Showing papers in "Nature Medicine in 2000"
TL;DR: The cellular and molecular mechanisms underlying the formation of endothelium-lined channels and their maturation via recruitment of smooth muscle cells (arteriogenesis) during physiological and pathological conditions are summarized, alongside with possible therapeutic applications.
Abstract: Endothelial and smooth muscle cells interact with each other to form new blood vessels. In this review, the cellular and molecular mechanisms underlying the formation of endothelium-lined channels (angiogenesis) and their maturation via recruitment of smooth muscle cells (arteriogenesis) during physiological and pathological conditions are summarized, alongside with possible therapeutic applications.
4,154 citations
TL;DR: In many instances, permeabilization of mitochondrial membranes is a rate-limiting step of apoptotic or necrotic cell demise, which has important consequences for the pathophysiology of cell death, as well as for its pharmacological control.
Abstract: In many instances, permeabilization of mitochondrial membranes is a rate-limiting step of apoptotic or necrotic cell demise. This has important consequences for the pathophysiology of cell death, as well as for its pharmacological control.
3,076 citations
TL;DR: It is demonstrated that Fc-receptor-dependent mechanisms contribute substantially to the action of cytotoxic antibodies against tumors and indicate that an optimal antibody against tumors would bind preferentially to activation Fc receptors and minimally to the inhibitory partner FcγRIIB.
Abstract: Inhibitory receptors have been proposed to modulate the in vivo cytotoxic response against tumor targets for both spontaneous and antibody-dependent pathways. Using a variety of syngenic and xenograft models, we demonstrate here that the inhibitory FcgammaRIIB molecule is a potent regulator of antibody-dependent cell-mediated cytotoxicity in vivo, modulating the activity of FcgammaRIII on effector cells. Although many mechanisms have been proposed to account for the anti-tumor activities of therapeutic antibodies, including extended half-life, blockade of signaling pathways, activation of apoptosis and effector-cell-mediated cytotoxicity, we show here that engagement of Fcgamma receptors on effector cells is a dominant component of the in vivo activity of antibodies against tumors. Mouse monoclonal antibodies, as well as the humanized, clinically effective therapeutic agents trastuzumab (Herceptin(R)) and rituximab (Rituxan(R)), engaged both activation (FcgammaRIII) and inhibitory (FcgammaRIIB) antibody receptors on myeloid cells, thus modulating their cytotoxic potential. Mice deficient in FcgammaRIIB showed much more antibody-dependent cell-mediated cytotoxicity; in contrast, mice deficient in activating Fc receptors as well as antibodies engineered to disrupt Fc binding to those receptors were unable to arrest tumor growth in vivo. These results demonstrate that Fc-receptor-dependent mechanisms contribute substantially to the action of cytotoxic antibodies against tumors and indicate that an optimal antibody against tumors would bind preferentially to activation Fc receptors and minimally to the inhibitory partner FcgammaRIIB.
2,831 citations
TL;DR: It is reported that intravenous injection of adult bone marrow cells in the FAH−/− mouse, an animal model of tyrosinemia type I, rescued the mouse and restored the biochemical function of its liver.
Abstract: The characterization of hepatic progenitor cells is of great scientific and clinical interest. Here we report that intravenous injection of adult bone marrow cells in the FAH(-/-) mouse, an animal model of tyrosinemia type I, rescued the mouse and restored the biochemical function of its liver. Moreover, within bone marrow, only rigorously purified hematopoietic stem cells gave rise to donor-derived hematopoietic and hepatic regeneration. This result seems to contradict the conventional assumptions of the germ layer origins of tissues such as the liver, and raises the question of whether the cells of the hematopoietic stem cell phenotype are pluripotent hematopoietic cells that retain the ability to transdifferentiate, or whether they are more primitive multipotent cells.
2,417 citations
TL;DR: Results indicate that antibodies can cross the blood–brain barrier to act directly in the central nervous system and should be considered as a therapeutic approach for the treatment of Alzheimer disease and other neurological disorders.
