A Novel Anti-Parkinsonian Agent, Zonisamide, Attenuates MPTP-Induced Neurotoxicity in Mice

Trifluoromethylated Flavonoid-Based Isoxazoles as Antidiabetic and Anti-Obesity Agents: Synthesis, In Vitro α-Amylase Inhibitory Activity, Molecular Docking and Structure-Activity Relationship Analysis

Diabetes mellitus is a major health problem globally. The management of carbohydrate digestion provides an alternative treatment. Flavonoids constitute the largest group of polyphenolic compounds, produced by plants widely consumed as food and/or used for therapeutic purposes. As such, isoxazoles have attracted the attention of medicinal chemists by dint of their considerable bioactivity. Thus, the main goal of this work was to discover new hybrid molecules with properties of both flavonoids and isoxazoles in order to control carbohydrate digestion. Moreover, the trifluoromethyl group is a key entity in drug development, due to its strong lipophilicity and metabolic stability. Therefore, the present work describes the condensation of a previously synthesized trifluoromethylated flavonol with different aryl nitrile oxides, affording 13 hybrid molecules indicated as trifluoromethylated flavonoid-based isoxazoles. The structures of the obtained compounds were deduced from by ¹H NMR, ¹³C NMR, and HRMS analysis. The 15 newly synthesized compounds inhibited the activity of α-amylase with an efficacy ranging from 64.5 ± 0.7% to 94.7 ± 1.2% at a concentration of 50 μM, and with IC₅₀ values of 12.6 ± 0.2 μM-27.6 ± 1.1 μM. The most effective compounds in terms of efficacy and potency were 3b, 3h, 3j, and 3m. Among the new trifluoromethylated flavonoid-based isoxazoles, the compound 3b was the most effective inhibitor of α-amylase activity (PI = 94.7 ± 1.2% at 50 μM), with a potency (IC₅₀ = 12.6 ± 0.2 μM) similar to that of the positive control acarbose (IC₅₀ = 12.4 ± 0.1 μM). The study of the structure-activity relationship based on the molecular docking analysis showed a low binding energy, a correct mode of interaction in the active pocket of the target enzyme, and an ability to interact with the key residues of glycosidic cleavage (GLU-230 and ASP-206), explaining the inhibitory effects of α-amylase established by several derivatives.

Zonisamide for the Treatment of Parkinson Disease: A Current Update

Zonisamide has been used as an add-on treatment in order to overcome the deficiencies of the general therapies currently used to resolve the motor complications and non-motor symptoms of Parkinson disease. Various trials have been designed to investigate the mechanism of action and treatment effects of zonisamide in this condition. Most clinical trials of zonisamide in Parkinson disease were from Japan. The vast majority of studies used changes in the Unified Parkinson’s Disease Rating Scale (UPDRS) scores and daily “OFF” time as primary endpoints. Based on adequate randomized controlled trials, zonisamide is considered a safe and efficacious add-on treatment in Parkinson disease. The most convincing proof is available for a dosage of 25–50 mg, which was shown to lead to a significant reduction in the UPDRS III score and daily “OFF” time, without increasing disabling dyskinesia. Furthermore, zonisamide may play a beneficial role in improving non-motor symptoms in PD, including impulsive–compulsive disorder, rapid eye movement sleep behavior disorder, and dementia. Among the various mechanisms reported, inhibition of monoamine oxidase-B, blocking of T-type calcium channels, modulation of the levodopa–dopamine metabolism, modulation of receptor expression, and neuroprotection are the most often cited. The mechanisms underlying neuroprotection, including modulation of dopamine turnover, induction of neurotrophic factor expression, inhibition of oxidative stress and apoptosis, inhibition of neuroinflammation, modulation of synaptic transmission, and modulation of gene expression, have been most extensively studied. This review focuses on structure, pharmacokinetics, mechanisms, therapeutic effectiveness, and safety and tolerability of zonisamide in patients with Parkinson disease.

