an in vivo pharmacokinetic/pharmacodynamic model for CP-456,773. Furthermore, CP-456,773 reduces ear swelling in an imiquimod cream-induced mouse model of skin inflammation, and it reduces airway inflammation in mice following acute challenge with house dust mite extract. These data implicate the NLRP3 inflammasome in the pathogenesis of dermal and airway inflammation, and they highlight the utility of CP-456,773 for interrogating the contribution of the NLRP3 inflammasome and its outputs in preclinical models of inflammation and disease.

An NLRP3-specific inflammasome inhibitor attenuates crystal-induced kidney fibrosis in mice.

Intrarenal crystal formation activates the Nlrp3 inflammasome in myeloid cells and triggers a profound inflammatory response. Here, we studied whether a specific inhibitor of the Nlrp3 inflammasome, CP-456,773, can prevent kidney fibrosis in a murine model of crystal nephropathy induced by diets rich in oxalate or adenine. Inflammasome activation in renal dendritic cells and the resulting interleukin (IL)-1ß and IL-18 production were markedly reduced by CP-456,773 treatment both ex vivo and in vivo. We directly visualized intrarenal inflammasome activation and its inhibition by CP-456,773 in vivo by adoptive transfer of bone marrow cells transduced with interleukin-1ß-Gaussia luciferase, a proteolytic luciferase-based reporter for inflammasome activation, into irradiated mice. CP-456,773 treatment strongly attenuated kidney fibrosis when given early in the genesis of crystal nephropathy, but was unable to reverse established crystal-induced fibrosis. The urinary IL-18 concentration appeared to be a useful noninvasive biomarker for renal inflammasome activation. Finally, NLRP3 inhibition did not compromise adaptive immune responses as previously reported for the global inhibition of IL-1 signaling. Thus, early NLRP3 inhibition by CP-456,773 may be an effective treatment for crystal nephropathy. Use of iGLuc transfected cells introduces a novel imaging technique for inflammasome activation in mice.

TRIL is involved in cytokine production in the brain following Escherichia coli infection.

TLR4 interactor with leucine-rich repeats (TRIL) is a brain-enriched accessory protein that is important in TLR3 and TLR4 signaling. In this study, we generated Tril(-/-) mice and examined TLR responses in vitro and in vivo. We found a role for TRIL in both TLR4 and TLR3 signaling in mixed glial cells, consistent with the high level of expression of TRIL in these cells. We also found that TRIL is a modulator of the innate immune response to LPS challenge and Escherichia coli infection in vivo. Tril(-/-) mice produce lower levels of multiple proinflammatory cytokines and chemokines specifically within the brain after E. coli and LPS challenge. Collectively, these data uncover TRIL as a mediator of innate immune responses within the brain, where it enhances neuronal cytokine responses to infection.

Human Recombinant Alkaline Phosphatase (Ilofotase Alfa) Protects Against Kidney Ischemia-Reperfusion Injury in Mice and Rats Through Adenosine Receptors.

Adenosine triphosphate (ATP) released from injured or dying cells is a potent pro-inflammatory "danger" signal. Alkaline phosphatase (AP), an endogenous enzyme that de-phosphorylates extracellular ATP, likely plays an anti-inflammatory role in immune responses. We hypothesized that ilofotase alfa, a human recombinant AP, protects kidneys from ischemia-reperfusion injury (IRI), a model of acute kidney injury (AKI), by metabolizing extracellular ATP to adenosine, which is known to activate adenosine receptors. Ilofotase alfa (iv) with or without ZM241,385 (sc), a selective adenosine A2A receptor (A2AR) antagonist, was administered 1 h before bilateral IRI in WT, A2AR KO (Adora2a-/- ) or CD73-/- mice. In additional studies recombinant alkaline phosphatase was given after IRI. In an AKI-on-chronic kidney disease (CKD) ischemic rat model, ilofotase alfa was given after the three instances of IRI and rats were followed for 56 days. Ilofotase alfa in a dose dependent manner decreased IRI in WT mice, an effect prevented by ZM241,385 and partially prevented in Adora2a-/- mice. Enzymatically inactive ilofotase alfa was not protective. Ilofotase alfa rescued CD73-/- mice, which lack a 5'-ectonucleotidase that dephosphorylates AMP to adenosine; ZM241,385 inhibited that protection. In both rats and mice ilofotase alfa ameliorated IRI when administered after injury, thus providing relevance for therapeutic dosing of ilofotase alfa following established AKI. In an AKI-on-CKD ischemic rat model, ilofotase alfa given after the third instance of IRI reduced injury. These results suggest that ilofotase alfa promotes production of adenosine from liberated ATP in injured kidney tissue, thereby amplifying endogenous mechanisms that can reverse tissue injury, in part through A2AR-and non-A2AR-dependent signaling pathways.

