Inhibiting the C5-C5a receptor axis

Activation of the complement system is a major pathogenic event that drives various inflammatory responses in numerous diseases. All pathways of complement activation lead to cleavage of the C5 molecule generating the anaphylatoxin C5a and, C5b that subsequently forms the terminal complement complex (C5b-9). C5a exerts a predominant pro-inflammatory activity through interactions with the classical G-protein coupled receptor C5aR (CD88) as well as with the non-G protein coupled receptor C5L2 (GPR77), expressed on various immune and non-immune cells. C5b-9 causes cytolysis through the formation of the membrane attack complex (MAC), and sub-lytic MAC and soluble C5b-9 also possess a multitude of non-cytolytic immune functions. These two complement effectors, C5a and C5b-9, generated from C5 cleavage, are key components of the complement system responsible for propagating and/or initiating pathology in different diseases, including paroxysmal nocturnal hemoglobinuria, rheumatoid arthritis, ischemia-reperfusion injuries and neurodegenerative diseases. Thus, the C5-C5a receptor axis represents an attractive target for drug development. This review provides a comprehensive analysis of different methods of inhibiting the generation of C5a and C5b-9 as well as the signalling cascade of C5a via its receptors. These include the inhibition of C5 cleavage through targeting of C5 convertases or via the C5 molecule itself, as well as blocking the activity of C5a by neutralizing antibodies and pharmacological inhibitors, or by targeting C5a receptors per se. Examples of drugs and naturally occurring compounds used are discussed in relation to disease models and clinical trials. To date, only one such compound has thus far made it to clinical medicine: the anti-C5 antibody eculizumab, for treating paroxysmal nocturnal hemoglobinuria. However, a number of drug candidates are rapidly emerging that are currently in early-phase clinical trials. The C5-C5a axis as a target for drug development is highly promising for the treatment of currently intractable major human diseases.     

A family of ParA-like ATPases promotes cell pole maturation by facilitating polar localization of chemotaxis proteins

Stochastic processes are thought to mediate localization of membrane-associated chemotaxis signaling clusters in peritrichous bacteria. Here, we identified a new family of ParA-like ATPases (designated ParC [for partitioning chemotaxis]) encoded within chemotaxis operons of many polar-flagellated γ-proteobacteria that actively promote polar localization of chemotaxis proteins. In Vibrio cholerae, a single ParC focus is found at the flagellated old pole in newborn cells, and later bipolar ParC foci develop as the cell matures. The cell cycle-dependent redistribution of ParC occurs by its release from the old pole and subsequent relocalization at the new pole, consistent with a “diffusion and capture” model for ParC dynamics. Chemotaxis proteins encoded in the same cluster as ParC have a similar unipolar-to-bipolar transition; however, they reach the new pole after the arrival of ParC. Cells lacking ParC exhibit aberrantly localized foci of chemotaxis proteins, reduced chemotaxis, and altered motility, which likely accounts for their enhanced colonization of the proximal small intestine in an animal model of cholera. Collectively, our findings indicate that ParC promotes the efficiency of chemotactic signaling processes. In particular, ParC-facilitated development of a functional chemotaxis apparatus at the new pole readies this site for its development into a functional old pole after cell division.     

Involvement of P2X4 and P2Y12 receptors in ATP-induced microglial chemotaxis

We previously reported that extracellular ATP induces membrane ruffling and chemotaxis of microglia and suggested that their induction is mediated by the Gi/o-protein coupled P2Y(12) receptor (P2Y(12)R). Here we report discovering that the P2X(4) receptor (P2X(4)R) is also involved in ATP-induced microglial chemotaxis. To understand the intracellular signaling pathway downstream of P2Y(12)R that underlies microglial chemotaxis, we examined the effect of two phosphatidylinositol 3'-kinase (PI3K) inhibitors, wortmannin, and LY294002, on chemotaxis in a Dunn chemotaxis chamber. The PI3K inhibitors significantly suppressed chemotaxis without affecting ATP-induced membrane ruffling. ATP stimulation increased Akt phosphorylation in the microglia, and the increase was reduced by the PI3K inhibitors and a P2Y(12)R antagonist. These results indicate that P2Y(12)R-mediated activation of the PI3K pathway is required for microglial chemotaxis in response to ATP. We also found that the Akt phosphorylation was reduced when extracellular calcium was chelated, suggesting that ionotropic P2X receptors are involved in microglial chemotaxis by affecting the PI3K pathway. We therefore tested the effect of various P2X(4)R antagonists on the chemotaxis, and the results showed that pharmacological blockade of P2X(4)R significantly inhibited it. Knockdown of the P2X(4) receptor in microglia by RNA interference through the lentivirus vector system also suppressed the microglial chemotaxis. These results indicate that P2X(4)R as well as P2Y(12)R is involved in ATP-induced microglial chemotaxis.     

