Ultrastructural clues for the protective effect of ascorbic acid and N-acetylcysteine against oxidative damage on caerulein-induced pancreatitis.

BACKGROUND: Oxygen free radicals (OFR) have been implicated in the induction of acute pancreatitis (AP). AIMS: The aim of this study was to determine the effect of ascorbic acid and N-acetylcysteine (NAC), potent antioxidants, against oxidative stress in AP. METHODS: AP was induced by two i.p. injections of caerulein at 2-hour intervals (50 microg/kg BW). One group received additionally an antioxidant mixture composed of L(+)-ascorbic acid (14.3 mg/kg BW) and NAC (181 mg/kg BW) i.p. The rats were sacrificed 12 h after the last injection. Oxidative stress markers were evaluated. Light-microscopic and ultrastructural examination was performed. RESULTS: Formation of vacuoles, mitochondrial damage, and dilatation of rough endoplasmic reticulum, margination and clumping of chromatin were major ultrastructural alterations in AP group. Ascorbic acid + NAC prevented these changes. Small vacuoles were present within the cytoplasm of some of the acinar cells. Pancreas damage was accompanied by an increase in tissue malondialdehyde (MDA) levels (p < 0.05), whereas a decrease was seen in catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) activities and total glutathione (GSH) levels (p < 0.005). Ascorbic acid + NAC decreased MDA levels but increased CAT, SOD, GPx activities and GSH levels (p < 0.005). CONCLUSION: These results suggest that ascorbic acid + NAC is potentially capable of limiting pancreatic damage produced during AP via protecting fine structure of acinar cells and tissue antioxidant enzyme activities.     

The Beneficial Effects of Pentoxifylline on Caerulein-Induced Acute Pancreatitis in Rats

In this study we aimed to investigate the effect of pentoxifylline on caerulein-induced acute pancreatitis (AP) by detecting oxidative stress markers and performing histopathological examination. Twenty-one adult female Sprague–Dawley rats were divided into three groups as follows: control, caerulein, and caerulein + pentoxifylline groups. Pancreatic tissues of rats from all groups were removed for light and electron microscopic examination and determination of oxidative stress markers. Pancreatic oxidative stress markers were evaluated by the measurements of malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and total glutathione (GSH). Serum amylase and lipase levels were determined spectrophotometrically. The pancreatic damage score was significantly increased (P < 0.005) in the caerulein group, whereas it was decreased (P < 0.05) in the caerulein+ with pentoxifylline group. MDA levels, CAT, SOD, GPx, and GSH activities were significantly altered (P < 0.05, P < 0.005) in the caerulein group and indicated increased oxidative stress. Oxidative stress markers were normalized with pentoxifylline administration. Caerulein administration resulted in significant increase (P < 0.05) in amylase and lipase levels; pentoxifylline reduced the levels of these enzymes. Pentoxifylline is potentially capable of limiting pancreatic damage produced during AP by restoring the fine structure of acinar cells and tissue antioxidant enzyme activities. We concluded that pentoxifylline may have beneficial effects in the treatment of caerulein-induced AP.     

Antioxidative effect of melatonin, ascorbic acid and N-acetylcysteine on caerulein-induced pancreatitis and associated liver injury in rats

