Melatonin treatment protects against spinal cord injury induced functional and biochemical changes in rat urinary bladder

The effect of melatonin administration on motor recovery after spinal cord injury in animal models: a systematic review and meta-analysis

STUDY DESIGN*: Systematic review and meta-analysis.

OBJECTIVES

In this study, the effects of the antioxidant melatonin on motor function after spinal cord injury were investigated in preclinical studies.

SETTING

IRAN METHODS: The search strategy was designed based on keywords related to melatonin and spinal cord injury. The primary screening was based on title and abstract, and the secondary screening was based on the full text of the articles. After extracting data from the articles, statistical analysis was performed using STATA software. Standardized mean differences were used to analyze the results of the included studies. Subgroup analysis and quality control of articles were also performed.

RESULTS

Based on the results of 29 separate experiments, melatonin showed a significant strong effect compared to the untreated group. The results showed that IP injection and multiple administrations days had the strong effect in the first three days as well as after 3-4 weeks. But more studies are needed to draw conclusions about its longer term effects. The analysis of MDA, SOD and GSH redox factors showed that the amount of MDA decreased and the amount of GSH increased in the treated animals. Also, the inflammatory factors IL-1Β and TNF-α as well as apoptosis and the rate of neuronal cell death, were reduced in animals that received melatonin, while the number of viable neurons was increased in melatonin treated animals.

CONCLUSION

Melatonin is an antioxidant supplement, which can be considered for clinical trials in human SCI patients.

SPONSORSHIP

IRAN University of medical sciences.

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.

Melatonin restores endoplasmic reticulum homeostasis to protect injured neurons in a rat model of chronic cervical cord compression

Cervical spondylotic myelopathy (CSM) refers to a chronic injury of the cervical cord caused by cervical intervertebral disc degeneration. Endoplasmic reticulum (ER) homeostasis is essential to counteract neuronal apoptosis. ER stress, an integral part of ER homeostasis, was observed in a rat model of chronic cervical cord compression in our previous study. However, the correlation between ER homeostasis and CSM remains unknown. The antioxidant melatonin is known to exert therapeutic effects in acute spinal cord injury, but the specific effects and their potential mechanisms in the pathological processes of CSM require further exploration. The present study hypothesized that ER homeostasis is essential for neuronal apoptosis in the CSM and that melatonin maintains this homeostasis. The results showed that ER stress led to neuronal apoptosis in rats with chronic cervical cord compression. Conversely, melatonin attenuates protein kinase R-like ER kinase-eukaryotic initiation factor 2α-C/EBP-homologous protein, inositol-requiring enzyme 1, and transcription factor 6 signaling pathways to release ER stress and prevents Bax translocation to the mitochondrion, thereby promoting motor recovery and protecting neurons in vivo. It also rescued primary rat cortical neurons from ER stress-induced glutamate toxicity in vitro. Moreover, melatonin remodels the ER morphology and restores homeostasis via ER-phagy in injured neurons. FAM134B, CCPG1, RTN3, and Sec. 62 are four known ER-phagy receptors. In this study, Sec. 62 was identified as a key melatonin factor in promoting ER-phagy and restoring ER homeostasis in damaged neurons in vivo and in vitro. In conclusion, melatonin suppresses neuronal apoptosis by reducing ER stress and promoting ER-phagy to restore ER morphology and homeostasis. The current results suggested that melatonin is a promising treatment for CSM owing to its restorative effect on ER homeostasis; however, well-designed randomized controlled trials must be carried out to further investigate its clinical effects.

The effect of amino acids on the bladder cycle: a concise review

The human bladder maintains a cycle of filling, storing, and micturating throughout an individual's lifespan. The cycle relies on the ability of the bladder to expand without increasing the intravesical pressure, which is only possible with the controlled relaxation of well-complaint muscles and the congruously organized construction of the bladder wall. A competent bladder outlet, which functions in a synchronous fashion with the bladder, is also necessary for this cycle to be completed successfully without deterioration. In this paper, we aimed to review the contemporary physiological findings on bladder physiology and examine the effects of amino acids on clinical conditions affecting the bladder, with special emphasis on the available therapeutic evidence and possible future roles of the amino acids in the treatment of the bladder-related disorders.

