Modulation of soluble and membrane-bound TNF-induced phenotypic and functional changes of human brain microvascular endothelial cells by recombinant TNF binding protein I

Exploiting microglial and peripheral immune cell crosstalk to treat Alzheimer's disease

Neuroinflammation is considered one of the cardinal features of Alzheimer’s disease (AD). Neuritic plaques composed of amyloid β and neurofibrillary tangle-laden neurons are surrounded by reactive astrocytes and microglia. Exposure of microglia, the resident myeloid cell of the CNS, to amyloid β causes these cells to acquire an inflammatory phenotype. While these reactive microglia are important to contain and phagocytose amyloid plaques, their activated phenotype impacts CNS homeostasis. In rodent models, increased neuroinflammation promoted by overexpression of proinflammatory cytokines can cause an increase in hyperphosphorylated tau and a decrease in hippocampal function. The peripheral immune system can also play a detrimental or beneficial role in CNS inflammation. Systemic inflammation can increase the risk of developing AD dementia, and chemokines released directly by microglia or indirectly by endothelial cells can attract monocytes and T lymphocytes to the CNS. These peripheral immune cells can aid in amyloid β clearance or modulate microglia responses, depending on the cell type. As such, several groups have targeted the peripheral immune system to modulate chronic neuroinflammation. In this review, we focus on the interplay of immunomodulating factors and cell types that are being investigated as possible therapeutic targets for the treatment or prevention of AD.

The Cancer Chemotherapy Drug Etoposide (VP-16) Induces Proinflammatory Cytokine Production and Sickness Behavior–like Symptoms in a Mouse Model of Cancer Chemotherapy–Related Symptoms

Cancer chemotherapy–related symptoms such as fatigue, malaise, loss of interest in social activities, difficulty concentrating, and changes in sleep patterns can lead to treatment delays, dose reductions, or termination and have a profound effect on the physical, psychosocial, and economic aspects of quality of life. Clinicians have long suspected that these symptoms are similar to those associated with “sickness behavior,” which is triggered by the production of the inflammatory cytokines IL-1β, TNF-α, and IL-6 by macrophages and other cells of the innate immune system in response to immune challenge. The p38 mitogen-activated protein kinase (p38 MAPK) plays a central role in the production of these cytokines and consequently the induction of sickness behavior. Several cancer chemotherapy drugs have been shown to activate p38 MAPK, but whether these drugs can also induce the production of inflammatory cytokines to cause sickness behavior is unknown. The aim of this study was to determine whether the cancer chemotherapy drug etoposide (VP-16), which is known to activate p38 MAPK, could induce inflammatory cytokine production by murine macrophages and sickness-like behaviors when injected into mice. VP-16 activated p38 MAPK and induced IL-6 production in murine macrophages in a p38 MAPK– dependent manner. VP-16 administration rapidly increased serum levels of IL-6 in healthy mice and induced sickness-like behaviors as evidenced by a decrease in food intake, body weight, hemoglobin level, and voluntary wheel-running activity. These findings support the idea that the induction of IL-1β, TNF-α, and IL-6 by cancer chemotherapy drugs underlies the fatigue and associated symptoms experienced by people undergoing cancer chemotherapy.

Clinical development of onercept, a tumor necrosis factor binding protein, in psoriasis

BACKGROUND

Tumor necrosis factor (TNF)-α plays a critical role in psoriasis pathogenesis, and several anti-TNF agents have been developed as therapeutic drugs in this indication.

SCOPE

To present the preclinical rationale and clinical data for onercept, a novel anti-TNF agent developed for the treatment of moderate-to-severe psoriasis, and to critically evaluate the onercept clinical development program.

FINDINGS

Onercept was shown in preclinical studies to inhibit TNF-α and suppress clinical signs in several inflammatory conditions. In phase II studies onercept demonstrated a therapeutic benefit in psoriasis and psoriatic arthritis and no safety issues were identified. Based on these results, a phase III program comprising three multicenter, randomized, double-blind, placebo-controlled studies examining onercept in moderate-to-severe plaque psoriasis was initiated. Following the occurrence of two cases of systemic inflammatory response syndrome (SIRS) and lower than expected efficacy results, an independent Data Safety Monitoring Board (DSMB) determined that the risk-benefit ratio was not sufficiently favorable to justify continued development, and all clinical studies were promptly terminated. Although not initially diagnosed as such by the investigators, two further SIRS events were reported, one after study discontinuation. Although an increased incidence of infection and sepsis-like events has been associated with other anti-TNF therapies, an increased risk of infection was not observed with onercept treatment. Moreover, no infectious etiology was determined in the SIRS cases. The data suggest that the SIRS reactions were due to a systemic inflammatory response.

