Geissoschizine methyl ether

Neuroscience. 2012 Apr 5;207:124-36.

Geissoschizine methyl ether, an alkaloid in Uncaria hook, is a potent serotonin ₁A receptor agonist and candidate for amelioration of aggressiveness and sociality by yokukansan.[Pubmed: 22314317 ]

METHODS AND RESULTS:
To find the candidate ingredients, we examined competitive binding assay and [(35)S] guanosine 5'-O-(3-thiotriphosphate) (GTPγS) binding assay of seven major alkaloids in UH using Chinese hamster ovary cells expressing 5-HT(1A) receptors artificially. Only Geissoschizine methyl ether (GM) among seven alkaloids potently bound to 5-HT(1A) receptors and acted as a partial agonist. This in vitro result on GM was further demonstrated in the socially isolated mice. As did YKS and UH, GM ameliorated the isolation-induced increased aggressiveness and decreased sociality, and the effect was counteracted by coadministration of WAY-100635.
CONCLUSIONS:
These lines of results suggest that GM in UH is potent 5-HT(1A) receptor agonist and a candidate for pharmacological effect of YKS on aggressiveness and sociality in socially isolated mice.

Eur J Pharmacol. 2002 May 31;444(3):183-9.

Geissoschizine methyl ether, an indole alkaloid extracted from Uncariae Ramulus et Uncus, is a potent vasorelaxant of isolated rat aorta.[Pubmed: 12063078]

METHODS AND RESULTS:
Effects of Geissoschizine methyl ether, an indole alkaloid isolated from the hook of Uncariae Ramulus et Uncus, on vascular responses were examined using isolated strips of rat aorta. Geissoschizine methyl ether (10(-7)-10(-4) M) relaxed norepinephrine (5x10(-8) M)-induced contraction in a dose-dependent manner. The potency (50% efficacy concentration, EC(50)=0.744 microM) was approximately 14 times greater than that (EC(50)=10.6 microM) of hirsutine, one of the indole alkaloids isolated from Uncariae Ramulus et Uncus that demonstrates a vasorelaxant effect by Ca(2+)-channel blocking. The vasorelaxant effect of Geissoschizine methyl ether found at the lower concentrations (10(-7)-3x10(-6) M) on the norepinephrine-induced contraction was abolished by pretreatment with N(G)-nitro-L-arginine (10(-4) M), an inhibitor of nitric oxide synthesis, or by denuding aortas of endothelium, while the effects at the higher concentrations (10(-5)-10(-4) M) were not completely prevented by either N(G)-nitro-L-arginine and deendothelialization. Furthermore, Geissoschizine methyl ether did not relax high K(+)-, Ca(2+)- and a Ca(2+)-channel agonist Bay K8644-induced contractions at the lower concentrations that markedly relaxed the norepinephrine-induced contractions, while the higher concentrations of Geissoschizine methyl ether relaxed the high K(+)-, Ca(2+)- and Bay K8644-induced contractions.
CONCLUSIONS:
These results suggest that the vasorelaxant effect of Geissoschizine methyl ether is composed of two different mechanisms: endothelial dependency with nitric oxide and endothelial independency with voltage-dependent Ca(2+)-channel blocking.

Eur J Pharmacol. 2011 Dec 5;671(1-3):79-86.

Geissoschizine methyl ether has third-generation antipsychotic-like actions at the dopamine and serotonin receptors.[Pubmed: 21951966 ]

