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.

This study compared the accuracy of measurements of the skull base made using computed tomography (CT) images and an image-guided surgery system with those made using scientific callipers in order to evaluate the practicability of replacing conventional direct anatomical measurements with digitized techniques in skull base surgery. Important bony landmarks and parameters were measured using the three different methods in 25 cadaver skull bases. No statistically significant differences were observed between the methods. Coefficient of variation calculations indicated that data obtained from CT images was the most stable. Digital methods of navigation have the potential to reflect individual skull base anatomical features more accurately than traditional group-based data, but it is important to assess their accuracy. This study demonstrated that CT imageology and image-guided surgery systems can provide accurate anatomical measurements. Digital methods are also more flexible and less variable, and may have wide applications in this field. Though not perfect, digital imaging is a promising tool for skull base surgery.