Rhythms of serum melatonin in rats with acute spinal cord injury at the cervical and thoracic regions

Melatonin secretion and sleep disorders in patients with spinal cord injuries

STUDY DESIGN

Prospective observational study.

OBJECTIVES

To evaluate melatonin secretion, daytime sleepiness and sleep disorders in patients with spinal cord injuries (SCI), and their association with lesion level.

SETTING

Specialized neuro rehabilitation hospital in France METHODS: Prospective observational study of patients aged over 18 hospitalized in for spinal cord injury. Sleep quality was measured with the Pittsburgh Sleep Quality Index (PQSI), daytime sleepiness with the Epworth Sleepiness scale (ESS), and melatonin secretion by 24 h urinary dosage of 6-sulphatoxy-melatonin.

RESULTS

213 patients were screened, 21 patients were included: 17 complete (AIS A) and 4 lesions (AIS B), 76% of traumatic origin with 12 tetraplegic and 9 paraplegic, mean 10 (range 0.5-40) years after injury. Mean age was 46.8 ± 14.7 years, mean BMI 23.56 ± 4.1 and men outnumbered women (15 vs 6). Melatonin secretion was analyzed by 24 h secretion and by secretion profile. Comparing retained vs abolished secretion, only 23% (4/17) of patients with a lesion above T8 retained melatonin secretion, compared to 80% (4/5) with a lesion below T8 (p = 0.022). Non significant differences were found in secretion profile in patients who retained secretion: no patient with a lesion above T8 had a normal secretion profile compared to 50% with a lesion below T8 and in the impact of partial vs total lesions above T8 in whom 17% (2/12) of complete ASIA-A lesions and 50% (2/4) of incomplete lesions retained secretion.

CONCLUSION

Lesions of the spinal cord above T8 are strongly associated with abolition of melatonin secretion.

Melatonin, a natural antioxidant therapy in spinal cord injury

Spinal cord injury (SCI) is a sudden onset of disruption to the spinal neural tissue, leading to loss of motor control and sensory function of the body. Oxidative stress is considered a hallmark in SCI followed by a series of events, including inflammation and cellular apoptosis. Melatonin was originally discovered as a hormone produced by the pineal gland. The subcellular localization of melatonin has been identified in mitochondria, exhibiting specific onsite protection to excess mitochondrial reactive oxygen species and working as an antioxidant in diseases. The recent discovery regarding the molecular basis of ligand selectivity for melatonin receptors and the constant efforts on finding synthetic melatonin alternatives have drawn researchers' attention back to melatonin. This review outlines the application of melatonin in SCI, including 1) the relationship between the melatonin rhythm and SCI in clinic; 2) the neuroprotective role of melatonin in experimental traumatic and ischemia/reperfusion SCI, i.e., exhibiting anti-oxidative, anti-inflammatory, and anti-apoptosis effects, facilitating the integrity of the blood-spinal cord barrier, ameliorating edema, preventing neural death, reducing scar formation, and promoting axon regeneration and neuroplasticity; 3) protecting gut microbiota and peripheral organs; 4) synergizing with drugs, rehabilitation training, stem cell therapy, and biomedical material engineering; and 5) the potential side effects. This comprehensive review provides new insights on melatonin as a natural antioxidant therapy in facilitating rehabilitation in SCI.

Riluzole promotes neurological function recovery and inhibits damage extension in rats following spinal cord injury: a meta-analysis and systematic review

