Protective effect of melatonin on experimental spinal cord ischemia

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.

The effects of apigenin administration on the inhibition of inflammatory responses and oxidative stress in the lung injury models: a systematic review and meta-analysis of preclinical evidence

BACKGROUND/OBJECTIVE

Apigenin is a member of the flavonoid family that can regulate various biological processes, which is characterized as a treatment of different inflammatory disorders and pathological problems associated with oxidative stress (OS). Recent research has focused on apigenin immunomodulatory properties as a potential treatment for different types of lung injuries. This meta-analysis was designed to determine the impact of apigenin treatment on inflammatory markers and OS parameters in animal models of lung injuries.

METHODS

The comprehensive literature search was conducted using electronic databases such as Google Scholar, PubMed, Web of Science, Scopus, and Embase up to August 2021. To assess apigenin's effect on inflammatory mediators and OS biomarkers in lung injury animal models, we used the I² statistic to determine the heterogeneity. We then pooled data as standardized mean difference (SMD) with a 95% confidence interval (CI).

RESULTS

Our meta-analysis of the pooled data for inflammatory biomarkers demonstrated that the apigenin administration significantly decreased the NF-κB expression (SMD - 1.60, 95% CI [- 2.93 to - 0.26]; I² = 89.0%, p < 0.001), IL-1β (SMD - 4.30, 95% CI [- 6.24 to - 2.37]; I² = 67.3%, p = 0.047), IL-6 (SMD - 4.10, 95% CI [- 5.04 to - 3.16]; I² = 72.6%, p < 0.001), TNF-α (SMD - 3.74, 95% CI [- 4.67 to - 2.82]; I² = 84.1%, p < 0.001), and TNF-α gene expression (SMD - 3.44, 95% CI [- 4.44 to - 2.43]; I² = 0.0%, p = 0.622). This study also indicated the efficacy of apigenin in increasing the level of CAT (SMD 4.56, 95% CI [3.57 to 5.55]; I² = 15.3%, p = 3.15), GSH (SMD 5.12, 95% CI [3.53 to 6.70]; I² = 77.6%, p < 0.001), and SOD (SMD 3.45, 95% CI [2.50 to 4.40]; I² = 79.2%, p < 0.001), and decreasing the level of MDA (SMD - 3.87, 95% CI [- 5.25 to - 2.49]; I² = 80.3%, p < 0.001) and MPO (SMD - 4.02, 95% CI [- 5.64 to - 2.40]; I² = 88.9%, p < 0.001), TGF- β (SMD - 3.81, 95% CI [- 4.91 to - 2.70]; I² = 73.4%, p = 0.001) and W/D level (SMD - 3.22, 95% CI [- 4.47 to - 1.97]; I² = 82.1%, p < 0.001) than control groups.

CONCLUSION

Overall, our findings showed the immunomodulatory potential of apigenin as an alternative treatment for the suppression of inflammatory responses and OS in different types of lung injury diseases. Nevertheless, due to the paucity of clinical studies, reliable preclinical models, and clinical settings, evaluating the influence of apigenin on lung injury is required in the future. Before conducting large-scale clinical trials, detailed human pharmacokinetic studies are also needed to establish dosage ranges and determine the initial safety and tolerability of apigenin.

Effect of Preoperative Administration of Oral Melatonin on Pneumatic Tourniquet-Induced Ischemia-Reperfusion Injury in Orthopedic Surgery of Lower Extremities: A Randomized Clinical Trial

Background

Ischemic reperfusion injury (IRI) causes cellular damage and dysfunction. The present study aimed to evaluate the effect of melatonin on pneumatic tourniquet-induced IRI in orthopedic surgery of the lower extremities.

Methods

A randomized clinical trial was conducted at Chamran Hospital, Shiraz University of Medical Sciences (Shiraz, Iran), from September to November 2019. The target population was patients scheduled for elective orthopedic surgery of the lower extremities. A total of 67 patients were randomly divided into two groups, placebo (n=34) and melatonin (n=33). The groups received 10 mg melatonin or placebo the night before surgery and two hours before surgery. Primary outcome variables were the serum levels of superoxide dismutase (SOD) and malondialdehyde (MDA). Hemodynamic parameters, sedation score, and drug side effects were also evaluated. Data were analyzed using SPSS version 21.0 software. P<0.05 was considered statistically significant.

Results

In the analysis phase, due to loss to follow-up (n=26), 41 patients divided into two groups of melatonin (n=20) and placebo (n=21) were evaluated. There was no significant difference in demographic data, duration of surgery (P=0.929), and tourniquet time (P=0.496) between the groups. The serum levels of SOD and MDA were not significantly different between the groups (P=0.866 and P=0.422, respectively), nor were the incidence of postoperative nausea (P=0.588) and patients' satisfaction (P=0.088). However, the postoperative sedation score and vomiting between the groups were significantly different (P<0.001).

Conclusion

Administration of 10 mg melatonin provided effective sedation, but had no significant effect on the serum levels of SOD and MDA, nor on pneumatic tourniquet-induced IRI in orthopedic surgery of the lower limbs.

Trial registration number

IRCT20141009019470N87.

Systematic review of melatonin levels in individuals with complete cervical spinal cord injury

Context: Pineal melatonin production is mediated by afferent signaling pathways that navigate through the cervicothoracic spinal cord. Melatonin profiles in individuals with complete cervical spinal cord injury (SCI) have not been systematically reviewed despite this proposed pathway. Objectives: The primary objective was to understand melatonin profiles in individuals with complete cervical SCI, as compared to healthy controls and those with thoracolumbar and incomplete cervical SCI. Secondary objectives were to understand the impact of injury chronicity and melatonin supplementation on melatonin values in adults with complete cervical SCI. Methods: This review (PROSPERO ID: CRD42017073767) searched several databases and gray literature sources from January 1978 to August 2017. Studies were eligible if they evaluated melatonin levels (blood, saliva or urinary metabolite measurements) in adults with complete cervical SCI. 390 studies were screened and 12 studies met final selection criteria. Given the heterogeneity in study designs, a narrative analysis was performed. Results: There is evidence that adults with complete cervical SCI have absent diurnal melatonin rhythms as compared to healthy controls and individuals with thoracolumbar SCI below T3. There is limited evidence comparing levels in individuals with incomplete tetraplegia. There is insufficient evidence describing profiles immediately (<2 weeks) after cervical SCI. Based on a limited number of studies, melatonin supplementation does not appear to improve sleep outcomes in adults with long-standing complete cervical SCI. Conclusions: Future research should explore melatonin levels acutely after cervical SCI and the impact of supplementation on non-sleep outcomes.

Protective Effect of Lycopene against Reperfusion Injury in Rats with Ovarian Torsion: A Biochemical and Histopathological Evaluation

Objective  The aim of our study was to evaluate the effect of two different doses of lycopene, an antioxidant, on experimentally induced ovarian ischemia/reperfusion (IR) injury in rat model.

Materials and Methods  Twenty-four female rats were randomly divided into four groups: sham operation (group 1), 3-hour ischemia, 3-hour reperfusion (IR) (group 2), and IR + 100 mg/kg lycopene (PO) (group 3), IR + 200 mg/kg of lycopene (group 4). The rats’ superoxide dismutase (SOD), myeloperoxidase (MPO) activities, malondialdehyde (MDA), and glutathione (GSH) levels were calculated. Ovarian tissue damage was assessed using a histopathological scoring system.

