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Microglia in the degenerating brain are capable of phagocytosis of beads and of apoptotic cells, but do not efficiently remove PrPSc, even upon LPS stimulation

Microglia in the degenerating brain are capable of phagocytosis of beads and of apoptotic cells, but do not efficiently remove PrPSc, even upon LPS stimulation
Microglia in the degenerating brain are capable of phagocytosis of beads and of apoptotic cells, but do not efficiently remove PrPSc, even upon LPS stimulation
Despite the phagocytic machinery available to microglia the aberrant amyloid proteins produced during Alzheimer’s and prion disease, amyloid-b and PrPSc, are inefficiently cleared. We have shown that microglia in the ME7 model of prion disease show morphological evidence of activation, synthesize low levels of pro-inflammatory cytokines and are primed to produce exaggerated responses to subsequent inflammatory challenges. Whether these microglia engage in significant phagocytic activity in the disease per se, or upon subsequent inflammatory challenge is not clear. In the present study we show transcriptional activation of a large number of scavenger receptors (SRs), matrix metallo- proteinases (MMPs), oxidative enzymes, and cathepsins in ME7 animals. Hippocampally-injected inert latex beads (6 µm) are efficiently phagocytosed by microglia of ME7 prion- diseased animals, but not by microglia in normal animals. Stimulation of ME7 animals with systemic bacterial endotoxin (lipopolysaccharide, LPS) induced further increases in SR-A2, MMP3, and urokinase plasminogen activator receptor (uPAR) but decreased, or did not alter, transcription of most phagocytosis-related genes examined and did not enhance clearance of deposited PrPSc. Furthermore, intra-cerebral injection with LPS (0.5 µg) induced marked micro- glial production of IL-1b, robust cellular infiltration and marked apoptosis but also did not induce further clearance of PrPSc. These data indicate that microglia in the prion- diseased brain are capable of phagocytosis per se, but show limited efficacy in removing PrPSc even upon marked escalation of CNS inflammation. Furthermore, microglia/macro- phages remain IL-1b-negative during phagocytosis of apoptotic cells. The data demonstrate that phagocytic activity and pro-inflammatory microglial phenotype do not necessarily correlate.
amyloid, microglia, priming, phagocytosis, activation, prion disease, apoptosis, alzheimer's disease
0894-1491
2017-2030
Hughes, Martina M.
6149ee60-694b-4c55-b8f2-349284c55d66
Field, Robert H.
fd235bed-1130-48e5-9a34-c68e5652ccb6
Perry, V.H.
8f29d36a-8e1f-4082-8700-09483bbaeae4
Murray, Carol L.
976fae1f-ac71-4c1b-9989-6087142f4b61
Cunningham, Colm
3bc1d897-f0f5-4112-abf4-1a10c2e92a6b
Hughes, Martina M.
6149ee60-694b-4c55-b8f2-349284c55d66
Field, Robert H.
fd235bed-1130-48e5-9a34-c68e5652ccb6
Perry, V.H.
8f29d36a-8e1f-4082-8700-09483bbaeae4
Murray, Carol L.
976fae1f-ac71-4c1b-9989-6087142f4b61
Cunningham, Colm
3bc1d897-f0f5-4112-abf4-1a10c2e92a6b

Hughes, Martina M., Field, Robert H., Perry, V.H., Murray, Carol L. and Cunningham, Colm (2010) Microglia in the degenerating brain are capable of phagocytosis of beads and of apoptotic cells, but do not efficiently remove PrPSc, even upon LPS stimulation. GLIA, 58 (16), 2017-2030. (doi:10.1002/glia.21070). (PMID:20878768)

Record type: Article

Abstract

Despite the phagocytic machinery available to microglia the aberrant amyloid proteins produced during Alzheimer’s and prion disease, amyloid-b and PrPSc, are inefficiently cleared. We have shown that microglia in the ME7 model of prion disease show morphological evidence of activation, synthesize low levels of pro-inflammatory cytokines and are primed to produce exaggerated responses to subsequent inflammatory challenges. Whether these microglia engage in significant phagocytic activity in the disease per se, or upon subsequent inflammatory challenge is not clear. In the present study we show transcriptional activation of a large number of scavenger receptors (SRs), matrix metallo- proteinases (MMPs), oxidative enzymes, and cathepsins in ME7 animals. Hippocampally-injected inert latex beads (6 µm) are efficiently phagocytosed by microglia of ME7 prion- diseased animals, but not by microglia in normal animals. Stimulation of ME7 animals with systemic bacterial endotoxin (lipopolysaccharide, LPS) induced further increases in SR-A2, MMP3, and urokinase plasminogen activator receptor (uPAR) but decreased, or did not alter, transcription of most phagocytosis-related genes examined and did not enhance clearance of deposited PrPSc. Furthermore, intra-cerebral injection with LPS (0.5 µg) induced marked micro- glial production of IL-1b, robust cellular infiltration and marked apoptosis but also did not induce further clearance of PrPSc. These data indicate that microglia in the prion- diseased brain are capable of phagocytosis per se, but show limited efficacy in removing PrPSc even upon marked escalation of CNS inflammation. Furthermore, microglia/macro- phages remain IL-1b-negative during phagocytosis of apoptotic cells. The data demonstrate that phagocytic activity and pro-inflammatory microglial phenotype do not necessarily correlate.

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Published date: December 2010
Keywords: amyloid, microglia, priming, phagocytosis, activation, prion disease, apoptosis, alzheimer's disease

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Local EPrints ID: 180191
URI: http://eprints.soton.ac.uk/id/eprint/180191
ISSN: 0894-1491
PURE UUID: 8d8a579c-df9d-4fab-b65f-a970f536cb04

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Date deposited: 06 Apr 2011 08:25
Last modified: 14 Mar 2024 02:51

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Contributors

Author: Martina M. Hughes
Author: Robert H. Field
Author: V.H. Perry
Author: Carol L. Murray
Author: Colm Cunningham

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