大麻素受体1在慢性乙型肝炎肝纤维化发生和发展中的作用

Sato等[1]和Teixeira Clerc等[2]先后发现大麻素受体1(CB1R)在慢性肝病发展过程中起着独特作用.为深入研究CB1R在慢性乙型肝炎(CHB)肝纤维化发生、发展过程中的作用,我们用免疫组织化学染色法检测肝组织中CB1R表达情况,分析CB1R半定量评分与纤维化分期、血清转化生长因子(TGF)β1、ALT以及HBV DNA水平等指标的相关性,为今后以CB1R为靶点进行抗肝纤维化治疗提供依据.     

Up regulated expression of fractalkine/CX3CL1 and CX3CR1 in patients with systemic sclerosis

BACKGROUND: Fractalkine expressed on endothelial cells mediates activation and adhesion of leucocytes expressing its receptor, CX(3)CR1. Soluble fractalkine exhibits chemotactic activity for leucocytes expressing CX(3)CR1. OBJECTIVE: To determine the role of fractalkine and its receptor in systemic sclerosis (SSc) by assessing their expression levels in patients with this disease. METHODS: The expression of fractalkine and CX(3)CR1 in the skin and lung tissues was immunohistochemically examined. Circulating soluble fractalkine levels were examined by enzyme linked immunosorbent assay (ELISA). Blood samples from patients with SSc were stained for CX(3)CR1 with flow cytometric analysis. RESULTS: CX(3)CR1 levels on peripheral monocytes/macrophages and T cells were found to be raised in patients with diffuse cutaneous SSc. The numbers of cells expressing CX(3)CR1, including monocytes/macrophages, were increased in the lesional skin and lung tissues from patients with diffuse cutaneous SSc. Fractalkine was strongly expressed on endothelial cells in the affected skin and lung tissues. Soluble fractalkine levels were significantly raised in sera and were associated with raised erythrocyte sedimentation rates, digital ischaemia, and severity of pulmonary fibrosis. CONCLUSIONS: Up regulated expression of fractalkine and CX(3)CR1 cooperatively augments the recruitment of mononuclear cells expressing CX(3)CR1 into the affected tissue of SSc, leading to inflammation and vascular injury.     

Polymorphism in the fractalkine receptor CX3CR1 as a genetic risk factor for coronary artery disease

Coronary atherosclerosis is a major cause of death in industrialized countries. Monocytes, which play a key role in atherosclerosis, migrate into the vessel wall, presumably guided by specific chemoattractant and adhesion molecules. A compelling candidate for this role is the chemokine receptor CX3CR1, which is expressed on monocytes and acts as either a chemotactic receptor or an adhesion molecule, depending on whether its ligand, fractalkine, is presented free or membrane bound. A common variant of CX3CR1 was recently identified, encoded by the alleles I249 and M280, which form a common I(249)M(280) haplotype. When CX3CR1 genotypes were analyzed in 151 patients with acute coronary syndromes and in 249 healthy controls, CX3CR1 I249 heterozygosity was associated with a markedly reduced risk of acute coronary events, independent of established acquired coronary risk factors (eg, smoking, diabetes). The adjusted odds ratio for this allele was 0.43 (95% confidence interval, 0.26-0.72; P =.001). Consistent with this, functional analysis of peripheral blood mononuclear cells showed that CX3CR1 I249 heterozygosity was associated with a significant decrease in the number of fractalkine binding sites per cell. The results show that CX3CR1 I249 is an independent genetic risk factor for coronary artery disease and that CX3CR1 may be involved in the pathogenesis of atherosclerotic disease. (Blood. 2001;97:1925-1928)     

Increased expression of fractalkine (CX3CL1) and its receptor, CX3CR1, in Wegener's granulomatosis--possible role in vascular inflammation