The effects of zonisamide on L-DOPA-induced dyskinesia in Parkinson's disease model mice

Parkinson's disease (PD) is a neurodegenerative disorder caused by the loss of dopaminergic neurons in the midbrain and shows motor dysfunctions. Zonisamide (ZNS, 1,2-benzisoxazole-3-methanesulfonamide), which was originally developed as an antiepileptic drug, was also found to have beneficial effects on motor symptoms in PD. In the current study, we have investigated the behavioral and physiological effects of ZNS on L-DOPA-induced dyskinesia (LID) in PD model mice. Chronic administration of L-DOPA plus ZNS in PD model mice was shown to increase the duration and severity of LID compared with PD model mice that were treated with L-DOPA alone. To elucidate the neural mechanism of the effects of ZNS on LID, we examined neuronal activity in the output nuclei of the basal ganglia, i.e., the substantia nigra pars reticulata (SNr). Chronic administration of L-DOPA plus ZNS in PD mice decreased the firing rate in the SNr while they showed apparent LID. In addition, chronic treatment of L-DOPA plus ZNS in PD mice changed cortically evoked responses in the SNr during LID. In the control state, motor cortical stimulation induces the triphasic response composed of early excitation, inhibition, and late excitation. In contrast, L-DOPA plus ZNS-treated PD mice showed longer inhibition and reduced late excitation. Previous studies proposed that inhibition in the SNr is derived from the direct pathway and releases movements, and that late excitation is derived from the indirect pathway and stops movements. These changes of the direct and indirect pathways possibly underlie the effects of ZNS on LID.

Zonisamide cotreatment delays striatal dopamine transporter reduction in Parkinson disease: A retrospective, observational cohort study

This study examined whether zonisamide (ZNS) cotreatment delays dopamine transporter (DAT) reduction on SPECT in Parkinson disease (PD) patients. The study participants met the following criteria: (i) age ≥ 40 years; (ii) HY stage = 2 or 3; (iii) average specific binding ratio (SBR) ≥2.00; (iv) levodopa administration without a prior history of ZNS use before the first DAT-SPECT (baseline). Attending physicians initially determined whether ZNS (25 mg/day) should be used or not. Levodopa and other anti-PD medications were not restricted. The second DAT-SPECT (endpoint) was conducted 1.2 ± 0.2 years after the first DAT-SPECT. Clinicoradiological changes of HY stage, UPDRS parts II to IV, dyskinesia subscore, and SBR were calculated. Statistical differences were analyzed by Student's t-test, ANOVA, or multilogistic analysis. ZNS cotreatment improved wearing off and prevented the development of dyskinesia without additional administration of selegiline, entacapone, and dopamine receptor agonists. The endpoint SBR reduced significantly in the non-ZNS group compared to the baseline (P < .01). The SBR decline rate reduced significantly in the ZNS group (P < .01). ZNS was an independent preventive factor for SBR reduction. These results suggested a beneficial potential that ZNS preserves striatal presynaptic DAT expression and slows disease progression in early-stage PD.

Zonisamide attenuates α-synuclein neurotoxicity by an aggregation-independent mechanism in a rat model of familial Parkinson's disease

The anti-epileptic agent zonisamide (ZNS) has been shown to exert protective effects in neurotoxin-based mouse models of Parkinson disease. However, it is unknown whether ZNS can attenuate toxicity of familial Parkinson's disease-causing gene products. In this study, we investigated the effects of ZNS on neurodegeneration induced by expression of A53T α-synuclein in the rat substantia nigra using a recombinant adeno-associated virus vector. Expression of A53T α-synuclein yielded severe loss of nigral dopamine neurons and striatal dopamine nerve terminals from 2 weeks to 4 weeks after viral injection. Oral administration of ZNS (40 mg/kg/day) significantly delayed the pace of degeneration at 4 weeks after viral injection as compared with the vehicle group. This effect lasted until 8 weeks after viral injection, the final point of observation. ZNS treatment had no impact on the survival of nigrostriatal dopamine neurons in rats expressing green fluorescent protein. Quantification of striatal Ser129-phosphorylated α-synuclein-positive aggregates showed that these aggregates rapidly formed from 2 weeks to 4 weeks after viral injection. This increase was closely correlated with loss of nigrostriatal dopamine neurons. However, ZNS treatment failed to alter the number of all striatal Ser129-phosphorylated α-synuclein-positive aggregates, including small dot-like and large round structures. The number of these aggregates was almost constant at 4 weeks and 8 weeks after viral injection, although ZNS persistently prevented loss of nigrostriatal dopamine neurons during this period. Also, ZNS treatment did not affect the number of striatal aggregates larger than 10 µm in diameter. These data show that ZNS attenuates α-synuclein-induced toxicity in a manner that is independent of the formation and maturation of α-synuclein aggregates in an in vivo model of familial Parkinson's disease, suggesting that ZNS may protect nigrostriatal dopamine neurons by modulating cellular damage or a cell death pathway commonly caused by neurotoxins and α-synuclein.