Results  Serum parameter levels and histological scores showed that treatment with lycopene may be conservative approach to prevent IR injury after the ovarian detorsion procedure.The improvement with lycopene was higher at 200 mg than at 100 mg. The MPO and MDA values were significantly lower in groups 3 and 4 as compared with group 2 ( p < 0.05), whereas the MPO and MDA values were lower in group 4 as compared with group 3.The SOD and GSH values were significantly higher in groups 3 and 4 as compared with group 2 ( p < 0.05), whereas the SOD and GSH values were higher in group 4 as compared with group 3.Tissue damage scores were elevated in the IR group compared with the sham group, but the treatment with different lycopene doses after reperfusion improved the histopathological tissue damage scores.

Conclusion  The results showed that lycopene treatment reduced ovarian IR damage. Antioxidant activity was found to increase in a dose-dependent manner. Lycopene treatment may be conservative approach for ovarian torsion patients after the detorsion procedure to prevent IR damage.

Protective effect of betaine against lead-induced testicular toxicity in male mice

Lead (Pb) is an environmental toxicant reported to impair male reproductive system. Betaine is a natural product which has promising beneficial effects against oxidative stress. In this experimental study, we evaluated the ameliorative effect of betaine on sperm quality and oxidative stress induced by lead (Pb) in the testis of adult male mice. Sixty male Kunming mice were divided equally into four groups: control group, betaine group (1% in drinking water), lead group (100 mg kg^-1  bw^-1  day^-1 ) and betaine + lead group. In the last group, mice were supplemented with betaine for two weeks prior to the initiation of lead treatment and concurrently during lead treatment for 3 weeks until sacrificed. Our results indicated that in the lead-administrated group, body weights together with sperm count were significantly decreased (p < .05). The numbers of abnormal sperms were found to be higher in lead-treated mice. The activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (Cat) were significantly reduced, while the level of malondialdehyde (MDA) content was increased in the testis tissue following lead treatment. The mRNA levels of antioxidant-related genes (SOD1, GPX1 and CAT) were significantly decreased in the lead group. Betaine enhanced these parameters in betaine + lead group. In testis histology span, Johnson score was decreased (p < .05) in lead group and co-treatment with betaine increased Johnson score significantly in betaine + lead group. These results indicate that betaine improves sperm quality and ameliorate oxidative damage in testis of mice exposed to lead.

Metformin Activates the Protective Effects of the AMPK Pathway in Acute Lung Injury Caused by Paraquat Poisoning

Objective

To observe whether metformin (MET) plays a protective role in acute lung injury (ALI) induced by paraquat (PQ) poisoning in rats by activating the AMPK/NF-κB signaling pathway.

Methods

PQ exposure was used to construct a rat model of ALI and a model of acute type II alveolar epithelial cell (RLE-6TN) injury, and MET intervention was performed. Rat lung tissue samples were collected to evaluate pathological changes in rat lung tissue, the oxidation index, and inflammatory factors; cell viability was detected by CCK-8 assays, and the protein expression levels of phospho-AMPK and phospho-NF-κBp65 in rat lung tissue and RLE-6TN cells were observed by Western blotting.

Results

Compared with the PQ group, the MET treatment group showed significantly (1) reduced lung wet/dry ratio (W/D: 4.67 ± 0.31 vs. 5.45 ± 0.40, P < 0.001), (2) reduced pathological changes in lung tissue, (3) decreased MDA levels (nmol/mg prot: 2.70 ± 0.19 vs. 3.08 ± 0.15, P < 0.001) and increased SOD and GSH-Px activities (U/mg prot: 76.17 ± 5.22 vs. 45.23 ± 6.58, 30.40 ± 2.84 vs. 21.00 ± 3.20; all P < 0.001) in lung tissue homogenate, (4) reduced levels of IL-1β, IL-6, and TNF-α in lung tissue homogenates (pg/mL: 47.87 ± 5.06 vs. 66.77 ± 6.55; 93.03 ± 7.41 vs. 107.39 ± 9.81; 75.73 ± 6.08 vs. 89.12 ± 8.94; all P < 0.001), (5) increased activity of RLE-6TN cells (%: 0.69 ± 0.09, 0.76 ± 0.06, and 0.58 ± 0.03 vs. 0.50 ± 0.05; all P < 0.05), (6) decreased protein levels of phospho-NF-κBp65 in lung homogenates and RLE-6TN cells (p-NF-κB/NF-κB: 0.47 ± 0.09 vs. 0.81 ± 0.13; 0.26 ± 0.07 vs. 0.79 ± 0.13; all P < 0.01), and (7) upregulated protein expression of phospho-AMPK in lung homogenates and RLE-6TN cells (p-AMPK/AMPK: 0.88 ± 0.05 vs. 0.36 ± 0.12; 0.93 ± 0.03 vs. 0.56 ± 0.15; all P < 0.01). After the addition of the AMPK inhibitor Compound C (Com C), the protein expression levels of phospho-AMPK and phospho-NF-κBp65 returned to baseline.

Conclusion

MET can effectively alleviate ALI induced by paraquat poisoning and increase the viability of cells exposed to paraquat. The mechanism may be related to the activation of the AMPK/NF-κB pathway, downregulation of inflammatory mediators such as IL-6 and TNF-α, and upregulation of the SOD and GSH-Px oxidation index, and these effects can be inhibited by the AMPK inhibitor Com C.

Baicalin Exerts Anti-Airway Inflammation and Anti-Remodelling Effects in Severe Stage Rat Model of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a worldwide epidemic. Current approaches are disappointing due to limited improvement of the disease development. The present study established 36-week side stream cigarette smoke induced rat model of COPD with advanced stage feature and evaluted the effects of baicalin on the model. Fifty-four Sprague–Dawley rats were randomly divided into six groups including room air control, cigarette smoke exposure, baicalin (40 mg/kg, 80 mg/kg, and 160 mg/kg), and budesonide used as a positive control. Rats were exposed to cigarette smoke from 3R4F research cigarettes. Pulmonary function was evaluated and pathological changes were also observed. Cytokine level related to airway inflammation and remodelling in blood serum, bronchoalveolar lavage fluid, and lung tissue was determined. Blood gases and HPA axis function were also examined, and antioxidant levels were quantified. Results showed that, after treatment with baicalin, lung function was improved and histopathological changes were ameliorated. Baicalin also regulated proinflammatory and anti-inflammatory balance and also airway remodelling and anti-airway remodelling factors in blood serum, bronchoalveolar lavage fluid, and lung tissue. Antioxidant capacity was also increased after treatment with baicalin in COPD rat model. HPA axis function was improved in baicalin treated groups as compared to model group. Therefore, baicalin exerts lung function protection, proinflammatory and anti-inflammatory cytokine regulation, anti-airway remodelling, and antioxidant role in long term CS induced COPD model.

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.

Comparison of the neuroprotective effects of brimonidine tartrate and melatonin on retinal ganglion cells

PURPOSE

We aimed to compare the neuroprotective effects of brimonidine tartrate (BRT) and melatonin (MEL) on retinal ganglion cells (RGCs) in a rat glaucoma model.

METHODS

Thirty-six adult Wistar albino rats were allocated into six groups: control (C), glaucoma (G), BRT, MEL, G + BRT and G + MEL. After establishing the glaucoma model, intraocular pressure (IOP) of all animals measured at day 4 and day 30 was compared statistically with day 0 and day 4, respectively. Prior to sacrification at day 30 for histological evaluation and TUNEL analysis, retrograde labeling of non-apoptotic RGCs with 3% Fluorogold was performed and RGCs were evaluated under fluorescein microscope.

RESULTS

IOP measurements at day 4 were significantly higher than basal measurements in all glaucoma groups. BRT alone induced a time-dependent decrease in IOP (p < 0.05), while MEL alone failed to reduce IOP. However, both BRT and MEL reduced IOP in the presence of glaucoma at day 30 (p < 0.05). BRT treatment significantly reversed the reduced non-apoptotic RGC counts (p < 0.01) and increased TUNEL-positive RGCs (p < 0.001) to control group levels in the presence of glaucoma. However, no statistical significance was found between groups G and G + MEL considering 3% Fluorogold-labeled cell counts and apoptotic index values.

CONCLUSION

Our study revealed that systemic administration of BRT also has an IOP reducing effect. MEL has no neuroprotective effect on RGCs; on the other hand, BRT acts as a neuroprotective agent against glaucomatous injury, when applied systemically.

Melatonin Inhibits Neural Cell Apoptosis and Promotes Locomotor Recovery via Activation of the Wnt/β-Catenin Signaling Pathway After Spinal Cord Injury

The spinal cord is highly sensitive to spinal cord injury (SCI) by external mechanical damage, resulting in irreversible neurological damage. Activation of the Wnt/β-catenin signaling pathway can effectively reduce apoptosis and protect against SCI. Melatonin, an indoleamine originally isolated from bovine pineal tissue, exerts neuroprotective effects after SCI through activation of the Wnt/β-catenin signaling pathway. In this study, we demonstrated that melatonin exhibited neuroprotective effects on neuronal apoptosis and supported functional recovery in a rat SCI model by activating the Wnt/β-catenin signaling pathway. We found that melatonin administration after SCI significantly upregulated the expression of low-density lipoprotein receptor related protein 6 phosphorylation (p-LRP-6), lymphoid enhancer factor-1 (LEF-1) and β-catenin protein in the spinal cord. Melatonin enhanced motor neuronal survival in the spinal cord ventral horn and improved the locomotor functions of rats after SCI. Melatonin administration after SCI also reduced the expression levels of Bax and cleaved caspase-3 in the spinal cord and the proportion of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) positive cells, but increased the expression level of Bcl-2. These results suggest that melatonin attenuated SCI by activating the Wnt/β-catenin signaling pathway.

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.

Senegenin Ameliorate Acute Lung Injury Through Reduction of Oxidative Stress and Inhibition of Inflammation in Cecal Ligation and Puncture-Induced Sepsis Rats

The purpose of this study was to assess the protective effect of senegenin on acute lung injury (ALI) in rats induced by sepsis. Rat ALI model was reproduced by cecal ligation and puncture (CLP). All rats were randomly divided into five groups: group 1 (control), group 2 (CLP), group 3 (CLP + senegenin 15 mg/kg), group 4 (CLP + senegenin 30 mg/kg), and group 5 (CLP + senegenin 60 mg/kg). CLP + senegenin groups received senegenin by gavage daily for consecutive 5 days, respectively, while the mice in control and CLP groups were given an equivalent volume of saline. We detected the lung wet/dry weight ratios and the histopathology of the lung. The levels of lung tissue myeloperoxidase (MPO), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) were determined. Meanwhile, the nuclear factor-kappa B (NF-κB) activation, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β) levels were studied. The results demonstrated that senegenin treatment significantly attenuated CLP-induced lung injury, including reduction of lung wet/dry weight ratio, protein leak, infiltration of leukocytes, and MPO activity. In addition, senegenin markedly decreased MDA content and increased SOD activity and GSH level. Serum levels of TNF-α and IL-1β were also decreased by senegenin administration. Furthermore, senegenin administration inhibited the nuclear translocation of NF-κB in the lungs. These findings indicate that senegenin exerts protective effects on CLP-induced septic rats. Senegenin may be a potential therapeutic agent against sepsis.

Effects of melatonin on severe crush spinal cord injury-induced reactive astrocyte and scar formation

The present work aimed at analyzing the effects of melatonin on scar formation after spinal cord injury (SCI). Upregulation of reactive astrocyte under SCI pathological conditions has been presented in several studies. It has been proved that the crucial factor in triggering this upregulation is proinflammatory cytokines. Moreover, scar formation is an important barrier to axonal regeneration through the lesion area. Melatonin plays an important role in reducing inflammation, but its effects on scar formation in the injured spinal cord remain unknown. Hence, we used the model of severe crush injury in mice to investigate the effects of melatonin on scar formation. Mice were randomly separated into four groups; SCI, SCI+Melatonin 1 (single dose), SCI+Melatonin 14 (14 daily doses), and control. Melatonin was administered by intraperitoneal injection (10 mg/kg) after injury. Immunohistochemical analysis, Western blot, and behavioral evaluation were used to explore the effects of melatonin after SCI for 14 days. The melatonin-treated mice presented higher expression of neuronal markers (P < 0.001). Remarkably, the inflammatory response appeared to be greatly reduced in the SCI+Melatonin 14 group (P < 0.001), which also displayed less scar formation (P < 0.05). These findings suggest that melatonin inhibits scar formation by acting on inflammatory cytokines after SCI. Overall, our results suggest that melatonin is a promising treatment strategy after SCI that deserves further investigation. © 2016 Wiley Periodicals, Inc.

Protective effects of ellagic acid and ozone on rat ovaries with an ischemia/reperfusion injury

AIM

This study investigated the effects of the antioxidant agents, ozone (O) and ellagic acid (EA), on ischemia/reperfusion (I/R) injuries developed from an ovarian torsion-detorsion model.

MATERIALS AND METHODS

Arteries in the left ovaries of rats were clamped for two hours to achieve torsion, and then the clamps were removed for a two-hour detorsion period. Thirty-five female Sprague-Dawley rats were randomly divided into five groups: control: administered only with anesthesia, rats were not subjected to torsion-detorsion; I/R: subjected to torsion and subsequent detorsion, without administering any treatment agent; and I/R + EA, I/R + O and I/R + O + EA: subjected to torsion and detorsion processes and administered with EA, O or EA + O at the 75th minute of torsion. The rats were then sacrificed under general anesthesia and the ovarian tissues were excised. The tissues were homogenized and levels of glutathione reductase, catalase, superoxide dismutase and malondialdehyde (MDA) were analyzed. Tissue damage was evaluated in terms of histopathological parameters, such as hemorrhage, congestion, edema and inflammation.

RESULTS

Antioxidant enzyme activity and MDA levels in the ovary tissue increased in the I/R group and decreased in the O, EA and O + EA groups (P < 0.05). Histopathological examination revealed that tissue damage in the O, EA and O + EA groups decreased in comparison with the I/R group (P < 0.05).

CONCLUSIONS

These biochemical and histopathological findings suggest that EA and O are effective against ovarian I/R injury.

Luteolin-induced protection of H₂O₂-induced apoptosis in PC12 cells and the associated pathway

Increasing evidence has indicated that the generation of reactive oxygen species (ROS) contributes to H2O2‑induced nerve injury. This may result in oxidative stress that leads to cell damage or death. Dietary or pharmaceutical augmentation of the endogenous antioxidant defense capacity is a potential means by which to prevent ROS‑induced damage. The aim of the current study was to investigate the effect of luteolin on H2O2‑induced cell apoptosis in cultured rat pheochromocytoma cells (PC12 cells) and to investigate the role of the phosphatidylinositol‑3‑kinase (PI3K)/protein kinase B (Akt) pathway on H2O2‑induced apoptosis. The results demonstrated that luteolin was able to inhibit the reduction in cell viability induced by H2O2. In addition, luteolin reduced ROS generation and lactate dehydrogenase release in H2O2‑treated PC12 cells. The levels of superoxide dismutase and glutathione peroxidase activity were increased following treatment with luteolin, however malondialdehyde levels were observed to be reduced. Additionally, luteolin increased the Bcl‑2/Bax ratio and enhanced Akt phosphorylation. However, these alterations were attenuated by pretreatment with an inhibitor of the PI3K/Akt pathway. In conclusion, luteolin inhibited H2O2‑induced apoptosis via reducing ROS levels and activating the PI3K/Akt pathway.

