mgrA regulates staphylococcal virulence important for induction and progression of septic arthritis and sepsis

Septic arthritis and sepsis are common and feared complications of staphylococcal infections, and the increasing antibiotic resistance among staphylococci urge the extended research for virulence factors involved in these diseases. Staphylcoccus aureus produces a number of virulence factors controlled by several global regulatory genes including agr and sarA. MgrA is a recently identified global regulator, belonging to the SarA subfamily, which upregulates expression of several virulence factors including capsule and sortase. In addition, MgrA has been shown to regulate antibiotic resistance and decrease bacterial autolysis. In this study we have assessed the role of mgrA gene expression on induction and progression of septic arthritis and sepsis. Mice inoculated with the mgrA mutant displayed significantly less severe arthritis and showed a significantly better weight development, than wild-type inoculated mice. Importantly, all 10 mice inoculated with the mgrA mutant survived as compared to 70% mortality in the wild-type inoculated mice (p=0.003). In addition, the mgrA mutant showed significantly less bacterial persistence in kidneys as compared to the wild-type strain. We conclude that mgrA regulates virulence factors important for establishment and progression of septic arthritis and sepsis.     

Exacerbation of group B streptococcal sepsis and arthritis in diabetic mice

Group B streptococci (GBS) have been recognised as an ever-growing cause of serious invasive infections in non-pregnant adults, in particular in association with severe underlying diseases such as diabetes mellitus. In the present study we used mice rendered diabetic to gain further insights into host-pathogen interaction during induced GBS sepsis and septic arthritis. Type I diabetes was induced in adult CD-1 mice by low-dose streptozotocin treatment. Mice were then infected with different doses of GBS, and mortality, appearance of arthritis, growth of microorganisms in the organs and cytokine and chemokine profile were assessed in diabetic and control animals. The LD50 was significantly lower in diabetics than in controls, while both incidence and severity of arthritis were higher. A significantly higher number of microorganisms were recovered from the organs of diabetic mice than in controls. The worsening of sepsis and arthritis was associated with a significant increase in systemic and local production of IL-6, IL-1 beta, TNF-alpha, IL-10, macrophage inflammatory protein 1 alpha (MIP-1alpha), and MIP-2 and with a decrease in IFN-gamma production. Taken together, our results indicate an impaired host resistance to GBS infection in diabetics, likely due to a dysregulation of the cytokine network and prolonged local inflammatory response.     

Differential effects between marimastat,a TNF-alpha converting enzyme inhibitor,and anti-TNF-alpha antibody on murine models for sepsis and arthritis

We investigated the effects of marimastat, an inhibitor of TNF-alpha converting enzyme and matrix metalloproteinases, and anti-TNF-alpha antibodies on a murine model for sepsis, and on arthritis in human TNF-alpha transgenic mice. Marimastat (25-200 mg/kg) inhibited lipopolysaccharide (LPS)-induced soluble TNF-alpha production in mice in a dose-dependent manner. At an oral dose of 200 mg/kg, marimastat almost completely inhibited LPS-induced soluble TNF-alpha production, but only slightly delayed LPS lethality. On the other hand, anti-TNF-alpha antibodies completely abolished LPS-induced morbidity. In addition, anti-TNF-alpha antibodies, but not marimastat (200 mg/kg/day), inhibited the development of arthritis in human TNF-alpha transgenic mice. These results suggest that cell surface TNF-alpha may be important in the pathogenesis of murine models for sepsis and arthritis.     

ISO-1 binding to the tautomerase active site of MIF inhibits its pro-inflammatory activity and increases survival in severe sepsis

MIF is a proinflammatory cytokine that has been implicated in the pathogenesis of sepsis, arthritis, and other inflammatory diseases. Antibodies against MIF are effective in experimental models of inflammation, and there is interest in strategies to inhibit its deleterious cytokine activities. Here we identify a mechanism of inhibiting MIF pro-inflammatory activities by targeting MIF tautomerase activity. We designed small molecules to inhibit this tautomerase activity; a lead molecule, "ISO-1 ((S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester)," significantly inhibits the cytokine activity in vitro. Moreover, ISO-1 inhibits tumor necrosis factor release from macrophages isolated from LPStreated wild type mice but has no effect on cytokine release from MIFdeficient macrophages. The therapeutic importance of the MIF inhibition by ISO-1 is demonstrated by the significant protection from sepsis, induced by cecal ligation and puncture in a clinically relevant time frame. These results identify ISO-1 as the first small molecule inhibitor of MIF proinflammatory activities with therapeutic implications and indicate the potential of the MIF active site as a novel target for therapeutic interventions in human sepsis.     

