Both the parasympathetic and sympathetic nervous system exert control over innate immune responses. In inflammatory bowel disease, sympathetic innervation in intestinal mucosa is reduced. Our aim was to investigate the role of sympathetic innervation to the intestine on regulation of the innate immune responses. In lipopolysaccharide (LPS)-stimulated macrophages, we evaluated the effect of adrenergic receptor activation on cytokine production and metabolic profile. In vivo, the effect of sympathetic denervation on mucosal innate immune responses using 6-hydroxydopamine (6-OHDA), or using surgical transection of the superior mesenteric nerve (sympathectomy) was tested in Rag1−/− mice that lack T- and B-lymphocytes. In murine macrophages, adrenergic β2 receptor activation elicited a dose-dependent reduction of LPS-induced cytokines, reduced LPS-induced glycolysis and increased maximum respiration. Sympathectomy led to a significantly decreased norepinephrine concentration in intestinal tissue. Within 14 days after sympathectomy, mice developed clinical signs of colitis, colon oedema and excess colonic cytokine production. Both 6-OHDA and sympathectomy led to prominent goblet cell depletion and histological damage of colonic mucosa. We conclude that the sympathetic nervous system plays a regulatory role in constraining innate immune cell reactivity towards microbial challenges, likely via the adrenergic β2 receptor.
Clinical trials suggest that vagus nerve stimulation presents an alternative approach to classical immune suppression in Crohn's disease. T cells capable of producing acetylcholine (ChAT + T cells) in the spleen are essential mediators of the anti-inflammatory effect of vagus nerve stimulation. Besides the spleen, ChAT + T cells are found abundantly in Peyer’s patches of the small intestine. However, the role of ChAT + T cells in colitis pathogenesis is unknown. Here, we made use of CD4 cre ChAT fl/fl mice (CD4ChAT −/− mice) lacking ChAT expression specifically in CD4 + T cells. Littermates (ChAT fl/fl mice) served as controls. In acute dextran sulfate sodium (DSS)-induced colitis (7 days of 2% DSS in drinking water), CD4ChAT −/− mice showed attenuated colitis and lower intestinal inflammatory cytokine levels compared with ChAT fl/fl mice. In contrast, in a resolution model of DSS-induced colitis (5 days of 2% DSS followed by 7 days without DSS), CD4ChAT −/− mice demonstrated a worsened colitis recovery and augmented colonic histological inflammation scores and inflammatory cytokine levels as compared with ChAT fl/fl mice. In a transfer colitis model using CD4 + CD45RB high T cells, T cells from CD4ChAT −/− mice induced a similar level of colitis compared with ChAT fl/fl T cells. Together, our results indicate that ChAT + T cells aggravate the acute innate immune response upon mucosal barrier disruption in an acute DSS-induced colitis model, whereas they are supporting the later resolution process of this innate immune-driven colitis. Surprisingly, ChAT expression in T cells seems redundant in the context of T cell-driven colitis. NEW & NOTEWORTHY By using different mouse models of experimental colitis, we provide evidence that in dextran sulfate sodium-induced colitis, ChAT + T cells capable of producing acetylcholine worsen the acute immune response, whereas they support the later healing phase of this innate immune-driven colitis.
