Evaluation of the effect of GM-CSF blocking on the phenotype and function of human monocytes.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multipotent cytokine that prompts the proliferation of bone marrow-derived macrophages and granulocytes. In addition to its effects as a growth factor, GM-CSF plays an important role in chronic inflammatory autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. Reports have identified monocytes as the primary target of GM-CSF; however, its effect on monocyte activation has been under-estimated. Here, using flow cytometry and ELISA we show that GM-CSF induces an inflammatory profile in human monocytes, which includes an upregulated expression of HLA-DR and CD86 molecules and increased production of TNF-α and IL-1ß. Conversely, blockage of endogenous GM-CSF with antibody treatment not only inhibited the inflammatory profile of these cells, but also induced an immunomodulatory one, as shown by increased IL-10 production by monocytes. Further analysis with qPCR, flow cytometry and ELISA experiments revealed that GM-CSF blockage in monocytes stimulated production of the chemokine CXCL-11, which suppressed T cell proliferation. Blockade of CXCL-11 abrogated anti-GM-CSF treatment and induced inflammatory monocytes. Our findings show that anti-GM-CSF treatment induces modulatory monocytes that act in a CXCL-11-dependent manner, a mechanism that can be used in the development of novel approaches to treat chronic inflammatory autoimmune diseases.

Carnosic Acid Inhibits CXCR3 Ligands Production in IL-27-Stimulated Human Oral Epithelial Cells.

Carnosic acid, which is a bioactive compound isolated from rosemary, has various pharmacological effects. However, the anti-inflammatory effect of carnosic acid on periodontitis is still unknown. The aim of this study was to investigate the effect of carnosic acid on CXC chemokine receptor 3 (CXCR3) ligands, which are involved in Th1 cells migration and accumulation, production in interleukin (IL)-27-stimulated human oral epithelial cells (TR146 cells). Carnosic acid decreased CXC chemokine ligand (CXCL)9, CXCL10, and CXCL11 production in IL-27-stimulated TR146 cells in a dose-dependent fashion. Moreover, we disclosed that carnosic acid could suppress signal transducer and activator of transcription (STAT)1, STAT3, and protein kinase B (Akt) phosphorylation in IL-27-stimulated TR146 cells. Furthermore, STAT1, STAT3, and Akt inhibitors could suppress CXCR3 ligands production in IL-27-treated TR146 cells. In summary, carnosic acid could reduce CXCR3 ligands production in human oral epithelial cell by inhibiting STAT1, STAT3, and Akt activation.

Honokiol and Magnolol Inhibit CXCL10 and CXCL11 Production in IL-27-Stimulated Human Oral Epithelial Cells.

Honokiol and magnolol, which are lignans isolated from Magnolia quinquepeta, have some pharmacological effects. However, the anti-inflammatory effects of honokiol and magnolol on periodontal disease are still uncertain. The aim of this study was to examine the effect of honokiol and magnolol on CXC chemokine receptor 3 (CXCR3) ligands, which are related with Th1 cell migration, production in interleukin (IL)-27-stimulated human oral epithelial cells (TR146 cells). Honokiol and magnolol inhibited CXC chemokine ligand (CXCL)10 and CXCL11 production in IL-27-stimulated TR146 cells in a dose-dependent manner. Moreover, we revealed that honokiol and magnolol could suppress signal transducer and activator of transcription (STAT)3 and protein kinase B (Akt) phosphorylation in IL-27-stimulated TR146 cells though STAT1 phosphorylation was not suppressed by honokiol and magnolol treatment. Furthermore, STAT3 and Akt inhibitors could suppress CXCR3 ligand production in TR146 cells. In summary, honokiol and magnolol could reduce CXCR3 ligand production in oral epithelial cell by inhibiting STAT3 and Akt activation.

Ligand-biased and probe-dependent modulation of chemokine receptor CXCR3 signaling by negative allosteric modulators.