Melatonin improves functional outcome via inhibition of matrix metalloproteinases-9 after photothrombotic spinal cord injury in rats

BACKGROUND

Matrix metalloproteinases (MMPs), especially MMP-2 and MMP-9 play an important role in secondary inflammatory reaction and blood-central nervous system (CNS) barrier disruption after spinal cord injury (SCI). Theoretically, it is expected that early blockade of activation of MMPs can provide neuro-protective effects from secondary tissue damage and improve functional neurological outcomes. The aim of this study was to investigate the expression and the activity of MMP-2 and MMP-9, and to determine the regulatory effect of melatonin on MMP expression and activity after photochemically induced SCI in rats.

METHODS

Female Sprague-Dawley rats weighing between 250 and 300 g (age 8 weeks) received focal ischemia by photothrombosis using Rose Bengal (RB). The injured animals were divided into two groups; one group received 50 mg/kg of melatonin intraperitoneally, starting 1 h after injury and at 12 h intervals for 7 days, while animals in the control group received weight-adjusted doses of a saline vehicle. In each group, the expressions and activities of MMP-2 and MMP-9 were assessed by Western blot and gelatin zymography at various times from 6 h to 3 days. The locomotor function was assessed using the Basso-Beattie-Bresnahan (BBB) scale at 3 days after SCI and then once per week for 4 weeks. The animals were killed at 28 days after the injury, and the histopathology of the lesions was assessed.

FINDINGS

The expressions and activities of MMP-9 were increased at 6, 24, 48, and 72 h after SCI in the control group. In the melatonin-treated group, the expression of MMP-9 was significantly decreased at 24, 48, and 72 h after SCI compared with the control group, and the activity of MMP-9 was significantly reduced at 72 h after SCI. In contrast, there were no significant changes in the MMP-2 level in both groups during the experimental period. Melatonin treatment following photochemically induced SCI in rats significantly ameliorated the functional deficits. On histopathologic examination, the lesion size in the spinal cord after photothrombotic insult was significantly reduced by melatonin administration.

CONCLUSIONS

This study showed that the up-regulation of MMP-9 correlated with the secondary damage after SCI in rats. The results of this study suggest that the ability of melatonin to reduce secondary tissue damage is intimately related to the reduction of MMP-9 expression, resulting in functional improvement.

Neuroprotective effect of alpha-lipoic acid and methylprednisolone on the spinal cord ischemia/reperfusion injury in rabbits

OBJECTIVE

The aim of this study is to investigate the putative neuroprotective effect of alpha-lipoic acid (LA) on spinal ischemia/reperfusion (I/R) injury in rabbits.

METHODS

Thirty-five adult female New Zeland rabbits, weighing 2,000-3,500 g (mean: 2,800), were divided randomly into five groups of seven rabbits each (n: 7) as Group 1: sham, only laparotomy; Group 2 (İ/R): I/R; Group 3 (LA): I/R and 100 mg/kg of LA; Group 4 (MP): I/R and 30 mg/kg of methylprednisolone (MP); and Group 5 (LA + MP): I/R and 100 mg/kg of LA plus 30 mg/kg of MP.

RESULTS

A statically significant effect of LA, MP, and LA plus MP on lowering malondialdehyde levels both in the blood and in the cerebrospinal fluid (CSF) has been observed. Nitric oxide is significantly decreased in the blood and spinal cord tissues, and also in the CSF but it is not significant. Superoxide dismutase, catalase, and glutathione levels were increased by LA administration.

CONCLUSION

LA exhibits antioxidant efficacy in spinal cord I/R injury, but it cannot decrease the oxidative stress. The histopathological result of the present study also demonstrated that LA has neuroprotective effect in spinal cord injury.

Cinnamtannin B-1 regulates cell proliferation of spinal cord astrocytes and protects the cell from oxygen-glucose-serum deprivation/reoxygenation-induced apoptosis

Astrocytes are important for protecting neurons in the central nervous system. It has been reported that some antioxidants could protect astrocytes from ischemia/reperfusion-induced dysfunction. Cinnamtannin B-1 is a naturally occurring A-type proanthocyanidin that exhibits anti-oxidant properties. In this study, we investigated the effects of cinnamtannin B-1 on spinal cord astrocytes. Astrocytes were subjected to oxygen-glucose-serum deprivation for eight hours followed by reoxygenation with or without cinnamtannin B-1. We found that cinnamtannin B-1 protected astrocytes from oxygen-glucose-serum deprivation and reoxygenation-induced apoptosis. Concurrently, cinnamtannin B-1 promoted the proliferation of astrocytes whereas the extracellular regulated protein kinase (ERK) inhibitor reversed this effect. The results indicated that cinnamtannin B-1 protects astrocytes from oxygen-glucose-serum deprivation/reoxygenation-induced apoptosis by promoting astrocyte proliferation via an ERK pathway. Therefore, as an anti-oxidant, cinnamtannin B-1 might provide extra benefit for astrocyte protection during ischemia/reperfusion in the central nervous system.

Neuroprotective effects of allicin on spinal cord ischemia-reperfusion injury via improvement of mitochondrial function in rabbits

Allicin, the active substance of garlic, exerts a broad spectrum of pharmacological activities and is considered to have potential therapeutic applications. The present study was designed to investigate the beneficial effects of allicin against spinal cord ischemia-reperfusion (I/R) injury and its associated mechanisms. Male New Zealand white rabbits were pretreated with allicin (1, 10 and 50 mg/kg) for two weeks, and exposed to infrarenal aortic occlusion-induced spinal cord I/R injury. We found that allicin significantly reduced the volume of the spinal cord infarctions, improved the histopathologic features and increased the number of motor neurons in a dose-dependent manner. This protection was associated with an improvement in neurological function, which was measured by the hind-limb motor function scores. Furthermore, allicin also significantly suppressed the accumulations of protein and lipid peroxidation products, and increased the activities of endogenous antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione S-transferase (GST). In addition, allicin treatment preserved the function of mitochondria respiratory chain complexes and inhibited the production of ROS and the release of mitochondrial cytochrome c in the spinal cord of this model. Collectively, these findings demonstrated that allicin exerts neuroprotection against spinal cord I/R injury in rabbits, which may be associated with the improvement of mitochondrial function.

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

Oxidative stress induced by spinal cord injury (SCI) has deleterious effects on the function of several organ systems including the urinary bladder. In this study, we investigated the possible protective actions of melatonin on SCI-induced oxidative damage and urinary bladder dysfunction. Wistar albino rats (n = 24) were divided randomly as control, vehicle- or melatonin (10 mg/kg, ip)-treated SCI groups. To induce SCI, a standard weight-drop method that induced a moderately severe injury at T10 was used. Injured animals were given either vehicle or melatonin 15 min postinjury. One week postinjury, each rat was neurologically examined and then decapitated; blood samples were taken to evaluate neuron-specific enolase (NSE) and soluble protein 100β (S-100β). Spinal cord (SC) and urinary bladder samples were taken for functional studies and histological examination or stored for the measurement of malondialdehyde (MDA), glutathione (GSH) and nerve growth factor (NGF) levels and caspase-3 activity. Isometric contractions in bladder strips were induced by carbachol. In the SCI rats, decreased contractile responses of the bladder strips were found to be restored by melatonin treatment. Serum S-100β levels and NSE activities and tissue MDA levels and caspase-3 activities, all of which were elevated in the vehicle-treated SCI animals as compared to the control values, were reversed by melatonin treatment. On the other hand, reduced GSH and NGF levels due to SCI were restored by melatonin treatment. Furthermore, melatonin treatment improved histological findings. These findings suggest that melatonin reduces SCI-induced tissue injury and improves bladder functions through its effects on oxidative stress and NGF.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Beneficial effects of endogenous and exogenous melatonin on neural reconstruction and functional recovery in an animal model of spinal cord injury

The purpose of this study was to investigate the beneficial effects of endogenous and exogenous melatonin on functional recovery in an animal model of spinal cord injury (SCI). Eight-week-old male Sprague-Dawley (SD, 250-260 g) rats were used for contusion SCI surgery. All experimental groups were maintained under one of the following conditions: 12/12-hr light/dark (L/D) or 24:0-hr constant light (LL). Melatonin (10 mg/kg) was injected subcutaneously for 4 wk, twice daily (07:00, 19:00). Locomotor recovery, inducible nitric oxide synthase (iNOS), glial fibrillary acidic protein gene expression, and muscle atrophy-related genes, including muscle atrophy F-box (MAFbx) and muscle-specific ring-finger protein 1 (MuRF1) gene expression were evaluated. Furthermore, autophagic signaling such as Beclin-1 and LC3 protein expression was examined in the spinal cord and in skeletal muscle. The melatonin treatment resulted in increased hind-limb motor function and decreased iNOS mRNA expression in the L/D condition compared with the LL condition (P < 0.05), indicating that endogenous melatonin had neuroprotective effects. Furthermore, the MAFbx, MuRF1 mRNA level, and converted LC3 II protein expression were decreased in the melatonin-treated SCI groups under the LL (P < 0.05), possibly in response to the exogenous melatonin treatment. Therefore, it seems that both endogenous and exogenous melatonin contribute to neural recovery and to the prevention of skeletal muscle atrophy, promoting functional recovery after SCI. Finally, this study supports the benefit of endogenous melatonin and use of exogenous melatonin as a therapeutic intervention for SCI.

Neuroprotective effects of gabapentin on spinal cord ischemia-reperfusion injury in rabbits

Object

Extensive research has been focused on neuroprotection after spinal cord trauma to alleviate the effects of secondary injury. This study aims to investigate the neuroprotective effects of gabapentin in an experimental spinal cord ischemia reperfusion injury.

Methods

Thirty-two adult male New Zealand white rabbits received spinal cord ischemic injury using the aortic occlusion model. Animals were divided into 4 groups (sham, control, low-dose, and high-dose treatment groups; 8 rabbits in each group). High (200 mg/kg) and low (30 mg/kg) doses of gabapentin were administered to the animals in the treatment groups after spinal cord ischemic injury. Neurological status of the animals, ultrastructural findings in injured tissue samples, and levels of tissue injury markers in these 2 groups were compared with findings in the animals that did not receive the ischemic procedure (sham-operated group) and those that received normal saline after administration of ischemia.

Results

Regarding levels of tissue injury marker levels after ischemic injury, animals in the gabapentin-treated groups demonstrated better results than animals in the other groups. The ultrastructural findings and caspase-3 activity were similar. The treatment groups demonstrated better results than the other groups.

Conclusions

Gabapentin demonstrated significant neuroprotection after early phases of ischemic injury. Further studies with different experimental settings including neurological outcome are required to achieve conclusive results.

Immunohistochemical analysis of TIMP-2 and collagen types I and IV in experimental spinal cord ischemia-reperfusion injury in rats

BACKGROUND

Thoracic and thoracoabdominal aortic intervention carries a significant risk of spinal cord ischemia. The pathophysiologic mechanisms that cause hypoxic/ischemic injury to the spinal cord have not been totally explained. In normal spinal cord, neurons and glial cells do not express type IV collagen. Type IV collagen produced by reactive astrocytes is reported to participate in glial scar formation. Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors that regulate the activity of the matrix metalloproteinases (MMPs). TIMP-2 binds strongly with MMP-2, facilitating activation by membrane-type MMP. Imbalance between TIMPs and MMPs can lead to excessive degradation of matrix components. Type IV collagen involved in the blood-brain barrier disruption and glial scar formation, TIMP-2 influences MMP-2 that controls degradation of collagen I and IV.

OBJECTIVE

To examine the immunohistochemical analysis of TIMP-2 and collagen types I-IV in experimental spinal cord ischemia-reperfusion in rats.

METHODS

Thirty-two male Wistar rats weighing 250-300 g were divided into four groups: group S: sham group (n = 8); group 0P: 30-minute occlusion without perfusion (n = 8); group 3P: 30-minute occlusion and 3-hour perfusion (n = 8); and group 24P: 30-minute occlusion and 24-hour perfusion (n = 8). Infrarenal aorta was cross-clamped at two sites by using two aneurysm clips for 30 minutes. Reperfusion was provided after removal of the clips. Lumbar spinal cord segments were removed for immunohistochemical analysis.

RESULTS

TIMP-2 and collagen staining in 3-hour perfused (3P) group were nearly the same with sham group (S). TIMP-2 and collagen staining increased in the 24-hour perfused group.

CONCLUSION

Alterations in collagen levels may relate to the biphasic breakdown of the blood-brain barrier and collagen staining in new cell types with relation to glial scar formation. Our results demonstrate that 3-hour perfusion after occlusion in hypoxic/ischemic spinal cord injury seems to be the critical reversible period.

Melatonin plus exercise-based neurorehabilitative therapy for spinal cord injury

Spinal cord injury (SCI) is damage to the spinal cord caused by the trauma or disease that results in compromised or loss of body function. Subsequent to SCI in humans, many individuals have residual motor and sensory deficits that impair functional performance and quality of life. The available treatments for SCI are rehabilitation therapy, activity-based therapies, and pharmacological treatment using antioxidants and their agonists. Among pharmacological treatments, the most efficient and commonly used antioxidant for experimental SCI treatment is melatonin, an indolamine secreted by pineal gland at night. Melatonin's receptor-independent free radical scavenging action and its broad-spectrum antioxidant activity makes it an ideal antioxidant to protect tissue from oxidative stress-induced secondary damage after SCI. Owing to the limitations of an activity-based therapy and antioxidant treatment singly on the functional recovery and oxidative stress-induced secondary damages after SCI, a melatonin plus exercise treatment may be a more effective therapy for SCI. As suggested herein, supplementation with melatonin in conjunction with exercise not only would improve the functional recovery by enhancing the beneficial effects of exercise but would reduce the secondary tissue damage simultaneously. Finally, melatonin may protect against exercise-induced fatigue and impairments. In this review, based on the documented evidence regarding the beneficial effects of melatonin, activity-based therapy and the combination of both on functional recovery, as well as reduction of secondary damage caused by oxidative stress after SCI, we suggest the melatonin combined with exercise would be a novel neurorehabilitative strategy for the faster recovery after SCI.

Anti-apoptotic and neuroprotective effects of α-lipoic acid on spinal cord ischemia-reperfusion injury in rabbits

PURPOSE

Radical oxygen species produced after injury counteracts antioxidant activity and frequently causes severe oxidative stress for the tissues. Alpha-lipoic acid is a powerful metabolic antioxidant with immunomodulatory effects which provides neuroprotection. The aim of this study is to investigate the neuroprotective and anti-apoptotic effects of alpha-lipoic acid on spinal cord ischemia-reperfusion.