Cyclophilin A: a key player for human disease

Cyclophilin A (CyPA) is a ubiquitously distributed protein belonging to the immunophilin family. CyPA has peptidyl prolyl cis-trans isomerase (PPIase) activity, which regulates protein folding and trafficking. Although CyPA was initially believed to function primarily as an intracellular protein, recent studies have revealed that it can be secreted by cells in response to inflammatory stimuli. Current research in animal models and humans has provided compelling evidences supporting the critical function of CyPA in several human diseases. This review discusses recently available data about CyPA in cardiovascular diseases, viral infections, neurodegeneration, cancer, rheumatoid arthritis, sepsis, asthma, periodontitis and aging. It is believed that further elucidations of the role of CyPA will provide a better understanding of the molecular mechanisms underlying these diseases and will help develop novel pharmacological therapies.     

内皮细胞与脓毒症

血管内皮细胞是凝血启动和炎症反应激活过程中最重要的效应细胞,而脓毒症的主要病理生理学变化是严重全身感染引起的炎症反应过度激活及凝血机能障碍。因此,血管内皮细胞活化和功能障碍是脓毒症发展恶化的中心环节。更好地理解血管内皮细胞功能对于脓毒症治疗的探索及对预防多器官衰竭和弥漫性血管内凝血发生有重要意义。本文就这方面的研究进展作一简要综述。     

Fibrinogen binding sites P336 and Y338 of clumping factor A are crucial for Staphylococcus aureus virulence

We have earlier shown that clumping factor A (ClfA), a fibrinogen binding surface protein of Staphylococcus aureus, is an important virulence factor in septic arthritis. When two amino acids in the ClfA molecule, P(336) and Y(338), were changed to serine and alanine, respectively, the fibrinogen binding property was lost. ClfAP(336)Y(338) mutants have been constructed in two virulent S. aureus strains Newman and LS-1. The aim of this study was to analyze if these two amino acids which are vital for the fibrinogen binding of ClfA are of importance for the ability of S. aureus to generate disease. Septic arthritis or sepsis were induced in mice by intravenous inoculation of bacteria. The clfAP(336)Y(338) mutant induced significantly less arthritis than the wild type strain, both with respect to severity and frequency. The mutant infected mice developed also a much milder systemic inflammation, measured as lower mortality, weight loss, bacterial growth in kidneys and lower IL-6 levels. The data were verified with a second mutant where clfAP(336) and Y(338) were changed to alanine and serine respectively. When sepsis was induced by a larger bacterial inoculum, the clfAP(336)Y(338) mutants induced significantly less septic death. Importantly, immunization with the recombinant A domain of ClfAP(336)SY(338)A mutant but not with recombinant ClfA, protected against septic death. Our data strongly suggest that the fibrinogen binding activity of ClfA is crucial for the ability of S. aureus to provoke disease manifestations, and that the vaccine potential of recombinant ClfA is improved by removing its ability to bind fibrinogen.     

Ghrelin protects against experimental sepsis by inhibiting high-mobility group box 1 release and by killing bacteria

Sepsis, a life-threatening complication of infections and the most common cause of death in intensive care units, is characterized by a hyperactive and out-of-balance network of endogenous proinflammatory cytokines. None of the current therapies are entirely effective, illustrating the need for novel therapeutic approaches. Ghrelin (GHR) is an orexigenic peptide that has emerged as a potential endogenous anti-inflammatory factor. In this study, we show that the delayed administration of GHR protects against the mortality in various models of established endotoxemia and sepsis. The therapeutic effect of GHR is mainly mediated by decreasing the secretion of the high mobility box 1 (HMGB1), a DNA-binding factor that acts as a late inflammatory factor critical for sepsis progression. Macrophages seem to be the major cell targets in the inhibition of HMGB1 secretion, in which GHR blocked its cytoplasmic translocation. Interestingly, we also report that GHR shows a potent antibacterial activity in septic mice and in vitro. Remarkably, GHR also reduces the severity of experimental arthritis and the release of HMGB1 to serum. Therefore, by regulating crucial processes of sepsis, such as the production of early and late inflammatory mediators by macrophages and the microbial load, GHR represents a feasible therapeutic agent for this disease and other inflammatory disorders.     

Extracellular-matrix-binding proteins as targets for the prevention of Staphylococcus aureus infections

Staphylococcal infections cause a number of serious diseases, ranging from acute septicaemia to chronic problems such as osteomyelitis and septic arthritis. Resistance to antibiotics is a growing problem and has re-ignited interest in vaccines and in passive immunization with antibodies. Natural infections and vaccines based on whole bacteria lead to poor antibody responses, but recent research using animal models of several staphylococcal diseases reveals that vaccines based on recombinant staphylococcal extracellular-matrix-binding proteins are much more protective. Passive immunization with antibodies against one of these proteins (collagen-binding protein) also shows promise in a mouse model of sepsis.     

