Molecular Determinants of α3β4 Nicotinic Acetylcholine Receptors Inhibition by Triterpenoids

Multi-target regulatory mechanism of Yang Xin Tang - a traditional Chinese medicine against dementia

BACKGROUND

Yang Xin Tang (YXT) is a traditional Chinese herbal preparation which has been reported to improve cognitive function and memory in patients with dementia. As the underlying mechanism of action of YXT has not been elucidated, we examined the effects of YXT and its major herbal components in regulating gene transcription and molecular targets related to Alzheimer's disease (AD).

METHODS

Aqueous and ethanol extracts of YXT and selected herbal components were prepared and validated by standard methods. A series of biochemical and cellular assays were employed to assess the ability of the herbal extracts to inhibit acetylcholinesterase, reduce β-amyloid aggregation, stimulate the differentiation of neural progenitor cells, suppress cyclooxygenase, and protect neurons against β-amyloid or N-methyl-D-aspartate-induced cytotoxicity. The effects of YXT on multiple molecular targets were further corroborated by a panel of nine reporter gene assays.

RESULTS

Extracts of YXT and two of its constituent herbs, Poria cocos and Poria Sclerotium pararadicis, significantly inhibited β-amyloid aggregation and β-amyloid-induced cytotoxicity. A protective effect of the YXT extract was similarly observed against N-methyl-D-aspartate-induced cytotoxicity in primary neurons, and this activity was shared by extracts of Radix Astragali and Rhizoma Chuanxiong. Although the YXT extract was ineffective, extracts of Poria cocos, Poria Sclerotium pararadicis and Radix Polygalae inhibited acetylcholine esterase, with the latter also capable of upregulating choline acetyltransferase. YXT and its components significantly inhibited the activities of the pro-inflammatory cyclooxygenases. Additionally, extracts of YXT and several of its constituent herbs significantly stimulated the phosphorylation of extracellular signal-regulated kinases and cAMP-responsive element binding protein, two molecular targets involved in learning and memory, as well as in the regulation of neurogenesis.

CONCLUSIONS

Several constituents of YXT possess multiple regulatory effects on known therapeutic targets of AD that range from β-amyloid to acetylcholinesterase. The demonstrated neuroprotective and neurogenic actions of YXT lend credence to its use as an alternative medicine for treating AD.

Pharmacological profiles and therapeutic applications of pachymic acid (Review)

Poria cocos is a saprophytic fungus that grows in diverse species of Pinus. Its sclerotium, called fu-ling or hoelen, has been used in various traditional Chinese medicines and health foods for thousands of years, and in several modern proprietary traditional Chinese medicinal products. It has extensive clinical indications, including sedative, diuretic, and tonic effects. Pachymic acid (PA) is the main lanostane-type triterpenoid in Poria cocos. Evidence suggests that PA has various biological properties such as cytotoxic, anti-inflammatory, antihyperglycemic, antiviral, antibacterial, sedative-hypnotic, and anti-ischemia/reperfusion activities. Although considerable advancements have been made, some fundamental and intricate issues remain unclear, such as the underlying mechanisms of PA. The present study aimed to summarize the biological properties and therapeutic potential of PA. The biosynthetic, pharmacokinetic, and metabolic pathways of PA, and its underlying mechanisms were also comprehensively summarized.

Non-enzymatic formation of isoprene and 2-methyl-3-buten-2-ol (2-MBO) by manganese

It has been suggested that isoprene synthesis by isoprene synthase (IspS) proceeds via a substrate-assisted mechanism. The authors observed a non-enzymatic isoprene formation by Mn²⁺, which represents the basis of IspS enzyme reaction. Because IspS and many other terpene synthases require Mn²⁺ metal ions as cofactor, this study characterized the formation reaction for the first time. Metal ions including Mn²⁺ non-enzymatically produced both isoprene and 2-methyl-3-buten-2-ol (2-MBO) from dimethylallyl pyrophosphate (DMADP). Isoprene formation was most enhanced by Fe²⁺ and, to a lesser extent, by Mn²⁺ or Cu²⁺. Ni²⁺, Co²⁺, Mg²⁺, and Ba²⁺ exhibited a low activity to generate both isoprene and 2-MBO. The proportion of isoprene and 2-MBO varied with the Mn²⁺ concentration: isoprene predominated over 2-MBO at a higher Mn²⁺ concentration. Similarly, isoprene formation by Mn²⁺ increased exponentially as temperature increased with predominance of isoprene over 2-MBO at higher temperature. Both isoprene and 2-MBO formation was enhanced by acidic and neutral pH compared to alkaline conditions. Molecular dynamic simulation of DMADP suggested that the formation reaction is initiated by deprotonation of hydrogen on allyl terminal carbon by phosphate oxygen and generates carbocation and allyl anion intermediates. This is followed by quenching to produce isoprene or by hydroxyl addition to form 2-MBO. Thus, this study provided an insight into reaction mechanism of isoprene and 2-MBO biosynthesis and highlighted some parts of isoprene emission from terrestrial plants, which could be formed by non-enzymatic mechanism.

