The effects of melatonin against atherosclerosis-induced endothelial dysfunction and inflammation in hypercholesterolemic rats

The aim of this study was to investigate the effects of melatonin on the serum asymmetric dimethylarginine (ADMA) levels and the expressions of vaspin, visfatin, dimethylarginine dimethylaminohydrolase (DDAH), and signal transducer and activator of transcription-3 (STAT-3) for evaluation of endothelial function and inflammation in the hypercholesterolemic rats. Rats were divided into 5 groups: (1) control, (2) hypercholesterolaemia, (3) melatonin administrated concurrently with cholesterol diet, (4) melatonin administrated only last 2 weeks and fed with cholesterol diet, (5) atorvastatin administered only last 2 weeks fed with cholesterol diet. Although an increase was observed in the expressions of visfatin and STAT-3 and the serum ADMA levels, the vaspin and DDAH protein expressions were found to decrease with hypercholesterolemic diets. Melatonin was determined to restore all the parameters to the normal levels. In conclusion, melatonin may have protective and therapeutic effects on hypercholesterolaemia by regulating vaspin, STAT-3, DDAH, and ADMA signalling pathways and create similar effects with atorvastatin.

A new perspective on the pleiotropic blood pressure improvement effect of sitagliptin: downregulation of miRNA-155 and miRNA-21

INTRODUCTION

Deterioration of vascular responses is the crucial event in the initiation of cardiovascular problems in hypertension (HT) and diabetes mellitus (DM). A well-known oral antidiabetic, sitagliptin, has pleiotropic effects besides improving glycemic state in type-2 DM. This study aimed to investigate the therapeutic effect of sitagliptin on blood pressure with previously unassessed parameters of well-known pathophysiological processes and especially at the microRNA (miRNA) level where there are many unknowns.

METHODS

N-nitro-L-arginine methyl ester (L-NAME)-induced HT model was performed on nondiabetic male rats. Four groups (including 7 rats in each) were formed: normotensives, sitagliptin-treated, HT and sitagliptin-treated HT. Asymmetric dimethylarginine (ADMA), intercellular adhesion molecule-1 (ICAM-1) and tyrosine hydroxylase (TH), HT related miRNAs were evaluated. In-vitro vessel responses were observed.

RESULTS

L-NAME led to a significant increase in blood pressure. Hypertensives exhibited significantly increased contractile responses, consistent with increased ADMA, ICAM-1. Sitagliptin decreased TH levels but not statistically significantly. The new side of the study was the miRNA-21 and miRNA-155 expressions were in line with other parameters in both the HT and sitagliptin-treated HT groups.

CONCLUSION

Sitagliptin may control comorbidities, especially HT and introduces new targets to alleviate vascular responses. The new knowledge is; sitagliptin may show these effects through microRNAs (Tab. 2, Fig. 6, Ref. 46).

The Effects of Apitherapeutic Agents on Oxidative Stress in Serum Metabolic Parameters of Hypertensive Rats Created by Nitric Oxide Synthase Inhibited

Hypertension is a chronic disease affecting the whole world due to its clinical effects and complications. The reduction in the release and effect of NO is one of the mechanisms of hypertension formation. Hypertension disrupts the balance between oxidant and antioxidant mechanisms. In this study, we aimed to observe biochemical changes in the blood by treatment propolis, caffeic acid phenethyl ester (CAPE) and pollen in hypertensive rats via Nω-Nitro-L-arginine methyl ester (L-NAME). Rats were divided in five groups. Rats were given L-NAME (40 mg/kg, intraperitoneally) for 14 days to make hypertensive. L-NAME and bee products were administered together with rats for 14 days, then L-NAME for 14 days. All administrated ended 28 days. There was a statistically significant (P<0.05) decrease in blood pressure (BP) in the groups in which bee products were applied. Blood pressure was lower in the pollen treated group than in the CAPE and propolis treated group (P<0.05). Paraoxanase (PON1), total antioxidant status (TAS), total oxidant status (TOS), asymmetric dimethylarginine (ADMA), nuclear factor-κB (NF-κB) levels were measured in the blood samples in all groups. In the L-NAME group; PON1, TAS, HDL, and total protein levels were found to be lower than the groups applied bee products (P<0.05). TOS, oxidative stress index (OSI), ADMA, NF-κB, glucose, cholesterol, LDL, triglyceride, ALT, AST, ALP levels were found to be lower in groups plus of bee products were applied compared to the group that received L-NAME (P<0.05). The results showed that oxidative stress and homeostasis can be regulated with propolis, CAPE and pollen in hypertensive rats induced L-NAME.

