A mouse model of pathological small intestinal epithelial cell apoptosis and shedding induced by systemic administration of lipopolysaccharide

Abstract

SUMMARYThe gut barrier, composed of a single layer of intestinal epithelial cells (IECs) held together by tight junctions, prevents the entrance of harmful microorganisms, antigens and toxins from the gut lumen into the blood. Small intestinal homeostasis is normally maintained by the rate of shedding of senescent enterocytes from the villus tip exactly matching the rate of generation of new cells in the crypt. However, in various localized and systemic inflammatory conditions, intestinal homeostasis can be disturbed as a result of increased IEC shedding. Such pathological IEC shedding can cause transient gaps to develop in the epithelial barrier and result in increased intestinal permeability. Although pathological IEC shedding has been implicated in the pathogenesis of conditions such as inflammatory bowel disease, our understanding of the underlying mechanisms remains limited. We have therefore developed a murine model to study this phenomenon, because IEC shedding in this species is morphologically analogous to humans. IEC shedding was induced by systemic lipopolysaccharide (LPS) administration in wild-type C57BL/6 mice, and in mice deficient in TNF-receptor 1 (Tnfr1−/−), Tnfr2 (Tnfr2−/−), nuclear factor kappa B1 (Nfκb1−/−) or Nfĸb2 (Nfĸb2−/−). Apoptosis and cell shedding was quantified using immunohistochemistry for active caspase-3, and gut-to-circulation permeability was assessed by measuring plasma fluorescence following fluorescein-isothiocyanate–dextran gavage. LPS, at doses ≥0.125 mg/kg body weight, induced rapid villus IEC apoptosis, with peak cell shedding occurring at 1.5 hours after treatment. This coincided with significant villus shortening, fluid exudation into the gut lumen and diarrhea. A significant increase in gut-to-circulation permeability was observed at 5 hours. TNFR1 was essential for LPS-induced IEC apoptosis and shedding, and the fate of the IECs was also dependent on NFκB, with signaling via NFκB1 favoring cell survival and via NFκB2 favoring apoptosis. This model will enable investigation of the importance and regulation of pathological IEC apoptosis and cell shedding in various diseases.

Chitooligosaccharides Attenuate Lipopolysaccharideinduced Inflammation and Apoptosis of Intestinal Epithelial Cells: Possible Involvement of TLR4/NF-κB Pathway.

“…20 In addition, TLR4/NF-κB signaling pathway is also considered to be a major signal transduction pathway involved in apoptosis. 21,[26][27] It has been found that LPS caused IEC apoptosis through a TLR4-dependent mechanism.…”

Intestinal permeability induced by lipopolysaccharide and measured by lactulose, rhamnose and mannitol sugars in chickens

“…Increased IP models are well established in humans (Ni et al, 2015;Piton et al, 2015), pigs , rats and mice (Williams et al, 2013;Ruan et al, 2014). Dextran sodium sulphate (DSS) ingestion, fasting (Kuttappan et al, 2015;Vicuna et al, 2015b), dexamethasone (Vicuna et al, 2015a) and wire floor stress (Wideman et al, 2012) have recently been employed as models of increased IP in chickens.…”

“…However, it has been determined that the IP of different strains is affected differently by DSS ingestion (Perše and Cerar, 2012). Lipopolysaccharide, found in the outer coat of gram-negative bacteria (Tran, 2009), has been well established as a model to increase IP in mice (Williams et al, 2013), rats (Ruan et al, 2014) and pigs . Although LPS has been used to induce systemic inflammation in chickens (Hu et al, 2011;Tan et al, 2014), limited research has been conducted regarding its effect on IP as reviewed by Gilani et al (2016).…”

Epidermal growth factor suppresses intestinal epithelial cell shedding via a MAPK dependent pathway.

“…Accelerated shedding, which can lead to infection and exacerbated immune responses (Hausmann, 2010;Knodler et al, 2010), is associated with inflammatory bowel diseases (IBD; Kiesslich et al, 2012;Liu et al, 2011) and endotoxemia (Assimakopoulos et al, 2012). This 'pathological' shedding can be induced by proinflammatory cytokines or lipopolysaccharide (Williams et al, 2013). However, little is known about regulation of constitutive physiological shedding, and especially about signals that repress it.…”