Lipopolysaccharide from biofilm-forming Pseudomonas aeruginosa PAO1 induces macrophage hyperinflammatory responses

INTRODUCTION: Macrophages polarization is essential in infection control. Llipopolysaccharide (LPS) plays an essential role in host innate immune system–pathogen interaction. The LPS structure of Pseudomonas aeruginosa modifies in the adaptation of this pathogen to biofilm-related chronic infection. GAP STATEMENT: There have been several studies on LPS induced polarization of human and mouse macrophages with different results. And it was reported that the lipid A structure of the LPS derived from biofilm-forming Pseudomonas aeruginosa strain PAO1 was modified. AIM: This study aimed to investigate the effect and the involved pathway of LPS from biofilm-forming PAO1 on human and murine macrophage polarization. METHODOLOGY: LPS was isolated from biofilm-forming and planktonic PAO1 and quantified. Then the LPS was added to PMA-differentiated human macrophage THP-1 cells and Raw264.7 murine macrophage cells. The expression of iNOS, Arg-1, IL4, TNF-α, CCL3, and CCL22 was analysed in the different cell lines. The expression of TICAM-1 and MyD88 in human THP-1 macrophages was quantified by Western blot. PAO1 infected macrophages at different polarization states, and the intracellular bacterial growth in macrophages was evaluated. RESULTS: LPS from biofilm-forming PAO1 induced more marked hyperinflammatory responses in THP-1 and Raw264.7 macrophages than LPS derived from planktonic PAO1, and these responses were related to the up-regulation of MyD88. Intracellular growth of PAO1 was significantly increased in THP-1 macrophages polarized by LPS from biofilm-forming PAO1, but decreased both in THP-1 and Raw264.7 macrophages polarized by LPS from planktonic PAO1. CONCLUSION: The presented in vitro study indicates that LPS derived from biofilm-forming PAO1 induces enhanced M1 polarization in human and murine macrophage cell lines than LPS from planktonic PAO1.