Melatonin as a promising modulator of aging related neurodegenerative disorders: Role of microRNAs

One of the host risk factors involved in aging-related diseases is coupled with the reduction of endogenous melatonin (MLT) synthesis in the pineal gland. MLT is considered a well-known pleiotropic regulatory hormone to modulate a multitude of biological processes such as the regulation of circadian rhythm attended by potent anti-oxidant, anti-inflammatory, and anti-cancer properties. It has also been established that the microRNAs family, as non-coding mRNAs regulating post-transcriptional processes, also serve a crucial role to promote MLT-related advantageous effects in both experimental and clinical settings. Moreover, the anti-aging impact of MLT and miRNAs participation jointly are of particular interest, recently. In this review, we aimed to scrutinize recent advances concerning the therapeutic implications of MLT, particularly in the brain tissue in the face of aging. We also assessed the possible interplay between microRNAs and MLT, which could be considered a therapeutic strategy to slow down the aging process in the nervous system.

Melatonin exerts neuroprotection in a chronodisrupted rat model through reduction in oxidative stress and modulation of autophagy

Circadian disruption due to artificial light affects cellular redox homeostasis and may lead to neurodegenerative diseases. The aim of the present study was to investigate the effect of continuous light exposure (CLE) and continuous dark exposure (CDE) along with melatonin supplementation on neuronal redox status, mitochondrial complexes, membrane bound transporters, inflammation, autophagy and neurodegeneration in chronodisrupted model of rat. In the study artificial light of white LED bulb with 500 lux intensity was used. Melatonin (10 mg/kg b.w., orally) was supplemented to control and CLE groups for 10 days. Standard protocols were employed to measure pro-oxidants, non-enzymatic antioxidants, and mitochondrial complexes in brain tissues. Membrane-bound ion transporter activities were evaluated in the crude synaptosomes. Gene expression analysis was performed to assess the expression of inflammatory, autophagy and neuronal marker genes. Histopathological changes in cerebral cortex and different hippocampus regions of the brain were studied. Melatonin exerted a significant normalization of redox status biomarkers in brain tissue. Further melatonin restored the activities of mitochondrial complexes and synaptosomal membrane bound ion transporters. RT-PCR data revealed that melatonin downregulated the expression of inflammatory (TNF-α, IL-6) autophagy (Atg-3, Beclin-1) and neurodegenerative genes (Ngb and NSE) in CLE group. Melatonin also preserved the histology architecture in cerebral cortex and hippocampus. Our results indicate that melatonin exerts a potent neuroprotective effect through reduction of oxidative stress, inflammation and autophagy. Melatonin supplementation might be a promising neurotherapeutic in the treatment neurodegenerative disorders caused by circadian disturbances.

Therapeutic approaches of trophic factors in animal models and in patients with spinal cord injury

Trophic factors are naturally produced by different tissues that participate in several functions such as the intercellular communication, in the development, stability, differentiation and regeneration at the cellular level. Specifically, in the case of spinal injuries, these factors can stimulate neuronal recovery. They are applied both in experimental models and in clinical trials in patients. The trophic factors analysed in this review include gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), growth hormone (GH), melatonin, oestrogens, the family of fibroblast growth factors (FGFs), the family of neurotrophins and the glial cell-derived neurotrophic factor (GDNF). There are some trophic (neurotrophic) factors that already been tested in patients with spinal cord injury (SCI), but only shown partial recovery effect. It is possible that, the administration of these trophic factors together with physical rehabilitation, act synergistically and, therefore, significantly improve the quality of life of patients with SCI.

Retracted Article: Melatonin protects spinal cord injury by up-regulating IGFBP3 through the improvement of microcirculation in a rat model