METHODS AND RESULTS:
In the present assay, the efficacy and potency of known ligands of serotonin 5-HT(1A), 5-HT(2A), 5-HT(2C), 5-HT(7) and dopamine D(2L) receptors were comparable to those found in previous studies using a variety of readouts. The developed assay was also able to reproduce the partial agonist activity, the low intrinsic activity and the selective activation of aripiprazole at the dopamine D(2L) receptors. Under identical experimental conditions, Geissoschizine methyl ether (GM), a plant indole alkaloid, behaved as a partial agonist at the serotonin 5-HT(1A) receptor, a partial agonist/antagonist at the dopamine D(2L) receptor and an antagonist at the serotonin 5-HT(2A), 5-HT(2C) and 5-HT(7) receptors. Interestingly, GM showed a relatively low intrinsic activity and evoked a partial activation response in a subset of cells expressing the dopamine D(2L) receptor; both of these effects were similarly observed for aripiprazole.
CONCLUSIONS:
Although GM is far less potent at the dopamine receptor than aripiprazole at dopamine D(2L) receptors (EC(50)=4.4 μM for GM vs. EC(50)=56 nM for aripiprazole), GM and GM derivatives may comprise a new set of candidates for atypical antipsychotics.

Nat Prod Res. 2012;26(1):22-8.

Geissoschizine methyl ether, a corynanthean-type indole alkaloid from Uncaria rhynchophylla as a potential acetylcholinesterase inhibitor.[Pubmed: 21714741 ]

METHODS AND RESULTS:
Geissoschizine methyl ether (1), a newly discovered strong acetylcholinesterase (AChE) inhibitor, along with six weakly active alkaloids, vallesiachotamine (2), hisuteine (3), hirsutine (4), isorhynchophylline (5), cisocorynoxeine (6) and corynoxeine (7) have been isolated from Uncaria rhynchophylla. Geissoschizine methyl ether (1) inhibited 50% of AChE activity at concentrations of 3.7 ± 0.3 µg mL(-1) while the IC(50) value of physostigmine as a standard was 0.013 ± 0.002 µg mL(-1).
CONCLUSIONS:
The mode of AChE inhibition by 1 was reversible and non-competitive. In addition, molecular modelling was performed to explore the binding mode of inhibitor 1 at the active site of AChE.

J Ethnopharmacol. 2016 Jul 1;187:249-58.

Geissoschizine methyl ether protects oxidative stress-mediated cytotoxicity in neurons through the 'Neuronal Warburg Effect'.[Pubmed: 27114061]

The rate of production of reactive oxygen species (ROS) is determined by mitochondrial metabolic rate. In turn, excessive ROS damage mitochondrial function, which is linked to aging and neurodegenerative conditions. One possible path to prevent oxidative stress could be achieved by reducing mitochondrial respiration in favor of less efficient ATP production via glycolysis. Such a shift in energy metabolism is known as the 'Warburg effect'. Geissoschizine methyl ether (GM) is one of the active components responsible for the psychotropic effects of Yokukansan, an herbal preparation widely used in China and Japan. GM protects neurons from glutamate-induced oxidative cytotoxicity through regulating mitochondrial function and suppressing ROS generation. We investigated the protective mechanism of GM against glutamate-induced oxidative stress in neuronal cells.
METHODS AND RESULTS:
The current study was performed on primary neurons and HT22 cells, a hippocampus neuronal cell line. Cell viability was measured by Calcein AM assay. H2DCFDA staining was used for intracellular ROS measurement. GSH level was measured using the GSH-Glo™ luminescence-based assay. Mitochondrial respiration and glycolysis were measured by the Seahorse Bioscience XFe 96 Extracellular Flux Analyzer. Protein levels were analyzed by western blot analysis. GM prevented glutamate-induced cytotoxicity in an HT-22 neuronal cell line even with a 9-hour exposure delay. GM blocked glutamate-induced intracellular ROS accumulation through suppressing mitochondrial respiration. Further, we found that GM up-regulated glycolysis and the pentose-phosphate pathway, which is involved in the production of intracellular reducing agent, NADPH. In addition, GM protected primary cortical neurons from both glutamate and buthioninesulfoximine toxicity.
CONCLUSIONS:
GM prevents glutamate-induced oxidative damage through reducing mitochondrial respiration, which further suppresses ROS generation. In addition, GM up-regulates glycolysis which compensate for the energy depletion induced by mitochondrial respiration inhibition. Overall, our study is the first to report that GM protects neurons from oxidative toxicity by shifting energy metabolism from mitochondrial respiration to glycolysis.