VSIG4 inhibits RANKL-induced osteoclastogenesis by enhancing Nrf2-dependent antioxidant response against reactive oxygen species production

Osteoporosis is a prevalent systemic skeletal disorder, particularly affecting postmenopausal women, primarily due to excessive production and activation of osteoclasts. However, the current anti-osteoporotic drugs utilized in clinical practice may lead to certain side effects. Therefore, it is necessary to further unravel the potential mechanisms regulating the osteoclast differentiation and to identify novel targets for osteoporosis treatment. This study revealed the most significant decline in VSIG4 expression among the VSIG family members. VSIG4 overexpression significantly inhibited RANKL-induced osteoclastogenesis and bone resorption function. Mechanistically, both western blot and immunofluorescence assay results demonstrated that VSIG4 overexpression attenuated the expression of osteoclast marker genes and dampened the activation of MAPK and NF-κB signaling pathways. Furthermore, VSIG4 overexpression could inhibit the generation of reactive oxygen species (ROS) and stimulate the expression of Nrf2 along with its downstream antioxidant enzymes via interaction with Keap1. Notably, a potent Nrf2 inhibitor, ML385, could reverse the inhibitory effect of VSIG4 on osteoclast differentiation. In line with these findings, VSIG4 overexpression also mitigated bone loss induced by OVX and attenuated the activation of osteoclasts in vivo. In conclusion, our results suggest that VSIG4 holds promise as a novel target for addressing postmenopausal osteoporosis. This is achieved by suppressing osteoclast formation via enhancing Nrf2-dependent antioxidant response against reactive oxygen species production.

Soluble complement receptor 1 protects the peripheral nerve from early axon loss after injury

Complement activation is a crucial early event in Wallerian degeneration. In this study we show that treatment of rats with soluble complement receptor 1 (sCR1), an inhibitor of all complement pathways, blocked both systemic and local complement activation after crush injury of the sciatic nerve. Deposition of membrane attack complex (MAC) in the nerve was inhibited, the nerve was protected from axonal and myelin breakdown at 3 days after injury, and macrophage infiltration and activation was strongly reduced. We show that both classical and alternative complement pathways are activated after acute nerve trauma. Inhibition of the classical pathway by C1 inhibitor (Cetor) diminished, but did not completely block, MAC deposition in the injured nerve, blocked myelin breakdown, inhibited macrophage infiltration, and prevented macrophage activation at 3 days after injury. However, in contrast to sCR1 treatment, early signs of axonal degradation were visible in the nerve, linking MAC deposition to axonal damage. We conclude that sCR1 protects the nerve from early axon loss after injury and propose complement inhibition as a potential therapy for the treatment of diseases in which axon loss is the main cause of disabilities.

Attenuation of myocardial reperfusion injury in pigs by Mirococept, a membrane-targeted complement inhibitor derived from human CR1

OBJECTIVES

Membrane-targeted application of complement inhibitors may ameliorate ischemia/reperfusion (I/R) injury by directly targeting damaged cells. We investigated whether Mirococept, a membrane-targeted, myristoylated peptidyl construct derived from complement receptor 1 (CR1) could attenuate I/R injury following acute myocardial infarction in pigs.

METHODS

In a closed-chest pig model of acute myocardial infarction, Mirococept, the non-tailed derivative APT154, or vehicle was administered intracoronarily into the area at risk 5 min pre-reperfusion. Infarct size, cardiac function and inflammatory status were evaluated.

RESULTS

Mirococept targeted damaged vasculature and myocardium, significantly decreasing infarct size compared to vehicle, whereas APT154 had no effect. Cardioprotection correlated with reduced serum troponin I and was paralleled by attenuated local myocardial complement deposition and tissue factor expression. Myocardial apoptosis (TUNEL-positivity) was also reduced with the use of Mirococept. Local modulation of the pro-inflammatory and pro-coagulant phenotype translated to improved left ventricular end-diastolic pressure, ejection fraction and regional wall motion post-reperfusion.

CONCLUSIONS

Local modification of a pro-inflammatory and pro-coagulant environment after regional I/R injury by site-specific application of a membrane-targeted complement regulatory protein may offer novel possibilities and insights into potential treatment strategies of reperfusion-induced injury.

[Protective effects of recombinant SCR15-18 domain of human soluble complement receptor type 1 on myocardial ischemia and reperfusion injury]

OBJECTIVE

To investigate the protective effects of recombinant SCR15-18 domain of human soluble complement receptor type 1 (sCR1-SCR-15-18) in rats underwent myocardial ischemia and reperfusion (I/R).

METHODS

Sprague-Dawley rats were randomly divided into three groups (n = 12 each group): sham (SO); 30 min ischemia/3h reperfusion (I/R) and I/R plus sCR1-SCR15-18 (15 mg/kg before I/R, sCR1). Serum LDH, CK and cardiac myeloperoxidase (MPO) activity were measured. Infarct size, myocardial histopathological changes and myocardial C3c were also compared among groups.

RESULTS

Infarct size [(16.1 +/- 3.3)% vs. (22.9 +/- 3.0)%, infarct zone/left ventricular mass, P < 0. 05] and CK [(2532.5 +/- 597.1) U/L vs. (3400.9 +/- 534.9) U/L, P < 0. 05] and LDH [(5436.2 +/- 611.3) U/L vs. (6572.0 +/- 476.3) U/L, P < 0. 05] as well as MPO activity in infarct zone [(0.81 +/- 0.14) U/g vs. (1.12 +/- 0.13) U/g, P < 0.05] were significantly decreased post sCR1 compared to I/R group. sCR1 also significantly attenuated histological myocardial injury and reduced the deposition of C3c in infarct zone.

