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M Pasparakis

Publications and source records attributed to M Pasparakis.

At least 19 recordsLinked to original sources
PubMed2006

Dissection of the NF-kappaB signalling cascade in transgenic and knockout mice.

Studies in transgenic and knockout mice have made a major contribution to our current understanding of the physiological functions of the NF-kappaB signalling cascade. The generation and analysis of mice with targeted modifications of individual components of the NF-kappaB pathway tremendously advanced our knowledge of the roles of the NF-kappaB proteins themselves, and also of the many activators and negative regulators of NF-kappaB. These studies have highlighted the complexity of the NF-kappaB system, by revealing the multiple interactions, redundancies, but also diverse functions, performed by the different molecules participating in the regulation of NF-kappaB signalling. Furthermore, inhibition or enforced activation of NF-kappaB in transgenic mice has uncovered the critical roles that NF-kappaB plays in the pathogenesis of various diseases such as liver failure, diabetes and cancer.

Animals↗
PubMed2006

Elevated serum levels of calcium-binding S100 proteins A8 and A9 reflect disease activity and abnormal differentiation of keratinocytes in psoriasis.

BACKGROUND: The expression of calcium-binding S100 molecules organized within the epidermal differentiation complex on chromosome 1q21 is disturbed in hyperproliferative skin diseases such as psoriasis. OBJECTIVES: We studied whether serum levels of S100 proteins A8 (S100A8) and A9 (S100A9) are elevated in psoriasis, correlated their amounts with disease activity and identified potential cellular sources. METHODS: Serum obtained from psoriasis patients or from healthy individuals was studied for S100A8 and S100A9 levels by enzyme-linked immunosorbent assay. Data were correlated to disease activity as reflected by the Psoriasis Area and Severity Index (PASI). Cellular sources of S100A8 and S100A9 were identified by in situ hybridization and immunohistochemistry of lesional psoriatic and nonlesional, nonpsoriatic skin. RESULTS: A significant increase of S100A8/S100A9 serum levels was found in patients with psoriasis compared with healthy controls. Grading the patients into two groups of severity, individuals with a PASI of <15 showed serum levels of 705+/-120 ng mL-1 (mean+/-SEM, n=18), those with a PASI of >or=15 showed levels of 1315+/-150 ng mL-1 (n=32) while controls presented with 365+/-50 ng mL-1. Performing in situ hybridization of lesional psoriatic skin we detected a dramatic induction of both S100A8 and S100A9 mRNA and protein primarily in the suprabasal layers of the epidermis while expression was negligible in nonlesional, nonpsoriatic interfollicular epidermis. CONCLUSIONS: Our data demonstrate that hyperproliferation and abnormal differentiation of psoriatic skin is associated with a massive upregulation and secretion of S100A8 and S100A9, suggesting not only a prominent role of these molecules during intracellular calcium-dependent signalling but also implying distinct extracellular functions.

Acute Disease↗
PubMed2000

Tumor necrosis factor and the p55TNF receptor are required for optimal development of the marginal sinus and for migration of follicular dendritic cell precursors into splenic follicles.

The development and function of secondary lymphoid tissue require signaling by tumor necrosis factor and lymphotoxins. Mice deficient in LTbetaR show defective organogenesis of lymph nodes and Peyer's patches and a severely disturbed splenic architecture. In contrast, TNF or p55TNF-R deficiency does not affect the organogenesis of peripheral lymphoid organs but interferes with the formation of B cell follicles and the appearance of FDC networks and germinal centers in all secondary lymphoid organs. Based on these differences, we have previously hypothesized that the role of TNF in lymphoid structure is distinct from that of LT and restricted in regulating cellular interactions that allow the differentiation and/or correct positioning of FDCs. In the present study we show that, in addition to the defects in follicular structure, TNF or p55TNF-R knockout mice exhibit defects in the formation of the macrophage populations and of the sinus lining cells of the splenic marginal zone. Interestingly, a large number of dendritic-shaped cells stained with FDC-specific markers and able to trap immune complexes are retained within the defective marginal zone of TNF and p55TNF-R knockout spleens. We conclude that the primary defect in the lymphoid phenotype of TNF or p55TNF-R knockout mice is the failure of FDC precursors to migrate through the disorganized marginal sinus and to home properly into the splenic follicular areas where they would promote the formation of B cell follicles and germinal centers.

