Macelignan, a lignan from Myristica fragrans Houtt., rescues mitochondrial homeostasis and prevents cognitive decline in vascular dementia by modulating the mTOR-Mitophagy axis

Ethnopharmacological relevance: Myristica fragrans Houtt. has a long history of use in traditional medicine as a nervine tonic for enhancing cognitive function, relieving anxiety, and managing neurological symptoms associated with aging. Given its established ethnopharmacological profile, we postulated that its principal active lignan, Macelignan, could exert potent neuroprotective effects in the context of neurodegenerative diseases like vascular dementia (VaD).

Aim of the study: This study was designed to investigate the neuroprotective properties of Macelignan in a preclinical model of vascular dementia (VaD) and to elucidate the underlying molecular mechanisms, with a particular focus on its modulation of the mTOR signaling pathway and mitochondrial homeostasis.

Materials and methods: In this study, in vivo and in vitro models of ischemia-hypoxia were established in Wistar rats by bilateral common carotid artery occlusion (BCCAo) and in HT22 neuronal cells with cobalt chloride (CoCl₂) treatment, respectively. The resulting cognitive, pathological, and cell survival damages were comprehensively assessed using a battery of behavioral tests, histological staining (H&E and Nissl), and the CCK-8 assay. To elucidate the underlying mechanisms, we first predicted and validated the direct interaction between the drug and its core target protein using transcriptome Sequencing (RNA-seq) combined with molecular docking and dynamics simulations. Subsequently, changes in key signaling pathways, including mTOR, mitochondrial dynamics, Autophagy, and Apoptosis, were systematically investigated utilizing Seahorse metabolic flux analysis, transmission electron microscopy (TEM), various fluorescent probes (JC-1, MitoSOX, ROS, CA²⁺), Western blotting, and immunofluorescence (IF). All data were statistically analyzed using GraphPad Prism 10.1.2.

Results: In vivo, we demonstrate that Macelignan ameliorates neuronal damage and cognitive deficits in a model of vascular dementia by directly targeting and activating the mTOR signaling pathway. At the cellular level, this mTOR activation orchestrates a multifaceted protective response, which includes restoring mitochondrial function and homeostasis, enhancing antioxidant defenses, suppressing the stress-induced expression of mitophagy-related proteins Beclin-1 and Parkin, and potently inhibiting Apoptosis. Critically, these neuroprotective effects of Mace were completely abrogated by the mTORC1-specific inhibitor rapamycin, definitively establishing that its therapeutic efficacy is dependent on mTOR activation.

Conclusions: Macelignan targets and activates mTOR to restore mitochondrial homeostasis, thereby ameliorating vascular dementia.

Apoptosis; Macelignan; Mitochondrial homeostasis; Mitophagy; Vascular dementia; mTOR signaling axis.