Poly(ADP-ribose) polymerase-1 promotes microglial activation, proliferation, and matrix metalloproteinase-9-mediated neuron death.
Activated microglia contribute to cell death in ischemic and neurodegenerative disorders of the CNS. Microglial activation is regulated in part by NF-kappaB, and the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) enhances NF-kappaB binding to DNA. In this study, the role of PARP-1 in microglia-mediated neurotoxicity was assessed using microglia from wild-type (wt) and PARP-1-/- mice. Cultured microglia were incubated with TNF-alpha, a cytokine that is up-regulated in many neurological disorders. When stimulated with TNF-alpha, wt microglia proliferated, underwent morphological changes characteristic of activation, and killed neurons placed in coculture. The effects of TNF-alpha were markedly attenuated both in PARP-1-/- microglia and in wt microglia treated with the PARP enzymatic inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2h)-isoquinolinone. These effects were also blocked by (E)-3-(4-methylphenylsulfonyl)-2-propenenenitrile, which inhibits translocation of NF-kappaB to the nucleus. TNF-alpha also up-regulated microglial release of matrix metalloproteinase-9 (MMP-9), an enzyme with potential neurotoxic properties that is transcriptionally regulated by NF-kappaB. This up-regulation was blocked in PARP-1-/- microglia and in wt microglia by the PARP inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2h)-isoquinolinone. Microglia from MMP-9-/- mice were used to evaluate the contribution of MMP-9 to microglial neurotoxicity. MMP-9-/- microglia treated with TNF-alpha showed substantially reduced neurotoxicity relative to the wt microglia. TNF-alpha-stimulated wt microglia treated with the MMP inhibitor ilomastat also showed reduced neurotoxicity. These findings suggest that PARP-1 activation is required for both TNF-alpha-induced microglial activation and the neurotoxicity resulting from TNF-alpha-induced MMP-9 release.
Kauppinen
Tiina M
TM
Department of Neurology, University of California, and Veterans Affairs Medical Center, San Francisco, CA 94121, USA.
Swanson
Raymond A
RA
D000818:Animals; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020780:Matrix Metalloproteinase 9 / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D061965:Matrix Metalloproteinase Inhibitors; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D009474:Neurons / Q000201:enzymology* / Q000473:pathology*; D000071137:Poly (ADP-Ribose) Polymerase-1; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D004791:Enzyme Inhibitors; D061965:Matrix Metalloproteinase Inhibitors; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D014409:Tumor Necrosis Factor-alpha; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D020780:Matrix Metalloproteinase 9