Mel Group Research Articles

Mechanism of liver injury in severe acute pancreatitis rats and role of melatonin

To investigate the activation level of nuclear factor-kappaB (NF-kappaB) in liver injury caused by severe acute pancreatitis (SAP) and the protective role of melatonin against liver injury. Ninety-six Sprague-Dawley (SD) rats were randomly divided into 3 equal groups: SAP group undergoing injection of sodium taurocholate to establish SAP models, melatonin (Mel) treatment group undergoing intraperitoneal injection 50 mg/kg 30 minutes before the establishment of SAP models, and sham operation group (Sham group). 4, 12, 24, and 48 hours after the onset of operation, blood samples were collected from the inferior vena casa of 8 rats from each group to measure the serum level of amylase (AMY) and alanine transaminase (ALT) by iodine colorimetry, and to detect the serum level of tumor necrosis factor-alpha (TNF-alpha) by ELISA. The livers were taken out to undergo pathological examination. Immunohistochemistry was used to examine the percentage of nuclear factor (NF)-kappaB in the hepatocytes. Terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) was used to determine the extent of hepatic apoptosis. The AMY and ALT levels at different time points of the SAP and Mel subgroups were all significantly higher than those of the sham operation subgroups (all P<0.05), and the AMY and ALT levels at different time points of the Mel subgroup were all significantly lower than those of the SAP subgroups (all P<0.05). The liver NF-kappaB activation level and hepatocellular apoptosis index of the SAP group increased since the fourth hour after the operation, and peaked at the time point of 24 hour, all significantly higher than those of the sham operation group (all P<0.05), and then declined. The TNF-alpha level at the time points of 12, 24, and 48 h in the SAP group were all significantly higher than those of the other 2 groups (all P<0.05). The levels of TNF-alpha, AMY, and ALT, the activity of NF-kappaB, and the extent of hepatocellular apoptosis at any time points of the Mel group were all significantly lower than those of the SAP group, but significantly higher than those of the sham operation group. Microscopy showed that the liver pathological damages of the Mel group were milder than those of the SAP group. SAP with liver injury is associated with the hepatic NF-kappaB activation leading to the production of NF-kappaB dependent cytokines and chemokines such as TNF-alpha. Melatonin reduces the apoptosis and necrosis in liver by inhibiting the activity of NF-kappaB and decreasing the expression of TNF-alpha.

Does melatonin help save dopaminergic cells in MPTP-treated mice?

This study explores whether melatonin neuroprotects dopaminergic cells of the substantia nigra pars compacta (SNc) from degeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice (well-known animal model of Parkinson disease). BALB/c albino mice were divided into four experimental groups. In each, mice received three series (over a 24-h period) of two intraperitoneal injections (1 h apart) in different combinations. The different groups and their combinations of injections were: (1) Saline (saline, saline); (2) Mel (melatonin, saline); (3) MPTP (saline, MPTP); (4) Mel-MPTP (melatonin, MPTP). Six days after the last injection, all mice were perfused transcardially with aldehyde fixative. Brains were processed for routine tyrosine hydroxylase (TH; rate limiting enzyme for dopamine production) immunochemistry and Nissl staining. Our results – using unbiased stereology – showed that there were more TH + (50%) and Nissl-stained (30%) cells in the SNc of the Mel-MPTP group compared to the MPTP group, indicating a clear saving or neuroprotection of these cells. In fact, we found no significant difference between the number of TH + and Nissl-stained SNc cells in the Mel-MPTP group compared to the controls, namely Saline and Mel groups. This indicated that melatonin pre-treatment potentially neuroprotected all the SNc cells from MPTP toxicity and death.

Supplementation of melatonin in vitro maturation (IVM) medium improves the efficiency of human IVM-IVF-ET program for the fertility treatment

