Bradykinin contributes to vasogenic edema in murine experimental cerebral malaria

Cerebral malaria (CM) from Plasmodium falciparum is a major cause of death in African children. Since bradykinin (BK) is a mediator of vasogenic edema, we hypothesized that it contributes to the pathogenesis of CM in Kenyan children and Plasmodium berghei ANKA (PbA) infected C57BL/6J mice in experimental cerebral malaria (ECM). Cleaved plasma high molecular weight kininogen (cHK) is a marker for BK release. 40% of children with central nervous system malaria had plasma cHK versus 18% of children with uncomplicated malaria. Wild-type PbA-infected mice with ECM had circulating cHK, elevated BK levels, and reduced HK and prekallikrein activity/antigen levels. HK null (Kng1(–/–)), combined BK B1 and B2 receptor null (Bdkrb1(–/–)/Bdkrb2(–/–)), BK B2 (Bdkrb2(–/–)) or BK B1 (Bdkrb1(–/–)) receptor null mice were protected significantly from neurologic deterioration and brain edema compared to wild-type mice. F12(–/–) mice were not protected from neurological deterioration. Prekallikrein null (Klkb1(–/–)), prolylcarboxypeptidase hypomorphs (Prcp(gt/gt)), and brain endothelial cell conditional knockout of PRCP (Prcp(fl/fl) Cre) mice with ECM had reduced neurologic deterioration and brain edema. Adjuvant plasma kallikrein inhibition combined with artesunate treatment in PbA-infected mice reversed neurologic deterioration and brain edema and significantly prolonged survival over artesunate alone. BK-induced vasogenic edema contributes to human and murine CM.