Regulatory role of GSK3β in the activation of NF-κB and modulation of cytokine levels in Burkholderia pseudomallei-infected PBMC isolated from streptozotocin induced diabetic animals

摘要

Increased susceptibility of diabetics to melioidosis, a disease caused by theBurkholderia pseudomallei bacterium is believed to be attributed to dysfunction of theinnate immune system. However, the underlying mechanism of the innate susceptibility is notwell-understood. Glycogen synthase kinase-3β (GSK3β) plays an important role in the innateinflammatory response caused by bacterial pathogens. The present study was conducted toinvestigate the effects of GSK3β inhibition by LiCl on levels of pro- and anti-inflammatorycytokines; and the activity of transcription factor NF-κB in B. pseudomallei-infected peripheralblood mononuclear cells (PBMC) derived from diabetic-induced and normal Sprague Dawleyrats. In addition, the effects of LiCl on intracellular bacterial counts were also investigated.Infection of PBMC from diabetic and normal rats with B. pseudomallei resulted in elevatedlevels of cytokines (TNF-α, IL-12 and IL-10) and phosphorylation of NF-κB in both cell types.Intracellular bacterial counts decreased with time in both cell types during infection. Howeverbacterial clearance was less prominent in diabetic PBMC. Burkholderia pseudomallei infectionalso caused inactivation (Ser9 phosphorylation) of GSK3β in normal PBMC, an effect absentin infected diabetic PBMC. Inhibition of GSK3β by LiCl lowered the levels of pro-inflammatorycytokines (TNF-α and IL-12) in both normal and diabetic PBMC. Similarly, phosphorylated NF-κB (pNF-κB) levels in both cell types were decreased with LiCl treatment. Also, LiCl was ableto significantly decrease the intracellular bacterial count in normal as well as diabetic PBMC.Interestingly, the levels of anti-inflammatory cytokine IL-10 in both normal and diabeticPBMC were further elevated with GSK3β inhibition. More importantly, GSK3β in infecteddiabetic PBMC was inactivated as in their non-diabetic counterparts upon LiCl treatment.Taken together, our results suggest that inhibition of dysregulated GSK3β in diabetic PBMCresulted in the inactivation of NF-κB and modulation of inflammatory cytokine levels. This isevidence that dysregulation of GSK3β is a contributing factor in the molecular basis of innatedysfunction and susceptibility of diabetic host to melioidosis infection.