OBJECTIVE: In vitro maturation program (IVM) has become increasingly important part in human assisted reproductive technology (ART). The establishment of an IVM program can yield many advantages. Because IVM conditions can affect oocytes' successful maturation and subsequent embryonic development, many researches have attempted to improve the culture medium. Melatonin is known to be associated with regulation of the dynamic physiological functions in general, and also is present in human preovulatory follicular fluid and may relate to reproduction. The aim of this study was to evaluate the effect of melatonin in maturation medium for IVM-IVF-ET program of polycystic ovarian (PCO) syndrome and non-PCO patients.DESIGN: Prospective and randomized study.MATERIALS AND METHODS: This clinical study was taken under the approval of the Institutional Review Board of University Hospital. Total of 205 IVM-IVF cycles undertaken in the Fertility Center from August 2004 to December 2007 were randomly divided into melatonin-added (MEL, n= 109) and control groups (non-melatonin added, n=96). The immature oocytes were aspirated and cultured in these two different types of media. Basic IVM medium (G2 medium supplemented with 20% human follicular fluid, 75mIU/ml rFSH, 0.5IU/ml hCG, and 1μg/ml E2) was used for control group. 10 μM melatonin was added to basic IVM medium and used for MEL group. Clinical outcome were analyzed based on the patients characteristics (PCO or non-PCO).RESULTS: In PCO patients, total of 143 IVM-IVF-ET (66 cycles in MEL and 77 cycles in control), the maturation rate at 24h and implantation rates in MEL were higher than those of control group (47.7%(426/893) vs. 42.1%(463/1100), 19.2%(44/229) vs. 12.5%(35/281), p<0.05). Pregnancy rate in MEL was also higher than that of control, but not significant (48.5%(32/66) vs. 36.4% (28/77), p=0.14). In non-PCO patients, total of 62 IVM-IVF-ET (43 cycles in MEL and 19 cycles in control), the number of retrieved oocytes in MEL and control groups were 6.9±3.7 and 9.2±4.5, respectively. The pregnancy rates in MEL were higher than those of control (27.9%(12/43) vs. 5.3%(1/19), p<0.05). However, there was no difference in maturation and implantation rate between two groups.CONCLUSIONS: The addition of melatonin in in vitro maturation system for human immature has improved the clinical efficiency of IVM-IVF-ET program for PCO or non-PCO patients. OBJECTIVE: In vitro maturation program (IVM) has become increasingly important part in human assisted reproductive technology (ART). The establishment of an IVM program can yield many advantages. Because IVM conditions can affect oocytes' successful maturation and subsequent embryonic development, many researches have attempted to improve the culture medium. Melatonin is known to be associated with regulation of the dynamic physiological functions in general, and also is present in human preovulatory follicular fluid and may relate to reproduction. The aim of this study was to evaluate the effect of melatonin in maturation medium for IVM-IVF-ET program of polycystic ovarian (PCO) syndrome and non-PCO patients. DESIGN: Prospective and randomized study. MATERIALS AND METHODS: This clinical study was taken under the approval of the Institutional Review Board of University Hospital. Total of 205 IVM-IVF cycles undertaken in the Fertility Center from August 2004 to December 2007 were randomly divided into melatonin-added (MEL, n= 109) and control groups (non-melatonin added, n=96). The immature oocytes were aspirated and cultured in these two different types of media. Basic IVM medium (G2 medium supplemented with 20% human follicular fluid, 75mIU/ml rFSH, 0.5IU/ml hCG, and 1μg/ml E2) was used for control group. 10 μM melatonin was added to basic IVM medium and used for MEL group. Clinical outcome were analyzed based on the patients characteristics (PCO or non-PCO). RESULTS: In PCO patients, total of 143 IVM-IVF-ET (66 cycles in MEL and 77 cycles in control), the maturation rate at 24h and implantation rates in MEL were higher than those of control group (47.7%(426/893) vs. 42.1%(463/1100), 19.2%(44/229) vs. 12.5%(35/281), p<0.05). Pregnancy rate in MEL was also higher than that of control, but not significant (48.5%(32/66) vs. 36.4% (28/77), p=0.14). In non-PCO patients, total of 62 IVM-IVF-ET (43 cycles in MEL and 19 cycles in control), the number of retrieved oocytes in MEL and control groups were 6.9±3.7 and 9.2±4.5, respectively. The pregnancy rates in MEL were higher than those of control (27.9%(12/43) vs. 5.3%(1/19), p<0.05). However, there was no difference in maturation and implantation rate between two groups. CONCLUSIONS: The addition of melatonin in in vitro maturation system for human immature has improved the clinical efficiency of IVM-IVF-ET program for PCO or non-PCO patients.

Establishing the Use of Melatonin as an Adjuvant Therapeutic Against Paraquat-Induced Lung Toxicity in Rats