Abstract: One hallmark of Alzheimer disease is the accumulation of amyloid beta-peptide in the brain and its deposition as plaques. Mice transgenic for an amyloid beta precursor protein (APP) mini-gene driven by a platelet-derived (PD) growth factor promoter (PDAPP mice), which overexpress one of the disease-linked mutant forms of the human amyloid precursor protein, show many of the pathological features of Alzheimer disease, including extensive deposition of extracellular amyloid plaques, astrocytosis and neuritic dystrophy. Active immunization of PDAPP mice with human amyloid beta-peptide reduces plaque burden and its associated pathologies. Several hypotheses have been proposed regarding the mechanism of this response. Here we report that peripheral administration of antibodies against amyloid beta-peptide, was sufficient to reduce amyloid burden. Despite their relatively modest serum levels, the passively administered antibodies were able to enter the central nervous system, decorate plaques and induce clearance of preexisting amyloid. When examined in an ex vivo assay with sections of PDAPP or Alzheimer disease brain tissue, antibodies against amyloid beta-peptide triggered microglial cells to clear plaques through Fc receptor-mediated phagocytosis and subsequent peptide degradation. These results indicate that antibodies can cross the blood-brain barrier to act directly in the central nervous system and should be considered as a therapeutic approach for the treatment of Alzheimer disease and other neurological disorders.
2,181 citations
TL;DR: The ubiquitin system plays important roles in the control of numerous processes, including cell-cycle progression, signal transduction, transcriptional regulation, receptor down-regulation, and endocytosis as mentioned in this paper.
Abstract: The selective degradation of many short-lived proteins in eukaryotic cells is carried out by the ubiquitin system. In this pathway, proteins are targeted for degradation by covalent ligation to ubiquitin, a highly conserved small protein. Ubiquitin-mediated degradation of regulatory proteins plays important roles in the control of numerous processes, including cell-cycle progression, signal transduction, transcriptional regulation, receptor down-regulation, and endocytosis. The ubiquitin system has been implicated in the immune response, development, and programmed cell death. Abnormalities in ubiquitin-mediated processes have been shown to cause pathological conditions, including malignant transformation. In this review we discuss recent information on functions and mechanisms of the ubiquitin system. Since the selectivity of protein degradation is determined mainly at the stage of ligation to ubiquitin, special attention is focused on what we know, and would like to know, about the mode of action of ubiquitin-protein ligation systems and about signals in proteins recognized by these systems.
2,177 citations
TL;DR: It is demonstrated here that carbon monoxide, a by-product of heme catabolism by heme oxygenase, mediates potent anti-inflammatory effects and may have an important protective function in inflammatory disease states and thus has potential therapeutic uses.
Abstract: The stress-inducible protein heme oxygenase-1 provides protection against oxidative stress. The anti-inflammatory properties of heme oxygenase-1 may serve as a basis for this cytoprotection. We demonstrate here that carbon monoxide, a by-product of heme catabolism by heme oxygenase, mediates potent anti-inflammatory effects. Both in vivo and in vitro, carbon monoxide at low concentrations differentially and selectively inhibited the expression of lipopolysaccharide-induced pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β, and macrophage inflammatory protein-1β and increased the lipopolysaccharide-induced expression of the anti-inflammatory cytokine interleukin-10. Carbon monoxide mediated these anti-inflammatory effects not through a guanylyl cyclase–cGMP or nitric oxide pathway, but instead through a pathway involving the mitogen-activated protein kinases. These data indicate the possibility that carbon monoxide may have an important protective function in inflammatory disease states and thus has potential therapeutic uses.
2,035 citations
TL;DR: In situ hybridization of the perifornical area and peptide radioimmunoassays indicated global loss of hypocretins, without gliosis or signs of inflammation in all human cases examined, indicating most cases of human narcolepsy are associated with a deficient hypocretin system.
Abstract: We explored the role of hypocretins in human narcolepsy through histopathology of six narcolepsy brains and mutation screening of Hcrt, Hcrtr1 and Hcrtr2 in 74 patients of various human leukocyte antigen and family history status. One Hcrt mutation, impairing peptide trafficking and processing, was found in a single case with early onset narcolepsy. In situ hybridization of the perifornical area and peptide radioimmunoassays indicated global loss of hypocretins, without gliosis or signs of inflammation in all human cases examined. Although hypocretin loci do not contribute significantly to genetic predisposition, most cases of human narcolepsy are associated with a deficient hypocretin system.
