N-type Calcium Channel in the Pathogenesis of Experimental Autoimmune Encephalomyelitis

One of the family of voltage-gated calcium channels (VGCC), the N-type Ca²⁺ channel, is located predominantly in neurons and is associated with a variety of neuronal responses, including neurodegeneration. A precise mechanism for how the N-type Ca²⁺ channel plays a role in neurodegenerative disease, however, is unknown. In this study, we immunized N-type Ca²⁺ channel α_1B-deficient (α_1B^−/−) mice and their wild type (WT) littermates with myelin oligodendrocyte glycoprotein 35–55 and analyzed the progression of experimental autoimmune encephalomyelitis (EAE). The neurological symptoms of EAE in the α_1B^−/− mice were less severe than in the WT mice. In conjunction with these results, sections of the spinal cord (SC) from α_1B^−/− mice revealed a reduction in both leukocytic infiltration and demyelination compared with WT mice. No differences were observed in the delayed-type hypersensitivity response, spleen cell proliferation, or cytokine production from splenocytes between the two genotypes. On the other hand, Western blot array analysis and RT-PCR revealed that a typical increase in the expression of MCP-1 in the SC showed a good correlation with the infiltration of leukocytes into the SC. Likewise, immunohistochemical analysis showed that the predominant source of MCP-1 was activated microglia. The cytokine-induced production of MCP-1 in primary cultured microglia from WT mice was significantly higher than that from α_1B^−/− mice and was significantly inhibited by a selective N-type Ca²⁺ channel antagonist, ω-conotoxin GVIA or a withdrawal of extracellular Ca²⁺. These results suggest that the N-type Ca²⁺ channel is involved in the pathogenesis of EAE at least in part by regulating MCP-1 production by microglia.     

Immunological signature of the different clinical stages of the HTLV-1 infection: establishing serum biomarkers for HTLV-1-associated disease morbidity

Abstract

This study aimed at establishing the immunological signature and an algorithm for clinical management of the different clinical stages of the HTLV-1-infection based on serum biomarkers. A panel of serum biomarkers was evaluated by four sets of innovative/non-conventional data analysis approaches in samples from 87 HTLV-1 patients: asymptomatic carriers (AC), putative HTLV-1 associated myelopathy/tropical spastic paraparesis (pHAM/TSP) and HAM/TSP. The analysis of cumulative curves and molecular signatures pointed out that HAM/TSP presented a pro-inflammatory profile mediated by CXCL10/LTB-4/IL-6/TNF-α/IFN-γ, counterbalanced by IL-4/IL-10. The analysis of biomarker networks showed that AC presented a strongly intertwined pro-inflammatory/regulatory net with IL-4/IL-10 playing a central role, while HAM/TSP exhibited overall immune response toward a predominant pro-inflammatory profile. At last, the classification and regression trees proposed for clinical practice allowed for the construction of an algorithm to discriminate AC, pHAM and HAM/TSP patients with the elected biomarkers: IFN-γ, TNF-α, IL-10, IL-6, IL-4 and CysLT. These findings reveal a complex interaction among chemokine/leukotriene/cytokine in HTLV-1 infection and suggest the use of the selected but combined biomarkers for the follow-up/diagnosis of disease morbidity of HTLV-1-infected individuals.     

Molecular Basis of Glycosaminoglycan Heparin Binding to the Chemokine CXCL1 Dimer

Glycosaminoglycan (GAG)-bound and soluble chemokine gradients in the vasculature and extracellular matrix mediate neutrophil recruitment to the site of microbial infection and sterile injury in the host tissue. However, the molecular principles by which chemokine-GAG interactions orchestrate these gradients are poorly understood. This, in part, can be directly attributed to the complex interrelationship between the chemokine monomer-dimer equilibrium and binding geometry and affinities that are also intimately linked to GAG length. To address some of this missing knowledge, we have characterized the structural basis of heparin binding to the murine CXCL1 dimer. CXCL1 is a neutrophil-activating chemokine and exists as both monomers and dimers (K_d = 36 μm). To avoid interference from monomer-GAG interactions, we designed a trapped dimer (dCXCL1) by introducing a disulfide bridge across the dimer interface. We characterized the binding of GAG heparin octasaccharide to dCXCL1 using solution NMR spectroscopy. Our studies show that octasaccharide binds orthogonally to the interhelical axis and spans the dimer interface and that heparin binding enhances the structural integrity of the C-terminal helical residues and stability of the dimer. We generated a quadruple mutant (H20A/K22A/K62A/K66A) on the basis of the binding data and observed that this mutant failed to bind heparin octasaccharide, validating our structural model. We propose that the stability enhancement of dimers upon GAG binding regulates in vivo neutrophil trafficking by increasing the lifetime of “active” chemokines, and that this structural knowledge could be exploited for designing inhibitors that disrupt chemokine-GAG interactions and neutrophil homing to the target tissue.     

Neutralizing Nanobodies Targeting Diverse Chemokines Effectively Inhibit Chemokine Function

Chemokine receptors and their ligands play a prominent role in immune regulation but many have also been implicated in inflammatory diseases such as multiple sclerosis, rheumatoid arthritis, allograft rejection after transplantation, and also in cancer metastasis. Most approaches to therapeutically target the chemokine system involve targeting of chemokine receptors with low molecular weight antagonists. Here we describe the selection and characterization of an unprecedented large and diverse panel of neutralizing Nanobodies (single domain camelid antibodies fragment) directed against several chemokines. We show that the Nanobodies directed against CCL2 (MCP-1), CCL5 (RANTES), CXCL11 (I-TAC), and CXCL12 (SDF-1α) bind the chemokines with high affinity (at nanomolar concentration), thereby blocking receptor binding, inhibiting chemokine-induced receptor activation as well as chemotaxis. Together, we show that neutralizing Nanobodies can be selected efficiently for effective and specific therapeutic treatment against a wide range of immune and inflammatory diseases.     