The investigation of antioxidant and anti-inflammatory potentials of apitherapeutic agents on heart tissues in nitric oxide synthase inhibited rats via Nω-nitro-L-arginine methyl ester

BACKGROUND

High blood pressure effects heart and vessels. Development of pathogenesis is the result of oxidative stress. We aimed to investigate the antioxidant effects of propolis, caffeic acid phenethyl ester (CAPE), and pollen on the hearts of rats which chronic nitric oxide synthase (NOS) inhibited through Nω-nitro-L-arginine methyl ester (L-NAME). Paraoxonase 1 (PON1), total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), asymmetric dimethylarginine (ADMA), and nuclear factor-κB (NF-κB) were analyzed on the heart.

MATERIAL AND METHODS

Sprague-Dawley rats were divided five groups of seven rats in every group; Group I: Control, Group II: L-NAME, Group III: L-NAME+propolis, Group IV: L-NAME+CAPE and Group V: L-NAME+pollen. L-NAME become dissolved in regular saline (0.9% NaCl w/v). The ethanolic extract of propolis (200 mg/kg/days, gavage), pollen (100 mg/kg/days, by gavage), CAPE (50 µM/kg/days, intraperitoneally), and the NOS inhibitor L-NAME (40 mg/kg, intraperitoneally) had been administered.

RESULTS

Blood pressure (BP) of rats treated with propolis, CAP,E and pollen statistically significant decreased. Decreasing in BP of the rats of pollen group was more than CAPE and propolis groups (P < .05). PON1 and TAS levels decreased in L-NAME-treated groups (P < .05), but ranges have been better in propolis, CAPE and pollen groups. TOS, ADMA and NF-κB levels increased (P < .05) in L-NAME group; however, these parameters were lower (P < .05) in propolis and CAPE groups (P < .05).

CONCLUSIONS

Vasorelaxant properties and free radical scavenging actions of propolis, CAPE, and pollen may reduce the oxidative stress and blood pressure in the rats chronic NOS inhibited through L-NAME.

The inhibition of apoptosis through myocardial postconditioning by affecting Fas/FasIg signaling through miR139-3p and miR181a-1

BACKGROUND AND AIM OF THE STUDY

Ischemic postconditioning (PostC) is considered to be one of the strongest mechanisms limiting the extent of myocardial infarction, and reducing ischemia-reperfusion (I/R) injury. I/R-induced myocardial injury results in apoptosis, autophagy, and necrosis. The aim of the present study was to investigate the roles of the necrotic gene cytochrome b-245 beta chain (Cybb); Cybb-related microRNA miR139-3p; the autophagy gene Beclin-1 (Becn1); proapoptotic genes Fas, Faslg and growth arrest and DNA-damage-inducible 45 alpha (Gadd45a); and apoptosis-related microRNA miR181a-1 levels on I/R injury, as well as, the potential protective effects of PostC through this gene and microRNAs.

METHODS

The left main coronary artery was subjected to ischemia for 30 minutes, followed by reperfusion for 120 minutes. PostC involved three cycles of I/R, each lasting 10 seconds. Gene and microRNA levels were analyzed using a quantitative reverse transcription-polymerase chain reaction.

RESULTS

Although an increase was observed in the expression levels of the Cybb, Fas, Faslg and Gadd45a genes, the miR139-3p, miR181a-1, and Becn1 expression levels were found to decrease with I/R injury. PostC was determined to restore the expression of all the genes to the normal levels.

CONCLUSIONS

The abovementioned genes can be used as important prognostic markers in the diagnosis of reperfusion injury and in the evaluation of treatment efficacy. It was further noted that increased expression of CYBB, which is one of the target genes for miR139-3p, and a decreased expression of miR181a-1 may cause apoptosis by affecting Fas and Faslg signaling. PostC can inhibit apoptosis by increasing miR139-3p and miR181a-1 levels.

