Effects of (-)stepholidine in animal models for schizophrenia

Alternative Therapy of Psychosis: Potential Phytochemicals and Drug Targets in the Management of Schizophrenia

Schizophrenia is a chronic mental and behavioral disorder characterized by clusters of symptoms including hallucinations, delusions, disorganized thoughts and social withdrawal. It is mainly contributed by defects in dopamine, glutamate, cholinergic and serotonergic pathways, genetic and environmental factors, prenatal infections, oxidative stress, immune system activation and inflammation. Management of schizophrenia is usually carried out with typical and atypical antipsychotics, but it yields modest benefits with a diversity of side effects. Therefore, the current study was designed to determine the phytochemicals as new drug candidates for treatment and management of schizophrenia. These phytochemicals alter and affect neurotransmission, cell signaling pathways, endocannabinoid receptors, neuro-inflammation, activation of immune system and status of oxidative stress. Phytochemicals exhibiting anti-schizophrenic activity are mostly flavonoids, polyphenols, alkaloids, terpenoids, terpenes, polypropanoids, lactones and glycosides. However, well-designed clinical trials are consequently required to investigate potential protective effect and therapeutic benefits of these phytochemicals against schizophrenia.

Significantly different effects of tetrahydroberberrubine enantiomers on dopamine D1/D2 receptors revealed by experimental study and integrated in silico simulation

Tetrahydroberberrubine (TU), an active tetrahydroprotoberberines (THPBs), is gaining increasing popularity as a potential candidate for treatment of anxiety and depression. One of its two enantiomers, l-TU, has been reported to be an antagonist of both D1 and D2 receptors, but the functional activity of the other enantiomer, d-TU, is still unknown. In this study, experiments were combined with in silico molecular simulations to (1) confirm and discover the functional activities of l-TU and d-TU, and (2) systematically evaluate the molecular mechanisms beyond the experimental observations. l-TU proved to be an antagonist of both D1 and D2 receptors (IC50 = 385 nM and 985 nM, respectively), while d-TU shows no affinity against either D1 or D2 receptor, based on the cAMP assay (D1 receptor) and calcium flux assay (D2 receptor). Results from both flexible-ligand docking studies and molecular dynamic (MD) simulations provided insights at the atomic level. The l-TU-bound structures predicted by MD (1) undergo an outward rotation of the extracellular helical bundles; (2) have an enlarged orthosteric binding pocket; and (3) have a central toggle switch that is prevented from rotating freely. These features are unique to the l-TU enantiomer and provide an explanation for its antagonistic behavior toward both D1 and D2 receptors. The present study provides new sight on the structural and functional relationships of l-TU and d-TU binding to dopamine receptors, and provides guidance to the rational design of novel molecules targeting these two dopamine receptors in the future.

Chinese Herbal Medicine for the Treatment of Drug Addiction

This chapter summarizes recent developments in preclinical and clinical research on Chinese herbal medicines and their neurochemical mechanism of action for the treatment of drug addiction. We searched Chinese and English scientific literature and selected several kinds of Chinese herbal medicines that have beneficial effects on drug addiction. Ginseng (Renshen) may be clinically useful for the prevention of opioid abuse and dependence. Rhizoma Corydalis (Yanhusuo) may be used to prevent relapse to chronic drug dependence. Alkaloids of Uncaria rhynchophylla (Gouteng) appear to have positive effects on methamphetamine and ketamine addiction. Both Salvia miltiorrhiza (Danshen) and Radix Pueraiae (Gegen) have beneficial inhibitory effects on alcohol intake. Sinomenine has been shown to have preventive and curative effects on opioid dependence. l-Stepholidine, an alkaloid extract of the Chinese herb Stephania intermedia (Rulan), attenuated the acquisition, maintenance, and reacquisition of morphine-induced conditioned place preference and antagonized the heroin-induced reinstatement of heroin seeking. Traditional Chinese herbal medicines may be used to complement current treatments for drug addiction, including withdrawal and relapse. As the molecular mechanisms of action of traditional Chinese herbal medicines are elucidated, further advances in their use for the treatment of drug addiction are promising.

