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

Abstract

<b>Introduction.</b> Macrophages polarization is essential in infection control. Llipopolysaccharide (LPS) plays an essential role in host innate immune system-pathogen interaction. The LPS structure of <i>Pseudomonas aeruginosa</i> modifies in the adaptation of this pathogen to biofilm-related chronic infection.<b>Gap statement.</b> 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 <i>Pseudomonas aeruginosa</i> strain PAO1 was modified.<b>Aim.</b> This study aimed to investigate the effect and the involved pathway of LPS from biofilm-forming PAO1 on human and murine macrophage polarization.<b>Methodology.</b> 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, <i>IL4</i>, TNF-α, <i>CCL3</i>, and <i>CCL22</i> 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.<b>Results.</b> 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.<b>Conclusion.</b> The presented <i>in vitro</i> 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.