Potential clinical applications of Ashwagandha (Withania somnifera) in medicine and neuropsychiatry

INTRODUCTION

Ashwagandha (ASW) is the extract of the plant Withania somnifera. It is widely used in complementary, alternative, and integrative medicine (CAIM) but is little discussed in mainstream modern medical literature.

AREAS COVERED

We performed a review of potential pharmacotherapeutic properties of ASW. Studies were sourced from relevant online and offline databases. In animal models, ASW displays antioxidant activity. It has GABAergic and other neurotransmitter modulatory effects. It reduces apoptosis and promotes synaptic plasticity. It improves cognition and reverses induced cognitive deficits. It attenuates indices of stress. In human subjects, ASW enhances adaptogenesis in healthy adults. It modestly benefits generalized anxiety disorder and obsessive-compulsive disorder, and symptom severity in schizophrenia, substance use disorders, and attention deficit hyperactivity disorder. It improves sleep quality.

EXPERT OPINION

ASW may confer modest benefit in certain neuropsychiatric conditions. Its benefits may arise from induction of neuroplasticity, antioxidant and anti-inflammatory effects, and modulation of GABA and glutamate, as well as other neurotransmitters. The antioxidant and anti-inflammatory actions may also benefit neurodegenerative states. Reports of clinical benefit with ASW must be interpreted with caution, given the paucity of randomized clinical trials (RCTs). Greater methodological rigor is necessary before clinical recommendations on ASW can be confidently made.

Sodium-calcium exchanger isoform-3 targeted Withania somnifera (L.) Dunal therapeutic intervention ameliorates cognition in the 5xFAD mouse model of Alzheimer's disease

The third isoform of the Na+-Ca2+ exchanger (NCX3) is crucial for a physiological fine-tuning of the Ca2+ fluxes in excitable tissues. In this view, the NCX3 accounts for the aberrant Ca2+ influx seen during neuronal excitotoxicity, such as in Alzheimer's disease (AD). However, little is known about NCX3 regulation and functional properties. Withania somnifera (L.) Dunal (W. somnifera), a traditional indigenous plant widely recognized for having numerous medicinal values, was undertaken to determine its potential therapeutic benefit against aggregated Aβ1-42-induced NCX3 dysregulation and the thereof cognition impairment in 5xFAD mice. The undertaken sourced dried roots of authenticated W. somnifera physicochemical compositional tests satisfied standards of pharmacognostic quality, and further phytochemical analysis of the roots methanol extract revealed the roots constitute several antioxidants. Following an intra-gastric gavage administration of synthesized W. somnifera roots methanolic extract from postnatal day 30 (P30) to P75, in vivo cognitional studies and then neurochemical examinations of the NCX3 expression level, Aβ plaque deposition, and antioxidant activities in the AD-associated brain regions of 4-month-old 5xFAD mice suggests that the oxidative stress normalizing effects of W. somnifera constituents, operating on the NCX3, may have a therapeutic role in the improvement of cognition in AD.

M1 muscarinic receptor is a key target of neuroprotection, neuroregeneration and memory recovery by i-Extract from Withania somnifera

Memory loss is one of the most tragic symptoms of Alzheimer's disease. Our laboratory has recently demonstrated that 'i-Extract' of Ashwagandha (Withania somnifera) restores memory loss in scopolamine (SC)-induced mice. The prime target of i-Extract is obscure. We hypothesize that i-Extract may primarily target muscarinic subtype acetylcholine receptors that regulate memory processes. The present study elucidates key target(s) of i-Extract via cellular, biochemical, and molecular techniques in a relevant amnesia mouse model and primary hippocampal neuronal cultures. Wild type Swiss albino mice were fed i-Extract, and hippocampal cells from naïve mice were treated with i-Extract, followed by muscarinic antagonist (dicyclomine) and agonist (pilocarpine) treatments. We measured dendritic formation and growth by immunocytochemistry, kallikrein 8 (KLK8) mRNA by reverse transcription polymerase chain reaction (RT-PCR), and levels of KLK8 and microtubule-associated protein 2, c isoform (MAP2c) proteins by western blotting. We performed muscarinic receptor radioligand binding. i-Extract stimulated an increase in dendrite growth markers, KLK8 and MAP2. Scopolamine-mediated reduction was significantly reversed by i-Extract in mouse cerebral cortex and hippocampus. Our study identified muscarinic receptor as a key target of i-Extract, providing mechanistic evidence for its clinical application in neurodegenerative cognitive disorders.