Tumor necrosis factor as a pharmacological target

As indicated by its name, tumor necrosis factor (TNF), cloned in 1985, was originally described as a macrophage-derived endogenous mediator that can induce hemorrhagic necrosis of solid tumors and kill some tumor cell lines in vitro. Unfortunately, its promising use as an anticancer agent was biased by its toxicity, which was clear soon from the first clinical trials with TNF in cancer. Almost at the same time TNF was being developed as an anticancer drug, it became clear that TNF was identical to a mediator responsible for cachexia associated with sepsis, which was termed cachectin. This research led to the finding that TNF is, in fact, the main lethal mediator of sepsis and to the publication of a huge number of articles showing that TNF inhibits the toxic effects of bacterial endotoxins, which are now described as systemic inflammatory response. Although the clinical trials with anti-TNF in sepsis have not been successful thus far, undoubtedly as a result of the complexity of this clinical setting, these studies ultimately led to the identification of TNF as a key inflammatory mediator and to the development of anti-TNF molecules (soluble receptors and antibodies) for important diseases including rheumatoid arthritis and Crohn’s disease. On the other side, the mechanisms by which TNF and related molecules induce cell death have been studied in depth, and their knowledge might, in the future, suggest means of improve the therapeutic index of TNF in cancer.     

Lack of B7-1 and B7-2 costimulatory molecules modulates the severity of group B Streptococcus-induced arthritis

Group B streptococci have long been known as a leading cause of life-threatening infection in neonates, young infants and pregnant women, and recently have been recognized as an ever-growing cause of serious invasive infections in nonpregnant adults. B7-1 and B7-2 are two molecules with immunoregulatory functions implicated in the differentiation of T cells. The present study examined the role of B7-1 and B7-2 during group B streptococci-induced sepsis and arthritis. B7-1- or B7-2-deficient mice were infected with 1 × 10⁷ streptococci, and mortality, appearance of arthritis, growth of microorganisms in the organs and cytokine profile were assessed. Lack of B7-1 was associated with amelioration of arthritis, while worsening of articular lesions was found in B7-2 deficient mice, in comparison to controls. Amelioration of arthritis in B7-1 deficient mice was accompanied by a lower local production of IL-1 β and IL-18, and increase in IL-4 and IL-10 secretion. On the contrary, B7-2 deficient mice showed an higher proinflammatory cytokine production and lower IL-10 secretion than controls. Taken together, our results provide evidence that signaling delivered by B7-1 and B7-2 plays a role in determining the outcome of group B streptococcal induced arthritis, likely due to the different local secretory pattern.     

Novel aspects of fibrin(ogen) fragments during inflammation

Coagulation is fundamental for the confinement of infection and/or the inflammatory response to a limited area. Under pathological inflammatory conditions such as arthritis, multiple sclerosis or sepsis, an uncontrolled activation of the coagulation system contributes to inflammation, microvascular failure and organ dysfunction. Coagulation is initiated by the activation of thrombin, which, in turn, triggers fibrin formation by the release of fibrinopeptides. Fibrin is cleaved by plasmin, resulting in clot lysis and an accompanied generation of fibrin fragments such as D and E fragments. Various coagulation factors, including fibrinogen and/or fibrin [fibrin(ogen)] and also fibrin degradation products, modulate the inflammatory response by affecting leukocyte migration and cytokine production. Fibrin fragments are mostly proinflammatory, however, Bβ15-42 in particular possesses potential antiinflammatory effects. Bβ15-42 inhibits Rho-kinase activation by dissociating Fyn from Rho and, hence prevents stress-induced loss of endothelial barrier function and also leukocyte migration. This article summarizes the state-of-the-art in inflammatory modulation by fibrin(ogen) and fibrin fragments. However, further research is required to gain better understanding of the entire role fibrin fragments play during inflammation and, possibly, disease development.     

猪链球菌分子流行病学研究方法

猪链球菌（Streptococcus suis）是猪重要的细菌性病原,它可以导致猪的脑膜炎、败血症和关节炎等症状,给养猪业带来严重经济损失;同时该菌还可感染人,是一种人畜共患病原菌。应用分子流行病学方法,阐明猪链球菌病的流行病学特征,明确其毒力分型、时空分布、传播途径、传染源,确定传播的遗传决定因素等,将有助于猪链球菌病的防控。目前常用的分子流行病学方法主要有多位点序列分型、脉冲场凝胶电泳、全基因组测序和基于PCR的方法等。本文介绍了上述方法的原理以及在猪链球菌流行病学中的应用,并分析这几种方法的优缺点,从而为更好地揭示猪链球菌流行病学特征、制定猪链球菌病的防控策略提供参考。     