It is well known that the intake of paraquat (PQ) causes severe tissue injury leading to numerous fatalities. Considering that the main target for PQ toxicity is the lung and involves the production of reactive oxygen and nitrogen species, transcription factors and inflammatory cytokines, it may be hypothesized that the combination of a potent antiinflammatory and antioxidant agent may counteract more of PQ's effects than an antiinflammatory agent alone. For this purpose, combination of dexamethasone (Dex) and melatonin (Mel) was compared with Dex alone. A total of 40 male Wistar albino rats were divided into four groups as control, PQ, Dex only, and Dex plus Mel. The animals were given intraperitoneally a toxic dose of 19 mg/kg PQ dissolved in 1 ml saline. Control animals were injected with the same amount of saline only. A dose of 1 mg/kg Dex was administered 2 hrs after PQ administration. In the combination treatment group, 20 mg/kg Mel was given with Dex. All drugs were given every 12 hrs for a total of six doses. Five animals in PQ group and three animals in Dex only group died by the end of the study. No deaths occurred in the Dex+Mel group. Dex exerted improvements in several oxidative and antioxidative parameters. However, combination treatment provided beneficial effects against PQ toxicity far greater than Dex alone. This difference was also apparent when tissues were histologically compared. In conclusion, Mel exhibited strong additive beneficial effects with Dex and can be considered as a safe treatment modality against PQ toxicity.

Chemopreventive effect of lycopene alone or with melatonin against the genesis of oxidative stress and mammary tumors induced by 7,12 dimethyl(a)benzanthracene in sprague dawely female rats

Breast cancer is the principle cause of death among women worldwide. In this study, we investigated the anti-tumor potential of lycopene (Lyco) alone or combined with melatonin (Lyco + Mel) for 120 days against a single oral dose of (50 mg/kg B.W.) 7,12-dimethylbenz(a)anthracene (DMBA)-induced oxidative stress and mammary carcinogenesis in female rats. The treatment protocol started from the day immediately after DMBA administration. Results obtained indicated that there was an elevation in the levels of malondialdhyde and nitric oxide in serum and breast tissues of DMBA injected rats. The combined treatment (Lyco + Mel) group showed a potential reduction of these parameters more than lyco individually. The activities of SOD, CAT, and GPx were found to be significantly high than lyco alone treated rats. In DMBA group a negative significant correlation between weight and serum nitric oxide (r = -0.59), and a positive significant correlation between NO and MDA (r = 0.81) was observed. Histopathological examination revealed the formation of tumor and angiogenesis in DMBA-induced rats and these abnormal changes were ameliorated by combined treatment with Lyco + Mel. In conclusion, these results suggested that supplementation of diet with lycopene with melatonin provided antioxidant defense with strong chemo preventive activity against DMBA-induced mammary tumors.

Melatonin as an Adjuvant Therapy Against Lung Paraquat Toxicity in Rats

The intake of paraquat (PQ) causes severe tissue injury leading to numerous fatalities. Considering that PQ toxicity involves the production of reactive oxygen and nitrogen species, transcription factors and inflammatory cytokines, it may be hypothesized that combination a potent antiinflammatory and antioxidant agent may counteract more of PQ's effects than an antiinflammatory agent alone. For this purpose, combination of dexamethasone (Dex) and melatonin (Mel) was compared with Dex alone. Forty male Wistar rats were divided into control, PQ, Dex only and Dex plus Mel groups. Animals were given a toxic dose of i.p. 19 mg/kg PQ dissolved in saline. Control animals were injected the same amount of saline. 1 mg/kg Dex was administered two h after PQ administration. In the combination treatment group 20 mg/kg Mel was given with Dex. Drugs were given every 12 h for a total of 6 doses. Five animals in PQ group and three animals in Dex only group died by the end of the study. No death occurred in the Dex+Mel group. Dex exerted improvements several oxidative and antioxidative parameters. However, combination treatment provides beneficial effects against PQ toxicity far greater than Dex alone. This difference was apparent when tissues were histologically compared. These results suggest that the reduced dose of corticosteroids with Mel is a safe treatment against PQ toxicity.

Neuropsychological and hypothalamic–pituitary-axis function in female patients with melancholic and non-melancholic depression

Executive function deficits in depression implicate involvement of frontal-striatal circuits. However, studies of hypothalamic-pituitary-axis (HPA) function suggest that stress-related brain changes of hippocampus may also implicate prefrontal-hippocampal circuits, which may explain the profile of both executive dysfunction and memory deficits. In this study we examined the performance of patients with major depressive disorder (MDD) on tasks of memory and executive function in relation to melancholic features and to cortisol levels. Our hypothesis was that raised cortisol levels in melancholic patients would correlate with these deficits. Forty female MDD patients, 20 having melancholic features (MEL vs. Non-MEL), and 20 sex-age- and education-matched normal controls were investigated using the Cambridge neuropsychological test automated battery (CANTAB), to assess memory (paired associative learning, PAL; short-term recognition memory, SRM) and executive (intradimensional/extradimensional set-shifting, ID/ED; Stockings of Cambridge, SOC) functions. Plasma and salivary cortisol levels were measured. The MDD patients performed worse than controls on PAL and both executive tasks. The MEL group differed from controls on all tests, and differed from the non-MEL only at the ED stage of the ID/ED task. Patient cortisol levels were within the normal range and did not correlate with neuropsychological performance for any group. MDD patients showed neuropsychological deficits on tasks of executive function and memory, supporting the model of frontal-temporal dysfunction. MEL vs. non-MEL performed worse overall and demonstrated a qualitative difference in set shifting, perhaps implicating more extensive prefrontal involvement. Cortisol levels did not correlate with depression severity or the observed deficits.