Identification and molecular study on the interaction of Schisandrin C with human 5-HT3A receptor

Schisandrin C (Sch C) is one of the main components of Schisandra chinensis (Schisandra). Since the olden times, Schisandra has been used as a traditional herbal medicine in Asia. Recent studies have shown that Schisandra is effective against irritable bowel syndrome (IBS) in an animal model and affects IBS through the 5-HT_3A pathway in the IBS rat model. However, there lacks fundamental research on the interaction of specific components of Schisandra with the 5-HT_3A receptor for the treatment of IBS. We hypothesized that a component of Schisandra binds to the 5-HT_3A receptor and identified Sch C via a screening work using two electrode-voltage clamps (TEVC). Thus, we aimed to elucidate the neuropharmacological actions between Sch C and the 5-HT_3A receptor at molecular and cellular levels. Co-treatment of Sch C with 5-HT inhibited I_5-HT in a reversible, concentrate-dependent, like-competition, and voltage-independent manner, and IC₅₀ values of Sch C. Besides, the main binding positions of Sch C were identified through 3D modeling and point mutation were V225A and V288Y on 5-HT_3A receptor. Thus, we suggest the potential of Sch C in treating IBS in a manner that suppresses excessive neuronal serotonin signaling in the synapse of sensory neurons and enterochromaffin (EC) cells. In conclusion, the results demonstrate the mechanism of interaction between Sch C and 5-HT_3A receptor and reveal Sch C as a novel antagonist.

Phytochemistry and Pharmacological Activities of Wolfiporia cocos (F.A. Wolf) Ryvarden & Gilb

Poria cocos is the dried sclerotium of Wolfiporia cocos (F.A. Wolf) Ryvarden & Gilb., which was the current accepted name and was formerly known as Macrohyporia cocos (Schwein.) I. Johans. & Ryvarden, Pachyma cocos (Schwein.) Fr., Poria cocos F.A. Wolf and Sclerotium cocos Schwein. It is one of the most important crude drugs in traditional Chinese medicine, with a wide range of applications in ameliorating phlegm and edema, relieving nephrosis and chronic gastritis and improving uneasiness of minds. Its extensive pharmacological effects have attracted considerable attention in recent years. However, there is no systematic review focusing on the chemical compounds and pharmacological activities of Poria cocos. Therefore, this review aimed to provide the latest information on the chemical compounds and pharmacological effects of Poria cocos, exploring the therapeutic potential of these compounds. We obtained the information of Poria cocos from electronic databases such as SCI finder, PubMed, Web of Science, CNKI, WanFang DATA and Google Scholar. Up to now, two main active ingredients, triterpenes and polysaccharides of Poria cocos, have been identified from Poria cocos. It has been reported that they have pharmacological effects on anti-tumor, anti-bacterial, anti-oxidant, anti-inflammatory, immunomodulation, and liver and kidney protection. The review summarizes the phytochemistry and pharmacological properties of Poria cocos, which suggest that researchers should focus on the development of new drugs about Poria cocos to make them exert greater therapeutic potential.

Targeted Screening Approach to Systematically Identify the Absorbed Effect Substances of Poria cocos in Vivo Using Ultrahigh Performance Liquid Chromatography Tandem Mass Spectrometry

Poria cocos are extensively used as nutritious food, dietary supplements, and oriental medicine in Asia. However, the effect substances are still not very clear. In this study, a targeted screening approach was developed to systematically identify absorbed constituents of Poria cocos in vivo using ultrahigh performance liquid chromatography tandem mass spectrometry combined with UNIFI software. First, incubation reactions in vitro with rat intestinal microflora and rat liver microsomes were conducted to sum up metabolic rules of main constituents. Second, the absorbed constituents in vivo were picked out and identified based on the results of metabolic study in vitro. Finally, the absorbed active constituents in the treatment of Alzheimer's disease were screened by targeted network pharmacology analysis. A total of 62 absorbed prototypes and 59 metabolites were identified and characterized in dosed plasma. Thirty potential active constituents were screened, and 86 drug-targets shared by absorbed constituents and Alzheimer's disease were discovered by targeted network pharmacology analysis. In general, this proposed targeted strategy comprehensively provides new insight for active ingredients of Poria cocos.