Spinal cord injury (SCI) is a devastating condition that has few treatment options. Riluzole, a sodium channel blocker used to treat amyotrophic lateral sclerosis, has been initially trialed in human SCI. We performed a systematic review to critically assess the efficacy of riluzole in locomotor recovery and damage extension in SCI rat models, and the potential for clinical translation. PubMed, Embase, Cochrane Library, and Chinese databases were searched from their inception date to March 2018. Two reviewers independently selected animal studies that evaluated neurological recovery and lesion area following riluzole treatment in SCI rat models, extracted data and assessed methodological quality. Pairwise meta-analysis, subgroup analysis, and network meta-analysis were performed to assess the effects of riluzole on SCI. Ten eligible studies were included. Two studies had high methodological quality. Overall, the Basso, Beattie, and Bresnahan scores were increased in riluzole-treated animals versus controls, and effect sizes showed a gradual increase from the 1st (five studies, n = 104, mean difference = 1.24, 95% CI = 0.11 to 2.37, p = 0.03) to 6th week after treatment (five studies, n = 120, mean difference = 2.34, 95% CI = 1.26 to 3.42, p < 0.0001). Riluzole was associated with improved outcomes in the inclined plane test and the tissue preservation area. Subgroup analyses suggested an association of locomotor recovery with riluzole dose. Network meta-analysis showed that 5 mg/kg riluzole exhibited greater protection than 2.5 and 8 mg/kg riluzole. Collectively, this review suggests that riluzole has a protective effect on SCI, with good safety and a clear mechanism of action and may be suitable for future clinical trials or applications. However, animal results should be interpreted with caution given the known limitations in animal experimental design and methodological quality.

Melatonin and cortisol in individuals with spinal cord injury

STUDY OBJECTIVES

The aim of this study was to investigate circadian rhythm and sleep complaints in individuals with spinal cord injury (SCI) as determined by diurnal saliva melatonin and cortisol as well as activity measurements and subjective sleep quality.

METHODS

Fourteen patients with cervical SCI (cSCI), six patients with thoracic SCI (tSCI) and eight able-bodied controls all underwent two consecutive weeks wearing a wrist actigraph in addition to filling out a sleep diary. During one 24-h period, cortisol and melatonin were measured at 4-h intervals. Furthermore, participants' sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) and their overall daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS).

RESULTS

The cSCI group demonstrated lower melatonin levels compared with the tSCI group and the controls at the 24:00 and 04:00 time points. Moreover, at one time point the tSCI group had a higher cortisol level than the cSCI group and the controls. In addition, baseline systolic blood pressure and oxygen saturation were significantly lower in the cSCI group. No differences were found in activity measurements or self-reported sleep quality.

CONCLUSIONS

Individuals with cSCI demonstrate reduced melatonin secretion compared with tSCI individuals, but not in other circadian measures. This supports an involvement of melatonergic cervical fibers associated with the cervical lesion.

Melatonin for the treatment of spinal cord injury

Spinal cord injury (SCI) from trauma or disease severely impairs sensory and motor function. Neurorehabilitation after SCI is a complex medical process that focuses on improving neurologic function and repairing damaged connections in the central nervous system. An increasing number of preclinical studies suggest that melatonin may be useful for the treatment of SCI. Melatonin is an indolamine that is primarily secreted by the pineal gland and known to be regulated by photoperiodicity. However, it is also a versatile hormone with antioxidative, antiapoptotic, neuroprotective, and anti-inflammatory properties. Here, we review the neuroprotective properties of melatonin and the potential mechanisms by which it might be beneficial in the treatment of SCI. We also describe therapies that combine melatonin with exercise, oxytetracycline, and dexamethasone to attenuate the secondary injury after SCI and limit potential side effects. Finally, we discuss how injury at different spinal levels may differentially affect the secretion of melatonin.

Melatonin supplementation in patients with complete tetraplegia and poor sleep

People with complete tetraplegia have interrupted melatonin production and commonly report poor sleep. Whether the two are related is unclear. This pilot study investigated whether nightly supplementation of 3 mg melatonin would improve objective and subjective sleep in tetraplegia. Five participants with motor and sensory complete tetraplegia ingested 3 mg melatonin (capsule) two hours prior to usual sleep time for two weeks. Full portable sleep studies were conducted in participants' homes on the night before commencing melatonin supplementation (baseline) and on the last night of the supplementation period. Endogenous melatonin levels were determined by assaying saliva samples collected the night of (just prior to sleep) and morning after (upon awakening) each sleep study. Prior to each sleep study measures of state sleepiness and sleep behaviour were collected. The results showed that 3 mg of melatonin increased salivary melatonin from near zero levels at baseline in all but one participant. A delay in time to Rapid Eye Movement sleep, and an increase in stage 2 sleep were observed along with improved subjective sleep experience with a reduction in time to fall asleep, improved quality of sleep and fewer awakenings during the night reported. Daytime sleepiness increased however. A randomised, placebo controlled trial with a larger sample is required to further explore and confirm these findings.