1,721,120 research outputs found
Atypical inflammation in the central nervous system in prion disease
No full textThe inflammatory response in prion diseases is dominated by microglial activation. Contrary to their profile in vitro none of the pro-inflammatory cytokines interleukin-1[beta], interleukin-6, or tumour necrosis factor-[alpha] are significantly upregulated in the ME7 model of prion disease. However, two major inflammatory mediators are elevated: transforming growth factor-[beta]1 and prostaglandin E2. This cytokine profile is the same as that reported for macrophages during phagocytosis of apoptotic cells and indeed transforming growth factor-[beta]1 and prostaglandin E2 are responsible for the downregulated phenotype of these macrophages. Transforming growth factor-[beta]1 may also have roles in extracellular matrix deposition and in amyloidogenesis and may play a direct role in disease pathogenesis. There is also now evidence to suggest that a peripheral infection, and its consequent systemic cytokine expression, may drive central nervous system cytokine expression and perhaps exacerbate disease
Transforming growth factor-beta1, the dominant cytokine in murine prion disease: influence on inflammatory cytokine synthesis and alteration of vascular extracellular matrix
No full textPrevious studies from our laboratory have shown the ME7 model of murine scrapie to be accompanied by an atypical inflammatory response that is characterized by marked astroglial and microglial activation but also by the lack of significant expression of the pro-inflammatory cytokines interleukin (IL)-1? and IL-6. The aim of this study was to determine whether, in the absence of IL-1? and IL-6, tumour necrosis factor (TNF)-? may play an equivalent pro-inflammatory role, or if an anti-inflammatory cytokine profile dominates. We have used competitive polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) to determine the levels of TNF-?, IL-10 and transforming growth factor (TGF)-?1 in the ME7 model, using their expression in lipopolysaccharide (LPS)-induced acute inflammation as a positive control. Levels of mRNA were elevated for all three cytokines during acute inflammation, while TGF-?1 mRNA alone was significantly elevated in ME7-injected brains. Similarly, by ELISA, we detected elevated IL-10, TNF-? and TGF-?1 in LPS-injected animals but only significant elevation of TGF-?1 in ME7-injected animals. An increase in laminin and collagen IV deposition around blood vessels was also observed and is consistent with up-regulation by active TGF-?1. These findings suggest that TGF-?1 may play a central role in maintenance of an atypical microglial phenotype and may also be involved in vascular and extracellular matrix change
Transforming growth factor-beta1-mediated neuroprotection against excitotoxic injury in vivo
No full textIschemic preconditioning is a phenomenon that describes how a sublethal ischemic insult can induce tolerance to subsequent ischemia. This phenomenon has been observed after focal or global ischemia in different animal models. However, the hypothesis that bacterial infection might lead to neuronal tolerance to injury has not been investigated. To mimic cerebral bacterial infection, we injected bacterial lipopolysaccharide (LPS) in the right dorsal hippocampus, followed 24 hours later by an excitotoxic lesion using kainic acid in the mouse model. Quantification of lesion size after cresyl violet counterstaining revealed that LPS pretreatment afforded neuroprotection to CA3 neurons against KA challenge. To investigate the events underlying this protection, we studied the cytokine profile induced after LPS injection. Interleukin (IL)-1 beta and transforming growth factor beta 1 (TGF-beta 1) were the main cytokines expressed at 24 hours after LPS injection. Because IL-1 beta has been described as deleterious in acute injury, we decided to investigate the function of TGF-beta 1. An adenovirus expressing a constitutively active form of TGF-beta 1 was injected intracerebrally 1 week before the induction of excitotoxic lesion, and neuronal protection was observed. To confirm the neuroprotective role of TGF-beta 1, the TGF-beta 1 adenovirus was replaced by recombinant human TGF-beta 1 protein and total neuroprotection was observed. Furthermore, the antibody-mediated blocking of TGF-beta 1 action prevented the protective effect of pretreatment with LPS. We have demonstrated in vivo that the cerebral tolerance phenomenon induced by LPS pretreatment is mediated by TGF-beta 1 cytokine.Abbreviations: ANOVA, analysis of variance; CNS, central nervous system; DAB, 3,3 -diaminobenzidine; ELISA, enzyme linked immuno assay; IL, interleukin; KA, kainic acid; LPS, lipopolysaccharide; PAI-I, plasminogen activator inhibitor; PBS, phosphate buffered saline; tPA, tissue plasminogen activator; TGF1, transforming growth factor beta 1; TNF, tumor necrosis factor alpha; Rh, recombinant huma
Comparison of inflammatory and acute-phase responses in the brain and peripheral organs of the ME7 model of prion disease
No full textChronic neurodegenerative diseases such as prion disease and Alzheimer's disease (AD) are reported to be associated with microglial activation and increased brain and serum cytokines and acute-phase proteins (APPs). Unlike AD, prion disease is also associated with a peripheral component in that the presumed causative agent, PrPSc, also accumulates in the spleen and other lymphoreticular organs. It is unclear whether the reported systemic acute-phase response represents a systemic inflammatory response to prion disease or merely reflects central nervous system (CNS) inflammation. For this study, we investigated whether intracerebrally initiated prion disease (ME7 model) provokes splenic, hepatic, or brain inflammatory and acute-phase responses. We detected no significant elevation of proinflammatory cytokines or activation of macrophages in the spleens of these animals, despite clear PrPSc deposition. Similarly, at 19 weeks we detected no significant elevation of transcripts for the APPs serum amyloid A, complement C3, pentraxin 3, and alpha2-antiplasmin in the liver, despite CNS neurodegeneration and splenic PrPSc deposition at this time. However, despite the low CNS expression levels of proinflammatory cytokines, there was robust expression of these APPs in degenerating brains. These findings suggest that PrPSc is not a stimulus for splenic macrophages and that neither peripheral PrPSc deposition nor CNS neurodegeneration is sufficient to produce a systemic acute-phase response. We also propose that serum cytokine and APP measurements are not useful during preclinical disease. Possible consequences of the clear chronic elevation of APPs in the CNS are discussed
