Just in time and place: NOS/NO system assembly in neuromuscular junction formation

Spasticity Treatment Beyond Botulinum Toxins

Botulinum toxin (BonT) is the mainstream treatment option for post-stroke spasticity. BoNT therapy may not be adequate in those with severe spasticity. There are a number of emerging treatment options for spasticity management. In this paper, we focus on innovative and revived treatment options that can be alternative or complementary to BoNT therapy, including phenol neurolysis, cryoneurolysis, and extracorporeal shock wave therapy.

Extracorporeal Shockwave Treatment as Additional Therapy in Patients with Post-Stroke Spasticity of Upper Limb-A Narrative Review

Stroke is a severe injury of the central nervous system (CNS) and one of the leading causes of long-term disability and mortality. One of the main symptoms of neurological diseases is spasticity. This is defined as a motor condition characterized by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks and resulting in the hyperexcitability of the stretch reflex. Rehabilitation after a stroke is focused on relearning lost skills and regaining independence. Many new methods in neurorehabilitation have been introduced. This review concentrates on the current evidence for extracorporeal shockwave therapy (ESWT) as a noninvasive alternative to treat spasticity. We present the effect of EWST and radial EWST interventions to post-stroke patients with spasticity in the upper limb. Our collected data suggest that different parameters of shockwaves can be used to achieve functional improvementsin the upper limb after a stroke. Our accumulated data imply that ESWT is safe and can be used for pain relief, reduced muscle tension, and an increased range of motion. According to many studies, complications after shockwave treatment are infrequent. Transient complications after shockwave therapy (ESWT) include redness, tingling, pain, and bruising. We reviewed clinical trials that present the possible benefits in upper-limb function after shockwave therapy for post-stroke patients. In this article, we used many database search engines, including PEDro. In the stroke rehabilitation literature, a key methodological problem is the design of double-blind studies, which very often are not feasible.

Global trends in research on extracorporeal shock wave therapy (ESWT) from 2000 to 2021

BACKGROUND

This study intended to analyze the application of extracorporeal shock wave therapy in medicine and to evaluate the quality of related literature.

METHODS

All publications were extracted from 2000 to 2021 from the Web of Science Core Collection (WoSCC). The literature characteristics were depicted by VOSviewer (version 1.6.15) and the online bibliometric website ( http://bibliometric.com/ ). The future trends and hotspots were conducted by Bibliographic Item Co-occurrence Matrix Builder (version 2.0) and gCLUTO software.

RESULTS

We analyzed 1774 articles corresponding to the criteria for ESWT publications from 2000 to 2021. Most studies were conducted within the United States and China which besides have the most cooperation. The most published research institutions are Chang Gung University, Kaohsiung Chang Gung Memorial Hospital, and Kaohsiung Medical University. Six research hotspots were identified by keyword clustering analysis: Cluster0: The effects of ESWT on muscle spasticity; Cluster1: The application of ESWT in osteoarthritis (OA); Cluster2: Therapeutic effect of ESWT on tendon diseases; Cluster3: Early application of ESWT/ESWL in urolithiasis; Cluster4: The Role of angiogenesis in ESWT and the efficiency of ESWT for penile disease; Cluster5: The Special value of radial extracorporeal shock wave therapy (rESWT).

CONCLUSIONS

A comprehensive and systematic bibliometric analysis of ESWT was conducted in our study. We identified six ESWT-related research hotspots and predicted future research trends. With the gradual increase of research on ESWT, we find that ESWT is used more and more extensively, such in musculoskeletal disease, bone delay union, neurological injury, andrology disorders, lymphedema, and so on. In addition, the mechanism is not destructive damage, as initially thought, but a restorative treatment. Furthermore, delayed union, cellulite, burn, and diabetic foot ulcers may be the future direction of scientific study.

