Complement inhibition attenuates acute kidney injury after ischemia-reperfusion and limits progression to renal fibrosis in mice.

The complement system is an essential component of innate immunity and plays a major role in the pathogenesis of ischemia-reperfusion injury (IRI). In this study, we investigated the impact of human C1-inhibitor (C1INH) on the early inflammatory response to IRI and the subsequent progression to fibrosis in mice. We evaluated structural damage, renal function, acute inflammatory response, progression to fibrosis and overall survival at 90-days post-injury. Animals receiving C1INH prior to reperfusion had a significant improvement in survival rate along with superior renal function when compared to vehicle (PBS) treated counterparts. Pre-treatment with C1INH also prevented acute IL-6, CXCL1 and MCP-1 up-regulation, C5a release, C3b deposition and infiltration by neutrophils and macrophages into renal tissue. This anti-inflammatory effect correlated with a significant reduction in the expression of markers of fibrosis alpha smooth muscle actin, desmin and picrosirius red at 30 and 90 days post-IRI and reduced renal levels of TGF-ß1 when compared to untreated controls. Our findings indicate that intravenous delivery of C1INH prior to ischemic injury protects kidneys from inflammatory injury and subsequent progression to fibrosis. We conclude that early complement blockade in the context of IRI constitutes an effective strategy in the prevention of fibrosis after ischemic acute kidney injury.

Inhibition of complement improves graft outcome in a pig model of kidney autotransplantation.

BACKGROUND: Ischemia reperfusion injury (IRI) induced immune response is a critical issue in transplantation. Complement and contact system activation are among its key mechanisms. STUDY DESIGN: We investigated the benefits of pre-reperfusion treatment with recombinant human C1INH (rhC1INH), inhibitor of both complement and contact activation, in a pig model of kidney autotransplantation, subjecting the organ to 60 min warm ischemia prior to 24 h static preservation to maximize damage. RESULTS: Serum creatinine measurement showed that treated animals recovered glomerular function quicker than the Vehicle group. However, no difference was observed in tubular function recovery, and elevated level of urinary NGal (Neutrophil gelatinase-associated lipocalin) and plasma AST (Aspartate Aminotransferase) were detected, indicating that treatment did not influence IRI-mediated tubular cell necrosis. Regarding chronic graft outcome, rhC1INH significantly prevented fibrosis development and improved function. Immunohistochemistry and western blot showed decreased invasion by macrophages and T lymphocytes, and reduction of epithelial to mesenchymal transition. We determined the effect of treatment on complement activation with immunofluorescence analyses at 30 min post reperfusion, showing an inhibition of C4d deposition and MBL staining in treated animals. CONCLUSIONS: In this model, the inhibition of complement activation by rhC1INH at reperfusion, while not completely counteracting IRI, limited immune system activation, significantly improving graft outcome on the short and long term.

Population pharmacokinetics of recombinant human C1 inhibitor in patients with hereditary angioedema.

AIMS: To characterize the pharmacokinetics (PK) of recombinant human C1 inhibitor (rhC1INH) in healthy volunteers and hereditary angioedema (HAE) patients. METHODS: Plasma levels of C1INH following 294 administrations of rhC1INH in 133 subjects were fitted using nonlinear mixed-effects modelling. The model was used to simulate maximal C1INH levels for the proposed dosing scheme. RESULTS: A one-compartment model with Michaelis-Menten elimination kinetics described the data. Baseline C1INH levels were 0.901 [95% confidence interval (CI): 0.839-0.968] and 0.176 U ml(-1) (95% CI: 0.154-0.200) in healthy volunteers and HAE patients, respectively. The volume of distribution of rhC1INH was 2.86 l (95% CI: 2.68-3.03). The maximal rate of elimination and the concentration corresponding to half this maximal rate were 1.63 U ml(-1) h(-1) (95% CI: 1.41-1.88) and 1.60 U ml(-1) (95% CI: 1.14-2.24), respectively, for healthy volunteers and symptomatic HAE patients. The maximal elimination rate was 36% lower in asymptomatic HAE patients. Peak C1INH levels did not change upon repeated administration of rhC1INH. Bodyweight was found to be an important predictor of the volume of distribution. Simulations of the proposed dosing scheme predicted peak C1INH concentrations above the lower level of the normal range (0.7 U ml(-1)) for at least 94% of all patients. CONCLUSIONS: The population PK model for C1INH supports a dosing scheme on a 50 U kg(-1) basis up to 84 kg, with a fixed dose of 4200 U above 84 kg. The PK of rhC1INH following repeat administration are consistent with the PK following the first administration.