TGF-beta1 regulates the inflammatory response during chronic neurodegeneration
No full textThe ME7 model of murine prion disease shows an atypical inflammatory response characterized by morphologically activated microglia and an anti-inflammatory cytokine profile with a marked expression of TGF?1. The investigation of the role of TGF?1 during a time course disease shows that its expression is correlated with (i) the onset of behavioral abnormalities, (ii) increased activated microglia, (iii) thickening of the basement membrane, and (iv) is associated with increased PrPsc deposition. Increasing TGF?1 using an adenoviral vector has no significant impact on prion-associated behavioral impairments or on neuropathology. In contrast, inhibition of TGF?1 activity using an adenovirus expressing decorin induces severe cerebral inflammation, expression of inducible nitric oxide synthase and acute neuronal death in prion-diseased animals only. These data suggest that TGF?1 plays a critical role in the downregulation of microglial responses minimizing brain inflammation and thus avoiding exacerbation of brain damag
Neuropathologically distinct prion strains give rise to similar temporal profiles of behavioral deficits
No full textMouse-adapted scrapie strains have been characterized by vacuolation profiles and incubation times, but the behavioral consequences have not been well studied. Here, we compared behavioral impairments produced by ME7, 79A, 22L, and 22A strains in C57BL/6J mice. We show that early impairments on burrowing, glucose consumption, nesting and open field activity, and late stage motor impairments show a very similar temporal sequence in ME7, 79A, and 22L. The long incubation time of the 22A strain produces much later impairments. However, the strains show clear late stage neuropathological differences. All strains showed clear microglial activation and synaptic loss in the hippocampus, but only ME7 and 79A showed significant CA1 neuronal death. Conversely, 22L and 22A showed significant cerebellar Purkinje neuron loss. All strains showed marked thalamic neuronal loss. These behavioral similarities coupled with clear pathological differences could serve to identify key circuits whose early dysfunction underlies the neurological effects of different prion strain
Amyloid and tau in the brain in sporadic Alzheimer’s disease: defining the chicken and the egg
Full text linkIn the October 2013 issue of Acta Neuropathologica there were three very interesting articles on: Amyloid or tau: the chicken or the egg? In the first article, David Mann and John Hardy argued that the deposition of aggregated amyloid β (Aβ) protein in the brain is a primary driving force behind the pathogenesis of Alzheimer’s disease with tau pathology following as a consequential or at least a secondary event. In the communication that followed, Braak and Del Tredici presented the contrary argument with accumulation of tau protein as the primary event in sporadic Alzheimer’s disease. Attems and Jellinger questioned the concept of a chicken and egg and suggested that the majority of cases of age-associated dementia are not caused by one single primary pathological mechanism
Neuropil and neuronal changes in hippocampal NADPH-diaphaorase histochemistry in the ME7 model of murine prion disease
No full textNitric oxide (NO) has been implicated in neurotoxicity and cerebral blood flow changes in chronic neurodegeneration, but its activity in the mammalian prion diseases has not been studied in detail. Nicotine adenine dinucleotide phosphate (NADPH)-diaphorase (NADPH-d) histochemistry is a simple and robust histochemical procedure that allows localization of the tissue distribution of NO synthases. The aim of the present study is to assess whether NADPH-d histochemical activity is altered in the hippocampus in the ME7 model of prion disease in C57BL/6J mice. At early and late stages after the initiation of the disease we assessed features of the NADPH-d positive cells and the neuropil histochemical activity in CA1 and dentate gyrus using densitometric analysis. In C57BL/6J mice 13 weeks postinjection of the prion agent ME7, when behavioural changes first become apparent, neuropil NADPH-d histochemical staining increases, whereas at late stages it decreases dramatically. Both type I and type II NADPH-d positive cells were found to survive throughout the hippocampal formation into the late stages of the disease, but diaphorase activity was reduced in dendritic branches and abnormal varicosities were present in both dendritic and axonal processes of NADPH-d positive type I cells. The pathophysiological implications of the results remain to be investigated but both blood flow alteration and NO neurotoxicity may be features of the diseas
MCP-1 and murine prion disease: separation of early behavioural dysfunction from overt clinical disease
No full textPrion diseases are chronic, fatal neurodegenerative conditions of the CNS. We have investigated the role of monocyte chemoattractant protein-1 (MCP-1) in the ME7 model of murine prion disease. MCP-1 expression increased in the CNS throughout disease progression and was positively correlated with microglial activation. We subsequently compared the inflammatory response, pathology and behavioural changes in wild-type (wt) mice and MCP-1 knockout mice (MCP-1?/?) inoculated with ME7. Late-stage clinical signs were delayed by 4 weeks in MCP-1?/? mice, and survival time increased by 2–3 weeks. By contrast, early changes in affective behaviours and locomotor activity were not delayed in onset. There was also no difference in microglial activation or neuronal death in the hippocampus and thalamus of wt mice and MCP-1?/? mice. These results highlight an important dissociation between prolonged survival, early behavioural dysfunction and hippocampal/thalamic pathology when considering therapeutic intervention for human prion diseases and other chronic neurodegenerative condition
- …