Matrix Metalloproteinase 8 (Collagenase 2) Induces the Expression of Interleukins 6 and 8 in Breast Cancer Cells

Matrix metalloproteinase 8 (MMP-8) is a tumor-suppressive protease that cleaves numerous substrates, including matrix proteins and chemokines. In particular, MMP-8 proteolytically activates IL-8 and, thereby, regulates neutrophil chemotaxis in vivo. We explored the effects of expression of either a WT or catalytically inactive (E198A) mutant version of MMP-8 in human breast cancer cell lines. Analysis of serum-free conditioned media from three breast cancer cell lines (MCF-7, SK-BR-3, and MDA-MB-231) expressing WT MMP-8 revealed elevated levels of IL-6 and IL-8. This increase was mirrored at the mRNA level and was dependent on MMP-8 catalytic activity. However, sustained expression of WT MMP-8 by breast cancer cells was non-permissive for long-term growth, as shown by reduced colony formation compared with cells expressing either control vector or E198A mutant MMP-8. In long-term culture of transfected MDA-MB-231 cells, expression of WT but not E198A mutant MMP-8 was lost, with IL-6 and IL-8 levels returning to base line. Rare clonal isolates of MDA-MB-231 cells expressing WT MMP-8 were generated, and these showed constitutively high levels of IL-6 and IL-8, although production of the interleukins was no longer dependent upon MMP-8 activity. These studies support a causal connection between MMP-8 activity and the IL-6/IL-8 network, with an acute response to MMP-8 involving induction of the proinflammatory mediators, which may in part serve to compensate for the deleterious effects of MMP-8 on breast cancer cell growth. This axis may be relevant to the recognized ability of MMP-8 to orchestrate the innate immune system in inflammation in vivo.     

CXCL8 in thyroid disease: From basic notions to potential applications in clinical practice

CXCL8 was the first chemokine shown to be secreted by thyrocytes. Experimental data suggest that CXCL8 plays a role in thyroid homeostasis but its role in thyroid diseases remains poorly investigated. Clinical studies measuring the serum levels of CXCL8 in patients with autoimmune-thyroid-diseases reported conflicting results. Solid evidences support a role of CXCL8 as a tumor-promoting agent in several human cancers. Studies in thyroid cancer are still in their initial stage, but promising. Several evidences indicate that thyroid cancer may share with other human malignancies some of the effects of CXCL8 and highlight the possibility of using CXCL8 as a marker of aggressiveness. Basic and clinical evidences in favor or against a role for CXCL8 in thyroid diseases are discussed.     

鱼类趋化因子的研究进展

趋化因子(Chemokine)是由多种细胞在致病因子刺激后分泌的一类低分子量的细胞因子,它们都具有激活和趋化白细胞的作用。趋化因子从结构上可分为四类:CC型、CXC型、CX3C型和C型;从功能上可分为两种类型:一类主要诱导白细胞到炎症部位;另一类主要是对肌体起免疫监控作用。目前,有关鱼类趋化因子的研究主要集中于CXC型和CC型两类,以及其在非特异性免疫中的作用。     

趋化因子及趋化因子受体在急性胰腺炎中的研究进展

普遍认为,急性胰腺炎起始于腺泡细胞内的胰蛋白酶原激活,随后引起的炎症反应加剧病情,也是多器官功能衰竭的主要原因。然而,最新的研究表明,急性胰腺炎引起的炎症反应是不依赖于胰蛋白酶原激活的独立病理过程。趋化因子作为能引起细胞趋化的细胞因子,通过与趋化因子受体作用,不但能调控淋巴细胞的生长、成熟和迁移,也参与多种炎症疾病与癌症的病理过程。近年来,多项研究已经阐述趋化因子及趋化因子受体在急性胰腺炎的发病发展过程中起到至关重要的作用。本文总结了CC,CXC和CX3C趋化因子家族成员在参与急性胰腺炎的炎症反应及对胰腺损伤的修复的研究进展,这将为AP临床治疗方案的设计提供新思路。     

Structural Determinants for the Interaction of Formyl Peptide Receptor 2 with Peptide Ligands

Unlike formyl peptide receptor 1 (FPR1), FPR2/ALX (FPR2) interacts with peptides of diverse sequences but has low affinity for the Escherichia coli-derived chemotactic peptide fMet-Leu-Phe (fMLF). Using computer modeling and site-directed mutagenesis, we investigated the structural requirements for FPR2 to interact with formyl peptides of different length and composition. In calcium flux assay, the N-formyl group of these peptides is necessary for activation of both FPR2 and FPR1, whereas the composition of the C-terminal amino acids appears more important for FPR2 than FPR1. FPR2 interacts better with pentapeptides (fMLFII, fMLFIK) than tetrapeptides (fMLFK, fMLFW) and tripeptide (fMLF) but only weakly with peptides carrying negative charges at the C terminus (e.g. fMLFE). In contrast, FPR1 is less sensitive to negative charges at the C terminus. A CXCR4-based homology model of FPR1 and FPR2 suggested that Asp-281^7.32 is crucial for the interaction of FPR2 with certain formyl peptides as its negative charge may be repulsive with the terminal COO- group of fMLF and negatively charged Glu in fMLFE. Asp-281^7.32 might also form a stable interaction with the positively charged Lys in fMLFK. Site-directed mutagenesis was performed to remove the negative charge at position 281 in FPR2. The D281^7.32G mutant showed improved affinity for fMLFE and fMLF and reduced affinity for fMLFK compared with wild type FPR2. These results indicate that different structural determinants are used by FPR1 and FPR2 to interact with formyl peptides.