Physiological and pharmacological effects of melatonin on remote ischemic perconditioning after myocardial ischemia-reperfusion injury in rats: Role of Cybb, Fas, NfκB, Irisin signaling pathway

It has been found that remote organ/limb temporary ischemia, known as remote ischemic conditioning, can provide protection against the formation of lethal ischemic outcome. Current evidence suggests that aging and age-releated comorbidities impair the cardioprotective effects of conditionings. In conjuction with aging, decrease in melatonin synthesis from pineal gland can have role in the pathogenesis of aging and age-related cardiovascular diseases. In this study, we investigated the effects of remote ischemic perconditioning (RIPerC) and physiological and pharmacological concentrations of melatonin on the infarct size, Fas gene, cytochrome b-245 beta chain (Cybb) gene, nuclear factor-kappa B (NfκB), and irisin using an in vivo model of myocardial ischemia/reperfusion (I/R) injury. Sprague-Dawley rats that were divided into two groups first as non-pinealectomized (Non-Px) and pinealectomized (Px), and then (a) Control; (b) I/R (30-minute ischemia, 120-minute reperfusion caused by left coronary artery ligation); (c) I/R + RIPerC (when myocardial ischemia initiated, three cycles of 5-minute occlusion followed by 5-minute reperfusion); (d) I/R + Mel; (e) Px; (f) Px + I/R; (g) Px + I/R + RIPerC; (h) Px + I/R + RIPerC + Mel groups. The infarct size was determined by TTC staining and analyzed by the ImageJ program. Molecular parameters were evaluated by qRT-PCR and Western blot. Results showed that increased infarct size in Non-Px groups decreased with RIPerC and melatonin. However, increased infarct size in Px groups was decreased minimally with RIPerC and significantly decreased with RIPerC + Melatonin. Fold change in Fas gene was associated with the infarct size. RIPerC and melatonin reduced expressions of Cybb, NfκB, and irisin genes. The physiological release and pharmacological concentration of melatonin may improve protective effect of RIPerC against I/R-induced infarct size by modulating Cybb, Fas, NfκB, Irisin signaling pathways.

Effect of melatonin on torsion and reperfusion induced pathogenesis of rat uterus

We investigated the use of melatonin to improve fertility and reduce uterine damage caused by torsion of the uterus in pregnant rats. We used 35 pregnant rats at gestational age 18 days. The animals were randomized into five groups. Group 1 was anesthetized only. Group 2 was subjected to experimental uterine torsion of 360° and the torsion was corrected after 6 h. Group 3 was subjected to uterine torsion of 360°, the torsion was corrected after 6 h and melatonin was administered at the time of correction. Group 4 rats were subjected to 360º uterine torsion and melatonin was administered 6 h later at the time of correction. Group 5 was administered melatonin followed by uterine torsion of 360 degrees followed by correction of torsion 6 h later. Samples were obtained from the uterine horns on the day 1 postpartum. We used Bax, Bcl-2 and caspase 3 staining to measure apoptosis in the uterine tissues. The mRNA levels of Rho-associated, coiled-coil containing protein kinases 1 (ROCK1), homeobox D10 (Hox4 HoxD10), TLR4, NFκB1, caveolin 1 (Cav1) heat shock protein 90 alpha (cytosolic), class B member 1 (Hsp90ab1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined using quantitative real-time polymerase chain reaction analysis (qRT-PCR). Bax, Bcl-2 and caspase 3 were detected using immunohistochemistry. No difference was observed among groups with respect to abortion, neonatal mortality or congenital abnormalities. Compared to the control group, the mRNA levels of Rock1, Hox4, TLR4, NFκB1, Cav1 and Hsp90 genes were decreased significantly in the study groups; the decrease was greater in groups 3 and 4, which were treated with melatonin. The greatest amount of Bax staining was found in group 1 and the least amount of Bcl-2 staining was found in groups 4 and 5; the greatest amount of caspase 3 staining was found in group 2. Our findings indicate that melatonin reduced uterine torsion related tissue damage and that its application during torsion was more effective than application following removal of torsion.