OBJECTIVE: Based on the function of fractalkine (CX3CL1), the unique member of the CX3C chemokine subfamily, in endothelial-related inflammation, we hypothesized a role for CX3CL1 and its receptor (CX3CR) in Wegener's granulomatosis (WG). In the present study, this hypothesis was tested by different experimental approaches. METHODS: We examined plasma levels of CX3CL1 (enzyme immunoassay) and CX3CR1 expression in peripheral blood mononuclear cells (PBMCs) (real-time quantitative RT-PCR and flow cytometry) in 18 WG patients and 15 healthy controls. In eight of these individuals, we also examined CX3CR1-mediated chemotaxis and adhesion in T cells and monocytes as well as the effects of CX3CL1 on monocyte chemoattractant protein (MCP) 1 levels in PBMC supernatants. RESULTS: Our main findings were: (i) WG patients had markedly increased plasma levels of CX3CL1, with particularly high levels in those with active disease, (ii) These increased CX3CL1 levels were accompanied by enhanced expression of its corresponding receptor, CX3XR1, in PBMC, primarily reflecting an increased proportion of CX3CR1(+)CD3(+)CD4(+) T cells and (iii) The up-regulation of CX3CR1 in PBMC from WG patients affected their functional potential as shown by CX3CL1-induced enhancement of chemotaxis, adhesion, responses as well as MCP-1 stimulation. CONCLUSION: Based on the ability of CX3CL1 to promote leucocyte infiltration into the vessel wall of inflammatory levels, it is tempting to hypothesize that increased CX3CL1/CX3CR1 interaction could be involved in the pathogenesis of the granulomatous vasculitis characterizing WG.     

Noninvasive assessment of liver fibrosis in chronic hepatitis C infection

Hepatic fibrogenesis is a dynamic process that reflects a balance between matrix synthesis and degradation. An accurate determination of hepatic fibrosis is important in determining prognosis, requirement for therapy, and disease progression in chronic hepatitis C infection. Histologic assessment relies on a liver biopsy, an invasive procedure associated with sampling error and inaccurate staging that provides only a semiquantitative and static measure of fibrosis and inflammatory activity. Several noninvasive tools initially developed and validated in chronic hepatitis C patients are now being applied to other chronic liver disease states. These noninvasive approaches include simple and complex serum biochemical marker algorithms, radiologic methods such as elastography, and emerging genomics and proteomics technologies. In the future, the combination of these diagnostic modalities likely will provide a more accurate and reliable measure of disease severity in chronic liver disease patients.     

The disintegrin-like metalloproteinase ADAM10 is involved in constitutive cleavage of CX3CL1 (fractalkine) and regulates CX3CL1-mediated cell-cell adhesion

The CX3C chemokine fractalkine (CX3CL1) exists as a membrane-expressed protein promoting cell-cell adhesion and as a soluble molecule inducing chemotaxis. Transmembrane CX3CL1 is converted into its soluble form by defined proteolytic cleavage (shedding), which can be enhanced by stimulation with phorbol-12-myristate-13-acetate (PMA). PMA-induced CX3CL1 shedding has been shown to involve the tumor necrosis factor-alpha-converting enzyme (TACE), whereas the constitutive cleavage in unstimulated cells remains elusive. Here we demonstrate a role of the closely related disintegrin-like metalloproteinase 10 (ADAM10) in the constitutive CX3CL1 cleavage. The hydroxamate GW280264X, capable of blocking TACE as well as ADAM10, proved to be an effective inhibitor of the constitutive and the PMA-inducible CX3CL1 cleavage in CX3CL1-expressing ECV-304 cells (CX3CL1-ECV-304), whereas GI254023X, preferentially blocking ADAM10 but not TACE, reduced the constitutive cleavage only. Overexpression of ADAM10 in COS-7 cells enhanced constitutive cleavage of CX3CL1 and, more importantly, in murine fibroblasts deficient of ADAM10 constitutive CX3CL1 cleavage was markedly reduced. Thus, ADAM10 contributes to the constitutive shedding of CX3CL1 in unstimulated cells. Addressing the functional role of CX3CL1 shedding for the adhesion of monocytic cells via membrane-expressed CX3CL1, we found that THP-1 cells adhere to CX3CL1-ECV-304 cells but detach in the course of vigorous washing. Inhibition of ADAM10-mediated CX3CL1 shedding not only increased adhesive properties of CX3CL1-ECV-304 cells but also prevented de-adhesion of bound THP-1 cells. Our data demonstrate that ADAM10 is involved in the constitutive cleavage of CX3CL1 and thereby may regulate the recruitment of monocytic cells to CX3CL1-expressing cell layers.     