The changing landscape of voltage-gated calcium channels in neurovascular disorders and in neurodegenerative diseases

It is a common belief that voltage-gated calcium channels (VGCC) cannot carry toxic amounts of Ca²⁺ in neurons. Also, some of them as L-type channels are essential for Ca²⁺-dependent regulation of prosurvival gene-programs. However, a wealth of data show a beneficial effect of drugs acting on VGCCs in several neurodegenerative and neurovascular diseases. In the present review, we explore several mechanisms by which the “harmless” VGCCs may become “toxic” for neurons. These mechanisms could explain how, though usually required for neuronal survival, VGCCs may take part in neurodegeneration. We will present evidence showing that VGCCs can carry toxic Ca²⁺ when: a) their density or activity increases because of aging, chronic hypoxia or exposure to β-amyloid peptides or b) Ca²⁺-dependent action potentials carry high Ca²⁺ loads in pacemaker neurons. Besides, we will examine conditions in which VGCCs promote neuronal cell death without carrying excess Ca²⁺. This can happen, for instance, when they carry metal ions into the neuronal cytoplasm or when a pathological decrease in their activity weakens Ca²⁺-dependent prosurvival gene programs. Finally, we will explore the role of VGCCs in the control of nonneuronal cells that take part to neurodegeneration like those of the neurovascular unit or of microglia.

Zonisamide: a review of the clinical and experimental evidence for its use in Parkinson's disease

The limitations of currently available therapies in addressing the non motor symptoms of Parkinson's disease (PD) have egged on the search for newer options. Zonisamide has been in use for epilepsy and it was serendipitously found to improve the symptoms of PD in a patient who had both epilepsy and PD. Thereafter, various trials were designed to assess the use of zonisamide in PD. The present article investigates the evidence for use of zonisamide in PD from the various clinical trials that were designed to address this issue. Furthermore, the article also summarizes the various mechanisms of its use in PD as described in various animal experiments. A search protocol was designed with predefined inclusion and exclusion criteria. The databases searched were Pubmed, Ovid medline, Cochrane and clinicaltrials.gov. The data thus generated, was fed into a predesigned format. Most of the clinical trials on zonisamide in PD have come from Japan. Most of these trials used the changes in the Unified Parkinson's Disease Rating Scale (UPDRS) score as the endpoints and the most conclusive evidence is for a dose of 25-50 mg, which caused a change in UPDRS part III (motor symptoms). These patients were on levodopa and other drugs used for PD during the trials. One of the clinical trials conducted in Spain investigates the use of zonisamide in impulse control disorders among 15 patients of PD. Among the many mechanisms postulated, a reduction in levodopa induced quinone formation, protection against mitochondrial impairment and an increase in astroglial cysteine transport, an inhibition of microglial activation, monoamine oxidase-B (MAO-B) inhibition, an increased dopamine release and blockade of calcium channels are the most cited. There is evidence for use of zonisamide in PD in addition to levodopa and other therapies for control of motor symptoms. For now, the evidence for its use in control of non motor symptoms in PD is not enough and needs to be investigated further.

Zonisamide up-regulated the mRNAs encoding astrocytic anti-oxidative and neurotrophic factors

Zonisamide has been proven as an effective drug for the recovery of degenerating dopaminergic neurons in the animal models of Parkinson's disease. However, several lines of evidence have questioned the neuroprotective capacity of zonisamide in animal models of Parkinson's disease. Although it suppresses dopaminergic neurodegeneration in animal models, the cellular and molecular mechanisms underlying the effectiveness of zonisamide are not fully understood. The current study demonstrates the effects of zonisamide on astrocyte cultures and two 6-hydroxydopamine-induced models of Parkinson's disease. Using primary astrocyte cultures, we showed that zonisamide up-regulated the expression of mRNA encoding mesencephalic astrocyte-derived neurotrophic factor, vascular endothelial growth factor, proliferating cell nuclear antigen, metallothionein-2, copper/zinc superoxide dismutase, and manganese superoxide dismutase. Similar responses to zonisamide were found in substantia nigra where the rats were pre-treated with 6-hydroxydopamine. Notably, pharmacological inhibition of 6-hydroxydopamine-induced toxicity by zonisamide pre-treatment was also confirmed using rat mesencephalic organotypic slice cultures of substantia nigra. In addition to this, zonisamide post-treatment also attenuated the nigral tyrosine hydroxylase-positive neuronal loss induced by 6-hydroxydopamine. Taken together, these studies demonstrate that zonisamide protected dopamine neurons in two Parkinson's disease models through a novel mechanism, namely increasing the expression of some important astrocyte-mediated neurotrophic and anti-oxidative factors.

