Amyloid peptide-induced cytokine and chemokine expression in THP-1 monocytes is blocked by small inhibitory RNA duplexes for early growth response-1 messenger RNA.
In Alzheimer's disease (AD) one finds increased deposition of A beta and also an increased presence of monocytes/macrophages in the vessel wall and activated microglial cells in the brain. AD patients show increased levels of proinflammatory cytokines by activated microglia. Here we used a human monocytic THP-1 cell line as a model for microglia to delineate the cellular signaling mechanism involved in amyloid peptides (A beta(1-40) and A beta(1-42))-induced expression of inflammatory cytokines and chemokines. We observed that A beta peptides at physiological concentrations (125 nM) increased mRNA expression of cytokines (TNF-alpha, and IL-1 beta) and chemokines (monocyte chemoattractant protein-1 (MCP-1), IL-8, and macrophage inflammatory protein-1 beta (MIP-1 beta)). The cellular signaling involved activation of c-Raf, extracellular signal-regulated kinase-1 (ERK-1)/ERK-2, and c-Jun N-terminal kinase, but not p38 mitogen-activated protein kinase. This is further supported by the data showing that A beta causes phosphorylation of ERK-1/ERK-2, which, in turn, activates Elk-1. Furthermore, A beta mediated a time-dependent increase in DNA binding activity of early growth response-1 (Egr-1) and AP-1, but not of NF-kappa B and CREB. Moreover, A beta-induced Egr-1 DNA binding activity was reduced >60% in THP-1 cells transfected with small interfering RNA duplexes for Egr-1 mRNA. We show that A beta-induced expression of TNF-alpha, IL-1 beta, MCP-1, IL-8, and MIP-1 beta was abrogated in Egr-1 small inhibitory RNA-transfected cells. Our results indicate that A beta-induced expression of cytokines (TNF-alpha and IL-1 beta) and chemokines (MCP-1, IL-8, and MIP-1 beta) in THP-1 monocytes involves activation of ERK-1/ERK-2 and downstream activation of Egr-1. The inhibition of Egr-1 by Egr-1 small inhibitory RNA may represent a potential therapeutic target to ameliorate the inflammation and progression of AD.
Giri
Ranjit K
RK
Department of Biochemistry and Molecular Biology, University of Southern California, Keck School of Medicine, Los Angeles, CA 90033, USA.
Selvaraj
Suresh K
SK
Kalra
Vijay K
VK
D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000873:Anthracenes / Q000494:pharmacology; D002478:Cells, Cultured; D018925:Chemokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000097:blood / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000097:blood / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051766:Early Growth Response Protein 1; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D009000:Monocytes / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009692:Nucleic Acid Heteroduplexes / Q000502:physiology*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000502:physiology*; D034741:RNA, Small Interfering / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured
D016229:Amyloid beta-Peptides; D000873:Anthracenes; D018925:Chemokines; D017362:Cyclic AMP Response Element-Binding Protein; D016207:Cytokines; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; D005419:Flavonoids; D017874:Immediate-Early Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D009692:Nucleic Acid Heteroduplexes; D010446:Peptide Fragments; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C497325:EGR1 protein, human; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); C432165:pyrazolanthrone; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one