METHODS

Twenty-four adult, male, New Zealand rabbits were divided into sham (n = 8), control (n = 8), and treatment groups (n = 8). The abdominal aorta was clamped for 30 min by an aneurysm clip, approximately 1 cm below the renal artery and 1 cm above the iliac bifurcation in control and treatment groups. Only laparotomy was performed in the sham group. Twenty-five cubic centimeters of saline in control group and 100 mg/kg lipoic acid were administered intraperitoneally in the treatment group after closure of the incision. The animals were killed 48 h later. Spinal cord segments between L2 and S1 were harvested for analysis. Levels of nitric oxide, glutathione, malondialdehyde, advanced oxidation protein products, and superoxide dismutase were analyzed as markers of oxidative stress and inflammation. Caspase-3 activity was analyzed to detect the effect of lipoic acid on apoptosis.

RESULTS

In all measured parameters of oxidative stress, administration of lipoic acid significantly demonstrated favorable effects. Both plasma and tissue levels of nitric oxide, glutathione, malondialdehyde, and advanced oxidation protein products significantly changed in favor of antioxidant activity. There was no significant difference between the plasma superoxide dismutase levels of the groups. Histopathological evaluation of the tissues also demonstrated significant decrease in cellular degeneration and infiltration parameters after lipoic acid administration. However, lipoic acid has no effect on caspase-3 activity.

CONCLUSIONS

Although further studies considering different dose regimens and time intervals are required, the results of the present study prove that alpha-lipoic acid has favorable effects on experimental spinal cord ischemia-reperfusion injury.

Effects of iloprost and piracetam in spinal cord ischemia-reperfusion injury in the rabbit

STUDY DESIGN

Experimental Study.

OBJECTIVES

The aim of this study was to investigate the neuroprotective effects of iloprost and piracetam on spinal cord ischemia/reperfusion (I/R) injury in the rabbit.

SETTINGS

The Experimental Research Center of Selcuk University, Konya, Turkey.

METHODS

A total of 24 rabbits were divided into four groups of six rabbits each, as follows: group 1 (n = 6) sham, laparotomy only; group 2 (n = 6) I/R; group 3 (n = 6) I/R+iloprost; and group 4 (n = 6) I/R+piracetam. I/R was established in groups 2, 3 and 4. Subsequently, they were followed up neurologically for 24 h until the rabbits were killed; biochemical and histopathological examinations of samples from the spinal cord were carried out.

RESULTS

Neurological examination results were significantly better in the iloprost and piracetam groups compared with the I/R group (P < 0.05). Neuroprotection was achieved with iloprost and piracetam by suppressing malondialdehyde (P < 0.05), increasing glutathione peroxidase activity (P < 0.05) and decreasing the xanthine oxidase level. In histopathological assessment, iloprost and piracetam groups were statistically different from the I/R group in terms of the number of apoptotic neurons in gray matter and white matter, as well as in terms of degenerated neurons and glial cells (P < 0.05). No statistical difference was determined between the four groups in the number of degenerated glial cells (P > 0.05).

CONCLUSION

This study has shown that iloprost and piracetam have neuroprotective effects in I/R injury both neurologically and histopathologically because of inhibition of lipid peroxidation.

The role of excitatory amino acid transporters in cerebral ischemia

Glutamate is an excitatory neurotransmitter that plays a major role in the pathogenesis of ischemia brain injury. The regulation of glutamate neurotransmission is carried out by excitatory amino acid transporters (EAATs) that act through reuptake of glutamate into cells. EAATs may also release glutamate into the extracellular space in a calcium-independent manner during ischemia and dysfunction of EAATs is specifically implicated in the pathology of cerebral ischemia. Recent studies show that up-regulation of EAAT2 provides neuroprotection during ischemic insult. This review summarizes current knowledge regarding the role of EAATs in cerebral ischemia.

Melatonin attenuates I/R-induced mitochondrial dysfunction in skeletal muscle

BACKGROUND

Our recent studies have shown that ischemia/reperfusion (I/R) produces significant necrosis and apoptosis in the cells of skeletal muscle. Our previous studies also demonstrated that melatonin provides significant protection against superoxide generation, endothelial dysfunction, and cell death in the skeletal muscle after I/R. Mitochondria are essential for cell survival, because of their roles as ATP producers as well as regulators of cell death. However, the efficacy of melatonin on I/R-induced mitochondrial dysfunction in the skeletal muscle in vivo has not been demonstrated in the literature.

MATERIALS AND METHODS

Vascular pedicle isolated rat gracilis muscle model was used. After 4 h of ischemia followed by 24 h of reperfusion, gracilis muscle was harvested, and mitochondrial as well as cytosolic fractions were isolated. Mitochondrial dysfunction was determined by the alteration of mitochondrial membrane potential and the release of the proapoptotic protein, cytochrome c. Three groups were designed; sham I/R, I/R-V (I/R with vehicle), and I/R-Mel (I/R with melatonin). Melatonin or vehicle was given intravenously 10 min prior to reperfusion and 10 min after reperfusion.

RESULTS

We found that the capability of uptake of fluorescent JC-1 dye in skeletal muscle cells was substantially improved in I/R-Mel group compared with I/R-V group. Melatonin significantly inhibited the outflow of cytochrome c from mitochondria to cytoplasm, which was demonstrated in the I/R-V group.

CONCLUSIONS

Melatonin significantly attenuates I/R-induced mitochondrial dysfunction, such as the depolarization of mitochondrial membrane potential and the release of the proapoptotic protein, cytochrome c, from the mitochondria.

Therapeutic potential of melatonin in traumatic central nervous system injury

A vast literature extolling the benefits of melatonin has accumulated during the past four decades. Melatonin was previously considered of importance to seasonal reproduction and circadian rhythmicity. Currently, it appears to be a versatile anti-oxidative and anti-nitrosative agent, a molecule with immunomodulatory actions and profound oncostatic activity, and also to play a role as a potent neuroprotectant. Nowadays, melatonin is sold as a dietary supplement with differential availability as an over-the-counter aid in different countries. There is a widespread agreement that melatonin is nontoxic and safe considering its frequent, long-term usage by humans at both physiological and pharmacological doses with no reported side effects. Endeavors toward a designated drug status for melatonin may be enormously rewarding in clinics for treatment of several forms of neurotrauma where effective pharmacological intervention has not yet been attained. This mini review consolidates the data regarding the efficacy of melatonin as an unique neuroprotective agent in traumatic central nervous system (CNS) injuries. Well-documented actions of melatonin in combating traumatic CNS damage are compiled from various clinical and experimental studies. Research on traumatic brain injury and ischemia/reperfusion are briefly outlined here as they have been recently reviewed elsewhere, whereas the studies on different animal models of the experimental spinal cord injury have been extensively covered in this mini review for the first time.