Histone deacetylase inhibitors [HDACi] exert potent anti-inflammatory effects. Because of the ubiquitous expression of HDACs, clinical utility of HDACi is limited by off-target effects. Esterase-sensitive motif [ESM] technology aims to deliver ESM-conjugated compounds to human mononuclear myeloid cells, based on their expression of carboxylesterase 1 [CES1]. This study aims to investigate utility of an ESM-tagged HDACi in inflammatory bowel disease [IBD].CES1 expression was assessed in human blood, in vitro differentiated macrophage and dendritic cells, and Crohn's disease [CD] colon mucosa, by mass cytometry, quantitative polymerase chain reaction [PCR], and immunofluorescence staining, respectively. ESM-HDAC528 intracellular retention was evaluated by mass spectrometry. Clinical efficacy of ESM-HDAC528 was tested in dextran sulphate sodium [DSS]-induced colitis and T cell transfer colitis models using transgenic mice expressing human CES1 under the CD68 promoter.CES1 mRNA was highly expressed in human blood CD14+ monocytes, in vitro differentiated and lipopolysaccharide [LPS]-stimulated macrophages, and dendritic cells. Specific hydrolysis and intracellular retention of ESM-HDAC528 in CES1+ cells was demonstrated. ESM-HDAC528 inhibited LPS-stimulated IL-6 and TNF-α production 1000 times more potently than its control, HDAC800, in CES1high monocytes. In healthy donor peripheral blood, CES1 expression was significantly higher in CD14++CD16- monocytes compared with CD14+CD16++ monocytes. In CD-inflamed colon, a higher number of mucosal CD68+ macrophages expressed CES1 compared with non-inflamed mucosa. In vivo, ESM-HDAC528 reduced monocyte differentiation in the colon and significantly improved colitis in a T cell transfer model, while having limited potential in ameliorating DSS-induced colitis.We demonstrate that monocytes and inflammatory macrophages specifically express CES1, and can be preferentially targeted by ESM-HDAC528 to achieve therapeutic benefit in IBD.
Background: Enhanced colorectal sensitivity (i.e. visceral hypersensitivity) is thought to be a pathophysiological mechanism in irritable bowel syndrome (IBS). In healthy men a circadian variation in rectal perception to colonic distention was described. Disturbed day and night rhythms, which occur in shift work and trans meridian flights, are associated with the prevalence of IBS. This raises the question whether disruptions of circadian control are responsible for the observed pathology in IBS. Prior to investigating altered rhythmicity in relation to visceral hypersensitivity in a rat model for IBS, it is relevant to establish whether normal rats display circadian variation similar to healthy men. Methodology and findings: In rodents colorectal distension leads to reproducible contractions of abdominal musculature. We used quantification of this so called visceromotor response (VMR) by electromyography (EMG) to assess visceral sensitivity in rats. We assessed the VMR in normal male Long Evans rats at different time points of the light/dark cycle. Although a control experiment with male maternal separated rats confirmed that intentionally inflicted (i.e. stress induced) changes in VMR can be detected, normal male Long Evans rats showed no variation in VMR along the light/dark cycle in response to colorectal distension.Conclusions: In the absence of a daily rhythm of colorectal sensitivity in normal control rats it is not possible to investigate possible aberrancies in our rat model for IBS.
Abstract Background Acute stress‐induced hypersensitivity to colorectal distention was shown to depend on corticotropin releasing factor (CRF)‐induced mast cell degranulation. At present it remains unclear whether CRF also induces chronic poststress activation of these cells. Accordingly, the objective of this study was to compare pre‐ and poststress CRF‐receptor antagonist treatment protocols for their ability to, respectively, prevent and reverse mast cell dependent visceral hypersensitivity in a rat model of neonatal maternal separation. Methods The visceromotor response to colonic distention was assessed in adult maternally separated and non‐handled rats before and at different time points after 1 h of water avoidance (WA). Rats were treated with the mast cell stabilizer doxantrazole and the CRF receptor‐antagonist α‐helical‐CRF (9‐41). Western blotting was used to assess mucosal protein levels of the mast cell protease RMCP‐2 and the tight junction protein occludin. Key Results In maternally separated, but not in non‐handled rats, WA induced chronic hypersensitivity (up to 30 days) to colorectal distention. Visceral hypersensitivity was prevented, but could not be reversed by administration of α‐helical‐CRF (9‐41). In contrast, however, the mast cell stabilizer doxantrazole reversed visceral hypersensitivity. Compared with vehicle‐treated rats, pre‐WA α‐helical‐CRF (9‐41) treated animals displayed higher mucosal RMCP‐2 and occludin levels. Conclusions & Inferences Water avoidance‐stress leads to persistent mast cell dependent visceral hypersensitivity in maternally separated rats, which can be prevented, but not reversed by blockade of peripheral CRF‐receptors. We conclude that persistent poststress mast cell activation and subsequent visceral hypersensitivity are not targeted by CRF‐receptor antagonists.
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