Melatonin protects against endosulfan‐induced oxidative tissue damage in rats

Endosulfan is a chlorinated cyclodiene insecticide which induces oxidative stress. In this study, we investigated the possible protective effect of melatonin, an antioxidant agent, against endosulfan (Endo)-induced toxicity in rats. Wistar albino rats (n = 8) were administered endosulfan (22 mg/kg/day orally) followed by either saline (Endo group) or melatonin (10 mg/kg/day, Endo + Mel group) for 5 days. In other rats, saline (control group) or melatonin (10 mg/kg/day, Mel group) was injected for 5 days, following corn oil administration (vehicle of endosulfan). Measurement of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content were performed in liver and kidney. Furthermore, aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), and creatinine levels, lactate dehydrogenase (LDH) activity were measured in the serum samples, while tumor necrosis factor-alpha (TNF-alpha), interleukin-beta (IL-beta) and total antioxidant capacity (AOC) were assayed in plasma samples. Endosulfan administration caused a significant decrease in tissue GSH and plasma AOC, which was accompanied with significant rises in tissue MDA and collagen levels and MPO activity. Moreover, the proinflammatory mediators (TNF-alpha and IL-beta), LDH activity, AST, ALT, creatinine and BUN levels were significantly elevated in the endosulfan-treated rats. On the other hand, melatonin treatment reversed all these biochemical alterations induced by endosulfan. Our results suggest that oxidative mechanisms play an important role in endosulfan-induced tissue damage and melatonin, by inhibiting neutrophil infiltration, balancing oxidant-antioxidant status and regulating the generation of inflammatory mediators, ameliorates oxidative organ injury as a result of endosulfan toxicity.

Melatonin ameliorates oxidative stress, inflammation, proteinuria, and progression of renal damage in rats with renal mass reduction

The progressive deterioration of renal function and structure resulting from renal mass reduction are mediated by a variety of mechanisms, including oxidative stress and inflammation. Melatonin, the major product of the pineal gland, has potent_antioxidant and anti-inflammatory properties, and its production is impaired in chronic renal failure. We therefore investigated if melatonin treatment would modify the course of chronic renal failure in the remnant kidney model. We studied rats followed 12 wk after renal ablation untreated (Nx group, n = 7) and treated with melatonin administered in the drinking water (10 mg/100 ml) (Nx + MEL group, n = 8). Sham-operated rats (n = 10) were used as controls. Melatonin administration increased 13-15 times the endogenous hormone levels. Rats in the Nx + MEL group had reduced oxidative stress (malondialdehyde levels in plasma and in the remnant kidney as well as nitrotyrosine renal abundance) and renal inflammation (p65 nuclear factor-kappaB-positive renal interstitial cells and infiltration of lymphocytes and macrophages). Collagen, alpha-smooth muscle actin, and transforming growth factor-beta renal abundance were all increased in the remnant kidney of the untreated rats and were reduced significantly by melatonin treatment. Deterioration of renal function (plasma creatinine and proteinuria) and structure (glomerulosclerosis and tubulointerstitial damage) resulting from renal ablation were ameliorated significantly with melatonin treatment. In conclusion, melatonin administration improves the course of chronic renal failure in rats with renal mass reduction. Further studies are necessary to define the potential usefulness of this treatment in other animal models and in patients with chronic renal disease.

Effect of melatonin on apoptosis, proliferation and differentiation of urothelial cells after cyclophosphamide treatment

