The vagus nerve as a modulator of intestinal inflammation - TI Pharma

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Chapter 4 ABSTRACT We previously reported that stimulation of the vagus nerve attenuates macrophage responses by activating the intracellular Jak2-STAT3 signaling pathway. Here, we further analyzed the potential of STAT3 to modulate TNF responses using STAT silencing strategies, pharmacological blockade, and dominant negative STAT3 constructs. We reveal that deletion of STAT3 using siRNA strategies augments the TNF production by endotoxin, confirming that STAT3 is a negative regulator of the immune response. On the other hand, pharmacological blockade of JAK2- STAT3 phosphorylation attenuates LPS-induced TNF production and NF-kB activation in macrophages. Expression of a mutant form that allows STAT3 tyrosine phosphorylation, but not STAT3 DNA binding, prevents the anti-inflammatory potential of nicotine. STAT3 inhibition specifically prevents the activation of the p65RelA/p50NF-kB1 pathway without affecting alternative other NF-kB signaling routes. These data suggest that nicotinic inhibition of inflammation in macrophages is dependent on STAT3 DNA binding and STAT3 protein, rather than STAT3 phosphorylation. Hypothetically, unphosphorylated STAT3 (U-STAT) can be important in mediating the anti-inflammatory effect of nAChR activation, via binding to NF-kB 20 and inhibition of NF-kB-activation of TNF transcription. 64
INTRODUCTION Deciphering STAT3 signaling in cholinergic immune-modulation Vagal activity has been implicated in the negative regulation of inflammatory reactions via the peripheral release of acetylcholine. Vagus nerve activity either via electrical stimulation or ablation of vagal output, has been shown to affect the disease course in experimental animal models of inflammatory conditions such as sepsis 1 , post-operative ileus 2 , colitis 3 , peritonitis 4 and arthritis 5 . This concept is based on the assumption that the vagus nerve, via peripheral release of the neurotransmitter acetylcholine (Ach), can regulate the immune response through activation of nicotinic acetylcholine receptors (nAChR) expressed on immune cells. At present, two nicotinic acetylcholine receptor (nAchR) subtypes have been put forward to be involved in this process: the nAChRα7 homopentamer 6 , and the α4β2 hetero pentamer 7 . This so called ‘cholinergic anti-inflammatory pathway’ is characterized by a nicotine dose-dependent decrease in the production of pro-inflammatory mediators, including TNF, MIP2, IL-6 and HMGB1 by macrophages 2 . In conjunction, nAChR activation has shown to inhibit NF-κB transcriptional activity 8 . Besides an effect on inflammatory properties, the cholinergic nervous system also affects more professional macrophage functions such as endo- and phagocytosis of bacteria and particles 7 . Nicotine has already been used in clinical trials for inflammatory disorders such as ulcerative colitis, but the therapeutic potential of this mechanism is hampered by the collateral toxicity of nicotine 3 . Identification and specific targeting of the intracellular signaling pathway involved in the anti-inflammatory effect of nAChR activation would increase the translational potential of this mechanism to a great extent. We previously evaluated the involvement of the janus kinase 2/signal transducer and activator of transcription 3 (JAK2-STAT3) pathway in mediating cholinergic anti-inflammatory effects in macrophages 2 . Mice, that specifically lack expression of STAT3 in their in macrophages and neutrophils, are highly susceptible to endotoxin shock and develop chronic enterocolitis 10 . Furthermore, production of inflammatory cytokines from STAT3-deficient macrophages is dramatically augmented in response to lipopolysaccharide 10 . These findings indicate that STAT3 is a potential negative regulator of inflammation. In JAK2-STAT3 signaling, cytokine receptor activation induces tyrosine phosphorylation activation of JAK2, which leads to the phosphorylation of STAT3. Upon phosphorylation, STAT3 dimerizes and translocates to the nucleus to bind specific DNA sequences, to activate genes involved in diverse functions such as cell cycle progression, apoptosis and inflammation 4 . STAT3 activation is required for both IL-10 receptor (IL-10R) and IL-6 receptor (IL-6R) signaling 5 . IL6 receptor signaling is negatively regulated through the suppressor of cytokine signaling protein SOCS3, whose expression is induced by STAT3 activation 11,6 . We previously showed that nicotine induced STAT3 phosphorylation and SOCS-3 activation and failed to decrease TNF production in macrophages transfected with an inactive form of 65
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The vagus nerve as a modulator ofin
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The vagus nerve as a modulator of i
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Promotiecommissie Promotores: Prof.