Effects of propolis, caffeic acid phenethyl ester, and pollen on renal injury in hypertensive rat: An experimental and theoretical approach

The objective of this study was to evaluate the antioxidant effects of propolis, caffeic acid phenethyl ester (CAPE; active compound in propolis), and pollen on biochemical oxidative stress biomarkers in rat kidney tissue inhibited by N^ω -nitro-L-arginine methyl ester (L-NAME). The biomarkers evaluated were paraoxonase (PON1), oxidative stress index (OSI), total antioxidant status (TAS), total oxidant status (TOS), asymmetric dimethylarginine (ADMA), and nuclear factor kappa B (NF-κB). TAS levels and PON1 activity were significantly decreased in kidney tissue samples in the L-NAME-treated group (P < 0.05). The levels of TAS and PONI were higher in the L-NAME plus propolis, CAPE, and pollen groups compared with the L-NAME-treated group. TOS, ADMA, and NF-κB levels were significantly increased in the kidney tissue samples of the L-NAME-treated group (P < 0.05). However, these parameters were significantly lower in the L-NAME plus propolis, CAPE, and pollen groups (P < 0.05) compared with rats administered L-NAME alone (P < 0.05). Furthermore, the binding energy of CAPE within catalytic domain of glutathione reductase (GR) enzyme as well as its inhibitory mechanism was determined using molecular modeling approaches. In conclusion, experimental and theoretical data suggested that oxidative alterations occurring in the kidney tissue of chronic hypertensive rats may be prevented via active compound of propolis, CAPE administration.

Effects of Chronic and Acute Zinc Supplementation on Myocardial Ischemia-Reperfusion Injury in Rats

The present study aims to explore the effects of chronic and acute zinc sulfate supplementation on myocardial ischemia-reperfusion injury in rats. The study registered 50 adult male rats which were divided into five groups in equal numbers as follows: group 1, normal control; group 2, sham; group 3, myocardial ischemia reperfusion (My/IR): the group which was fed on a normal diet and in which myocardial I/R was induced; group 4, myocardial ischemia reperfusion + chronic zinc: (5 mg/kg i.p. zinc sulfate for 15 days); and group 5, myocardial ischemia reperfusion + acute zinc: the group which was administered 15 mg/kg i.p. zinc sulfate an hour before the operation and in which myocardial I/R was induced. The collected blood and cardiac tissue samples were analyzed using spectrophotometric method to determine levels of MDA, as an indicator of tissue injury, and GSH, as an indicator of antioxidant activity. The highest plasma and heart tissue MDA levels were measured in group 3 (p < 0.05). Group 5 had lower MDA values than group 3, while group 4 had significantly lower MDA values than groups 3 and 5 (p < 0.05). The highest erythrocyte GSH values were found in group 4 (p < 0.05). Erythrocyte GSH values in group 5 were higher than those in group 3 (p < 0.05). The highest GSH values in heart tissue were measured in group 4 (p < 0.05). The results of the study reveal that the antioxidant activity inhibited by elevated oxidative stress in heart ischemia reperfusion in rats is restored partially by acute zinc administration and markedly by chronic zinc supplementation.

Effects of rosuvastatin on ADMA, rhokinase, NADPH oxidase, caveolin-1, hsp 90 and NFkB levels in a rat model of myocardial ischaemia-reperfusion

Aim

Endothelial dysfunction, oxidative stress and inflammation are among the most important mechanisms of ischaemia–reperfusion (I/R) injury. Besides their cholesterol-lowering effects, statins are known to provide protection against myocardial dysfunction and vascular endothelial injury via nitric oxide-dependent mechanisms. The aim of this study was to investigate the effects of rosuvastatin on certain intermediates involved in the generation of nitric oxide (asymmetrical dimethyl arginin, ADMA, caveolin-1 and hsp 90), oxidative stress (rhokinase, NADPH oxidase) and inflammation (NFkB), using an in vivo model of myocardial infarction in the rat.

Methods

Adult male Sprague Dawley rats were divided into three groups (control, I/R and I/R after 15 days of rosuvastatin administration). Reperfusion was applied for 120 min following left anterior descending coronary artery ischaemia for 30 min. Caveolin-1, hsp 90 and NFkB levels were evaluated with the quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and ADMA, rhokinase and NADPH oxidase levels were evaluated with ELISA.

Results

While NFkB and hsp 90 levels were higher in the I/R group, their levels were significantly lower in the rosuvastatin group. While ADMA and NADPH oxidase levels significantly increased with I/R, they were lower in the rosuvastatin-treated group, but not statistically significant. Rhokinase levels were significantly lower in the rosuvastatin group. Caveolin-1 levels were not different between the groups.

Conclusion

Our results suggest that ADMA, rhokinase, NADPH oxidase, hsp 90 and NFkB could facilitate I/R injury, and rosuvastatin significantly reduced levels of these parameters. These results indicate that rosuvastatin may have a protective role in I/R injury via mechanisms targeting inflammation, endothelial dysfunction and oxidative stress.