Chemotactic effect of melatonin on leukocytes

Melatonin seems to be an important stimulatory factor of the immune system. This indolamine is capable of inducing activation of leukocytes. Tissue leukocyte infiltration is a key feature of inflammatory and immune responses; however, there is no information about the effect of melatonin on leukocyte chemotaxis. Therefore, the aim of this study was to examine the in vitro and in vivo effects of melatonin on leukocyte chemotaxis, on modulation of leukocyte chemotaxis to other chemoattractants and on the in vivo induction of leukocyte chemokines. Neutrophils and mononuclear leukocytes (PBMC) were isolated by a discontinuous gradient on Hystopaque. Chemotaxis was performed in blind well Boyden's chambers. In vivo chemotaxis was determined after intraperitoneal injection of melatonin into rats. Leukocyte chemotactic response and leukocyte chemokine expression were determined in human volunteers treated with 20 mg daily of melatonin. Increased neutrophils and PBMC chemotaxis in response to 1.2 nm melatonin was observed in vitro. Peritoneal leukocytes were found increased after melatonin injection. Humans treated with melatonin showed an increased neutrophil chemotactic response to a physiological chemoattractant and increased expression of intracellular chemokines; however, decreased chemotactic response and no chemokine expression were observed in PBMC. These data suggest that melatonin could have a relevant role during the tissue leukocyte infiltration in inflammatory and immune responses.     

空肠弯曲菌mcp1/2/3基因原核表达及其产物与细菌趋化作用的相关性

目的 克隆空肠弯曲菌(Campylobacter jejuni)接受甲基趋化蛋白(MCP)编码基因mcp1、mcp2和mcp3并构建其原核表达系统,建立空肠弯曲菌体外趋化模型并确定趋化诱导物质,了解MCPs与趋化诱导物之间的关系.方法 PCR扩增mcp1、mcp2和mcp3基因片段,T-A克隆后测序.构建上述目的 基因原核表达系统,SDS-PAGE和Bio-Rad凝胶成像分析系统检查目的 重组蛋白rMCP1、rMCP2和rMCP3的表达情况,Ni-NTA亲和层析法提纯rMCPs.rMCPs免疫家兔获得抗血清,免疫扩散法测其效价.用饱和硫酸铵盐析法和DEAE-32离子交换法提纯IgG,经胃蛋白酶酶解和Sephedex G-100层析制备IgGF(ab')2.建立HAP(hard-agar plus)法空肠弯曲菌体外趋化模型并检测8种物质的趋化诱导作用.采用基于IgG F(ab')2封闭的趋化阻断试验,确定不同MCPs的功能及其差异.结果 PCR扩增获得预期大小的mcp1、mcp2和mop3基因片段,其核苷酸和氨基酸序列与文献报道完全相同.所构建的原核表达系统能有效地表达各rMCPs,其产量均约为细菌总蛋白的10%.rMCP1、rMCP2和rMCP3免疫家兔后能产生特异性抗体,其免疫扩散效价均为1∶4.牛胆汁和脱氧胆酸钠(DOC)对空肠弯曲菌趋化有浓度依赖性诱导作用(P<0.05).MCP1和MCP2被其IgG F(ab')2 封闭后,空肠弯曲菌对DOC的趋化能力明显减弱(P<0.05),MCP3被封闭后对空肠弯曲菌趋化能力无影响(P>0.05).结论 本研究成功地表达了空肠弯曲菌MCPs蛋白.牛胆汁和DOC是诱导空肠弯曲菌趋化的信号物质,MCP1和MCP2可能参与该菌对DOC的趋化过程.     

Selective upregulation of interleukin‐8 by human rhabdomyosarcomas in response to hypoxia: therapeutic implications

Rhabdomyosarcoma (RMS) is the most common soft‐tissue sarcoma of adolescence and childhood. Because RMS tumors are highly vascularized, we sought to determine which factors secreted by RMS cells are crucial in stimulating angiogenesis in response to hypoxia. To address this issue, we evaluated expression of several proangiogenic factors [interleukin (IL)‐8, vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF)‐2, stromal‐derived factor (SDF)‐1, hepatocyte growth factor (HGF) and leukemia inhibitory factor (LIF)] in 8 human RMS cell lines in both normal steady‐state and hypoxic conditions. We found by real‐time quantitative polymerase chain reaction (RQ‐PCR) and confirmed by enzyme‐linked immunosorbent assay (ELISA) that from all the factors evaluated, IL‐8, whose expression is very low in normoxia, had been very highly expressed and secreted by RMS cells lines during hypoxic conditions (∼40–170 times). Interestingly, this upregulation was not affected by knocking down hypoxia‐inducible factor (HIF)‐1α, but was inhibited by mitogen‐activated protein kinase (MAPK)p42/44 and phosphatidylinositaol 3‐kinase (PI3K)/AKT pathway inhibitors. This suggests that IL‐8 expression is regulated in an activating protein (AP)‐1‐ and nuclear factor (NF)‐κB‐dependent manner. Furthermore, we found that conditioned media (CM) harvested from RMS cells exposed to hypoxia activated and stimulated chemotactic responses in human umbilical vein endothelial cells (HUVECs) and that IL‐8 was responsible for hypoxia‐related effects. Finally, by employing shRNA, the expression of IL‐8 in human RH‐30 cells was downregulated. We noticed that such RMS cells, if injected into skeletal muscles of immunodeficient mice, have a reduced ability for tumor formation. We conclude that IL‐8 is a pivotal proangiogenic factor released by human RMS cells in hypoxic conditions and that the targeting of IL‐8 may prove to be a novel and efficient strategy for inhibiting RMS growth.     