CONCLUSION

sCR1-SCR15-18 protein exerts cardioprotective effects in this rat I/R model.

Beneficial effects of complement inhibition with soluble complement receptor 1 (TP10) during cardiac surgery: is there a gender difference?

BACKGROUND

TP10, a potent inhibitor of complement activation during cardiopulmonary bypass (CPB) has been shown to significantly reduce the incidence of death and myocardial infarction (MI) in high-risk male patients undergoing cardiac surgery. However, the effect of TP10 in females was undefined because of the limited number of females studied. To examine the possibility of a gender effect, this phase 2 multi-center trial was undertaken to determine whether TP10 would also limit ischemic damage in a larger sample size of high-risk females undergoing cardiac surgery on cardiopulmonary bypass (CPB).

METHODS AND RESULTS

This prospective, double-blind, placebo-controlled, multi-center trial involved 297 high-risk (urgent surgery, CABG + Valve, reoperations, ejection fraction <30%) female patients randomized to receive a 5 mg/kg dose of TP10 (n=150) or placebo (n=147) as a 30-minute intravenous infusion before surgery. The primary end point was the incidence of death or MI at 28 days after surgery. Complement activation was assessed by levels of CH50 and SC5b-9 during and after CPB. TP10 was well tolerated and there were no differences in the safety profiles of the 2 groups. Although TP10 effectively suppressed complement activation (at 2 hours after CPB CH50 (mean+SD % change from baseline) 50+/-17% placebo versus 4+/-14% TP10; P=0.0001; SC5b-9 (ng/mL) 917+/-1067 placebo versus 204+/-79 TP10; P=0.0001), there was no difference in the primary end point between the groups (17% placebo versus 21% TP10; P=0.2550).

CONCLUSIONS

The benefits of TP10 appear to be gender-related. and mechanisms other than complement activation may be responsible for myocardial injury in high-risk female patients during cardiac surgery on CPB.

Mechanisms of disease: the complement system in renal injury--new ways of looking at an old foe

The fact that the complement system is activated during immune-complex glomerular disease has been known for nearly 50 years. Detection of complement deposition in the glomerulus using immunochemistry has become an important element of the histological analysis of renal biopsies, and is key to the diagnosis of many types of glomerulonephritis. In recent years it has become evident that complement activation is involved in the pathogenesis of other types of renal disease; complement activation is implicated in transplant injury, atypical hemolytic uremic syndrome and progressive tubulointerstitial fibrosis. Emergence of this evidence has provided insight into how these diseases develop, and has yielded useful diagnostic tools and potential targets for therapeutic intervention. Clinicians have, by using plasma-based therapies, unknowingly treated abnormalities of the complement system in renal patients for many years. Advances in antibody and protein technologies have led to the development of complement inhibitors that have been used in phase III clinical studies. More-specific agents and applications are likely to be developed over the coming years and are discussed in this Review.

Complement C5 mediates experimental tubulointerstitial fibrosis

Renal fibrosis is the final common pathway of most progressive renal diseases. C5 was recently identified as a risk factor for liver fibrosis. This study investigated the role of C5 in the development of renal tubulointerstitial fibrosis by (1) induction of renal fibrosis in wild-type and C5(-/-) mice by unilateral ureteral ligation (UUO) and (2) investigation of the effects of a C5a receptor antagonist (C5aRA) in UUO. In C5(-/-) mice, when compared with wild-type controls, markers of renal fibrosis (Sirius Red, type I collagen, fibronectin, alpha-smooth muscle actin, vimentin, and infiltrating macrophages) were significantly reduced on day 5 of UUO. On day 10, fibronectin mRNA and protein expression were still reduced in the C5(-/-) mice. Cortical mRNA of all PDGF isoforms and of TGF-beta(1) (i.e., central mediators of renal disease) were significantly reduced in C5(-/-) mice when compared with controls. Renal tubular cell expression of the C5aR was sparse in normal cortex but markedly upregulated after UUO. Treatment of wild-type UUO mice with C5aRA also led to a significant reduction of cortical Sirius Red staining, fibronectin protein expression, and PDGF-B mRNA expression on day 5. Neither genetic C5 deficiency nor C5aRA treatment caused any histologic changes in the nonobstructed kidneys. In cultured murine cortical tubular cells, C5a stimulated production of TGF-beta(1), and this was inhibited by C5aRA. Using a combined genetic and pharmacologic approach, C5, in particular C5a, is identified as a novel profibrotic factor in renal disease and as a potential new therapeutic target.

The use of TP10, soluble complement receptor 1, in cardiopulmonary bypass

Cardiopulmonary bypass (CPB) for cardiac surgery or lung transplantation initiates a systemic inflammatory response characterized by increased vascular permeability, generalized edema, abnormal lung function and oxygenation and impaired ventricular function. This post-CPB syndrome significantly contributes to postoperative morbidity and mortality. Activation of complement during CPB is a key component that initiates and augments this process. TP10, soluble complement receptor 1, is a novel complement inhibitor that is a potent inhibitor of C3 and C5 convertases, blocking activation of the complement cascade at the nexus of all three complement pathways. Recent controlled trials in humans have demonstrated that TP10 effectively inhibits complement activation during CPB. In high-risk adult patients, TP10 decreases the incidence of mortality and myocardial infarction in males but not in females following cardiac surgery. TP10 is also well tolerated and protects vascular function in infants undergoing CPB. In addition, TP10 leads to early extubation in adult lung transplant recipients. TP10 is currently positioned for clinical development in a male-only indication of cardiac surgery on CPB.