Melatonin attenuates calpain upregulation, axonal damage and neuronal death in spinal cord injury in rats

Multiple investigations in vivo have shown that melatonin (MEL) has a neuroprotective effect in the treatment of spinal cord injury (SCI). This study investigates the role of MEL as an intervening agent for ameliorating Ca(2+)-mediated events, including activation of calpain, following its administration to rats sustaining experimental SCI. Calpain, a Ca(2+)-dependent neutral protease, is known to be involved in the pathogenesis of SCI. Rats were injured using a standard weight-drop method that induced a moderately severe injury (40 g.cm force) at T10. Sham controls received laminectomy only. Injured animals were given either 45 mg/kg MEL or vehicle at 15 min post-injury by intraperitoneal injection. At 48 hr post-injury, spinal cord (SC) samples were collected. Immunofluorescent labelings were used to identify calpain expression in specific cell types, such as neurons, glia, or macrophages. Combination of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and double immunofluorescent labelings was used to identify apoptosis in specific cells in the SC. The effect of MEL on axonal damage was also investigated using antibody specific for dephosphorylated neurofilament protein (dNFP). Treatment of SCI animals with MEL attenuated calpain expression, inflammation, axonal damage (dNFP), and neuronal death, indicating that MEL provided neuroprotective effect in SCI. Further, expression and activity of calpain and caspse-3 were examined by Western blotting. The results indicated a significant decrease in expression and activity of calpain and caspse-3 in SCI animals after treatment with MEL. Taken together, this study strongly suggested that MEL could be an effective neuroprotective agent for treatment of SCI.

Preventive effects of intrathecal methylprednisolone administration on spinal cord ischemia in rats: The role of excitatory amino acid metabolizing systems

Spinal cord ischemic injury usually results in paraplegia, which is a major cause of morbidity after thoracic aorta operations. Ample evidence indicates that massive release of excitatory amino acids (EAAs; glutamate) plays an important role in the development of neuronal ischemic injuries. However, there is a lack of direct evidence to indicate the involvement of EAAs in the glutamate metabolizing system (including the glutamate transporter isoforms, i.e. the Glu-Asp transporter (GLAST), Glu transporter-1 (GLT-1), and excitatory amino acid carrier one (EAAC1); glutamine synthetase (GS); and glutamate dehydrogenase (GDH)) in spinal cord ischemia. In the present results, we found that methylprednisolone (MP; intrathecal (i.t.) injection, 200 mug twice daily administered for 3 days before ischemia), a synthetic glucocorticoid, is the therapeutic agent for the treatment of spinal injuries in humans, can significantly reduce the ischemia-induced motor function defect and down-regulate the glutamate metabolizing system (including GLAST, GLT-1, GS, and GDH) in male Wistar rats. The spinal cord ischemia-induced down-regulation of EAAC1 protein expression in the ventral portion of the lumbar spinal cord was partly inhibited by pretreatment with i.t. MP. However, MP did not affect the down-regulation of EAAC1 in the dorsal portion of the lumbar spinal cord after spinal cord ischemia. The i.t. injection of MP alone did not change the neurological functions and the expression of proteins of the glutamate metabolizing system in the spinal cord. Our results indicate that spinal cord ischemia-induced neurological deficits accompany the decrease in the expression of proteins of the glutamate metabolizing system in the lumbar portion of the spinal cord. The i.t. MP pretreatment significantly prevented these symptoms. These results support the observation that MP delivery through an i.t. injection, is beneficial for the treatment of spinal cord ischemic injuries.

The effects of prophylactic zinc and melatonin application on experimental spinal cord ischemia–reperfusion injury in rabbits: experimental study

STUDY DESIGN

Experimental study.

OBJECTIVES

To determine the neuroprotective effects of zinc and melatonin on spinal cord ischemia-reperfusion (I/R) injuries of rabbits.

SETTING

The Experimental Research Centre of Selçuk University, Konya, Turkey.

METHODS

Twenty-four male rabbits underwent spinal cord ischemia by clamping the thoraco-abdominal aorta for 20 min. Twenty minutes before the aortic clamping, animals received zinc, melatonin or a combination of both. Neurological examination of the animals was performed three times during reperfusion period. The animals were killed 24 h after reperfusion. Spinal cord samples were taken for biochemical and histopathological evaluation.

RESULTS

Pre-treated animals with zinc, melatonin or combination displayed better neurological outcomes than the I/R group (P<0.05). Zinc, melatonin and combined treatment prevented spinal cord injury by reducing apoptosis rate (P<0.05) and preserving intact ganglion cell numbers (P<0.05). Zinc pre-treatment protected spinal cord by preventing malondialdehyde (MDA) formation (P=0.002), increasing glutathione peroxidase (GPx) activity (P=0.002) and decreasing xanthine oxidase enzyme activity (P=0.026) at molecular level. Melatonin treatment also resulted with MDA formation (P=0.002), increased GPx activity (P=0.002) and decreased xanthine oxidase activity (P=0.026).

CONCLUSION

The results of the study showed that prophylactic zinc and melatonin use in spinal cord I/R not only suppressed lipid peroxidation by activating antioxidant systems but also had significant neuroprotective effects by specifically improving the neurological and histopathological situation.

Melatonin reduces ischemia/reperfusion-induced superoxide generation in arterial wall and cell death in skeletal muscle

The purpose of this study was to determine the effect of melatonin on superoxide generation in arterial wall at an early phase of reperfusion and on endothelial dysfunction of microvasculature and cell viability of cremaster muscle at late phase of reperfusion (24 hr) after prolonged ischemia. Bilateral vascular pedicles which supply blood flow to the cremaster muscle were exposed. After surgical preparation, microvascular clamps were applied on the right iliac, femoral and spermatic arteries to create 4 hr of ischemia in both feeding vessels and the unexposed cremaster muscle. The vascular clamping was omitted on the left iliac, femoral and spermatic arteries and served as an internal control. Melatonin or Vehicle was via by intravenous injection at 10 min prior to reperfusion and 10 min after reperfusion. In the first experiment, the vascular pedicle was harvested after reperfusion to measure superoxide generation in real time by lucigenin-derived chemiluminescence. In the second experiment, endothelial-dependent and -independent vasodilatation was examined in the terminal arteriole of cremaster muscle which was then harvested to examine cell viability by WST-1 assay on day 2. Superoxide generation in arterial wall peaked at first 5-min of reperfusion and declined to near baseline after 60 min of reperfusion. Melatonin treatment significantly reduced superoxide generation in arterial walls and improved cell viability in cremaster muscles. Melatonin treatment also significantly reduced microvascular endothelial dysfunction which was still observable in the microcirculation of cremaster muscle after 24 hr of reperfusion. Melatonin reduces superoxide generation in the early phase of reperfusion resulting in attenuating endothelial dysfunction and muscle cell death in the late phase of reperfusion.

Anti-apoptotic and neuroprotective effects of Tetramethylpyrazine following spinal cord ischemia in rabbits

Background

Tetramethylpyrazine (TMP) is one of the most important active ingredients of a Chinese herb Ligusticum wallichii Franchat, which is widely used in many ischemia disorders treatments. However, the exact mechanism by which TMP protects the spinal cord ischemia/reperfusion (I/R) injury is still unknown. For this purpose, rabbits were randomly divided into sham group, control group and TMP group. After the evaluation of neurologic function, the spinal cords were immediately removed for biochemical and histopathological analysis. Apoptosis was measured quantitatively by the terminal transferase UTP nick end-labeling (TUNEL) method and confirmed by electron microscopic examination, the expression of Bax and Bcl-2 was immunohistochemically evaluated and quantified by Western blot analysis.

Results

Neurologic outcomes in the TMP-group were significantly better than those in the control group (P < 0.05). TMP decreased spinal cord malondialdehyde (MDA) levels and ameliorated the down regulation of spinal cord superoxide dismutase (SOD) activity. TMP significantly reduced the loss of motoneurons and TUNEL-positive rate. Greater Bcl-2 and attenuated Bax expression was found in the TMP treating rabbits.

Conclusion

These findings suggest that TMP has protective effects against spinal cord I/R injury by reducing apoptosis through regulating Bcl-2 and Bax expression.