Over the last decade, functional selectivity (or ligand bias) has evolved from being a peculiar phenomenon to being recognized as an essential feature of synthetic ligands that target G protein-coupled receptors (GPCRs). The CXC chemokine receptor 3 (CXCR3) is an outstanding platform to study various aspects of biased signaling, because nature itself uses functional selectivity to manipulate receptor signaling. At the same time, CXCR3 is an attractive therapeutic target in the treatment of autoimmune diseases and cancer. Herein we report the discovery of an 8-azaquinazolinone derivative (N-{1-[3-(4-ethoxyphenyl)-4-oxo-3,4-dihydropyrido[2,3-d]pyrimidin-2-yl]ethyl}-4-(4-fluorobutoxy)-N-[(1-methylpiperidin-4-yl)methyl]butanamide, 1 b) that can inhibit CXC chemokine 11 (CXCL11)-dependent G protein activation over ß-arrestin recruitment with 187-fold selectivity. This compound also demonstrates probe-dependent activity, that is, it inhibits CXCL11- over CXCL10-mediated G protein activation with 12-fold selectivity. Together with a previously reported biased negative allosteric modulator from our group, the present study provides additional information on the molecular requirements for allosteric modulation of CXCR3.

IL-17A signaling in colonic epithelial cells inhibits pro-inflammatory cytokine production by enhancing the activity of ERK and PI3K.

Our previous data suggested that IL-17A contributes to the inhibition of Th1 cell function in the gut. However, the underlying mechanisms remain unclear. Here we demonstrate that IL-17A signaling in colonic epithelial cells (CECs) increases TNF-α-induced PI3K-AKT and ERK phosphorylation and inhibits TNF-α induced expression of IL-12P35 and of a Th1 cell chemokine, CXCL11 at mRNA level. In a co-culture system using HT-29 cells and PBMCs, IL-17A inhibited TNF-α-induced IL-12P35 expression by HT-29 cells and led to decreased expression of IFN-γ and T-bet by PBMCs. Finally, adoptive transfer of CECs from mice with Crohn's Disease (CD) led to an enhanced Th1 cell response and exacerbated colitis in CD mouse recipients. The pathogenic effect of CECs derived from CD mice was reversed by co-administration of recombinant IL-17A. Our data demonstrate a new IL-17A-mediated regulatory mechanism in CD. A better understanding of this pathway might shed new light on the pathogenesis of CD.

Inhibition of human astrocyte and microglia neurotoxicity by calcium channel blockers.

We examined the effects of L-type calcium channel blockers (CCBs) on toxicity exerted by activated human astrocytes and microglia towards SH-SY5Y human neuronal cells. The CCBs nimodipine (NDP) and verapamil (VPM) both significantly suppressed toxic secretions from human astrocytes and astrocytoma U-373 MG cells that were induced by interferon (IFN)-γ. NDP also inhibited neurotoxic secretions of human microglia and monocytic THP-1 cells that were induced by the combination of lipopolysaccharide and IFN-γ. In human astrocytes, both NDP and VPM reduced IFN-γ-induced phosphorylation of signal transducer and activator of transcription (STAT) 3. They also inhibited the astrocytic production of IFN-γ-inducible T cell α chemoattractant (I-TAC). These results suggest that CCBs attenuate IFN-γ-induced neurotoxicity of human astrocytes through inhibition of the STAT3 signaling pathway. L-type CCBs, especially NDP, might be a useful treatment option for a broad spectrum of neurodegenerative diseases, including Alzheimer disease, where the pathology is believed to be exacerbated by neurotoxic glial activation.

Peroxisome proliferator-activated receptor-α agonists modulate CXCL9 and CXCL11 chemokines in Graves' ophthalmopathy fibroblasts and preadipocytes.

