Sulfated fucopyranosyl-glucosamino-glucopyranose from marine heterotrophic Bacillus tequilensis regulates inflammatory cytokines in lipopolysaccharide-stimulated human monocyte THP-1 cells

Abstract

Marine macroalga or seaweed-associated bacterial exopolysaccharides, particularly (1 → 3)-linked β-glucans, possess potential ability to reduce inflammatory responses by targeting various cytokines. In this direction, a sulfated exopolysaccharide (BP-2), characterized as fucopyranosyl-glucosamino-glucopyranose, was isolated from the heterotrophic bacterium Bacillus tequilensis MTCC13043, associated with the brown seaweed Sargassum wightii. The whole-genome analysis of B. tequilensis MTCC13043 (accession number: JAKGAV000000000) revealed that 97 % of its genome consisted of biosynthetic gene clusters for specific saccharide molecules. Administration of BP-2 (50 μg/mL) on lipopolysaccharide (LPS)- induced THP-1 monocytic cell line resulted in a substantial reduction in overexpressed nitric oxide (∼56 %), tumor necrosis factor (TNF-α) (∼81 %), interleukins (IL-6, IL-12, and IL-1β) (∼50–66 %). Significant downregulation of mRNA expression of IL-2 (1.65-fold) and interferon-gamma (IFN-γ) (2.15-fold) was observed in BP-2 (50 μg/mL) treated cells, in comparison with LPS-treated cells (3.81–5.06-fold), whereas the expression of inflammation- regulatory transforming growth factor (TGF)-β was upregulated (∼80 %, 4.85-fold) upon treatment with BP-2 (50 μg/mL). The structure-activity correlations revealed that (1 → 3) β-glycosidic linkage, along with C-6/C-4,6 sulfation patterns in BP-2 are likely responsible for its prospective anti-inflammatory property. These findings highlight the potential of the isolated bacterial exopolysaccharide (BP-2) as a promising anti-inflammatory agent