1,939 citations
TL;DR: Findings indicate that CD14 is a co-receptor for HSP70-mediated signaling in human monocytes and are indicative of an previously unrecognized function for H SP70 as an extracellular protein with regulatory effects on human monocyte, having a dual role as chaperone and cytokine.
Abstract: Here, we demonstrate a previously unknown function for the 70-kDa heat-shock protein (HSP70) as a cytokine. HSP70 bound with high affinity to the plasma membrane, elicited a rapid intracellular calcium flux, activated nuclear factor (NF)-kappaB and upregulated the expression of pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6 in human monocytes. Furthermore, two different signal transduction pathways were activated by exogenous HSP70: one dependent on CD14 and intracellular calcium, which resulted in increased IL-1beta, IL-6 and TNF-alpha; and the other independent of CD14 but dependent on intracellular calcium, which resulted in an increase in TNF-alpha but not IL-1beta or IL-6. These findings indicate that CD14 is a co-receptor for HSP70-mediated signaling in human monocytes and are indicative of an previously unrecognized function for HSP70 as an extracellular protein with regulatory effects on human monocytes, having a dual role as chaperone and cytokine.
1,583 citations
TL;DR: It is shown that mice deficient in aquaporin-4 (AQP4), a glial membrane water channel, have much better survival than wild-type mice in a model of brain edema caused by acute water intoxication, and suggested that AQP4 inhibition may provide a new therapeutic option for reducingbrain edema in a wide variety of cerebral disorders.
Abstract: Cerebral edema contributes significantly to morbidity and death associated with many common neurological disorders. However, current treatment options are limited to hyperosmolar agents and surgical decompression, therapies introduced more than 70 years ago. Here we show that mice deficient in aquaporin-4 (AQP4), a glial membrane water channel, have much better survival than wild-type mice in a model of brain edema caused by acute water intoxication. Brain tissue water content and swelling of pericapillary astrocytic foot processes in AQP4-deficient mice were significantly reduced. In another model of brain edema, focal ischemic stroke produced by middle cerebral artery occlusion, AQP4-deficient mice had improved neurological outcome. Cerebral edema, as measured by percentage of hemispheric enlargement at 24 h, was decreased by 35% in AQP4-deficient mice. These results implicate a key role for AQP4 in modulating brain water transport, and suggest that AQP4 inhibition may provide a new therapeutic option for reducing brain edema in a wide variety of cerebral disorders.
1,418 citations
TL;DR: Simvastatin enhanced phosphorylation of the endogenous Akt substrate endothelial nitric oxide synthase, inhibited apoptosis and accelerated vascular structure formation in vitro in an Akt-dependent manner, and promoted angiogenesis in ischemic limbs of normocholesterolemic rabbits.
Abstract: Recent studies suggest that statins can function to protect the vasculature in a manner that is independent of their lipid-lowering activity. We show here that statins rapidly activate the protein kinase Akt/PKB in endothelial cells. Accordingly, simvastatin enhanced phosphorylation of the endogenous Akt substrate endothelial nitric oxide synthase (eNOS), inhibited apoptosis and accelerated vascular structure formation in vitro in an Akt-dependent manner. Similar to vascular endothelial growth factor (VEGF) treatment, both simvastatin administration and enhanced Akt signaling in the endothelium promoted angiogenesis in ischemic limbs of normocholesterolemic rabbits. Therefore, activation of Akt represents a mechanism that can account for some of the beneficial side effects of statins, including the promotion of new blood vessel growth.
TL;DR: It is shown that statins act as direct inhibitors of induction of MHC-II expression by IFN-γ and thus as repressors of M HC-II-mediated T-cell activation, providing a new type of immunomodulation.
