The Protective Role of CD59 and Pathogenic Role of Complement in Hepatic Ischemia and Reperfusion Injury

Abstract

Hepatic ischemia-reperfusion injury (IRI) is a major factor influencing graft outcome in liver transplantation, but its mechanism is not well defined. Although complement, including the membrane attack complex (MAC), a terminal product of complement activation, is thought to be involved in the multiple reactions subsequent to the ischemia-reperfusion (IR) process, the role of MAC in the pathogenesis of hepatic IRI requires further investigation. We used a warm ischemia-reperfusion injury model in mice and a syngeneic orthotopic liver transplantation model in rats to define the role of complement, including MAC, in hepatic IR. CD59-deficient mice had more severe liver dysfunction, evidenced by increased aspartate aminotransferase levels and increased injury of liver parenchymal and nonparenchymal cells than did CD59-sufficient mice during warm hepatic IR. Furthermore, complement depletion in CD59-deficient mice by pretreatment with cobra venom factor (CVF) or the genetic introduction of C3 deficiency partially protected against development of the severe liver dysfunction that occurred in CD59-deficient mice. Severity of liver dysfunction correlated with MAC deposition, apoptotic cells, and increased inflammatory mediators such as tumor necrosis factor ␣. Liver transplantation is a routine and powerful approach for treatment of patients with acute or chronic liver failure of various causes. 1 Nevertheless, hepatic ischemia-reperfusion (IR) remains a major deleterious factor influencing graft outcome in organ transplantation. The incidence of primary graft failure (5% to 15%) and initial poor function (10% to 25%) is strongly dependent on the extent of ischemia-reperfusion injury (IRI). 2-4 IRI also initiates later graft failure by triggering irreversible intrahepatic biliary tract injury (ischemic-type biliary lesion) or by promoting rejection through activation of innate immunity. 5 At present, because of the shortage of organs for transplantation, the donor pool has been expanded by utilization of marginal organs from old donors or non-heart-beating donors, as well as grafts with prolonged cold storage, and even allografts donated after cardiac death. It is conceivable that grafts from such donors could cause severe liver injury, because they have usually experienced a long ischemia time. To improve the outcome of liver transplantation, therefore, it is imperative to better understand the mechanisms involved in IRI and to design novel therapeutic strategies for prevention of IRI.Ischemia-reperfusion injury is characterized by the presence of activated polymorphonuclear leukocytes, oxygen radical formation, 6 and cytokine release. 7,8 The process that temporarily blocks blood supply followed by blood reperfusion to the living donor after the transplantation causes attraction, activation, adhesion, and migration of neutrophils at the site of donor organ, thereby

Complement—here, there and everywhere, but what about the transplanted organ?

“…Transplantation of kidneys from C3-deficient donors resulted in an increased rejection free survival supporting a role for donor-derived C3 in murine transplant rejection [16]. These models illustrate how complement damages the renal parenchyma directly and indirectly by enhancing the recipient's T cell response in a C3 dependent manner [31,47]. A similar phenomenon is reported in cardiac transplants with activation of the classical and alternative pathways via inhibition of the complement regulator CD55 [70][71][72].…”

“…This has been found in studies of complement deficient and depleted mice that are protected against reperfusion damage [30,31,33,34]. C5a acts directly on the C5a receptor on parenchymal cells, as well as stimulating chemotaxis and degranulation of neutrophils [35,36].…”

“…This induces cellular inflammation via toll-like receptors, cytokines, chemokines and complement. Complement activation both initiates and propagates tissue damage not only in kidney transplantation but also in other major transplanted organs such as the heart, lung, liver and pancreas [27][28][29][30][31][32]. The classical pathway is triggered by the C1 complex (C1q, C1r, C1s) binding to antibody or C-reactive protein on the activating surface, leading to the formation of the classical pathway C3 convertase from C4 and C2 (C4bC2a) and to subsequent cleavage of C3.…”

Targeted Complement Inhibition Protects Vascularized Composite Allografts From Acute Graft Injury and Prolongs Graft Survival When Combined With Subtherapeutic Cyclosporine A Therapy

“…This indicates that whereas the anaphylatoxins may contribute to IRI, likely via the recruitment and/or activation of leukocytes, other operative mechanisms that are not affected by C3aR/C5aR deficiency, namely C3 opsonins and/or the MAC, play a prominent role in VCA IRI. Indeed, in some solid organs the MAC appears to be the primary mediator of IRI 31–34 . In addition to being directly cytolytic, deposition of the MAC at sublytic concentrations can, as can the anaphylatoxins, result in the activation of endothelial cells, expression of adhesion molecules, and the recruitment and activation of leukocytes 35,36 .…”

Use of a Hanging-weight System for Liver Ischemia in Mice

“…liver transplantation, hepatic tumor resection or trauma repair and can result in liver failure which has a high mortality rate [1][2] . Therefore murine studies of hepatic ischemia have become an important field of research by providing the opportunity to utilize pharmacological and genetic studies [3][4][5][6][7][8][9] . Specifically, conditional mice with tissue specific deletion of a gene (cre, flox system) provide insights into the role of proteins in particular tissues [10][11][12][13] .…”