Changes of gene expression profiles in the cervical spinal cord by acupuncture in an MPTP-intoxicated mouse model: microarray analysis

It has been shown that acupuncture at acupoints GB34 and LR3 inhibits the degeneration of nigrostriatal neurons in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease. The degeneration of spinal cord was reported to be induced in the MPTP-treated pre-symptomatic mouse. In this study, the gene expression profile changes following acupuncture at the acupoints were investigated in the cervical spinal cord of an MPTP-induced parkinsonism model using a whole transcript array (Affymetrix GeneChip mouse gene 1.0 ST array). It was shown that 8 of the probes up-regulated in MPTP, as compared to the control, were down-regulated after acupuncture at the acupoints. Of these 8 probes, 6 probes (4 annotated genes in 6 probes: Ctla2a, EG383229, Ppbp and Ube2l6) were exclusively down-regulated by acupuncture at the specific acupoints except for 2 probes as these 2 probes were commonly down-regulated by acupuncture at both the acupoints and the non-acupoints. In addition, 11 of the probes down-regulated in MPTP, as compared to the control, were up-regulated by acupuncture at the acupoints. Of these 11 probes, 10 probes (5 annotated genes in 10 probes: EG665033, ENSMUSG00000055323, Obox6, Pbp2 and Tmem150) were exclusively up-regulated by acupuncture at the specific acupoints except for the Fut11 because the Fut11 was commonly up-regulated by acupuncture at both the acupoints and the non-acupoints. The expression levels of the representative genes in the microarray were validated by real-time RT-PCR. These data suggest that the expression of these exclusively regulated 16 probes (9 genes) may be, at least in part, affected by acupuncture at the acupoints in the cervical spinal cord which can be damaged by MPTP intoxication.

Zonisamide-induced long-lasting recovery of dopaminergic neurons from MPTP-toxicity

Zonisamide is an antiepileptic drug that also improves the cardinal symptoms of Parkinson's disease. This study investigated the effects of zonisamide on dopaminergic neuronal degeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. Six groups of mice were treated as follows: 1) normal saline; 2) MPTP, 15 mg/kg×4 every 2h; 3) MPTP and zonisamide, 40 mg/kg×1, 1h after the last MPTP dose; 4) MPTP and zonisamide, 1 day after the last dose of MPTP; 5) MPTP and zonisamide, 1h before the first MPTP dose; and 6) zonisamide, 40 mg/kg. MPTP-treatment decreased the contents of dopamine as well as the number and area of tyrosine hydroxylase (TH)-positive neurons. Concurrent treatment of mice with zonisamide and MPTP did not show any inhibition of the toxic effect of MPTP towards dopamine contents at 1 week after treatment but it increased the number and area of TH-positive neurons compared to the MPTP-treated group. Surviving TH-positive neurons had recovery of dopamine production after several weeks. Moreover, zonisamide increased the number of S100β-positive and glial fibrillary acidic protein (GFAP)-positive astrocytes and dopamine turnover. These results suggest that zonisamide acts as a neuro-protectant against MPTP-induced dopaminergic neuronal degeneration as shown by an increase of TH-positive neurons and this may be mediated by increased S100β secretion.

Neuroprotective properties of mildronate, a small molecule, in a rat model of Parkinson's disease

Previously, we have found that mildronate [3-(2,2,2-trimethylhydrazinium) propionate dihydrate], a small molecule with charged nitrogen and oxygen atoms, protects mitochondrial metabolism that is altered by inhibitors of complex I and has neuroprotective effects in an azidothymidine-neurotoxicity mouse model. In the present study, we investigated the effects of mildronate in a rat model of Parkinson's disease (PD) that was generated via a unilateral intrastriatal injection of the neurotoxin 6-hydroxydopamine (6-OHDA). We assessed the expression of cell biomarkers that are involved in signaling cascades and provide neural and glial integration: the neuronal marker TH (tyrosine hydroxylase); ubiquitin (a regulatory peptide involved in the ubiquitin-proteasome degradation system); Notch-3 (a marker of progenitor cells); IBA-1 (a marker of microglial cells); glial fibrillary acidic protein, GFAP (a marker of astrocytes); and inducible nitric oxide synthase, iNOS (a marker of inflammation). The data show that in the 6-OHDA-lesioned striatum, mildronate completely prevented the loss of TH, stimulated Notch-3 expression and decreased the expression of ubiquitin, GFAP and iNOS. These results provide evidence for the ability of mildronate to control the expression of an array of cellular proteins and, thus, impart multi-faceted homeostatic mechanisms in neurons and glial cells in a rat model of PD. We suggest that the use of mildronate provides a protective effect during the early stages of PD that can delay or halt the progression of this neurodegenerative disease.