Interferon-alpha and liver fibrosis in patients with chronic damage due to hepatitis C virus

The present review focuses on the published information published regarding the effects of interferon alpha therapy on liver fibrosis in patients with chronic liver damage secondary to hepatitis C infection. Data reviewed included results of the in vitro effects of interferon on hepatic cell line cultures with regards to indirect markers of fibrosis, activation of hepatic stellate cells and oxidative stress response. In the clinical arena, there is current clear evidence of a favorable histological outcome in patients with sustained viral response to interferon therapy. For this reason, the current review focuses more on the histological outcomes regarding liver fibrosis in patients who have not attained viral response to therapy (non-responders) or who already have biopsy defined cirrhosis. Data in these patients were analyzed according to the results of objective testing of fibrosis through the assessment of liver biopsy and its change during time, specially because the morbidity and mortality of this disease is directly related to the complications of liver cirrhosis and not necessarily to the persistence of the hepatitis C virus. Lastly, it is concluded that the process of liver fibrosis/cirrhosis is a dynamic one and that there is some evidence to support the usefulness of interferon alpha therapy as a means to halt or retard the progression of hepatic fibrosis. The result of current clinical trials in which interferon therapy is being used to modify the progression of fibrosis in non-responders or cirrhotic patients is eagerly awaited.     

Serum hyaluronic acid is a useful marker of liver fibrosis in chronic hepatitis C virus infection

Patients with chronic hepatitis C virus (HCV) infection are often asymptomatic with few clinical signs of liver disease. Recognition of the presence of fibrosis or cirrhosis is difficult without liver biopsy, but with the availability of effective treatments, such as interferon, and the potential for progression to hepatoma in some cases, an accurate measure of the stage of disease is important. Serum hyaluronic acid (HA) has been identified as a potential marker of fibrosis or cirrhosis in other settings. In a prospective study in 130 chronic HCV carriers therefore, serum HA concentrations were compared with conventional liver function tests (including alanine aminotransferase (ALT), a-glutathione-S transferase (GST) and serum HCV RNA in order to determine which identified the stage of liver fibrosis as assessed by liver biopsy most accurately. The median HA concentrations according to the stage of fibrosis 0, 1&2, 3 and 4&5 were 17gl^–1 (range 5– 37), 17gl^–1 (5–80), 30gl^–1 (10–105) and 350gl^–1 (20–800) respectively. The median HA concentration in stage 4&5 was significantly greater than in stages 0, 1&2 or 3. Serum HA concentration rose with age, but even when adjusted for age the median HA at stage 4&5 was greater than all other groups (95% CI of difference between the medians exceeded 0). Thus, serum HA gave a sensitivity and specificity for stage 4&5 fibrosis of 85% and 88% respectively, exceeding those for ALT or GST. In contrast, serum ALT or GST levels were not correlated with the stage of fibrosis although ALT was significantly greater in the cirrhotic group when compared to the group with no fibrosis (stage 0). There was no correlation between serum HA and either the grade of inflammatory changes or serum HCV RNA. These results suggest that serum hyaluronic acid is a useful marker of liver fibrosis in patients with chronic HCV infection. It could therefore be used to monitor patients at risk of progressive fibrosis, in controlled clinical trials, as a measure of response to antifibrotic therapy and in those in whom liver biopsy is difficult or contraindicated.     