问号钩体趋化相关基因特征分析

目的 预测问号钩体黄疸出血群赖型赖株的趋化信号传导途径，并深入分析趋化相关基因。方法 使用ProtParam tool，NCBI／Blastp进行蛋白参数分析和结构域分析，使用Clustalw软件进行多序列对比，与大肠埃希菌K-12趋化相关基因进行比较。结果 问号钩体趋化相关基因共30个，分为MCPs和che两组基因，功能与大肠埃希菌趋化相关基因相似，并预测出问号钩体趋化信号传导途径。结论 问号钩体趋化相关基因较大肠埃希菌、苍白密螺旋体和伯氏疏螺旋体多，提示其趋化传导途径更为复杂，适应宿主的能力也更强，可能是钩体的重要毒力因子之一。     

Effect of dietary fish oil supplemented with different doses of vitamin e on neutrophil chemotaxis in healthy volunteers

The effect of fish oils supplemented with a high or low dose of vitamin E on neutrophil chemotaxis was investigated in a double-blind crossover study. Twelve healthy volunteers were given 30 mL of either oil (5.4 g eicosapentaenoic acid and 3.2 g docosahexaenoic acid) daily for three weeks The serum vitamin E (-tocopherol) concentration decreased and the plasma malondialdehyde concentration increased only after supplementation with the low vitamin E fish oil, the latter change indicating increased lipid peroxidation. Both oils decreased neutrophil chemotaxis significantly and there was no significant difference in this respect between the high and low vitamin E oils, indicating that the effect was due primarily to the fish oil and not to the vitamin E. Generation of leukotriene B₄ by neutrophils was unaltered. Dietary supplementation with n-3 fish oil could have beneficial effects in pathological conditions with activated neutrophils, such as ischemic heart disease.     

Targeted replacement of rodent CCR2 with the human orthologue CCR2B: A mouse model for in vivo analysis of human target‐selective small molecule MCP‐1 receptor antagonists

Rodent models for testing the efficacy of lead compounds are often invalidated by species selectivity of the compounds. The advent of mouse embryonic stem cell technology has allowed the development of genetically engineered mouse strains that incorporate a specific human gene in place of the orthologous mouse gene, a so‐called knock‐in mouse. This study describes the generation and validation of a mutant mouse line that expresses human CCR2B as a functional substitute for murine CCR2. The human CCR2B knock‐in mice are viable and appear normal. In vitro assays indicate that the CCR2B knock‐in is functionally expressed, giving a macrophage chemotactic profile in response to JE or MCP‐1 that is similar to human peripheral blood monocytes rather than that of a murine macrophage cell line. In addition, the human selective CCR2B antagonist, SB‐399721, was a more potent inhibitor of CCR2B knock‐in macrophages in response to hMCP‐1 than JE. The ability of the human CCR2B gene to functionally substitute for the mouse orthologue in vivo is demonstrated by a normal inflammatory response to intraperitoneal thioglycollate injection. Drug Dev. Res. 55:197–209, 2002. © 2002 Wiley‐Liss, Inc.     

Ex vivo studies of polymorphonuclear neutrophils from patients with early-onset forms of periodontitis (I).

Abstract The polymorphonuclear neutrophil (PMN) appears lo be an important cell in the protection of the host from pathogenic periodontal microorganisms and, despite some reports to the contrary, it is generally assumed that early-onset forms of periodontal disease including both juvenile and rapidly progressing periodontitis are associated with a defect in PMN chemotactic behaviour. The purpose of the present study was to examine the peripheral PMN chemotactic behaviour, using the under agarose method, in 4 groups, namely healthy periodontium group (n= 7), gingivitis group (n= 8), early-onset periodontitis group (n= 17) and adult periodontitis group (n= 8). PMN from early-onset periodontitis patients showed normal random and chemotactic locomotory behaviour when compared with those of PMN from subjects of the other groups. No statistically significant difference could be found among the 4 studied groups, with regard to spontaneous and oriented migration.