Effects of apocynin, an NADPH oxidase inhibitor, on levels of ADMA, MPO, iNOS and TLR4 induced by myocardial ischemia reperfusion

PURPOSE

In this study, the effects of apocynin, an NADPH oxidase inhibitor, on the levels of inducible nitric oxide synthase (iNOS) and the toll-like receptor 4 (TLR4), which are inflammatory mediators in myocardial ischemia-reperfusion (MIR) injury, and myeloperoxidase (MPO), which is the indicator of neutrophil infiltration and the endogenous nitric oxide synthase inhibitor asymmetric dimethyl arginine (ADMA) increasing with oxidative stress were investigated.

METHODS

MIR injury was accomplished by the application of occlusion for 30 minutes and reperfusion for 120 minutes in the left anterior descending artery (LAD). In the study, 21 Sprague-Dawley male rats were divided into three groups: a sham group (n = 7); a MIR group (n = 7); and a MIR + apocynin treatment group (n = 7, before the procedure, an intraperitoneal administration of 10 mg/kg of apocynin for 15 days). After reperfusion, iNOS, TLR4, MPO and ADMA levels in myocardial tissue were measured by ELISA.

RESULTS

While myocardial TLR4, MPO and ADMA levels increased in the MIR group, these parameters were found to be decreased significantly in the group treated with apocynin. Although iNOS levels showed an increase in the MIR group compared to the sham group and a reduction in the MIR+apocynin group, there was no statistically significant difference between the groups.

DISCUSSION

In our study, the effect of the treatment of apocynin in MIR on ADMA, MPO, iNOS and TLR4 levels in myocardial tissue was shown for the first time. It is thought that apocynin treatment may show a protective effect in MIR injury by affecting oxidative stress (ADMA) and inflammatory parameters (iNOS, MPO).

Lycopene and ellagic acid prevent testicular apoptosis induced by cisplatin

The aim of this study was to investigate the possible protective effects of lycopene (LC) and ellagic acid (EA) on cisplatin (CP)-induced testicular apoptosis in male rats. The control group was treated with placebo; LC, EA and CP groups were given alone LC, EA and CP, respectively; the CP+LC group was treated with a combination of CP and LC; and the CP+EA group was treated with a combination of CP and EA. Although CP significantly increased the number of Bax-positive (apoptotic) cells it had no effect on the number of Bcl-2-positive (antiapoptotic) cells compared with the control group. Administration of CP caused significant increase in lipid peroxidation and nonsignificant decrease in superoxide dismutase (SOD) activity along with some histopathological lesions in testicular tissue. However, combined treatments of LC or EA in addition to CP tended to prevent the CP-induced testicular apoptosis, histopathological lesions and lipid peroxidation.

Effect of lycopene on caspase-3 enzyme activation in liver of methanol-intoxicated rats: comparison with fomepizole

Lycopene is one of the major carotenoids and is found almost exclusively in tomatoes and tomato products. This study was performed to evaluate the effect of lycopene on methanol-induced liver injury and to compare the results with those after fomepizole, which is used in treatment of methanol intoxication. Experiments were carried out with 30 female Wistar rats weighting 180-200 g. Rats were injected with a intraperitoneally dose of 3 g/kg methanol as a 50% solution in isotonic saline once for intoxication. Rats were pretreated with fomepizole (50 mg/kg) and/or lycopene (10 mg/kg) before methanol. After 24 hours all the drug-treated and intoxicated rats were sacrificed under anesthesia. Malondialdehyde (MDA) levels were determined in order to assess lipid peroxidation, and caspase-3 activity was determined by immunostaining of liver tissues to evaluate apoptosis. Methanol administration significantly increased the MDA level and caspase-3 activity in liver. Pretreatment with lycopene and/or fomepizole decreased the MDA levels significantly. Similarly, lycopene and fomepizole decreased methanol-induced caspase-3 activity. The findings of the present study demonstrate that methanol intoxication causes hepatic toxicity in rats and that this is likely a result of reactive oxygen species and apoptosis induction. Lycopene has protective effects against methanol-induced hepatic injury similar to fomepizole. It was demonstrated for the first time that both lycopene and fomepizole prevent methanol-induced hepatic injury by reducing the increase of lipid oxidation and caspase-3 activation.

