期刊
EXPERIMENTAL NEUROLOGY
卷 309, 期 -, 页码 91-106出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.expneurol.2018.07.016
关键词
Inflammation; Neuropathology; Phagocytosis; Plaques; Tangles; Microglia; Interferon responses; Immunohistochemistry
资金
- National Institutes of Health, National Institutes on Aging [1R21AG044068]
- National Institute of Neurological Disorders and Stroke (National Brain and Tissue Resource for Parkinson's Disease and Related Disorders) [U24 NS072026]
- National Institute on Aging (Arizona Alzheimer's Disease Core Center) [P30 AG19610]
- Arizona Department of Health Services (Arizona Alzheimer's Research Center) [211002]
- Arizona Biomedical Research Commission [4001, 0011, 05901, 1001]
- Michael J. Fox Foundation for Parkinson's Research (The Prescott Family Initiative)
The focus of this study is the expression of Toll-like receptor-3 (TLR-3), a receptor for double-stranded RNA, in human brains affected by Alzheimer's disease (AD) pathology. Toll-like receptors are a family of pattern recognition molecules primarily involved in host defenses to microbial pathogens, but roles in neurodegenerative disease have also been shown, as amyloid beta (A beta) can be a ligand for TLR-2 and -4 and alpha-synuclein for TLR-1 and TLR-2, while TLR-9 activation promotes A beta removal. However, involvement of TLR-3 in AD has not been rigorously studied. Immunohistochemical analyses in human temporal cortical sections with a validated antibody for TLR-3 predominantly identified microglia, particularly strongly in cells associated with amyloid plaques, also brain vascular endothelial cells and subsets of astrocytes, but not neurons or p62-immunoreactive structures. Microglial TLR-3 colocalized with the endosomal/lysosomal marker CD68, which identifies phagocytic cells. Quantitative analyses of neuropathologically-staged human brain middle temporal gyrus samples using immunohistochemistry and mRNA expression methods demonstrated increased TLR-3 immunoreactivity and increased TLR-3 mRNA in AD compared to non-demented cases. There were significant positive correlations between TLR-3 mRNA levels and plaque or tangle loads in both series of samples. Increased expression of interferon beta (IFN-beta) and interferon regulatory factor (IRF)-3 mRNA, two factors induced by TLR-3 signaling, were detected in the AD cases. Increased expression of TLR-4 and TLR-9 mRNA was also observed in these same samples, but not TLR-2. In vitro cultured human brain microglia responses to A beta inflammatory activation were not altered by TLR-3 activation with activator polyinosinic;polycytidylic acid (poly I:C), while human brain endothelial cells showed reduction in responses when stimulated with both agents. Treatment of microglia with poly I:C did not increase their uptake and breakdown of A beta.
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