Animals↗
PubMed2000

NEMO/IKK gamma-deficient mice model incontinentia pigmenti.

Disruption of the X-linked gene encoding NF-kappa B essential modulator (NEMO) produces male embryonic lethality, completely blocks NF-kappa B activation by proinflammatory cytokines, and interferes with the generation and/or persistence of lymphocytes. Heterozygous female mice develop patchy skin lesions with massive granulocyte infiltration and hyperproliferation and increased apoptosis of keratinocytes. Diseased animals present severe growth retardation and early mortality. Surviving mice recover almost completely, presumably through clearing the skin of NEMO-deficient keratinocytes. Male lethality and strikingly similar skin lesions in heterozygous females are hallmarks of the human genetic disorder incontinentia pigmenti (IP). Together with the recent discovery that mutations in the human NEMO gene cause IP, our results indicate that we have created a mouse model for that disease.

Animals↗
PubMed2000

Tumor necrosis factor alpha-deficient, but not interleukin-6-deficient, mice resist peripheral infection with scrapie.

In most peripheral infections of rodents and sheep with scrapie, infectivity is found first in lymphoid tissues and later in the central nervous system (CNS). Cells within the germinal centers (GCs) of the spleen and lymph nodes are important sites of extraneural replication, from which infection is likely to spread to the CNS along peripheral nerves. Here, using immunodeficient mice, we investigate the identity of the cells in the spleen that are important for disease propagation. Despite possessing functional T and B lymphocytes, tumor necrosis factor alpha-deficient (TNF-alpha(-/-)) mice lack GCs and follicular dendritic cell (FDC) networks in lymphoid tissues. In contrast, lymphoid tissues of interleukin-6-deficient (IL-6(-/-)) mice possess FDC networks but have impaired GCs. When the CNSs of TNF-alpha(-/-), IL-6(-/-), and wild-type mice were directly challenged with the ME7 scrapie strain, 100% of the mice were susceptible, developing disease after closely similar incubation periods. However, when challenged peripherally (intraperitoneally), most TNF-alpha(-/-) mice failed to develop scrapie up to 503 days postinjection. All wild-type and IL-6(-/-) mice succumbed to disease approximately 300 days after the peripheral challenge. High levels of scrapie infection and the disease-specific isomer of the prion protein, PrP(Sc), were detectable in spleens from challenged wild-type and IL-6(-/-) mice but not from TNF-alpha(-/-) mice. Histopathological analysis of spleen tissue demonstrated heavy PrP accumulations in direct association with FDCs in challenged wild-type and IL-6(-/-) mice. No PrP(Sc) accumulation was detected in spleens from TNF-alpha(-/-) mice. We conclude that, for the ME7 scrapie strain, mature FDCs are critical for replication in lymphoid tissues and that in their absence, neuroinvasion following peripheral challenge is impaired.

Animals↗
PubMed1999

Myocyte-dependent regulation of endothelial cell syndecan-4 expression. Role of TNF-alpha.

Syndecan-4 is a unique member of the syndecan gene family that has the ability to bind and activate protein kinase C-alpha. Whereas increased syndecan-4 levels have been noted in ischemic hearts, little is known regarding the regulation of its expression. To investigate the role of cardiac myocytes in induction of syndecan-4 expression, human endothelial cells (ECV304) were exposed to a medium conditioned by primary mouse cardiac myocytes or H9c2 cells. The medium conditioned by hypoxic but not normal myocytes was able to induce syndecan-4 expression in ECV cells. Western analysis of the conditioned medium demonstrated an increased presence of tumor necrosis factor-alpha (TNF-alpha) in the medium conditioned by hypoxic but not normal myoblasts. Primary cardiac myocytes collected from the wild type C57/129 but not the homozygous TNF-alpha-/- knockout mice were able to induce syndecan-4 expression in ECV cells when cultured under hypoxic conditions. In vitro studies demonstrated that TNF-alpha induced endothelial cell syndecan-4 expression by both increasing syndecan-4 gene expression in an NF-kappaB-dependent manner and by prolonging syndecan-4 mRNA half-life. We conclude that TNF-alpha is the principal factor produced by the ischemic myocytes that is responsible for induction of endothelial cell syndecan-4 expression and that this requires both transcriptional and posttranscriptional mechanisms.

Animals↗
PubMed1999

TNF accelerates the onset but does not alter the incidence and severity of myelin basic protein-induced experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) induction in TNF gene-targeted mice has resulted in conflicting reports in part due to the strong association of TNF with the MHC locus. To define the participation of TNF in EAE development, we back-crossed TNF-deficient mice (H-2b) into the SJL/J strain and directly compared them to H-2b congenic SJL or inbred SJL/J mice. Induction of EAE with myelin basic protein (MBP) revealed that H-2b congenic SJL mice are fully susceptible, indicating that the H-2b haplotype does not affect disease susceptibility. Using H-2b congenic SJL mice we show here that TNF deficiency modifies the normal course of EAE by considerably delaying the onset for approximately 5 days, suggesting that TNF is required for the normal initiation of MBP-induced EAE. However, TNF-deficient mice eventually developed severe EAE with perivascular inflammation and primary demyelination similar to wild-type controls, indicating that TNF is not essential during these processes. Taken together, these results indicate that although TNF is not required for the progression of MBP-induced EAE, it contributes positively by advancing the onset of disease.

Animals↗
PubMed1999

Impaired on/off regulation of TNF biosynthesis in mice lacking TNF AU-rich elements: implications for joint and gut-associated immunopathologies.

We addressed the impact of deleting TNF AU-rich elements (ARE) from the mouse genome on the regulation of TNF biosynthesis and the physiology of the host. Absence of the ARE affected mechanisms responsible for TNF mRNA destabilization and translational repression in hemopoietic and stromal cells. In stimulated conditions, TNF ARE were required both for the alleviation and reinforcement of message destabilization and translational silencing. Moreover, the mutant mRNA was no longer responsive to translational modulation by the p38 and JNK kinases, demonstrating that TNF ARE are targets for these signals. Development of two specific pathologies in mutant mice, i.e., chronic inflammatory arthritis and Crohn's-like inflammatory bowel disease, suggests that defective function of ARE may be etiopathogenic for the development of analogous human pathologies.

3' Untranslated Regions↗
PubMed1999

Mice deficient in tumor necrosis factor-alpha are resistant to skin carcinogenesis.

Given the associations between chronic inflammation and epithelial cancer, we studied susceptibility to skin carcinogenesis in mice deficient for the pro-inflammatory cytokine TNF-alpha (refs. 5,6). TNF-alpha(-/-) mice were resistant to development of benign and malignant skin tumors, whether induced by initiation with DMBA and promotion with TPA or by repeated dosing with DMBA. TNF-alpha(-/-) mice developed 5-10% the number of tumors developed by wild-type mice during initiation/promotion and 25% of those in wild-type mice after repeated carcinogen treatment. TNF-alpha could influence tumor and stromal cells during tumor development. The early stages of TPA promotion are characterized by keratinocyte hyperproliferation and inflammation. These were diminished in TNF-alpha(-/-) mice. TNF-alpha was extensively induced in the epidermis, but not the dermis, in TPA-treated wild-type skin, indicating that dermal inflammation is controlled by keratinocyte TNF-alpha production. Deletion of a TNF-alpha inducible chemokine also conferred some resistance to skin tumor development. TNF-alpha has little influence on later stages of carcinogenesis, as tumors in wild-type and TNF-alpha(-/-) mice had similar rates of malignant progression. These data provide evidence that a pro-inflammatory cytokine is required for de novo carcinogenesis and that TNF-alpha is important to the early stages of tumor promotion. Strategies that neutralize TNF-alpha production may be useful in cancer treatment and prevention.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Methotrexate specifically modulates cytokine production by T cells and macrophages in murine collagen-induced arthritis (CIA): a mechanism for methotrexate-mediated immunosuppression.

