Competitive inhibition of the high-affinity choline transporter by tetrahydropyrimidine anthelmintics

Functional characterization of Clonorchis sinensis choline transporter

Clonorchis sinensis is commonly found in East Asian countries. Clonorchiasis is prevalent in these countries and can lead to various clinical symptoms. In this study, we used overlap extension polymerase chain reaction (PCR) and the Xenopus laevis oocyte expression system to isolate a cDNA encoding the choline transporter of C. sinensis (CsChT). We subsequently characterized recombinant CsChT. Expression of CsChT in X. laevis oocytes enabled efficient transport of radiolabeled choline, with no detectable uptake of arginine, α-ketoglutarate, p-aminohippurate, taurocholate, and estrone sulfate. Influx and efflux experiments showed that CsChT-mediated choline uptake was time- and sodium-dependent, with no exchange properties. Concentration-dependent analyses of revealed saturable kinetics consistent with the Michaelis-Menten equation, while nonlinear regression analyses revealed a Km value of 8.3 μM and a Vmax of 61.0 pmol/oocyte/h. These findings contribute to widen our understanding of CsChT transport properties and the cascade of choline metabolisms within C. sinensis.

Polygoni Multiflori Radix Praeparata and Acori Tatarinowii Rhizoma ameliorate scopolamine-induced cognitive impairment by regulating the cholinergic and synaptic associated proteins

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Polygoni Multiflori Radix Praeparata (PMRP) and Acori Tatarinowii Rhizoma (ATR) is often used in traditional Chinese medicine to prevent and treat Alzheimer's disease (AD). However, it is not clear whether the effects and mechanisms of the decoction prepared by traditional decocting method (PA) is different from that prepared by modern decocting method (P + A).

AIM OF THE STUDY

The present study aimed to investigate the differences in the protective effects of PA and P + A on scopolamine induced cognitive impairment, and to explore its potential mechanism.

MATERIALS AND METHODS

To assess the protective effect of PA and P + A on cognitive dysfunction, the mice were orally administrated with PA (1.56, 6.24 g kg^-1•day^-1) and P + A (1.56, 6.24 g kg^-1•day^-1) for 26 days before co-treatment with scopolamine (4 mg kg^-1•day^-1, i.p.). The learning and memory abilities of mice were examined by Morris water maze test, and the expressions of proteins related to cholinergic system and synaptic function were detected by the methods of ELISA, real-time PCR and Western blotting. Then, molecular docking technique was used to verify the effect of active compounds in plasma after PA administration on Acetylcholinesterase (AChE) protein. Finally, the Ellman method was used to evaluate the effects of different concentrations of PA, P + A (1 μg/mL-100 mg/mL) and the compounds (1-100 μM) on AChE activity in vitro.

RESULTS

On one hand, in the scopolamine-induced cognitive impairment mouse model, both of PA and P + A could improve the cognitive impairment, while the effect of PA on cognitive amelioration was better than that of P + A. Moreover, PA regulated the cholinergic and synaptic functions by enhancing the concentration of acetylcholine (ACh), the mRNA levels of CHT1, Syn, GAP-43 and PSD-95, and the related proteins (CHT1, VACHT, Syn, GAP-43 and PSD-95), and significantly inhibiting the expression of AChE protein. Meanwhile, P + A only up-regulated the mRNA levels of GAP-43 and PSD-95, increased the expressions of CHT1, VACHT, Syn, GAP-43 and PSD-95 proteins, and inhibited the expression of AChE protein. On the other hand, the in vitro study showed that some compounds including emodin-8-o-β-d-Glucopyranoside, THSG and α-Asarone inhibited AChE protein activity with the IC₅₀ values 3.65 μM, 5.42 μM and 9.43 μM, respectively.

CONCLUSIONS

These findings demonstrate that both of PA and P + A can ameliorate the cognitive deficits by enhancing cholinergic and synaptic related proteins, while PA has the stronger improvement effect on the cholinergic function, which may be attributed to the compounds including THSG, emodin, emodin-8-O-β-D-glucopyranoside and α-asarone. The present study indicated that PA has more therapeutic potential in the treatment of neurodegenerative diseases such as AD. The results provide the experimental basis for the clinical use of PA.

Amyloid Beta Dynamics in Biological Fluids-Therapeutic Impact

Despite the significant impact of Alzheimer's disease (AD) at individual and socioeconomic levels and the numerous research studies carried out on this topic over the last decades, the treatments available in daily clinical practice remain less than satisfactory. Among the accepted etiopathogenic hypotheses, the amyloidogenic pathway theory, although intensively studied and even sometimes controversial, is still providing relevant theoretical elements for understanding the etiology of AD and for the further development of possible therapeutic tools. In this sense, this review aims to offer new insights related to beta amyloid (Aβ), an essential biomarker in AD. First the structure and function of Aβ in normal and pathological conditions are presented in detail, followed by a discussion on the dynamics of Aβ at the level of different biological compartments. There is focus on Aβ elimination modalities at central nervous system (CNS) level, and clearance via the blood-brain barrier seems to play a crucial/dominant role. Finally, different theoretical and already-applied therapeutic approaches for CNS Aβ elimination are presented, including the recent "peripheral sink therapeutic strategy" and "cerebrospinal fluid sinks therapeutic strategy". These data outline the need for a multidisciplinary approach designed to deliver a solution to stimulate Aβ clearance in more direct ways, including from the cerebrospinal fluid level.