AIM: To investigate the role of oxidative injury in pancreatitis-induced hepatic damage and the effect of antioxidant agents such as melatonin, ascorbic acid and N-acetyl cysteine on caerulein-induced pancreatitis and associated liver injury in rats. METHODS: Thirty-eight female Wistar rats were used. Acute pancreatitis (AP) was induced by two i.p. injections of caerulein at 2-h intervals (at a total dose of 100μg/kg b.wt). The other two groups received additional melatonin (20 mg/kg b.wt) or an antioxidant mixture containing L( )-ascorbic acid (14.3 mg/kb.wt.) and N-acetyl cysteine (181 mg/kg b.wt.) i.p. shortly before each injection of caerulein. The rats were sacrificed by decapitation 12 h after the last injection of caerulein. Pancreatic and hepatic oxidative stress markers were evaluated by changes in the amount of lipid peroxides measured as malondialdehyde (MDA) and changes in tissue antioxidant enzyme levels, catalase (CAT) and glutathione peroxidase (GPx). Histopathological examination was performed using scoring systems. RESULTS: The degree of hepatic cell degeneration, intracellular vacuolization, vascular congestion, sinusoidal dilatation and inflammatory infiltration showed a significant difference between caerulein and caerulein melatonin (P=0.001), and careulein and caerulein L( )-ascorbic acid N-acetyl cysteine groups (P=0.002). The degree of aciner cell degeneration, pancreatic edema, intracellular vacuolization and inflammatory infiltration showed a significant difference between caerulein and caerulein melatonin (P=0.004), and careulein and caerulein L( )-ascorbic acid N-acetyl cysteine groups (P=0.002). Caerulein-induced pancreatic and liver damage was accompanied with a significant increase in tissue MDA levels (P=0.01, P=0.003, respectively) whereas a significant decrease in CAT (P=0.002, P=0.003, respectively) and GPx activities (P= 0.002, P=0.03, respectively). Melatonin and L( )-ascorbic acid N-acetyl cysteine administration significantly decreased MDA levels in pancreas (P=0.03, P= 0.002, respectively) and liver (P=0.007,P=0.01, respectively). Administration of these agents increased pancreatic and hepatic CAT and GPx activities. Melatonin significantly increased pancreatic and hepatic CAT (P=0.002, P=0.001, respectively) and GPx activities (P= 0.002, P=0.001). Additionally, L( )-ascorbic acid N-acetyl cysteine significantly increased pancreatic GPx (P=0.002) and hepatic CAT and GPx activities (P=0.001, P=0.007, respectively) CONCLUSION: Oxidative injury plays an important role not only in the pathogenesis of AP but also in pancreatitis-induced hepatic damage. Antioxidant agents such as melatonin and ascorbic acid N-acetyl cysteine, are capable of limiting pancreatic and hepatic damage produced during AP via restoring tissue antioxidant enzyme activities.     

Melatonin ameliorates cerulein‐induced pancreatitis by the modulation of nuclear erythroid 2‐related factor 2 and nuclear factor‐kappaB in rats

Abstract: Melatonin exhibits a wide variety of biological effects, including antioxidant and anti‐inflammatory functions. Its antioxidant role impedes the etiopathogenesis of pancreatitis, but little is known about the signaling pathway of melatonin in the induction of antioxidant enzymes in acute pancreatitis (AP). The aim of this study was to determine whether melatonin could prevent cerulein‐induced AP through nuclear factor erythroid 2‐related factor 2 (Nrf2) and curtail inflammation by inhibition of NF‐κB. AP was induced by two intraperitoneal (i.p.) injections of cerulein at 2 h intervals (50 μg/kg) in Sprague‐Dawley rats. Melatonin (10 or 50 mg/kg/daily, i.p.) was administered 24 h before each injection of cerulein. The rats were killed 12 h after the last injection. Acinar cell degeneration, pancreatic edema, and inflammatory infiltration were significantly different in cerulein‐ and melatonin‐treated rats. Melatonin significantly reduced amylase, lipase, MPO, and MDA levels, and increased antioxidant enzyme activities including SOD and GPx, which were decreased in AP (P < 0.05). Melatonin increased the expression of NQO1, HO‐1, and SOD2 when compared with the cerulein‐induced AP group (P < 0.05). In addition, melatonin increased Nrf2 expression, and reduced expressions of tumor necrosis factor‐alpha, IL‐1β, IL‐6, IL‐8, and iNOS. The elevated nuclear binding of NF‐κB in the cerulein‐induced pancreatitis group was inhibited by melatonin. These results show that melatonin increases antioxidant enzymes and Nrf2 expression, and limits inflammatory mediators in cerulein‐induced AP. It is proposed that melatonin may play an important role in oxidative stress via the Nrf2 pathway in parallel with reduction of inflammation by NF‐κB inhibition.     