Abstract: Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, or statins, are effective lipid-lowering agents, extensively used in medical practice. Statins have never been shown to be involved in the immune response, although a report has indicated a better outcome of cardiac transplantation in patients under Pravastatin therapy. Major histocompatibility complex class II (MHC-II) molecules are directly involved in the activation of T lymphocytes and in the control of the immune response. Whereas only a limited number of specialized cell types express MHC-II constitutively, numerous other cells become MHC-II positive upon induction by interferon gamma (IFN-gamma). This complex regulation is under the control of the transactivator CIITA (refs 6,7). Here we show that statins act as direct inhibitors of induction of MHC-II expression by IFN-gamma and thus as repressors of MHC-II-mediated T-cell activation. This effect of statins is due to inhibition of the inducible promoter IV of the transactivator CIITA and is observed in several cell types, including primary human endothelial cells (ECs) and monocyte-macrophages (Mstraight phi). It is of note that this inhibition is specific for inducible MHC-II expression and does not concern constitutive expression of CIITA and MHC-II. In repressing induction of MHC-II, and subsequent T-lymphocyte activation, statins therefore provide a new type of immunomodulation. This unexpected effect provides a scientific rationale for using statins as immunosuppressors, not only in organ transplantation but in numerous other pathologies as well.
TL;DR: It is demonstrated that antibodies can affect transmission and subsequent disease course after vaginal SHIV-challenge, and the data begin to define the type of antibody response that could play a role in protection against mucosal transmission of HIV-1.
Abstract: The development of the human immunodeficiency virus-1 (HIV-1)/simian immunodeficiency virus (SIV) chimeric virus macaque model (SHIV) permits the in vivo evaluation of anti-HIV-1 envelope glycoprotein immune responses. Using this model, others, and we have shown that passively infused antibody can protect against an intravenous challenge. However, HIV-1 is most often transmitted across mucosal surfaces and the intravenous challenge model may not accurately predict the role of antibody in protection against mucosal exposure. After controlling the macaque estrous cycle with progesterone, anti-HIV-1 neutralizing monoclonal antibodies 2F5 and 2G12, and HIV immune globulin were tested. Whereas all five control monkeys displayed high plasma viremia and rapid CD4 cell decline, 14 antibody-treated macaques were either completely protected against infection or against pathogenic manifestations of SHIV-infection. Infusion of all three antibodies together provided the greatest amount of protection, but a single monoclonal antibody, with modest virus neutralizing activity, was also protective. Compared with our previous intravenous challenge study with the same virus and antibodies, the data indicated that greater protection was achieved after vaginal challenge. This study demonstrates that antibodies can affect transmission and subsequent disease course after vaginal SHIV-challenge; the data begin to define the type of antibody response that could play a role in protection against mucosal transmission of HIV-1.
TL;DR: It is shown that acute administration of angiopoietin-1 does indeed protect adult vasculature from leaking, countering the potentially lethal actions of VEGF and inflammatory agents.
Abstract: Pathological increases in vascular leakage lead to edema and swelling, causing serious problems in brain tumors, in diabetic retinopathy, after strokes, during sepsis and also in inflammatory conditions such as rheumatoid arthritis and asthma. Although many agents and disease processes increase vascular leakage, no known agent specifically makes vessels resistant to leaking. Vascular endothelial growth factor (VEGF) and the angiopoietins function together during vascular development, with VEGF acting early during vessel formation, and angiopoietin-1 acting later during vessel remodeling, maturation and stabilization. Although VEGF was initially called vascular permeability factor, there has been less focus on its permeability actions and more effort devoted to its involvement in vessel growth and applications in ischemia and cancer. Recent transgenic approaches have confirmed the profound permeability effects of VEGF (refs. 12-14), and have shown that transgenic angiopoietin-1 acts reciprocally as an anti-permeability factor when provided chronically during vessel formation, although it also profoundly affects vascular morphology when thus delivered. To be useful clinically, angiopoietin-1 would have to inhibit leakage when acutely administered to adult vessels, and this action would have to be uncoupled from its profound angiogenic capabilities. Here we show that acute administration of angiopoietin-1 does indeed protect adult vasculature from leaking, countering the potentially lethal actions of VEGF and inflammatory agents.
TL;DR: Assessment of the contribution of the pro-inflammatory cytokine interleukin (IL)-6 to the increased resistance of mucosal T cells against apoptosis in Crohn disease indicates that a pathway of T-cell activation driven by IL-6–sIL-6R contributes to the perpetuation of chronic intestinal inflammation.
