Abstract
Rosmarinic acid (RosA) is a hydroxylated compound frequently found in herbal plants and is mostly responsible for anti-inflammatory and antioxidative activity. Previously, we observed that RosA inhibited T-cell antigen receptor (TCR)- induced interleukin 2 (IL-2) expression and subsequent T-cell proliferation in vitro. In this study, we investigated in detail inhibitory mechanism of RosA on TCR signaling, which ultimately activates IL-2 promoter by activating transcription factors, such as nuclear factor of activated T cells (NF-AT) and activating protein-1 (AP-1). Interestingly, RosA inhibited NF-AT activation but not AP-1, suggesting that RosA inhibits Ca(2+)-dependent signaling pathways only. Signaling events upstream of NF-AT activation, such as the generation of inositol 1,4,5-triphosphate and Ca(2+) mobilization, and tyrosine phosphorylation of phospholipase C-gamma 1 (PLC-gamma 1) were strongly inhibited by RosA. Tyrosine phosphorylation of PLC-gamma 1 is largely dependent on 3 kinds of protein tyrosine kinases (PTKs), ie, Lck, ZAP-70, and Itk. We found that RosA efficiently inhibited TCR-induced tyrosine phosphorylation and subsequent activation of Itk but did not inhibit Lck or ZAP-70. ZAP-70-dependent signaling pathways such as the tyrosine phosphorylation of LAT and SLP-76 and serine/threonine phosphorylation of mitogen-activated protein kinases (MAPKs) were intact in the presence of RosA, confirming that RosA suppresses TCR signaling in a ZAP-70-independent manner. Therefore, we conclude that RosA inhibits TCR signaling leading to Ca(2+) mobilization and NF-AT activation by blocking membrane-proximal events, specifically, the tyrosine phosphorylation of inducible T cells kinase (Itk) and PLC-gamma 1.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Animals
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Anti-Inflammatory Agents, Non-Steroidal / pharmacology*
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Calcium Signaling / drug effects*
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Carrier Proteins / metabolism
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Cinnamates / pharmacology*
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DNA-Binding Proteins / metabolism
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Depsides
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology*
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GRB2 Adaptor Protein
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Humans
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Jurkat Cells / drug effects*
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Jurkat Cells / enzymology
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Jurkat Cells / immunology
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Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / physiology
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Membrane Proteins*
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Mice
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Mice, Inbred BALB C
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases / metabolism
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Muromonab-CD3 / pharmacology
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NFATC Transcription Factors
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Nuclear Proteins*
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Phospholipase C gamma
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Phosphoproteins / metabolism
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Phosphorylation / drug effects
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Protein Processing, Post-Translational / drug effects
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Protein-Tyrosine Kinases / antagonists & inhibitors*
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Protein-Tyrosine Kinases / physiology
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Proteins / metabolism
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Receptors, Antigen, T-Cell / drug effects*
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Receptors, Antigen, T-Cell / immunology
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Rosmarinic Acid
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Transcription Factors / metabolism
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Type C Phospholipases / antagonists & inhibitors*
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ZAP-70 Protein-Tyrosine Kinase
Substances
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Adaptor Proteins, Signal Transducing
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Anti-Inflammatory Agents, Non-Steroidal
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Carrier Proteins
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Cinnamates
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DNA-Binding Proteins
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Depsides
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Enzyme Inhibitors
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GRB2 Adaptor Protein
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GRB2 protein, human
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Grb2 protein, mouse
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LAT protein, human
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Lat protein, mouse
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Membrane Proteins
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Muromonab-CD3
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NFATC Transcription Factors
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Nuclear Proteins
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Phosphoproteins
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Proteins
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Receptors, Antigen, T-Cell
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SLP-76 signal Transducing adaptor proteins
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Transcription Factors
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Protein-Tyrosine Kinases
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Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
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ZAP-70 Protein-Tyrosine Kinase
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ZAP70 protein, human
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Zap70 protein, mouse
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emt protein-tyrosine kinase
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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Type C Phospholipases
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Phospholipase C gamma