Melatonin ameliorates chronic renal failure-induced oxidative organ damage in rats

Chronic renal failure (CRF) is associated with oxidative stress that promotes production of reactive oxygen species (ROS). Melatonin, the chief secretory product of the pineal gland, was recently found to be a potent free radical scavenger and antioxidant. The aim of this study was to examine the role of melatonin in protecting the aorta, heart, corpus cavernosum, lung, diaphragm, and kidney tissues against oxidative damage in a rat model of CRF, which was induced by five of six nephrectomy. Male Wistar albino rats were randomly assigned to either the CRF group or the sham-operated control group, which had received saline or melatonin (10 mg/kg, i.p.) for 4 wk. CRF was evaluated by serum blood urea nitrogen (BUN) level and creatinine measurements. Aorta and corporeal tissues were used for contractility studies, or stored along with heart, lung, diaphragm, and kidney tissues for the measurement of malondialdehyde (MDA, an index of lipid peroxidation), protein carbonylation (PC, an index for protein oxidation), and glutathione (GSH) levels (a key antioxidant). Plasma MDA, PC, and GSH levels and erythrocytic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were studied to evaluate the changes of antioxidant status in CRF. In the CRF group, the contraction and the relaxation of aorta and corpus cavernosum samples decreased significantly compared with controls (P < 0.05-0.001). Melatonin treatment of the CRF group restored these responses. In the CRF group, there were significant increases in tissue MDA and PC levels in all tissues with marked reductions in GSH levels compared with controls (P < 0.05-0.001). In the plasma, while MDA and PC levels increased, GSH, SOD, CAT, and GSH-Px activities were reduced. Melatonin treatment reversed these effects as well. In this study, the increase in MDA and PC levels and the concomitant decrease in GSH levels of tissues and plasma and also SOD, CAT, GSH-Px activities of plasma demonstrate the role of oxidative mechanisms in CRF-induced tissue damage, and melatonin, via its free radical scavenging and antioxidant properties, ameliorates oxidative organ injury. CRF-induced dysfunction of the aorta and corpus cavernosum of rats was reversed by melatonin treatment. Thus, supplementing CRF patients with adjuvant therapy of melatonin may have some benefit.     

Age-related changes in the rat brain mitochondrial antioxidative enzyme ratios: Modulation by melatonin

Oxidative stress is an important factor for aging. The antioxidative enzymes glutathione peroxidase (GPx), glutathione reductase (GRd) and superoxide dismutase (SOD) play a crucial role protecting the organism against the age-dependent oxidative stress. Glutathione (GSH) is present in nearly all living cells. GSH is one of the main antioxidants in the cell and it serves several physiological functions. Our purpose was to evaluate the age-related changes in mitochondrial GPx, GRd and SOD activities, and mitochondrial GSH pool in the brains of young (3months) and aged rats (24months). We also investigated whether melatonin administration influences these brain mitochondrial enzyme activities and GSH levels in young and aged rats. The results showed that GPx activity increased with age, whereas melatonin treatment decreased GPx activity in the aged rats at levels similar to those in young and young+melatonin groups. The activities of GRd and SOD, however, did not change with age. But, melatonin treatment increased SOD activity in the aged rats. GSH levels, which also increased with age, were not modified by melatonin treatment. The reduction in the SOD/GPx and GR/GPx ratios with age was prevented by melatonin administration. Together, our results suggest that the age-related oxidative stress in rat brain mitochondria is more apparent when the antioxidant enzyme ratios are analyzed instead of their absolute values. The antioxidative effects of melatonin were also supported by the recovery of the enzyme ratios during aging.     