Role for neuronally derived fractalkine in mediating interactions between neurons and CX3CR1-expressing microglia

A recently identified chemokine, fractalkine, is a member of the chemokine gene family, which consists principally of secreted, proinflammatory molecules. Fractalkine is distinguished structurally by the presence of a CX3C motif as well as transmembrane spanning and mucin-like domains and shows atypical constitutive expression in a number of nonhematopoietic tissues, including brain. We undertook an extensive characterization of this chemokine and its receptor CX3CR1 in the brain to gain insights into use of chemokine-dependent systems in the central nervous system. Expression of fractalkine in rat brain was found to be widespread and localized principally to neurons. Recombinant rat CX3CR1, as expressed in Chinese hamster ovary cells, specifically bound fractalkine and signaled in the presence of either membrane-anchored or soluble forms of fractalkine protein. Fractalkine stimulated chemotaxis and elevated intracellular calcium levels of microglia; these responses were blocked by anti-CX3CR1 antibodies. After facial motor nerve axotomy, dramatic changes in the levels of CX3CR1 and fractalkine in the facial nucleus were evident. These included increases in the number and perineuronal location of CX3CR1-expressing microglia, decreased levels of motor neuron-expressed fractalkine mRNA, and an alteration in the forms of fractalkine protein expressed. These data describe mechanisms of cellular communication between neurons and microglia, involving fractalkine and CX3CR1, which occur in both normal and pathological states of the central nervous system.     

The CX3C chemokine fractalkine mediates platelet adhesion via the von Willebrand receptor glycoprotein Ib

The membrane-anchored CX3C chemokine fractalkine (FKN) is expressed on activated endothelium and is associated with the development of atherosclerosis. The potential of FKN in mediating platelet adhesion beyond platelet activation remains unexplored to date. A flow-based adhesion assay was used to study the adhesion of platelets to immobilized FKN under physiologic flow conditions. Platelet adhesion to von Willebrand factor (VWF) was increased in the presence of FKN at 600 inverse seconds. Additional platelet adhesion to FKN coimmobilized with VWF was dependent on the FKN receptor CX3CR1 and activation of glycoprotein (GP) IIb/IIIa. The number of platelets rolling on VWF was likewise enhanced in the presence of FKN. The enhancement of rolling on FKN and VWF was insensitive to anti-CX3CR1 antibody but was fully inhibited by neutralizing GPIbα function. The extracellular domain of GPIbα was covalently coupled to fluorescent microspheres, and microsphere binding was significantly higher in the presence of FKN. Platelet adhesion to activated endothelium in vitro and to intact human arteries was substantially increased in an FKN-dependent manner. These data demonstrate that endothelial expressed FKN activates platelets via its cognate receptor CX3CR1, whereas platelet adhesion is predominantly mediated by GPIbα and independent of CX3CR1.     

Intestinal CX3C chemokine receptor 1(high) (CX3CR1(high)) myeloid cells prevent T-cell-dependent colitis

Adequate activation of CD4(+) T lymphocytes is essential for host defense against invading pathogens; however, exaggerated activity of effector CD4(+) T cells induces tissue damage, leading to inflammatory disorders such as inflammatory bowel diseases. Several unique subsets of intestinal innate immune cells have been identified. However, the direct involvement of innate immune cell subsets in the suppression of T-cell-dependent intestinal inflammation is poorly understood. Here, we report that intestinal CX(3)C chemokine receptor 1(high) (CX(3)CR1(high)) CD11b(+) CD11c(+) cells are responsible for prevention of intestinal inflammation through inhibition of T-cell responses. These cells inhibit CD4(+) T-cell proliferation in a cell contact-dependent manner and prevent T-cell-dependent colitis. The suppressive activity is abrogated in the absence of the IL-10/Stat3 pathway. These cells inhibit T-cell proliferation by two steps. Initially, CX(3)CR1(high) CD11b(+) CD11c(+) cells preferentially interact with T cells through highly expressed intercellular adhesion molecule-1/vascular cell adhesion molecule-1; then, they fail to activate T cells because of defective expression of CD80/CD86. The IL-10/Stat3 pathway mediates the reduction of CD80/CD86 expression. Transfer of wild-type CX(3)CR1(high) CD11b(+) CD11c(+) cells prevents development of colitis in myeloid-specific Stat3-deficient mice. Thus, these cells are regulatory myeloid cells that are responsible for maintaining intestinal homeostasis.     

