Toll-Like Receptor 2 Mediates Ischemia-Reperfusion Injury of the Small Intestine in Adult Mice

Abstract

Toll-like receptor 2 (TLR2) recognizes conserved molecular patterns associated with both gram-negative and gram-positive bacteria, and detects some endogenous ligands. Previous studies demonstrated that in ischemia-reperfusion (I/R) injury of the small intestine, the TLR2-dependent signaling exerted preventive effects on the damage in young mice, but did not have a significant effect in neonatal mice. We investigated the role of TLR2 in adult ischemia-reperfusion injury in the small intestine. Wild-type and TLR2 knockout mice at 16 weeks of age were subjected to intestinal I/R injury. Some wild-type mice received anti-Ly-6G antibodies to deplete circulating neutrophils. In wild-type mice, I/R induced severe small intestinal injury characterized by infiltration by inflammatory cells, disruption of the mucosal epithelium, and mucosal bleeding. Compared to wild-type mice, TLR2 knockout mice exhibited less severe mucosal injury induced by I/R, with a 35%, 33%, and 43% reduction in histological grading score and luminal concentration of hemoglobin, and the numbers of apoptotic epithelial cells, respectively. The I/R increased the activity of myeloperoxidase (MPO), a marker of neutrophil infiltration, and the levels of mRNA expression of tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and cyclooxygenase-2 (COX-2) in the small intestine of the wild-type mice by 3.3-, 3.2-, and 13.0-fold, respectively. TLR2 deficiency significantly inhibited the I/R-induced increase in MPO activity and the expression of mRNAs for TNF-α and ICAM-1, but did not affect the expression of COX-2 mRNA. I/R also enhanced TLR2 mRNA expression by 2.9-fold. TLR2 proteins were found to be expressed in the epithelial cells, inflammatory cells, and endothelial cells. Neutrophil depletion prevented intestinal I/R injury in wild-type mice. These findings suggest that TLR2 may mediate I/R injury of the small intestine in adult mice via induction of inflammatory mediators such as TNF-α and ICAM-1.

TLR2 Modulates Antibodies Required for Intestinal Ischemia/Reperfusion-Induced Damage and Inflammation

“…Using a 45 min ischemic period followed by 60 min reperfusion, a recent study also demonstrated that the neutrophilic infitration, Cox-2 and TNF mediated at least a portion of IR-induced intestinal damage in a TLR2 dependent manner (26). These studies differ from those performed on young (4 wk) mice in which wildtype mice sustained minimal intestinal injury (0.67 injury score on a 0–4 scale) and TLR2 −/− mice exhibited increased injury (39).…”

“…Similarly, TLR2 plays a role in renal, cerebral, and myocardial IR (18, 24, 25). A recent publication indicated that TLR2 is required for the cellular response to intestinal IR (26). However, the role of TLR2 in antibody deposition and complement activation remains unclear.…”

La influencia de la administración de solución de lactato de Ringer o HES 130 / 0,4 en la integridad de la mucosa del intestino delgado en un modelo porcino de hemorragia controlada = The influence of administering Ringer's Lactate solution or HES 130/0.4 on the integrity of the small intestinal mucosa in a pig model of controlled haemorrhage

“…However some studies on neutrophils' role in the local small intestine damage following intestinal IR report contradictory findings (Kurtel et al 1991;Simpson et al 1993;Matthijsen et al 2009), and its role in intestinal IR is still unclear. In a recent study, depletion of circulating neutrophil attenuated the IR injury in the small intestine in wild-type mice (Watanabe et al 2014). In our study, and although not statistically significant, the number of neutrophils present within the lamina propria at the level of the top of the villi, in the duodenum, was higher in groups 1 and 2 than in the control group (group 3).…”

Murine Model of Intestinal Ischemia-reperfusion Injury

“…Although typical time for evaluation of tissue damage after reperfusion is 2-3 hr, longer time (12 hr) is required for the analysis of intestinal stem cell mobilization 36 . Additionally, changes in commensal microbiota and TLR/Nod-mediated signaling can significantly influence the outcome of the of IR injury 4,8,[37][38][39] .…”