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Soluble human complement receptor type 1: in vivo inhibitor of complement suppressing post-ischemic myocardial
H F Weisman1, T Bartow, M K Leppo
1Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Insights
A novel soluble complement receptor type 1 (sCR1) effectively inhibits complement activation and reduces tissue damage in inflammatory diseases. This recombinant protein shows promise for treating autoimmune and inflammatory conditions by blocking key complement enzymes.
Area of Science:
- Immunology
- Biochemistry
Background:
- The complement system mediates acute inflammation and tissue damage in autoimmune and inflammatory diseases.
- Endogenous complement regulatory proteins can inhibit complement activation, but their therapeutic use is limited.
- Complement receptor type 1 (CR1) has significant inhibitory potential but is restricted to specific cell types.
Purpose of the Study:
- To investigate the potential of recombinant, soluble human CR1 (sCR1) as a therapeutic agent for complement-mediated tissue injury.
- To evaluate the efficacy of sCR1 in inhibiting complement activation and reducing inflammation in vivo.
Main Methods:
- sCR1 was engineered to lack transmembrane and cytoplasmic domains, enabling soluble function.
- sCR1's binding to complement components C3b and C4-ma and its promotion of factor I-mediated inactivation were assessed.
- Complement activation in human serum was measured in the presence of sCR1.
- The anti-inflammatory and complement inhibitory effects of sCR1 were evaluated in a rat model of myocardial reperfusion injury.
Main Results:
- sCR1 effectively bound dimeric C3b and C4-ma, promoting their inactivation by factor I.
- Nanomolar concentrations of sCR1 inhibited complement activation via both major pathways in human serum.
- sCR1 demonstrated significant complement inhibitory and anti-inflammatory activities in vivo.
- Treatment with sCR1 reduced myocardial infarction size by 44% in a rat model of reperfusion injury.
Conclusions:
- Recombinant soluble CR1 (sCR1) is a potent inhibitor of complement activation.
- sCR1 effectively reduces tissue damage in models of inflammatory injury.
- sCR1 represents a promising therapeutic candidate for suppressing complement-dependent tissue injury in autoimmune and inflammatory diseases.
Abstract:
The complement system is an important mediator of the acute inflammatory response, and an effective inhibitor would suppress tissue damage in many autoimmune and inflammatory diseases. Such an inhibitor might be found among the endogenous regulatory proteins of complement that block the enzymes that activate C3 and C5. Of these proteins, complement receptor type 1 (CR1; CD35) has the most inhibitory potential, but its restriction to a few cell types limits its function in vivo. This limitation was overcome by the recombinant, soluble human CR1, sCR1, which lacks the transmembrane and cytoplasmic domains. The sCR1 bivalently bound dimeric forms of its ligands, C3b and methylamine-treated C4 (C4-ma), and promoted their inactivation by factor I. In nanomolar concentrations, sCR1 blocked complement activation in human serum by the two pathways. The sCR1 had complement inhibitory and anti-inflammatory activities in a rat model of reperfusion injury of ischemic myocardium, reducing myocardial infarction size by 44 percent. These findings identify sCR1 as a potential agent for the suppression of complement-dependent tissue injury in autoimmune and inflammatory diseases.