Soluble human complement receptor 1 limits ischemic damage in cardiac surgery patients at high risk requiring cardiopulmonary bypass

BACKGROUND

This study was undertaken to determine whether soluble human complement receptor type 1 (TP10), a potent inhibitor of complement activation, would reduce morbidity and mortality in high-risk patients undergoing cardiac surgery on cardiopulmonary bypass (CPB).

METHODS

This was a randomized multicenter, prospective, placebo-controlled, double-blind study in which 564 high-risk patients undergoing cardiac surgery on CPB received an intravenous bolus of TP10 (1, 3, 5, 10 mg/kg) or placebo immediately before CPB. The primary endpoint was the composite events of death, myocardial infarction (MI), prolonged (> or =24 hours) intra-aortic balloon pump support (IABP), and prolonged intubation.

RESULTS

TP10 significantly inhibited complement activity after 10 to 15 minutes of CPB and this inhibition persisted for 3 days postoperatively. However, there was no difference in the primary endpoint between the 2 groups (33.7% placebo versus 31.4% TP10; P=0.31). The primary composite endpoint was, however, reduced in all male TP10 patients by 30% (P=0.025). TP10 reduced the incidence of death or MI in males by 36% (P=0.026), the incidence of death or MI in CABG males by 43% (P=0.043) and the need for prolonged IABP support in male CABG and valve patients by 100% (P=0.019). There was, however, no improvement seen in female TP10 patients. There were no significant differences in adverse events between the groups.

CONCLUSIONS

TP10 effectively inhibits complement activation during CPB; however, this was not associated with an improvement in the primary endpoint of the study. Nevertheless, TP10 did significantly decrease the incidence of mortality and MI in male patients.

Effects of recombinant sCR1 on the immune inflammatory reaction in acute spinal cord injury tissue of rats

OBJECTIVE

To determine the effects of recombinant soluble complement receptor type I (sCR1) on the immune inflammatory reaction in acute spinal cord injury tissue of rats and its protective effects.

METHODS

SD rat models of acute spinal cord injury were prepared by modified Allen's method. The motor function of the rat lower extremities in sCR1 group and normal saline (NS) group was evaluated by the tiltboard experiment at 12 h, 1 d, 3 d, 7 d, and 14 d. The neutrophil infiltration and C3c positive expression were observed. The myeloperoxidase activity was assessed in the injury tissue at 12 h, 1 d, 3 d, 7 d, and 14 d after injury in the two groups.

RESULTS

The motor function of rat in sCR1 group at 3 d, 7 d, and 14 d was obviously better than that in NS group (P<0.01, P<0.01, P<0.01). C3c positive expression in sCR1 group at each time point after injury was obviously less than that in NS group (P<0.01). The myeloperoxidase activity in sCR1 group at each time point after injury was obviously less than that in NS group (P<0.01).

CONCLUSIONS

Recombinant soluble complement receptor type I (sCR1) can lessen the immune inflammatory reaction in acute spinal cord injury tissue and relieve secondary spinal cord injury by inhibiting the activation of the complement system.

Comparative anti-inflammatory activities of antagonists to C3a and C5a receptors in a rat model of intestinal ischaemia/reperfusion injury

1. Complement activation is implicated in the pathogenesis of intestinal ischaemia-reperfusion injury (I/R), although the relative importance of individual complement components is unclear. A C3a receptor antagonist N(2)-[(2,2-diphenylethoxy)acetyl]-l-arginine (C3aRA) has been compared with a C5a receptor antagonist (C5aRA), AcF-[OPdChaWR], in a rat model of intestinal I/R. 2. C3aRA (IC(50)=0.15 microm) and C5aRA (IC(50)=0.32 microm) bound selectively to human polymorphonuclear leukocyte (PMN) C3a and C5a receptors, respectively. Effects on circulating neutrophils and blood pressure in the rat were also assessed. 3. Anaesthetised rats, subjected to intestinal ischaemia (30 min) and reperfusion (120 min), were administered intravenously with either (A) the C3aRA (0.1-1.0 mg x kg(-1)); the C5aRA (1.0 mg x kg(-1)); the C3aRA+C5aRA (each 1.0 mg x kg(-1)); or vehicle, 45 min prior, or (B) the C3aRA (1.0 mg x kg(-1)) or vehicle, 120 min prior to reperfusion. 4. The C3aRA and C5aRA, administered 45 min prior to reperfusion, displayed similar efficacies at ameliorating several disease markers (increased oedema, elevated ALT levels and mucosal damage) of rat intestinal I/R. The combination drug treatment did not result in greater injury reduction than either antagonist alone. However, doses of the C3aRA (0.01-10 mg x kg(-1)) caused transient neutropaenia, and the highest dose (10 mg x kg(-1)) also caused a rapid and transient hypertension. 5. The C3aRA (1.0 mg x kg(-1)), delivered 120 min prior to reperfusion to remove the global effect of C3aRA-induced neutrophil sequestration, did not attenuate the markers of intestinal I/R, despite persistent C3aR antagonism at this time. 6. C3aR antagonism does not appear to be responsible for the anti-inflammatory actions of this C3aRA in intestinal I/R in the rat. Instead, C3aRA-mediated global neutrophil tissue sequestration during ischaemia and early reperfusion may account for the protective effects observed.