Prevention by melatonin of hepatocarcinogenesis in rats injected with N-nitrosodiethylamine

N-nitrosodiethylamine (NDEA) is a potent carcinogenic agent that induces liver cancer. To evaluate the chemopreventive function of melatonin in this experimental model, Wistar male rats received a single i.p. injection of NDEA or vehicle followed by weekly s.c. injections of carbon tetrachloride or vehicle for 6 weeks. Melatonin (5 mg/kg body weight) or its vehicle (0.5 mL saline) was given i.p. on a daily basis 2 hr before lights off for 20 wk. At the end of this period the rats were killed and liver and blood samples were taken for histological and biochemical studies. As markers for liver function, the activity of aspartate transaminase (AST) and alanine transaminase (ALT) and the levels of alpha-fetoprotein were measured in serum. To assess lipid peroxidation and the antioxidant status in liver and blood, the levels of thiobarbituric acid reactive substances (TBARS) and of reduced glutathione (GSH) were measured. The activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) was assessed in liver and erythrocyte fraction of NDEA-treated rats. NDEA administration inhibited body weight, macro- and microscopically detectable liver tumors and increased levels of plasma AST, ALT and alpha-fetoprotein. NDEA treatment decreased liver TBARS levels and CAT and SOD activities and increased liver GSH levels and GST and GPx activities. Plasma TBARS were augmented, while plasma GSH levels and the activities of erythrocyte CAT, SOD, GST and GPx decreased, in NDEA-treated rats. Melatonin administration significantly curtailed tumor development and counteracted all the biochemical effects.     

Melatonin administration differentially affects age-induced alterations in daily rhythms of lipid peroxidation and antioxidant enzymes in male rat liver

A central clock/pacemaker, suprachiasmatic nuclei of the hypothalamus coordinates and entrains circadian oscillations in the peripheral tissues such as the liver, kidney, heart, lungs etc. called peripheral clocks. These also have endogenous circadian oscillations. The circadian rhythms of antioxidants present in cytosol signify redox state of the cell during day/night cycle. The liver has a major impact on homeostasis through its control on serum protein composition and plays a pivotal role in the metabolism of nutrients, drugs, hormones, and metabolic waste products and undergoes substantial changes in structure and function upon aging. In present study, the temporal patterns of oxidative stress indicators in liver were studied. Daily rhythms of lipid peroxidation end products, reduced glutathione (GSH), oxidized glutathione (GSSG) and antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were studied in liver at variable time points (Zeitgeber Time (ZT) 0, 6, 12 and 18) in three age groups: 3 (adult), 12 and 24?months old male Wistar rats. There was increase in oxidative stress in 12 and 24?months old rats indicated through a significant increase in lipid peroxidation, decrease in GSH/GSSG ratio and antioxidant enzyme activities. In 3?months old rats, lipid peroxidation was maximum at ZT-12 whereas GSH, SOD and CAT activities were minimum at ZT-12. The maximum level in 24?h i.e., acrophases of lipid peroxidation, GPx, SOD and CAT activities in liver cell free extracts altered upon aging. As melatonin, messenger of darkness, an endogenous synchronizer of rhythm, an antioxidant and an antiaging drug, declines with aging we studied the effects of melatonin on activities of these antioxidant enzymes in aging rats. Melatonin administration resulted in differential restoration of acrophases, amplitude, mean as well as daily rhythms of lipid peroxidation and antioxidants in liver of 12 and 24?months old rats.     