Abstract: The pro-inflammatory cytokine interleukin (IL)-6 (refs. 1-5) can bind to cells lacking the IL-6 receptor (IL-6R) when it forms a complex with the soluble IL-6R (sIL-6R) (trans signaling). Here, we have assessed the contribution of this system to the increased resistance of mucosal T cells against apoptosis in Crohn disease (CD), a chronic inflammatory disease of the gastrointestinal tract. A neutralizing antibody against IL-6R suppressed established experimental colitis in various animal models of CD mediated by type 1 T-helper cells, by inducing apoptosis of lamina propria T cells. Similarly, specific neutralization of sIL-6R in vivo by a newly designed gp130-Fc fusion protein caused suppression of colitis activity and induction of apoptosis, indicating that sIL-6R prevents mucosal T-cell apoptosis. In patients with CD, mucosal T cells showed strong evidence for IL-6 trans signaling, with activation of signal transducer and activator of transcription 3, bcl-2 and bcl-xl. Blockade of IL-6 trans signaling caused T-cell apoptosis, indicating that the IL-6-sIL-6R system mediates the resistance of T cells to apoptosis in CD. These data indicate that a pathway of T-cell activation driven by IL-6-sIL-6R contributes to the perpetuation of chronic intestinal inflammation. Specific targeting of this pathway may be a promising new approach for the treatment of CD.
TL;DR: The data support the possibility of the transplantability of mesenchymal stem cells and their potential utility in tissue engineering, and cellular and gene therapy applications, and seem to have unique immunologic characteristics that allow persistence in a xenogeneic environment.
Abstract: Mesenchymal stem cells are multipotent cells that can be isolated from adult bone marrow and can be induced in vitro and in vivo to differentiate into a variety of mesenchymal tissues, including bone, cartilage, tendon, fat, bone marrow stroma, and muscle1,2. Despite their potential clinical utility for cellular and gene therapy, the fate of mesenchymal stem cells after systemic administration is mostly unknown. To address this, we transplanted a well-characterized human mesenchymal stem cell population3 into fetal sheep early in gestation, before and after the expected development of immunologic competence. In this xenogeneic system, human mesenchymal stem cells engrafted and persisted in multiple tissues for as long as 13 months after transplantation. Transplanted human cells underwent site-specific differentiation into chondrocytes, adipocytes, myocytes and cardiomyocytes, bone marrow stromal cells and thymic stroma. Unexpectedly, there was long-term engraftment even when cells were transplanted after the expected development of immunocompetence. Thus, mesenchymal stem cells maintain their multipotential capacity after transplantation, and seem to have unique immunologic characteristics that allow persistence in a xenogeneic environment. Our data support the possibility of the transplantability of mesenchymal stem cells and their potential utility in tissue engineering, and cellular and gene therapy applications.
TL;DR: A phase II trial of a combination of intratumoral ONYX-015 injection with cisplatin and 5-fluorouracil in patients with recurrent squamous cell cancer of the head and neck found substantial objective responses, including a high proportion of complete responses.
Abstract: ONYX-015 is an adenovirus with the E1B 55-kDa gene deleted, engineered to selectively replicate in and lyse p53-deficient cancer cells while sparing normal cells. Although ONYX-015 and chemotherapy have demonstrated anti-tumoral activity in patients with recurrent head and neck cancer, disease recurs rapidly with either therapy alone. We undertook a phase II trial of a combination of intratumoral ONYX-015 injection with cisplatin and 5-fluorouracil in patients with recurrent squamous cell cancer of the head and neck. There were substantial objective responses, including a high proportion of complete responses. By 6 months, none of the responding tumors had progressed, whereas all non-injected tumors treated with chemotherapy alone had progressed. The toxic effects that occurred were acceptable. Tumor biopsies obtained after treatment showed tumor-selective viral replication and necrosis induction.
TL;DR: It is reported that minocycline delays disease progression, inhibits casp enzyme-1 and caspase-3 mRNA upregulation, and decreases inducible nitric oxide synthetase activity, in the R6/2 mouse model of Huntington disease.
Abstract: Huntington disease is an autosomal dominant neurodegenerative disease with no effective treatment. Minocycline is a tetracycline derivative with proven safety. After ischemia, minocycline inhibits caspase-1 and inducible nitric oxide synthetase upregulation, and reduces infarction. As caspase-1 and nitric oxide seem to play a role in Huntington disease, we evaluated the therapeutic efficacy of minocycline in the R6/2 mouse model of Huntington disease. We report that minocycline delays disease progression, inhibits caspase-1 and caspase-3 mRNA upregulation, and decreases inducible nitric oxide synthetase activity. In addition, effective pharmacotherapy in R6/2 mice requires caspase-1 and caspase-3 inhibition. This is the first demonstration of caspase-1 and caspase-3 transcriptional regulation in a Huntington disease model.