The present study was aimed at the investigation of the effects of melatonin on spinal cord injury (SCI) and the role of IGFBP3 in SCI both in vivo and in vitro. The rats received treatment with 100 mg kg-1 melatonin or both melatonin and pGenesil-1-si-IGFBP3 (50 µg per g bw) after SCI surgery. The motor function in rats was measured using the Basso-Beattie-Bresnahan (BBB) scale score; perfusion vessel area was determined by injecting FITC-conjugated lycopersicon esculentum agglutinin lectin (FITC-LEA), whereas the blood-spinal cord barrier permeability was measured using Evans blue. The pericytes were isolated, and the cells were cultured under hypoxia, treated with melatonin or transfected with si-IGFBP3. RT-qPCR and western blotting were conducted for the determination of IGFBP3, VEGF, MMP-2, ICAM-1 and Ang1. The expression of IGFBP3 was significantly down-regulated in the SCI rats, and melatonin significantly enhanced the IGFBP3 level. Melatonin improved the motor function, reduced the neuron injury, and improved the microcirculation in rats. However, the down-regulation of IGFBP3 significantly reversed these effects. Moreover, in both the SCI rat spinal cord tissues and the in vitro pericytes under hypoxia, the expressions of IGFBP3 and Ang1 were significantly down-regulated, whereas those of the proteins MMP-2, VEGF and ICAM-1 were significantly up-regulated, and melatonin dramatically inhibited these changes. Melatonin could protect the rats from SCI by improving the microcirculation through the up-regulation of IGFBP3.

Melatonin improves functional recovery in female rats after acute spinal cord injury by modulating polarization of spinal microglial/macrophages

Spinal cord injury (SCI) is a devastating neurological disorder, but few drugs have proven to be effective for its treatment. Neuroinflammation exaggerates the secondary injury subsequent to trauma. Emerging evidence suggests that melatonin may help protect neural tissue against secondary injury after SCI, but the underlying mechanisms remain elusive. Microglial/macrophages polarization plays an important role in regulating immune responses. To examine whether melatonin exerts neuroprotective effects after acute SCI by regulating microglial/macrophages polarization in the spinal cord, we administered intraperitoneal injections of melatonin (50 mg/kg) in female rats immediately after SCI and then daily for seven consecutive days (n = 6). Compared with the vehicle-treated group (n = 6), the melatonin-treated group exhibited a greater Basso, Beattie, and Bresnahan locomotor rating score, smaller spinal cavity, and less cleaved caspase 3 immunofluorescence staining in the injured spinal segments. Real-time PCR data revealed decreases in the expression levels of M1 microglia phenotypic markers and increases in M2 markers in the spinal cord of melatonin-treated SCI rats, as compared to levels in the vehicle-treated group. Melatonin increased the number of CD206⁺ and Arg1⁺ cells, decreased the number of CD16⁺ and iNOS⁺ cells and reduced the levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in the spinal cord tissue of female SCI rats. Current findings suggest that melatonin may inhibit pro-inflammatory responses and promote M2 polarization of microglial/macrophages in the spinal cord in the early stage of SCI, facilitating functional recovery. Accordingly, melatonin may represent a promising therapeutic candidate for acute SCI.

Native High-Density Lipoprotein and Melatonin Improve Platelet Response Induced by Glycated Lipoproteins

Activated platelets and glycated lipoproteins are responsible for atherothrombosis in diabetics. Melatonin and native high-density lipoproteins are crucial in the preservation of pro/oxidant-antioxidant balance. The aim of the present study was to investigate the in vitro effects of native high-density lipoproteins and melatonin on altering the platelet response induced by glycated lipoproteins. Low-density lipoproteins and high-density lipoproteins were purified from plasma by ultracentrifugation and were glycated with glucose for three weeks. After incubation with or without melatonin/or native highdensity lipoproteins, low-density lipoproteins, glycated low-density lipoproteins/glycated high-density lipoproteins were added to ADP-induced platelets. Oxidative parameters, caspase-3/9 and nitric oxide levels were measured spectrophotometrically; CD62-P/ annexin-V expression was determined by flow cytometry. In glycated low-density lipoprotein/glycated high-density lipoprotein-treated groups, platelet malondialdehyde/ protein carbonyl, P-selectin, annexin-V, caspase-3/9 levels were increased (ranging from P < 0.001 to P < 0.01); glutathione and nitric oxide levels were reduced (ranging from P < 0.001 to P < 0.01). In glycated low-density lipoprotein/glycated high-density lipoprotein-treated groups, melatonin treatment reduced malondialdehyde, protein carbonyl, CD62-P, annexin-V and caspase-3/9 (P < 0.001, P < 0.01) levels and elevated nitric oxide (only glycated low-density lipoproteins). In glycated low-density lipoprotein/glycated high-density lipoprotein-treated groups, native high-density lipoprotein treatment reduced malondialdehyde, protein carbonyl, annexin-V, caspase-3/9 levels (P < 0.001, P < 0.01) and increased glutathione; nitric oxide levels (only with gly-HDL). Both melatonin and high-density lipoproteins should be regarded as novel promising mechanism-based potential therapeutic targets to prevent atherothrombosis in diabetics.