Administration of the soluble complement inhibitor, Crry-Ig, reduces inflammation and aquaporin 4 expression in lupus cerebritis

Changes in brain water and cerebral volume can lead to brain edema that may be one of the underlying causes of death in many neurological diseases. Cerebral water content is regulated by aquaporin 4 (AQ4) present in astrocytic end feet and around blood vessels. In systemic lupus erythematosus (SLE), magnetic resonance imaging (MRI) studies of the brain have demonstrated lesions with the prominent appearance of edema. Activation of complement may play a significant role in the pathogenesis of lupus cerebritis by causing inflammation that can lead to edema. In this study, the well-established MRL/lpr lupus mouse model was used to evaluate the role of complement in lupus cerebritis. IgG and C1q colocalized in perivascular deposits indicating that the blood-brain barrier was compromised. Both RNA and protein expressions of AQ4 were significantly increased in brains of MRL/lpr mice. Chronic administration of the soluble complement inhibitor, Crry-Ig, reduced inflammation as measured by decreased accumulation of IgG. In contrast to control MRL/lpr mice, AQ4 expression in complement inhibited MRL/lpr mice was not changed relative to untreated congenic controls. These results illustrate that complement activation in brains of lupus mice leads to enhanced AQ4 expression and inflammation. It is conceivable that increased AQ4 expression results in cerebral edema and hence complement inhibition may provide a new therapeutic option in inflammatory cerebral disorders such as lupus cerebritis.

Complement receptor 1 inhibitors for prevention of immune-mediated red cell destruction: potential use in transfusion therapy

Activation of complement cascade via the antibody-mediated classical pathway can initiate red blood cell (RBC) destruction, causing transfusion reactions and hemolytic anemia. In the present study, we have assessed the ability of a human recombinant soluble form of complement receptor 1 (sCR1) to inhibit complement-mediated RBC destruction in vitro and in vivo. Using an in vitro alloimmune incompatibility model, sCR1 inhibited complement activation and prevented hemolysis. Following transfusion of human group O RBCs into mice lacking detectable pre-existing antibodies against the transfused RBCs, systemic coadministration of 10 mg/kg sCR1, a dose well tolerated in human subjects for prevention of tissue injury, completely inhibited the in vivo clearance of the transfused RBCs and surface C3 deposition in the first hour after transfusion, correlating with the half-life of sCR1 in the circulation. Treatment with sCR1 increased the survival of transfused human group A RBCs in the circulation of mice with pre-existing anti-A for 2 hours after transfusion by 50%, reduced intravascular hemolysis, and lowered the levels of complement deposition (C3 and C4), but not immunoglobulin G (IgG) or IgM, on the transfused cells by 100-fold. We further identified potential functional domains in CR1 that can act to limit complement-mediated RBC destruction in vitro and in vivo. Collectively, our data highlight a potential use of CR1-based inhibitors for prevention of complement-dependent immune hemolysis.

Use of complement inhibitors in tissue injury

A great deal of information has accumulated implicating the complement system in several human disease processes. Although some of this information is circumstantial, protein inhibitors of the complement system have been developed and applied successfully to experimental disease models in animals. Two inhibitors, soluble complement receptor 1 (sCR1) and anti-C5 monoclonal antibody, are now being investigated in a variety of clinical conditions such as systemic lupus erythematosus and rheumatoid arthritis (RA), diseases for which current therapy has changed little and remains unsatisfactory. Preliminary successes in Phase II clinical trials of RA have provided optimism that complement inhibition might prove useful in these diseases and become part of standard medical therapy.

sCR1sLe(X) reduces lung allograft ischemia-reperfusion injury but does not ameliorate acute rejection

BACKGROUND

Combined inhibition of complement and leukocyte adhesion by sCR1sLe(X) reduces lung allograft dysfunction up to 24 h. In the present study its effect on graft function and acute rejection was evaluated up to 5 days after experimental transplantation.

METHODS

Orthotopic single left lung transplantation was performed in 35 male rats (Brown Norway to Fischer 344) after a total ischemic time of 20 h. Two groups were assessed after 1, 3, and 5 days post-transplant, respectively (n=5 per group and time point): controls vs. recipients which received 10 mg/kg sCR1sLe(X) 15 min prior to reperfusion. In addition, five animals received 10 mg/kg per day sCR1sLe(X) for 5 days. For blood gas analysis of the graft, the contralateral lung was occluded for 5 min to assess graft function. Lung grafts were flushed, and histological grading was performed in blinded fashion according to the International Society for Heart and Lung Transplantation criteria.

RESULTS

Graft PaO(2) in recipients treated with sCR1sLe(X) was superior on day 1 (383+/-118 vs. 56+/-15 mmHg; P<0.0001) and day 3 (446+/-48 vs. 231+/-108 mmHg; P<0.0001). Five days after transplantation, no difference in PaO(2) was found (61+/-28 vs. 83+/-31 mmHg; P=0.59). Repeated treatment with sCR1sLe(X) for 5 days did not improve PaO(2) (64+/-5 mmHg; P=0.65 vs. control; P=0.93 vs. sCR1sLe(X)). At any time point, there was no difference in the degree of rejection between groups.

CONCLUSIONS

In this model sCR1sLe(X) provided marked improvement of graft function up to 3 days, but inhibition of both complement system and selectin dependent leukocyte adhesion failed to protect against acute rejection.