Identification and SAR of a new series of thieno[3,2-d]pyrimidines as Tpl2 kinase inhibitors.

We report here the synthesis and SAR of a new series of thieno[3,2-d]pyrimidines as potent Tpl2 kinase inhibitors. The proposed binding mode suggests the potential flipped binding mode depending on the substitution. Biacore studies show evidence of binding of these molecules to the protein kinase. The kinome inhibition profile of these molecules suggests good selectivity.

Discovery of indazoles as inhibitors of Tpl2 kinase.

Synthesis, modeling and structure-activity relationship of indazoles as inhibitors of Tpl2 kinase are described. From a high throughput screening effort, we identified an indazole hit compound 5 that has a single digit micromolar Tpl2 activity. Through SAR modifications at the C3 and C5 positions of the indazole, we discovered compound 31 with good potency in LANCE assay and cell-based p-Erk assay.

TREM-1 expression is increased in the synovium of rheumatoid arthritis patients and induces the expression of pro-inflammatory cytokines.

OBJECTIVES: To investigate the expression and function of triggering receptor expressed on myeloid cells-1 (TREM-1) in the synovium of human RA patients as well as the level of soluble TREM-1 in the plasma of RA patients. METHODS: Twenty-four RA synovial samples were analysed by gene expression oligonucleotide microarrays. Expression levels of TREM-1 mRNA in murine CIA paws were determined by quantitative PCR (qPCR). TREM-1 protein expression was detected by immunohistochemistry in five RA synovial samples and two OA synovial samples. TREM-1-positive cells from five RA synovial tissues were analysed by FACS staining to determine the cell type. Activation of TREM-1 was tested in five RA synovial samples. Soluble TREM-1 was measured in serum from 32 RA patients. RESULTS: The expression of TREM-1 mRNA was found to increase 6.5-fold in RA synovial samples, whereas it was increased 132-fold in CIA paws. Increased numbers of TREM-1-positive cells were seen in RA synovium sections and these cells co-expressed CD14. Using a TREM-1-activating cross-linking antibody in RA synovial cultures, multiple pro-inflammatory cytokines were induced. The average amount of soluble TREM-1 in plasma from RA patients was found to be higher than that in plasma from healthy volunteers. CONCLUSIONS: These findings suggest that the presence of high levels of functionally active TREM-1 in RA synovium may contribute to the development or maintenance of RA, or both. Inhibiting TREM-1 activity may, therefore, have a therapeutic effect on RA. High levels of soluble TREM-1 in the plasma of RA patients compared with healthy volunteers may indicate disease activity.

Optimized protocols for studying the NLRP3 inflammasome and assessment of potential targets of CP-453,773 in undifferentiated THP1 cells.

