Profiling withanolide A for therapeutic targets in neurodegenerative diseases

Abstract

To identify new potential therapeutic targets for neurodegenerative diseases, we initiated activity-based protein profiling studies with withanolide A (WitA), a known neuritogenic constituent of Withania somnifera root with unknown mechanism of action. Molecular probes were designed and synthesized, and led to the discovery of the glucocorticoid receptor (GR) as potential target. Molecular modeling calculations using the VirtualToxLab predicted a weak binding affinity of WitA for GR. Neurite outgrowth experiments in human neuroblastoma SH-SY5Y cells further supported a glucocorticoid-dependent mechanism, finding that WitA was able to reverse the outgrowth inhibition mediated by dexamethasone (Dex). However, further GR binding and transactivation assays found no direct interference of WitA. Further molecular modeling analysis suggested that WitA, although forming several contacts with residues in the GR binding pocket, is lacking key stabilizing interactions as observed for Dex. Taken together, the data suggest that WitA-dependent induction of neurite outgrowth is not through a direct effect on GR, but might be mediated through a closely related pathway. Further experiments should evaluate a possible role of GR modulators and/or related signaling pathways such as ERK, Akt, NF-B, TR, or Hsp90 as potential targets in the WitA-mediated neuromodulatory effects.

Natural withanolides, an update

“…Further experiments showed that withanolide A-dependent induction of neurite outgrowth was not achieved by a direct effect on GR, but might be mediated through a closely related pathway, such as ERK, Akt, NF-κB, TRα, or Hsp90. 222 These studies indicate that the efficacy of withanolides on neurons can be utilized to tackle age-related diseases, such as Parkinson's disease and Alzheimer's disease. The glutathione derivative CR-777 ( 320 ) could protect dopaminergic and cortical neurons at nanomolar concentrations, and the observed role of 320 seemed to involve the PI3K/mTOR pathway, indicating that 320 could be considered as a protective agent against a large panel of neuronal stressors.…”

Natural Products and Their Bioactive Compounds: Neuroprotective Potentials against Neurodegenerative Diseases

“…Collectively, the possible mechanism underlying the neuroprotective actions of Withania somnifera could be mediated through several pathways. Several studies have suggested that the protective effect of withanoside IV [119], withanone [120][121][122], withaferin A [123][124][125], and withanolide A [126][127][128][129][130] and other compounds as well as the synergistic action of multiple compounds present in Withania somnifera extract could contribute towards beneficial effect of Withania somnifera in the pathogenesis of neurodegenerative diseases.…”

Effect of Withanolide A on 7-Ketocholesterol Induced Cytotoxicity in hCMEC/D3 Brain Endothelial Cells

“…Withanolide A increases glutathione biosynthesis in neuronal cells in a corticosteronedependent manner [23]. Profiling of withanolide A for therapeutic targets in neurodegenerative diseases has shown that withanolide A forms several contacts with residues in the glucocorticoid binding pocket but lacks key stabilizing interactions as observed for dexamethasone [45]. More studies are therefore needed to elucidate the possible mechanisms of action of withanolide A, on the glucocorticoid receptor.…”