Reperfusion injury of ischemic skeletal muscle is mediated by natural antibody and complement.

Abstract

SummaryReperfusion ofischemic tissue induces an acute inflammatory response that can result in necrosis and irreversible cell injury to both local vascular endothelium and parenchyma. To examine the pathogenesis of ischemia/reperfusion injury, we have used mice deficient in complement components C3, C4, or serum immunoglobulin in a hindlimb model of ischemia. We found that mice homozygous deficient in C3 or C4 were equally protected against reperfusion injury based on a significant reduction in leakage of radiolabeled albumin out of the vasculature. This demonstrates that classical pathway complement is an important factor in the initiation ofinflammarion following reperfusion. Furthermore, mice deficient in serum immunoglobulin were equally protected and this protection could be reversed by reconstitution with serum from norreal mice. Thus, this report describes a novel mechanism for reperfusion injury that involves antibody deposition and activation of complement leading to inflammation permeability. While the pathogenesis of reperfnsion injury is not completely understood, the complement system is thought to be involved since there is clear evidence of deposition of complement components C5-9 after repeffusion of hypoxic tissue (1, 2) and injury can be inhibited in part by pretreatment with soluble complement receptor type 1 (sCR1) (3-6). Weisman et al. found that pretreatment with sCR1 substantially reduced influx of neutrophils, deposition of C5-9 and myocardial infarct size in a rat model of myocardial ischemia (3). Similar studies have used sCR1 to block or reduce inflammation after reperfusion ofischemic rat hindlimb or intestine and of mouse skeletal muscle (cremaster) (4-6). Complement receptor type 1 (CR1; CD35), which is normally expressed by human erythrocytes, B lymphocytes, granulocytes, and macrophages, binds activated C3 (C3b) and C4 (C4b) leading both to dissociation of the complement system's C3 and C5 activating enzymes and to proteolytic degradation of C3b and C4b by serum factor I. When administered in a soluble form, recombinant sCR,1 functions as a highly effective inhibitor of serum complement activation (7).To clarify the role of complement and gain insight into the pathogenesis of ischemia/reperfusion injury, we have examined novel strains of mice deficient in either complement components C3 or C4 in a mouse model ofhindlimb ischemia reperfusion. Both strains of mice were equally protected from vascular injury demonstrating that injury is mediated by the classical pathway. Moreover, mice totally deficient in antibody, i.e., recombination-activation gene 2 deficient (RAG-2-/-) (8), were equally protected and protection could be abrogated by reconstitution with fresh mouse serum. These results support the hypothesis that ischemia/reperfusion injury is initiated by natural antibody binding to hypoxic endothelium and activation of the complement system. Materials and MethodsReconstitution of Antibody-d!ficient Mice. RAG2-/-mice were reconstituted by i.v. administration of 0.5 ml of pooled ...

Soft Tissue Repair Capacity after Oxygen-Derived Free Radical-Induced Damage in One Hindlimb of the Rat

“…72, NO. 1, SEPTEM BER 1997 the histological vascular damage as found w ith tertBuOOH infusion are also observed in acute inflam m a tion [37] and in ischemia/reperfusion [38][39][40]. In the model presented in this report, the vascular damage is primarily initiated by free radicals.…”

“…A t this time they also might produce higher amounts of free radicals [41,42] and could have an amplifying role on the degree of tissue damage. An other pathophysiological mechanism which m ight be involved in the increased vascular permeability is the classical complement pathway [38].…”

How dying cells alert the immune system to danger

“…That this process is important to deathinduced inflammation, in at least some settings, is suggested from a number of findings. Immunodeficient mice that lack antibody show reduced inflammation to ischemia-reperfusion injury of the bowel 62 , skeletal muscle 63 and heart 64 . Injection of a monoclonal myosin-heavychain-specific antibody into these animals restores the inflammatory response after injury 65 .…”

Complement C6 Deficiency Protects Against Diet-Induced Atherosclerosis in Rabbits

“…Second, it is possible that E-LDL is initially taken up by monocytes/macrophages but is then released subsequent to cell death, if the cells are unable to leave the vessel wall. Finally, complement activation may additionally be driven by other processes such as reperfusion events [42][43][44][45] or liberation of intracellular complement activators from the cells. 46,47 A major unanswered question relates to the problem of why the terminal complement sequence should assume such a central role in atherogenesis.…”