The Mucilage From the Opuntia ficus-indica (L.) Mill. Cladodes Plays an Anti-Inflammatory Role in the LPS-Stimulated HepG2 Cells: A Combined In Vitro and In Silico Approach

The effect of a mucilage extracted from Opuntia ficus-indica (L.) Mill (OFI) cladodes was tested in lipopolysaccharide (LPS)-challenged HepG2 hepatocarcinoma cells, through a combined in vitro–in silico approach. The OFI mucilage was characterized by gas chromatography-mass spectrometry and liquid chromatography-high resolution mass spectrometry. In cells treated with OFI (5–10 µg/mL) prior to LPS (1 µg/mL, 24 h), the gene expression profile of pro-inflammatory mediators, namely tumor necrosis factor alpha, interleukin-1 beta, interleukin-8, and cyclo-oxygenase-2, was significantly (p < 0.01) reduced if compared to single LPS-challenged cells. The OFI-mediated cytokines reduction was also validated in polystyrene scaffold-grown 3D HepG2 cultures, undergoing treatment with the OFI mucilage (50 µg/mL, 24 h) and LPS stimulation (50 µg/mL, 24 h). We further demonstrated that OFI suppresses the LPS-triggered inflammatory response via impairment of the Toll-like receptor 4 (TLR4)/Myeloid differentiation protein-88/Nuclear factor-kappa B (NF-kB) pathway, by interfering with NF-kB phosphorylation at Serine 536. By molecular docking approach, we provided in silico demonstration of the direct molecular interaction between the mucilage monosaccharides and the TLR4 that interferes with the LPS receptor binding and down-stream inflammatory cascade activation. We also demonstrated that OFI cladodes mucilage downregulates the TLR4 pathway, showing an anti-inflammatory potential in HepG2 cells.