Gender differences in plasma pharmacokinetics and hepatic metabolism of geissoschizine methyl ether from Uncaria hook in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Geissoschizine methyl ether (GM), an indole alkaloid from Uncaria hook, is an active ingredient in the traditional Japanese Kampo medicine yokukansan, which is used to treat neurosis, insomnia, irritability, and night crying in children. AIM OF THE STUDY: Recent our pharmacokinetic studies suggested that there may be gender differences in the plasma concentrations of GM in rats, but not in humans. However, the details of this difference remain unverified. The purpose of this study was to clarify the reasons for the gender differences in rats. MATERIALS AND METHODS: GM plasma pharmacokinetics was compared in male and female rats orally administered yokukansan (4 g/kg). To confirm the involvement of cytochrome P450 (CYP) in GM liver metabolism, GM was incubated with male and female rat liver S9 fraction in the absence or presence of 1-aminobenzotriazole (a nonspecific CYP inhibitor). CYP isoforms involved in GM metabolism were estimated using recombinant rat CYP isoforms and anti-rat CYP antibodies. RESULTS: The maximum GM plasma concentrations were significantly higher in female than in male rats. When GM was incubated with rat liver S9 fractions, GM reduction was more striking in male S9 (69.3%) than that in female S9 (10.0%) and was completely blocked with nonspecific CYP inhibitor 1-aminobenzotriazole. Screening experiments using recombinant rat cytochrome P450 (CYP) isoforms showed that CYP1A1, CYP2C6, CYP2C11, CYP2D1, and CYP3A2 were involved in GM metabolism. Of these CYP isoforms, the use of anti-rat CYP antibodies indicated that male-dependent CYP2C11 and CYP3A2 were predominantly involved in the liver microsomal GM metabolism with gender differences. CONCLUSIONS: These results suggest that the cause of gender differences in plasma GM pharmacokinetics in rats is most likely because of male-dependent CYP2C11 and CYP3A2, and provide also useful information to further evaluate the pharmacological and toxicological effects in future. This study is the first to demonstrate that the gender differences in plasma GM pharmacokinetics in rats are caused by the gender-dependent metabolism of GM.

Lipidomics-based study on the neuroprotective effect of geissoschizine methyl ether against oxidative stress-induced cytotoxicity.

ETHNOPHARMACOLOGICAL RELEVANCE: Lipid homoeostasis is important for neurodevelopment, cell signaling and neurotransmission. Alteration of lipid metabolism has been demonstrated in many neurological disorders and neurodegenerative diseases. Geissoschizine methyl ether (GM) is an active alkaloid ingredient in the traditional Chinese medicine Uncaria hook. It has been shown that GM has strong potency in neuroprotective activity and GM reduces the production of reactive oxygen species by regulating glucose metabolism, which protects neurons against oxidative stress-induced cell death. However, it is unknown whether GM could regulate neuronal lipid metabolism during oxidative challenge. AIM OF THE STUDY: The current study aimed to explore whether GM regulates lipid metabolism in oxidative damaged neurons and to determine the underlying mechanism involved in this neuro-protection. MATERIALS AND METHODS: Using a glutamate-induced oxidative toxicity model in mouse hippocampal neuronal cell line (HT-22 cells), we investigated the effect of GM on glutamate-induced lipid peroxidation, lipotoxicity and mitochondrial dysfunction. In order to clarify the mechanism underlying the neuroprotection by GM, lipid metabolomics was performed to investigate whether GM prevent oxidative stress-induced lipid metabolism disruption. Furthermore, the expression of lipid metabolism-related genes was measured. RESULTS: The results show the protective effect of GM against oxidative stress through blocking glutamate-induced lipid peroxidation and lipotoxicity. Overall, lipidomics analysis revealed that glutamate treatment resulted in different extents of changes in a wide range of lipid classes such as fatty acids (FA), triacylglycerol (TG), sphingomyelin (SM), cardiolipin (CL), lysophosphatidylcholines (LPC). However, GM treatment can significantly reverse glutamate-induced lipids disorder to the homeostasis level. GM prevented the disruption of lipid metabolism by regulating the expression of lipid homeostasis related genes, which contributes to preserve mitochondrial function under oxidative damage. CONCLUSION: These findings clearly demonstrated a novel protective mechanism of GM against glutamate-induced oxidative toxicity in neurons via regulating lipid metabolism. GM may provide an effective approach for the prevention and treatment of oxidative damaged neurons.

Antiepileptic geissoschizine methyl ether is an inhibitor of multiple neuronal channels.