Levo-Tetrahydroberberrubine Produces Anxiolytic-Like Effects in Mice through the 5-HT1A Receptor

Tetrahydroprotoberberines (THPBs) are isoquinoline alkaloids isolated from the Chinese herb Corydalis yanhusuo. In the present study, we performed competitive binding assays to examine the binding of l-THBr to neurotransmitter receptors known to be involved in sedation, hypnosis and anxiety. Our results show that l-THBr does not interact with GABAergic receptors but has binding affinities for dopamine and serotonin receptors. In addition, cAMP and [³⁵S]GTPγS assays were used to determine the agonist or antagonist properties of l-THBr at dopamine (D₁, D₂) or serotonin (5-HT) receptors. Our results show that l-THBr displays D₁ and D₂ antagonist and 5-HT_1A agonist properties. Moreover, l-THBr-treated rodents exhibit anxiolytic-like effects in the light/dark box and elevated plus-maze tests, and the anxiolytic effect of l-THBr can be reduced by WAY-100635, a selective 5-HT_1A receptor antagonist. Our results suggest that l-THBr may produce potent anxiolytic-like effects mainly through serotonin receptors.

Synthesis and evaluation of C9 alkoxy analogues of (-)-stepholidine as dopamine receptor ligands

Tetrahydroprotoberberine alkaloids have shown interesting polypharmacological actions at dopamine receptors and are a unique template from which to mine novel molecules with dual selective actions at D1 and D3 receptors. Such compounds will be valuable to evaluate as anti-cocaine therapeutics. Towards that eventual goal, we engaged an SAR study in which a series of C9 alkoxy analogues of the D1/D2/D3 ligand (-)-stepholidine that possessed or lacked a C12 bromo functionality, were synthesized and evaluated for affinity at dopamine D1, D2 and D3 receptors. We found that the analogues are generally selective for the D1 receptor. Small n-alkoxy substituents (up to 4 carbons in length) were generally well tolerated for high D1 affinity but such groups reduced D3 affinity. In the case of C12 brominated analogues, C9 alkoxylation also had little effect on D1 affinity for the smaller alkoxy groups, but reduced D2 and D3 affinities significantly. C12 bromination tends to increase D1 receptor selectivity. A number of compounds were identified that retain affinity for D1 and D3 receptors but lack D2 receptor affinity. Among them, compound 22a was found to be a selective D1/D3 dual antagonist (Ki = 5.3 and 106 nM at D1 and D3 receptors). Docking studies performed on the analogues at the D3 receptor revealed a number of interactions that are important for affinity including a critical N - Asp110 salt bridge motif, H-bonds to Ser192 and Cys181 and hydrophobic interactions between the aryl rings and Phe106 and Phe345. The analogues adopt an orientation in which ring A is located in the orthosteric binding site while the C9 alkoxy substituents attached to ring D project into the secondary binding pocket of the D3 receptor.

(-)-Stepholidine is a potent pan-dopamine receptor antagonist of both G protein- and β-arrestin-mediated signaling

RATIONALE

(-)-Stepholidine is a tetrahydroberberine alkaloid that is known to interact with dopamine receptors and has also been proposed as a novel antipsychotic agent. Its suggested novelty lies in the fact that it has been proposed to have D1-like receptor agonist and D2-like receptor antagonist properties. Thus, it might be effective in treating both positive and negative (cognition) symptoms of schizophrenia. However, its activity on specific dopamine receptor subtypes has not been clarified, especially with respect to its ability to activate D1-like receptors.

OBJECTIVES

We wished to examine the affinity and functional activity of (-)-stepholidine at each of the human dopamine receptor subtypes expressed in a defined cellular environment.

METHODS

D1-D5 dopamine receptors were stably expressed in cell lines and their interactions with (-)-stepholidine were examined using radioligand binding and various functional signaling assays. Radioligand binding assays were also performed using bovine striatal membranes.

RESULTS

(-)-Stepholidine exhibited high (nM) affinity for D1 and D5 receptors, somewhat lower (two- to four-fold) affinity for D2 and D3 receptors, and low micromolar affinity for D4 receptors. Functionally, (-)-stepholidine was ineffective in activating G protein-mediated signaling of D1-like and D2 receptors and was also ineffective in stimulating β-arrestin recruitment to any dopamine receptor subtype. It did, however, antagonize all of these responses. It also antagonized D1-D2 heteromer-mediated Ca(2+) mobilization. Radioligand binding assays of D1-like receptors in brain membranes also indicated that (-)-stepholidine binds to the D1 receptor with antagonist-like properties.

