Anthocyanin-rich polyphenols from Hibiscus syriacus activate autophagy to reverse polystyrene microplastic-induced...

The environmental accumulation of microplastics (MPs), defined as plastic particles ≤5 mm, has emerged as a critical global health concern, particularly owing to their potential to impair skeletal development and bone homeostasis.

This study aimed to determine whether anthocyanin-rich polyphenols extracted from Hibiscus syriacus L. (AH) could restore osteogenesis impaired by polystyrene MPs (PS-MPs) by targeting osteoblast senescence and autophagy regulation.

MC3T3-E1 preosteoblasts were exposed to PS-MPs followed by treatment with AH, and osteogenic recovery was evaluated via alkaline phosphatase (ALP) activity, calcium mineralization, and expression of osteogenic markers (RUNX2, SP7, and ALP) over 14 days. Senescence-associated secretory phenotype (SASP) markers (Tnf, Mmp13, Il6, and Il1b), key senescence regulators (p21, p27, MMP13, and Lamin B1), and autophagy markers (p62 and LC3B) were assessed using RT-qPCR, western blotting, and immunofluorescence. Zebrafish larvae were employed as an in vivo model to evaluate vertebral mineralization using calcein staining, as well as the expression of SASP osteogenic genes.

PS-MP exposure markedly reduced ALP activity, mineral deposition, and osteogenic gene/protein expression, while elevating senescence markers, indicative of severe osteoblast dysfunction. AH treatment significantly reversed these effects, effectively restoring ALP activity and mineralization. Furthermore, AH activated autophagy, as evidenced by increased LC3B and reduced p62 expression. In zebrafish, AH ameliorated PS-MP-induced defects in vertebral mineralization, reduced skeletal malformations, and upregulated osteogenic genes.

AH mitigates PS-MP-induced osteogenic dysfunction through the dual modulation of osteoblast senescence and autophagy activation, supporting its potential as a natural therapeutic strategy against MP-related skeletal disorders.