Examination of intestinal ultrastructure, bowel wall apoptosis and tight junctions in the early phase of sepsis

Abstract

Gut hyperpermeability can be caused by either apoptosis of the intestinal epithelium or altered status, permeability or porosity of tight junctions. This project aims to elucidate these mechanisms in the early phase of sepsis. Eighteen male wild type mice were randomized to two groups. All mice received one single gavage of fluorescein isothiocyanate (FITC) dextran 30 min before intervention. One group (n = 10) underwent cecal ligation and puncture to induce sepsis. The other group (n = 8) was sham operated. Septic animals exhibited significantly increased permeability for FITC 8 h post-operatively. Significantly increased serum interleukin-6, tumor-necrosis-factor-alpha and interleukin-1-beta confirmed sepsis. Septic animals showed significant bowel wall inflammation of ileum and colon samples. PCR revealed significantly increased expression of claudin-2 and decreased expressions of claudin-4, tight-junction-protein-1 and occludin-1 resembling increased permeability of tight junctions. However, these alterations could not be confirmed at the protein level. Light microscopy revealed significant dilatation of intercellular spaces at the basal sections of intestinal epithelial cells (IEC) in septic animals confirmed by increased intercellular spaces at the level of tight junctions and adherens junctions in electron microscopy (TEM). In small angle X-ray scattering no increase in number or size of nanopores could be shown in the bowel wall. HOECHST staining and PCR of ileum samples for apoptosis markers proofed no relevant differences in intestinal epithelial cell apoptosis between the groups. Intestinal hyperpermeability in septic animals was most likely caused by alterations of the intercellular contacts and not by apoptosis or increased size/number of nanopores of intestinal epithelial cells in this murine model of early sepsis.

Inhibition of platelet activation suppresses reactive enteric glia and mitigates intestinal barrier dysfunction during sepsis

“…Disruption of intestinal epithelial tight junctions may cause hyperpermeability which can be observed in both septic animals (Dominguez et al 2013) and patients (Klaus et al 2013). In the early stage of sepsis, the intercellular spaces among intestinal epithelial cells were expanded and the expression of tight junction proteins such as claudin-2, claudin-4, occludin and ZO-1 were decreased (Obermuller et al 2020;Otani et al 2020). Then, the apoptosis and damage of intestinal epithelial cells induced intestinal barrier dysfunction, which progressed rapidly to severe sepsis (Hu et al 2019).…”

Toll-like receptor 4-mediated endoplasmic reticulum stress induces intestinal paneth cell damage in mice following CLP-induced sepsis

“…During early sepsis, cell-wall components from bacteria activated TLR4 resulting in a “cytokine storm” of pro-inflammatory mediators generated, mainly via the mitogen-activated protein kinase and NF-κB pathways 22 . Subsequently, alterations of the intercellular contacts (adherens junction and tight junction) caused intestinal hyperpermeability 23 . Meanwhile, TLR4 is significantly higher in crypts and lower on surface epithelium, which is positively correlated with the high expression of IL-6 in the lamina propria 24 .…”

Sepsis induces variation of intestinal barrier function in different phase through nuclear factor kappa B signaling

“…The disruption of intestinal barrier function in early stage is widely studied [ 26 - 28 ], while little attention is paid to the late sepsis. The CLP model of sepsis has previously been described to have at least two phases based on the adrenomeullin or blood glucose level and defined the first phase of sepsis occurred within 6 h, while the second phase was present at 18 h [ 29 - 31 ].…”