Stachys sieboldii Extract Supplementation Attenuates Memory Deficits by Modulating BDNF-CREB and Its Downstream Molecules, in Animal Models of Memory Impairment

Cholinergic dysfunction, impaired brain-derived neurotrophic factor and cAMP response element binding protein (BDNF-CREB) signaling are one of the major pathological hallmarks of cognitive impairment. Therefore, improving cholinergic neurotransmission, and regulating the BDNF-CREB pathway by downregulating apoptosis genes is one strategy for inhibiting the etiology of dementia. This study evaluates the potential effects of Stachys sieboldii MIQ (SS) extract against cognitive dysfunction and its underlying mechanisms. SS supplementation for 33 days improved scopolamine-induced memory impairment symptoms in Morris water maze test and Y-maze test. SS reduced the acetylcholineesterase activity and significantly increase acetylcholine and cholineacetyltransferase activity in the brain. In the subsequent mechanism study, SS regulated the mRNA expression level of neuronal plasticity molecules such as (nerve growth factor) NGF, BDNF, CREB, and its downstream molecules such as Bcl-2 and Egr-1 by downregulating the neuronal apoptosis targets in both hippocampus and frontal cortex. Additionally, inward currents caused by SS in hippocampal CA1 neurons was partially blocked by the GABA receptor antagonist picrotoxin (50 μM), suggesting that SS acts on synaptic/extrasynaptic GABA_A receptors. These findings indicate that SS may function in a way that is similar to nootropic drugs by inhibiting cholinergic abnormalities, and neuronal apoptosis targets and ultimately increasing the expression of BDNF-CREB.

Effect of Withinia Somnifera and Shilajit on Alcohol Addiction in Mice

BACKGROUND

Alcohol addiction is a social problem leading to both loss of health and economic prosperity among addicted individuals. Common properties of anti-addictive compounds include anti-anxiety, anticonvulsants, anti-depressant, and nootropic actions primarily through modulation of gamma-aminobutyric acid (GABA) and serotonergic systems.

OBJECTIVE

Here, we screen ashwagandha and shilajit known ethnopharmacologically as nervine tonic and adaptogenic herbs for possible anti-addictive potential.

MATERIALS AND METHODS

Effect of ashwagandha churna and shilajit was measured on ethanol withdrawal anxiety using elevated plus maze. Role of ashwagandha and shilajit on chronic ethanol consumption (21 days) was measured using two bottle choice protocol of voluntary drinking. We also measured the effect of the above herbs on corticohippocampal GABA, dopamine, and serotonin levels.

RESULTS

Both ashwagandha and shilajit were found to reduce alcohol withdrawal anxiety in a dose-dependent manner. These herbs alone or in combination also decreased ethanol intake and increased water intake significantly after 21 days of chronic administration. Chronic administration of ashwagandha was found to significantly increase GABA and serotonin levels whereas shilajit altered cortico-hippocampal dopamine in mice.

CONCLUSION

These central nervous system active herbs alone or in combination reduced both alcohol dependence and withdrawal thus showing promising anti-addictive potential.

SUMMARY

Withinia Somnifera alone and in combination with Shilajeet prevented ethanol withdrawal and alcohol addiction Abbreviations used: GABA: Gama aminobutyric acid, CNS: Central Nervous System, CPP:Condition place preference, DA: Dopamine, 5-HT: 5-hydroxytryptamine, NMDA:N-methyl-D-aspartate.

