Kinsenoside from Anoectochilus roxburghii (Wall.) Lindl. suppressed oxidative stress to attenuate aging-related learning and memory impairment via ERK/Nrf2 pathway

Anoectochilusroxburghii (Wall.) Lindl. (AR), as an exceptionally valuable traditional Chinese medicine, has been widely used to treat hepatitis, cancer, diabetes, etc. But, the effects and the primary functioning element of AR on attenuating aging and aging-related learning and memory degradation has not yet been explored.This study aimed at exploring the protective property of aqueous extract of AR (AEAR) on alleviation of aging and aging-related learning and memory impairment in vivo, and further investigating the main active ingredient and mechanism of AEAR.D-galactose (D-gal) induced aging mice and HT22 cells exposed with L-Glutamic acid (Glu) were used as in vivo and in vitro model, separately. The effects of AEAR on aging and aging-related learning and memory degradation were explored by using morris water maze test, immunohistochemistry staining, biochemistry assay, etc. The effects and mechanism of AEAR and Kinsenoside (Kin) on antioxidation in vitro were investigated by cell viability assay, biochemistry assay, qRT-PCR, western blotting and molecular docking studies.Treatment with AEAR (containing 69.52 ± 0.85% Kin, i.g.) for 63 days, alleviated low growth rate, abnormal brain, liver and thymus index, and decline in learning and memory capability of aging mice. Meanwhile, AEAR inhibited the decreased activities of SOD and GSH-PX, the decline in the ratio of GSH to GSSG, and the increase of MDA in both serum and brain, and also promoted the Nrf2 nuclear translocation in brain of aging mice induced by D-gal. The effects of AEAR on alleviating abnormal physiological characteristics, attenuating learning and memory impairment, and inhibiting oxidative stress in aging mice was similar to or even better than that of Vc. In HT22 cells exposed with Glu, Kin increased the cell viability, up-regulated the activities of SOD and GSH-PX, enhanced the ratio of GSH to GSSG, and down-regulated MDA, which was superior to AEAR. Kin up-regulated the ratio of p-ERK1/2 to ERK1/2, promoted the Nrf2 nuclear translocation and its downstream target genes, i.e. HO-1, NQO-1, GCLC and GCLM expression at the mRNA and protein levels, which were consistent with AEAR. Further, molecular docking results also confirmed that Kin had strong binding energy with ERK1 and ERK2.The present study indicated that Kin could alleviate the oxidative stress in aging mice via activating the ERK/Nrf2 signaling pathway, in order to attenuate aging and aging-related learning and memory impairment, as the main active ingredient of AR.