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.

Psychological and Physical Environmental Factors in the Development of Incontinence in Adults and Children: A Comprehensive Review

The aim of this review was to identify etiological environmental factors related to incontinence in children and adults. A variety of etiological environmental factors for the development of incontinence were identified. In children, these encompass stressful life events and trauma, family dysfunction, parental psychopathology, school-related stressors, toilet or "potty" training, fluid consumption habits, housing conditions, and the availability of toilets. In adults, physical exercise, obesity, working conditions, fluid intake, and the availability of toilets play a role. Intervening variables such as hormonal variations due to work shifts have also been identified as influencing the likelihood of incontinence. Current research suggests that environmental factors influence the development of incontinence in children and adults. The interactions between biological factors, the immediate environment, and intervening variables need to be explored in greater detail. Practical solutions to reduce barriers to adequate fluid intake and healthy toileting habits should be implemented in school and work settings.

Melatonin prevents blood vessel loss and neurological impairment induced by spinal cord injury in rats

BACKGROUND

Melatonin can be neuroprotective in models of neurological injury, but its effects on blood vessel loss and neurological impairment following spinal cord injury (SCI) are unclear. Our goal herein was to evaluate the possible protective action of melatonin on the above SCI-induced damage in rats.

MATERIALS AND METHODS

Sixty-three female Sprague-Dawley rats were randomly divided into three equal groups: sham, SCI and melatonin groups. Melatonin (10 mg/kg) was injected intraperitoneally and further administered twice a day at indicated time after a moderate injury at T10 in melatonin group. Blood vessel was assessed by CD31staining and FITC-LEA, the permeability of blood-spinal cord barrier (BSCB) was detected by Evan's Blue. Neuron was assessed by NeuN staining and the expression of Nissl bodies in the neurons was assessed by Nissl staining. The expressions of brain-derived neurotrophic factor (BDNF), synapsin I, or growth associated protein-43 (GAP-43) in the spinal cord and hippocampus were evaluated by Western blotting.

RESULTS

At 7 days post-injury, melatonin treatment rescued blood vessels, increased CD31 levels, ameliorated BSCB permeability. Additionally, melatonin significantly increased the number of neurons and the expression of Nissl bodies in neurons at the injury epicenter. Furthermore, our data showed that SCI reduced levels of the molecular substrates of neurological plasticity, including BDNF, synapsin I, or GAP-43 in the spinal cord and hippocampus. Melatonin treatment partially prevented these reductions.

CONCLUSION

The neuroprotective effect of melatonin was associated with melioration of the microcirculation in the spinal cord and reduction of neurological impairment in the spinal cord and brain.

Combination of melatonin and Wnt-4 promotes neural cell differentiation in bovine amniotic epithelial cells and recovery from spinal cord injury

Although melatonin has been shown to exhibit a wide variety of biological functions, its effects on promoting differentiation of neural cells remain unknown. Wnt signaling mediates major developmental processes during embryogenesis and regulates maintenance, self-renewal, and differentiation of adult mammalian stem cells. However, the role of the noncanonical Wnt pathway during neurogenesis remains poorly understood. In this study, the amniotic epithelial cells ( AECs) were isolated from bovine amnion and incubated with various melatonin concentrations (0.01, 0.1, 1, 10, or 100 μm) and 5 × 10(-5) m all-trans retinoic acid (RA) for screening optimum culture medium of neural differentiation, compared with each groups, 1 μm melatonin and 5 × 10(-5) m RA were selected to induce neural differentiation of AECs, and then siMT1, siMT2, oWnt-4, and siWnt-4 were expressed in AECs to research role of these genes in neural differentiation. Efficiency of neural differentiation was evaluated after expressed above genes using flow cytometry. Cell function of neural cells was demonstrated in vivo using spinal cord injury model after cell transplantation, and damage repair of spinal cord was assessed using cell tracking and Basso, Beattie, Bresnahan Locomotor Rating Scale scores. Results demonstrated that melatonin stimulated melatonin receptor 1, which subsequently increased bovine amniotic epithelial cell vitality and promoted differentiation into neural cells. This took place through cooperation with Wnt-4. Additionally, following cotreatment with melatonin and Wnt-4, neurogenesis gene expression was significantly altered. Furthermore, single inhibition of melatonin receptor 1 or Wnt-4 expression decreased expression of neurogenesis-related genes, and bovine amniotic epithelial cell-derived neural cells were successfully colonized into injured spinal cord, which suggested participation in tissue repair.