Exploring neuroprotective potential of Withania somnifera phytochemicals by inhibition of GluN2B-containing NMDA receptors: An in silico study

N-methyl-d-aspartate receptors (NMDARs) mediated excitotoxicity has been implicated in multi-neurodegenerative diseases. Due to lack of efficacy and adverse effects of NMDA receptor antagonists, search for herbal remedies that may act as therapeutic agents is an active area of research to combat these diseases. Withania somnifera (WS) is being used for centuries as a nerve tonic and Nootropic agents. The present study targets the in silico evaluation of the neuroprotective efficacy of W. somnifera phytochemicals by inhibition of NMDA receptor-mediated excitotoxicity through allosteric inhibition of the GluN2B containing NMDARs. We predict Blood Brain Barrier (BBB) penetration, mutagenicity, drug-likeness and Human Intestinal Absorption properties of 25 WS phytochemicals. Further, molecular docking was performed to know whether these phytochemicals inhibit the GluN2B containing NMDARs or not. The results suggest that Anaferine, Beta-Sitosterol, Withaferin A, Withanolide A, Withanolide B and Withanolide D inhibit GluN2B containing NMDARs through allosteric mode similar to the well-known selective antagonist Ifenprodil. These phytochemicals have potential as an essentially useful oral drug to counter NMDARs mediated excitotoxicity and to treat multi-neurodegenerative diseases.

Phasic and tonic type A γ-Aminobutryic acid receptor mediated effect of Withania somnifera on mice hippocampal CA1 pyramidal Neurons

Background:

In Nepali and Indian system of traditional medicine, Withania somnifera (WS) is considered as a rejuvenative medicine to maintain physical and mental health and has also been shown to improve memory consolidation.

Objective:

In this study, a methanolic extract of WS (mWS) was applied on mice hippocampal CA1 neurons to identify the receptors activated by the WS.

Materials and Methods:

The whole cell patch clamp recordings were performed on CA1 pyramidal neurons from immature mice (7-20 postnatal days). The cells were voltage clamped at -60 mV. Extract of WS root were applied to identify the effect of mWS.

Results:

The application of mWS (400 ng/μl) induced remarkable inward currents (-158.1 ± 28.08 pA, n = 26) on the CA1 pyramidal neurons. These inward currents were not only reproducible but also concentration dependent. mWS-induced inward currents remained persistent in the presence of amino acid receptor blocking cocktail (AARBC) containing blockers for the ionotropic glutamate receptors, glycine receptors and voltage-gated Na⁺ channel (Control: -200.3 ± 55.42 pA, AARBC: -151.5 ± 40.58 pA, P > 0.05) suggesting that most of the responses by mWS are postsynaptic events. Interestingly, these inward currents were almost completely blocked by broad GABA_A receptor antagonist, bicuculline- 20 μM (BIC) (BIC: -1.46 ± 1.4 pA, P < 0.001), but only partially by synaptic GABA_A receptor blocker gabazine (1 μM) (GBZ: -18.26 ± 4.70 pA, P < 0.01).

Conclusion:

These results suggest that WS acts on synaptic/extrasynaptic GABA_A receptors and may play an important role in the process of memory and neuroprotection via activation of synaptic and extrasynaptic GABA_A receptors.

GABA-Mimetic Actions of Withania somnifera on Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Mice

The plant Withania somnifera (WS), also known as Ashwagandha, has been used widely in traditional medicine systems in India and Nepal (Ayurveda), and has been accepted to cure various ailments. In this study, the whole-cell patch clamp technique was performed to examine the mechanism of action of WS on the SG neurons of the Vc from mouse brainstem slices. In whole-cell patch clamp mode, methanol extract of Withania somnifera (mWS) induced short-lived and repeatable inward currents in all SG neurons tested (31.3±8.51 pA, n = 7) using a high chloride pipette solution. The mWS-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated Na + channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, AP5, an NMDA receptor antagonist and strychnine, a glycine receptor antagonist. The mWS induced currents were blocked by picrotoxin, a GABAA receptor antagonist. These results show that mWS has an inhibitory effects on SG neurons of the Vc through GABAA receptor-mediated activation of chloride ion channels, indicating that mWS contains compounds with sedative effects on the central nervous system. These results also suggest that mWS may be a potential target for modulating orofacial pain processing.