Aqueous Polygalae Radix extract (PRE) prolongs the lifespan of C. elegans and alleviates D-galactose-induced oxidative stress in the mouse liver and brain by modulating PPARγ/MAPK.

ETHNOPHARMACOLOGICAL RELEVANCE: Polygalae Radix has high pharmacological activity and has been widely used as a sedative and tranquilizer to increase cognitive function, prevent epilepsy, and treat respiratory diseases such as bronchitis. However, its role in delaying aging and decreasing oxidative stress and its main functional factors have not been thoroughly studied.

AIM OF THE STUDY: The purpose was to investigate the antiaging and antioxidant effects of aqueous Polygalae Radix extract (PRE) and its mechanism of action.

MATERIALS AND METHODS: The effects of different concentrations (1, 5, and 10 mg/mL) of PRE on the lifespan, body length, reproductive ability, motility, lipofuscin, and reactive oxygen species (ROS) on a model of natural senescence of Caenorhabditis elegans were investigated. The effects of PRE treatment on the expression of body weight, malondialdehyde (MDA), glutathione peroxidase (GSH-PX), and mTERT content were evaluated in a D-galactose (Dgal)-induced mouse model of aging. Histopathological changes in the liver and brain of mice were analyzed by hematoxylin-eosin (HE). The enriched pathways associated with differentially expressed genes in the liver tissues of C. elegans and mice were analyzed via RNA-seq, and the results were verified via RT-qPCR, cell transfection and Western blotting. Abundance of and changes in the mouse intestinal flora were analyzed by 16S rDNA sequencing.

RESULTS: PRE significantly prolonged the average lifespan of C. elegans and improved the physiological indices related to senescence. In addition, PRE slowed the decrease in weight of senescent model mice; protected serum, liver and brain tissues from oxidative stress damage; increased GSH-PX expression; and reduced MDA expression. The role of PRE in the low- and middle-dose groups was similar to that of vitamin C (VC) in inhibiting oxidative stress, but the effect of PRE in the high-dose group was greater than that of VC. The RNA-seq results suggested that PRE might be related to PPARγ/MAPK, and the subsequent RT-qPCR and cell transfection results indicated that PRE decreased oxidative stress by downregulating the mRNA expression of the Fabp1, Acaa1b, Hmgcs1, Map3K5, and Rac2 genes. The Western blot results revealed that PRE decreased oxidative stress by increasing PPARγ expression and inhibiting p38 protein phosphorylation. 16S rDNA sequencing showed that PRE treatment increased the abundance of the intestinal flora in mice and inhibited the growth of pathogenic bacteria such as Helicobacter pylori and Desulfurization vibrio while promoting the growth of beneficial bacteria such as Bifidobacteria.

CONCLUSIONS: PRE delays aging and resists oxidative stress in organisms; it may act by regulating the PPARγ/MAPK signaling pathway and the intestinal flora. The efficacy and mechanism of PRE against oxidative stress were elucidated using RNA-seq and 16S rDNA sequencing, providing a reference for antiaging and aging-related diseases.