Riluzole Treatment Reduces Motoneuron Death Induced by Axotomy in Newborn Rats

Riluzole, a neuroprotective agent, preserves erectile function following bilateral cavernous nerve injury in male rats

Neurogenic erectile dysfunction is a highly prevalent complication in men undergoing radical prostatectomy. The underlying mechanisms remain incompletely defined and the effective therapy has been limited. This study aimed to evaluate the protective effect of riluzole and the role of PKC β and excitatory amino acid transporters (EAATs) mediating this effect in a rat model of bilateral cavernous injury (BCNI). A total of 48 male Sprague-Dawley rats were divided into sham, BCNI (at 7, 15 days post-injury) and BCNI treated with riluzole (8 mg/kg/day) groups. Erectile function was measured as maximum intracavernosal pressure (mICP)/mean arterial pressure (MAP) and total ICP/MAP. Changes in protein expressions of phospho (p)-PKC β IIser660 and EAATs were analysed in penis and major pelvic ganglion with western blotting. BCNI decreased erectile function at 7 and 15 days post-injury (mICP/MAP at 4 V: 0.45 ± 0.06 vs 0.84 ± 0.07; 0.34 ± 0.04 vs 0.77 ± 0.04 respectively; p < 0.001) whereas riluzole treatment (for 15 days) preserved erectile function (mICP/MAP at 4 V: 0.62 ± 0.03 vs 0.34 ± 0.04; p < 0.01). The decline in the expression of p-PKC β IIser660 was observed in penis at 7 and 15 days post-injury (p = 0.0003, p = 0.0033), which was prevented by riluzole treatment for 15 days (p = 0.0464). While expressions of EAAT-1 and EAAT-2 decreased in major pelvic ganglion following BCNI (p = 0.0428, p = 0.002), riluzole treatment for 15 days prevented the decrease only in EAAT-2 expression (p = 0.0456). Riluzole improved erectile function via possibly interacting with PKC β II and glutamatergic pathways, as a potential therapeutic candidate for erectile dysfunction.

Local Riluzole Release from a Thermosensitive Hydrogel Rescues Injured Motoneurons through Nerve Root Stumps in a Brachial Plexus Injury Rat Model

The C5-C6 nerve roots are usually spared from avulsion after brachial plexus injury (BPI) and can thus be used as donors for nerve repair. A BPI rat model with C5-C6 nerve root stumps has been established in our previous work. The aim of this study was to test whether riluzole loaded into a thermosensitive hydrogel could applied locally in the nerve root stumps of this BPI rat model, thus increasing the reparative effect of the nerve root stumps. Nile red (a hydrophobic dye) was used as a substitute for riluzole since riluzole itself does not emit light. Nile red, loaded into a thermosensitive hydrogel, was added to the nerve root stumps of the BPI rat model. Additionally, eighteen rats, with operation on right brachial plexus, were evenly divided into three groups: control (Con), thermosensitive hydrogel (Gel) and thermosensitive hydrogel loaded with riluzole (Gel + Ri) groups. Direct nerve repair was performed after local riluzole release for two weeks. Functional and electrophysiological evaluations and histological assessments were used to evaluate the reparative effect 8 weeks after nerve repair. Nile red was slowly released from the thermosensitive hydrogel and retrograde transport through the nerve root stumps to the motoneurons, according to immunofluorescence. Discernible functional recovery began earlier in the Gel + Ri group. The compound muscle action potential, ChAT-expressing motoneurons, positivity for neurofilaments and S100, diameter of regenerating axons, myelin sheath thickness and density of myelinated fibers were markedly increased in the Gel + Ri group compared with the Con and Gel groups. Our results indicate that the local administration of riluzole could undergo retrograde transportation through C5-C6 nerve root stumps, thereby promoting neuroprotection and increasing nerve regeneration.

Recent Findings on the Effects of Pharmacological Agents on the Nerve Regeneration after Peripheral Nerve Injury

Peripheral nerve injuries (PNIs) are accompanied with neuropathic pain and functional disability. Despite improvements in surgical repair techniques in recent years, the functional recovery is yet unsatisfied. Indeed a successful nerve repair depends not only on the surgical strategy but also on the cellular and molecular mechanisms involved in traumatic nerve injury. In contrast to all strategies suggested for nerve repair, pharmacotherapy is a cheap, accessible and non-invasive treatment that can be used immediately after nerve injury. This study aimed to review the effects of some pharmacological agents on the nerve regeneration after traumatic PNI evaluated by functional, histological and electrophysiological assessments. In addition, some cellular and molecular mechanisms responsible for their therapeutic actions, restricted to neural tissue, are suggested. These findings can not only help to find better strategies for peripheral nerve repair, but also to identify the neuropathic effects of various medications and their mechanisms of action.

Treatment with Riluzole Restores Normal Control of Soleus and Extensor Digitorum Longus Muscles during Locomotion in Adult Rats after Sciatic Nerve Crush at Birth

The effects of sciatic nerve crush (SNC) and treatment with Riluzole on muscle activity during unrestrained locomotion were identified in an animal model by analysis of the EMG activity recorded from soleus (Sol) and extensor digitorum longus (EDL) muscles of both hindlimbs; in intact rats (IN) and in groups of rats treated for 14 days with saline (S) or Riluzole (R) after right limb nerve crush at the 1st (1S and 1R) or 2nd (2S and 2R) day after birth. Changes in the locomotor pattern of EMG activity were correlated with the numbers of survived motor units (MUs) identified in investigated muscles. S rats with 2-8 and 10-28 MUs that survived in Sol and EDL muscles respectively showed increases in the duration and duty factor of muscle EMG activity and a loss of correlation between the duty factors of muscle activity, and abnormal flexor-extensor co-activation 3 months after SNC. R rats with 5, 6 (Sol) and 15-29 MUs (EDL) developed almost normal EMG activity of both Sol and control EDL muscles, whereas EDL muscles with SNC showed a lack of recovery. R rats with 8 (Sol) and 23-33 (EDL) MUs developed almost normal EMG activities of all four muscles. A subgroup of S rats with a lack of recovery and R rats with almost complete recovery that had similar number of MUs (8 and 24-28 vs 8 and 23-26), showed that the number of MUs was not the only determinant of treatment effectiveness. The results demonstrated that rats with SNC failed to develop normal muscle activity due to malfunction of neuronal circuits attenuating EDL muscle activity during the stance phase, whereas treatment with Riluzole enabled almost normal EMG activity of Sol and EDL muscles during locomotor movement.

The effect of Riluzole on functional recovery of locomotion in the rat sciatic nerve crush model

PURPOSE

Peripheral nerve injury (PNI) is common disorder that represents more than 3 % of all traumatic injury cases. One type of PNI, sciatic nerve injury, leads to considerable motoneuron dysfunction. Because Riluzole is clinically approved for the treatment of motoneuron disease, we evaluated whether Riluzole treatment could enhance the nerve regeneration process and improve functional outcome after sciatic nerve crush in rats.

METHODS

In acute treatment groups, a single dose of Riluzole (6 and 8 mg/kg) was administered intra-peritoneally 15 min after the crush nerve injury. In the chronic treatment groups, animals were treated with Riluzole (4 and 6 mg/kg/d) for 8 days. Sciatic functional index (SFI) was evaluated for 9 weeks after injury. Furthermore, electrophysiological and morphometric evaluations were performed at the 9th week following injury.

RESULTS

Acute and chronic administrations of Riluzole immediately after sciatic nerve crush result in significantly delayed regeneration and reduced motor function outcome.

CONCLUSIONS

These findings suggest that early administration of even a single dose of Riluzole after sciatic nerve crush injury can delay motor function recovery. This effect may not depend on its anti-nociceptive activity.

Pharmacologic rescue of motor and sensory function by the neuroprotective compound P7C3 following neonatal nerve injury

Nerve injuries cause pain, paralysis and numbness that can lead to major disability, and newborns often sustain nerve injuries during delivery that result in lifelong impairment. Without a pharmacologic agent to enhance functional recovery from these injuries, clinicians rely solely on surgery and rehabilitation to treat patients. Unfortunately, patient outcomes remain poor despite application of the most advanced microsurgical and rehabilitative techniques. We hypothesized that the detrimental effects of traumatic neonatal nerve injury could be mitigated with pharmacologic neuroprotection, and tested whether the novel neuroprotective agent P7C3 would block peripheral neuron cell death and enhance functional recovery in a rat neonatal nerve injury model. Administration of P7C3 after sciatic nerve crush injury doubled motor and sensory neuron survival, and also promoted axon regeneration in a dose-dependent manner. Treatment with P7C3 also enhanced behavioral and muscle functional recovery, and reversed pathological mobilization of spinal microglia after injury. Our findings suggest that the P7C3 family of neuroprotective compounds may provide a basis for the development of a new neuroprotective drug to enhance recovery following peripheral nerve injury.