Peroxisome proliferator-activated receptors (PPAR)α have been shown to exert immunomodulatory effects in autoimmune disorders; no study evaluated the effect of PPARα activation in Graves' ophthalmopathy (GO). We show the presence of PPARα, δ and γ in GO fibroblasts and preadipocytes. PPARα activators have a potent inhibitory action on the secretion of CXCL9 and CXCL11 chemokines (induced by IFNγ and TNFα) in fibroblasts and preadipocytes. The potency of the used PPARα agonists was maximum on the secretion of CXCL11 (67% inhibition by fenofibrate) in fibroblasts. The relative potency of the compounds in GO fibroblasts was different with each chemokine. PPARα agonists were stronger inhibitors of CXCL9 and CXCL11 (in GO fibroblasts and preadipocytes) than PPARγ activators. This study first shows that PPARα activators inhibit CXCL9 and CXCL11 chemokines in normal and GO fibroblasts and preadipocytes, suggesting that PPARα may be involved in the modulation of the immune response in GO.

Differential regulation of chemokines by IL-17 in colonic epithelial cells.

The IL-23/IL-17 pathway plays an important role in chronic inflammatory diseases, including inflammatory bowel disease. In inflammatory bowel disease, intestinal epithelial cells are an important source of chemokines that recruit inflammatory cells. We examined the effect of IL-17 on chemokine expression of HT-29 colonic epithelial cells. IL-17 strongly repressed TNF-alpha-stimulated expression of CXCL10, CXCL11, and CCL5, but synergized with TNF-alpha for induction of CXCL8, CXCL1, and CCL20 mRNAs. For CXCL10, IL-17 strongly inhibited promoter activity but had no effect on mRNA stability. In contrast, for CXCL8, IL-17 slightly decreased promoter activity but stabilized its normally unstable mRNA, leading to a net increase in steady-state mRNA abundance. IL-17 synergized with TNF-alpha in transactivating the epidermal growth factor receptor (EGFR) and in activating ERK and p38 MAPK. The p38 and ERK pathway inhibitors SB203580 and U0126 reversed the repressive effect of IL-17 on CXCL10 mRNA abundance and promoter activity and also reversed the inductive effect of IL-17 on CXCL8 mRNA, indicating that MAPK signaling mediates both the transcriptional repression of CXCL10 and the stabilization of CXCL8 mRNA by IL-17. The EGFR kinase inhibitor AG1478 partially reversed the effects of IL-17 on CXCL8 and CXCL10 mRNA, demonstrating a role for EGFR in downstream IL-17 signaling. The overall results indicate a positive effect of IL-17 on chemokines that recruit neutrophils (CXCL8 and CXCL1), and Th17 cells (CCL20). In contrast, IL-17 represses expression of CXCL10, CXCL11, and CCR5, three chemokines that selectively recruit Th1 but not other effector T cells.

Antagonism of the chemokine receptors CXCR3 and CXCR4 reduces the pathology of experimental autoimmune encephalomyelitis.

Chemokines regulate lymphocyte trafficking under physiologic and pathologic conditions. In this study, we have investigated the role of CXCR3 and CXCR4 in the activation of T lymphocytes and their migration to the central nervous system (CNS) using novel mutant chemokines to antagonize CXCR3 and CXCR4 specifically. A series of truncation mutants of CXCL11, which has the highest affinity for CXCR3, were synthesized, and an antagonist, CXCL11((4-79)), was obtained. CXCL11((4-79)) strongly inhibited the migration of activated mouse T cells in response to all three high-affinity CXCR3 ligands, CXCL9, 10 and 11. CXCL12((P2G2)), while exhibiting minimal agonistic activity, potently inhibited the migration of activated mouse T cells in response to CXCL12. Interfering with the action of CXCR3 and CXCR4 with these synthetic receptor antagonists inhibited experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis and reduced the accumulation of CD4(+) T cells in the CNS. Further investigation demonstrated that CXCL12((P2G2)) inhibited the sensitization phase, whereas CXCL11((4-79)) inhibited the effector phase of the immune response. Our data suggest that simultaneous targeting of CXCR4 and CXCR3 may be of benefit in the treatment of the CNS autoimmune disease.