Recent Advances in the Treatment of Spasticity: Extracorporeal Shock Wave Therapy

Spasticity is a common sequala of the upper motor neuron lesions. For instance, it often occurs in the first 4 weeks after stroke and is seen in more than one-third of stroke survivors after 12 months. In recent years, extracorporeal shock wave therapy (ESWT) has been recognized as a safe and effective method for reducing muscle spasticity. Possible/relevant mechanisms include nitric oxide production, motor neuron excitability reduction, induction of neuromuscular transmission dysfunction, and direct effects on rheological properties. There are two types of ESWT, focused and radial, with the radial type more commonly applied for treating muscle spasticity. Concerning the optimal location for applying ESWT, the belly muscles and myotendinous junction seem to produce comparable results. The effects of ESWT on spasticity are known to last at least four to six weeks, while some studies report durations of up to 12 weeks. In this review, the authors will focus on the current evidence regarding the effectiveness of ESWT in spasticity, as well as certain technical parameters of ESWT, e.g., the intensity, frequency, location, and number of sessions. The pertinent literature has been reviewed, with an emphasis on post-stroke upper limbs, post-stroke lower limbs, cerebral palsy, and multiple sclerosis. In short, while ESWT has positive effects on parameters such as the modified Ashworth scale, mixed results have been reported regarding functional recovery. Of note, as botulinum toxin injection is one of the most popular and effective pharmacological methods for treating spasticity, studies comparing the effects of ESWT and botulinum toxin injections, and studies reporting the results of their combination, are also reviewed in this paper.

Effects of Radial Shockwave Therapy and Orthotics Applied with Physical Training on Motor Function of Children with Spastic Diplegia: A Randomized Trial

Aims: To explore the effects of radial shockwave therapy (rSWT) combined with standard orthotic management (SOM) on spasticity, functional balance, and gait in children with spastic diplegia. Methods: Sixty children with diplegia were allocated to group I (rSWT, n = 20), group II (SOM, n = 20), or group III (rSWT + SOM, n = 20). All groups received a physical training program 3 times/week for 3 months. Assessments were completed before and immediately after the intervention and included the Hoffman reflex/Myogenic response ratio of the soleus muscle (H/M ratio), balance, and gait. Results: At a significance criterion adjusted to p ˂ .006, there were no between-group differences in balance or gait (p > .006). The rSWT + SOM group had a greater improvement of H/M ratio compared to rSWT alone (p = .001) but not to SOM alone (p = .04). Within-group analysis demonstrated significant improvement of all variables for rSWT + SOM (p ˂ .006). The H/M ratio and knee midstance angle exhibited clinically meaningful improvement for rSWT alone (p ˂ .006). No significant changes were observed in any variable for SOM alone (p > .006). Conclusions: Radial shockwave and orthotics together, or either of them along with physical training did not differ in improving balance or gait. Their combination was more effective than rSWT alone in reducing spasticity.

Collagen VI is required for the structural and functional integrity of the neuromuscular junction

The synaptic cleft of the neuromuscular junction (NMJ) consists of a highly specialized extracellular matrix (ECM) involved in synapse maturation, in the juxtaposition of pre- to post-synaptic areas, and in ensuring proper synaptic transmission. Key components of synaptic ECM, such as collagen IV, perlecan and biglycan, are binding partners of one of the most abundant ECM protein of skeletal muscle, collagen VI (ColVI), previously never linked to NMJ. Here, we demonstrate that ColVI is itself a component of this specialized ECM and that it is required for the structural and functional integrity of NMJs. In vivo, ColVI deficiency causes fragmentation of acetylcholine receptor (AChR) clusters, with abnormal expression of NMJ-enriched proteins and re-expression of fetal AChRγ subunit, both in Col6a1 null mice and in patients affected by Ullrich congenital muscular dystrophy (UCMD), the most severe form of ColVI-related myopathies. Ex vivo muscle preparations from ColVI null mice revealed altered neuromuscular transmission, with electrophysiological defects and decreased safety factor (i.e., the excess current generated in response to a nerve impulse over that required to reach the action potential threshold). Moreover, in vitro studies in differentiated C2C12 myotubes showed the ability of ColVI to induce AChR clustering and synaptic gene expression. These findings reveal a novel role for ColVI at the NMJ and point to the involvement of NMJ defects in the etiopathology of ColVI-related myopathies.

Effect of extracorporeal shock wave therapy on gait pattern in hemiplegic cerebral palsy: a randomized controlled trial

OBJECTIVE

The aim of this study was to investigate the effects of shock wave therapy on gait pattern in children with hemiplegic cerebral palsy.