Geissoschizine methyl ether (GM) is an indole alkaloid isolated from Uncaria rhynchophyll (UR) that has been used for the treatment of epilepsy in traditional Chinese medicine. An early study in a glutamate-induced mouse seizure model demonstrated that GM was one of the active ingredients of UR. In this study, electrophysiological technique was used to explore the mechanism underlying the antiepileptic activity of GM. We first showed that GM (1-30 µmol/L) dose-dependently suppressed the spontaneous firing and prolonged the action potential duration in cultured mouse and rat hippocampal neurons. Given the pivotal roles of ion channels in regulating neuronal excitability, we then examined the effects of GM on both voltage-gated and ligand-gated channels in rat hippocampal neurons. We found that GM is an inhibitor of multiple neuronal channels: GM potently inhibited the voltage-gated sodium (NaV), calcium (CaV), and delayed rectifier potassium (IK) currents, and the ligand-gated nicotinic acetylcholine (nACh) currents with IC50 values in the range of 1.3-13.3 µmol/L. In contrast, GM had little effect on the voltage-gated transient outward potassium currents (IA) and four types of ligand-gated channels (γ-amino butyric acid (GABA), N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainite (AMPA/KA receptors)). The in vivo antiepileptic activity of GM was validated in two electricity-induced seizure models. In the maximal electroshock (MES)-induced mouse seizure model, oral administration of GM (50-100 mg/kg) dose-dependently suppressed generalized tonic-clonic seizures. In 6-Hz-induced mouse seizure model, oral administration of GM (100 mg/kg) reduced treatment-resistant seizures. Thus, we conclude that GM is a promising antiepileptic candidate that inhibits multiple neuronal channels.

LC-MS/MS detection of citrus unshiu peel-derived flavonoids in the plasma and brain after oral administration of yokukansankachimpihange in rats.

1. Yokukansankachimpihange (YKSCH), a Kampo formulation combining Citrus unshiu peel (CUP) and Pinellia tuber (PT) with yokukansan (YKS), has been recently used to treat the behavioral and psychological symptoms of dementia. Several flavonoids derived from CUP and PT reportedly exhibit psychopharmacological activity, but it remains unclear whether these flavonoids reach the brain after oral administration of YKSCH. 2. In this study, we first measured eight target flavonoids in the plasma and brain in rats orally administered YKSCH. Among these flavonoids, hesperidin, narirutin, nobiletin, and heptamethoxyflavone (HMF) were detected in the plasma, and nobiletin and HMF were detected in the brain. 3. Next, to clarify whether CUP and PT affect the pharmacokinetics of YKS ingredients in YKSCH, the plasma pharmacokinetics of geissoschizine methyl ether (GM) as a representative active ingredient in YKS was examined in rats orally administered YKSCH or YKS. There was no significant difference between the two groups, inferring that the pharmacokinetics of GM may not be affected by the two additional crude drugs. 4. Taken together, this study suggests that the CUP-derived flavonoids nobiletin and HMF may be responsible for the psychopharmacological effects of YKSCH in addition to YKS ingredients.

Serotonin Receptor Binding Characteristics of Geissoschizine Methyl Ether, an Indole Alkaloid in Uncaria Hook.

BACKGROUND: Geissoschizine methyl ether (GM) is one of the indole alkaloids in Uncaria hook, and an active ingredient of yokukansan (YKS) that improves behavioral and psychological symptoms of dementia (BPSD) in patients with several types of dementia. The pharmacological action of GM has been related to various serotonin (5-HT) receptor subtypes. OBJECTIVE: The aim of this article is to review the binding characteristics of GM to the 5-HT receptor subtypes in the brains using our own data and previous findings. METHOD: Competitive receptor-binding and agonist/antagonist activity assays for several 5-HT receptor subtypes were performed. Moreover, the articles describing pharmacokinetics and brain distribution of GM were searched in PubMed. RESULTS: GM bound the following 5-HT receptor subtypes: 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5- HT4, 5-HT5A, 5-HT6, and 5-HT7. Among these receptors, GM had partial agonistic activity for 5-HT1A receptors and antagonistic activity for 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT7 receptors. Also, GM was metabolized by various CYP isoforms, mainly CYP3A4. Parent/unchanged GM was detected in both the blood and brain of rats after oral administration of YKS. In the brains, GM was presumed to bind to 5- HT1A, 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT7 receptors on neuron-like large cells mainly in the frontal cortex. CONCLUSION: These results suggest that GM is a pharmacologically important alkaloid that regulates various serotonergic activities or functions by binding to multiple 5-HT receptor subtypes. Thus, this review provides recent 5-HT receptor-related evidence that GM is partly responsible for pharmacological effects of YKS.

