title: Increase of MCP-1 (CCL2) in myelin mutant Schwann cells is mediated by MEK-ERK signaling pathway.
abstract: Macrophages are critically involved in the pathogenesis of genetically caused demyelination, as it occurs in inherited demyelinating neuropathies. On the basis of the observation that upregulation of the Schwann cell-derived chemokine MCP-1 (CCL2) is a pathologically relevant mechanism for macrophage activation in mice heterozygously deficient for the myelin component P0 (P0+/-), we posed the question of the intracellular signaling cascade involved. By using western blot analysis of peripheral nerve lysates the MAP-kinases extracellular signal-regulated kinase 1/2 (ERK1/2) and MAP kinase/ERK kinase 1/2 (MEK1/2) showed an early and constantly increasing activation in P0 mutants. Furthermore, in nerve fibers from the P0+/- mutants, Schwann cell nuclei were much more often positive for phosphorylated ERK1/2 than in nerve fibers from wild type mice. In vitro experiments using the MEK1/2-inhibitor CI-1040 decreased ERK1/2-phosphorylation and MCP-1 expression in a Schwann cell-derived cell line. Finally, systemic application of CI-1040 lead to a decreased ERK1/2-phosphorylation and substantially reduced MCP-1-production in peripheral nerves of P0+/- mutant mice. Our study identifies MEK1/2-ERK1/2 signaling as an important intracellular pathway that connects the Schwann cell mutation with the activation of pathogenetically relevant macrophages in the peripheral nerves. These findings may have important implications for the treatment of inherited peripheral neuropathies in humans.
authors.affiliation: Department of Neurology, Developmental Neurobiology, University of Wuerzburg, Wuerzburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Fischer
authors.forename: Andreas
authors.initials: A
authors.lastname: Weishaupt
authors.forename: Jakob
authors.initials: J
authors.lastname: Troppmair
authors.forename: Rudolf
authors.initials: R
authors.lastname: Martini
mesh_terms: D000367:Age Factors; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism; D018932:Chemokine CCL2 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018993:Myelin P0 Protein / Q000172:deficiency / Q000235:genetics*; D009414:Nerve Growth Factors / Q000378:metabolism; D009442:Neurilemmoma / Q000473:pathology; D010525:Peripheral Nerves / Q000166:cytology; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism; D012583:Schwann Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D001549:Benzamides; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D004791:Enzyme Inhibitors; D018993:Myelin P0 Protein; D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D048049:Extracellular Signal-Regulated MAP Kinases