Increased Soluble Protein Oligomer in Sepsis is Associated with the Induction of Pro‐inflammatory Signal Transduction in Intra‐renal Arteries

Abstract

IntroductionSepsis is a profoundly morbid and life‐threatening condition affecting every organ in the body. Acute kidney injury (AKI) is a frequent and serious complication of sepsis, and accounts for greater than 50% of cases in the critically ill. Sepsis‐associated AKI is known to develop even in the absence of hemodynamic alterations suggesting contributions from unique inflammatory and immune mechanisms. There has been growing interest in the role of prefibrillar, soluble protein oligomers (SPO) as being primarily responsible for the observed toxicity in a number of age‐related degenerative diseases. SPOs have been shown to activate a variety of pattern recognition receptors (PRRs) leading to pro‐inflammatory signal transduction in these conditions. Endoplasmic reticulum stress in the septic response has been shown activate the unfolded protein response and induce apoptosis. Based on these observations, we hypothesize that the cellular insult in sepsis is sufficiently severe to overwhelm proteostasis mechanisms and lead to the accumulation of SPO in multiple systems, and that SPOs represent damage‐associated molecular patterns (DAMPs) which contribute to the inflammatory state and loss of cellular and tissue integrity observed in sepsis.MethodsMale C57BL/6 mice (age 3–5 months) underwent cecal ligation and puncture (CLP) as a model of sepsis, and sham surgery as a control. Dot blots were performed using A11 anti‐oligomer antibody and secondary donkey anti‐rabbit peroxidase‐linked antibody. For toxicity studies, soluble oligomer was prepared by dissolving amyloid‐β1–42 peptide in hexaflouro‐2‐propanol (HFIP) that was allowed to evaporate before being diluted in cold phenol‐free F12 medium as previously described. Oligomer formation was confirmed by dot blot. Mouse heart and intra‐renal arteries were then incubated in 10‐μM SPO solution for 4 hours, and western blot was performed for p‐ERK and COX‐1 expression.ResultsSoluble oligomer is increased in the heart and intrarenal arteries of CLP mice (1.8 and 1.4 fold vs. control respectively, p < 0.05). (Figure 1) Exposure of intrarenal arteries to 10‐μM soluble oligomer is associated with increased expression of pro‐inflammatory p‐ERK (2.1 fold vs control, p<0.05, Figure 2) and a tendency towards increased COX‐1 expression (p>0.05).ConclusionSepsis is associated with increased soluble protein oligomer in the heart and intra‐renal arteries. Exposure of intra‐renal arteries to SPO is associated with the increased expression of the pro‐inflammatory signaling pathway p‐ERK. These findings support the notion that elevated SPO in sepsis is involved in propagating the inflammatory cascade. The presence of soluble oligomer in the renal vasculature in sepsis and its induction of inflammatory mediators offers a compelling novel mechanism for sepsis‐associated AKI with or without extra‐renal hemodynamic compromise with the potential for specific and novel therapeutic interventions.Support or Funding InformationNIH: P01HL134604, NIH: 1K99GM118885‐01This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.