DESIGN

Fifteen children were assigned to the study group, whose members received shock wave therapy (1500 shots/muscle, frequency of 5Hz, energy of 0.030 mJ/mm, one session/wk). Another 15 were assigned to the control group, whose members participated in a conventional physical therapy exercise program for 3 successive months. Baseline and posttreatment assessments were performed using the Modified Ashworth Scale to evaluate spasticity degrees and using a three-dimensional gait analysis to evaluate gait parameters.

RESULTS

Children in the study group showed a significant improvement when compared with those in the control group (P < 0.005). The Modified Ashworth scores after treatment were 1.86 (0.22) and 1.63 (0.23) for the control and study groups, respectively. The gait parameters (stride length, cadence, speed, cycle time, and stance phase percentage) after treatment were 0.5 m, 125 steps/min, 0.6 m/sec, 0.48 sec, and 50.4% and 0.74 m, 119 steps/min, 0.75 m/sec, 0.65 sec, and 55.9% for the control group and the study group, respectively.

CONCLUSIONS

Shock wave therapy may be a useful tool for improving spasticity and gait pattern in children with hemiplegic cerebral palsy.

Effects of extracorporeal shock wave therapy on functional and strength recovery of handgrip in patients affected by epicondylitis

Extracorporeal shock wave therapy (ESWT) is effective in the treatment of tendinopathy. We designed a prospective observational clinical study to assess the correlation between clinical and functional measures and recovery of strength after ESWT for epicondylitis. We analyzed 26 patients. We measured progressive improvement in visual analogue scale values (p < 0.0005) and Mayo Elbow Performance Index scores (p = 0.004) for the pathologic limb. Monitoring of handgrip failed to reveal changes in values at any follow-up (p > 0.05). We found no correlation between degree of clinical function and muscle deficit during follow-up. After ESWT, there was a tendency toward a decrease in grip strength, especially in the dominant limb. This could be related to the effects of ESWT, which reduces spasticity in painful hypertonic muscles. These data may be useful in defining the expectations for function during ESWT for epicondylitis, particularly for elite athletes.

SBOTE study: extracorporeal shock wave therapy versus electrical stimulation after botulinum toxin type a injection for post-stroke spasticity-a prospective randomized trial

Research is on-going to identify new methods of biostimulation to increase the effect of botulinum toxin type A (BTX-A) in the treatment of spasticity. The Spasticity treated by Botulinum Toxin and ESWT (SBOTE) study is a prospective, randomized controlled trial assessing the effectiveness of extracorporeal shock wave therapy (ESWT) given immediately after BTX-A injections compared with electrical stimulation (ES) given immediately after BTX-A therapy for the management of focal upper limb spasticity in stroke patients. ES was given for 30 min twice a day for 5 days starting at 5 Hz; ESWT was given once a day for 5 days. At study follow-up, patients treated with BTX-A injections and ESWT showed a statistically greater significance and continuous decrease of spasticity measure (modified Ashworth scale [MAS]: 1.37, 1.75 and 1.58 at 15, 30 and 90 days post-treatment, respectively), of spasms (spasm frequency scale [SFS]: 0.8 and 0.25 at 30 and 90 days post-treatment, respectively) and of pain (visual analogue scale [VAS]: 1.94 and 1.87 at 30 and 90 days, respectively) compared with patients treated with BTX-A injections and ES (MAS: 2.37, 2.18 and 2.18, respectively) (p < 0.05) (SFS: 1.5 and 1.06, respectively) (p < 0.05) (VAS: 2.44 and 2.69 respectively) (p < 0.05). ESWT enhances the effect of BTX-A to a greater extent than ES, probably by modulating rheology of the muscle and neurotransmission at the neuromuscular junction.

Spasticity and electrophysiologic changes after extracorporeal shock wave therapy on gastrocnemius

Objective

To evaluate the spasticity and electrophysiologic effects of applying extracorporeal shock wave therapy (ESWT) to the gastrocnemius by studying F wave and H-reflex.

Method

Ten healthy adults and 10 hemiplegic stroke patients with ankle plantarflexor spasticity received one session of ESWT on the medial head of the gastrocnemius. The modified Ashworth scale (MAS), tibial nerve conduction, F wave, and H-reflex results were measured before and immediately after the treatment. The Visual Analogue Scale (VAS) was used during ESWT to measure the side effects, such as pain.