Complement inhibitor, complement receptor 1-related gene/protein y-Ig attenuates intestinal damage after the onset of mesenteric ischemia/reperfusion injury in mice

Complement receptor 1-related gene/protein y (Crry) is a murine membrane protein that regulates the activity of both classical and alternative complement pathways. We used a recombinant soluble form of Crry fused to the hinge, CH2, and CH3 domains of mouse IgG1 (Crry-Ig) to determine whether inhibition of complement activation prevents and/or reverses mesenteric ischemia/reperfusion-induced injury in mice. Mice were subjected to 30 min of ischemia, followed by 2 h of reperfusion. Crry-Ig was administered either 5 min before or 30 min after initiation of the reperfusion phase. Pretreatment with Crry-Ig reduced local intestinal mucosal injury and decreased generation of leukotriene B(4) (LTB(4)). When given 30 min after the beginning of the reperfusion phase, Crry-Ig resulted in a decrease in ischemia/reperfusion-induced intestinal mucosal injury comparable to that occurring when it was given 5 min before initiation of the reperfusion phase. The beneficial effect of Crry-Ig administered 30 min after the initiation of reperfusion coincided with a decrease in PGE(2) generation despite the fact that it did not prevent local infiltration of neutrophils and did not have a significant effect on LTB(4) production. These data suggest that complement inhibition protects animals from reperfusion-induced intestinal damage even if administered as late as 30 min into reperfusion and that the mechanism of protection is independent of neutrophil infiltration or LTB(4) inhibition.

Membrane-targeted complement inhibitors

Undesirable complement activation contributes to the pathology of many human diseases by damaging tissue and promoting inflammation. Because complement-mediated damage is caused by the deposition of complement components on the cell surface, several strategies have been devised to target complement regulator proteins to cell membranes. These strategies have resulted in engineered proteins that have improved potency in vitro and enhanced therapeutic benefit in animal models of disease. One membrane-targeted complement inhibitor has now entered clinical development and this class of second-generation agents may provide effective therapies for the treatment of a variety of disease states.

Complement inhibition does not reduce post-hypoxic-ischemic cerebral injury in 21-day-old rats

Hypoxic-ischemic (HI) cerebral injury frequently follows resuscitation and is a recognized cause of permanent long-term neurologic disability in children. Complement activation has been shown to participate in post-ischemic injury to a variety of tissues and organs. To test the hypothesis that complement activation participates in post-HI cerebral injury in immature rats, 21-day-old rats were subjected to right common carotid artery ligation and 8% O(2). This combination of ischemia and hypoxia resulted in the development of significant neuronal loss, edema, and atrophy in the right cerebral hemisphere. However, intraperitoneal administration of the complement inhibitors soluble complement receptor type 1 or cobra venom factor did not reduce the neuronal loss, edema, or atrophy. Therefore, complement activation did not contribute significantly to the cerebral injury observed in this immature rat model.

Prolongation of discordant renal xenograft survival by depletion of complement. Comparative effects of systemically administered cobra venom factor and soluble complement receptor type 1 in a guinea-pig to rat model

There is an increasing body of evidence to suggest that inhibition of complement activation may be a valuable approach to avert hyperacute rejection. In our study, the guinea-pig to rat discordant kidney xenograft model was adapted for the investigation of renal transplant function and an attempt was made to delay the hyperacute rejection using systemically administered cobra venom factor (CVF) and soluble complement receptor type 1 (sCR1). The saline-treated control recipients experienced a rapid transplant rejection with a xenograft survival averaging 10.5 +/- 2.1 min. Administration of a single 60 U/kg i.v. bolus of CVF significantly prolonged renal graft survival to 20.4 +/- 2.5 h, and by a single bolus of sCR1 (50 mg/kg) a prolongation of graft survival to 18.8 +/- 2.3 h was achieved. The grafts functioned only over periods of 2.5 +/- 0.3 and 2.3 +/- 0.2 h, respectively. No complications of sCR1 were noted. We concluded that complement inhibition by sCR1 may be an important component in the therapeutic approach aiming at the prevention of hyperacute rejection in human organ transplantation.

TP-10 (AVANT Immunotherapeutics)

AVANT Immunotherapeutics is developing TP-10, a recombinant soluble complement receptor type 1 (sCR1), for the potential treatment of reperfusion injury (following surgery, ischemic disease and organ transplantation), organ rejection, acute inflammatory injury to the lungs and autoimmune diseases [348669]. TP-10 has been awarded Orphan Drug status from the FDA for the prevention and reduction of adult respiratory distress syndrome (ARDS) and as a treatment for infants undergoing cardiac surgery [180849], [359588]. A placebo-controlled phase II trial, conducted at approximately 30 sites in the US and involving approximately 600 adult patients undergoing cardiac surgery utilizing cardiopulmonary bypass, was initiated in November 2000. This safety and efficacy study was designed to assess the ability of TP-10 to mitigate the injury to the heart, brain and other organs that occurs when patients are placed on cardiopulmonary bypass circuits, thus potentially improving postoperative outcomes [391437]. In September 2000, the company was planning a double-blind, placebo controlled phase IIb trial in infants undergoing cardiac surgery; AVANT expected to initiated in 30 infants in January 2001 [395086]. The data from this trial will enable the company to further define its clinical endpoints before inititating a pivotal phase III trial in 2001 [382529]. A phase I/II trial of TP-10 involving 15 infants, under 12 months of age, undergoing cardiac surgery for congenital heart defects was initiated by the company in September 1999. The trial will evaluate the ability of TP-10 to mitigate the injury to the heart and other organs when patients are placed on cardiopulmonary bypass circuits [340602]. Enrollment was complete by January 2000 [352458]. Phase I safety trials of TP-10, including studies in adult patients at risk for adult respiratory distress syndrome (ARDS), adult patients with first-time myocardial infarction (heart attack), and pediatric patients undergoing cardiac surgery demonstrated that TP-10 is well tolerated. However, after completion, in December 1997, of a phase IIa trial in nine patients with ARDS, AVANT decided to cease development for this indication. TP-10 was licensed to Novartis AG for use in xeno- and allotransplantation in July 1999. Extensive animal studies have shown TP-10 to have potential in a wide variety of complement-mediated conditions, including organ transplantation, multiple sclerosis, rheumatoid arthritis and lupus [238093]. Early work demonstrated favorable results in animal models of reperfusion injury [180849] and hyperacute xenograft rejection in guinea pig to rat and pig to primate organ transplants [191552]. AVANT has received Notices of Allowance (July 1998) from the USPTO for three separate patent applications covering pharmaceutical compositions of TP-10, methods of purification and methods of certain TP-10 glycoforms for treating diseases or disorders resulting from inappropriate complement activation [291776]. In January 1999, the company was awarded US-05856297 which covers pharmaceutical compositions of TP-10. US-05856300 was also awarded covering compositions and methods of producing the drug [312267].