Immunosuppressive therapy with methotrexate (MTX) has been established as effective treatment for patients with rheumatoid arthritis. To analyse the therapeutic potential and mechanisms of action of MTX, we determined serum cytokine levels and cytokine production by splenic T cells and macrophages in untreated and MTX-treated mice. Furthermore, we assessed the role of MTX in a murine model of experimental arthritis induced by collagen type II (CIA). MTX reduced spontaneous and IL-15-induced tumour necrosis factor (TNF) production by splenic T cells but not by macrophages from healthy mice in vitro in a dose-dependent manner. In contrast, interferon-gamma (IFN-gamma) production was less strikingly reduced and IL-4 production was virtually unaffected. In addition, treatment of healthy mice with MTX in vivo led to reduced TNF serum levels and diminished TNF production by splenic T cells and macrophages. Intraperitoneal administration of MTX prior to the onset of arthritis completely prevented clinical and pathological signs of CIA. This was associated with a striking reduction of TNF production by spleen cells from MTX-treated mice. The role of TNF in MTX-mediated effects on cytokine production was further underlined by the finding that MTX effects on IFN-gamma production were augmented in TNF-transgenic mice but abrogated in mice in which the TNF-alpha gene had been inactivated by homologous recombination. Thus, MTX specifically modulates spontaneous and IL-15-induced TNF-alpha production in mice and prevents experimental murine CIA. These data suggest that TNF production by T cells is an important target of MTX and may serve as a basis to understand and further analyse MTX-mediated mechanisms of immunosuppression in patients with RA.

Animals↗
PubMed1998

Complementation of lymphotoxin alpha knockout mice with tumor necrosis factor-expressing transgenes rectifies defective splenic structure and function.

Lymphotoxin (LT)alpha knockout mice, as well as double LTalpha/tumor necrosis factor (TNF) knockout mice, show a severe splenic disorganization with nonsegregating T/B cell zones and complete absence of primary B cell follicles, follicular dendritic cell (FDC) networks, and germinal centers. In contrast, as shown previously and confirmed in this study, LTbeta-deficient mice show much more conserved T/B cell areas and a reduced but preserved capacity to form germinal centers and FDC networks. We show here that similar to the splenic phenotype of LTbeta-deficient mice, complementation of LTalpha knockout mice with TNF-expressing transgenes leads to a p55 TNF receptor-dependent restoration of B/T cell zone segregation and a partial preservation of primary B cell follicles, FDC networks, and germinal centers. Notably, upon lipopolysaccharide challenge, LTalpha knockout mice fail to produce physiological levels of TNF both in peritoneal macrophage supernatants and in their serum, indicating a coinciding deficiency in TNF expression. These findings suggest that defective TNF expression contributes to the complex phenotype of the LTalpha knockout mice, and uncover a predominant role for TNF and its p55 TNF receptor in supporting, even in the absence of LTalpha, the development and maintenance of splenic B cell follicles, FDC networks, and germinal centers.

Animals↗
PubMed1998

Oligodendrocyte apoptosis and primary demyelination induced by local TNF/p55TNF receptor signaling in the central nervous system of transgenic mice: models for multiple sclerosis with primary oligodendrogliopathy.