Results

There were no significant effects of ESWT on the conduction velocity, distal latency and amplitude of tibial nerve conduction, minimal latency of tibial nerve F wave, latency, or H-M ratio of H-reflex in either the healthy or stroke group. However, the MAS of plantarflexor was significantly reduced from 2.67±1.15 to 1.22±1.03 (p<0.05) after applying ESWT in the stroke group.

Conclusion

After applying ESWT on the gastrocnemius in stroke patients, the spasticity of the ankle plantarflexor was significantly improved, with no changes of F wave or H-reflex parameters. Further studies are needed to evaluate the mechanisms of the antispastic effect of ESWT.

The roles of the dystrophin-associated glycoprotein complex at the synapse

Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and is characterized by progressive muscle wasting. A number of Duchenne patients also present with mental retardation. The dystrophin protein is part of the highly conserved dystrophin-associated glycoprotein complex (DGC) which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems. Many years of research into the roles of the DGC in muscle have revealed its structural function in stabilizing the sarcolemma. In addition, the DGC also acts as a scaffold for various signaling pathways. Here, we discuss recent advances in understanding DGC roles in the nervous system, gained from studies in both vertebrate and invertebrate model systems. From these studies, it has become clear that the DGC is important for the maturation of neurotransmitter receptor complexes and for the regulation of neurotransmitter release at the NMJ and central synapses. Furthermore, roles for the DGC have been established in consolidation of long-term spatial and recognition memory. The challenges ahead include the integration of the behavioral and mechanistic studies and the use of this information to identify therapeutic targets.

Role for the skeletal muscle action potential in non-Hebbian long-term depression at the amphibian (Bufo marinus) neuromuscular junction

Retrograde signaling from skeletal muscle cells to motor nerve terminals is a recognized mechanism for modulating the strength of neuromuscular transmission. We recently described a form of long-term depression of transmitter release at the mature neuromuscular junction that is dependent on the production of nitric oxide, most likely by the muscle cell (Etherington and Everett 2004 J Physiol (Lond) 559:507-517). We now show that the depression is blocked by treating neuromuscular preparations with mu-conotoxin G111A, an antagonist of skeletal muscle voltage gated sodium channels, indicating that the depression requires postsynaptic action potential firing. Experiments on dually-innervated sartorius muscles revealed that propagation of action potentials generated by low-frequency stimulation of one nerve branch gives rise to nitric-oxide mediated depression at unstimulated nerve terminals located many millimetres away on the same muscle fiber. The non-Hebbian pattern of expression of the depression, as well as its reliance on postsynaptic action potential firing, distinguish it from forms of synaptic depression described at immature neuromuscular synapses and may provide a mechanism for coregulation of the strength of motoneurons innervating the same postsynaptic cell.

Changes in mRNA for CAPON and Dexras1 in adult rat following sciatic nerve transection

Peripheral nerve transection has been implicated to cause a production of neuronal nitric oxide synthase (nNOS), which may influence a range of post-axotomy processes necessary for neuronal survival and nerve regeneration. Carboxy-terminal post synaptic density protein/Drosophila disc large tumor suppressor/zonula occuldens-1 protein (PDZ) ligand of neuronal nitric oxide synthase (CAPON), as an adaptor, interacts with nNOS via the PDZ domain helping regulate nNOS activity at postsynaptic sites in neurons. And Dexras1, a small G protein mediating multiple signal transductions, has been reported to form a complex with CAPON and nNOS. A role for the physiologic linkage by CAPON of nNOS to Dexras1 has suggested that NO-mediated activation of Dexras1 is markedly enhanced by CAPON. We investigated the changes in mRNA for CAPON, Dexras1 and nNOS in the sciatic nerve, dorsal root ganglia and lumbar spinal cord of adult rat following sciatic axotomy by TaqMan quantitative real-time PCR and in situ hybridization combined with immunofluorescence. Signals of mRNA for CAPON and Dexras1 were initially expressed in these neural tissues mentioned, transiently increased at certain time periods after sciatic axotomy and finally recovered to the basal level. It was also found that nNOS mRNA underwent a similar change pattern during this process. These results suggest that CAPON as well as Dexras1 may be involved in the different pathological conditions including nerve regeneration, neuron loss or survival and even pain process, possibly via regulating the nNOS activity or through the downstream targets of Dexras1.

