Riluzole suppresses motor cortex facilitation in correlation to its plasma level

The aim of our study was to measure the effects of the glutamate antagonist riluzole on different parameters of motor excitability, using transcranial magnetic stimulation (TMS) during 7 days of riluzole administration, and to correlate these effects with riluzole plasma levels. Nine healthy volunteers received a dose of 100 mg riluzole from day 1 to 7 of the study period. Electrophysiological examinations were performed on day 1 before and 2 h, 5 h and 8 h after riluzole administration, on day 2, day 3 and day 5 before riluzole administration, and on day 8. Plasma samples were taken simultaneously. The excitability of the motor cortex, supraspinal and spinal motor pathways was tested by studying intracortical facilitation and inhibition, the cortical silent period and motor threshold after TMS, as well as the peripheral silent period and F-wave amplitudes after electrical peripheral nerve stimulation. We found a significant reduction of intracortical facilitation, which correlated significantly with riluzole plasma levels. To a lesser extent, intracortical inhibition was enhanced on day 1, motor threshold was increased on day 8 and F-wave amplitudes were reduced. These changes did not correlate with riluzole plasma levels. We conclude that the main effect of riluzole in vivo is a reduction of intracortical facilitation, which is closely related to the drug's level in the plasma. The most probable mechanism involves an effect on glutamatergic synaptic transmission.     

反相高效液相色谱法测定人血浆中利鲁唑浓度

目的 :建立测定利鲁唑血药浓度的方法。方法 :采用反相高效液相色谱法 ,以DiamonsilTM C18(250mm×4. 6mm ,5μm )为色谱柱 ,甲醇 -0 .03mol/L磷酸二氢铵 (80∶20 ,V/V)为流动相 ,乙醚为提取剂 ,流速为0. 8ml/min ,检测波长为265nm。结果 :利鲁唑检测浓度线性范围为5～1000ng/ml ,最低检测浓度为5ng/ml ;高、中、低3种浓度的回收率分别为99 .51 %、95. 74 %和97. 12 % ,日内RSD≤1 .17 %、日间RSD≤6. 48 % (n=5)。结论 :本方法灵敏、准确、简单、快速 ,可用于人体药动学研究。     

Enhanced endogenous type I interferon cell-driven survival and inhibition of spontaneous apoptosis by Riluzole

Highly active antiretroviral therapy (HAART), although effective in improving the survival of HIV-1-infected individuals, has not been able to reconstitute the adaptive immune response. We have described the use of novel chemical agents to restore T-cell survival/proliferation by inducing cytokine production. Due to its cationic amphiphilic structure, these molecules appear to enhance immune restoration. In this study, we investigated the action of Riluzole (2-amino-6-trifuromethoxybenzothiazole) in HIV-1 infection. Riluzole is able to increase (effective dose from 1 to 1000 nM) the cell-survival of T cells from HIV-1-infected patients and inhibit spontaneous apoptosis. The immunomodulatory effect of riluzole-sensitized cells was ascribed to endogenous type I interferon (IFN) derived from monocytes. Riluzole might be used for restoring the cell survival of immunocompromised patients and eliminating latent infected cells upon HIV-1 reactivation.     

Co-treatment with riluzole and GDNF is necessary for functional recovery after ventral root avulsion injury

Unilateral avulsion of lumbar ventral roots kills approximately 50% of injured motoneurons within 2 weeks of surgery. Immediate treatment involving surgical reimplantation of the ventral root (VRI) or intrathecal glial cell line-derived neurotrophic factor (GDNF) delivery or intraperitoneal injection of riluzole for 2 weeks ameliorates motoneuron death to 80% of control but combining the different treatment paradigms did not further enhance survival except when GDNF was combined with VRI. At 3 months, all combined treatments provided a neuroprotective effect compared to avulsion only, but the neuroprotective effect of surgical reimplantation alone was not maintained unless combined with riluzole and GDNF treatment. Analysis of regenerating motoneurons using retrograde labelling techniques showed that riluzole, but not GDNF, increased the number of dendrites per labelled motoneuron. However, when functional motor recovery was assessed using the BBB locomotor score and rotarod tests, only VRI animals treated with riluzole and GDNF application showed significantly improved locomotor function in both tests. Our results show that functional recovery appears related to a combination of enhanced dendrite formation, increased motoneuron survival and the neurotrophic actions of GDNF. Thus, combination treatment may offer a new therapeutic strategy for treating patients with avulsion injury.     