TL;DR: Results indicate that thrombospondin-1, and possibly other broad-spectrum natural inhibitors of angiogenesis, act in vivo by inducing receptor-mediated apoptosis in activated microvascular endothelial cells.
Abstract: Thrombospondin-1 (TSP-1) is a naturally occurring inhibitor of angiogenesis that limits vessel density in normal tissues and curtails tumor growth. Here, we show that the inhibition of angiogenesis in vitro and in vivo and the induction of apoptosis by thrombospondin-1 all required the sequential activation of CD36, p59fyn, caspase-3 like proteases and p38 mitogen-activated protein kinases. We also detected increased endothelial cell apoptosis in situ at the margins of tumors in mice treated with thrombospondin-1. These results indicate that thrombospondin-1, and possibly other broad-spectrum natural inhibitors of angiogenesis, act in vivo by inducing receptor-mediated apoptosis in activated microvascular endothelial cells.
TL;DR: It is found that a large proportion of primary spinal afferent neurons also contain the proinflammatory neuropeptides calcitonin gene-related peptide and substance P, which mediate inflammatory edema induced by agonists of proteinase-activated receptor 2.
Abstract: Trypsin and mast cell tryptase cleave proteinase-activated receptor 2 and, by unknown mechanisms, induce widespread inflammation. We found that a large proportion of primary spinal afferent neurons, which express proteinase-activated receptor 2, also contain the proinflammatory neuropeptides calcitonin gene-related peptide and substance P. Trypsin and tryptase directly signal to neurons to stimulate release of these neuropeptides, which mediate inflammatory edema induced by agonists of proteinase-activated receptor 2. This new mechanism of protease-induced neurogenic inflammation may contribute to the proinflammatory effects of mast cells in human disease. Thus, tryptase inhibitors and antagonists of proteinase-activated receptor 2 may be useful anti-inflammatory agents.
TL;DR: It is concluded that epitopes recognized by the three monoclonal antibodies are important determinants for achieving substantial protection, thus providing a rational basis for AIDS vaccine development.
Abstract: Although maternal human immunodeficiency virus type 1 (HIV-1) transmission occurs during gestation, intrapartum and postpartum (by breast-feeding), 50-70% of all infected children seem to acquire HIV-1 shortly before or during delivery. Epidemiological evidence indicates that mucosal exposure is an important aspect of intrapartum HIV transmission. A simian immunodeficiency virus (SIV) macaque model has been developed that mimics the mucosal exposure that can occur during intrapartum HIV-1 transmission. To develop immunoprophylaxis against intrapartum HIV-1 transmission, we used SHIV-vpu+ (refs. 5,6), a chimeric simian-human virus that encodes the env gene of HIV-IIIB. Several combinations of human monoclonal antibodies against HIV-1 have been identified that neutralize SHIV-vpu+ completely in vitro through synergistic interaction. Here, we treated four pregnant macaques with a triple combination of the human IgG1 monoclonal antibodies F105, 2G12 and 2F5. All four macaques were protected against intravenous SHIV-vpu+ challenge after delivery. The infants received monoclonal antibodies after birth and were challenged orally with SHIV-vpu+ shortly thereafter. We found no evidence of infection in any infant during 6 months of follow-up. This demonstrates that IgG1 monoclonal antibodies protect against mucosal lentivirus challenge in neonates. We conclude that epitopes recognized by the three monoclonal antibodies are important determinants for achieving substantial protection, thus providing a rational basis for AIDS vaccine development.
TL;DR: Assessment of the sensitivity of hepatocytes from rat, mouse, rhesus monkey and human livers to TRAIL indicates that there are species differences in sensitivity to TRAil, and that substantial liver toxicity might result if TRAIL were used in human cancer therapy.
Abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been reported to induce apoptosis in various tumor cells but not in nontransformed, normal cells. Preclinical studies in mice and nonhuman primates have shown that administration of TRAIL can induce apoptosis in human tumors, but that no cytotoxicity to normal organs or tissues is found. The susceptibility of tumor cells to TRAIL and an apparent lack of activity in normal cells has lead to a proposal to use TRAIL in cancer therapy. Here, we assessed the sensitivity of hepatocytes from rat, mouse, rhesus monkey and human livers to TRAIL-induced apoptosis. TRAIL induced apoptosis in normal human hepatocytes in culture but not in hepatocytes isolated from the other species. Human hepatocytes showed characteristic features of apoptosis, including cytoplasmic shrinkage, the activation of caspases and DNA fragmentation. Apoptosis and cell death in human hepatocytes was massive and rapid, occurring in more than 60% of the cells exposed to TRAIL within 10 hours. These results indicate that there are species differences in sensitivity to TRAIL, and that substantial liver toxicity might result if TRAIL were used in human cancer therapy.
TL;DR: This NEP-catalyzed proteolysis limits the rate of Aβ42 catabolism, up-regulation of which could reduce the risk of developing Alzheimer's disease by preventing Aβ accumulation.
Abstract: Alzheimer amyloid beta-peptide (Abeta) is a physiological peptide constantly anabolized and catabolized under normal conditions. We investigated the mechanism of catabolism by tracing multiple-radiolabeled synthetic peptide injected into rat hippocampus. The Abeta1-42 peptide underwent full degradation through limited proteolysis conducted by neutral endopeptidase (NEP) similar or identical to neprilysin as biochemically analyzed. Consistently, NEP inhibitor infusion resulted in both biochemical and pathological deposition of endogenous Abeta42 in brain. This NEP-catalyzed proteolysis therefore limits the rate of Abeta42 catabolism, up-regulation of which could reduce the risk of developing Alzheimer's disease by preventing Abeta accumulation.
TL;DR: Glutamate excitotoxicity seems to be an important mechanism in autoimmune demyelination, and its prevention with AMPA/kainate antagonists may prove to be a effective therapy for multiple sclerosis.
Abstract: Glutamate excitotoxicity mediated by the AMPA/kainate type of glutamate receptors damages not only neurons but also the myelin-producing cell of the central nervous system, the oligodendrocyte. In multiple sclerosis, myelin, oligodendrocytes and some axons are lost as a result of an inflammatory attack on the central nervous system. Because glutamate is released in large quantities by activated immune cells, we expected that during inflammation in MS, glutamate excitotoxicity might contribute to the lesion. We addressed this by using the AMPA/kainate antagonist NBQX to treat mice sensitized for experimental autoimmune encephalomyelitis, a demyelinating model that mimics many of the clinical and pathologic features of multiple sclerosis. Treatment resulted in substantial amelioration of disease, increased oligodendrocyte survival and reduced dephosphorylation of neurofilament H, an indicator of axonal damage. Despite the clinical differences, treatment with NBQX had no effect on lesion size and did not reduce the degree of central nervous system inflammation. In addition, NBQX did not alter the proliferative activity of antigen-primed T cells in vitro, further indicating a lack of effect on the immune system. Thus, glutamate excitotoxicity seems to be an important mechanism in autoimmune demyelination, and its prevention with AMPA/kainate antagonists may prove to be an effective therapy for multiple sclerosis.
TL;DR: Vesicular stomatitis virus (VSV), an enveloped, negative-sense RNA virus exquisitely sensitive to treatment with interferon, is used as a replication-competent oncolytic virus and a new strategy for the treatment of interferons non-responsive tumors is demonstrated.
Abstract: Interferons are circulating factors that bind to cell surface receptors, activating a signaling cascade, ultimately leading to both an antiviral response and an induction of growth inhibitory and/or apoptotic signals in normal and tumor cells. Attempts to exploit the ability of interferons to limit the growth of tumors in patients has met with limited results because of cancer-specific mutations of gene products in the interferon pathway. Although interferon-non-responsive cancer cells may have acquired a growth/survival advantage over their normal counterparts, they may have simultaneously compromised their antiviral response. To test this, we used vesicular stomatitis virus (VSV), an enveloped, negative-sense RNA virus exquisitely sensitive to treatment with interferon. VSV rapidly replicated in and selectively killed a variety of human tumor cell lines even in the presence of doses of interferon that completely protected normal human primary cell cultures. A single intratumoral injection of VSV was effective in reducing the tumor burden of nude mice bearing subcutaneous human melanoma xenografts. Our results support the use of VSV as a replication-competent oncolytic virus and demonstrate a new strategy for the treatment of interferon non-responsive tumors.