L-citrulline inhibits [3H]acetylcholine release from rat motor nerve terminals by increasing adenosine outflow and activation of A1 receptors

BACKGROUND AND PURPOSE

Nitric oxide (NO) production and depression of neuromuscular transmission are closely related, but little is known about the role of L-citrulline, a co-product of NO biosynthesis, on neurotransmitter release.

EXPERIMENTAL APPROACH

Muscle tension recordings and outflow experiments were performed on rat phrenic nerve-hemidiaphragm preparations stimulated electrically.

KEY RESULTS

L-citrulline concentration-dependently inhibited evoked [(3)H]ACh release from motor nerve terminals and depressed nerve-evoked muscle contractions. The NO synthase (NOS) substrate, L-arginine, and the NO donor, 3-morpholinosydnonimine chloride (SIN-1), also inhibited [(3)H]ACh release with a potency order of SIN-1>L-arginine>L-citrulline. Co-application of L-citrulline and SIN-1 caused additive effects. NOS inactivation with N(omega)-nitro-L-arginine prevented L-arginine inhibition, but not that of L-citrulline. The NO scavenger, haemoglobin, abolished inhibition of [(3)H]ACh release caused by SIN-1, but not that caused by L-arginine. Inactivation of guanylyl cyclase with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) fully blocked SIN-1 inhibition, but only partially attenuated the effects of L-arginine. Reduction of extracellular adenosine accumulation with adenosine deaminase or with the nucleoside transport inhibitor, S-(p-nitrobenzyl)-6-thioinosine, attenuated the effects of L-arginine and L-citrulline, while not affecting inhibition by SIN-1. Similar results were obtained with the selective adenosine A(1) receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine. L-citrulline increased the resting extracellular concentration of adenosine, without changing that of the adenine nucleotides.

CONCLUSIONS AND IMPLICATIONS

NOS catalyses the formation of two neuronally active products, NO and L-citrulline. While, NO may directly reduce transmitter release through stimulation of soluble guanylyl cyclase, the inhibitory action of L-citrulline may be indirect through increasing adenosine outflow and subsequently activating inhibitory A(1) receptors.

Human skeletal muscle structure and function preserved by vibration muscle exercise following 55 days of bed rest

Prolonged immobilization of the human body results in functional impairments and musculoskeletal system deconditioning that may be attenuated by adequate muscle exercise. In a 56-day horizontal bed rest campaign involving voluntary males we investigated the effects of vibration muscle exercise (RVE, 2x6 min daily) on the lower limb skeletal muscles using a newly designed foot plantar trainer (Galileo Space) for use at supine position during bed rest. The maximally voluntary isometric plantar flexion force was maintained following regular RVE bouts during bed rest (controls -18.6 %, P<0.05). At the start (BR2) and end of bed rest (BR55) muscle biopsies were taken from both mixed fast/slow-type vastus lateralis (VL) and mainly slow-type soleus muscle (SOL), each having n=10. RVE group: the size of myofiber types I and II was largely unchanged in VL, and increased in SOL. Ctrl group: the SOL depicted a disrupted pattern of myofibers I/II profiles (i.e., type II>140 % vs. preBR) suggesting a slow-to-fast muscle phenotype shift. In RVE-trained SOL, however, an overall conserved myofiber I/II pattern was documented. RVE training increased the activity-dependent expression of nitric oxide synthase type 1 immunofluorescence at SOL and VL myofiber membranes. These data provide evidence for the beneficial effects of RVE training on the deconditioned structure and function of the lower limb skeletal muscle. Daily short RVE should be employed as an effective atrophy countermeasure co-protocol preferentially addressing postural calf muscles during prolonged clinical immobilization or long-term human space missions.

