Blockade of fatty acid signalling inhibits lipopolysaccharide‐induced macrophage recruitment and progression of apical periodontitis

Abstract

Aim To examine the role of palmitic acid in lipopolysaccharide (LPS)‐stimulated chemotaxis of macrophages and the potential contribution of saturated fatty acid in signalling during the pathogenesis of apical periodontitis. Methodology J774, a mouse macrophage cell line, was used in the experiments. After treatment with LPS, proteolytic maturation of sterol regulatory element‐binding protein‐1c (SREBP‐1c) and expression of fatty acid synthase (FASN) were examined by Western analysis. Levels of palmitic acid were measured by reverse phase‐high performance liquid chromatography‐mass spectrometry. Knockdown of SREBP‐1c and FASN was accomplished by small interfering RNA technology. Secretion of CC‐chemokine ligand 2 (CCL2) and cellular chemotaxis were assessed by enzyme‐linked immunosorbent assay and transwell migration assay, respectively. Sulfo‐N‐succinimidyl oleate (SSO) treatment was used to inhibit fatty acid signalling in vitro and also in a rat model of apical periodontitis. All data were first subjected to Levene’s test. In vitro data were then analysed using ANOVA followed by Tukey’s multiple comparison test. Data from animal experiments were analysed by independent t‐tests. The significant level was set at 0.05. Results LPS stimulated proteolytic maturation of SREBP‐1c and FASN expression in macrophages and significantly enhanced palmitic acid synthesis (P < 0.05). Knockdown of SREBP‐1c attenuated LPS‐enhanced FASN expression. Knockdown of FASN significantly suppressed LPS‐enhanced palmitic acid synthesis (P < 0.05). LPS and exogenous palmitic acid significantly enhanced CCL2 secretion and macrophage chemotaxis (all P < 0.05). Inhibition of FASN expression significantly alleviated LPS‐augmented CCL2 secretion (P < 0.05). SSO significantly suppressed CCL2 secretion and macrophage chemotaxis augmented by LPS and palmitic acid (all P < 0.05). In a rat model of induced apical periodontitis, SSO treatment significantly attenuated progression of apical periodontitis and macrophage recruitment (all P < 0.05). Conclusions LPS/SREBP‐1c/FASN/palmitic acid signalling contributed to tissue destruction caused by bacterial infection. Modulation of lipid metabolism and signalling may be helpful for the management of apical periodontitis.

NLRP3 Cys126 palmitoylation by ZDHHC7 promotes inflammasome activation

“…Our study shows that NLRP3 is palmitoylated in the resting state and that the palmitoylation is enhanced in LPS-primed BMDMs or PMA-differentiated THP-1 cells ( Figure 1A and 1B ). Previous work has suggested that LPS could significantly accelerate palmitic acid synthesis by inducing the expression of fatty acid synthase (FASN) and the maturation of sterol regulatory element binding protein 1c (SREBP-1c) in macrophages, 54 , 55 which might contribute to the enhanced NLRP3 S -palmitoylation in primed macrophages. After activation with ATP or nigericin, NLRP3 S -palmitoylation remains ( Figure 1A , 1B , and 1G ), suggesting that S -palmitoylation may continue to stabilize NLRP3 on dTGN, which facilitates its transport to the MTOC and recruitment of adaptors to mediate inflammasome activation.…”

NLRP3 Cys126 palmitoylation by ZDHHC7 Promotes Inflammasome Activation

“…Our study shows that NLRP3 is palmitoylated at resting state and the palmitoylation is enhanced in LPS-primed BMDMs or PMA-primed THP-1 cells (Figure 1A, B). Previous work suggested that LPS could significantly accelerate palmitic acid synthesis by inducing the expression of fatty acid synthase (FASN) and the maturation of Sterol Regulatory Element Binding Protein-1c (SREBP-1c) in macrophages 54,55 , which might contribute to the enhanced NLRP3 S -palmitoylation in primed macrophages. After activation with ATP or nigericin, NLRP3 S -palmitoylation remains (Figure 1A, B, H), suggesting that S -palmitoylation may continue to stabilize NLRP3 on dispersed TGN, which facilitates its transport to the MTOC and recruitment of adaptors to mediate inflammasome activation.…”

Pathophysiology of cellulite: Possible involvement of selective endotoxemia

“…Additionally, LPS stimulates expression of FASN and significantly enhances palmitic acid synthesis in macrophages. 62 Remarkably, combination of LPS with palmitic acid demonstrates a synergistic impact upon induction of the monocyte chemoattractant protein‐1, thus amplifying inflammation in WAT. 63 Similar interactions between LPS and palmitic acid were also reported in microglial activation and neuroinflammatory responses.…”