Effects of melatonin or acetylsalicylic acid on gastric oxidative stress after bile duct ligation in rats

BACKGROUND

Antioxidant enzyme activities decrease after bile duct ligation. The aim of this study was to assess the effect of melatonin and acetylsalicylic acid on antioxidant enzyme activities in gastric oxidative stress induced by bile duct ligation.

METHODS

Sixty-four animals were divided into eight groups of eight rats each. Male Sprague-Dawley rats were subjected to either a sham operation or common bile duct ligation (BDL) before treatment with melatonin (MEL) or acetylsalicylic acid (ASA). Gastric superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, and malondialdehyde (MDA) and nitric oxide (NO) levels were determined by spectrophotometers and evaluated.

RESULTS

Our results indicated that BDL caused a significant increase in lipid peroxidation, whereas coadministration of MEL with ASA significantly decreased MDA and NO levels in BDL rats. Moreover, coadministration of MEL and ASA increased antioxidant enzyme activities after the BDL, and these increases were statistically significant for CAT and GPx. On the other hand, the increase in SOD activity was not significant.

CONCLUSIONS

Melatonin administration, either alone or together with acetylsalicylic acid, decreases lipid peroxidation and increases antioxidant enzyme activities in gastric tissues of rats after bile duct ligation. ASA administration, however, either alone or with a vehicle, increases lipid peroxidation and decreases antioxidant enzyme activities.

Antioxidative protection by melatonin: multiplicity of mechanisms from radical detoxification to radical avoidance

Melatonin has been shown to protect against oxidative stress in various, highly divergent experimental systems. There are many reasons for its remarkable protective potential. Signaling effects comprise the upregulation of antioxidant enzymes, such as superoxide dismutases, peroxidases, and enzymes of glutathione supply, down-regulation of prooxidant enzymes, such as nitric oxide synthases and lipoxygenases, and presumably also the control of quinone reductase 2. Other mechanisms are based on direct interactions with several reactive oxygen and nitrogen species. Among these reactions, the capacity of easily undergoing single-electron transfer reactions is of particular importance. Electron donation by melatonin is not only an aspect of direct radical scavenging, but additionally represents the basis for formation of the protective metabolites AFMK (N1-ace-tyl-N2-formyl-5-methoxykynuramine) and AMK (N1-acetyl-5-methoxykynuramine). Recent investigations on mitochondrial metabolism indicate that melatonin as well as AMK are capable of supporting the electron flux through the respiratory chain, of preventing the breakdown of the mitochondrial membrane potential, and of decreasing electron leakage, thereby reducing the formation of superoxide anions. Radical avoidance is a new line of investigation, which exceeds mitochondrial actions and also comprises antiexcitatory effects and contributions to the maintenance of internal circadian phase relationships.

Melatonin, a potent agent in antioxidative defense: actions as a natural food constituent, gastrointestinal factor, drug and prodrug

Melatonin, originally discovered as a hormone of the pineal gland, is also produced in other organs and represents, additionally, a normal food constituent found in yeast and plant material, which can influence the level in the circulation. Compared to the pineal, the gastrointestinal tract contains several hundred times more melatonin, which can be released into the blood in response to food intake and stimuli by nutrients, especially tryptophan. Apart from its use as a commercial food additive, supraphysiological doses have been applied in medical trials and pure preparations are well tolerated by patients. Owing to its amphiphilicity, melatonin can enter any body fluid, cell or cell compartment. Its properties as an antioxidant agent are based on several, highly diverse effects. Apart from direct radical scavenging, it plays a role in upregulation of antioxidant and downregulation of prooxidant enzymes, and damage by free radicals can be reduced by its antiexcitatory actions, and presumably by contributions to appropriate internal circadian phasing, and by its improvement of mitochondrial metabolism, in terms of avoiding electron leakage and enhancing complex I and complex IV activities. Melatonin was shown to potentiate effects of other antioxidants, such as ascorbate and Trolox. Under physiological conditions, direct radical scavenging may only contribute to a minor extent to overall radical detoxification, although melatonin can eliminate several of them in scavenger cascades and potentiates the efficacy of antioxidant vitamins. Melatonin oxidation seems rather important for the production of other biologically active metabolites such as N¹-acetyl-N²-formyl-5-methoxykynuramine (AFMK) and N¹-acetyl-5-methoxykynuramine (AMK), which have been shown to also dispose of protective properties. Thus, melatonin may be regarded as a prodrug, too. AMK interacts with reactive oxygen and nitrogen species, conveys protection to mitochondria, inhibits and downregulates cyclooxygenase 2.

Microcirculatory effects of melatonin in rat skeletal muscle after prolonged ischemia

The purpose of this study was to determine microcirculatory effects and response of nitric oxide synthase (NOS) to melatonin in skeletal muscle after prolonged ischemia. A vascular pedicle isolated rat cremaster muscle model was used. Each muscle underwent 4 hr of zero-flow warm ischemia followed by 2 hr of reperfusion. Melatonin (10 mg/kg) or saline as a vehicle was given by intraperitoneal injection at 30 min prior to reperfusion and the same dose was given immediately after reperfusion. After reperfusion, microcirculation measurements including arteriole diameter, capillary perfusion and endothelial-dependent and -independent vasodilatation were performed. The cremaster muscle was then harvested to measure endothelial NOS (eNOS) and inducible NOS (iNOS) gene expression and enzyme activity. Three groups of rats were used: sham-ischemia/reperfusion (I/R), vehicle + I/R and melatonin + I/R. As compared with vehicle + I/R group, administration of melatonin significantly enhanced arteriole diameter, improved capillary perfusion, and attenuated endothelial dysfunction in the microcirculation of skeletal muscle after 4 hr warm ischemia. Prolonged warm ischemia followed by reperfusion significantly depressed eNOS gene expression and constitutive NOS activity and enhanced iNOS gene expression. Administration of melatonin did not significantly alter NOS gene expression or activity in skeletal muscle after prolonged ischemia and reperfusion. Melatonin provided a significant microvascular protection from reperfusion injury in skeletal muscle. This protection is probably attributable to the free radical scavenging effect of melatonin, but not to its anti-inflammatory effect.

Attenuation in the evolution of experimental spinal cord trauma by treatment with melatonin

Melatonin is the principal secretory product of the pineal gland and its role as an immuno-modulator is well established. Recent evidence shows that melatonin is a scavenger of oxyradicals and peroxynitrite and exerts protective effects in septic shock, hemorrhagic shock and inflammation. In the present study, we evaluated the effect of melatonin treatment, in a model of spinal cord injury (SCI). SCI was induced by the application of vascular clips (force of 50 g) to the dura via a four-level T5-T8 laminectomy. SCI in rats resulted in severe trauma characterized by edema, neutrophil infiltration and apoptosis (measured by terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling staining). Infiltration of spinal cord tissue with neutrophils (measured as increase in myeloperoxidase activity) was associated with enhanced lipid peroxidation (increased tissue levels of malondialdehyde). Immunohistochemical examination demonstrated a marked increase in immunoreactivity for nitrotyrosine and Poly(ADP-ribose) (PAR) in the spinal cord tissue. In contrast, the degree of (a) spinal cord inflammation and tissue injury (histological score), (b) nitrotyrosine and PAR formation, (c) neutrophils infiltration and (d) apoptosis was markedly reduced in spinal cord tissue obtained from rats treated with melatonin (50 mg/kg i.p., 30 min before SCI, 30 min, 6 hr, 12 hr and 24 hr after SCI). In a separate set of experiment we have clearly demonstrated that melatonin treatment significantly ameliorated the recovery of limb function (evaluated by motor recovery score). Taken together, our results demonstrate that treatment with melatonin reduces the development of inflammation and tissue injury events associated with spinal cord trauma.