CONCLUSIONS

(-)-Stepholidine is a pan-dopamine receptor antagonist and its in vivo effects are largely mediated through dopamine receptor blockade with potential cross-talk to other receptors or signaling proteins.

Ethnobotany, phytochemistry and pharmacology of Stephania rotunda Lour

ETHNOPHARMACOLOGICAL RELEVANCE

Stephania rotunda Lour. (Menispermaceae) is an important traditional medicinal plant that is grown in Southeast Asia. The stems, leaves, and tubers have been used in the Cambodian, Lao, Indian and Vietnamese folk medicine systems for years to treat a wide range of ailments, including asthma, headache, fever, and diarrhoea.

AIM OF THE REVIEW

To provide an up-to-date, comprehensive overview and analysis of the ethnobotany, phytochemistry, and pharmacology of Stephania rotunda for its potential benefits in human health, as well as to assess the scientific evidence of traditional use and provide a basis for future research directions.

MATERIAL AND METHODS

Peer-reviewed articles on Stephania rotunda were acquired via an electronic search of the major scientific databases (Pubmed, Google Scholar, and ScienceDirect). Data were collected from scientific journals, theses, and books.

RESULTS

The traditional uses of Stephania rotunda were recorded in countries throughout Southeast Asia (Cambodia, Vietnam, Laos, and India). Different parts of Stephania rotunda were used in traditional medicine to treat about twenty health disorders. Phytochemical analyses identified forty alkaloids. The roots primarily contain l-tetrahydropalmatine (l-THP), whereas the tubers contain cepharanthine and xylopinine. Furthermore, the chemical composition differs from one region to another and according to the harvest period. The alkaloids exhibited approximately ten different pharmacological activities. The main pharmacological activities of Stephania rotunda alkaloids are antiplasmodial, anticancer, and immunomodulatory effects. Sinomenine, cepharanthine, and l-stepholidine are the most promising components and have been tested in humans. The pharmacokinetic parameters have been studied for seven compounds, including the three most promising compounds. The toxicity has been evaluated for liriodenine, roemerine, cycleanine, l-tetrahydropalmatine, and oxostephanine.

CONCLUSION

Stephania rotunda is traditionally used for the treatment of a wide range of ailments. Pharmacological investigations have validated different uses of Stephania rotunda in folk medicine. The present review highlights the three most promising compounds of Stephania rotunda, which could constitute potential leads in various medicinal fields, including malaria and cancer.

The genus Stephania (Menispermaceae): chemical and pharmacological perspectives

The plants of the genus Stephania (Menispermaceae) are widely distributed, and have long been used in folk medicine for the treatment of various ailments such as asthma, tuberculosis, dysentery, hyperglycemia, malaria, cancer and fever. Over 150 alkaloids together with flavonoids, lignans, steroids, terpenoids and coumarins have been identified in the genus, and many of these have been evaluated for biological activity. This review presents comprehensive information on the chemistry and pharmacology of the genus together with the traditional uses of many of its plants. In addition, this review discusses the structure-activity relationship of different compounds as well as recent developments and the scope for future research in this aspect.

Brain targeting of risperidone-loaded solid lipid nanoparticles by intranasal route

Intranasal drug delivery is known to overcome the blood-brain barrier (BBB) for delivery of drugs to brain. The objective of this study was to prepare risperidone (RSP)-loaded solid lipid nanoparticles (RSLNs) and explore the possibility of brain targeting by nose-to-brain delivery. RSLNs were prepared by solvent emulsification-solvent evaporation method and characterized for drug content, particle size and size distribution, zeta potential, and in vitro drug-release study. The pharmacodynamic study of RSLNs, which was performed by paw test using Perspex platform, showed higher hindlimb retraction time (HRT) values as compared with RSP solution (RS) indicating the superiority of RSLNs over the RS for brain targeting. The pharmacokinetics and biodistribution studies in mice showed that brain/blood ratio 1 h post-administration of RSLNs (i.n.) was found to be 1.36 ± 0.06 (nearly 10- and 5-fold higher) as compared with 0.17 ± 0.05 for RS (i.v.) and 0.78 ± 0.07 for RSLNs (i.v.), respectively. Gamma scintigraphy imaging of mice brain following intravenous and intranasal administration confirmed the localization of drug in brain. This finding substantiates the existence of direct nose-to-brain delivery route for nanoparticles administered to the nasal cavity.