Melatonin was recently shown to have protective effects against cyclophosphamide (CP)-induced hemorrhagic cystitis (HC) by diminishing bladder oxidative stress. HC is accompanied by destruction of the bladder urothelium and followed by apoptosis and rapid regeneration via proliferation and differentiation of urothelial cells, reaching complete restoration of normal urothelium in three weeks. Therefore, the effect of melatonin on apoptosis, proliferation and differentiation of urothelial cells, during destruction and regeneration of the urothelium three-weeks after a single dose CP treatment, was studied. F344 male rats were injected intraperitoneally with saline (control group) or melatonin (Mel group) or a single dose of CP (100 mg/kg; CP group) or melatonin (10 mg/kg) with CP (Mel + CP group). Melatonin co-treatment with CP significantly reduced apoptosis and increased proliferation of urothelial cells at day 1 and thus prevented extensive loss of cells from the urothelium. However, proliferation indices at days 4 and 7 after melatonin and CP co-treatment suddenly dropped and therefore the development of hyperplasia was prevented. Melatonin co-treatment with CP also resulted in earlier differentiation of superficial urothelial cells. Melatonin seems to have protective effect against CP-induced urothelial damage and a favorable impact on regeneration and restoration of normal urothelium, since it reduces the number of apoptotic and proliferating urothelial cells and results in their earlier differentiation.

Neuroprotective effect of melatonin against ischemia/reperfusion-induced neuronal apoptosis in mouse cerebellum

Background Some experiments have demonstrated that melatonin (N-aceyl-5-methoxytryptamine, Mel) has antioxidation. However, whether it has neuroprotective effect in the ischemia/reperfusion injury of central nervous system is unclear. Objective To observe the protective effect of Mel on ischemia/reperfusion-induced cerebellar neuronal apoptosis of rats, and the action mechanism. Design Controlled observation experiment. Setting Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology. Materials Eight Sprague-Dawley rats aged 7–8 days and weighing 10–12 g were provided by Medical Experimental Animal Center, Tongji Medical College, Huazhong University of Science and Technology. Anti-cytochrome C monoclonal antibody was purchased from R & D Company; 7-dichlorodihydrofluorescein diacetate(DCFH-DA), rhodamine 123 and Mel were purchased from Sigma Company (USA). Lactate dehydrogenase (LDH) kit was purchased from Nanjing Jiancheng Bioengineering Institute. Methods This experiment was carried out in the laboratory for Department of Biochemistry and Molecule Biology, Tongji Medical College between October 2002 and March 2004. Cerebellar neurons of rats were cultured in vitro. After oxygen-glucose deprivation (OGD) for 90 minutes, 1×10 −4,1×10 −6, 1×10 −9 mol/L Mel was added, respectively, namely high-, middle-, and low-concentration Mel groups. Cells, which were cultured by OGD, served as model group, and control group, in which OGD intervention was omitted, was set. ▪Cytochrome C level of mitochondrial cells in each group was detected by ELISA method. ▪LDH activity in the cell culture fluid was measured, and cell membrane permeability change was analyzed. The cells in the Mel group with the lowest LDH activity served as Mel treatment group, i.e. cells were cultured with OGD, and then Mel was added; Meanwhile, Mel prevention group was set, i.e. Mel was added before OGD. Intervention was not changed in the model group and control group. ▪ DNA level was analyzed and cell apoptosis was observed by agarose gel electrophoresis(AGE). ▪Mitochondrial transmembrane potential of cells, and apoptotic way in each group were analyzed by confocal laser scanning microscopy. Main Outcome Measures ▪Mitochondrial cytochrome C level of cerebellar nerve cells. ▪LDH activity of cerebellar nerve cells. ▪ DNA AGE results. ▪Mitochondrial transmembrane potential change. Results ▪Mitochondrial cytochrome C level of cerebellar nerve cells: cytochrome C was obviously released at 6 hours of OGD-reperfusion. Mel inhibited the release of cytochrome C in dose-dependent manner. ▪LDH activity of cerebellar nerve cells: LDH activity ( A value) was significantly lower in the high- and middle-concentration Mel groups than in the model group ( P < 0.05). LDH activity ( A value) in the low-concentration Mel group was 0.415 0±0.012 9, indicating that Mel could decrease LDH activity of OGD-treated cell supernatant and promote membrane stablization in dose-dependent manner. ▪AGE results of DNA: 1×10 −9 mol/L was considered as the best concentration of melatonin. Cell DNA was extracted for AGE. Results presented typical ladder shape, indicating apoptosis appeared, while apoptosis was lessened in the Mel treatment group and Mel prevention group. ▪Mitochondrial transmembrane potential change: Experimental results showed that green fluorescein was evenly distributed in cerebellar granule cells cultured normally, and the axons of neurons were very clear. The body of neurons was condensed and the axons disappeared after cerebellar granule cells undergoing OGD injury. Mel could completely reverse the effect of OGD. Conclusion Mel can enhance cerebellar neuronal membrane stabilization of rats in dose-dependent manner, and suppress OGD-induced apoptosis of cerebellar granule cells by preventing against mitochondrial apoptosis.