CONCLUSIONS

Despite promising early clinical results, onercept showed many of the expected risks associated with other anti-TNF agents and proved not to have an exceptional efficacy and safety profile. The clinical development of onercept highlights the critical importance of DSMBs and closely monitoring patient safety and evaluating risk-benefit profiles in large clinical programs.

Peripheral T cells derived from Alzheimer's disease patients overexpress CXCR2 contributing to its transendothelial migration, which is microglial TNF-alpha-dependent

The mechanism of circulating T cells entry into the brain in Alzheimer's diseases (AD) remains unclear. Here, we showed that peripheral T cells derived from AD patients overexpress CXCR2 to enhance its transendothelial migration. T cells migration through in vitro blood-brain barrier model was effectively blocked by anti-CXCR2 antibody or IL-8 (a CXCR2 ligand) RNAi in human brain microvascular endothelial cells (HBMECs). Amyloid beta (Abeta) injection in rat hippocampus upregulated CXCR2 expression accompanied with increased T cells occurrence in the brain, and this enhanced T cells entry was effectively blocked by CXCR2 antagonist. Furthermore, anti-TNF-alpha antibody blocked IL-8 production in HBMECs and T cells transendothelial migration caused by the culture supernatant of microglia treated with Abeta. Blockage of intracerebral TNF-alpha abolished the upregulation of CXCR2 in peripheral T cells and the increased T cells occurrence in the brain induced by Abeta injection in rat hippocampus. These data suggest that CXCR2 overexpression in peripheral T cells is intracerebral microglial TNF-alpha-dependent and TNF-alpha primes T cells transendothelial migration in Alzheimer's diseases.

Therapeutic potential of selectin antagonists in psoriasis

Psoriasis is a systemic chronic inflammatory disorder. One of the major characteristics is an excess of infiltration of inflammatory cells, mainly lymphocytes, into the skin. Because the adhesion family of selectins is suggested to play a relevant role in this process, selectins have emerged as an interesting target for drug discovery and development in psoriasis. Different strategies targeting selectins have been described. This review discusses these approaches and summarises the current development of selectin antagonists for the treatment of psoriasis. An expert opinion will give the authors' personal opinion about selectin antagonism in psoriasis and which approach might be preferable.

The importance of T cell interactions with macrophages in rheumatoid cytokine production

The analysis of suppression of cytokines in rheumatoid synovial tissue and fluid pioneered the studies of human cytokines in diseased tissue due to the relative ease of staining samples, even at the height of the inflammatory process. These studies led to the study of synovial cytokine regulation, and the identification of TNF as a therapeutic target, which has been amply validated in clinical trials and now routine therapy. The next key question was how is TNF disregulated in synovium. Are there differences between the mechanisms of synovial TNF production compared to the production of protective TNF during an immune response? Are there differences between the induction of the pro-inflammatory TNF and the anti inflammatory IL-10? The analysis of the interaction of the two most abundant synovial cells, T lymphocytes and macrophages has provided interesting clues to new therapeutic approaches based on disrupting T-macrophage interaction.

[TNF-alpha inhibitors in inflammatory bowel disease]

Inflammatory bowel disease (IBD) is a chronic immunoinflammatory response to an stimulus that activates a chain of cellular mediators causing intestinal damage. One of the most well recognized proinflammatory mediators involved in the pathogenesis of IBD is tumor necrosis factor alpha (TNFalpha). The treatment of IBD has advanced in parallel to the improvement of the knowledge of its physiopathology, leading to the development of biological therapies. An example of this kind of treatment is the use of substances that antagonize TNFalpha, such as monoclonal antibodies infliximab, adalimumab, natalizumab, etanercept or onercept, with infliximab being the unique approved for use in IBD. Several studies have demonstrated that inhibition of TNFalpha is useful in the treatment of Crohn's disease (CD). In CD, infliximab induces the remission of relapses which are refractory to the conventional treatment, prevents more relapses and induces a closure of enterocutaneous and perianal fistula that do not respond to first line treatment. However, infliximab is not useful in ulcerative colitis. Infliximab treatment has some drawbacks, such as the development of anti-infliximab antibodies, which cause a loss of efficacy of the treatment and hypersensitivity reactions. Other reported adverse effects of infliximab are the development of autoimmunity, such as that related with antinuclear or anti-DNA antibodies, or the reactivation of infections such as tuberculosis. In fact, a screening for tuberculosis is necessary before administration of infliximab. To reduce the adverse effects due to infliximab immunogenicity, several trials with humanized or completely human agents, such as adalimumab or onercept, are under way. Until the precise stimulus that triggers IBD is identified, biological therapies have a great future and the selective antagonism of TNFalpha is already a reality.

