Efficacy of Cicuta virosa medicinal preparations against pentylenetetrazole-induced seizures

Highlights

• CV HMPs delayed the onset and reduced the duration of GTCS in acute seizure model.

• CV HMPs imparted persistent insensitivity against PTZ induced kindling.

• CV HMPs ameliorated behavioral impairment induced by chronic convulsant stimulus.

• CV HMPs strengthened the antioxidant defense mechanism to attenuate oxidative stress.

Abstract

Epileptic seizures are characterized by imbalanced inhibition-excitation cycle that triggers biochemical alterations responsible for jeopardized neuronal integrity. Conventional antiepileptic drugs (AEDs) have been the mainstay option for treatment and control; however, symptomatic control and potential to exacerbate the seizure condition calls for viable alternative to these chemical agents. In this context, natural product-based therapies have accrued great interest in recent years due to competent disease management potential and lower associated adversities. Cicuta virosa (CV) is one such herbal remedy that is used in traditional system of medicine against myriad of disorders including epilepsy. Homeopathic medicinal preparations (HMPs) of CV were assessed for their efficacy in pentylenetetrazole (PTZ)-induced acute and kindling models of epilepsy. CV HMPs increased the latency and reduced the duration of tonic-clonic phase in acute model while lowering the kindling score in the kindling model that signified their role in modulating GABAergic neurotransmission and potassium conductance. Kindling-induced impairment of cognition, memory, and motor coordination was ameliorated by the CV HMPs that substantiated their efficacy in imparting sustained neuronal fortification. Furthermore, biochemical evaluation showed attenuated oxidative stress load through reduced lipid peroxidation and strengthened free radical scavenging mechanism. Taken together, CV HMPs exhibited promising results in acute and kindling models and must be further assessed through molecular and epigenomic studies.

Introduction

Impacting nearly 70 million people worldwide, epilepsy represents a complex neurological scenario characterized by recurrent seizure episodes, increased vulnerability to physical trauma, and associated comorbidities [1], [2], [3], [4], [5], [6]. Progressive brain damage due to epileptic seizures disrupts the coherence of neuronal efflux [7], [8], [9], [10], [11] and elevates the brain oxidative stress load thereby upregulating the intracellular Ca²⁺ concentration [12], [13] and hence facilitating for unhindered seizure progression. This imparts a significant therapeutic relevance to the potential antioxidants in context of the treatment and control of epileptic seizures [1], [14].

Conventional antiepileptic drugs (AEDs) have been the primary option for treatment and control of epileptic seizures [11]. With around 20 AEDs licensed globally, these chemical agents have shown reasonable seizure suppression potential [15]. However, their action is primarily symptomatic and thus does not address the latent biochemical alterations associated with epileptogenesis [16]. Due to this, nearly 30% of the patients do not respond to these AEDs while many experience various side effects that range from mild and short-term behavioral alteration to more severe and long-term psychiatric abnormality [11] including the possibility of seizure exacerbation [17]. This makes it imperative to search for more viable therapeutic alternative. In this context, natural product-based agents and therapies, including herbal extracts and homeopathic formulations, have shown competent potential in controlling epileptic seizures without inducing significant side effects [1], [11], [18], [19], [20], [21] therefore paving the way forward.

Cicuta virosa (CV) in one such natural remedy that is used against myriad of disorders in traditional system of medicine [18]. It has been recognized as a therapeutic option against epileptic convulsions in Materia Medica by Adolf zur Lippe (1854), John Henry Clarke (1902), James Tyler Kent (1905), and Cyrus Maxwell Boger (1915). Cicuta virosa, belonging to Apiaceae family, has Cicutoxin as one of the major contents which can regulate potassium channel currents [22] that are known to have direct effects on neuronal excitability and indirect effects related to metabolism [23] besides facilitating for cell membrane repolarization and sustained neuronal output [24]. Owing to its natural origin and documented usage, CV can be a viable alternative to conventional AEDs like Topiramate and Retigabine that act through potassium channel regulation and are known to induce behavioral and psychiatric side effects like somnolence, vision alterations, cognitive decline, and anorexia [25], [26], [27], [28], [29], [30], [31], [32]. Such effects have also been observed in healthy subjects [33] and thus put into perspective the need for competent and safer option.

Wide application in the traditional system of medicine and documented literature motivated us to investigate the efficacy of Cicuta virosa homeopathic medicinal preparations (HMPs) in PTZ-induced acute and kindling seizure models, respectively. The acute seizure model is a widely accepted tool for the screening of anticonvulsant drugs while the kindling model closely resembles the progressive neurochemical alterations, i.e. compromised functioning of GABAergic and glutamatergic transmission system and induction of pro-oxidative and pro-inflammatory responses that affect the cortical network and limbic circuit, associated with epilepsy and thus provides reliable and predictable results [34], [35], [36], [37]. Here, we evaluated the efficacy of CV HMPs in PTZ-induced acute seizure model which was followed by the assessment of HMPs in PTZ-induced kindling model. Clonazepam and sodium valproate were used as reference drugs in acute and kindling models, respectively as the former facilitates for screening of drugs for anticonvulsant action through direct action on GABAergic neurotransmission [38], [39] while the latter, owing to its multipronged action on seizure propagation [40] and active regulation of epileptogenesis [41], provides a justified benchmark for the assessment of antiepileptogenic potential of CV. Three different potencies (6CH, 12CH, and 30CH) of the HMPs were used in the study and all the potencies were in Hahnemannian centesimal (CH) dilution. Kindling assessment of the HMPs was followed with the evaluation of their efficacy in negating PTZ-induced behavioral alterations through various validated behavioral screening tests. Five tests were performed in this study for the assessment of cognition impairment, recognition memory, anxiety and behavioral normalcy, motor coordination impairment, and spatial memory retention. Utilization of multiple behavioral screening tests in epilepsy studies for the assessment of various behavioral parameters has been reported previously [42], [43], [44], [45], [46], [47], [48]. The HMPs were then assessed for their effect on brain oxidative stress through the measurement of malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) levels. The present study provides a pharmacological basis to the use of CV in traditional system of medicine and adds up to the current knowledge about its neurochemical interaction in the brain.