Long‐term morphological and functional evaluation of the neuroprotective effects of post‐ischemic treatment with melatonin in rats

Consensus on neuroprotection has pointed out the relevance of the long-term morphological and functional evaluation of the effectiveness of putative neuroprotective procedures. In the present study, place learning (Morris water maze) and working memory (eight-arm Olton radial maze) were evaluated in adult male rats 90 days after 15 min of global cerebral ischemia (four-vessel occlusion) followed by continuous i.v. infusion (10 mg/kg/hr) of melatonin (Isch + Mel) or vehicle (Isch + Veh) for 6 hr, and the pyramidal neuron population of the cornus Ammoni (CA) of the hippocampus and layers III and V of the medial prefrontal cortex was assessed at the end of the behavioral testing period (120 days after ischemia). Impairment of place learning, a significant delay in working memory acquisition, and a significant loss of pyramidal neurons in the Ammon's horn (CA1: 23%, CA2: 52% CA3: 73%, hilus: 64% remaining neurons), were observed in the Isch + Veh group. By contrast, a similar performance of the Isch + Mel group to that in the Intact and Sham groups and better than that of the Isch + Veh group, besides a significant reduction of pyramidal neuron loss in the CA subfields (CA1: 79%, CA2: 88% CA3: 86%, hilus: 72% remaining neurons), documented that melatonin treatment led to a long-term preservation of both the neural substrate, and the capability for integration of spatial learning and memory, mainly dependent on a normal hippocampal functioning. Overall the results emphasize the efficacy of melatonin in counteracting the pathophysiological processes induced by ischemia, by exerting its actions during a short but critical period early after the ischemic episode.

Melatonin protects against ischemia/reperfusion injury in skeletal muscle

Melatonin has been shown to diminish ischemia-reperfusion (I/R) injury in many tissues. The main aim of this study was to evaluate the protective antioxidant effect of melatonin in skeletal muscle during I/R injury. Wistar albino rats were randomly divided into three groups. Hindlimb ischemia was achieved by clamping the common femoral artery in two groups but not in control group. Limbs were rendered ischemic for 1.5 hr; at the end of the reperfusion period of 1.5 hr muscle tissue samples were taken for the histological evaluation and biochemical analysis. Melatonin (10 mg/kg) was injected i.p. in the I/R + Mel group at the onset of ischemia whereas the vehicle solution was injected in the I/R group. In I/R + Mel group histological damage was significantly less than in the I/R group (P < 0.001). In the I/R + Mel group, the mean malonedialdehyde level was lower than in the I/R group (P < 0.01) and was quite near to the levels in the control group (P > 0.05). Glutathione levels were found to be reduced in the I/R group compared with the control (P < 0.01) and I/R + Mel group (P < 0.01). Melatonin has a protective effect against I/R injury in skeletal muscle and may reduce the incidence of compartment syndrome, especially after acute or chronic peripheral arterial occlusions.

Role of Melatonin in Reducing Water Avoidance Stress-Induced Degeneration of the Liver

Melatonin, a pineal secretory product, is a potent scavenger of a variety of free radicals. We investigated the role of melatonin on water avoidance stress (WAS)-induced degenerations of the liver parenchyme. Wistar albino rats were exposed to acute WAS (aWAS group) or chronic WAS (cWAS group). Before exposing animals to acute (aWAS + mel group) or chronic WAS (cWAS + mel group), 10 mg/kg melatonin was injected i.p. The liver samples were investigated under light and transmission electron microscope. Malondialdehyde (MDA) and glutathione (GSH) levels were also determined. Prominent vascular congestion and dilated sinusoids, activated Kupffer cells with prominent morphology, dilated granular endoplasmic reticulum membranes, and focal picnotic nuclei were observed in the aWAS group; these morphological changes were severe in the cWAS group. MDA level was increased and GSH level was decreased significantly in the cWAS group. The morphology of liver parenchme in both the aWAS + mel and the cWAS + mel group showed that melatonin significantly reduced the degeneration in liver; besides, a significant decrease in MDA and an increase in GSH levels were observed in the cWAS + mel group. Based on the results, melatonin treatment significantly prevented WAS-induced morphological and biochemical changes in liver parenchyma.