The NLRP3 inflammasome is a complex multimeric signaling apparatus that regulates production of the pro-inflammatory cytokine IL-1ß. To overcome both the variability among primary immune cells and the limitations of genetic manipulation of differentiated human or murine macrophages, we developed a simplified, reliable and relevant cell-based model for studying the NLRP3 inflammasome using the undifferentiated human myelomonocytic cell line THP1. Undifferentiated THP1 cells constitutively express NLRP3, and NLRP3 inflammasome activation occurred in response to canonical NLRP3 activation stimuli including nigericin, ATP, and urea crystals, culminating in pro-IL-1ß cleavage, extracellular release of mature IL-1ß, and pyroptosis. We used this THP1 cell system to investigate potential targets of the potent, NLRP3 inflammasome selective inhibitor CP-456,773. We optimized a viral shRNA transduction method for gene expression knockdown (KD), and the KD of NLRP3 itself eliminated inflammasome activation and IL-1ß production. NLRP3 inflammasome activation and CP-453,773 pharmacology were not altered in ABCb7- or ABCb10-deficient THP1 cells, eliminating these gene products as candidate pharmacological targets of CP-453,773. For ABCb10, we confirmed our results using CRISPR/CAS9-mediated ABCb10 knockout (KO) THP1 sub-lines. In summary, undifferentiated THP1 cells are fully competent for activation of the NLRP3 inflammasome and production of IL-1ß, without differentiation into macrophages, and we describe optimized KD and KO methodologies to manipulate gene expression in these cells. As an example of the utility of undifferentiated THP1 cells for investigations into the biology of the NLRP3 inflammasome, we have used this cell system to rule out ABCb7 and ABCb10 as potential targets of the NLRP3 inflammasome inhibitor CP-453,773.

Inhibitors of tumor progression loci-2 (Tpl2) kinase and tumor necrosis factor alpha (TNF-alpha) production: selectivity and in vivo antiinflammatory activity of novel 8-substituted-4-anilino-6-aminoquinoline-3-carbonitriles.

Tumor progression loci-2 (Tpl2) (Cot/MAP3K8) is a serine/threonine kinase in the MAP3K family directly upstream of MEK. Recent studies using Tpl2 knockout mice have indicated an important role for Tpl2 in the lipopolysaccharide (LPS) induced production of tumor necrosis factor alpha (TNF-alpha) and other proinflammatory cytokines involved in diseases such as rheumatoid arthritis. Initial 4-anilino-6-aminoquinoline-3-carbonitrile leads showed poor selectivity for Tpl2 over epidermal growth factor receptor (EGFR) kinase. Using molecular modeling and crystallographic data of the EGFR kinase domain with and without an EGFR kinase-specific 4-anilinoquinazoline inhibitor (erlotinib, Tarceva), we hypothesized that we could diminish the inhibition of EGFR kinase by substitution at the C-8 position of our 4-anilino-6-aminoquinoline-3-carbonitrile leads. The 8-substituted-4-anilino-6-aminoquinoline-3-carbonitriles were prepared from the appropriate 2-substituted 4-nitroanilines. Modifications to the C-6 and C-8 positions led to the identification of compounds with increased inhibition of TNF-alpha release from LPS-stimulated rat and human blood, and these analogues were also highly selective for Tpl2 kinase over EGFR kinase. Further structure-activity based modifications led to the identification of 8-bromo-4-(3-chloro-4-fluorophenylamino)-6-[(1-methyl-1H-imidazol-4-yl)methylamino]quinoline-3-carbonitrile, which demonstrated in vitro as well as in vivo efficacy in inhibition of LPS-induced TNF-alpha production.

A rat pharmacokinetic/pharmacodynamic model for assessment of lipopolysaccharide-induced tumor necrosis factor-alpha production.

