Dual Anti-Malarial and GSK3ß-Mediated Cytokine-Modulating Activities of Quercetin Are Requisite of Its Potential as a Plant-Derived Therapeutic in Malaria.

Although death in malaria is attributed to cerebrovascular blockage and anaemia, overwhelming cytokine production can contribute to the severity of the disease. Therefore, mitigation of dysregulated inflammatory signalling may provide further benefit for malaria treatment. Quercetin (3,3',4',5,7-pentahydroxyflavone) is known to inhibit glycogen synthase kinase-3ß (GSK3ß), a potent regulator of both pro- and anti-inflammatory effects. Quercetin is therefore a potential therapeutic to modulate the imbalanced cytokine production during malarial infection. Anti-malarial effects of quercetin were evaluated in murine models of severe and cerebral malaria using Plasmodium berghei NK65 and ANKA strains, respectively. Western blotting and analysis of cytokines were carried out to determine the GSK3ß-mediated cytokine-modulating effects of quercetin in infected animals. Quercetin (25 mg/kg BW) treatment in P. berghei NK65-infected animals resulted in 60.7 ± 2.4% suppression of parasitaemia and significantly decreased serum levels of TNF-α and IFN-γ, whilst levels of IL-10 and IL-4 were elevated significantly. Western analysis revealed that pGSK3ß (Ser9) increased 2.7-fold in the liver of quercetin-treated NK65-infected animals. Treatment of P. berghei ANKA-infected mice with quercetin (15 mg/kg BW) increased (2.3-fold) pGSK3ß (Ser9) in the brains of infected animals. Quercetin is a potential plant-derived therapeutic for malaria on the basis that it can elicit anti-malarial and GSK3ß-mediated cytokine-modulating effects.