Anti-Inflammatory Activity of Biotransformed Platycodon grandiflorum Root Extracts Containing 3-O-β-D-Glucopyranosyl Platycosides in LPS-Stimulated Alveolar Macrophages, NR8383 Cells.

Acute lung injury (ALI) is a severe inflammatory condition characterized by excessive immune responses and oxidative stress, leading to significant tissue damage. Given the need for novel therapeutic agents, this study aimed to explore the anti-inflammatory activity and mechanisms of biotransformed Platycodon grandiflorum root extracts (BT-PGR), which were enzymatically processed using rapidsase PL Classic from Aspergillus niger. The goal was to assess the potential of BT-PGR as a natural treatment for ALI. BT-PGR effectively inhibited the production of NO, iNOS, IL-1β, IL-6, and TNF-α induced by LPS in NR8383 cells. BT-PGR inhibited the phosphorylation of ERK1/2, p38, JNK and p65 in LPS-stimulated NR8383 cells. In addition, BT-PGR suppressed LPS-mediated activation of NFκB luciferase activity. BT-PGR increased the levels of HO-1 and the inhibition of HO-1 by ZnPP attenuated BT-PGR-mediated inhibition of NO production. In addition, the inhibition of PI3K by LY294002 blocked the BT-PGR-mediated increase of HO-1 level. BT-PGR increased nuclear Nrf2 level and the knockdown of Nrf2 by siRNA inhibited BT-PGR-mediated increase of HO-1 level. In addition, inhibition of PI3K by LY294002 suppressed the increase of nuclear Nrf2 level. Based on these results, it can be inferred that BT-PGR exhibits anti-inflammatory activity in rat alveolar macrophages, suggesting its potential as a natural candidate for the improvement of ALI.