Riluzole治疗肌萎缩侧索硬化

Riluzole是谷氨酸受体拮抗剂。现介绍Riluzole治疗ALS的作用机制和临床疗效。     

Neuroprotective agent riluzole potentiates postsynaptic GABA(A) receptor function.

The antiepileptic drug riluzole is a use-dependent blocker of voltage-gated Na(+) channels and selectively depresses action potential-driven glutamate over gamma-aminobutyric acid (GABA) release. Here we report that in addition to its presynaptic effect, riluzole at higher concentrations also strongly potentiates postsynaptic GABA(A) responses both in cultured hippocampal neurons and in Xenopus oocytes expressing recombinant receptors. Although peak inhibitory postsynaptic currents (IPSCs) of autaptic hippocampal neurons were inhibited, 20-100 microM riluzole significantly prolonged the decay of IPSCs, resulting in little change in total charge transfer. The effect was dose-dependent and reversible. Riluzole selectively increased miniature IPSC fast and slow decay time constants, without affecting their relative proportions. Miniature IPSC peak amplitude, rise time and frequency were unaffected, indicating a postsynaptic mechanism. In the Xenopus oocyte expression system, riluzole potentiated GABA responses by lowering the EC(50) for GABA activation. Riluzole directly gated a GABA(A) current that was partially blocked by bicuculline and gabazine. Pharmacological experiments suggest that the action of riluzole did not involve a benzodiazepine, barbiturate, or neurosteroid site. Instead, riluzole-induced potentiation was inhibited by the lactone antagonist alpha-isopropyl-alpha-methyl-gamma-butyrolatone (alpha-IMGBL). While most anticonvulsants either block voltage-gated Na(+) channels or potentiate GABA(A) receptors, our results suggest that riluzole may define an advantageous class of anticonvulsants with both effects.     

Interactions between riluzole and ABCG2/BCRP transporter

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative fatal disease. Drugs used in this disease need to cross the blood–brain barrier (BBB). Only riluzole is approved for ALS treatment. We have investigated riluzole as a breast cancer resistance protein (BCRP) substrate by studying its brain transport in CF1 mdr1a (−/−) mice and its intracellular uptake on BeWo cells (human placental choriocarcinoma cell line). We have also investigated the effect of riluzole on BCRP expression level and on its activity using the prazocin as a test probe for brain transport and intracellular uptake. Assays on mdr1a (−/−) mice and BeWo cells showed a higher uptake of riluzole when pretreated with a BCRP inhibitor. After repeated doses of riluzole, BCRP activity was increased in CF1 mdr1a (−/−) mice, riluzole uptake was decrease and both BCRP expression and activity were increased in BeWo cells. In conclusion, we report in this study that riluzole is transported by BCRP at the BBB level and can enhance its function. These results taken with our previous studies on riluzole and P-glycoprotein show that drug–drug interactions between riluzole and efflux transporters substrates may occur at the BBB level and should be taken into account in future clinical trial design in ALS.     

Riluzole disrupts autoresuscitation from hypothermic respiratory arrest in neonatal hamsters but not rats

We examined the effect of riluzole on expression of the central respiratory rhythm and the ability of neonates to autoresuscitate from hypothermic respiratory arrest using in vitro brainstem-spinal cord preparations of rats and hamsters. At a constant temperature of 27 °C, riluzole (5–200 μM) decreased the burst amplitude of respiratory-related motor discharge, but had little effect on the fictive respiratory frequency in rat preparations. In contrast, in hamster preparations, riluzole reduced fictive respiratory frequency, but had little effect on burst amplitude. Hamster preparations were more cold-tolerant than rat preparations, with respiratory arrest and autoresuscitation occurring at lower temperatures during cooling of the preparation. This difference was removed by incubation with riluzole (5 μM); riluzole significantly increased the temperature at which fictive respiration arrested and restarted in hamster preparations, but had no effect in rat preparations. The species differences observed in this study may reflect fundamental differences in the relative role of riluzole-sensitive mechanisms in the expression of the respiratory rhythm in early development of an altricial vs. a more precocial species.     