The protective effects of melatonin against water avoidance stress-induced mast cell degranulation in dermis

Nontraumatic psychological water avoidance stress has been shown to induce mucosal degeneration, inflammatory cell infiltration and mast cell degranulation in stomach, ileum, colon and urinary bladder. Many skin disorders, such as atopic dermatitis and psoriasis, worsen during stress and seem to be related with infiltration and activation of mast cells releasing vasoactive and proinflammatory mediators. Melatonin is a free radical scavenger and has cytoprotective effects in inflammatory conditions. The aim of the present study was to investigate the effects of melatonin on water avoidance stress (WAS)-induced degranulation of mast cells in the dermis. Wistar rats were exposed to acute WAS (aWAS group) or chronic WAS (cWAS group). Before exposing to acute WAS, one group of animals was treated with 10mg/kg melatonin (aWAS+mel group). In the cWAS+mel group, treatment with melatonin lasted for 5 days. Dermal mast cells were stained with toluidine blue and investigated using light microscopy. Numbers of mast cells were increased in both aWAS and cWAS groups, but numbers of degranulated mast cells were increased significantly only in the cWAS group when compared to the control group. Numbers of mature granulated and degranulated mast cells were decreased in the cWAS+mel group when compared to the cWAS group. In conclusion, chronic melatonin treatment reduced WAS-induced infiltration and activation of mast cells in dermis and may provide a useful therapeutic option in stress-induced skin disorders.

Radioprotective Effects of Melatonin on Radiation-Induced Cataract

One of the mechanisms proposed to explain lens opacification is the oxidation of crystallins, either by radiation or reactive oxygen species (ROS). It has been shown that melatonin has both an anti-peroxidative effect on several tissues and a scavenger effect on ROS. The purpose of this study was to determine the antioxidant role of melatonin (5 mg/kg/day) against radiation-induced cataract in the lens after total-cranium irradiation of rats with a single dose of 5 Gy. Sprague-Dawley rats were divided into four groups. Control group received neither melatonin nor irradiation. Irradiated rats (IR) and melatonin+irradiated rats (IR+Mel) groups were exposed to total cranium irradiation of 5 Gy in a single dose by using a cobalt-60 teletherapy unit. IR+Mel and melatonin (Mel) groups were administered 5 mg/kg melatonin daily by intraperitoneal injections during ten days. Chylack's cataract classification was used in this study. At the end of the 10th day, the rats were killed and their eyes were enucleated to measure the antioxidant enzymes i.e. the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and lipid peroxidation level (malondialdehyde (MDA)). Irradiation significantly increased the MDA level, as an end product of lipid peroxidation, and also significantly decreased SOD and GSH-Px activity, emphasizing the generation of increased oxidative stress. Rats injected with melatonin only did not cause cataract formation. Melatonin supplementation with irradiation significantly increased the activity of SOD and GSH-Px enzymes and significantly decreased the MDA level. Total cranium irradiation of 5 Gy in a single dose enhanced cataract formation, and melatonin supplementation protected the lenses from radiation-induced cataract formation. Our results suggest that supplementing cancer patients with adjuvant therapy of melatonin may reduce patients suffering from toxic therapeutic regimens such as chemotherapy and/or radiotherapy and may provide an alleviation of the symptoms due to radiation-induced organ injuries.

Effects of melatonin on carbon tetrachloride-induced changes in rat serum

Carbon tetrachloride (CCl4) is a volatile organic chemical, which causes tissue damage, especially to the liver and kidney. In experimental animals it has been shown to be carcinogenic. This study was designed to evaluate the effects of exogenous melatonin administration on the CCl4-induced changes of some biochemical parameters in rat blood. Twenty-four male Wistar rats were randomly divided into three equal groups: Control, CCl4 and CCl4 plus melatonin (CCl4+MEL). Rats in CCl4 group were injected subcutaneously with CCl4 0.5 ml/kg in olive oil while rats in CCl4+MEL group were injected with CCl4 (0.5 ml/kg) plus melatonin (25 mg/kg in 10% ethanol) every other day for one month. Control rats were treated with olive oil. Serum urea, creatinine, total protein, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total and conjugated bilirubin, alkaline phosphatase (ALP), gamma-glutamyl transferase (gamma-GT), total iron, and magnesium levels were determined. Serum AST, ALT, total and conjugated bilirubin, ALP, gamma-GT, and total iron levels were significantly higher in CCl4-treated rats than in the controls, while urea, total protein, and albumin levels were significantly lower. Melatonin treatment did not cause a significantly change in serum urea, total protein, and albumin levels. However, the elevations in AST, ALT, total and conjugated bilirubin, ALP, gamma-GT, and total iron levels induced by CCl4 injections were significantly reduced by melatonin. On the other hand, melatonin administration significantly decreased serum magnesium levels. These results indicate that melatonin could be a protective agent against the CCl4 toxicity in rats, most likely through its antioxidant and free radical scavenger effects.