The role of B cell CD22 expression in Staphylococcus aureus arthritis and sepsis

Severe Staphylococcus aureus infections give rise to a pronounced antigen-specific and polyclonal B cell response with elevated serum immunoglobulin levels. However, it has been difficult to correlate the antibody levels with the clinical outcome of sepsis and/or arthritis concerning both protection and pathogenic aspects. Earlier studies have shown that macrophages and neutrophils are of great importance for bacterial clearance. However, deletion of the complete B cell compartment affected neither S. aureus-induced arthritis nor survival. MZ B cells are believed to be of importance for clearance of blood-borne antigens and have been implicated in protection against S. aureus infections. CD22 is a B-cell-specific inhibitory receptor binding to alpha2,6-linked sialic acids, and deficiency in CD22 leads to a 75% reduction of the MZ B cell compartment. CD22-/- mice and congeneic controls were inoculated intravenously with an arthritogenic dose of live S. aureus. No differences between the groups were detected regarding frequency and severity of arthritis, survival, bacterial clearance, or induction of inflammatory response. This study shows explicitly that a reduced MZ B cell compartment in the absence of CD22 expression does not interfere with the inflammatory response during S. aureus infection.     

Immune regulation of bone loss by Th17 cells

A significant macrophage and T-cell infiltrate commonly occurs in inflammatory joint conditions such as rheumatoid arthritis that have significant bone destruction. Cytokines produced by activated macrophages and T cells are implicated in arthritis pathogenesis and are involved in osteoclast-mediated bone resorption. The scope of the present review is to analyze current knowledge and to provide a better understanding of how macrophage-derived factors promote the differentiation of a novel T-helper subset (Th17) that promotes osteoclast formation and activation.     

microRNAs调控脓毒症Toll样受体通路研究进展

脓毒症是重症监护病房(ICU)患者死亡的重要原因。近年来,随着现代医学的发展,脓毒症救治成功率有所提高,但总的死亡例数继续增加,研究脓毒症发生机制及救治策略具有重要的临床意义。目前认为,免疫炎性反应紊乱是脓毒症的重要特征,也是脓毒症患者死亡的根本原因;Toll样受体(TLRs)炎性信号通路失调是脓毒症的重要病理生理机制;micro RNAs(mi RNAs)是其中的关键调控分子,mi RNAs对TLR信号通路组成分子的调控,包括对TLRs、TLR信号蛋白、转录因子、细胞因子及TLR信号通路的调控分子等5个水平。本文综述了近年来micro RNAs调控脓毒症Toll样受体通路的研究进展。     

Genetic Control of Spontaneous Arthritis in a Four-Way Advanced Intercross Line

Identifying the genetic basis of complex diseases, such as rheumatoid arthritis, remains a challenge that requires experimental models to reduce the genetic and environmental variability. Numerous loci for arthritis have been identified in induced animal models; however, few spontaneous models have been genetically studied. Therefore, we generated a four-way advanced intercross line (AIL) from four inbred strains, including BXD2/TyJ which spontaneously develops autoimmune arthritis. A genome-wide scan for spontaneous arthritis was performed in a cohort of 366 mice of the fourth generation (G4) of this cross. Five loci contributing to clinical phenotypes were identified in chromosomes 3, 7, 13, 18, and X. Three of the loci found in this study, confirm previously identified loci; whereas two of them are novel loci. Interesting candidate genes for the loci are highlighted. This study provides a genetic overview of spontaneous arthritis in mice and aids to solve the genetic etiology of rheumatoid arthritis and to gain a better understanding of the disease.     

The role of TNF-alpha in chronic inflammatory conditions, intermediary metabolism, and cardiovascular risk

The recent insight that inflammation contributes to the development of atherosclerosis and type 2 diabetes mellitus constitutes a major breakthrough in understanding the mechanisms underlying these conditions. In addition, it opens the way for new therapeutic approaches that might eventually decrease the prevalence of these public health problems. Tumor necrosis factor-alpha (TNF-alpha) has been shown to play a key role in these processes and thus might be a potential therapeutic target. Increased concentrations of TNF-alpha are found in acute and chronic inflammatory conditions (e.g., trauma, sepsis, infection, rheumatoid arthritis), in which a shift toward a proatherogenic lipid profile and impaired glucose tolerance occurs. Although therapeutic blockade of TNF-alpha worsens the prognosis in patients with abscesses and granulomatous infections, this strategy is highly beneficial in the case of chronic inflammatory conditions, including rheumatoid arthritis. Current investigations assessing the impact of anti-TNF agents on intermediary metabolism suggest that TNF-alpha blockade may improve insulin resistance and lipid profiles in patients with chronic inflammatory diseases.