Melatonin prevents oxidative stress and changes in antioxidant enzyme expression and activity in the liver of aging rats

This study compared the effects of melatonin supplementation on markers of oxidative stress, and on the activity and expression of antioxidant enzymes in the liver of young (3-month-old) and aging (24-month-old) rats. Animals were supplemented with melatonin in the drinking water (20 mg/L) for 4 wk. Liver concentration of thiobarbituric-reactive substances (TBARS), as an index of lipid peroxidation, and the oxidized to reduced glutathione ratio significantly increased in aged rats (+58%), while values did not significantly differ from the young in aged animals receiving melatonin. Significant decreases in the liver activities of Cu,Zn-superoxide dismutase (SOD) (-25%), cytosolic (-21%) and mitochondrial (-40%) glutathione peroxidase (GPx), and catalase (CAT) (-34%) were found in aged rats. Melatonin abolished these changes and also prevented the reduction of Cu,Zn-SOD (-33%), cytosolic GPx (-30%), and mitochondrial GPx (-47%) liver protein content as measured by Western blot. Reductions in Cu,Zn-SOD mRNA (-39%), and GPx mRNA (-86%) levels induced by aging were also abolished by melatonin. In summary, our data indicate that melatonin treatment abrogates oxidative stress in the liver of aged rats, and that prevention of the decreased activity of CAT and the downregulation of Cu,Zn-SOD and GPx gene expression contribute to this effect.     

Melatonin stimulates the activity of protective antioxidative enzymes in myocardial cells of rats in the course of doxorubicin intoxication

The study aimed at determining the effect of melatonin on the activity of protective antioxidative enzymes in the heart and of lipid peroxidation products in the course of intoxication with doxorubicin (DOX). The rats were categorized into four groups, receiving: 0.9% NaCl i.p. (NaCl control); melatonin [20 mg/kg body weight (b.w.)] s.c. (control Mel); DOX (2.5 mg/kg b.w.) i.p.; melatonin plus DOX in doses as above. All the substances were administered once in a week for four consecutive weeks. Homogenates of heart tissue were examined for activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), levels of reduced glutathione (GSH) and of lipid peroxidation indices (MDA + 4-HDA). Administration of melatonin alone did not induce alterations in levels of MDA + 4-HDA, GSH, or in activity of GPx, SOD or CAT, as compared to the group receiving 0.9% NaCl. GSH levels decreased following DOX but remained at normal levels following DOX and melatonin. The level of MDA + 4-HDA increased following DOX, as compared with the control, a change prevented by the combination of DOX + melatonin. Activities of GPx, SOD and CAT were higher in groups receiving DOX and/or DOX plus melatonin than in control groups. Activity of CAT and the level of GSH in the group receiving DOX plus melatonin were significantly higher than in the group intoxicated with DOX alone. The obtained results demonstrate that, when given in parallel with DOX, melatonin protects cardiomyocytes from damaging effects of the cytostatic drug (reflected by the levels of MDA + 4-HDA). The protective effect resulted, in part from the augmented levels of GSH and from stimulation of CAT activity by melatonin in cardiomyocytes subjected to the action of DOX.     

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.     

Effect of melatonin on lipid peroxidation, glutathione and glutathione-dependent enzyme activities in experimental otitis media with effusion in guinea pigs

Melatonin plays a role in the prevention of oxidative damage. In the present study, we investigated whether the increased oxidative stress in experimental otitis media with effusion (OME) induced by histamine is reflected in erythrocytes and middle ear effusion fluid. Lipid peroxidation in effusion fluid was measured to determine the effects of melatonin on oxidative stress. Erythrocyte and middle ear effusion malondialdehyde (MDA) levels, erythrocyte glutathione (GSH) levels and glutathione peroxidase (GPx), glutathione reductase (GRd) and glutathione-S-transferase (GST) activities were measured in three groups of six guinea pigs each at 3 hr after the injection of 0.1 mL of histamine (or saline) into the middle ear. In erythrocyte and middle ear effusion samples, MDA levels showed a significant increase in guinea pigs with experimental OME group when compared with the control animals. Erythrocyte GPx, GST, GRd activities and GSH levels significantly reduced in experimental OME guinea pigs when compared with the control and melatonin-treated animals. Erythrocyte GPx activity also significantly increased after melatonin treatment when compared with the control group. These findings suggest that reactive oxygen species play a role in histamine-induced OME. Pretreatment with melatonin increases antioxidant enzyme activities and reduced formation of MDA, an indicator of lipid peroxidation, in histamine-induced OME.     

