Saponins from Panax japonicus improve neuronal mitochondrial injury of aging rats.

Context: Panax japonicus is the dried rhizome of Panax japonicus C.A. Mey. (Araliaceae). Saponins from Panax japonicus (SPJ) exhibit anti-oxidative and anti-aging effects.
Objective: We evaluated the neuroprotective effects of SPJ on aging rats.
Materials and Methods: Sprague-Dawley rats (18-months-old) were randomly divided into aging and SPJ groups ( n  = 8). Five-month-old rats were taken as the adult control ( n  = 8). The rats were fed a normal chow diet or the SPJ-containing diet (10 or 30 mg/kg) for 4 months. An in vitro model was established by d-galactose (d-Gal) in the SH-SY5Y cell line and pretreated with SPJ (25 and 50 µg/mL). The neuroprotection of SPJ was evaluated via Nissl staining, flow cytometry, transmission electron microscopy and Western blotting in vivo and in vitro .
Results: SPJ improved the neuronal degeneration and mitochondrial morphology that are associated with aging. Meanwhile, SPJ up-regulated the protein levels of mitofusin 2 (Mfn2) and optic atrophy 1 (Opa1) and down-regulated the protein level of dynamin-like protein 1 (Drp1) in the hippocampus of aging rats ( p  < 0.05 or p  < 0.01 vs. 22 M). The in vitro studies also demonstrated that SPJ attenuated d-Gal-induced cell senescence concomitant with the improvement in mitochondrial function; SPJ, also up-regulated the Mfn2 and Opa1 protein levels, whereas the Drp1 protein level ( p  < 0.05 or p  < 0.01 vs. d-Gal group) was down-regulated.
Discussion and Conclusions: Further research on the elderly population will contribute to the development and utilization of SPJ for the treatment of neurodegenerative disorders.