Potent anti-inflammatory and neuroprotective effects of TGF-beta1 are mediated through the inhibition of ERK and p47phox-Ser345 phosphorylation and translocation in microglia.
TGF-beta1 is one of the most potent endogenous immune modulators of inflammation. The molecular mechanism of its anti-inflammatory effect on the activation of the transcription factor NF-kappaB has been well-studied; however, the potential effects of TGF-beta1 on other proinflammatory signaling pathways is less clear. In this study, using the well-established LPS and the 1-methyl-4-phenylpyridinium-mediated models of Parkinson's disease, we demonstrate that TGF-beta1 exerts significant neuroprotection in both models via its anti-inflammatory properties. The neuroprotective effects of TGF-beta1 are mainly attributed to its ability to inhibit the production of reactive oxygen species from microglia during their activation or reactivation. Moreover, we demonstrate that TGF-beta1 inhibited LPS-induced NADPH oxidase (PHOX) subunit p47phox translocation from the cytosol to the membrane in microglia within 10 min. Mechanistic studies show that TGF-beta1 fails to protect dopaminergic neurons in cultures from PHOX knockout mice, and significantly reduced LPS-induced translocation of the PHOX cytosolic subunit p47phox to the cell membrane. In addition, LPS-induced ERK phosphorylation and subsequent Ser345 phosphorylation on p47phox were significantly inhibited by TGF-beta1 pretreatment. Taken together, our results show that TGF-beta1 exerted potent anti-inflammatory and neuroprotective properties, either through the prevention of the direct activation of microglia by LPS, or indirectly through the inhibition of reactive microgliosis elicited by 1-methyl-4-phenylpyridinium. The molecular mechanisms of TGF-beta1-mediated anti-inflammatory properties is through the inhibition of PHOX activity by preventing the ERK-dependent phosphorylation of Ser345 on p47phox in microglia to reduce oxidase activities induced by LPS.
Comprehensive Center for Inflammatory Disorders, University of North Carolina, Chapel Hill, NC 27599-7455, USA.
Li
L
Qian
Sung-Jen
SJ
Wei
Dan
D
Zhang
Xiaoming
X
Hu
Zongli
Z
Xu
Belinda
B
Wilson
Jamel
J
El-Benna
Jau-Shyong
JS
Hong
Patrick M
PM
Flood
D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D019610:Cytoprotection / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010768:Phosphoserine / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D046509:Tissue Culture Techniques; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D021122:Protein Subunits; D017382:Reactive Oxygen Species; D053773:Transforming Growth Factor beta1; D010768:Phosphoserine; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine