Pierre-François Piguet

The inducing role of tumor necrosis factor in the development of bactericidal granulomas during BCG infection

Granuloma formation in the liver of mice infected with BCG coincides with local TNF synthesis. Injection of rabbit anti-TNF antibody, after 1 or 2 weeks of infection, dramatically interferes with the development of granulomas (both in number and size, large epithelioid cells failing to appear) and subsequent mycobacterial elimination. Furthermore, fully developed BCG granulomas, after 3 weeks of infection, rapidly regress after anti-TNF treatment. Antibody treatment also prevents or suppresses accumulation of TNF mRNA and protein, which resumes after disappearance of the antibody. Peritoneal macrophages exposed to TNF transiently accumulate TNF mRNA, and show an enhanced increase in TNF mRNA in response to gamma interferon. We propose that TNF released from macrophages in the microenvironment of developing granulomas is involved in a process of autoamplification: acting in an autocrine or paracrine way, it enhances its own synthesis and release, thus favoring further macrophage accumulation and differentiation leading to bacterial elimination.

Plasminogen activator inhibitor-1 in acute hyperoxic mouse lung injury

Hyperoxia-induced lung disease is associated with prominent intraalveolar fibrin deposition. Fibrin turnover is tightly regulated by the concerted action of proteases and antiproteases, and inhibition of plasmin-mediated proteolysis could account for fibrin accumulation in lung alveoli. We show here that lungs of mice exposed to hyperoxia overproduce plasminogen activator inhibitor-1 (PAI-1), and that PAI-1 upregulation impairs fibrinolytic activity in the alveolar compartment. To explore whether increased PAI-1 production is a causal or only a correlative event for impaired intraalveolar fibrinolysis and the development of hyaline membrane disease, we studied mice genetically deficient in PAI-1. We found that these mice fail to develop intraalveolar fibrin deposits in response to hyperoxia and that they are more resistant to the lethal effects of hyperoxic stress. These observations provide clear and novel evidence for the pathogenic contribution of PAI-1 in the development of hyaline membrane disease. They identify PAI-1 as a major deleterious mediator of hyperoxic lung injury.

Thrombocytopenia in an animal model of malaria is associated with an increased caspase-mediated death of thrombocytes

Infection of mice with Plasmodium Berghei Anka (PbA) leads to a thrombocytopenia, due to a reduced platelet life span, eventually associated with a syndrome of severe or cerebral malaria (CM). Thrombocytopenia was associated with an increase in the number of microparticles (mcp) in plasma. More than >60% of these mcp were of platelet origin, as seen by staining with an anti-platelet antibody. The thrombocytopenia and the amount of mcp were decreased in mice treated with anti CD40L mAb, suggesting that CD40L is the main effector of the thrombocytopenia. Caspase-1, -3, -6, -8, -9 were activated in platelets from infected mice, as seen by the binding of labeled probes or the amount of pro-caspase-3. Treatment of infected mice with the caspases inhibitor ZVAD-fmk decreased the number of mcp and the thrombocytopenia, shoving that platelet caspases are responsible for platelet fragmentation. In addition, the caspase inhibitor also caused a decrease in the mortality associated with CM, indicating a critical role of caspases in the expression of CM.

Cytokines Involved in Pulmonary Fibrosis

Publisher Summary This chapter focuses on the role of cytokines in experimental pulmonary fibrosis induced in mice by bleomycin or dust particles and various other types of pulmonary fibrosis such as idiopathic pulmonary fibrosis and sarcoidosis. The role of cytokines can be explored using different methods: (l) tissue extraction is obviously the most direct approach and has been performed successfully for transforming growth factor (TGF)- β during bleomycin-induced pulmonary fibrosis, (2) RNA extraction and evaluation of the mRNA content by Northern blotting have been performed for several cytokines, including interleukin-1, tumor necrosis factor, TGF, and platelet-derived growth factor, and (3) another approach is isolation and exploration of cellular components; alveolar leukocytes and macrophages, freshly prepared or after culture, have been extensively explored in the context of pulmonary fibrosis.

Involvement of Tumour Necrosis Factor and Other Cytokines in Immune-Mediated Vascular Pathology

Vascular endothelial cells are actively involved in coagulation and inflammation processes and appear to represent an important element in cell-mediated immune responses. In this paper, the possible role of endothelial cells as a target for immunopathological reactions was analyzed. Experimental neurovascular lesions were studied in a model of cerebral malaria, with particular attention to the role of cytokine interactions in vivo.

Respective role of polymorphonuclear leukocytes and their integrins (CD-11/18) in the local or systemic toxicity of lipopolysaccharide

The role of neutrophils (PMNs) and leukocyte integrins was investigated in two models of lipopolysac‐ charide (LPS)‐induced toxicity: the systemic lethality assay in D‐galactosamine‐sensitized mice and the local reaction elicited by intradermal injection of LPS and tumor necrosis factor (TNF) at 24‐h intervals. In the local reaction, depletion of PMNs with an anti‐PMN monoclonal antibody (mAb) and mAbs against CD‐11a (or LFA1) and CD‐llb (or CR3) completely prevented the hemorrhagic necrosis. Evaluation of histological sections and myeloperoxidase levels suggested different mechanism of protection because PMNs were abundant in anti‐ CD‐11‐ and absent in anti‐PMN‐treated mice. In the systemic assay, depletion of PMNs ensured 100% survival, whereas after administration of anti‐CD‐1 la or b mAb, the percentages of survivors were 6 and 59%, respectively. One hour after LPS injection, the serum TNF‐α level was higher in PMN‐depleted mice than in controls. These studies provide evidence that neutrophils are essential for the expression of local or systemic LPS‐induced injury, whereas the requirement for their leukocytic integrins is obvious only in the local reaction.