sCR1sLe ameliorates ischemia/reperfusion injury in experimental lung transplantation

BACKGROUND

The nonspecific immune response with activation of the complement system and polymorphonuclear leukocytes is important for the mediation of reperfusion injury after lung transplantation. In this study, we investigated the combined blockade of the complement system and leukocyte adhesion by a novel drug combining soluble complement receptor type 1 (sCR1, CD35) with the selectin ligand sialyl Lewis X (sLe(X), CD15s) synthesized to sCR1sLe(X). Both sCR1 and sCR1sLe(X) were supplied by AVANT Immunotherapeutics, Inc, Needham, Massachusetts.

METHODS

Orthotopic allogeneic single left lung transplantation was performed in male rats (Brown Norway to Fischer F344; n = 5 in all groups) after a total ischemic time of 20 hours. Recipients received either no specific treatment (control) or administration of sCR1 (10 mg/kg) or sCR1sLe(X) (10 mg/kg) 15 minutes before reperfusion by intracardiac injection. Twenty-four hours after reperfusion, the native contralateral lung was occluded to assess gas exchange of the graft only. In additional animals (5 per group), lung tissue was frozen 24 hours after reperfusion and assessed for myeloperoxidase activity as a measurement of neutrophil migration into the graft and thiobarbituric acid reactive substances to quantify lipid peroxidation.

RESULTS

Graft function as assessed by arterial PO (2) in recipients treated with sCR1sLeX was superior not only to that of controls (383 +/- 53 vs 56 +/- 7 mm Hg, P =. 000095) but also to that of animals treated with sCR1 (243 +/- 45 mm Hg, P =.031). This improvement was confirmed by significant reduction of neutrophil migration (0.33 +/- 0.05 vs control, 1.0 +/- 0.09 DeltaOD/mg/min, P =.0000024) and lipid peroxidation (6.2 +/- 0. 38 vs control, 10.6 +/- 0.54 pmol/g, P =.00021).

CONCLUSIONS

Our data indicate that combined inhibition of complement activation and leukocyte adhesion with sCR1sLe(X) reduces reperfusion injury significantly and that both mechanisms are effectively inhibited in this model.

Soluble complement receptor 1 (CD35) delivered by retrovirally infected syngeneic cells or by naked DNA injection prevents the progression of collagen-induced arthritis

OBJECTIVE

The complement system is important in the development of autoimmune inflammation, including rheumatoid arthritis (RA) and collagen-induced arthritis (CIA). Complement receptor 1 (CR1) is involved in regulation of complement activity. Studies on models of autoimmunity have demonstrated that soluble CR1 (sCR1) is a potent therapeutic agent. The present study was thus undertaken to investigate the feasibility of antiinflammatory gene therapy to prevent CIA by delivery of genes encoding truncated sCR1 (tsCR1) and dimeric tsCR1-Ig.

METHODS

Syngeneic fibroblasts or arthritogenic splenocytes, engineered to express tsCR1 using retrovirus-mediated gene transfer, were injected into DBA/1 recipients that had been immunized with bovine type II collagen (CII). In separate experiments, naked DNA containing tsCR1 and tsCR1-Ig genes was injected intramuscularly into the immunized animals. The clinical development of arthritis was monitored, anti-CII levels measured, and antigenic T cell response studied. Affinity-purified tsCR1-Ig was assayed for its inhibitory effect on the alternative complement pathway in mouse serum.

RESULTS

Treatment of CII-immunized mice with the tsCR1-expressing cells inhibited development of CIA, reduced anti-CII antibody levels, and inhibited T cell response to CII in vitro. Intramuscular injections of DNA encoding the CR1 genes prevented the progression of disease. Furthermore, compared with full-length sCR1, purified tsCR1-Ig was more active in inhibiting the murine alternative complement pathway.

CONCLUSION

Our findings demonstrated that tsCR1 and tsCR1-Ig, when delivered via gene therapy, had a beneficial effect on autoimmune inflammation. These results indicate that targeting the complement system in RA patients may be of clinical importance.