Preventive effect of melatonin on bleomycin-induced lung fibrosis in rats

Oxidative stress has an important role in the pathogenesis of idiopathic pulmonary fibrosis. Melatonin has direct and indirect free radical-detoxifying activity. The present study investigated whether melatonin treatment attenuates bleomycin-induced lung fibrosis in rats. A group of rats was given one dose of bleomycin while the control animals were given saline. The first dose of melatonin (4 mg/kg/day) was given 2 days before the bleomycin injection. At day 14, fibrotic changes were evaluated using Aschoft's criteria and lung hydroxyproline content. Bleomycin produced a 2.7-fold rise in the fibrosis score that was decreased 65% by melatonin (P < 0.05) and a 1.4-fold increase in hydroxyproline content which was completely prevented by melatonin. Protein carbonyl and thiobarbituric acid reactive substances levels, which were significantly elevated in the bleomycin treated rats, were significantly attenuated by melatonin. Bleomycin administration significantly reduced the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in lung tissue. The reduction in CAT activity was prevented by melatonin but SOD and GSH-Px were not influenced. These results revealed that melatonin may prevent the development of bleomycin-induced lung fibrosis via the repression of protein and lipid peroxidation.     

Melatonin provides neuroprotection by reducing oxidative stress and HSP70 expression during chronic cerebral hypoperfusion in ovariectomized rats

Abstract:  Oxidative stress is believed to contribute to functional and histopathologic disturbances associated with chronic cerebral hypoperfusion (CCH) in rats. Melatonin has protective effects against cerebral ischemia/reperfusion injury. This effect has mainly been attributed to its antioxidant properties. In the present study, we evaluate the effects of melatonin on chronic cerebral hypoperfused rats and examined its possible influence on oxidative stress, superoxide dismutase (SOD) activity, reduced glutathione (GSH) levels, and heat shock protein (HSP) 70 induction. CCH was induced by permanent bilateral common carotid artery occlusion in ovariectomized female rats. Extensive neuronal loss in the hippocampus at day 14 following CCH was observed. The ischemic changes were preceded by increases in malondialdehyde (MDA) concentration and HSP70 induction as well as reductions in GSH and SOD. Melatonin treatment restored the levels of MDA, SOD, GSH, and HSP70 induction as compared to the ischemic group. Histopathologic analysis confirmed the protective effect of melatonin against CCH-induced morphologic alterations. Taken together, our results document that melatonin provides neuroprotective effects in CCH by attenuating oxidative stress and stress protein expression in neurons. This suggests melatonin may be helpful for the treatment of vascular dementia and cerebrovascular insufficiency.     

Melatonin protects against rotenone-induced oxidative stress in a hemiparkinsonian rat model

In the present study, we evaluated the effect of melatonin, a well-known free radical scavenger and neuroprotector, against rotenone-induced oxidative stress in a hemiparkinsonian rat model. The effect of melatonin on glutathione (GSH) depletion caused by unilateral, intranigral infusion of rotenone was investigated employing a spectrofluorimetric procedure. We also studied the effect of melatonin on rotenone-induced changes in the antioxidant enzymes superoxide dismutase (SOD) and catalase in the cytosolic fractions of substantia nigra (SN), employing spectrophotometric procedures. Rotenone-induced hydroxyl radicals (*OH) in the isolated mitochondria, as measured employing a sensitive HPLC-electrochemical method, were significantly scavenged by melatonin. Melatonin treatment restored the rotenone-induced decrease in GSH level and changes in antioxidant enzyme (SOD and catalase) activities in the SN. Our results strongly indicate melatonin's beneficial use in Parkinson's disease therapy as an antioxidant.     