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Table of contents Chapter 1 Introdu
Page 9 and 10: Introduction and outline The aim of
Page 11 and 12: Introduction and outline Hence, the
Page 13 and 14: Introduction and outline 18. van de
Page 15 and 16: Chapter 2 ABSTRACT The cholinergic
Page 17 and 18: Chapter 2 neurotransmitter ACh with
Page 19 and 20: Chapter 2 THE VAGUS NERVE AND CHOLI
Page 21 and 22: Chapter 2 nicotine treatment impair
Page 23 and 24: Chapter 2 Figure 1. Hypothetical sc
Page 25 and 26: Chapter 2 unclear whether this hybr
Page 27 and 28: Chapter 2 reduction of NF-κB activ
Page 29 and 30: Chapter 2 CONCLUDING REMARKS The hy
Page 31 and 32: Chapter 2 34 17. The FO, Boeckxstae
Page 33 and 34: Chapter 2 55. Moser N, Mechawar N,
Page 35 and 36: Chapter 2 93. Shafique S, Dalsing M
Page 37 and 38: Chapter 3 ABSTRACT Acetylcholine re
Page 39 and 40: Chapter 3 by bowel manipulation 12
Page 41 and 42: Chapter 3 for preparation of whole
Page 43 and 44: Chapter 3 Figure 1. Nicotine attenu
Page 45 and 46: Chapter 3 Figure 2. Inhibition of m
Page 47 and 48: Chapter 3 macrophage cell lysates s
Page 49 and 50: Chapter 3 reports 2 . We next incub
Page 51 and 52: Chapter 3 Figure 5. Perioperative e
Page 53 and 54: Chapter 3 Figure 7. Stimulation of
Page 55 and 56: Chapter 3 Activation of the STAT3 c
Page 57 and 58: Chapter 3 REFERENCE LIST 60 1. Trac
Page 59: 4 CHAPTER Deciphering STAT3 signali
Page 63 and 64: Deciphering STAT3 signaling in chol
Page 69 and 70: DISCUSSION Deciphering STAT3 signal
Page 71 and 72: REFERENCES Deciphering STAT3 signal
Page 73 and 74: Chapter 5 ABSTRACT Background and A
Page 75 and 76: Chapter 5 METHODS Reagents and anti
Page 77 and 78: Chapter 5 described previously 6 .
Page 79 and 80: Chapter 5 Figure 1 Cholinergic agon
Page 81 and 82: Chapter 5 Figure 3 Cholinergic agon
Page 83 and 84: Chapter 5 we analyzed whether nicot
Page 85 and 86: Chapter 5 Zymosan induced formation
Page 87 and 88: Chapter 5 marker CD11 c (Fig. 7E),
Page 89 and 90: Chapter 5 Our data demonstrate that
Page 91 and 92: Chapter 5 REFERENCE LIST 96 1. Boro
Page 93 and 94: Thesis E.P.M. van der Zanden The va
Page 95 and 96: Summary and conclusions The goal of
Page 97 and 98: Summary and conclusions whether the
Page 99 and 100: Summary and conclusions exposure co
Page 101 and 102: REFERENCE LIST Summary and conclusi
Page 103 and 104: Nederlandse samenvatting
Page 105 and 106: Chapter 7 van STAT3 in de ‘cholin
Page 107 and 108: Chapter 7 De bevinding dat nicotine
Page 109 and 110: Chapter 7 macrofagen aan te tonen (
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Chapter 7 18. Yu Z, Zhang W, Kone B
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Shizuo Akira Department of Host Def
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List of publications
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Dankwoord
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om de ene keer olijfolie te drinken
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Curriculum Vitae Curriculum Vitae E
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