The complement regulators C1 inhibitor and soluble complement receptor 1 attenuate acute lung injury in rabbits

Because activation of the complement system plays a major role in the pathogenesis of acute lung injury, the availability of new specific complement inhibitors represents a promising therapeutic approach. In the present study we investigated pulmonary edema formation and pulmonary artery pressure (PAP) in acute complement-induced lung injury for possible therapeutic impact of the complement regulators C1 inhibitor and soluble complement receptor 1. Eighteen isolated and ventilated rabbit lungs were perfused with pooled normal human serum (NHS, final concentration 35%) in Krebs-Henseleit buffer in a recirculating system. Lung weight gain and PAP were continuously recorded. Complement activation was blocked by the addition of C1 inhibitor (1.0 U/mL, n = 6) or sCR 1 (2.0 microg/mL, n = 6). Lungs that received NHS without inhibitors served as controls (n = 6). This study was performed according to the Helsinki Declaration and approved by the local government. Application of NHS resulted in an increase of PAP within 20 min from 8+/-2 to 42+/-6 mmHg, which was significantly (P < 0.05) decreased by C1-Inh (25+/-5 mmHg) and sCRI (20 +/-3 mmHg). Moreover, pulmonary edema formation after NHS, as assessed by overall weight gain, was reduced by both C1-Inh and sCR1, compared with controls. These findings were paralleled with significantly decreased thromboxane release rates and reduced tissue deposition of C3c and C5b-9. C1 inhibitor and sCR1 attenuate the complement-induced pulmonary capillary leakage and PAP increase, indicating the protective effect of complement inhibition in isolated perfused rabbit lungs.

Blockade of complement inhibits obliterative bronchiolitis in rat tracheal allografts

The role of complement activation in the development of obliterative bronchiolitis, a manifestation of chronic lung allograft rejection, was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft complement components C3 and C5b-9 (membrane attack complex) as well as IgM and IgG deposits were demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. A 7-d treatment with recombinant human soluble complement receptor type 1 (sCR1; 20 mg/kg/d, intraperitoneal), an inhibitor of both the classic and alternative complement pathways, significantly decreased epithelial necrosis and intragraft neutrophil infiltration, and reduced obliterative changes by 40%. Immunohistochemical analysis of the grafts showed that sCR1 treatment significantly decreased early C5b-9 and IgG deposits, neutrophil chemoattractant IL-8 immunoreactivity, and ICAM-1 expression. Treatment with sCR1 was associated with increased staining for Th2 cytokines, in particular IL-10, with concomitant downregulation of IL-2 and TNF-alpha immunoreactivity. In contrast, sCR1 treatment did not affect the number of graft-infiltrating CD4(+) and CD8(+) T cells, CD45(+) B cells, ED1(+) and ED3(+) macrophages, or immune activation with expression of IL-2Ralpha or MHC class II. In conclusion, this is the first study to demonstrate that blockade of complement activation attenuates the development of OB and suggests that in addition to T cell-driven responses, humoral and antigen-independent immune responses also operate in the disease process. A blockade of complement activation renders the chemokine milieu unattractive to neutrophils and also modulates the alloimmune response toward Th2 cytokines, which may have an antiproliferative role in fibroproliferative disorders.

Soluble complement receptor-1 protects heart, lung, and cardiac myofilament function from cardiopulmonary bypass damage

BACKGROUND

Host defense system activation occurs with cardiopulmonary bypass (CPB) and is thought to contribute to the pathophysiological consequences of CPB. Complement inhibition effects on the post-CPB syndrome were tested with soluble complement receptor-1 (sCR1).

METHODS AND RESULTS

Twenty neonatal pigs (weight 1.8 to 2.8 kg) were randomized to control and sCR1-treated groups. LV pressure and volume, left atrial pressure, pulmonary artery pressure and flow, and respiratory system compliance and resistance were measured. Preload recruitable stroke work, isovolumic diastolic relaxation time constant (tau), and pulmonary vascular resistance were determined. Pre-CPB measures were not statistically significantly different between the 2 groups. After CPB, preload recruitable stroke work was significantly higher in the sCR1 group (n=5, 46.8+/-3.2x10(3) vs n=6, 34.3+/-3.7x10(3) erg/cm(3), P=0.042); tau was significantly lower in the sCR1 group (26.4+/-1.5, 42.4+/-6. 6 ms, P=0.003); pulmonary vascular resistance was significantly lower in the sCR1 group (5860+/-1360 vs 12 170+/-1200 dyn. s/cm(5), P=0.009); arterial PO(2) in 100% FIO(2) was significantly higher in the sCR1 group (406+/-63 vs 148+/-33 mm Hg, P=0.01); lung compliance and airway resistance did not differ significantly. The post-CPB Hill coefficient of atrial myocardium was higher in the sCR1 group (2.88+/-0.29 vs 1.88+/-0.16, P=0.023).

CONCLUSIONS

sCR1 meaningfully moderates the post-CPB syndrome, supporting the hypothesis that complement activation contributes to this syndrome.

Neuronal protection in stroke by an sLex-glycosylated complement inhibitory protein

Glycoprotein adhesion receptors such as selectins contribute to tissue injury in stroke. Ischemic neurons strongly expressed C1q, which may target them for complement-mediated attack or C1qRp-mediated clearance. A hybrid molecule was used to simultaneously inhibit both complement activation and selectin-mediated adhesion. The extracellular domain of soluble complement receptor-1 (sCR1) was sialyl Lewis x glycosylated (sCR1sLex) to inhibit complement activation and endothelial-platelet-leukocyte interactions. sCR1 and sCR1sLex colocalized to ischemic cerebral microvessels and C1q-expressing neurons, inhibited neutrophil and platelet accumulation, and reduced cerebral infarct volumes. Additional benefit was conferred by sialyl Lewis x glycosylation of the unmodified parent sCR1 molecule.

