Nicotine and modafinil combination protects against the neurotoxicity induced by 3,4-Methylenedioxymethamphetamine in hippocampal neurons of male rats

Highlights

• Combination therapy creates stronger therapeutic effects than monotherapy.

• Nicotine and modafinil co-administration reduces MDMA-induced neurotoxicity.

• The protective effects are associated with inhibition of apoptosis.

Abstract

MDMA (3,4-Methylenedioxymethamphetamine) is a common recreational drug of abuse which causes neurodegeneration. Nicotine and modafinil provide antioxidant and neuroprotective properties and may be beneficial in the management of MDMA-induced neurotoxicity. The purpose of this study was to characterize how acute and chronic administration of nicotine and/or modafinil exert protective effects against the MDMA-induced impaired cognitive performance, oxidative stress, and neuronal loss. Adult male rats were divided into three groups, namely control, MDMA and treatment (modafinil and/or nicotine). MDMA (10 mg/kg) was administered intraperitoneally during a three-week schedule (two times/day for two consecutive days/week). The treated-groups were classified based on the acute or chronic status of treatment. In the groups which underwent acute treatments, nicotine (0.5 mg/kg) and/or modafinil (100 mg/kg) were injected just prior to the MDMA administration (acute nicotine (NA), acute modafinil (MA), and acute nicotine and modafinil (NMA)). In the rats which received chronic treatments, nicotine (0.5 mg/kg) and/or modafinil (100 mg/kg) were injected every day during the three week-schedule administration of MDMA (chronic nicotine (NC), chronic modafinil (MC), and chronic nicotine and modafinil (NMC)). Learning and memory performance, as well as avoidance response, were assessed by Morris water maze and Shuttle box, respectively. Our findings indicate enhanced learning and memory and avoidance response in the NMC group. By TUNEL test and Cresyl Violet staining we evaluated neuronal loss and apoptosis in the hippocampal CA1 and found increased neuronal viability in the NMC group. On the other hand, chronic administration of modafinil and nicotine significantly down-regulated the caspase 3 and up-regulated both BDNF and TrkB levels in the MDMA-received rats. The serum levels of glutathione peroxidase (GPx) and total antioxidant capacity (TAC) were evaluated and we found that the alterations of serum levels of GPx and TAC were considerably prevented in the NMC group. The overall results indicate that nicotine and modafinil co-administration rescued brain from MDMA-induced neurotoxicity. We suggest that nicotine and modafinil combination therapy could be considered as a possible treatment to reduce the neurological disorders induced by MDMA.

Introduction

The psychotropic drug MDMA (3,4-methylenedioxy-metamphetamine, Ecstasy), is a substituted amphetamine with euphoric properties, such as pleasant feelings, reduced anxiety and stress, lowered defensiveness and enhanced willingness to communicate. These effects probably lead to the growing use of MDMA among adolescent populations (DELAVARI et al., 2007; Perez et al., 2008). In addition to amphetamine-like effects, MDMA exhibits hallucinogenic-like properties(Simantov and Tauber, 1997). It also causes neurotoxicity and psychiatric disorders including anxiety, depression, and psychosis (Gouzoulis‐Mayfrank and Daumann, 2006; Schifano, 2000). A substantial body of evidence points to the neural degeneration and apoptosis following the consumption of MDMA in several parts of parietal cortex, insula, ventrolateral nucleus of thalamus, and cerebellum. Importantly, the most apoptotic changes have been observed in the striatum, hippocampus, and prefrontal cortex (PFC)(Schmued, 2003). Hippocampus is one of the important areas which is affected by MDMA, and lead into impairment of memory and disruption of neurogenesis(Capela et al., 2009; Van Petten, 2004). Additionally, MDMA could be the cause of accumulation of reactive oxygen species (ROS) and reduced levels of Glutathione in neurons (Montiel-Duarte et al., 2004).

In neurodegenerative disorders, production of oxidative stress is accompanied by disruption of neurotrophins and apoptosis homeostasis (Hampton and Orrenius, 1997; Levi‐Montalcini, 1987; Sata et al., 1997). Brain-derived neurotrophic factor (BDNF) is a member of neurotrophin family which affects the generation, differentiation, and viability of neurons as well as learning and memory (Chao et al., 2006; Levi‐Montalcini, 1987). via two receptors of tyrosin kinase receptor (trk) and neurotrophin receptor (p75ntr) (Arevalo and Wu, 2006).

Nicotine, as an addictive compound, binds to the neuronal nicotinic acetylcholine receptors (nAChRs) in the central nervous system (CNS). The nAChRs highly expressed in the hippocampus(Nakauchi et al., 2015), and play important role in the memory and learning (Francis et al., 1999; Piri et al., 2010). Normally, nAChRs are activated by endogenous acetylcholine (ACh). Repeated exposure to nicotine give rise to the modifications of dopamine (DA) and ACh pathways (Le Foll and Goldberg, 2009). Other studies have supported the permanent changes of behavior and synaptic activities following nicotine administration(Abreu-Villaça et al., 2005). In newborn rat model, nicotine reduced the expression of BDNF which causes brain functional alterations (Xiaoyu, 2015). However, it could act as an antioxidant and exerts neuroprotective properties (Newman et al., 2002). Previously, it has been reported that acute dose of nicotine decreased the expression of BDNF in hippocampus, while it’s chronic administration lead to the upregulation of BDNF (Kenny et al., 2000). Accordingly, frequent exposures to nicotine have beneficial effects on cholinergic markers and enhance memory (Fewell et al., 2001; Hernandez and Terry, 2005; Piri et al., 2012; Puma et al., 1999; Zarrindast et al., 2012).

Modafinil is a non-amphetamine medication which stimulates nervous system by inhibition of DA reuptake. This drug affects various GABAergic, glutamatergic, noradrenergic, serotoninergic, histaminergic and orexinergic systems (Raineri et al., 2015). As a treatment for stimulant addiction, modafinil is being investigated in order to its cognitive enhancing properties (Mereu et al., 2013). Clinical investigations have confirmed that modafinil improves symptoms in patients with psychiatric disorders such as major depression, bipolar disorder, schizophrenia, and attention- deficit/hyperactivity disorder (ADHD) (Pierre et al., 2007; Shuman et al., 2009). It has been also described that modafinil decreased the deficits of cognitive function in psychostimulant addicted individuals (Mereu et al., 2020). Experimental studies have exhibited the neuroprotective and antioxidant effects of modafinil in neurodegenerative diseases, but the exact mechanism has not been studied (Bibani et al., 2012; Xiao et al., 2004). Modafinil prevented increasing of pre-apoptotic bax gene, and reducing anti-apoptotic bcl-2 gene in the striatum of methamphetamine treated-rats (Raineri et al., 2012). Additionally, increased levels of BDNF have been induced in the hippocampal dentate gyrus by modafinil administration (Sahu et al., 2013). Current developments have gradually shifted from a focus on monotherapy to combined or multiple therapies to create stronger effects on treatment of different diseases (Amani et al., 2021; Poustchi et al., 2021). Considering that the protective effects of nicotine and modafinil co-administration have not been studied on MDMA-induced neurotoxicity in the hippocampus, thus, it seems that assessment of therapeutic potential of these drugs on destructive effects of MDMA can represent a step forward in the treatment of brain damage following the MDMA administration. Therefore, the purpose of the current study was to examine the effects of both acute or chronic administration of modafinil and/or nicotine administration in the MDMA-treated male rats along behavioral, molecular, and histological tests.