Lycopene, an antioxidant carotenoid, attenuates testicular injury caused by ischemia/reperfusion in rats

Testicular torsion is a common syndrome that could lead to infertility. We investigated the therapeutic effects of lycopene, an antioxidant caretenoid, on testicular ischemia/reperfusion (IR) injury that resembles testicular torsion. Male Wistar albino rats were divided into three groups: sham (n = 6), IR (n = 18), and ischemia/reperfusion with lycopene (IRL, n = 18). Left testicular artery and vein was occluded for 1 h, followed by reperfusion of 3 h, 24 h or 30 days in IR and IRL animals. Either corn oil (vehicle) or lycopene (4 mg/kg) was administrated once daily by gavage to IR or IRL animals, respectively, 5 min after ischemia. Sham-operated animals were treated with vehicle by gavage 5 min after the operation. IR decreased sperm motility and concentration in both ipsilateral and contralateral testes and increased abnormal sperm rate in ipsilateral testis after 30 days of reperfusion. Treatment with lycopene increased the motility in bilateral testes and decreased the rate of abnormal sperm in ipsilateral testis to the sham level, but did not increase sperm concentration in bilateral testes. IR increased the activities of catalase and glutathione peroxidase and the level of reduced glutathione by 24 h of reperfusion, but malondialdehyde remained unchanged. Lycopene treatment restored the enzyme activities but not the reduced glutathione level. Lycopene treatment also ameliorated the IR-induced tissue damage in bilateral testes. In conclusion, the therapeutic antioxidant effect of lycopene on germ cells could serve as a promising intervention to oxidative stress-associated infertility problems, such as testicular torsion.

Nitric oxide synthase inhibition in rats: Melatonin reduces blood pressure and ischemia/reperfusion-induced infarct size

Reduction in the synthesis or bioavailability of nitric oxide plays a significant role in the development of myocardial infarction and hypertension. Numerous studies suggest that melatonin reduces blood pressure (BP) and ischemia/reperfusion (I/R) injury in rats. The effects of melatonin on the BP and I/R-induced cardiac infarct size in L-NAME-induced hypertensive rats remains unknown. This study was designed to investigate the effects of melatonin on BP and the I/R-induced infarct size in chronic nitric oxide synthase inhibited rats by L-NAME. Rats received L-NAME for 15 days to produce hypertension and melatonin the last 5 days before I/R studies. To produce cardiac damage, the left coronary artery was occluded for 30 min, followed by 120 min reperfusion. L-NAME led to a significant increase in BP. Melatonin administration (10 mg/kg) to L-NAME treated rats significantly reduced BP and infarct size. Also, melatonin attenuated the mortality resulting from I/R, but this was not statistically significant. Melatonin administration would seem important to reduce BP and infarct size resulting from I/R in L-NAME-induced hypertensive rats.

Investigating the protective effect of melatonin on liver injury related to myocardial ischemia-reperfusion

BACKGROUND

An animal model of myocardial ischemia-reperfusion (MI/R) was used to test the hypothesis that free radicals released with MI/R have hazardous effects on liver through remote organ injury.

MATERIAL/METHODS

Twenty-one rats were divided into three groups: sham-treated, MI/R, and MI/R+melatonin. To produce MI/R, a branch of the left coronary artery was occluded for 30 min followed by two hours of reperfusion. Melatonin or vehicle was given 10 min before ischemia. At the end of the study, liver tissue was obtained for biochemical determination. The false discovery rate (FDR) is explained and was used for multiple comparisons of the groups' means.

RESULTS

Compared with the sham group, MI/R significantly decreased glutathione (GSH) content and increased levels of nitric oxide (NO) and malondialdehyde (MDA). Melatonin administration significantly increased GSH levels and decreased the levels of NO and MDA compared with the MI/R group.

CONCLUSIONS

Melatonin could prevent liver damage due to its strong antioxidant and free radical scavenger effects. Therefore, melatonin may have beneficial effects on remote organ injury such as MI/R-induced liver disorders.

Remote organ injury induced by myocardial ischemia and reperfusion on reproductive organs, and protective effect of melatonin in male rats

OBJECTIVE

Myocardial ischemia and reperfusion (MI-R) leads to remote organ injury associated with oxidative stress. Melatonin is a well-known antioxidant and free-radical scavenger. This study was conducted to examine whether MI-R causes damage in the testes and sperm quality, and to investigate the possible protective effect of exogenous melatonin on these parameters in an in vivo rat model.

DESIGN

Experimental study.

SETTING

Experimental Research Center, Firat University Medical School, Elaziğ, Turkey.

