Escins Isolated from Aesculus chinensis Bge. Promote the Autophagic Degradation of Mutant Huntingtin and Inhibit its Induced Apoptosis in HT22 cells

Abstract

The pathogenesis of Huntington's disease (HD), an inherited progressive neurodegenerative disease, is highly associated with the cytotoxicity-inducing mutant huntingtin (mHtt) protein. Emerging evidence indicates that autophagy plays a pivotal role in degrading aggregated proteins such as mHtt to enhance neuronal viability. In this study, by employing preparative high-performance liquid chromatography (pre-HPLC), ultra-high performance liquid chromatography diode-array-detector quadrupole time-of-flight mass spectrometry (UHPLC-DAD-Q-TOF-MS) and nuclear magnetic resonance (NMR), three escins, escin IA (EA), escin IB (EB) and isoescin IA (IEA), were isolated and identified from the seed of Aesculus chinensis Bge. (ACB). After EGFP-HTT74-overexpressing HT22 cells were treated with EA, EB and IEA at safe concentrations, the clearance of mHtt and mHtt-induced apoptosis were investigated by Western blot, immunofluorescence microscopy and flow cytometry methods. In addition, the autophagy induced by these escins in HT22 cells was monitored by detecting GFP-LC3 puncta, P62 and LC3 protein expression. The results showed that EA, EB and IEA could significantly decrease mHtt levels and inhibit its induced apoptosis in HT22 cells. In addition, these three saponins induced autophagic flux by increasing the ratio of RFP-LC3 to GFP-LC3, and by decreasing P62 expression. Among the tested escins, EB displayed the best autophagy induction, which was regulated via both the mTOR and ERK signaling pathways. Furthermore, the degradation of mHtt and the commensurate decrease in its cytotoxic effects by EA, EB and IEA were demonstrated to be closely associated with autophagy induction, which depended on ATG7. In conclusion, we are the first to report that the escins, including EA, EB and IEA are novel autophagy inducers that degrade mHtt and inhibit mHtt-induced apoptosis in vitro and in vivo. As a result of these findings, the triterpenoid saponins in ACB might be considered to be promising candidates for the treatment of HD in the future.

Tissue Culture Response of Ornamental and Medicinal Aesculus Species—A Review

“…Aescin is a mixture of chemically related triterpenic glycosides. It is widely present in the seeds of virtually all Aesculus species: A. assamica [34][35][36], A. californica [37], A. chinensis [38,39], A. glabra [40], A. hippocastanum [41,42], A. indica [41], A. pavia [43,44] and A. turbinata [45,46]. Aescin content, in terms of compound profile and quantity, varies among the Aesculus species [44,47].…”

“…Many biological activities of aescin validate the traditional use of seed extracts. Aescin exhibits potent anti-inflammatory [31,32,48,49], anticancer [44,[50][51][52], antiviral [46,[53][54][55], antifungal [35], antidiabetic [34,45,48], antiedema [32], antioxidative [49,56,57] and anti-apoptotic [39] effects. Aescin is a promising phytochemical for anticancer drug development [50], as well as for the treatment of neurodegenerative diseases [39], neuropathy [58] and diabetic nephropathy [59].…”

“…Aescin exhibits potent anti-inflammatory [31,32,48,49], anticancer [44,[50][51][52], antiviral [46,[53][54][55], antifungal [35], antidiabetic [34,45,48], antiedema [32], antioxidative [49,56,57] and anti-apoptotic [39] effects. Aescin is a promising phytochemical for anticancer drug development [50], as well as for the treatment of neurodegenerative diseases [39], neuropathy [58] and diabetic nephropathy [59]. Since it can reduce inflammation and edema, aescin is being considered for use in addon therapy in acute lung injury related to COVID-19 infection [60].…”

Aescin Protects Neuron from Ischemia-Reperfusion Injury via Regulating the PRAS40/mTOR Signaling Pathway

“…Accumulating evidences suggest that the neurobiological function of aescin is related to the Akt and mammalian target of rapamycin (mTOR) signaling pathway [ 14 , 15 ]. For instance, aescin protected retinal pigment epithelium cells from oxidative stress via activating the Akt signaling pathway [ 16 ].…”

“…For instance, aescin protected retinal pigment epithelium cells from oxidative stress via activating the Akt signaling pathway [ 16 ]. In Huntington's disease, it promoted neurodegeneration through mTOR signaling pathways [ 15 ]. Our previous studies found that the mTOR signaling pathway played an important role in the protection against brain I/R injury both in vitro and in vivo [ 17 , 18 ].…”