Change in the Humoral Response of Athymic Nude Mice with Ageing

The evolution of the serum Ig levels of Balb/c‐nu/nu mice was investigated between 1 month and 12 months of age. An increase as a function of age was observed in all classes and subclasses, which was, expressed in percentage of a nu/+ serum, from 130% to 230% for IgM, from 3% to 24% for IgG1, from 12% to 164% for IgG2a, from 28% to 62% for IgG2b, and from 10% to 50% for IgA. This increase correlates with an increase of plasma cells of each class in the bone marrow, whereas the number of plasma cells in the spleen, the lymph node, and the intestinal mucosa did not change markedly with age. The humoral response after an injection of heterologous erythrocytes was compared in young and aged nu/nu mice; aged mice had a higher haemagglutination titre mainly due to direct (IgM) antibodies. The response of the spleen, as judged by plaque‐forming cells (PFC), was similar in young and aged mice, but the bone marrow response, not detectable in young mice, was about as high in aged nude mice as in nu/+ mice. Although the content of Thy 1 cells in the spleen and lymph nodes was markedly higher in aged than in young nude mice, no T‐cell function could be detected at any age, either in the response to phytohaemagglutinin or concanavalin A or in a graft‐versus‐host assay. Increase in the Ig production with age is interpreted as the result of progressive priming and hyperimmunization by environmental antigens, leading to a T‐independent immune response (even against antigens considered to be T‐dependent) predominantly located in the bone marrow.

Tumor necrosis factor/cachectin as an effector of T cell-dependent immunopathology.

Publisher Summary The possible implications of tumor necrosis factor (TNF) in immunopathological reactions has been investigated only recently. It is likely that TNF is involved at several levels of the immune response. Thus, this chapter describes TNF properties relevant to tissue injury, the role of TNF in T cell-mediated immunopathological reactions in vivo, and the possible cytokine interactions responsible for the overproduction of TNF. One of the characteristics of TNF responsible for its effects observed originally, that is, the induction of hemorrhagic necrosis of tumors, is its numerous and potent effects on vascular endothelial cells. The major effects of TNF in endotoxinemia—such as cerebrovascular lesions in malaria or vascular leak in graft-versus-host disease—may indeed depend largely on the modulatory and toxic effects of TNF on endothelial cells. Another peculiar feature of TNF is its ability to induce concomitantly cellular necrosis and proliferation, which are characteristic alterations of tissue damage and remodeling observed in immunopathological reactions. In vitro, it has been shown that TNF—depending on the dose—can cause either proliferation or necrosis of various cell types. In vivo, administration of recombinant TNF to several species—including man—reproduces the pathological changes of Gram-negative sepsis.

CD40-CD40 Ligand Disruption Does Not Prevent Hyperoxia-Induced Injury

Recent studies suggest that apoptosis plays a role in oxygen-induced injury, although the activation pathways and the executioner proteases that lead to cleavage of lung cell proteins and DNA, are not yet identified. We explored previously the tumor necrosis factor/tumor necrosis factor receptor and the Fas/FasL, belonging to the intrinsic pathway, and could not demonstrate any protective effect by interfering with these cell receptors. Lately, it has been shown that interacting with the CD40 system, also known to promote cell death, by administering anti-CD40 ligand (L) antibody was beneficial in several diseases and, in particular, in hyperoxia-induced injury. Using CD40- and CD40L-deficient mice (-/-) as well as administering anti-CD40L antibody, we examined the extent of lung injury in oxygen-breathing mice by several ways (lung weight, histology, inflammatory mediators, and DNA ladder) as well as the mortality. The development of lung injury was similar in wild-type, CD40-/-, CD40L-/-, or in wild-type mice treated with anti-CD40L antibody. Apoptosis was present in all conditions at 72 hours of oxygen exposure. These results show that oxygen-induced injury does not require CD40-CD40L interaction and that apoptosis of lung cells does not involve this pathway.

Short-lived lymphoid cells respond more rapidly to stimulation by phytohemagglutinin or concanavalin a. An explanation for the apparent inhibitory effect of vinblastine on the activation of lymphoid cells.

Abstract Mouse spleen or lymph node cells, whose ‘short-lived’ population had been labelled in vivo by repeated injections of [3H]thymidine, were cultured in the presence or absence of phytohemagglutinin (PHA) or concanavalin A (ConA). The cells proliferating in culture were arrested in mitosis with vinblastine and studied by autoradiography. After 24 h the number of mitoses was about six times higher in the stimulated than in the unstimulated cultures, and the majority of the mitoses were labelled. After 48 h, the number of mitoses was increased about 40-fold in the stimulated cultures, and less than 10% of these mitoses were labelled. In stimulated cultures performed in the continuous presence of vinblastine, in which the first mitoses of the responding cells can be observed for a few hours before the cell arrested in metaphase disintegrates, large numbers of mitoses were observed on the second and third day of culture, none of which were labelled. These results indicate the following. 1. 1. Short-lived cells respond more rapidly to mitogen than do long-lived cells. 2. 2. When vinblastine is continuously present, the progeny of the cells which were in S phase at the beginning of the culture are arrested in metaphase during the first 24 h, which explains why vinblastine markedly decreases the earliest stimulation of DNA synthesis. 3. 3. The mitotic response of the long-lived cells, which occurs during the second and third day of culture and represents the majority of the responding cells, is unaffected by the continuous presence of vinblastine, indicating that integrity of the microtubular system is not necessary for the mitogenic stimulation of these lymphocytes.