MAC1 mediates LPS-induced production of superoxide by microglia: the role of pattern recognition receptors in dopaminergic neurotoxicity.
Microglia-derived superoxide is critical for the inflammation-induced selective loss of dopaminergic (DA) neurons, but the underlying mechanisms of microglial activation remain poorly defined. Using neuron-glia and microglia-enriched cultures from mice deficient in the MAC1 receptor (MAC1-/-), we demonstrate that lipopolysaccharide (LPS) treatment results in lower TNFalpha response, attenuated loss of DA neurons, and absence of extracellular superoxide production in MAC1-/- cultures. Microglia accumulated fluorescently labeled LPS in punctate compartments associated with the plasma membrane, intracellular vesicles, and the Golgi apparatus. Cytochalasin D (CD), an inhibitor of phagocytosis, blocked LPS internalization. However, microglia derived from Toll-like receptor 4 deficient mice and MAC1-/- mice failed to show a significant decrease in intracellular accumulation of labeled LPS, when compared with controls. Pretreatment with the scavenger receptor inhibitor, fucoidan, inhibited 79% of LPS accumulation in microglia without affecting superoxide, indicating that LPS internalization and superoxide production are mediated by separate phagocytosis receptors. Together, these data demonstrate that MAC1 is essential for LPS-induced superoxide from microglia, implicating MAC1 as a critical trigger of microglial-derived oxidative stress during inflammation-mediated neurodegeneration.
Pei
Zhong
Z
Neuropharmacology Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
Pang
Hao
H
Qian
Li
L
Yang
Sufen
S
Wang
Tonggauang
T
Zhang
Wei
W
Wu
Xeufei
X
Dallas
Shannon
S
Wilson
Belinda
B
Reece
Jeffrey M
JM
Miller
David S
DS
Hong
Jau-Shyong
JS
Block
Michelle L
ML
D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D008070:Lipopolysaccharides / Q000378:metabolism / Q000494:pharmacology*; D016177:Macrophage-1 Antigen / Q000502:physiology*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000378:metabolism* / Q000502:physiology; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D051192:Receptors, Pattern Recognition / Q000378:metabolism*; D051116:Receptors, Scavenger / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000378:metabolism
D008070:Lipopolysaccharides; D016177:Macrophage-1 Antigen; D008562:Membrane Glycoproteins; D009498:Neurotoxins; D017382:Reactive Oxygen Species; D051192:Receptors, Pattern Recognition; D051116:Receptors, Scavenger; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D013481:Superoxides; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D004298:Dopamine