The scientific dogma that multiple sclerosis (MS) is a disease caused by a single pathogenic mechanism has been challenged recently by the heterogeneity observed in MS lesions and the realization that not all patterns of demyelination can be modeled by autoimmune-triggered mechanisms. To evaluate the contribution of local tumor necrosis factor (TNF) ligand/receptor signaling pathways to MS immunopathogenesis we have analyzed disease pathology in central nervous system-expressing TNF transgenic mice, with or without p55 or p75TNF receptors, using combined in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling and cell identification techniques. We demonstrate that local production of TNF by central nervous system glia potently and selectively induces oligodendrocyte apoptosis and myelin vacuolation in the context of an intact blood-brain barrier and absence of immune cell infiltration into the central nervous system parenchyma. Interestingly, primary demyelination then develops in a classical manner in the presence of large numbers of recruited phagocytic macrophages, possibly the result of concomitant pro-inflammatory effects of TNF in the central nervous system, and lesions progress into acute or chronic MS-type plaques with axonal damage, focal blood-brain barrier disruption, and considerable oligodendrocyte loss. Both the cytotoxic and inflammatory effects of TNF were abrogated in mice genetically deficient for the p55TNF receptor demonstrating a dominant role for p55TNF receptor-signaling pathways in TNF-mediated pathology. These results demonstrate that aberrant local TNF/p55TNF receptor signaling in the central nervous system can have a potentially major role in the aetiopathogenesis of MS demyelination, particularly in MS subtypes in which oligodendrocyte death is a primary pathological feature, and provide new models for studying the basic mechanisms underlying oligodendrocyte and myelin loss.

Animals↗
PubMed1997

Peyer's patch organogenesis is intact yet formation of B lymphocyte follicles is defective in peripheral lymphoid organs of mice deficient for tumor necrosis factor and its 55-kDa receptor.

Targeted inactivation of genes in the tumor necrosis factor (TNF)/lymphotoxin (LT) ligand and receptor system has recently revealed essential roles for these molecules in lymphoid tissue development and organization. Lymphotoxin-alphabeta (LTalphabeta)/lymphotoxin-beta receptor (LTbeta-R) signaling is critical for the organogenesis of lymph nodes and Peyer's patches and for the structural compartmentalization of the splenic white pulp into distinct B and T cell areas and marginal zones. Moreover, an essential role has been demonstrated for TNF/p55 tumor necrosis factor receptor (p55TNF-R) signaling in the formation of splenic B lymphocyte follicles, follicular dendritic cell networks, and germinal centers. In contrast to a previously described essential role for the p55TNF-R in Peyer's patch organogenesis, we show in this report that Peyer's patches are present in both TNF and p55TNF-R knockout mice, demonstrating that these molecules are not essential for the organogenesis of this lymphoid organ. Furthermore, we show that in the absence of TNF/p55TNF-R signaling, lymphocytes segregate normally into T and B cell areas and a normal content and localization of dendritic cells is observed in both lymph nodes and Peyer's patches. However, although B cells are found to home normally within Peyer's patches and in the outer cortex area of lymph nodes, organized follicular structures and follicular dendritic cell networks fail to form. These results show that in contrast to LTalphabeta signaling, TNF signaling through the p55TNF-R is not essential for lymphoid organogenesis but rather for interactions that determine the cellular and structural organization of B cell follicles in all secondary lymphoid tissues.

Animals↗
PubMed1997

Predominant pathogenic role of tumor necrosis factor in experimental colitis in mice.

Antibodies to tumor necrosis factor (TNF)-alpha have been recently proposed as effective treatment for patients with Crohn's disease. Here, we analyze the functional role of TNF-alpha in a mouse model of chronic intestinal inflammation induced by the hapten reagent 2,4,6,-trinitrobenzene sulfonic acid (TNBS) that mimics some characteristics of Crohn's disease in humans. Macrophage-enriched lamina propria (LP) mononuclear cells from mice with TNBS-induced colitis produced 10-30-fold higher levels of TNF-alpha mRNA and protein than cells from control mice. When mice with chronic colitis were treated by intraperitoneal injection of antibodies to TNF-alpha, an improvement of both the clinical and histopathologic signs of disease was found. Isolated macrophage-enriched LP cells from anti-TNF-alpha-treated mice produced strikingly less pro-inflammatory cytokines such as interleukin (IL)-1 and IL-6 in cell culture. The predominant role of TNF-alpha in the mouse TNBS-induced colitis model was further underlined by the finding that striking colonic inflammation and lethal pancolitis was induced in TNF-alpha-transgenic mice upon TNBS treatment. Conversely, no significant TNBS-induced colitis could be induced in mice in which the TNF-alpha gene had been inactivated by homologous recombination. Complementation of TNF-alpha function in TNF-/- mice by the expression of a mouse TNF-alpha transgene was sufficient to reverse this effect. Taken together, the data provide direct evidence for a predominant role of TNF-alpha in a mouse model of chronic intestinal inflammation and encourage further clinical trials with antibodies to TNF-alpha for the treatment of patients with Crohn's disease.

