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Review
. 2014 Jan 7;20(1):64-77.
doi: 10.3748/wjg.v20.i1.64.

Inflammatory pathways of importance for management of inflammatory bowel disease

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Review

Inflammatory pathways of importance for management of inflammatory bowel disease

Jannie Pedersen et al. World J Gastroenterol. .

Abstract

Inflammatory bowel disease (IBD) is a group of chronic disorders of the gastrointestinal tract comprising Crohn's disease (CD) and ulcerative colitis (UC). Their etiologies are unknown, but they are characterised by an imbalanced production of pro-inflammatory mediators, e. g. , tumor necrosis factor (TNF)-α, as well as increased recruitment of leukocytes to the site of inflammation. Advantages in understanding the role of the inflammatory pathways in IBD and an inadequate response to conventional therapy in a large portion of patients, has over the last two decades lead to new therapies which includes the TNF inhibitors (TNFi), designed to target and neutralise the effect of TNF-α. TNFi have shown to be efficient in treating moderate to severe CD and UC VSports手机版. However, convenient alternative therapeutics targeting other immune pathways are needed for patients with IBD refractory to conventional therapy including TNFi. Indeed, several therapeutics are currently under development, and have shown success in clinical trials. These include antibodies targeting and neutralising interleukin-12/23, small pharmacologic Janus kinase inhibitors designed to block intracellular signaling of several pro-inflammatory cytokines, antibodies targeting integrins, and small anti-adhesion molecules that block adhesion between leukocytes and the intestinal vascular endothelium, reducing their infiltration into the inflamed mucosa. In this review we have elucidated the major signaling pathways of clinical importance for IBD therapy and highlighted the new promising therapies available. As stated in this paper several new treatment options are under development for the treatment of CD and UC, however, no drug fits all patients. Hence, optimisations of treatment regimens are warranted for the benefit of the patients either through biomarker establishment or other rationales to maximise the effect of the broad range of mode-of-actions of the present and future drugs in IBD. .

Keywords: Anti-tumor necrosis factor; Biologics; Crohn’s disease; Pro-inflammatory cytokines; Signaling pathways; Treatment; Ulcerative colitis V体育安卓版. .

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Figures

Figure 1
Figure 1
Mechanism of action of anti-tumor necrosis factor biologics and inhibitors of Janus kinase/signal transducer and activator of transcription signaling. Left panel: Anti-tumor necrosis factor (TNF) biologics bind to homotrimeric TNF-α [transmembrane (tmTNF-α) and/or soluble (sTNF-α)], thereby blocking the interaction between the cytokine and TNF-α receptor type 1 and 2 (TNFR1 and TNFR2) to neutralise TNF-α-mediated pro-inflammatory signaling. Infliximab is shown as a representative anti-TNF biologics to illustrate the mechanism of action of the four agents labeled for IBD: Infliximab (a chimeric antibody), adalimumab and golimumab (fully human antibodies), and certolizumab pegol (a pegylated Fab fragment of a humanised anti-TNF antibody). Right panel: The fully human antibody against interleukin (IL)-12/23, ustekinumab, binds to the common p40 subunit of IL-12 and IL-23 heterodimers and prevents the interaction of IL-12 and IL-23 with their cognate receptors, IL-12R and IL-23R, hence neutralising IL-12/23-mediated intracellular signaling. Tofacitinib is a small molecule inhibitor of Janus kinase (JAK) activity that prevents the JAK-dependent phosphorylation of signal transducer and activator of transcription (STAT) proteins and subsequently the STAT-induced transcription of pro-inflammatory target genes.
Figure 2
Figure 2
Integrin and chemokine inhibitors in intestinal endothelium. Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) and vascular adhesion molecule-1 (VCAM-1) adhesion molecules become up-regulated on the endothelium during intestinal inflammation. In the small and large intestine (upper panel) the adhesion molecule MAdCAM-1 functions as docking site for integrins α4β1 and α4β7 expressed by T-cells. Contrary, the adhesion molecule VCAM-1 also acts as docking molecule for α4β1. Addition of the inhibitory α4β1 antibody, natalizumab, thus blocks adhesion of T-cells to the entire intestinal mucosa. As VCAM-1 is additionally expressed within the central nervous system (CNS), natalizumab also blocks T-cell extravasation and hence limits immune surveillance of the CNS which might lead to progressive multifocal leukoencephalopathy. Using the α4β7 inhibitory antibody, vedolizumab, only the adhesion of T-cells to the intestine specific MAdCAM-1 is blocked, and thus does not limit immune surveillance of the CNS while dampening the inflammatory response. In the endothelium of the small intestine (lower panel) the chemokine ligand 25 (CCL25) adhesion molecule is predominantly expressed during inflammation. It acts as a ligand for the chemokine receptor 9 (CCR9) on T-cells. The inhibitor vercirnon blocks the CCL25-CCR9 chemotaxis thus inhibiting T-cells adhesion to the small intestinal mucosa. Vercirnon was recently withdrawn following a phase III trial.

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