Gene expression analysis of inflammation-related genes in macrophages treated with α-(1 → 3, 1 → 6)-D-glucan extracted from Streptococcus mutans

Abstract

Streptococcus mutans is a gram-positive bacterium that causes tooth decay. The exopolyssacharides, mostly glucans synthesized by the bacterium are responsible for establishing pathogenic bio-films associated with dental caries disease. The regulatory immune and inflammatory reactions implicated by the synthesized glucans are still not clearly understood. In this study, a water-soluble exopolyssacharide (WSP) was extracted from culture of Str. mutans. The structural properties of WSP, [α-(1 → 3, 1 → 6)-D-glucan] were confirmed using Fourier-transform infrared spectroscopy and ¹³C-nuclear magnetic resonance spectroscopy. Furthermore, the effects of WSP on the global gene expression of the macrophage-like RAW 264.7 cells were analyzed using mRNA-seq analysis. Using Gene Ontology analysis, we compiled a total of 24,421 genes that were upregulated or downregulated by more than 5.0-fold and 0.3-fold, respectively. Most of the transcripts were grouped under immune response and inflammation-related gene categories. Among the 802 immunity-related genes analyzed, chemokine ligand 7 (Ccl7), interleukin-1β (IL-1β), interleukin-1α (IL-1α) and interleukin-6 (IL-6) were upregulated after WSP exposure. In addition, among a total of 344 genes related to inflammation, Ccl7, IL-1α and IL-6 were upregulated. These results suggest that [α-(1 → 3, 1 → 6)-D-glucan] from Str. mutans produces activates macrophages and may contribute to the immune and inflammatory response to periodontal disease.

Keywords: Gene expression profile; Glucan; Immunity genes; Inflammatory genes; Streptococcus mutans; mRNA-seq.