Neuropharmacological efficacy of the traditional Japanese Kampo medicine yokukansan and its active ingredients.

Dementia is a progressive neurodegenerative disorder with cognitive dysfunction, and is often complicated by behavioral and psychological symptoms of dementia (BPSD) including excitement, aggression, and hallucinations. Typical and atypical antipsychotics are used for the treatment of BPSD, but induce adverse events. The traditional Japanese Kampo medicine yokukansan (YKS), which had been originated from the traditional Chinese medicine Yi-Gan-San, has been reported to improve BPSD without severe adverse effects. In the preclinical basic studies, there are over 70 research articles indicating the neuropharmacological efficacies of YKS. In this review, we first describe the neuropharmacological actions of YKS and its bioactive ingredients. Multiple potential actions for YKS were identified, which include effects on serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmissions as well as neuroprotection, anti-stress effect, promotion of neuroplasticity, and anti-inflammatory effect. Geissoschizine methyl ether (GM) in Uncaria hook and 18ß-glycyrrhetinic acid (GA) in Glycyrrhiza were responsible for several pharmacological actions of YKS. Subsequently, we describe the pharmacokinetics of GM and GA in rats. These ingredients were absorbed into the blood, crossed the blood-brain barrier, and reached the brain, in rats orally administered YKS. Moreover, autoradiography showed that [(3)H]GM predominantly distributed in the frontal cortex and [(3)H]GA in the hippocampus. Thus, YKS is a versatile herbal remedy with a variety of neuropharmacological effects, and may operate as a multicomponent drug including various active ingredients.

In vitro identification of human cytochrome P450 isoforms involved in the metabolism of Geissoschizine methyl ether, an active component of the traditional Japanese medicine Yokukansan.

1. Yokukansan (YKS) is a traditional Japanese medicine also called kampo, which has been used to treat neurosis, insomnia, and night crying and peevishness in children. Geissoschizine methyl ether (GM), a major indole alkaloid found in Uncaria hook, has been identified as a major active component of YKS with psychotropic effects. Recently, GM was reported to have a partial agonistic effect on serotonin 5-HT1A receptors. However, there is little published information on GM metabolism in humans, although several studies reported the blood kinetics of GM in rats and humans. In this study, we investigated the GM metabolic pathways and metabolizing enzymes in humans. 2. Using recombinant human cytochrome P450 (CYP) isoforms and polyclonal antibodies to CYP isoforms, we found that GM was metabolized into hydroxylated, dehydrogenated, hydroxylated+dehydrogenated, demethylated and water adduct forms by some CYP isoforms. 3. The relative activity factors in human liver microsomes were calculated to determine the relative contributions of individual CYP isoforms to GM metabolism in human liver microsomes (HLMs). We identified CYP3A4 as the CYP isoform primarily responsible for GM metabolism in human liver microsomes. 4. These findings provide an important basis for understanding the pharmacokinetics and pharmacodynamics of GM and YKS.

Medicinal uses, phytochemistry and pharmacology of the genus Uncaria.

ETHNOPHARMACOLOGICAL RELEVANCE: The genus Uncaria belongs to the family Rubiaceae, which mainly distributed in tropical regions, such as Southeast Asia, Africa and Southeast America. Their leaves and hooks have long been thought to have healing powers and are already being tested as a treatment for asthma, cancer, cirrhosis, diabetes, hypertension, stroke and rheumatism. The present review aims to provide systematically reorganized information on the ethnopharmacology, phytochemistry and pharmacology of the genus Uncaria to support for further therapeutic potential of this genus. To better understanding this genus, information on the stereo-chemistry and structure-activity relationships in indole alkaloids is also represented. MATERIAL AND METHODS: The literature study of this review is based on various databases search (SCIFinder, Science Direct, CNKI, Wiley online library, Spring Link, Web of Science, PubMed, Wanfang Data, Medalink, Google scholar, ACS, Tropicos, Council of Heads of Australasian Herbaria, The New York Botanical Garden, African Plants Database at Genera Botanical Garden, The Plant List and SEINet) and library search for Biological Abstract and some local books on ethnopharmacology. RESULTS: 19 species of the genus Uncaria are found to be important folk medicines in China, Malaysia, Phillippines, Africa and Southeast America, etc, and have been served for the treatment of asthma, rheumatism, hyperpyrexia, hypertension and headaches, etc. More than 200 compounds have been isolated from Uncaria, including indole alkaloids, triterpenes, flavonoids, phenols, phenylpropanoids, etc. As characteristic constituents, indole alkaloids have been considered as main efficacy component for hypertension, epilepsy, depressant, Parkinson's disease and Alzheimer's disease. In addition, pharmacokinetic and metabolism investigation reveal that the indole alkaloids are likely to be absorbed, metabolized and excreted at early time points. Moreover, the specific inhibition of CYP isozymes can regulate their hydroxylation metabolites at C-10 and C-11. CONCLUSION: Preliminary investigations on pharmacological properties of the Uncaria species have enlightened their efficacious remedy for hypertension, asthma, cancer, diabetes, rheumatism and neurodegenerative diseases. To ensure the safety and effectiveness in clinical application, research on bioactive compounds, pharmacological mechanisms and toxicity of the genus Uncaria as well as the stereo-chemistry and structure-activity relationships of indole alkaloids seem very important.