The process of identifying and understanding cytokines: from basic studies to treating rheumatic diseases

This is a historical overview seen from a personal angle. It covers the insights made during the past 20 years into the destructive processes of rheumatoid arthritis (RA) related to cytokines. The biochemical knowledge of the matrix components (i.e. collagen) and enzymology (i.e. collagenase) available in the 1950s led to the identification of cells from synovial tissue producing collagenase (fibroblast-like cells) and their interaction with other immune cells, i.e. monocyte-macrophages (Mphi) and lymphocytes (1976-1979). This insight led to the isolation of soluble factors produced by Mphi, such as interleukin-1 (IL-1) and TNF, the principal cytokines inducing collagenase and PGE(2) in many target cells (i.e. synovial fibroblasts, chondrocytes, bone-derived cells) (1981-1985). Further advances resulted from observations that, in clinical conditions (i.e. leukaemia, juvenile RA), a remission of fever and inflammation may occur spontaneously and that tissue catabolism may persist despite the absence of systemic inflammation; this gave rise to the concept and identification of endogenous cytokine inhibitors (i.e. IL-1 receptor antagonist and TNF soluble receptor) (1984-1989). The fourth milestone was the observation that the production of IL-1 and TNF by Mphi was induced mainly by direct contact with lymphocytes, prompting studies of the ligands and counter-ligands on Mphi and lymphocytes as well as inhibitors involved in this cell-cell contact, some of these inhibitors being involved in lipid metabolism and acute-phase proteins (HDL-apo A-1).

Treatment of active Crohn's disease with onercept (recombinant human soluble p55 tumour necrosis factor receptor): results of a randomized, open-label, pilot study

BACKGROUND

Monoclonal antibodies to the pro-inflammatory cytokine tumour necrosis factor-alpha have shown efficacy in treating Crohn's disease, but can be immunogenic. Soluble tumour necrosis factor-binding proteins are being studied as potential alternative anti-tumour necrosis factor agents in Crohn's disease.

AIM

To investigate the safety and efficacy of onercept, a recombinant form of the natural human soluble p55 tumour necrosis factor receptor, in the treatment of patients with active Crohn's disease.

METHODS

In a pilot study, 12 patients with active Crohn's disease were randomized to receive onercept at either 11.7 or 50 mg three times weekly for 2 weeks. Patients were followed up for 6 months after the end of treatment.

RESULTS

The Crohn's disease activity index decreased rapidly during treatment in both groups. Seven responses (Crohn's disease activity index decrease of 100 points) were observed over the first 6 weeks of the study, including five remissions (Crohn's disease activity index decrease of 150 points). Improvement was sustained for 2-4 months after stopping treatment. Treatment was well tolerated. No patients developed antibodies to onercept.

CONCLUSIONS

Neutralizing the activity of tumour necrosis factor-alpha with its soluble p55 receptor may be valuable in the treatment of patients with Crohn's disease. Larger placebo-controlled trials are indicated.

The saga of the discovery of IL-1 and TNF and their specific inhibitors in the pathogenesis and treatment of rheumatoid arthritis

In the seventies, the molecule subsequently termed IL-1 was among the first cytokines to attract the attention of rheumatologists due to its biological role in tissue destruction and bone resorption. In the mid-eighties, cachectin/tumor necrosis factor was found to share some of these biological activities, and a strong synergism between the two cytokines became evident. While IL-1 appeared to be more important at the local level, TNF played a more prominent part at the systemic level. In 1984, we became aware of the existence of an antagonist to IL-1 - subsequently termed IL-1Ra (interleukin-1 receptor antagonist) - in urine of febrile patients; its mechanism of action was elucidated in 1987 and the molecule cloned in 1990. The natural inhibitors of TNF were identified in 1996/97 by different investigators and proved to be soluble fragments of the TNF receptor. A concept commonly accepted at present is that disease activity and clinical outcome are controlled by the balance between agonistic and antagonistic cytokines, and at present the principal goal is to understand the underlying mechanisms. This concept is illustrated by observations in numerous animal models. The control of IL-1 and TNF is strongly dependent on the contact between activated lymphocytes and monocytes, the main source of these cytokines. Inhibiting this interaction by interfering with ligands and counter-ligands may be a useful approach if it is possible to maintain the production of the cytokine antagonist. Apolipoproteins A-I and A-II as well as beta2-integrins are molecules that block ligand/counter-ligand interaction. According to animal experiments and clinical data, blocking either IL-1 or TNF, or both, is beneficial. However, to determine not only the benefit but also the side effects of combination therapy in the human system, long-term clinical trials will be required.