Antioxidative effects of melatonin administration in elderly primary essential hypertension patients

The imbalance of the redox state of the aging organism may be involved in the development of primary essential hypertension. Melatonin, a potent antioxidant agent, was found to exert a hypotensive effect and improve the function of the cardiovascular system. The aim of this study was to determine the influence of melatonin supplementation on oxidative stress parameters in elderly primary essential hypertensive (EH) patients, controlled by a diuretic (indapamide) monotherapy. The levels of malondialdehyde (MDA) and reduced glutathione (GSH), activities of Cu-Zn superoxide dismutase (SOD-1), catalase (CAT) and glutathione peroxidase (GSH-Px) in erythrocytes, the plasma level of nitrate/nitrite, the content of carbonyl groups of plasma proteins and morning melatonin levels in the serum of 17 elderly EH patients were determined at the baseline and after the 15th and 30th days of melatonin supplementation (5 mg daily). Melatonin administration resulted in a significant increase in the morning melatonin concentration, SOD-1 and CAT activities, and a reduction in the MDA level. Statistically significant alterations in the levels of GSH, nitrate/nitrite and carbonyl groups and the activity of GSH-Px were not observed. These results indicate an improvement in the antioxidative defense of the organism by melatonin supplementation in the examined group and may suggest melatonin supplementation as an additional treatment supporting hypotensive therapy in elderly EH patients.     

Melatonin protects against oxidative stress caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in the mouse nigrostriatum

We tested the hypothesis that melatonin acts as a powerful hydroxyl radical (*OH) scavenger in vivo in the brain, and interferes with oxidative stress caused by the parkinsonian neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We investigated the effect of melatonin on in vitro *OH production employing a Fenton-like reaction in test tubes, and ex vivo *OH generation in isolated mitochondria induced by 1-methyl-4-phenyl pyridinium (MPP+), as well as on in vivo *OH formation in the mouse striatum following systemic administration of MPTP. We also measured reduced glutathione (GSH) levels, and superoxide dismutase (SOD) activity in the nucleus caudatus putamen (NCP) and substantia nigra (SN), 7 days following MPTP and/or melatonin administration. Melatonin caused a significant and dose-dependent inhibition of the production of *OH in the in vitro, ex vivo and in vivo experimental conditions. Melatonin caused no changes in monoamine oxidase-B activity, in vitro in mitochondrial P2 fractions or in vivo following systemic administration. MPTP treatment in mice caused a significant depletion of GSH, and increased the specific activity of SOD both in SN and NCP on the seventh day. MPTP-induced GSH depletion was dose-dependently blocked in SN and NCP by melatonin. Higher doses of melatonin exhibited a synergistic effect on MPTP-induced increase in the SOD activity in the SN. These results suggest that while GSH inhibition is a direct consequence of *OH generation following neurotoxin administration, the increase in SOD activity is a compensatory mechanism for removing superoxide radicals generated as the result of MPTP. Our results not only point to the potency of melatonin in blocking the primary insults caused by MPTP, but also provide evidence for triggering secondary neuroprotective mechanisms, suggesting its use as a therapeutic agent in neurodegenerative disorders, such as Parkinson's disease.     

Inhibitory effect of melatonin on lung oxidative stress induced by respiratory syncytial virus infection in mice

