Ergosterol promotes neurite outgrowth, inhibits amyloid-beta synthesis, and extends longevity: In vitro neuroblastoma and in vivo Caenorhabditis elegans evidence

Aims: Alzheimer's disease (AD), the most common neurodegenerative disorder associated with aging, is characterized by amyloid-beta (A beta) plaques in the hippocampus. Ergosterol, a mushroom sterol, exhibits neuroprotective activities; however, the underlying mechanisms of ergosterol in promoting neurite outgrowth and preventing A beta associated aging have never been investigated. We aim to determine the beneficial activities of ergosterol in neuronal cells and Caenorhabditis elegans (C. elegans). Materials and methods: The neuritogenesis and molecular mechanisms of ergosterol were investigated in wildtype and A beta precursor protein (APP)-overexpressing Neuro2a cells. The anti-amyloidosis properties of ergosterol were determined by evaluating in vitro A beta production and the potential inhibition of A beta-producing enzymes. Additionally, AD-associated transgenic C. elegans was utilized to investigate the in vivo attenuating effects of ergosterol. Key findings: Ergosterol promoted neurite outgrowth in Neuro2a cells through the upregulation of the transmembrane protein Teneurin-4 (Ten-4) mRNA and protein expressions, phosphorylation of the extracellular signal-regulated kinases (ERKs), activity of cAMP response element (CRE), and growth-associated protein-43 (GAP-43). Furthermore, ergosterol enhanced neurite outgrowth in transgenic Neuro2A cells overexpressing either the wild-type APP (Neuro2a-APPwt) or the Swedish mutant APP (Neuro2a-APPswe) through the Ten-4/ ERK/CREB/GAP-43 signaling pathway. Interestingly, ergosterol inhibited A beta synthesis in Neuro2a-APPwt cells. In silico analysis indicated that ergosterol can interact with the catalytic sites of beta- and gamma-secretases. In A beta-overexpressing C. elegans, ergosterol decreased A beta accumulation, increased chemotaxis behavior, and prolonged lifespan. Significance: Ergosterol is a potential candidate compound that might benefit AD patients by promoting neurite outgrowth, inhibiting A beta synthesis, and enhancing longevity.