Cytokine regulation in RA synovial tissue: role of T cell/macrophage contact-dependent interactions

Several groups have documented the expression of cytokines in rheumatoid arthritis synovial tissue over the past 15 years or so. These studies have indicated that most cytokines examined are expressed at the mRNA levels at least, and many other cytokines are found in abundance as proteins. Our attention has recently focused on the mechanisms that induce and regulate tumour necrosis factor and IL-10. Other workers and ourselves have found that cell-cell contact is an important signal for the induction of cytokines, and our work has demonstrated that tumour necrosis factor and IL-10 production in rheumatoid arthritis synovial joint cells cultures is dependent on T cell/macrophage interaction. In this chapter, we review recent advances in this area and also highlight areas where new therapeutic intervention opportunities arise.

Cytoadhesion of Plasmodium falciparum ring-stage-infected erythrocytes

A common pathological characteristic of Plasmodium falciparum infection is the cytoadhesion of mature-stage-infected erythrocytes (IE) to host endothelium and syncytiotrophoblasts. Massive accumulation of IE in the brain microvasculature or placenta is strongly correlated with severe forms of malaria. Extensive binding of IE to placental chondroitin sulfate A (CSA) is associated with physiopathology during pregnancy. The adhesive phenotype of IE correlates with the appearance of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) at the erythrocyte surface (approximately 16 h after merozoite invasion), so that only early blood-stage (ring-stage) IE appear in the peripheral blood. Here, we describe results that challenge the existing view of blood-stage IE biology by demonstrating the specific adhesion of IE, during the early ring-stage, to endothelial cell lines from the brain and lung and to placental syncytiotrophoblasts. Later, during blood-stage development of these IE, trophozoites switch to an exclusively CSA cytoadhesion phenotype. Therefore, adhesion to an individual endothelial cell or syncytiotrophoblast may occur throughout the blood-stage cycle, indicating the presence in malaria patients of noncirculating (cryptic) parasite subpopulations. We detected two previously unknown parasite proteins on the surface of ring-stage IE. These proteins disappear shortly after the start of PfEMP1-mediated adhesion.

Decomplementation with cobra venom factor prolongs survival of xenografted islets in a rat to mouse model

Although the involvement of complement in hyperacute rejection of xenotransplants is well recognized, its role in rejection of devascularized xenografts, such as pancreatic islets, is not completely understood. In this study, we investigated whether complement participates in the immunopathology of xeno-islet transplantation in a concordant rat to mouse model. Rat pancreatic islets were implanted under the kidney capsule of normal and cobra venom factor (CVF)-decomplementized diabetic C57BL/6 mice. Graft survival was monitored by blood glucose levels. Deposition of IgM and C3 on grafted islets in vivo or on isolated islets in vitro (after incubation with normal and decomplementized mouse serum), as well as CD4- and CD8-positive leucocyte infiltration of grafts, was checked by immunohistochemistry. In addition, complement-mediated cytotoxicity on rat islet cells was evaluated by a 3-(4, 5-dimethythiazolyl)-2.5-diphenyl-2H-tetrazolium-bromide (MTT) assay. A significant C3 deposition was found on grafted islets from the first day after transplantation in vivo, as well as on isolated islets after incubation with mouse serum in vitro. By MTT assay, complement-mediated cytotoxicity for islet cells was found. Decomplementation by CVF decreased C3 deposition on either isolated or grafted islets, delayed CD4- and CD8-positive leucocyte infiltration, led to significant inhibition of complement-mediated cytotoxicity for islet cells, and prolonged graft survival (mean survival time 21.3 versus 8.5 days; P<0.01). Our results indicate that decomplementation can prolong the survival time of devascularized xenografts across concordant species. The deposition of complement on transplanted islets may contribute to xenograft rejection by direct cytotoxicity and by promoting leucocyte infiltration.

Central nervous system vasculitis

Central nervous system vasculitis occurs in a variety of clinical settings. Some exhibit a distinct age preference; others a tissue tropism. Most frequently encountered are giant cell arteritis (temporal arteritis) and vasculitis secondary to infections. The central nervous system may be involved in the antineutrophil cytoplasmic antibody-associated systemic vasculitides and occasionally neurologic abnormalities appear as a presenting manifestation of disease. Isolated angiitis of the central nervous system, a rare form of vasculitis that is restricted to the central nervous system, must be distinguished from other causes of central nervous system inflammation and from noninflammatory vascular disease. We are learning a great deal about the cellular mechanisms of vascular inflammation in general. Some manifestations of the clinical disease result from histologic features of the infiltrate and the size of affected vessel. However, the local consequences of inflammation, such as increased coagulation and altered vasomotor tone, as well as the systemic consequences, such as activation of the central noradrenergic systems, trigeminovascular system, and hypothalamic pituitary adrenal axis, contribute both to pathogenesis of disease and to recovery.