Neuromuscular contacts induce nitric oxide signals in skeletal myotubes in vitro

It has previously been shown that skeletal myotubes express nitric oxide synthase (NOS) and produce and release NO signals. NOS is also part of agrin-induced acetylcholine receptor aggregations on myotubes. As nerve-muscle interactions underlie reciprocal signaling mechanisms, we hypothesized that NO signals in target myotubes may be induced by neuromuscular contacts in development. Chimeric neuron-myotube co-cultures were prepared using p75-selected spinal cord neurons from embryonic chicken. Confocal imaging revealed robust 1,2-diaminoanthraquinone red fluorescence indicative of de novo formation of NO only in those myotubes which were contacted by neurites, also verified by pre- and postsynaptic marker costaining (anti-synaptotagmin and alpha-bungarotoxin). Neither soluble agrin nor sensory dorsal root ganglionic neurons showed comparable effects in this model. We concluded that in target skeletal muscle cells the NOS/NO system is controlled by motoneuron contacts by as yet incompletely understood signaling mechanisms. Endogenous NO signaling in myotubes may be essential during synapse formation and plasticity of the neuromuscular system.

Long-term effect of shock wave therapy on upper limb hypertonia in patients affected by stroke

BACKGROUND AND PURPOSE

Spasticity is a disabling complication of stroke and different noninvasive treatments are used to reduce muscle hypertonia. Shock waves are defined as a sequence of single sonic pulses largely used in the treatment of diseases involving bone and tendon as well as muscular contractures. The effect and duration of extracorporeal shock wave therapy (ESWT) was investigated on muscle hypertonia of the hand and wrist.

METHODS

A total of 20 patients affected by stroke associated with severe hypertonia in upper limbs were evaluated. Placebo stimulation was performed 1 week before active stimulation in each patient. Evaluation was performed using the National Institutes of Health and Ashworth scales and video monitoring with a digital goniometer before and immediately after placebo or active stimulation. Motor nerve conduction velocity from abductor digiti minimi were recorded. Patients were monitored at 1, 4, and 12 weeks after active treatment.

RESULTS

After active ESWT, patients showed greater improvement in flexor tone of wrist and fingers compared with placebo stimulation. At the 1- and 4-week follow-up visits, a significant decrease of passive muscle tonicity was noted on muscles in all patients receiving active treatment. At 12 weeks after therapy, 10 of the 20 patients showed persistent reduction in muscle tone. There were no adverse events associated with ESWT.

CONCLUSIONS

ESWT reduces hypertonia of the wrist and finger muscles for > or =12 weeks after treatment. The possible mechanisms of action of ESWT are discussed.

Functionality of nitrated acetylcholine receptor: The two-step formation of nitrotyrosines reveals their differential role in effectors binding

The presence of nitrotyrosines is associated with several neurodegenerative pathologies. We evaluated the functionality of the nicotinic acetylcholine receptor possessing nitrotyrosines. The spectrum of the nitrated receptor displays an absorption band characteristic of ortho-nitrophenol. The presence of carbamylcholine in the agonist site prevented the effect of nitration by tetranitromethane in some conditions. The nitration occurred with two discrete steps and pointed out the differential involvement of tyrosines in the binding of acetylcholine and neurotoxin. We concluded that at least two residues involved in agonist binding can be nitrated, which bring similar contributions to the binding energy of the neurotransmitter.

CAPON expression in skeletal muscle is regulated by position, repair, NOS activity, and dystrophy

In skeletal muscle, the localization of nNOS is destabilized in the absence of dystrophin, which impacts muscle function and satellite cell activation. In neurons, the adaptor protein, carboxy-terminal PDZ ligand of nNOS (CAPON), regulates the distribution of neuronal nitric oxide synthase (nNOS), which produces the key signaling molecule nitric oxide (NO). While a CAPON-like gene is known to compensate functionally for a dystrophic phenotype in muscle of Caenorhabditis elegans, CAPON expression has not been reported for mammalian muscle. Here, CAPON expression was identified in mouse muscle using Northern and Western blotting and in situ hybridization in combination with immunostaining for laminin. CAPON RNA was expressed in developing normal and dystrophic muscles near fiber junctions with tendons, and levels increased from 1 to 3 weeks. In regenerating normal muscle and also in dystrophic muscles in the mdx mouse, CAPON transcripts were prominent in satellite cells and new myotubes. Expression of CAPON RNA increased in diaphragm muscle of normal and mdx mice after treatment with L-arginine, the NOS substrate. Both CAPON and utrophin protein levels increased in dystrophic quadriceps muscle after treatment with the steroid deflazacort plus L-arginine, known to reduce the dystrophic phenotype. The identification of CAPON transcripts and protein in mammalian muscle and responses to L-arginine suggest CAPON may have a functional role in stabilizing neuronal NOS in skeletal muscle in the cytoskeletal complex associated with dystrophin/utrophin, with possible applications to therapy for human muscular dystrophy.