PATIENT(S)

Eight-week-old male Wistar rats (n = 18).

INTERVENTION(S)

To produce MI-R, a branch of the descending left coronary artery was occluded for 30 minutes, followed by 120-minute reperfusion. Melatonin (10 mg/kg) or vehicle was given 10 minutes before ischemia via the jugular vein.

MAIN OUTCOME MEASURE(S)

Reproductive organ weights and epididymal sperm concentration, sperm motility, abnormal sperm rate, and testicular-tissue malondialdehyde (MDA) and glutathione (GSH) levels were examined after reperfusion.

RESULT(S)

MI-R significantly decreased epididymal sperm motility, and increased the testes-tissue level of MDA, compared to the control group. Administration of melatonin reversed the harmful effects of MI-R significantly. However, MI-R did not change sperm concentration, GSH levels, and reproductive organ weights.

CONCLUSION(S)

These findings indicate that MI-R leads to damage of testis tissue and sperm motility, and melatonin protects against MI-R-induced reproductive-organ injury. These results may also encourage the use of antioxidants to reduce remote organ injury in the testis after MI-R.

Effects of caffeic acid phenethyl ester on cerebral cortex: structural changes resulting from middle cerebral artery ischemia reperfusion

Overproduction of free radicals is important in the pathogenesis of the cerebral damage induced by ischemia reperfusion. Caffeic acid phenethyl ester, an active component of propolis extract, exhibits antioxidant properties. The study was carried out in 16 male Wistar albino rats, divided into two groups: ischemia reperfusion and ischemia reperfusion with caffeic acid phenethyl ester. The middle cerebral artery was occluded for 60 min with an intraluminal suture, followed by 24-h reperfusion. In this study, widespread infarcted areas, red neurons (eosinophilic degeneration), pyknotic cells, vacuolization and neuroglial cell infiltration were observed in the cerebral cortex in the ischemia reperfusion group. In the caffeic acid phenethyl ester group, slightly infarcted areas were observed and neuroglial cell infiltration was not determined. Congestion of choroid plexus and pia mater was found more severe in the ischemia reperfusion group than in the caffeic acid phenethyl ester group. In the caffeic acid group, neuroglial cell activation was rare. Vacuolization, an indication of brain edema, was prevented by caffeic acid phenethyl ester. In the present study, we showed that pre-treatment with a single i.p. injection of caffeic acid phenethyl ester at 50 microM/kg dose reduced the structural changes.

Melatonin attenuates renal ischemia-reperfusion injury in nitric oxide synthase inhibited rats

Recent studies show that melatonin reduces the blood pressure (BP) and ischemia/reperfusion (I/R)-induced damage. This study was designed to investigate the effects of melatonin on the renal I/R injury in rats given the nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME). After right nephrectomy, I/R was induced by occlusion of the left renal vessels for 60 min, followed by 24h reperfusion. The administration of melatonin significantly attenuated BP in NOS-inhibited hypertensive rats. Malondialdehyde (MDA) levels, a stable metabolite of the free-radical-mediated lipid peroxidation cascade, were found to be significantly higher in the I/R group (3.48+/-0.2mg/l serum) than in the control group (2.69+/-0.2mg/l serum). L-NAME (40 mgkg(-1) for 15 days)+I/R significantly increased the MDA levels compared to I/R alone. Melatonin administration to L-NAME rats significantly reduced the MDA values resulting from I/R. We also demonstrated that I/R, and especially L-NAME+I/R, lead to structural changes in the kidney and that melatonin attenuates these changes. These results suggest that melatonin reduces BP and I/R injury in NOS inhibited rats by L-NAME.

Chemoprotective effect of melatonin against cisplatin-induced testicular toxicity in rats