Recombinant C1-inhibitor: effects on coagulation and fibrinolysis in patients with hereditary angioedema.

BACKGROUND: Recombinant human C1-inhibitor (rhC1INH; Ruconest®) has been developed for treatment of acute angioedema attacks in patients with hereditary angioedema (HAE) due to heterozygous deficiency of C1INH. Previous reports suggest that administration of plasma-derived C1INH products may be associated with an increased risk for thromboembolic complications. OBJECTIVES: Our aim is to evaluate the effects of rhC1INH on coagulation and fibrinolysis in symptomatic HAE patients. METHODS: Levels of various coagulation and fibrinolytic parameters were determined in pre- and post-exposure plasma samples from HAE patients included in a randomized clinical trial. Patients were treated with either saline, or 50 or 100 U/kg rhC1INH for an acute angioedema attack. RESULTS: Prior to rhC1INH treatment, the majority of patients had low to normal activated partial thromboplastin times (aPTT) and increased levels of prothrombin fragment 1+2, thrombin-antithrombin complexes, D-dimers and plasmin-antiplasmin complexes, all of which indicate activation of both coagulation and fibrinolysis. Infusion of rhC1INH at doses up to 100 U/kg did not affect these parameters except for a dose-dependent prolongation of aPTT, confirming that rhC1INH is an inhibitor of the contact system, and that F1+2 levels decreased. CONCLUSION: Coagulation and fibrinolytic systems are activated in HAE patients suffering from an acute angioedema attack. Treatment with rhC1INH at 50 or 100 U/kg had no effect on parameters reflecting activation of these systems except for a significant effect on aPTT, which likely reflects a pharmacodynamic effect of rhC1INH, and a reduction on plasma levels of the prothrombin activation fragment F1+2. We conclude that these results argue against a prothrombotic effect of treatment with this rhC1INH product in HAE patients.

Receptors, mediators, and mechanisms involved in bacterial sepsis and septic shock.

Bacterial sepsis and septic shock result from the overproduction of inflammatory mediators as a consequence of the interaction of the immune system with bacteria and bacterial wall constituents in the body. Bacterial cell wall constituents such as lipopolysaccharide, peptidoglycans, and lipoteichoic acid are particularly responsible for the deleterious effects of bacteria. These constituents interact in the body with a large number of proteins and receptors, and this interaction determines the eventual inflammatory effect of the compounds. Within the circulation bacterial constituents interact with proteins such as plasma lipoproteins and lipopolysaccharide binding protein. The interaction of the bacterial constituents with receptors on the surface of mononuclear cells is mainly responsible for the induction of proinflammatory mediators by the bacterial constituents. The role of individual receptors such as the toll-like receptors and CD14 in the induction of proinflammatory cytokines and adhesion molecules is discussed in detail. In addition, the roles of a number of other receptors that bind bacterial compounds such as scavenger receptors and their modulating role in inflammation are described. Finally, the therapies for the treatment of bacterial sepsis and septic shock are discussed in relation to the action of the aforementioned receptors and proteins.

Leukocyte ABCA1 controls susceptibility to atherosclerosis and macrophage recruitment into tissues.

The ATP-binding cassette transporter 1 (ABCA1) has recently been identified as a key regulator of high-density lipoprotein (HDL) metabolism, which is defective in familial HDL-deficiency syndromes such as Tangier disease. ABCA1 functions as a facilitator of cellular cholesterol and phospholipid efflux, and its expression is induced during cholesterol uptake in macrophages. To assess the role of macrophage ABCA1 in atherosclerosis, we generated low-density lipoprotein (LDL) receptor knockout (LDLr(-/-)) mice that are selectively deficient in leukocyte ABCA1 (ABCA1(-/-)) by using bone marrow transfer (ABCA1(-/-) --> LDLr(-/-)). Here we demonstrate that ABCA1(-/-) --> LDLr(-/-) chimeras develop significantly larger and more advanced atherosclerotic lesions compared with chimeric LDLr(-/-) mice with functional ABCA1 in hematopoietic cells. Targeted disruption of leukocyte ABCA1 function did not affect plasma HDL cholesterol levels. The amount of macrophages in liver and spleen and peripheral blood leukocyte counts is increased in the ABCA1(-/-) --> LDLr(-/-) chimeras. Our results provide evidence that leukocyte ABCA1 plays a critical role in the protection against atherosclerosis, and we identify ABCA1 as a leukocyte factor that controls the recruitment of inflammatory cells.