Pipecolic Acid, a Putative Mediator of the Encephalopathy of Cerebral Malaria and the Experimental Model of Cerebral Malaria

Abstract

Background: We explored a metabolic etiology of cerebral malaria (CM) coma.

Methods: Plasma metabolites were compared between Malawian children with CM and mild Plasmodium falciparum malaria. A candidate molecule was further studied in animal models of malaria.

Results: Clinically abnormal concentrations of pipecolic acid (PA) were present in CM plasma, and nearly normal in mild malaria samples. PA is renally cleared and the elevated PA blood levels were associated with renal insufficiency, which was present only in CM subjects. Prior studies demonstrate that PA has neuromodulatory effects and is generated by malaria parasites. PA brain levels in Plasmodium berghei ANKA-infected animals in the experimental cerebral malaria (ECM) model inversely correlated with normal behavior and correlated with blood-brain barrier (BBB) permeability. Mice infected with malaria species that do not induce neurological abnormalities or manifest BBB permeability had elevated plasma PA levels similar to ECM plasma at 7 days postinfection; however, they had low PA levels in the brain compared to ECM mice brains at 7 days postinfection.

Conclusions: Our model suggests that malaria-generated PA induces coma in CM and in ECM. The role of BBB permeability and the mechanisms of PA neuromodulation in CM will require additional investigation.

Keywords: blood-brain barrier; cerebral malaria; coma; experimental cerebral malaria model; pipecolic acid; renal insufficiency.