Blockade of antibody-induced glomerulonephritis with Crry-Ig, a soluble murine complement inhibitor

A recombinant soluble form of the mouse membrane complement inhibitor Crry (complement receptor-related gene y) fused to IgG1 hinge, CH2, and CH3 domains has been created and designated Crry-Ig. Crry has been used because, similar to human soluble CR1, it demonstrates decay-accelerating activity for both the classical and alternative pathways of complement as well as cofactor activity for factor I-mediated cleavage of C3b and C4b. The mouse IgG1 isotype was incorporated because it is a noncomplement-activating isotype and, when fused to Crry, results in a complement inhibitor that should not be recognized as foreign when used chronically in murine models. Crry-Ig demonstrated complement-inhibitory activity in both the fluid phase and on target surfaces. Following in vivo injection, Crry-Ig manifested a two-phase serum elimination profile, a rapid initial loss most likely reflecting tissue redistribution and a second more prolonged decline with a t1/2 of 40 h. Inhibition of complement activation in mice following injection of Crry-Ig was demonstrated by a marked decrease in the ability of serum from treated mice to be activated by zymosan particles in vitro. Finally, in vivo efficacy of Crry-Ig was demonstrated by its ability to substantially diminish renal injury induced by complement-fixing nephrotoxic Ab. The use of Crry-Ig in vivo in murine models of chronic inflammatory and autoimmune disease should allow further insight into the potential therapeutic effects and possible untoward complications of continuous blockade of complement using inhibitors that act on activation products of C4 and C3.

Soluble complement receptor type I limits damage during revascularization of ischemic myocardium

BACKGROUND

This study was undertaken to determine whether suppression of complement activation with soluble human complement receptor type I reduces myocardial damage during the revascularization of ischemic myocardium.

METHODS

In 20 pigs, the second and third diagonal coronary arteries were occluded for 90 minutes, followed by 45 minutes of cardioplegic arrest and 180 minutes of reperfusion. In 10 pigs, soluble human complement receptor type I (10 mg/kg) was infused over 30 minutes before the period of coronary occlusion; 10 other pigs received no soluble human complement receptor type I. Complement activation was measured by total hemolytic complement activity (expressed as a percentage of preischemic values). Ischemic damage was assessed by changes in myocardial tissue pH, wall motion scores (range, 4=normal to -1=dyskinesia), and infarct size (area of necrosis versus area at risk).

RESULTS

After 180 minutes of reperfusion, hearts treated with soluble human complement receptor type I had significantly less complement activation than nontreated hearts (1.1%+/-0.09% versus 7.8%+/-0.04%, respectively; p < 0.002), less myocardial acidosis (-0.41+/-0.03 versus -0.72+/-0.03, respectively; p < 0.0001), higher wall motion scores (3.1+/-0.09 versus 1.67+/-0.16, respectively; p < 0.0001), and smaller infarct size (24.6%+/-2.0% versus 41%+/-1.3%, respectively; p < 0.0001).

CONCLUSIONS

Complement inhibition with soluble human complement receptor type I significantly limits ischemic damage during the revascularization of acutely ischemic myocardium.

Soluble complement receptor 1 (sCR1) is not as effective as cobra venom factor in the treatment of experimental allergic neuritis

To further investigate the role of complement activation in Experimental Allergic Neuritis (EAN), the effect of systemic complement blockade by soluble CR1 (sCR1) was compared to complement depletion by Cobra Venom Factor (CVF) in EAN rats immunized with bovine peripheral nerve myelin. EAN rats treated with CVF (n = 10) had significantly reduced clinical scores compared to rats treated with sCR1 (n = 9) or saline (n = 10) (score: sCR1 0.66 +/- 0.7; CVF 0; saline 0.6 +/- 0.8; mean +/- SD). CVF treatment more effectively decreased inflammation and demyelination compared to sCR1 treatment which had only a partial effect (inflammation: sCR1 1.8 +/- 1.4; CVF 0.3 +/- 0.7; saline 1.9 +/- 1.2; demyelination; sCR1 1.3 +/- 1; CVF 0.1 +/- 0.6; saline 1.7 +/- 1.2). In lumbosacral nerve roots significantly less infiltrating ED1 positive macrophages and CD11bc (expressing complement receptor 3 or CR3) positive inflammatory cells were present in CVF treated EAN rats while there was a limited decrease in inflammation in the sCR1 treated animals compared to the saline treated rats (ED1: sCR1 1.4 +/- 1.2; CVF 0.5 +/- 0.6; saline 1.7 +/- 1.2; CD11bc: sCR1 1.9 +/- 1.2; CVF 0.9 +/- 1; saline 2.1 +/- 1.2). Our findings suggest that complement depletion by CVF is more effective than complement blockade by sCR1 in reducing the severity of inflammatory peripheral nerve demyelination.

Local therapy with soluble complement receptor 1 (sCR1) suppresses inflammation in rat mono-articular arthritis

Complement activation has been implicated in the pathogenesis of human rheumatoid arthritis. We sought to determine whether inhibition of complement (C) using sCR1 could influence the development and progression of antigen arthritis in the rat, a recognized model of human chronic synovitis. The effect of C inhibition, systemically and locally, on three different stages of disease was examined: (i) prophylaxis, (ii) treatment of established inflammation, and (iii) prevention of antigen-induced flares of disease. Arthritis was assessed by knee swelling and by histological examination. Our results show that intra-articular injection of sCR1 prior to disease onset reduced joint swelling and development of arthritis, whereas systemic administration was ineffective. Treatment of established arthritis with intraarticular sCR1 3 days after disease onset caused a transient reduction in swelling, but treatment 7 days after disease onset had no effect on disease. An intra-articular dose of sCR1 given at the time of disease flares had a small, yet significant effect on knee swelling. We conclude that complement activation is important in the initiation and maintenance of inflammation in antigen arthritis. The potent effect of local C inhibition suggests that C biosynthesis and activation within the joint contributes to inflammation in this model of arthritis.