INTRODUCTION: Tumor necrosis factor-alpha (TNFalpha) participates in many inflammatory processes. TNFalpha modulators show beneficial effects for the treatment of many diseases including rheumatoid arthritis. The purpose of this study was to validate a rat pharmacokinetic/pharmacodynamic (PK/PD) model for rapid assessment of drug candidates that intended to interrupt TNFalpha synthesis or release. METHODS: Rats received intravenous (IV) or oral administrations of test article or dose vehicle, followed by LPS challenge. Plasma levels of test article and TNFalpha were determined. The areas under the concentration-time curves (AUC(drug) and AUC(TNFalpha)) were calculated. The overall percentage of inhibition on TNFalpha release in vivo was calculated by comparing AUC(TNFalpha) of the test article treated group against that for the vehicle control group. RESULTS: The dosing vehicles tested in this study did not increase plasma TNFalpha level. At IV dose of up to 100 microg/kg, LPS did not alter the pharmacokinetics of the compound tested. Using a selective TNFalpha converting enzyme (TACE) inhibitor as model compound, this PK/PD model demonstrated its ability to correlate plasma test article concentration with its biological activity of lowering the LPS-induced TNFalpha plasma levels in vivo. DISCUSSION: A rat PK/PD model for evaluation of the effect of drug candidates on LPS-induced TNFalpha synthesis and/or release has been investigated. This model provides integrated information on pharmacokinetics and in vivo potency of the test articles.

Stimulation of TLR4 by recombinant HSP70 requires structural integrity of the HSP70 protein itself.

BACKGROUND: Toll-like receptor 4 (TLR4) is activated by bacterial endotoxin, a prototypical pathogen-associated molecular pattern (PAMP). It has been suggested that TLR4 can also be activated by damage-associated molecular pattern (DAMP) proteins such as HSP70. It remains a challenge to provide unequivocal evidence that DAMP proteins themselves play a role in TLR4 activation, as the DAMP proteins used are often contaminated with endotoxin and other TLR ligands introduced during protein expression and/or purification. RESULTS: Here we report that the activation of TLR4 on primary human macrophage cultures by recombinant HSP70 is not solely due to contaminating endotoxin. Polymyxin B pretreatment of HSP70 preparations to neutralize contaminating endotoxin caused significant reductions in the amount of TNF-α induced by the recombinant protein as determined by ELISA. However, digestion of HSP70 with Proteinase K-agarose beads also dramatically reduced the TNF-α response of macrophages to HSP70, while leaving levels of contaminating endotoxin largely unchanged relative to controls. CONCLUSIONS: These results indicate that the stimulatory effect of recombinant HSP70 requires both the presence of endotoxin and structural integrity of the heat shock protein itself.

Mice lacking Tbk1 activity exhibit immune cell infiltrates in multiple tissues and increased susceptibility to LPS-induced lethality.

TBK1 is critical for immunity against microbial pathogens that activate TLR4- and TLR3-dependent signaling pathways. To address the role of TBK1 in inflammation, mice were generated that harbor two copies of a mutant Tbk1 allele. This Tbk1(Δ) allele encodes a truncated Tbk1(Δ) protein that is catalytically inactive and expressed at very low levels. Upon LPS stimulation, macrophages from Tbk1(Δ/Δ) mice produce normal levels of proinflammatory cytokines (e.g., TNF-α), but IFN-ß and RANTES expression and IRF3 DNA-binding activity are ablated. Three-month-old Tbk1(Δ/Δ) mice exhibit mononuclear and granulomatous cell infiltrates in multiple organs and inflammatory cell infiltrates in their skin, and they harbor a 2-fold greater amount of circulating monocytes than their Tbk1(+/+) and Tbk1(+/Δ) littermates. Skin from 2-week-old Tbk1(Δ/Δ) mice is characterized by reactive changes, including hyperkeratosis, hyperplasia, necrosis, inflammatory cell infiltrates, and edema. In response to LPS challenge, 3-month-old Tbk1(Δ/Δ) mice die more quickly and in greater numbers than their Tbk1(+/+) and Tbk1(+/Δ) counterparts. This lethality is accompanied by an overproduction of several proinflammatory cytokines in the serum of Tbk1(Δ/Δ) mice, including TNF-α, GM-CSF, IL-6, and KC. This overproduction of serum cytokines in Tbk1(Δ/Δ) mice following LPS challenge and their increased susceptibility to LPS-induced lethality may result from the reactions of their larger circulating monocyte compartment and their greater numbers of extravasated immune cells.

