The Fibrin Cleavage Product Bβ15-42 Channels Endothelial and Tubular Regeneration in the Post-acute Course During Murine Renal Ischemia Reperfusion Injury.

Dania Fischer,Christopher Seifen,Bertram Scheller,Kai Zacharowski,Thorsten J Maier,Michaela Jung,Christina Mertens,Rainer Hofmann,Patrick Baer,Anja Urbschat

doi:10.3389/fphar.2018.00369

Abstract

Early and adequate restoration of endothelial and tubular renal function is a substantial step during regeneration after ischemia reperfusion (IR) injury, occurring, e.g., in kidney transplantation, renal surgery, and sepsis. While tubular epithelial cell injury has long been of central importance, recent perception includes the renal vascular endothelium. In this regard, the fibrin cleavage product fibrinopeptide Bβ15-42 mitigate IR injury by stabilizing interendothelial junctions through its affinity to VE-cadherin. Therefore, this study focused on the effect of Bβ15-42 on post-acute physiological renal regeneration. For this, adult male C57BL/6 mice were exposed to a 30 min bilateral renal ischemia and reperfusion for 24 h or 48 h. Animals were randomized in a non-operative control group, two operative groups each treated with i.v. administration of either saline or Bβ15-42 (2.4 mg/kg) immediately prior to reperfusion. Endothelial activation and inflammatory response was attenuated in renal tissue homogenates by single application of Bβ15-42. Meanwhile, Bβ15-42 did not affect acute kidney injury markers. Regarding the angiogenetic players VEGF-A, Angiopoietin-1, Angiopoietin-2, however, we observed significant higher expressions at mRNA and trend to higher protein level in Bβ15-42 treated mice, compared to saline treated mice after 48 h of IR, thus pointing toward an increased angiogenetic activity. Similar dynamics were observed for the intermediate filament vimentin, the cytoprotective protein klotho, stathmin and the proliferation cellular nuclear antigen, which were significantly up-regulated at the same points in time. These results suggest a beneficial effect of anatomical contiguously located endothelial cells on tubular regeneration through stabilization of endothelial integrity. Therefore, it seems that Bβ15-42 represents a novel pharmacological approach in the targeted therapy of acute renal failure in everyday clinical practice.

Highlights

Ischemia reperfusion injury (IR) leads to the development of acute kidney injury (AKI) characterized by a massive tubular cell death, mainly affecting proximal tubules within the outer stripe of the outer medulla (Bonventre, 2010)
The corresponding vascular endothelial (VE)-cadherin protein expression significantly increased after 24 h of ischemia reperfusion (IR) but reached again levels of the control group after 48 h of IR, still no marked difference was found between saline and Bβ15−42 treated mice at both points in time (Figure 1B)
IR injury induces the generation of inflammatory mediators like cytokines and chemokines by both tubular and endothelial cells (Supavekin et al, 2003; Bonventre and Zuk, 2004)

Summary

Introduction

Ischemia reperfusion injury (IR) leads to the development of acute kidney injury (AKI) characterized by a massive tubular cell death, mainly affecting proximal tubules within the outer stripe of the outer medulla (Bonventre, 2010). Loosening of interendothelial connections and the subsequent formation of interendothelial gaps with leak formation leads to dysfunction of the blood–tissue barrier (Basile, 2007), possibly influencing recovery of the affected segments These renal alterations rapidly evoke a process of regeneration, leading to restoration of both normal tubular and endothelial architecture. Endothelial injury and capillary loss in the immediate vicinity of damaged renal epithelial tubules seem to affect tubular recovery and are of particular interest In this context, vascular endothelial (VE)-cadherin is one of the most important endothelial anchor proteins which is connected to the actin-based cytoskeleton and one of the key molecules integrating and tightening endothelial cell junctions maintaining the vascular barrier integrity (Dejana et al, 2001; Broman et al, 2007; Vestweber, 2008). In supra-physiologic doses, this peptide has proven its efficacy to prevent VE-cadherin disruption, and micro-vascular dysfunction, achieving an organoprotection in myocardial IR injury in rodents (Petzelbauer et al, 2005), pigs (Roesner et al, 2007) as well as in humans (Atar et al, 2009), and recently in a clinical case of vascular leak syndrome during Ebola virus disease (Wolf et al, 2015)

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