Burkholderia pseudomallei regulates lipid metabolism in HepG2 cells by inducing autophagy suppression

Abstract

Objective To investigate the regulatory effect of Burkholderia pseudomallei (B. pseudomallei)-induced autophagy suppression on lipid metabolism in HepG2 cells. Methods HepG2 cells infected by B. pseudomallei were observed for changes in intracellular lipid droplets and GFP-autophagy spots using confocal laser microscopy at 6, 12, 24 h following the infection. The levels of triglyceride and cholesterol in the cells were determined using a quantitative detection kit, and the expression levels of autophagy-related proteins LC3Ⅱ and p62 were detected with Western blotting. The effects of pretreatment with the autophagy inhibitors 3-MA and Baf-A1 or the autophagy activator Rapa prior to B. pseudomallei infection were examined on lipid metabolism in HepG2 cells. The changes in the intracellular survival of B. pseudomallei in response to exogenous free fatty acid triacsin C were examined by counting the viable bacteria in the cells. Results B. pseudomallei infection resulted in significantly increased number of intracellular lipid droplets at 6, 12 and 24 h after the infection and progressively increased levels of triglyceride and cholesterol in HepG2 cells over time, which reached the highest level at 24 h after the infection (P < 0.01). The cells infected by B. pseudomallei showed progressively lowered expression of LC3Ⅱ protein and increased expression of p62 protein over time with gradually decreased number of autophagosomes, which reached the lowest level at 24 h after the infection (P < 0.01), suggesting suppressed autophagy in HepG2 cells after B. pseudomallei infection. Inhibition of autophagy by pretreatment of the cells with 3-MA and Baf-A1 caused significantly increased intracellular lipid accumulation (P < 0.01), whereas activation of autophagy by Rapa obviously reduced the accumulation of intracellular lipids (P < 0.01). The addition of exogenous triacsin C significantly reduced the intracellular survival of B. pseudomallei (P < 0.01). Conclusion B. pseudomallei infection regulates intracellular lipid metabolism in HepG2 cells by inducting autophagy inhibition.

Keywords

• burkholderia pseudomallei
• hepg2 cells
• autophagy
• lipid metabolism