Evaluation of the antipsychotic effect of bi-acetylated l-stepholidine (l-SPD-A), a novel dopamine and serotonin receptor dual ligand

Bi-acetylated l-stepholidine (l-SPD-A), a novel derivate of l-stepholidine (l-SPD), possesses a pharmacological profile of D(1)/5-HT(1A) agonism and D(2) antagonism. In the present study, we examined the potential antipsychotic effect of l-SPD-A in a phencyclidine (PCP)-induced rat model of schizophrenia. Pretreatment with l-SPD-A blocked acute PCP-induced hyperlocomotion and reversed prepulse inhibition (PPI) deficits. Chronic l-SPD-A administration (i.p., 10mg/kg/day for 14 days) improved social interaction and novel object recognition impairments in rats that were pretreated with PCP (i.p., 5mg/kg/day for 14 days). Moreover, in a conditioned avoidance response (CAR) test, l-SPD-A, with either i.p. or oral administration, significantly decreased active avoidance without affecting the escape response of rats. Importantly, compared to that of the parent compound l-SPD, l-SPD-A showed stronger suppression of CARs. Lastly, using a [(35)S]GTPgammaS binding assay, we demonstrated that l-SPD-A improved impaired dopamine D(1) receptor function in the prefrontal cortex (PFC) in chronic PCP-treated rats. Taken together, these results indicate that l-SPD-A was not only effective against the hyperactivity, but also improved the sensorimotor gating deficit, social withdrawal and cognitive impairment in an animal model of schizophrenia. The present data suggest that l-SPD-A, a potential neurotransmitter stabilizer, is a promising novel candidate drug for the treatment of schizophrenia.

Oral bioavailability and brain penetration of (-)-stepholidine, a tetrahydroprotoberberine agonist at dopamine D(1) and antagonist at D(2) receptors, in rats

BACKGROUND AND PURPOSE

(-)-Stepholidine has high affinity for dopamine D(1) and D(2) receptors. The aims of the present study were to examine the oral bioavailability and brain penetration of (-)-stepholidine and to gain understanding of mechanisms governing its transport across the enterohepatic barrier and the blood-brain barrier.

EXPERIMENTAL APPROACH

The pharmacokinetics of (-)-stepholidine was studied in rats and microdialysis was used to measure delivery to the brain. These studies were supported by biological measurement of unbound (-)-stepholidine. Membrane permeability was assessed using Caco-2 cell monolayers. Metabolite profiling of (-)-stepholidine in rat bile and plasma was performed. Finally, in vitro metabolic stability and metabolite profile of (-)-stepholidine were examined to compare species similarities and differences between rats and humans.

KEY RESULTS

Orally administered (-)-stepholidine was rapidly absorbed from the gastrointestinal tract; two plasma concentration peaks were seen, and the second peak might result from enterohepatic circulation. Due to extensive pre-systemic metabolism, the oral bioavailability of (-)-stepholidine was poor (<2%). However, the compound was extensively transported across the blood-brain barrier, demonstrating an AUC (area under concentration-time curve) ratio of brain : plasma of approximately 0.7. (-)-Stepholidine showed good membrane permeability that was unaffected by P-glycoprotein and multidrug resistance-associated protein 2. In vitro (-)-stepholidine was metabolized predominantly by glucuronidation and sulphation in rats and humans, but oxidation of this substrate was very low.

CONCLUSIONS AND IMPLICATIONS

Although (-)-stepholidine exhibits good brain penetration, future development efforts should aim at improving its oral bioavailability by protecting against pre-systemic glucuronidation or sulphation. In this regard, prodrug approaches may be useful.

