An In Silico Study on Withania somnifera Bioactives and Curcumin Analogs as Potential Inducers of Smoothened (Smo) Receptor of Sonic Hedgehog (SHH) Pathway to Promote Oligodendrogenesis

Abstract

Demyelinating disorder is a subset of neurodegenerative conditions wherein factors such as aging and/or auto-immune attack cause damage and degradation of myelin sheath which enwraps the neuronal axons. Lowered axonal integrity and sub-par conduction of nerve impulses due to impaired action potentials make neurodegeneration imminent as the neurons do not have mitotic ability to replenish their numbers. Oligodendrocytes (OLs) myelinate the axonal segments of neurons and perform neuronal maintenance. Neuroregenerative stem cell therapy exploits this property for remyelination by targeting OL replenishment using in vitro stem cell differentiation protocols for inducing OL lineage cells. But some shortcomings of such protocols are over-reliance on synthetic inducers, lengthy differentiation process, low differentiation efficiency besides being financially expensive. This in silico study sought to identify herbal substitutes of currently available OL-lineage-specific synthetic inducers from a virtual library of curcumin analogs and Withania somnifera bioactives. Smoothened (Smo) receptor belonging to the canonical sonic hedgehog (SHH) signaling pathway promotes in vivo differentiation of OLs as well as their subsequent lineage progression to myelinating OLs. Therefore, we performed pharmacokinetics prediction for the bioactives followed by their molecular docking and molecular dynamics simulation with Smo. From a pool of 1289 curcumin analogs and 80 Withania somnifera-derived bioactives, the best docked ligands were identified as the compounds with PubChem IDs 68815167 and 25880, respectively. Molecular dynamics simulation of these ligands further concluded the Withania somnifera bioactive 25880 to have the best activity with Smo. This compound may be deemed as a potential lead molecule for an agonistic interaction with and activation of Smo to initialize its downstream signaling cascade for enriching OL differentiation.

Keywords: Withania somnifera bioactives; Curcumin analogs; Molecular docking; Molecular dynamics simulation; Oligodendrocytes; Smoothened receptor.