Sequestration of nNOS in neurofilamentous aggregate bearing neurons in vitro leads to enhanced NMDA-mediated calcium influx

The significance of copper/zinc superoxide dismutase (SOD1) and neuronal nitric oxide synthase (nNOS) co-localization to neurofilamentous (NF) aggregates in amyotrophic lateral sclerosis (ALS) is unknown. In this study, we have used dissociated motor neurons from either C57BL/6 or mice that over-express the human low molecular weight neurofilament protein (hNFL+/+) to examine the relationship between NF aggregate formation, SOD1 and nNOS co-localization, and the regulation of NMDA-mediated calcium influx in vitro. The intracellular distribution of NF aggregates, SOD1 and nNOS was examined by confocal microscopy and NMDA-induced alterations in intracellular calcium levels using either Oregon green fluorescence or FURA-2 photometric imaging. Cell death was assessed using an antibody to activated caspase-3. C57 Bl/6 motor neurons expressed nNOS in a punctate manner, whereas SOD1 was distributed homogeneously throughout the cytosol. In contrast, hNFL+/+ motor neurons demonstrated co-localization of SOD1 and nNOS by day 9 post-plating, preceding the formation of NF aggregates. Both proteins co-localized to NF aggregates once formed. With NMDA stimulation, aggregate-bearing hNFL+/+ motor neurons demonstrated significant increases in intracellular calcium, whereas only a minimal alteration in intracellular calcium was observed in C57 Bl/6 neurons. Following stimulation with 100 microM NMDA, 75.5+/-5.5% of hNFL+/+ neurons became apoptotic, whereas only 16.3+/-5.3% of C57 Bl/6 were. These observations suggest that the presence of NF aggregates results in a failure of regulation of NMDA-mediated calcium influx, and that this occurs due to the sequestration of nNOS to the NF aggregate, preventing its down-regulation of the NMDA receptor.

The potential of nitric oxide therapeutics in stroke

The therapeutic modulation of the nitric oxide (NO) system has generated considerable interest as a new way for managing many disease processes. In stroke, a useful strategy is to increase NO availability and thereby exploit its beneficial antiplatelet, antiatherosclerotic, haemodynamic and neuroprotective properties. Pharmacologically, this can be achieved by providing NO substrate, using NO donors or by upregulating nitric oxide synthase. Alternatively, one can reduce NO availability by inhibiting NO synthase and thereby limiting its pro-inflammatory and neurotoxic properties. This article reviews developments in NO-related therapeutics for treatment of stroke, with a particular emphasis on compounds that are in the clinical research and development pipeline. Although the routine use of NO therapeutics for the prevention or treatment of stroke cannot currently be recommended, we are evidently at an exciting stage in their pharmacological development. Definitive randomised controlled trials in stroke patients are required as a matter of urgency.

The role of utrophin in the potential therapy of Duchenne muscular dystrophy

Duchenne muscular dystrophy is an X-linked recessive muscle wasting disease caused by the absence of the muscle cytoskeletal protein, dystrophin. Dystrophin is a member of the spectrin superfamily of proteins and is closely related in sequence similarity and functional motifs to three proteins that constitute the dystrophin related protein family, including the autosomal homologue, utrophin. An alternative strategy circumventing many problems associated with somatic gene therapies for Duchenne muscular dystrophy has arisen from the demonstration that utrophin can functionally substitute for dystrophin and its over-expression in muscles of dystrophin-null transgenic mice completely prevents the phenotype arising from dystrophin deficiency. One potential approach to increase utrophin levels in muscle for possible therapeutic purpose in humans is to increase expression of the utrophin gene at a transcriptional level via promoter activation. This has lead to an interest in the identification and manipulation of important regulatory regions and/or molecules that increase the expression of utrophin and their delivery to dystrophin-deficient tissue. As pre-existing cellular mechanisms are utilized, this approach would avoid many problems associated with conventional gene therapies.