The fraction of activated <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="SmallCaps">d</Emphasis>-Aspartate receptors during synaptic transmission remains constant in the presence of the glutamate release inhibitor riluzole

Excessive N-methyl-D: -aspartate (NMDA) receptor activation is widely accepted to mediate calcium-dependent glutamate excitotoxicity. The uncompetitive, voltage-dependent NMDA receptor antagonist memantine has been successfully used clinically in the treatment of neurodegenerative dementia and is internationally registered for the treatment of moderate to severe Alzheimer's disease. Glutamate release inhibitors (GRIs) may also be promising for the therapy of some neurodegenerative diseases. During the clinical use of GRIs, it could be questioned whether there would still be a sufficient number of active NMDA receptors to allow any additional effects of memantine or similar NMDA receptor antagonists. To address this question, we determined the fraction of NMDA receptors contributing to postsynaptic events in the presence of therapeutically relevant concentrations of the GRI riluzole (1 muM) using an in vitro hippocampal slice preparation. We measured the charge transfer of pharmacologically isolated excitatory synaptic responses before and after the application of the selective, competitive NMDA receptor antagonist D-AP5 (100 muM). The fraction of activated NMDA receptors under control conditions did not differ from those in the presence of riluzole. It is therefore likely that NMDA receptor antagonists would be able to exert additional therapeutic effects in combination therapy with GRIs.     

The Riluzole Derivative 2-Amino-6-trifluoromethylthio-benzothiazole (SKA-19), a Mixed KCa2 Activator and NaV Blocker,is a Potent Novel Anticonvulsant

Inhibitors of voltage-gated sodium channels (Na_v) have been used as anticonvulsants since the 1940s, while potassium channel activators have only been investigated more recently. We here describe the discovery of 2-amino-6-trifluoromethylthio-benzothiazole (SKA-19), a thioanalog of riluzole, as a potent, novel anticonvulsant, which combines the two mechanisms. SKA-19 is a use-dependent Na_V channel blocker and an activator of small-conductance Ca²⁺-activated K⁺ channels. SKA-19 reduces action potential firing and increases medium afterhyperpolarization in CA1 pyramidal neurons in hippocampal slices. SKA-19 is orally bioavailable and shows activity in a broad range of rodent seizure models. SKA-19 protects against maximal electroshock-induced seizures in both rats (ED₅₀ 1.6 mg/kg i.p.; 2.3 mg/kg p.o.) and mice (ED₅₀ 4.3 mg/kg p.o.), and is also effective in the 6-Hz model in mice (ED₅₀ 12.2 mg/kg), Frings audiogenic seizure-susceptible mice (ED₅₀ 2.2 mg/kg), and the hippocampal kindled rat model of complex partial seizures (ED₅₀ 5.5 mg/kg). Toxicity tests for abnormal neurological status revealed a therapeutic index (TD₅₀/ED₅₀) of 6–9 following intraperitoneal and of 33 following oral administration. SKA-19 further reduced acute pain in the formalin pain model and raised allodynic threshold in a sciatic nerve ligation model. The anticonvulsant profile of SKA-19 is comparable to riluzole, which similarly affects Na_V and KCa2 channels, except that SKA-19 has a ~4-fold greater duration of action owing to more prolonged brain levels. Based on these findings we propose that compounds combining KCa2 channel-activating and Na_v channel-blocking activity exert broad-spectrum anticonvulsant and analgesic effects.

Electronic supplementary material

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