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.
Department of Biochemistry and Molecular Biology, University of Southern California, Keck School of Medicine, Los Angeles, CA 90033, USA.
Ranjit K
RK
Giri
Suresh K
SK
Selvaraj
Vijay K
VK
Kalra
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