The neuroprotective and anti-apoptotic effects of melatonin on hemolytic hyperbilirubinemia-induced oxidative brain damage

Melatonin exerts protection in several inflammatory and neurodegenerative disorders. To investigate the neuroprotective effects of melatonin in an experimental hemolysis-induced hyperbilirubinemia, newborn Sprague-Dawley rats (25-40 g, n = 72) were injected with phenylhydrazine hydrochloride (PHZ; 75 mg/kg) and the injections were repeated at the 24th hour. Rats were treated with saline or melatonin (10 mg/kg) 30 min before the first and second PHZ injections and 24 h after the 2nd PHZ injections. Control rats (n = 24) were injected with saline, but not PHZ. At sixth hours after the last injections of saline or melatonin, all rats were decapitated. Tumor necrosis factor (TNF)-α, IL-1β, IL-10 and brain-derived neurotrophic factor (BDNF) and S100B levels in the plasma were measured. Brain tissue malondialdehyde (MDA), glutathione (GSH) levels and myeloperoxidase (MPO) activities were measured, and brain tissues were evaluated for apoptosis by TUNEL method. In the saline-treated PHZ group, hemoglobin, hematocrit levels were reduced, and total/direct bilirubin levels were elevated when compared to control group. Increased plasma TNF-α, IL-1β levels, along with decreased BDNF, S100B and IL-10 values were observed in the saline-treated PHZ group, while these changes were all reversed in the melatonin-treated group. Increased MDA levels and MPO activities in the brain tissues of saline-treated hyperbilirubinemic rats, concomitant with depleted brain GSH stores, were also reversed in the melatonin-treated hyperbilirubinemic rats. Increased TUNEL(+) cells in the hippocampus of saline-treated PHZ group were reduced by melatonin treatment. Melatonin exerts neuroprotective and anti-apoptotic effects on the oxidative neuronal damage of the newborn rats with hemolysis and hyperbilirubinemia.

Antioxidant Agent Quercetin Prevents Impairment of Bladder Tissue Contractility and Apoptosis in a Rat Model of Ischemia/Reperfusion Injury

OBJECTIVES

To examine the possible protective effect of quercetin (QT), which is well known for its antioxidant and protective effects in circumstances of oxidative stress, on urinary bladder tissue in a rat model of ischemia/reperfusion (I/R) injury, which is a known factor for the development of lower urinary tract dysfunction partly mediated by the generation of free radicals causing oxidative damage.

METHODS

Thirty male Sprague-Dawley rats were subjected to I/R injury through clamping the abdominal aorta for 30 min and then allowing reperfusion for the next 60 min. Quercetin (20 mg/kg; subcutaneously) or vehicle were given before ischemia and just before reperfusion. Findings of the isometric contraction studies in the organ bath and of the histological examinations along with oxidative stress markers were evaluated in bladder tissues.

RESULTS

Increased malondialdehyde (MDA) levels and myeloperoxidase (MPO) activities and decreased glutathione (GSH) levels and superoxide dismutase (SOD) activities in the I/R group were reduced by QT treatment. In the I/R group, pro-apoptotic marker caspase-3 was increased and anti-apoptotic bcl-2 protein was decreased, while QT treatment significantly reversed these parameters. In the I/R group contractile responses of the bladder strips to carbachol were significantly lower than those of the control group, which were reversed by QT treatment.

CONCLUSION

Quercetin treatment protects bladder tissue contractility against acute I/R injury by decreasing oxidative stress and apoptosis induced by I/R.