Animals↗
PubMed1997

A murine transmembrane tumor necrosis factor (TNF) transgene induces arthritis by cooperative p55/p75 TNF receptor signaling.

The arthritogenic activities of tumor necrosis factor (TNF) and its p55TNF-receptor (R) have been well documented in experimental animal models of arthritis, and in transgenic mice expressing wild-type or mutant transmembrane human TNF proteins in their joints. In this study we show that chronic inflammatory arthritis also develops in transgenic mice made to overexpress a mutant transmembrane from of the murine TNF protein (muTNF delta 1-12) which is known to utilize efficiently both the p55 and the p75TNFR. Cross-breeding of the transgene into a TNF knockout background did not alter development of disease. Analysis of TNF bioactivity in sera from lipopolysaccharide-stimulated mice or ex vivo macrophage cultures demonstrated that the muTNF delta 1-12 protein accumulates on the cell surface and is not processed to bioactive soluble TNF, indicating that transmembrane TNF is by itself sufficient to mediate pathogenesis of arthritis. Furthermore, using TNFR knockout mice, it is shown that development of transmembrane TNF-mediated arthritis requires the presence of the p55TNFR but is significantly delayed in the absence of the p75TNFR, suggesting a positive cooperation between the two TNFR in the arthritogenic process. These results indicate that blocking the activities of both soluble and transmembrane TNF may be required to effectively neutralize the pathogenic potential of this cytokine in arthritis.

Animals↗
PubMed1997

In vivo evidence for a functional role of both tumor necrosis factor (TNF) receptors and transmembrane TNF in experimental hepatitis.

The significance of tumor necrosis factor receptor 1 (TNFR1) for TNF function in vivo is well documented, whereas the role of TNFR2 so far remains obscure. In a model of concanavalin A (Con A)-induced, CD4+ T cell-dependent experimental hepatitis in mice, in which TNF is a central mediator of apoptotic and necrotic liver damage, we now provide evidence for an essential in vivo function of TNFR2 in this pathophysiological process. We demonstrate that a cooperation of TNFR1 and TNFR2 is required for hepatotoxicity as mice deficient of either receptor were resistant against Con A. A significant role of TNFR2 for Con A-induced hepatitis is also shown by the enhanced sensitivity of transgenic mice overexpressing the human TNFR2. The ligand for cytotoxic signaling via both TNF receptors is the precursor of soluble TNF, i.e. transmembrane TNF. Indeed, transmembrane TNF is sufficient to mediate hepatic damage, as transgenic mice deficient in wild-type soluble TNF but expressing a mutated nonsecretable form of TNF developed inflammatory liver disease.

Animals↗
PubMed1997

TNF-alpha transgenic and knockout models of CNS inflammation and degeneration.

Tumour necrosis factor-alpha (TNF-alpha) plays a central role in inflammatory events including those taking place in the central nervous system (CNS), and has been implicated as a key pathogenic mediator in several human inflammatory, infectious and autoimmune CNS disorders. Using transgenic and gene knockout mice we have investigated the role of deregulated TNF-alpha production in the CNS. We show that the overexpression of wild-type murine or human TNF-alpha transgenes by resident CNS astrocytes or neurons in sufficient to trigger a neurological disorder characterised by ataxia, seizures and paresis, with histopathological features of chronic CNS inflammation and white matter degeneration. Furthermore, we show that transmembrane human TNF-alpha is sufficient to trigger CNS inflammation and degeneration when overexpressed by astrocytes but not by neurons, indicating that target cells mediating the neuroinflammatory activities of TNF-alpha localise in the vicinity of astrocytes rather than neurons. Our results establish that both soluble and transmembrane molecular forms of TNF-alpha can play critical roles in vivo in the pathogenesis of CNS inflammation and demyelination, and validate TNF-alpha transgenic and mutant mice as important models for the further study of related human CNS diseases.

Animals↗