Disruption of the Mucosal Barrier During Gut Ischemia Allows Entry of Digestive Enzymes Into the Intestinal Wall

Abstract

Intestinal ischemia is associated with high morbidity and mortality but the underlying mechanisms are uncertain. We hypothesize that during ischemia the intestinal mucosal barrier becomes disrupted, allowing digestive enzymes access into the intestinal wall initiating autodigestion. We used a rat model of splanchnic ischemia by occlusion of the superior mesenteric and celiac arteries up to 30 min with and without luminal injection of tranexamic acid as a trypsin inhibitor. We determined the location and activity of digestive proteases on intestinal sections with in-situ zymography and we examined the disruption of two components of the mucosal barrier: mucin isoforms and the extra- and intracellular domains of E-cadherin with immunohistochemistry and western blot techniques. The results indicate that non-ischemic intestine has low levels of protease activity in its wall. After 15 min ischemia protease activity was visible at the tip of the villi and after 30 min enhanced activity was seen across the full thickness of the intestinal wall. This activity was accompanied by disruption of the mucin layer and loss of both intra- and extracellular domains of E-cadherin. Digestive protease inhibition in the intestinal lumen with tranexamic acid reduced morphological damage and entry of digestive enzymes into the intestinal wall. This study demonstrates that disruption of the mucosal epithelial barrier within minutes of intestinal ischemia allows entry of fully activated pancreatic digestive proteases across the intestinal barrier triggering autodigestion.

Diagnosis biomarkers in acute intestinal ischemic injury: so close, yet so far

“…Degradation products of pancreatic enzymes, residues of bacterial products pass through the lymphatic, hematogenous or peritoneal barrier and are likely to induce not only a loco-regional but also a systemic reaction [19,20]. In animal models, inhibition of these enzymes results in a decrease in intra-parietal micro-bleeding, systemic inflammatory response, and even in mortality in some studies [21]. The action of these enzymes would involve degradation of inter-enterocytic tight junction's proteins such as E-cadherin.…”

“…Aside from its barrier function, the gut contains growth factors, adenosine and hormones, which are potential mediators of the modulation of intestinal inflammation and repair, due to their roles in cellular proliferation, differentiation, migration, apoptosis and autophagy [18][19][20][21][22]. Physiologically, the gut could initiate and propagate sepsis due to the ability of bacteria, endotoxins, and other antigens to translocate, along with the production of pro-inflammatory cytokines and toxins [11].…”

Nutritional Modulation of Immune Response via Vagus Nerve: Preclinical Studies and Future Perspectives

“…Whereas such barrier loss may represent a generalized phenomenon that affects epithelial function in diverse organs, various lines of experimental and clinical evidence implicate early loss of the intestinal barrier in particular as a potential therapeutic target to prevent or treat dysregulated inflammation (MacFie et al 1999;Sambol et al 2000;Fink and Delude 2005). Indeed, interventions that aim to improve intestinal integrity, including enterocyte-specific growth factor, high molecular weight polyethylene glycol, inhibition of pancreatic enzyme activity in the gut lumen, and modulation of the intestinal flora, were shown to reduce distant organ damage and improve survival during sepsis (Ewaschuk et al 2007;Clark et al 2009;Chang et al 2012).…”

The cross-talk between the kidney and the gut: implications for chronic kidney disease

“…Therefore, hypervolemia, excessive use of diuretics, and hypotensive episodes during or after dialysis can aggravate CKDinduced intestinal barrier dysfunction [7,71,72].…”