Therapeutic effect of a novel anti-parkinsonian agent zonisamide against MPTP (1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine) neurotoxicity in mice

We investigated the therapeutic effect of zonisamide against 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice, using Western blot analysis, immunohistochemistry and behavioral test. Our Western blot analysis and immunohistochemical study showed that the post-treatment with zonisamide prevented significantly dopaminergic cell damage, the depletion of tyrosine-hydroxylase (TH) protein levels and the proliferation of microglia in the striatum and/or substantia nigra 8 days after MPTP treatment. Furthermore, our behavioral study showed that the post-treatment with zonisamide attenuated significantly the motor deficits 7 days after MPTP treatment. These results show that zonisamide has the therapeutic effect in the MPTP model of Parkinson's disease (PD) in mice. Our study also demonstrates the neuroprotective effect of zonisamide against dopaminergic cell damage after MPTP treatment in mice. Thus our present findings suggest that therapeutic strategies targeted to the activation of TH protein and/or the inhibition of microglial activation with zonisamide may offer a great potential for restoring the functional capacity of the surviving dopaminergic neurons in individuals affected with PD.

Zonisamide reduces cell death in SH-SY5Y cells via an anti-apoptotic effect and by upregulating MnSOD

Zonisamide, originally known as an antiepileptic drug, has been approved in Japan as adjunctive therapy with levodopa for the treatment of Parkinson's disease (PD). Although zonisamide reduces neurotoxicity, the precise mechanism of this action is not known. Here, we show that zonisamide increases cell viability in SH-SY5Y cells via an anti-apoptotic effect and by upregulating levels of manganese superoxide dismutase (MnSOD). These results would give us novel evidences of PD treatment.

Therapeutic effect of a novel anti-parkinsonian agent zonisamide against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in mice

We investigated the therapeutic effect of zonisamide against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice, using Western blot analysis, immunohistochemistry and behavioral test. Our Western blot analysis and immunohistochemical study showed that the post-treatment with zonisamide prevented significantly dopaminergic cell damage, the depletion of tyrosine-hydroxylase (TH) protein levels and the proliferation of microglia in the striatum and/or substantia nigra 8 days after MPTP treatment. Furthermore, our behavioral study showed that the post-treatment with zonisamide attenuated significantly the motor deficits 7 days after MPTP treatment. These results show that zonisamide has the therapeutic effect in the MPTP model of Parkinson's disease (PD) in mice. Our study also demonstrates the neuroprotective effect of zonisamide against dopaminergic cell damage after MPTP treatment in mice. Thus our present findings suggest that therapeutic strategies targeted to the activation of TH protein and/or the inhibition of microglial activation with zonisamide may offer a great potential for restoring the functional capacity of the surviving dopaminergic neurons in individuals affected with PD.

Zonisamide: aspects in neuroprotection

Zonisamide is widely used as an antiepileptic drug. Two studies published recently in Experimental Neurology focus on the drug's neuroprotective effect. In the present commentary, we discuss the significance of their findings and aspects of zonisamide in neuroprotection.

Zonisamide: in Parkinson's disease

Zonisamide, a widely available antiepileptic drug, has been approved in Japan as adjunctive therapy with levodopa for the treatment of previously treated patients with Parkinson's disease. It is an oral 1,2-benzisoxazole-3-methanesulfonamide and is associated with increased striatal dopamine levels in animal models. In two 12-week, randomized, double-blind, multicentre trials in adult patients with inadequately controlled Parkinson's disease and receiving levodopa, zonisamide 25 mg once daily (the recommended dosage) significantly improved motor function from baseline at final assessment, as assessed by the Unified Parkinson's Disease Rating Scale (UPDRS) Part III total score (primary endpoint), compared with placebo. Zonisamide 25 mg once daily as adjunctive therapy with levodopa was generally well tolerated by patients with Parkinson's disease. The overall incidence of adverse events was not significantly different between zonisamide 25 mg once daily and placebo groups in the phase IIb/III trial.