TL;DR: Three patients developed exacerbations of multiple sclerosis, and in two this could be linked to altered peptide ligand treatment by immunological studies demonstrating the encephalitogenic potential of the myelin basic protein peptide in a subgroup of patients, which raise important considerations for the use of specific immunotherapies in general.
Abstract: Myelin-specific T lymphocytes are considered essential in the pathogenesis of multiple sclerosis. The myelin basic protein peptide (a.a. 83-99) represents one candidate antigen; therefore, it was chosen to design an altered peptide ligand, CGP77116, for specific immunotherapy of multiple sclerosis. A magnetic resonance imaging-controlled phase II clinical trial with this altered peptide ligand documented that it was poorly tolerated at the dose tested, and the trial had therefore to be halted. Improvement or worsening of clinical or magnetic resonance imaging parameters could not be demonstrated in this small group of individuals because of the short treatment duration. Three patients developed exacerbations of multiple sclerosis, and in two this could be linked to altered peptide ligand treatment by immunological studies demonstrating the encephalitogenic potential of the myelin basic protein peptide (a.a. 83-99) in a subgroup of patients. These data raise important considerations for the use of specific immunotherapies in general.
TL;DR: In vitro-generated pancreatic ductal epithelial cells induced to produce functioning islets showed temporal changes in mRNA transcripts for islet cell-associated differentiation markers, responded in vitro to glucose challenge, and reversed insulin-dependent diabetes after being implanted into diabetic non-obese diabetic mice.
Abstract: Ductal structures of the adult pancreas contain stem cells that differentiate into islets of Langerhans. Here, we grew pancreatic ductal epithelial cells isolated from prediabetic adult non-obese diabetic mice in long-term cultures, where they were induced to produce functioning islets containing alpha, beta and delta cells. These in vitro-generated islets showed temporal changes in mRNA transcripts for islet cell-associated differentiation markers, responded in vitro to glucose challenge, and reversed insulin-dependent diabetes after being implanted into diabetic non-obese diabetic mice. The ability to control growth and differentiation of islet stem cells provides an abundant islet source for beta-cell reconstitution in type I diabetes.
TL;DR: Caspase 8 acts as a tumor suppressor in neuroblastomas with amplification of the oncogene MYCN and is silenced through DNA methylation as well as through gene deletion.
Abstract: Caspase 8 is a cysteine protease regulated in both a death-receptor-dependent and -independent manner during apoptosis. Here, we report that the gene for caspase 8 is frequently inactivated in neuroblastoma, a childhood tumor of the peripheral nervous system. The gene is silenced through DNA methylation as well as through gene deletion. Complete inactivation of CASP8 occurred almost exclusively in neuroblastomas with amplification of the oncogene MYCN. Caspase 8-null neuroblastoma cells were resistant to death receptor- and doxorubicin-mediated apoptosis, deficits that were corrected by programmed expression of the enzyme. Thus, caspase 8 acts as a tumor suppressor in neuroblastomas with amplification of MYCN.
TL;DR: In vitro use of ribavirin triphosphate by a model viral RNA polymerase, poliovirus 3Dpol, indicates that ribvirin forces the virus into `error catastrophe' and mutagenic ribonucleosides may represent an important class of anti-RNA virus agents.
Abstract: The ribonucleoside analog ribavirin (1-beta-D-ribofuranosyl-1,2, 4-triazole-3-carboxamide) shows antiviral activity against a variety of RNA viruses and is used in combination with interferon-alpha to treat hepatitis C virus infection. Here we show in vitro use of ribavirin triphosphate by a model viral RNA polymerase, poliovirus 3Dpol. Ribavirin incorporation is mutagenic, as it templates incorporation of cytidine and uridine with equal efficiency. Ribavirin reduces infectious poliovirus production to as little as 0. 00001% in cell culture. The antiviral activity of ribavirin correlates directly with its mutagenic activity. These data indicate that ribavirin forces the virus into 'error catastrophe'. Thus, mutagenic ribonucleosides may represent an important class of anti-RNA virus agents.