SB290157 trifluoroacetate

SB 290157 functions as a competitive antagonist of 125I-C3a radioligand binding to rat basophilic leukemia (RBL)-2H3 cells expressing the human C3aR (RBLC3aR), with an IC50 of 200 nM. SB 290157 is a functional antagonist, blocking C3a-induced C3aR internalization in a concentration-dependent manner and C3a-induced Ca21 mobilization in RBL-C3aR cells and human neutrophils with IC50s of 27.7 and 28 nM, respectively. SB 290157 is selective for the C3aR in that it does not antagonize the C5aR or six other chemotactic G protein-coupled receptors. Functional antagonism is not solely limited to the human C3aR; SB 290157 also inhibits C3ainduced Ca21 mobilization of RBL-2H3 cells expressing the mouse and guinea pig C3aRs. It potently inhibits C3a-mediated ATP release from guinea pig platelets and inhibits C3a-induced potentiation of the contractile response to field stimulation of perfused rat caudal artery.^[1]

2–5 × 10⁵ RBL-C3aR cells are incubated with 100 pM ¹²⁵I-C3a and varying concentrations of antagonist at room temperature in 20 mM HEPES (pH 7.4), 125 mM NaCl, 5 mM KCl, 1 mM CaCl2, 1 mM MgCl2, 0.25% BSA and 0.5 mM glucose (HAG-CM) for 45 min at room temperature. The unbound ligand is removed by vacuum filtration using the HV Millipore MultiScreen assay plate with a Durapore 0.45-mm pore size membrane equilibrated with HAG-CM. Filters are washed twice with 100 ml/well HAG-CM and dried. Plates are counted on a Beckman gamma counter 5500B.

In animal models, SB 290157, inhibits neutrophil recruitment in a guinea pig LPS-induced airway neutrophilia model and decreases paw edema in a rat adjuvant-induced arthritis model.^[1]