Berberine against gastrointestinal peptides elevation and mucous secretion in hyperthyroid diarrheic rats

To investigate the underlying mechanisms of Berberine-mediated antidiarrheal effects in thyroid hormone-induced diarrhea in rats, gastrointestinal peptides, such as motilin, gastrin, vasoactive intestinal peptide, and somatostatin from plasma and tissue of hyperthyroid diarrheic rats were measured using radioimmunoassay in healthy control, model, and treated model groups. The number and volume of goblet cells were also observed. Compared with healthy control, hyperthyroid diarrheic rats exhibited a significant reduction in body weight, and increase in plasma concentrations of tri-iodothyronine and free thyroxine along with the increase of wet stool. Both plasma motilin and gastrin were also elevated and reduced remarkably in Berberine-treated subgroup along with the body weight increased and wet stool reduced at the meantime. Significant changes in plasma vasoactive intestinal peptide and somatostatin were not seen. Gastrointestinal peptides trend in tissue samples were similar to those observed in plasma. Morphological data demonstrated an increase in number and/or volume of goblet cells to some extent in duodenum, jejunum, ileum, and colon, respectively and decreased by administration of Berberine. The possible underlying mechanisms of antidiarrheal effects of Berberine may be due in partially to the reduction of the number of goblet cells and the amount of mucous secretion through re-balancing gastrointestinal peptides.

Mucoadhesive nanoemulsion-based intranasal drug delivery system of olanzapine for brain targeting

The objective of the present study was to optimize olanzapine nanoemulsion (ONE), for nose-to-brain delivery. The nanoemulsions and olanzapine mucoadhesive nanoemulsions (OMNEs) were prepared using water titration method and characterized for technical and electrokinetic properties. Biodistribution of nanoemulsions and olanzapine solution (OS) in the brain and blood of rats following intranasal (intranasal) and intravenous (intravenous) administrations were examined using optimized technetium-labeled ((99m)Tc-labeled) olanzapine formulations. The brain/blood uptake ratios of 0.45, 0.88, 0.80, and 0.04 of OS (intranasal), ONE (intranasal), OMNE (intranasal), ONE (intravenous), respectively, at 0.5 h are indicative of direct nose-to-brain transport (DTP). Higher % drug targeting efficiency (%DTE) and %DTP for mucoadhesive nanoemulsions indicated effective brain targeting of olanzapine among the prepared nanoemulsions. Gamma scintigraphy imaging of the rat brain conclusively demonstrated rapid and larger extent of transport of olanzapine by OMNE (intranasal), when compared with OS (intranasal), ONE (intranasal), and ONE (intravenous), into the rat brain.

The antipsychotic potential of l-stepholidine--a naturally occurring dopamine receptor D1 agonist and D2 antagonist

RATIONALE

l-Stepholidine, a dopamine D(2) antagonist with D(1) agonist activity, should in theory control psychosis and treat cognitive symptoms by enhancing cortical dopamine transmission. Though several articles describe its impact on the dopamine system, it has not been systematically evaluated and compared to available antipsychotics.

MATERIALS AND METHODS

We examined its in vitro interaction with dopamine D(2) and D(1) receptors and compared its in vivo pharmacokinetic profile to haloperidol (typical) and clozapine (atypical) in animal models predictive of antipsychotic activity.

RESULTS

In vitro, l-stepholidine showed significant activity on dopamine receptors, and in vivo, l-stepholidine demonstrated a dose-dependent striatal receptor occupancy (RO) at D(1) and D(2) receptors (D(1) 9-77%, 0.3-30 mg/kg; D(2) 44-94%, 1-30 mg/kg), though it showed a rather rapid decline of D(2) occupancy related to its quick elimination. In tests of antipsychotic efficacy, it was effective in reducing amphetamine- and phencyclidine-induced locomotion as well as conditioned avoidance response, whereas catalepsy and prolactin elevation, the main side effects, appeared only at high D(2)RO (>80%). This preferential therapeutic profile was supported by a preferential immediate early gene (Fos) induction in the nucleus accumbens over dorsolateral striatum. We confirmed its D(1) agonism in vitro, and then using D(2) receptor, knockout mice showed that l-stepholidine shows D(1) agonism in the therapeutic dose range.