Abstract: Previous research has shown that antioxidant (butylated hydroxyanisole) treatment ameliorates respiratory syncytial virus (RSV)‐induced disease and lung inflammation. Melatonin has been reported to exhibit a wide varieties of biological effects, including antioxidant and anti‐inflammation, and has no evident toxicity and side effect. But it is not known whether melatonin would modify RSV‐induced lung disease and oxidative stress. The present study was to establish the involvement of oxidative stress in the pathogenesis of RSV‐induced lung inflammation, and to investigate the protective effect of administration of melatonin in mice with RSV‐induced oxidative pulmonary injury for 4 days. Malondialdehyde (MDA), an end product of lipid peroxidation, and glutathione (GSH) and superoxide dismutase (SOD) and nitric oxide (NO) levels were evaluated in lung tissue homogenates by spectrophotometry. Hydroxyl radical (˙OH), one of the indicators of free radical formation, was also detected in lung homogenates by Fenton reaction. Tumor necrosis factor‐a (TNF‐a) concentrations in mouse serum were measured with ELISA assay. The results demonstrated that the mice intranasally inoculated with RSV resulted in oxidative stress changes by increasing NO, MDA and ˙OH levels, and decreasing GSH and SOD activities, whereas administration of melatonin significantly reversed all these effects. Furthermore, melatonin inhibited production of proinflammatory cytokines such as TNF‐a in serum of RSV‐infected mice. These results suggest that melatonin ameliorates RSV‐induced lung inflammatory injury in mice via inhibition of oxidative stress and proinflammatory cytokine production and may be as a novel therapeutic agent in virus‐induced pulmonary infection.     

Plasma oxidative stress parameters in men and women with early stage Alzheimer type dementia

It is well known that oxidative stress is one of the earliest events in Alzheimer's disease pathogenesis, indicating that may play a key role in this disease. In our study, we measured the levels of oxidative stress indicators (TBARS and protein carbonyls content) and the non-enzymatic (glutathione (GSH) and oxidized glutathione (GSSG)) and enzymatic (glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD)) defense systems in the plasma of 46 patients diagnosed of ATD and 46 age-matched controls. We found decreased levels in total GSH in ATD patients, although healthy control women showed lower levels of total GSH than healthy control men. On the contrary, we found increased levels of TBARS and carbonyl groups content in ATD patients in both genders. The activity of the plasma antioxidant enzymes showed no changes for SOD activity in ATD patients, independently of the gender, although western blot analysis showed an increase in SOD-1 protein. CAT activity was also decreased in ATD patients, although this decrease is mainly due to the decrease found in men but not in women. However, western blot analysis did not show differences in CAT protein between controls and ATD patients. Finally, a decrease of GPx activity was found in ATD patients in both genders. However, as with CAT protein, western blot analysis did not show differences in GPx protein between controls and ATD patients. Our results suggest that there is a defect in the antioxidant defense system that is incapable of responding to increased free radical production, which may lead to oxidative damage and the development of the pathological alterations that characterize the neurodegenerative disorder of patients with ATD. Thus, oxidative damage could be one important aspect for the onset of ATD and oxidative stress markers could be useful to diagnose the illness in their earliest stages through both non-invasive, reliable and cost-affordable methods.     

Melatonin reduces uranium-induced nephrotoxicity in rats

The protective role of exogenous melatonin on U-induced nephrotoxicity was investigated in rats. Animals were given single doses of uranyl acetate dihydrate (UAD) at 5 mg/kg (subcutaneous), melatonin at 10 or 20 mg/kg (intraperitoneal), and UAD (5 mg/kg) plus melatonin (10 or 20 mg/kg), or vehicle (control group). In comparison with the UAD-treated group only, significant beneficial changes were noted in some urinary and serum parameters of rats concurrently exposed to UAD and melatonin. The increase of U excretion after UAD administration was accompanied by a significant reduction in the renal content of U when melatonin was given at a dose of 20 mg/kg. Melatonin also reduced the severity of the U-induced histological alterations in kidney. In renal tissue, the activity of the superoxide dismutase (SOD) and the thiobarbituric acid reactive substances (TBARS) levels increased significantly as a result of UAD exposure. Following UAD administration, oxidative stress markers in erythrocytes showed a reduction in SOD activity and an increase in TBARS levels, which were significantly restored by melatonin administration. In plasma, reduced glutathione (GSH) and its oxidized form (GSSG) were also altered in UAD-exposed rats. However, only the GSSG/GSH ratio was restored to control levels after melatonin treatment. Oxidative damage was observed in kidneys. Melatonin administration partially restored these adverse effects. It is concluded that melatonin offers some benefit as a potential agent to treat acute U-induced nephrotoxicity.