Identification of a novel class of selective Tpl2 kinase inhibitors: 4-Alkylamino-[1,7]naphthyridine-3-carbonitriles.

We have previously reported the discovery and initial SAR of the [1,7]naphthyridine-3-carbonitriles and quinoline-3-carbonitriles as Tumor Progression Loci-2 (Tpl2) kinase inhibitors. In this paper, we report new SAR efforts which have led to the identification of 4-alkylamino-[1,7]naphthyridine-3-carbonitriles. These compounds show good in vitro and in vivo activity against Tpl2 and improved pharmacokinetic properties. In addition they are highly selective for Tpl2 kinase over other kinases, for example, EGFR, MEK, MK2, and p38. Lead compound 4-cycloheptylamino-6-[(pyridin-3-ylmethyl)-amino]-[1,7]naphthyridine-3-carbonitrile (30) was efficacious in a rat model of LPS-induced TNF-alpha production.

Pharmacologic inhibition of tpl2 blocks inflammatory responses in primary human monocytes, synoviocytes, and blood.

Tumor necrosis factor alpha (TNFalpha) is a pro-inflammatory cytokine that controls the initiation and progression of inflammatory diseases such as rheumatoid arthritis. Tpl2 is a MAPKKK in the MAPK (i.e. ERK) pathway, and the Tpl2-MEK-ERK signaling pathway is activated by the pro-inflammatory mediators TNFalpha, interleukin (IL)-1beta, and bacterial endotoxin (lipopolysaccharide (LPS)). Moreover, Tpl2 is required for TNFalpha expression. Thus, pharmacologic inhibition of Tpl2 should be a valid approach to therapeutic intervention in the pathogenesis of rheumatoid arthritis and other inflammatory diseases in humans. We have developed a series of highly selective and potent Tpl2 inhibitors, and in the present study we have used these inhibitors to demonstrate that the catalytic activity of Tpl2 is required for the LPS-induced activation of MEK and ERK in primary human monocytes. These inhibitors selectively target Tpl2 in these cells, and they block LPS- and IL-1beta-induced TNFalpha production in both primary human monocytes and human blood. In rheumatoid arthritis fibroblast-like synoviocytes these inhibitors block ERK activation, cyclooxygenase-2 expression, and the production of IL-6, IL-8, and prostaglandin E(2), and the matrix metalloproteinases MMP-1 and MMP-3. Taken together, our results show that inhibition of Tpl2 in primary human cell types can decrease the production of TNFalpha and other pro-inflammatory mediators during inflammatory events, and they further support the notion that Tpl2 is an appropriate therapeutic target for rheumatoid arthritis and other human inflammatory diseases.

Inhibition of Tpl2 kinase and TNFalpha production with quinoline-3-carbonitriles for the treatment of rheumatoid arthritis.

The synthesis and structure-activity studies of a series of quinoline-3-carbonitriles as inhibitors of Tpl2 kinase are described. Potent inhibitors of Tpl2 kinase with selectivity against a panel of selected kinases in enzymatic assays and specificity in cell-based phosphorylation assays in LPS-treated human monocytes were identified. Selected inhibitors with moderate activity in human whole blood assay effectively inhibited LPS/D-Gal induced TNFalpha release when administered intraperitoneally in mice.

Inhibition of Tpl2 kinase and TNF-alpha production with 1,7-naphthyridine-3-carbonitriles: synthesis and structure-activity relationships.

The synthesis and structure-activity studies of a series of 6-substituted-4-anilino-[1,7]-naphthyridine-3-carbonitriles as inhibitors of Tpl2 kinase are described. The early exploratory work described here may lead to the discovery of compounds with significant therapeutic potential for treating rheumatoid arthritis and other inflammatory diseases.