Human cerebral malaria causes neurological and behavioral deficits which persist long after resolution of infection and clearance of parasites with antimalarial drugs. Previously, we demonstrated that during active infection, mice with cerebral malaria demonstrated negative behavioral outcomes. Here we used a chloroquine treatment model of cerebral malaria to determine whether these abnormal outcomes would be persistent in the mouse model. C57BL/6 mice were infected with Plasmodium berghei ANKA, and treated for ten days. After cessation of chloroquine, a comprehensive assessment of cognitive and motor function demonstrated persistence of abnormal behavioral outcomes, 10 days after successful eradication of parasites. Furthermore, these deficits were still evident forty days after cessation of chloroquine, indicating persistence long after successful treatment, a hallmark feature of human cerebral malaria. Thus, cognitive tests similar to those used in these mouse studies could facilitate the development of adjunctive therapies that can ameliorate adverse neurological outcomes in human cerebral malaria. Published by Elsevier Masson SAS on behalf of the Institut Pasteur.

Neurological and cognitive impairment persist in more than 20% of cerebral malaria (CM) patients long after successful anti-parasitic treatment. We recently reported that long term memory and motor coordination deficits are also present in our experimental cerebral malaria model (ECM). We also documented, in a murine model, a lack of obvious pathology or inflammation after parasite elimination, suggesting that the long-term negative neurological outcomes result from potentially reversible biochemical and physiological changes in brains of ECM mice, subsequent to acute ischemic and inflammatory processes. Here, we demonstrate for the first time that acute ECM results in significantly reduced activation of protein kinase B (PKB or Akt) leading to decreased Akt phosphorylation and inhibition of the glycogen kinase synthase (GSK3β) in the brains of mice infected with Plasmodium berghei ANKA (PbA) compared to uninfected controls and to mice infected with the non-neurotrophic P. berghei NK65 (PbN). Though Akt activation improved to control levels after chloroquine treatment in PbA-infected mice, the addition of lithium chloride, a compound which inhibits GSK3β activity and stimulates Akt activation, induced a modest, but significant activation of Akt in the brains of infected mice when compared to uninfected controls treated with chloroquine with and without lithium. In addition, lithium significantly reversed the long-term spatial and visual memory impairment as well as the motor coordination deficits which persisted after successful anti-parasitic treatment. GSK3β inhibition was significantly increased after chloroquine treatment, both in lithium and non-lithium treated PbA-infected mice. These data indicate that acute ECM is associated with abnormalities in cell survival pathways that result in neuronal damage. Regulation of Akt/GSK3β with lithium reduces neuronal degeneration and may have neuroprotective effects in ECM. Aberrant regulation of Akt/GSK3β signaling likely underlies long-term neurological sequelae observed in ECM and may yield adjunctive therapeutic targets for the management of CM.

Aim To investigate the association between vasculopathy and survival during experimental cerebral malaria (ECM), and to determine whether targeting the endothelin-1 (ET-1) pathway alone or in combination with the anti-malaria drug artemether (a semi-synthetic derivative of artemisinin) will improve microvascular hemorrhage and survival. Main Methods C57BL/6 mice infected with Plasmodium berghei ANKA (PbA) were randomly assigned to four groups: no treatment, artemether treated, ETA receptor antagonist (HJP-272) treated, or HJP-272 and artemether treated. The uninfected control mice were treated with HJP-272 and artemether. We analyzed survival, cerebral hemorrhage, weight change, blood glucose levels and parasitemia. Key Findings Our studies demonstrated decreased brain hemorrhage in PbA-infected (ECM) mice treated when HJP-272, a 1,3,6-trisubstituted-2-carboxy-quinol-4-one novel ETA receptor antagonist synthesized by our group, is used in conjunction with artemether, an anti-malarial agent. In addition, despite adversely affecting parasitemia and weight in non-artemether treated infected mice, HJP-272, seemed to confer some survival benefit when used as adjunctive therapy, though this did not reach significance. Significance Previous studies demonstrate that the endothelin pathway is associated with vasculopathy, neuronal injury and inflammation in ECM. As demonstrated here, components of the ET-1 pathway may be important targets for adjunctive therapy in ECM, and may help in preventing hemorrhage and in improving survival when used as adjunctive therapy during malaria infection. The data presented suggest that our novel agent, HJP-272, may ameliorate alterations in the vasculature which can potentially lead to inflammation, neurological dysfunction, and subsequent death in mice with ECM.

No abstract