Prevention of mobile phone induced skin tissue changes by melatonin in rat: an experimental study

Most of the mobile phones in Turkey emit 900 MHz radiation which is mainly absorbed by the skin and, to a lesser extent, muscle. The aim of this study was to investigate the effects the 900 MHz electromagnetic irradiation emitted by these devices on the induction of histopathologic changes in skin and the effect of melatonin (Mel) on any of these changes. Thirty male Wistar-Albino rats were used in the study. The experimental groups were composed of: a nontreated control group, an irradiated group (IR) without Mel and an irradiated with Mel treatment group (IR + Mel). 900 MHz radiation was applied to IR group for 10 days (30 min/day). The IR + Mel group received 10 mg/kg per day melatonin in tap water for 10 days before irradiation. At the end of the tenth day, the skin graft was excized from the thoraco-abdominal area. Histopathologic changes in skin were analyzed. In the IR group, increased thickness of stratum corneum, atrophy of epidermis, papillamatosis, basal cell proliferation, increased granular cell layer (hypergranulosis) in epidermis and capillary proliferation, impairment in collagen tissue distribution and separation of collagen bundles in dermis were all observed compared to the control group. Most of these changes, except hypergranulosis, were prevented with melatonin treatment. In conclusion, exposure to 900 MHz radiation emitted by mobile phones caused mild skin changes. Furthermore, melatonin treatment can reduce these changes and may have a beneficial effect to prevent 900 MHz mobile phone-induced rat skin changes.

Role of melatonin in reducing water avoidance stress-induced degeneration of the gastrointestinal mucosa.

We investigated the role of melatonin on water avoidance stress (WAS)-induced degeneration of the gastric, ileal and colonic mucosa. Wistar albino rats were exposed to acute WAS (aWAS group) or chronic WAS (cWAS group). Before exposing animals to acute (aWAS + mel group) or chronic WAS (cWAS + mel group), 10 mg/kg melatonin was injected i.p. The stomach, ileum and colon samples were investigated under light and scanning electron microscope. Malondialdehyde (MDA) and glutathione (GSH) levels were also determined. In both aWAS and cWAS groups, the epithelium of stomach showed ulceration in some areas, dilatations of the gastric glands and degeneration of gastric glandular cells; prominent congestion of the capillaries after WAS was apparent. In the cWAS group, severe vascular congestion was observed along with degeneration of ileal and colonic epithelium. MDA levels were increased and GSH levels were decreased in all tissues in both the aWAS and cWAS groups. The morphology of gastric, ileal and colonic mucosa in both aWAS + mel and cWAS + mel groups showed that the indole significantly reduced degeneration of the gastrointestinal mucosa. Decreased MDA and increased GSH levels were observed in the WAS + mel groups. Based on the results, melatonin treatment significantly prevented WAS induced degenerative morphological and biochemical changes of gastrointestinal mucosa.

Melatonin attenuates ifosfamide-induced Fanconi syndrome in rats.

Regarding the mechanisms of ifosfamide (IFO)-induced nephrotoxicity and hemorrhagic cystitis, several hypotheses have been put forward, among which oxidative stress and depletion of glutathione (GSH) are suggested. This investigation elucidates the role of free radicals in IFO-induced toxicity and the protection by melatonin. Wistar albino rats were injected intraperitoneally with saline (0.9% NaCl; control-C group), melatonin (Mel group; 10 mg/kg daily for 5 days) or ifosfamide (50 mg/kg daily for 5 days; IFO group) or IFO + Mel. On the 5th day (120 hr) after the first IFO dose, animals were killed by decapitation and trunk blood was collected. Kidney and bladder tissues were obtained for biochemical and histological analysis. Urine was collected 24 hr before the rats were killed. The results demonstrated that IFO induced a Fanconi syndrome (FS) characterized by wasting of sodium, phosphate, and glucose, along with increased serum creatinine and urea. Melatonin markedly ameliorated the severity of renal dysfunction induced by IFO with a significant decrease in urinary sodium, phosphate, and glucose and increased creatinine excretion. Moreover, melatonin significantly improved the IFO-induced GSH depletion, malondialdehyde accumulation and neutrophil infiltration in both renal and bladder tissues. In the kidney, Na+,K+ -ATPase activity which was significantly reduced by IFO, was increased with melatonin treatment. Increased collagen contents of the kidney and bladder tissues by IFO treatment were reversed back to the control levels with melatonin. Our results suggest that IFO causes oxidative damage in renal and bladder tissues and melatonin, via its antioxidant effects, protects these tissues. These data suggest that melatonin may be of therapeutic use in preventing acquired FS due to IFO toxicity.