Specific binding and characteristics of geissoschizine methyl ether, an indole alkaloid of Uncaria Hook, in the rat brain.

ETHNOPHARMACOLOGICAL RELEVANCE: Geissoschizine methyl ether (GM) is an indole alkaloid that is a component of Uncaria Hook, and has been identified as the active component responsible for the anti-aggressive effects of the Uncaria Hook-containing traditional Japanese medicine, yokukansan. Recently, GM was shown to reach the brain by crossing the blood-brain barrier in rats following the oral administration of yokukansan. This finding suggested that there may be specific binding sites for GM in the brain. Here we show evidence that tritium-labeled GM ([(3)H]GM) binds specifically to several brain areas of rats. MATERIALS AND METHODS: Male rats were used. [(3)H]GM was synthesized from a demethylated derivative of GM. Specific binding sites of [(3)H]GM on brain sections were determined by quantitative autoradiography, and maximum binding densities (Bmax) and dissociation constants (Kd) were calculated. Several chemical compounds were used to clarify the molecules that recognize [(3)H]GM in the completion-binding assay. Emulsion microautoradiography was also performed to identify the cells that bind [(3)H]GM. RESULTS: Specific binding of [(3)H]GM was observed in the frontal cortex, including the prefrontal cortical region (e.g., prelimbic cortex (PrL)), hippocampus, caudate putamen, amygdala, central medial thalamic nucleus, dorsal raphe nucleus (DR), and cerebellum. Bmax ranged between 0.65 and 8.79pmol/mg tissue, and Kd was between 35.0 and 232.6nM. Specific binding with relatively high affinity (Kd less than 62nM) was dense in the frontal cortical region, moderate in the DR, and sparse in the cerebellum. The specific binding of [(3)H]GM in the PrL was significantly replaced by the serotonin 1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (DPAT), 5-HT2A receptor antagonist ketanserin, 5-HT2B receptor agonist BW 723C86, 5-HT2C receptor agonist RO60-0175, adrenergic α2A receptor antagonist yohimbine, L-type Ca(2+) channel blocker verapamil, and µ-opioid receptor antagonist naloxone. Similar results were obtained in the frontal cortex and DR, but not in the cerebellum. Microautoradiography revealed that [(3)H]GM signals were distributed throughout the frontal cortex, which included neuron-like large cells. CONCLUSION: These results demonstrate that specific binding sites for GM exist in rat brain tissue, and suggest that the pharmacological actions of GM are mainly associated with 5-HT receptors in the frontal cortex and DR. These results provide an insight into the neuropharmacology of GM and GM-containing herbal medicines.

Yokukansan and its ingredients as possible treatment options for schizophrenia.

Schizophrenia is a debilitating psychotic mental disorder that affects almost the entire range of human mental function. The devastating effect of the illness is usually long-lasting and requires lifelong treatment. Despite an evolved psychopharmacological understanding, the overall therapeutic effect of antipsychotics is still not satisfactory. The choice of proper medication presents a clinical dilemma between efficacy and safety. As a result, searching for comparable treatment options with safer profiles is very important. Yokukansan (TJ-54), also called yi-gan san in Chinese, is a traditional herbal medicine with evident therapeutic effect for neuropsychiatric disorders. There are several open-label clinical studies upholding the possibility of using yokukansan to treat schizophrenia or schizophrenia-like psychosis. Evidence from animal studies and neurobiology also sheds light on the antipsychotic implications of yokukansan and its ingredients. Nevertheless, correlations between the experimental environment and clinical settings may be complicated by a number of confounders. Clinical trials with more sophisticated designs are required to fill the gap between the experimental environment and clinical settings.