Tissue Damage, Not Infection, Triggers Hepatic Unfolded Protein Response in an Experimental Rat Peritonitis Model

Abstract

BackgroundAbdominal surgery is an efficient treatment of intra-abdominal sepsis. Surgical trauma and peritoneal infection lead to the activation of multiple pathological pathways. The liver is particularly susceptible to injury under septic conditions. Liver function is impaired when pathological conditions induce endoplasmic reticulum (ER) stress. ER stress triggers the unfolded protein response (UPR), aiming at restoring ER homeostasis, or inducing cell death. In order to translate basic knowledge on ER function into the clinical setting, we aimed at dissecting the effect of surgery and peritoneal infection on the progression of ER stress/UPR and inflammatory markers in the liver in a clinically relevant experimental animal model.MethodsWistar rats underwent laparotomy followed by colon ascendens stent peritonitis (CASP) or surgery (sham) only. Liver damage (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and De Ritis values), inflammatory and UPR markers were assessed in livers at 24, 48, 72, and 96 h postsurgery. Levels of inflammatory (IL-6, TNF-α, iNOS, and HO-1), UPR (XBP1, GRP78, CHOP), and apoptosis (BAX/Bcl-XL) mRNA were determined by qPCR. Splicing of XBP1 (XBP1s) was analyzed by gel electrophoresis, p-eIF2α and GRP78 protein levels using the western blots.ResultsAspartate aminotransferase levels were elevated 24 h after surgery and thereafter declined with different kinetics in sham and CASP groups. Compared with sham De Ritis ratios were significantly higher in the CASP group, at 48 and 96 h. CASP induced an inflammatory response after 48 h, evidenced by elevated levels of IL-6, TNF-α, iNOS, and HO-1. In contrast, UPR markers XBP1s, p-eIF2α, GRP78, XBP1, and CHOP did not increase in response to infection but paralleled the kinetics of AST and De Ritis ratios. We found that inflammatory markers were predominantly associated with CASP, while UPR markers were associated with surgery. However, in the CASP group, we found a stronger correlation between XBP1s, XBP1 and GRP78 with damage markers, suggesting a synergistic influence of inflammation on UPR in our model.ConclusionOur results indicate that independent mechanisms induce ER stress/UPR and the inflammatory response in the liver. While peritoneal infection predominantly triggers inflammatory responses, the conditions associated with organ damage are predominant triggers of the hepatic UPR.

Association between volume of lung damage and endoplasmic reticulum stress expression among severe COVID-19 ICU patients

“…However, it is also often presumed in animal models that in ammation triggers ERS response (and vice versa). Our ndings are in concordance with the recent animal study by Müllebner et al showing that peritoneal infection induced by CLP predominantly triggered in ammatory response, while damages caused by surgery were predominant triggers of the ERS/UPR response (20). They hypothesized that ERS/UPR and in ammatory response in vivo during sepsis may be triggered by different mechanisms and that secondary tissue injury in uences the severity of ERS more than the intensity of local and systemic in ammation.…”

“…However, a recent study questioned the causal relationship between in ammation, organ injury and ERS during sepsis. Thus, in a model of surgical peritoneal sepsis (cecal ligation-puncture (CLP)), peritoneal infection predominantly triggered in ammatory responses, while damages induced by surgical stress were predominant triggers of the ERS/UPR response (20). These data, showing that in ammation was little associated with tissue trauma (but driven by infection) while ERS/UPR were essentially driven by tissue trauma more than by infection or systemic in ammation, raise the question of the relationship between ERS, in ammation and volume of organ damage (cellular necrosis / tissue degradation).…”

Endoplasmic Reticulum Stress Induces Vasodilation in Liver Vessels That Is Not Mediated by Unfolded Protein Response

“…Each PCR reaction contained SYBR R green I ® (0.5×, Sigma Aldrich, Vienna, Austria), iTaq TM DNA polymerase TM (25 U/L; Bio Rad, Hercules, CA, USA), oligonucleotide primers (250 nmol/L each, Invitrogen; Carlsbad, CA, USA), dNTP (200 µmol/L each), and MgCl 2 (3 mmol/L). Primer pairs for XBP1 were described elsewhere [25]. Randomly assigned no-reverse transcriptase controls corresponding to ~15% of all the samples investigated, a no-template control, and an internal standard, a pool generated of equal aliquots of cDNA of all samples investigated, were included in each measurement.…”

Association between volume of lung damage and endoplasmic reticulum stress expression among severe COVID-19 ICU patients

“…Récemment, une étude a interrogé la relation de causalité entre inflammation, lésions d'organe et SRE durant le sepsis. En effet, l'infection péritonéale engendrait la réponse inflammatoire alors que les dommages tissulaires induits par le stress chirurgical déclenchaient le SRE / UPR au sein d'un modèle murin de sepsis péritonéal chirurgical (27). Ces données, montrant que l'inflammation induite par l'infection était peu associée au tissu lésé, alors que le SRE/UPR était essentiellement induit par le traumatisme tissulaire plus que par l'infection ou l'inflammation systémique, posent la question de la relation entre le SRE, l'inflammation et le volume de tissu lésé.…”

“…However, a recent study questioned the causal relationship between inflammation, organ injury and ERS during sepsis. Thus, in a model of surgical peritoneal sepsis [cecal ligation-puncture (CLP)], peritoneal infection predominantly triggered inflammatory responses, while damages induced by surgical stress were predominant triggers of the ERS/UPR response ( 20 ). These data, showing that inflammation was little associated with tissue trauma (but driven by infection) while ERS/UPR were essentially driven by tissue trauma more than by infection or systemic inflammation, raise the question of the relationship between ERS, inflammation and volume of organ damage (cellular necrosis/tissue degradation).…”