CONCLUSIONS

Thus, l-stepholidine shows efficacy like an "atypical" antipsychotic in traditional animal models predictive of antipsychotic activity and shows in vitro and in vivo D(1) agonism, and, if its rapid elimination does not limit its actions, it could provide a unique therapeutic approach to schizophrenia.

The neuropharmacology of (-)-stepholidine and its potential applications

(-)-Stepholidine (SPD), a natural product isolated from the Chinese herb Stephania, possesses dopamine (DA) D1 partial agonistic and D2 antagonistic properties in the nigrostriatal and mesocorticolimbic DAergic pathways. These unique dual effects have suggested that SPD can effectively restore previously imbalanced functional linkage between D1 and D2 receptors under schizophrenic conditions, in which, SPD improves both the negative and positive symptoms of schizophrenia. SPD also relieves the motor symptoms of Parkinson's disease (PD) when co-administered with Levodopa. Furthermore, SPD exhibits neuroprotective effects through an antioxidative mechanism and slows down the progression of neuronal degeneration in the substantia nigra (SN) of PD patients and/or animal models. Therefore, SPD is a novel, natural compound with potentially therapeutic roles in the treatment of schizophrenia and/or PD.

Levo-tetrahydropalmatine inhibits cocaine's rewarding effects: experiments with self-administration and brain-stimulation reward in rats

It was recently reported that levo-tetrahydropalmatine (l-THP), a dopamine (DA) D1 and D2 receptor antagonist purified from the Chinese herb Stephanie, appears to be effective in attenuating cocaine self-administration, cocaine-triggered reinstatement and cocaine-induced conditioned place preference in preclinical animal models. The present study was designed to contrast l-THP's effects on cocaine self-administration under fixed-ratio (FR) and progressive-ratio (PR) reinforcement, and to study l-THP's effects on cocaine-enhanced brain stimulation reward (BSR). Systemic administration of l-THP produced dose-dependent, biphasic effects, i.e., low-to-moderate doses (1, 3, 10 mg/kg) increased, while a high dose (20 mg/kg) inhibited cocaine self-administration behavior under FR2 reinforcement. The increased cocaine self-administration is likely a compensatory response to a reduction in cocaine's rewarding effects, because the same low doses of l-THP dose-dependently attenuated cocaine self-administration under PR reinforcement and also attenuated cocaine-enhanced BSR. These attenuations of PR cocaine self-administration and cocaine-enhanced BSR are unlikely due to l-THP-induced sedation or locomotor inhibition, because only 10 mg/kg, but not 1-3 mg/kg, of l-THP inhibited locomotion, sucrose self-administration and asymptotic operant performance in the BSR paradigm. In vivo microdialysis demonstrated that l-THP slightly elevates extracellular nucleus accumbens DA by itself, but dose-dependently potentiates cocaine-augmented DA, suggesting that a postsynaptic, rather than presynaptic, DA receptor antagonism underlies l-THP's actions on cocaine reward. Together, the present data, combined with previous findings, support the potential use of l-THP for treatment of cocaine addiction.

Effects of (-)-stepholidine on NMDA receptors: comparison with haloperidol and clozapine

AIM

To examine whether (-)-stepholidine (SPD) has a direct effect on the N-methyl- D-aspartic acid receptors (NMDAR) containing the NMDA receptor subunits NR2A or NR2B and to compare its effect with those of haloperidol (Hal) and clozapine (Cloz).

METHODS

NMDAR was transiently expressed in human embryonic kidney 293 (HEK293) cells. Changes in intracellular calcium concentration ([Ca2+]i) induced by NMDAR activation were monitored with Fura-2 ratio imaging techniques.

RESULTS

SPD had no significant effects on either subunit of NMDAR at a concentration of less than 100 micromol/L. Hal selectively inhibited NMDAR containing the NR2B subunit, whereas Cloz inhibited both subunits of NMDAR. Although both Hal and Cloz inhibited NR1a/NR2B receptor-mediated Ca2+ influx, their effects were different. Hal was more potent and had a faster peak effect than Cloz.

CONCLUSION

Both Hal and Cloz inhibit NMDAR-mediated function, whereas SPD produced only a little inhibition at a high concentration. Based on our other studies, the modulation of SPD on NMDAR function may be via D1 receptor action underlying an indirect mechanism.