Carrageenan polysaccharides and oligosaccharides with distinct immunomodulatory activities in murine microglia BV-2 cells

This study was to investigate the anti-inflammatory activities in vitro of various carrageenans (Car) fractions (κ-, ι-, and λ-types) with well characterized molecular properties, using murine microglia BV-2 cell line treated with lipopolysaccharide (LPS) as model. It is indicated that pretreatments with the oligosaccharide fractions from κ- or ι-carrageenan acid hydrolysates (κ- and ι-CarAOS, respectively) at 125–500 μg/mL significantly and dose-dependently decreased the levels of tumor necrosis factor α (TNF-α) secreted from LPS-treated BV-2 cells, showing promisingly anti-inflammatory effects. Differently, pretreatments of most of polymeric carrageenans at 250–500 μg/mL significantly increased the TNF-α level, implying the co-inflammatory effects with LPS. The co-inflammatory effectiveness of pure carrageenans at 125 μg/mL was notable for λ-Car, followed by ι-Car, and insignificantly for κ-Car. Generally, cytokine TNF-α was a more sensitive biomarker to the presence of carrageenans than was the IL-6. The TNF-α level varied greatly at a low carrageenan concentration (125 μg/mL) and high polymer percentage (e.g. purified κ- and ι-Car). Conclusively, the anti-inflammatory effects on LPS-treated BV-2 cells could be attenuated by pretreatments with κ- and ι-CarAOS at 125–500 μg/mL. •Carrageenan oligosaccharides show anti-inflammation activities on LPS-treated BV-2 cells.•Carrageenan polysaccharides are co-inflammatory with LPS on LPS-treated BV-2 cells.•Key factors are carrageenan molecular property, type (sulfation content), and concentration.