Sympathetic activity regulates epithelial proliferation and wound healing via adrenergic receptor α2A

Innervation of the intestinal mucosa by the sympathetic nervous system is well described but the effects of adrenergic receptor stimulation on the intestinal epithelium remain equivocal. We therefore investigated the effect of sympathetic neuronal activation on intestinal cells in mouse models and organoid cultures, to identify the molecular routes involved. Using publicly available single-cell RNA sequencing datasets we show that the α2A isoform is the most abundant adrenergic receptor in small intestinal epithelial cells. Stimulation of this receptor with norepinephrine or a synthetic specific α2A receptor agonist promotes epithelial proliferation and stem cell function, while reducing differentiation in vivo and in intestinal organoids. In an anastomotic healing mouse model, adrenergic receptor α2A stimulation resulted in improved anastomotic healing, while surgical sympathectomy augmented anastomotic leak. Furthermore, stimulation of this receptor led to profound changes in the microbial composition, likely because of altered epithelial antimicrobial peptide secretion. Thus, we established that adrenergic receptor α2A is the molecular delegate of intestinal epithelial sympathetic activity controlling epithelial proliferation, differentiation, and host defense. Therefore, this receptor could serve as a newly identified molecular target to improve mucosal healing in intestinal inflammation and wounding.

Neuronal innervation of the intestinal crypt

Mucosal damage is a key feature of inflammatory bowel diseases (IBD) and healing of the mucosa is an endpoint of IBD treatment that is often difficult to achieve. Autonomic neurons of the parasympathetic and sympathetic nervous system may influence intestinal epithelial cell growth and modulating epithelial innervation could for that reason serve as an interesting therapeutic option to improve mucosal healing. Understanding of the biological processes triggered by nonspecific and specific epithelial adrenergic and cholinergic receptor activation is of key importance. At present, with rising technological advances, bioelectronic neuromodulation as treatment modality has gained momentum. We discuss the current view on state-of-the-art innervation of the intestinal crypt and its impact on epithelial cell growth and differentiation. Furthermore, we outline bioelectronic technology and review its relevance to wound healing processes.

The role of nicotinic receptors in SARS-CoV-2 receptor ACE2 expression in intestinal epithelia

Background

Recent evidence demonstrated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) propagates in intestinal epithelial cells expressing Angiotensin-Converting Enzyme 2 (ACE2), implying that these cells represent an important entry site for the viral infection. Nicotinic receptors (nAChRs) have been put forward as potential regulators of inflammation and of ACE2 expression. As vagus nerve stimulation (VNS) activates nAChRs, we aimed to investigate whether VNS can be instrumental in affecting intestinal epithelial ACE2 expression.

Methods

By using publicly available datasets we qualified epithelial ACE2 expression in human intestine, and assessed gene co-expression of ACE2 and SARS-CoV-2 priming Transmembrane Serine Protease 2 (TMPRSS2) with nAChRs in intestinal epithelial cells. Next, we investigated mouse and human ACE2 expression in intestinal tissues after chronic VNS via implanted devices.

Results

We show co-expression of ACE2 and TMPRSS2 with nAChRs and α7 nAChR in particular in intestinal stem cells, goblet cells, and enterocytes. However, VNS did not affect ACE2 expression in murine or human intestinal tissue, albeit in colitis setting.

Conclusions

ACE2 and TMPRSS2 are specifically expressed in epithelial cells of human intestine, and both are co-expressed with nAChRs. However, no evidence for regulation of ACE2 expression through VNS could be found. Hence, a therapeutic value of VNS with respect to SARS-CoV-2 infection risk through ACE2 receptor modulation in intestinal epithelia could not be established.

Similar Short- and Long-term Colectomy Rates with Ciclosporin and Infliximab Treatment in Hospitalised Ulcerative Colitis Patients

BACKGROUND AND AIMS

Ciclosporin A [CsA] and infliximab [IFX] are similarly effective in preventing short-term colectomy in ulcerative colitis [UC] patients, but long-term data are scarce. We aimed to compare short- and long-term efficacy of CsA and IFX by analysing colectomy rates and failure of remission-induction treatment as outcome parameters for treatment success.

METHODS

We retrospectively studied hospitalised UC patients who received CsA or IFX for moderate-to-severe UC, between January 2000 and April 2014. The primary endpoint was time to colectomy, and treatment failure [defined as colectomy or another remission-induction treatment with corticosteroids, CsA, or IFX] was used as secondary endpoint. Variables possibly affecting colectomy outcomes were analysed.

RESULTS

A total of 55 patients were studied for colectomy outcome and 58 patients for treatment failure. A significantly longer follow-up duration was available for CsA-treated patients [p < 0.001, both subcohorts]. Patients showed comparable patient- and disease-specific characteristics. Colectomy rates did not differ significantly at 3, 12, and 36 months: 36% versus 29%, 58% versus 48%, and 64% versus 67% for CsA- and IFX-treated patients, respectively. Multivariate Cox regression analysis revealed the lowest hazard ratio [HR] for colectomy in patients concomitantly using thiopurines: HR 0.28 (confidence interval [CI] 0.13-0.64), p = 0.002. Treatment failure rates were not significantly different at 3, 12 and 36 months: 35% versus 48%, 51% versus 68%, and 62% versus 83% for CsA- and IFX-treated patients, respectively.

CONCLUSIONS

Treatment with CsA and IFX is similarly effective in preventing short- and long-term colectomy in hospitalised UC patients. Furthermore, failure rates of these remission-induction treatments were comparable.