Intravenous Polyethylene Glycol Alleviates Intestinal Ischemia-Reperfusion Injury in a Rodent Model

Abstract

Intestinal ischemia-reperfusion injury (IRI) is a common clinical entity, and its outcome is unpredictable due to the triad of inflammation, increased permeability and bacterial translocation. Polyethylene glycol (PEG) is a polyether compound that is extensively used in pharmacology as an excipient in various products. More recently, this class of products have shown to have potent anti-inflammatory, anti-apoptotic, immunosuppressive and cell-membrane-stabilizing properties. However, its effects on the outcome after intestinal IRI have not yet been investigated. We hypothesized that PEG administration would reduce the effects of intestinal IRI in rodents. In a previously described rat model of severe IRI (45 min of ischemia followed by 60 min of reperfusion), we evaluated the effect of IV PEG administration at different doses (50 and 100 mg/kg) before and after the onset of ischemia. In comparison to control animals, PEG administration stabilized the endothelial glycocalyx, leading to reduced reperfusion edema, bacterial translocation and inflammatory reaction as well as improved 7-day survival. These effects were seen both in a pretreatment and in a treatment setting. The fact that this product is readily available and safe should encourage further clinical investigations in settings of intestinal IRI, organ preservation and transplantation.

Keywords: intestinal ischemia; intestinal ischemia-reperfusion injury; polyethylene glycol.

Figure 1

Histopathological effect of PEG pretreatment in intestinal IRI was scored according to the Park–Chiu score (A) and villus length (B). Intestinal epithelial permeability was measured by TEER in an Ussing chamber, which was corrected for villus length (C). Bacterial translocation was evaluated by plasmatic endotoxin levels (D). (n = 6/group). Statistical analyses were performed by Kruskal–Wallis testing. IRI: ischemia-reperfusion injury; PEG: polyethylene glycol; TEER: transepithelial electrical resistance. ** p < 0.01; *** p < 0.001.

Figure 2

Inflammatory modulation by PEG administration was measured by systemic IL-6 (A) and intestinal IL-1β (B), TNF-α (C), IL-10 (D) and IFN-γ (E). (n = 6/group). Statistical analyses were performed by one-way ANOVA. IFN-γ: interferon-gamma; IL: interleukin; IRI: ischemia-reperfusion injury; PEG: polyethylene glycol; TNF-α: tumor necrosis factor—alfa. * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 3

Vascular permeability was altered by IV PEG administration, as shown by hemoglobin levels (A), reperfusion edema (wet/dry ratio) (B) and plasmatic endothelial glycocalyx components: syndecan-1 (C) and heparan sulfate (D). (n = 6/group). The protective effect was confirmed by TEM images of terminal ileum vasculature of a PEG100 + IRI rat (E), compared to a saline + IRI rat (F), showing an intact endothelial glycocalyx (arrow E) versus a destructed one (arrow F). Statistical analyses were performed by one-way ANOVA. IRI: ischemia-reperfusion injury; PEG: polyethylene glycol; TEM: transmission electron microscopy. * p < 0.05; ** p < 0.01; *** p < 0.001. Scale bar = 1 µm.

Figure 4

Effect of PEG 100 mg/kg in treatment versus pretreatment and control animals, evaluated on histopathology (A), bacterial translocation (B), inflammatory reaction (intestinal IL-1β (C) and IL-10 (D)), reperfusion edema (E) and endothelial glycocalyx (F). (n = 6 rats/group). Statistical analyses were performed by Kruskal–Wallis (A,B) and one-way ANOVA (C–F). IRI: ischemia-reperfusion injury; PEG: polyethylene glycol. * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 5

Seven-day survival, assessed by Kaplan–Meier analysis (n = 10 rats/group). IRI: ischemia-reperfusion injury; PEG: polyethylene glycol; T: treatment.

Figure 6

Timeline of the experiments, with sampling time points and explanation of the different groups. IRI: ischemia-reperfusion injury; PEG: polyethylene glycol; 50: 50 mg/kg body weight; 100: 100 mg/kg body weight; 100(T): 100 mg/kg body weight in the treatment setting.