The surface morphology of Platycodon grandiflorus polysaccharide and its anti-apoptotic effect by targeting autophagy

Fumonisin B1 is categorised as possible carcinogenic to humans which commonly contaminate maize and maize-based products worldwide, FB1, like other environmental pollutants, may activate apoptosis, autophagy, the inflammatory response and oxidative stress. Platycodon grandiflorus polysaccharide (PGPS_t) is prepared from a traditional herbal medicine in Asia with tremendous pharmacological activities. However, whether PGPS_t could relieve FB1-induced apoptosis has not been elucidated. The study aimed to evaluate the surface morphology of PGPS_t and its protective effect on fumonisin B1-induced apoptosis.

The surface morphology of PGPS_t was evaluated by SEM and AFM. Expressions of proteins involved in autophagy and apoptosis were detected by western blot analysis. Western blot, transient transfection, JC-1 and Annexin V-FITC/PI staining, CCK8, Live-cell imaging and autophagy inhibitor were used to observe the effect and explore the mechanism of PGPS_t on FB1-induced apoptosis of 3D4/21 cells.

PGPS_t had triple helix conformation, and had the characteristics of compact, polyporous and agglomerated morphology. PGPS_t promoted the expression of LC3-II and Beclin1, reduced the expression of p62, and significantly activated autophagy. PGPS_t inhibited the Akt/mTOR signaling pathway at 24 h. Besides, PGPS_t increased the expression of Bcl-2 and decreased the expression of Cleaved Caspase-3. PGPS_t-mediated autophagy was inhibited by 3-MA, accompanied by the upregulation of Caspase-3 and Cleaved Caspase-3, suggesting that enhanced autophagy inhibited apoptosis.

PGPS_t can activate autophagy, which in turn protects FB1-induced apoptosis. Targeting autophagy may provide a new way to improve the health of humans or animals in FB1 contaminated areas.