Ballar Kirmizibayrak, P. | Search bioRxiv

bioRxiv2022

The role of Cycloastragenol at the intersection of Nrf-2/ARE, telomerase, and proteasome activity

Aging is well-characterized by the gradual decline of cellular functionality. As redox balance, proteostasis, and telomerase systems have been found to be associated with aging and age-related diseases, targeting these systems by small compounds has been considered as a promising therapeutic approach. Cycloastragenol (CA), a small molecule telomerase activator obtained from Astragalus species, has been reported to have positive effects on several age-related pathophysiologies, including ischemia, glucose intolerance, diabetes, and neurodegenerative diseases. Although CA has received intense attention as a promising compound for aging and age-related diseases, the mechanisms underlying CA activity related to redox balance, proteasome, and telomerase has not yet been reported. Here, we presented that CA increased Nrf-2 activity leading to upregulation of cytoprotective enzymes and attenuation of oxidative stress-induced ROS levels. Furthermore, CA enhanced telomerase activity by increasing not only the expression of hTERT but also its nuclear localization via the Hsp90-chaperon complex. CA alleviated the oxidative stress-induced mitochondrial hTERT levels while increasing the nuclear hTERT levels. Additionally, the proteasome activity and assembly were increased by CA. Strikingly, our data revealed that CA-mediated neuroprotection requires both Nrf-2 and hTERT induction. In conclusion, this study is the first report describing the effect of CA on these aging-related three major cellular pathways and their interrelationships. As the proteasome activator effect of CA is dependent on induction of telomerase activity, which is mediated by Nrf-2 system, CA has a great potential for healthier aging and prevention or treatment of age-related diseases by positively affecting these three cellular pathways.

cell biology↗

bioRxiv2021

Sapogenin based self-assembly structures activating a non-apoptotic cell death via multiple pathways

Induction of distinct cell death pathways is critical to deal with tumor heterogeneity and therapeutic resistance. In our previous study, we reported a promising saponin analog (AG-08) for cancer therapy inducing non-canonical necrotic cell death. Here, we describe that AG-08 forms unique supramolecular structures responsible for its biological activity. After internalization via non-canonical endocytosis pathway, these structures affect several cell signaling pathways including unfolded protein response, immune response, oxidative stress and heat stress. Moreover, we prepared 18 analogs to reveal the role of residues on the formation of supramolecular structures and biological activities. The results have demonstrated that unique structural features are required for particulate structures and unprecedented cell death mechanism. Although small molecule based supramolecular assemblies have widely been accepted as nuisance for drug discovery studies, our results indicate that they may provide a new research field for anti-cancer drug development studies.

pharmacology and toxicology↗