Melatonin and Its Role in Lower Urinary Tract Function: An Article Review

This article reviewed the results of studies done on animals that assessed effects of melatonin on bladder function. Melatonin does not change strip relaxation on its own. However, pre-treatment with melatonin decreases contractile responses induced by phenylephrine, acetylcholine, bethanechol and KCl in a dose-dependent manner. The contractile responses induced by the direct calcium channel openers are significantly decreased by melatonin pre-treatment. It also binds to Ca(2+)-activated calmodulin, and prevents it from activating myosin light-chain kinase. It may have direct effects on ion channels which are responsible for regulating bladder contraction. Its other mode of action on bladder occurs via the brain GABAA receptor. Melatonin is an antioxidant. In bladder, treatment with melatonin prevents elevations in malondialdehyde levels, reverses changes in glutathione levels, and decreases myeloperoxidase levels compared with oxidative injury. It can normalize age induced bladder dysfunction through its antioxidant effects, inhibiting smooth muscle contractility directly and restoring impaired contractility via normalization of Ca(2+) handling and sensitizations pathways. It attenuates the severity of cystitis and inflammation. Mast cell proliferation and activation are increased in cystitis, but decrease by melatonin treatment. Also, there is a decrease in expression levels of pro-inflammatory cytokines after melatonin treatment.

Reduction in traumatic brain injury-induced oxidative stress, apoptosis, and calcium entry in rat hippocampus by melatonin: Possible involvement of TRPM2 channels

Melatonin, which is a very effective reactive oxygen species (ROS) scavenger, acts through a direct reaction with free radicals. Ca(2+) entry induced by traumatic brain injury (TBI) has deleterious effects on human hippocampal function. TRPM2 is a Ca(2+) permeable non-selective channel in hippocampal neurons, and its activation of during oxidative stress has been linked to cell death. Despite the importance of oxidative stress in TBI, its role in apoptosis and Ca(2+) entry in TBI is poorly understood. Therefore, we tested the effects of melatonin on apoptosis, oxidative stress, and Ca(2+) entry through the TRPM2 channel in the hippocampal neurons of TBI-induced rats. Thirty-two rats were divided into the following four groups: control, melatonin, TBI, and TBI + melatonin groups. Melatonin (5 mg/kg body weight) was intraperitoneally given to animals in the melatonin group and the TBI + melatonin group after 1 h of brain trauma. Hippocampal neurons were freshly isolated from the four groups, incubated with a nonspecific TRPM2 blocker (2-aminoethyl diphenylborinate, 2-APB), and then stimulated with cumene hydroperoxide. Apoptosis, caspase-3, caspase-9, intracellular ROS production, mitochondrial membrane depolarization and intracellular free Ca(2+) ([Ca(2+)]i) values were high in the TBI group, and low in the TBI + melatonin group. The [Ca(2+)]i concentration was decreased in the four groups by 2-APB. In our TBI experimental model, TRPM2 channels were involved in Ca(2+) entry-induced neuronal death, and the negative modulation of the activity of this channel by melatonin pretreatment may account for the neuroprotective activity of TRPM2 channels against oxidative stress, apoptosis, and Ca(2+) entry.

Role of melatonin in traumatic brain injury and spinal cord injury

Brain and spinal cord are implicated in incidences of two of the most severe injuries of central nervous system (CNS). Traumatic brain injury (TBI) is a devastating neurological deficit involving primary and secondary injury cascades. The primary and secondary mechanisms include complex consequences of activation of proinflammatory cytokines, cerebral edema, upregulation of NF-κβ, disruption of blood-brain barrier (BBB), and oxidative stress. Spinal cord injury (SCI) includes primary and secondary injury cascades. Primary injury leads to secondary injury in which generation of free radicals and oxidative or nitrative damage play an important pathophysiological role. The indoleamine melatonin is a hormone secreted or synthesized by pineal gland in the brain which helps to regulate sleep and wake cycle. Melatonin has been shown to be a versatile hormone having antioxidative, antiapoptotic, neuroprotective, and anti-inflammatory properties. It has a special characteristic of crossing BBB. Melatonin has neuroprotective role in the injured part of the CNS after TBI and SCI. A number of studies have successfully shown its therapeutic value as a neuroprotective agent in the treatment of neurodegenerative diseases. Here in this review we have compiled the literature supporting consequences of CNS injuries, TBI and SCI, and the protective role of melatonin in it.

