Intrathecal heat shock protein 60 mediates neurodegeneration and demyelination in the CNS through a TLR4- and MyD88-depe
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RESEARCH ARTICLE
Open Access
Intrathecal heat shock protein 60 mediates neurodegeneration and demyelination in the CNS through a TLR4- and MyD88-dependent pathway Karen Rosenberger1, Paul Dembny1, Katja Derkow1, Odilo Engel2, Christina Krüger1, Susanne A Wolf3, Helmut Kettenmann3, Eckart Schott4, Andreas Meisel1,2,5 and Seija Lehnardt1,5,6*
Abstract Background: Toll-like receptors (TLR) constitute a highly conserved class of receptors through which the innate immune system responds to both pathogen- and host-derived factors. Although TLRs are involved in a wide range of central nervous system (CNS) disorders including neurodegenerative diseases, the molecular events leading from CNS injury to activation of these innate immune receptors remain elusive. The stress protein heat shock protein 60 (HSP60) released from injured cells is considered an endogenous danger signal of the immune system. In this context, the main objective of the present study was to investigate the impact of extracellular HSP60 on the brain in vivo. Results: We show here that HSP60 injected intrathecally causes neuronal and oligodendrocyte injury in the CNS in vivo through TLR4-dependent signaling. Intrathecal HSP60 results in neuronal cell death, axonal injury, loss of oligodendrocytes, and demyelination in the cerebral cortex of wild-type mice. In contrast both mice lacking TLR4 and the TLR adaptor molecule MyD88 are protected against deleterious effects induced by HSP60. In contrast to the exogenous TLR4 ligand, lipopolysaccharide, intrathecal HSP60 does not induce such a considerable inflammatory response in the brain. In the CNS, endogenous HSP60 is predominantly expressed in neurons and released during brain injury, since the cerebrospinal fluid (CSF) from animals of a mouse stroke model contains elevated levels of this stress protein compared to the CSF of sham-operated mice. Conclusions: Our data show a direct toxic effect of HSP60 towards neurons and oligodendrocytes in the CNS. The fact that these harmful effects involve TLR4 and MyD88 confirms a molecular pathway mediated by the release of endogenous TLR ligands from injured CNS cells common to many forms of brain diseases that bi-directionally links CNS injury and activation of the innate immune system to neurodegeneration and demyelination in vivo. Keywords: Neurodegeneration, Innate immunity, Heat shock protein 60, Toll-like receptor, Intrathecal injection, Cerebral ischemia
Background Inflammation, neuronal injury, and demyelination are common hallmarks of most central nervous system (CNS) diseases. Innate immunity activated through Toll-like receptors (TLRs) contributes to various forms of CNS injury. TLRs are a highly conserved class of type 1 transmembrane receptors that are involved in regulation * Correspondence: [email protected] 1 Department of Neurology, Charité-Universitaetsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany 5 Cluster of Excellence NeuroCure, Charité-Universitaetsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany Full list of author infor
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