The anti-malarial chloroquine modulated cytokine levels and increased animal survivability via Akt-mediated inhibition of GSK3β in Burkholderia pseudomalleiinfected mice.

Melioidosis is a common cause of fatal community-acquired septicaemia and pneumonia in endemic regions even with appropriate antibiotic treatments. The involvement of inflammatory cytokines in the manifestation of melioidosis is well-documented. Antibacterial and anti-inflammatory therapies may prove more efficacious against melioidosis rather than just anti-bacterial therapy alone. The phosphatidylinositol 3-kinase (PI3K)/Akt pathway has a central role in regulating the host inflammatory response; and glycogen synthase kinase-3β (GSK3β), a downstream effector molecule within this axis, plays a pivotal role in regulating the production of pro- and anti-inflammatory cytokines. The anti-malarial drug, chloroquine is a novel activator of Akt, and can elicit inhibition of GSK3β via PI3K/Akt signalling. LiCl, a GSK3 inhibitor is reported to increase survivability and modulate cytokine production in B. pseudomallei-infected mice. Here we determined the effects of chloroquine administration on animal survivability, cytokine levels and phosphorylation states of GSK3β (Ser9), Akt (Ser473) and NF-κB p65 (Ser536) in a murine model of acute melioidosis infection. Administration of 50 mg/kg b w chloroquine improved survivability (mean 67.0 ± 6.3%) of mice infected with 3 X LD B. pseudomallei compared to controls. Bacterial loads in spleen, liver, lung and blood of infected mice administered with chloroquine were significantly lower than controls. Western blot analysis revealed that the intensities of pAkt (Ser473) and pGSK3β (Ser9) in liver samples of mice administered with chloroquine were significantly (Pandlt;0.05) higher (2.3- and 4.4-fold respectively) compared to controls. On the other hand, chloroquine treatment signicantly decreased (Pandlt;0.05) phosphorylation of NF-κB p65 (Ser536) by 0.7-fold compared to control. Chloroquine administration also resulted in significantly reduced levels of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β and IL-18) but increased levels of antiinflammatory cytokines (IL-4 and IL-10) in sera and liver of B. pseudomallei-infected mice. Findings from this study demonstrate that the increased survivability of B. pseudomalleiinfected mice after chloroquine administration is at least in part due to its cytokine-modulating effects elicited via Akt-mediated inhibition of GSK3β that resulted in inhibition of NF-κB activation. This study represents laboratory evidence of the use of chloroquine for cytokine modulation and a plausible effective adjunctive therapeutic for B. pseudomallei infection.