Neurotrophin signaling and visceral hypersensitivity

Neurotrophin family are traditionally recognized for their nerve growth promoting function and are recently identified as crucial factors in regulating neuronal activity in the central and peripheral nervous systems. The family members including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are reported to have distinct roles in the development and maintenance of sensory phenotypes in normal states and in the modulation of sensory activity in disease. This paper highlights receptor tyrosine kinase (Trk) -mediated signal transduction by which neurotrophins regulate neuronal activity in the visceral sensory reflex pathways with emphasis on the distinct roles of NGF and BDNF signaling in physiologic and pathophysiological processes. Viscero-visceral cross-organ sensitization exists widely in human diseases. The role of neurotrophins in mediating neural cross talk and interaction in primary afferent neurons in the dorsal root ganglia (DRG) and neurotrophin signal transduction in the context of cross-organ sensitization are also discussed.

Protective effects of melatonin against spinal cord injury induced oxidative damage in rat kidney: A morphological and biochemical study

Spinal cord injury (SCI) induced oxidative stress affects multiple organ systems including the kidney. We studied the possible protective effects of melatonin on SCI-induced oxidative damage in renal tissues of rats. Wistar albino rats (n = 24) were exposed to SCI and divided into vehicle- or melatonin-treated SCI groups. Melatonin was administred intraperitoneally at a dose of 10 mg/kg for seven days. Renal tissues were investigated by light and electron microscopy. Furthermore, tissue malondialdehyde (MDA) and glutathione (GSH) levels and myeloperoxidase (MPO) and superoxide dismutase (SOD) activities were also determined. In the vehicle-treated SCI group, the renal histology was disturbed compared to controls, whereas the melatonin-treated SCI group showed significantly reduced degeneration of renal tissue as seen by both light and electron microscopy. MDA levels, MPO and SOD activities were increased and GSH levels were decreased in the vehicle-treated SCI group compared to controls. On the other hand, decreased MDA levels and MPO activities and increased GSH levels were observed in the melatonin-treated SCI group compared to vehicle-treated SCI group. These results showed that experimentally induced SCI caused oxidative stress in the rat kidney, whereas melatonin treatment reduced oxidative stress, suggesting that it may be used as a complementary therapy of renal problems occurring following SCI.

Montelukast inhibits caspase-3 activity and ameliorates oxidative damage in the spinal cord and urinary bladder of rats with spinal cord injury

Spinal cord injury (SCI) leads to an inflammatory response that generates substantial secondary damage within the tissue besides the primary damage. Leukotrienes are biologically active 5-lipoxygenase products of arachidonic acid metabolism that are involved in the mediation of various inflammatory disorders including SCI. In this study, we investigated the possible protective effects of montelukast, a leukotriene receptor blocker, on SCI-induced oxidative damage. Wistar albino rats (n=24) were divided randomly as control, vehicle- or montelukast (10mg/kg, ip)-treated SCI groups. To induce SCI, a standard weight-drop method that induced a moderately severe injury at T10 was used. Vehicle or montelukast were administered to the injured animals 15 min after injury. At seven days post-injury, neurological examination was performed and rats were decapitated. Blood samples were taken to evaluate leukotriene B4 levels, and pro-inflmamatory cytokines (TNF-α, IL-1β) while in spinal cord and urinary bladder samples malondialdehyde (MDA), glutathione (GSH), luminol chemiluminescence (CL) levels and myeloperoxidase (MPO) and caspase-3 activities were determined. Tissues were also evaluated histologically. SCI caused significant decreases in tissue GSH, which were accompanied with significant increases in luminol CL and MDA levels and MPO and caspase-3 activities, while pro-inflammatory cytokines in the plasma were elevated. On the other hand, montelukast treatment reversed these parameters and improved histological findings. In conclusion, SCI caused oxidative tissue injury through the activation of pro-inflammatory mediators and by neutrophil infiltration into tissues, and the neuroprotective and antiapoptotic effects of montelukast are mediated by the inhibition of lipid peroxidation, neutrophil accumulation and pro-inflammatory cytokine release. Moreover, montelukast does not only exert antioxidant and antiapoptotic effects on the spinal cord, but it has a significant impact on the bladder tissue damage secondary to SCI.