Immunometabolism of Dendritic Cells in Porphyromonas Gingivalis-Stimulated Hyperglycemic Microenvironment

Objectives: Chronic periodontitis and diabetes mellitus (DM) are chronic inflammatory diseases that exert a bidirectional relationship to each other. The immune-inflammatory response against multispecies bacterial biofilms in periodontal pocket triggers destruction of periodontal tissues. DM induces exacerbation of periodontitis due to dysregulation of both innate and adaptive immune cells. Dendritic cells (DC) are the most efficient antigen presenting cells due to their unique capability to connect both innate and adaptive immunity, and their presence is critical to maintain oral immune homeostasis. The effect of DM on the immune-metabolism of DCs have not been well understood. This study aimed to investigate the effect of diabetic microenvironment and periodontal pathogen on morphology, phenotype, and metabolism of DC.
Methods: Human monocyte derived-DC (THP-1) were cultured in 5.5-, 11-, and 25 mM glucose and stimulated with advanced glycation end-products (AGE) and lipopolysaccharides (LPS) of Porphyromanas. gingivalis (P. gingivalis) (24 hours). The cell morphology was assessed by confocal microscopy and the phenotypic changes of surface markers were quantified via RT-qPCR. Seahorse assay, lactate assay, and OXPHOS assay were utilized to examine DC metabolism together with gene expressions of glycolytic proteins c-Myc, HK2, LDHA, GLUT1.
Results: In comparison to the control samples in unstimulated 5.5-mM glucose culture, DC cultured in higher glucose concentrations showed increased dendrites formation with significantly upregulated activation of surface markers. DC metabolism under stress of glucose, AGE, and LPS was of glycolytic nature, confirmed by the significantly high extracellular acidification rate, lactic acid assay and glycolytic proteins in diabetic microenvironment. Whereas the OXPHOS assay was reversed signifying glycolytic metabolism.
Conclusions: This study indicated hyperglycemia, AGE, and P. gingivalis LPS affect the immune-metabolism of DC by increased activation as well as metabolic pathways. Rescuing tolerogenicity of DC could provide new insights to improve therapeutic outcome of periodontitis with DM.