Schisandrin enhances dendrite outgrowth and synaptogenesis in primary cultured hippocampal neurons

A comprehensive review on Schisandrin and its pharmacological features

Schisandrin stands as one of the primary active compounds within the widely used traditional medicinal plant Schisandra chinensis (Turcz.) Baill. This compound exhibits sedative, hypnotic, anti-aging, antioxidant, and immunomodulatory properties, showcasing its effectiveness across various liver diseases while maintaining a favorable safety profile. However, the bioavailability of schisandrin is largely affected by hepatic and intestinal first-pass metabolism, which limits the clinical efficacy of schisandrin. In this paper, we review the various pharmacological effects and related mechanisms of schisandrin, in order to provide reference for subsequent drug research and promote its medicinal value.

Schisandrin A and B enhance the dentate gyrus neurogenesis in mouse hippocampus

Schisandrin A and B (Sch A and B) are the main effective components of Schisandra chinensis (S. chinensis), which is traditionally used to enhance mental and intellectual functions in eastern Asia. Previously, we reported Sch A and B remarkably affect adult neurogenesis in the subventricular zone of mouse lateral ventricle. Since the neurogenesis in the hippocampal dentate gyrus (DG) is more important to learning, memory and cognition, here we further examined their effects on the adult DG neurogenesis. Phosphohistone H3 (PHH3) immunostaining showed that Sch B significantly enhanced the cell proliferation in the DG. Glial fibrillary acidic protein (GFAP, mostly labels astrocytes and some stem cells) staining was used to further identify the proliferating cell type. Dramatically, increases of GFAP⁺ cells in both Sch A and B treated groups were observed. What's more, the total numbers of the mature neurons labeled by neuron-specific nuclear protein (NeuN) were also increased in both Sch A and B treated groups compared with the controls. Together, Sch A and B enhance the adult DG neurogenesis by increasing astrocytes/stem cells and improving the survival and maturation of DG neurons. Our study shed a new light on the neuropharmacological functions of the herbal medicine S. chinensis.

Jowiseungchungtang Inhibits Amyloid-β Aggregation and Amyloid-β-Mediated Pathology in 5XFAD Mice

Alzheimer's disease (AD) is a neurodegenerative disease, which is accompanied by memory loss and cognitive dysfunction. Although a number of trials to treat AD are in progress, there are no drugs available that inhibit the progression of AD. As the aggregation of amyloid-β (Aβ) peptides in the brain is considered to be the major pathology of AD, inhibition of Aβ aggregation could be an effective strategy for AD treatment. Jowiseungchungtang (JWS) is a traditional oriental herbal formulation that has been shown to improve cognitive function in patients or animal models with dementia. However, there are no reports examining the effects of JWS on Aβ aggregation. Thus, we investigated whether JWS could protect against both Aβ aggregates and Aβ-mediated pathology such as neuroinflammation, neurodegeneration, and impaired adult neurogenesis in 5 five familial Alzheimer's disease mutations (5XFAD) mice, an animal model for AD. In an in vitro thioflavin T assay, JWS showed a remarkable anti-Aβ aggregation effect. Histochemical analysis indicated that JWS had inhibitory effects on Aβ aggregation, Aβ-induced pathologies, and improved adult hippocampal neurogenesis in vivo. Taken together, these results suggest the therapeutic possibility of JWS for AD targeting Aβ aggregation, Aβ-mediated neurodegeneration, and impaired adult hippocampal neurogenesis.

Platycodon grandiflorus Root Extract Improves Learning and Memory by Enhancing Synaptogenesis in Mice Hippocampus

Platycodon grandiflorus (Jacq.) A.DC. (PG) has long been used as an ingredient of foods and is known to have beneficial effects on cognitive functions as well. The present study examined the effect of each PG extract (PGE) from root, aerial part, and seeds on cognitive functions in mice. Changes in spatial learning and memory using a Y-maze test, and markers of adult hippocampal neurogenesis and synaptogenesis were examined. Moreover, changes in neuritogenesis and activation of the ERK1/2 pathway were investigated. Results indicated that mice administered PGE (root) showed increased spontaneous alternation in the Y-maze test and synaptogenesis in the hippocampus. In addition, PGE (root) and platycodin D, the major bioactive compound from the PG root, significantly stimulated neuritic outgrowth by phosphorylation of the ERK1/2 signaling pathway in vitro. These results indicate that the PGE (root), containing platycodin D, enhances cognitive function through synaptogenesis via activation of the ERK1/2 signaling pathway.

Undaria pinnatifida Promotes Spinogenesis and Synaptogenesis and Potentiates Functional Presynaptic Plasticity in Hippocampal Neurons

Reductions in neurotrophic factors are implicated in synaptic dysfunction in the central nervous system, but exogenous neurotrophic factors with potential effects on neuritic regeneration and synaptic reconstruction could offer therapeutic and preventive strategies for treating memory-related neurological disorders. In an earlier effort to identify natural neurotrophic agents, we found that the ethanol extract of the edible marine alga Undaria pinnatifida (UPE) had promising effects on the neuritogenesis of cultured hippocampal neurons. Here, we further investigated the ability of UPE to promote spinogenesis and synaptogenesis in primary cultures of hippocampal neurons. It was found that UPE triggered significant increase in numbers of dendritic filopodia and spines, promoted the formation of excitatory and inhibitory synapses, and potentiated synaptic transmission by increasing the sizes of reserve vesicle pools at presynaptic terminals. These findings indicate a substantial role for UPE in the morphological and functional maturation of neurons and suggest that UPE is a possible therapeutic preventative measure and treatment for neurodegenerative diseases, such as those involving cognitive disorders and memory impairments.

Effect of nigranoic acid on Ca²⁺ influx and its downstream signal mechanism in NGF-differentiated PC12 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra chinensis has a long history of use as a famous traditional Chinese medicine. The plants of genus Schisandra, especially Schisandra neglecta, Schisandra rubriflora, and Schisandra sphaerandra are used in the same way as Schisandra chinensis in the folk medicine to treat insomnia, fatigue, increasing intelligence, and tranquilizing. Many studies showed that lignans were the major active components of Schisandra genus, whereas the bioactivity of abundant triterpenoids in Schisandra genus, such as nigranoic acid (SBB1, 3,4-secocycloartene triterpenoid), has not been examined yet in neuropathology.

MATERIALS AND METHODS

After treating with SBB1, intracellular Ca(2+) concentration was analyzed by Ca(2+) fluorescent indicator (Fluo-4 AM) in NGF-differentiated PC12 cells. Intracellular nitric oxide (NO) level was analyzed using NO fluorescent indicator (DAF-FM). The expression of extracellular signal regulated kinase 1 and 2 (ERK1/2) was analyzed by western blotting, and the temporal mRNA for BDNF and c-fos was analyzed using reverse transcription quantitative PCR.

RESULT

We found that SBB1 induced Ca(2+) influx in a time- and concentration-dependent manner, which was significantly attenuated in Ca(2+) free media. SBB1 promoted the intracellular NO production which depended on increasing cytoplasmic Ca(2+) level. Moreover, SBB1 stimulated activation of ERK1/2 through Ca(2+)-CaMKII pathway. In addition, we found that SBB1 increased the expression of BDNF and c-fos mRNA.

CONCLUSION

These results suggest that SBB1 is able to promote NO production and stimulate phosphorylation of ERK1/2 through Ca(2+) influx, further impact expression of BDNF and c-fos, which provides evidence for the effects of SBB1 that may be benefit to enhance mental and intellectual functions.