Fractalkine及其受体CX3CR1与脑血管病

Fractalkine是趋化因子家族的新成员,以膜结合形式和可溶性形式存在,兼有黏附分子和趋化因子的活性.CX3CR1是其特异性受体,二者在神经系统的诸多疾病中均有表达.目前,fractalkine其受体CX3CR1的基因多态性与脑血管病的研究,主要涉及脑血管病的危险因素、脑缺血再灌注及骨髓干细胞移植等方面,有望成为临床治疗的新靶点.     

CX3CL1/fractalkine is released from apoptotic lymphocytes to stimulate macrophage chemotaxis

Cells undergoing apoptosis are efficiently located and engulfed by phagocytes. The mechanisms by which macrophages, the professional scavenging phagocytes of apoptotic cells, are attracted to sites of apoptosis are poorly defined. Here we show that CX3CL1/fractalkine, a chemokine and intercellular adhesion molecule, is released rapidly from apoptotic lymphocytes, via caspase- and Bcl-2-regulated mechanisms, to attract macrophages. Effective chemotaxis of macrophages to apoptotic lymphocytes is dependent on macrophage fractalkine receptor, CX3CR1. CX3CR1 deficiency caused diminished recruitment of macrophages to germinal centers of lymphoid follicles, sites of high-rate B-cell apoptosis. These results provide the first demonstration of chemokine/chemokine-receptor activity in the navigation of macrophages toward apoptotic cells and identify a mechanism by which macrophage infiltration of tissues containing apoptotic lymphocytes is achieved.     

The severity of liver fibrosis is associated with high leptin levels in chronic hepatitis C

Summary.  Recent attention has focused on the liver profibrogenic role of leptin in animal models. The purpose of this study was to evaluate the role of leptin and TNF- α in the severity of liver fibrosis in patients with chronic hepatitis C (CHC). We used a radioimmunoassay to determine serum leptin concentrations in 77 consecutive patients with CHC and 22 healthy controls. Leptin was correlated with liver histological (METAVIR) and metabolic indices. Sixty five patients had none to moderate liver fibrosis (F0-F2) and twelve severe fibrosis (F3-F4). Steatosis was observed in all but 27 patients. Leptin was significantly increased in patients compared with controls and was significantly more elevated in females both in patients and controls. The age, age at infection, prothrombin index, body mass index (BMI), triglycerides, glycaemia, ferritin, leptin and TNF- α , were associated with severe fibrosis. Steatosis was significantly more pronounced in patients with severe than those without or moderate fibrosis ( P  = 0.04). Only leptin was significantly and independently associated with severe fibrosis (OR = 1.2, CI 95%: 1.1–1.4, P  = 0.03). Leptin was significantly associated with BMI ( r  = 0.64, P  < 0.001) and glycaemia ( r  = 0.43, P  < 0.001). Significant correlations were found between steatosis and BMI ( r  = 0.30, P  < 0.01) and glycaemia ( r  = 0.30, P  < 0.01). In patients with CHC and higher BMI and glycaemia levels, the severity of liver fibrosis is associated with serum leptin. TNF- α is a putative candidate involved in the mechanism.     

Routine blood tests to predict liver fibrosis in chronic hepatitis C

AIM: To verify the usefulness of FibroQ for predicting fibrosis in patients with chronic hepatitis C, compared with other noninvasive tests.METHODS: This retrospective cohort study included 237 consecutive patients with chronic hepatitis C who had undergone percutaneous liver biopsy before treatment. FibroQ, aspartate aminotransferase (AST)/alanine aminotransferase ratio (AAR), AST to platelet ratio index, cirrhosis discriminant score, age-platelet index (API), Pohl score, FIB-4 index, and Lok’s model were calculated and compared.RESULTS: FibroQ, FIB-4, AAR, API and Lok’s model results increased significantly as fibrosis advanced (analysis of variance test: P < 0.001). FibroQ trended to be superior in predicting significant fibrosis score in chronic hepatitis C compared with other noninvasive tests.CONCLUSION: FibroQ is a simple and useful test for predicting significant fibrosis in patients with chronic hepatitis C.