In this study, we investigated the effect of melatonin on cisplatin-induced spermiotoxicity using quantitative, biochemical and histopathological approaches. Cisplatin (CP, 7 mg/kg) and melatonin (10 mg/kg) were intraperitoneally injected. The rats were decapitated on 5th (short-term group) or 50th day (long-term group) after CP injection. Traits of reproductive organs, sperm characteristics, testicular histological findings, and the lipid peroxidation in the testicular tissue were determined. Melatonin mitigated CP-induced reductions in testes, epididymis and accessory gland weights in rats decapitated on day 5. Both short- and long-term CP treatment decreased sperm concentration, sperm motility and increased abnormal sperm rates compared with the control. But the reduction of sperm concentration in long-term CP treatment was insignificant. Although treatment with melatonin provided moderately normalization with respect to sperm concentration in short-term treatment group, melatonin caused a marked normalization of sperm motility in both CP + melatonin groups. Both groups treated with the melatonin showed decreases in abnormal sperm rates compared with alone CP. While testicular malondialdehyde levels were elevated after CP treatment, glutathione peroxidase activity decreased significantly in both groups. Glutathione levels reduced after long-term treatment, but not in short-term group by CP administration. Treatment with CP plus melatonin provided significant amelioration of oxidative stress parameters. Histopathological findings of testes in both short- and long-term treatment groups paralleled the biochemical and spermatogenic results. This study clearly indicates that CP-treatment impaired markedly testicular function and combined treatment with melatonin prevented much of the toxicity in rats.

[Myocardial ischemia-reperfusion injury and melatonin]

It is believed that myocardial ischemia-reperfusion injury is related to increased free radical generated and intracellular calcium overload especially during the period of reperfusion. The pineal secretory product, melatonin, is known to be a potent free radical scavenger, antioxidant and can inhibit the intracellular calcium overload. In this review, we have summarized the fundamental of cardiac ischemia-reperfusion injury and the effects of melatonin on myocardial damage that related to cardiac ischemia-reperfusion injury. The total antioxidant capacity of human serum is related to melatonin levels. Incidence of sudden cardiac death is high in the morning hours. It has been shown that melatonin levels are significantly low at these times and patients with coronary heart disease have lower than normal individuals. These findings thought that melatonin would be valuable to test in clinical trials for prevention of possible ischemia-reperfusion-induced injury, especially life threatening arrhythmias and infarct size, effecting life quality, associated with thrombolysis, angioplasty, coronary artery spasm or coronary bypass surgery.

Effects of aminoguanidine against renal ischaemia-reperfusion injury in rats

Aminoguanidine is an inhibitor of nitric oxide synthase (NOS), with high selectivity for the inducible isoform (iNOS). In addition to being an inhibitor of NOS, aminoguanidine also exhibits antioxidant activity. Recent studies suggest that aminoguanidine reduces ischaemia-reperfusion (I/R)-induced damage. However, the role of aminoguanidine, in renal injury associated with I/R remains unknown. This study was designed to investigate the effects of aminoguanidine on renal I/R injury. There were three groups of eight rats each. I/R was induced by occlusion of the left renal vessels for 60 min, followed by 24 h reperfusion in rats. Malondialdehyde (MDA) levels, a stable metabolite of the free radical-mediated lipid peroxidation cascade, were found to be significantly higher in the I/R group (30.3 +/- 0.1 nmol g(-1) tissue) than in the control group (10 +/- 0.05 nmol g(-1)). Aminoguanidine (100 mg kg(-1)) administration to rats significantly reduced the MDA values. We also demonstrated that I/R leads to structural change but aminoguanidine did not reverse this change. Aminoguanidine, according to the biochemical finding is protective but histopathological findings did not reveal protection against I/R injury in kidney. The effects of aminoguanidine on I/R-induced damage remain a subject for future investigations.

Beneficial role of aminoguanidine on acute cardiomyopathy related to doxorubicin-treatment

Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic that has cardiotoxicity as a major side effect. One mechanism of this toxicity is believed to involve the reactive oxygen radical species (ROS); these agents likely account for the pathophysiology of DOX-induced cardiomyopathy. Aminoguanidine (AG) is an effective antioxidant and free radical scavenger which has long been known to protect against ROS formation. We investigated the effects of AG on DOX-induced changes in thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH) content. The rats were divided into four groups:1) Control; 2) DOX group; injected intraperitoneally (i.p.) with DOX 20 mg/kg in a single dose 3) AG-treated group; injected i.p. in single dose of 20 mg/kg DOX plus 100 mg/kg AG 1 h before the DOX for 3 days, 4) AG group; injected i.p. with AG 100 mg/kg for 3 days. DOX administration to control rats increased TBARS and decreased GSH levels. AG administration before DOX injection caused significant decrease in TBARS and increase in GSH levels in the heart tissue when compared with DOX only. Morphological changes, including severe myocardial fibrosis and inflammatory cell infiltration were clearly observed in the DOX-treated heart. AG reversed the DOX-induced heart damage. Therefore AG could protect the heart tissue against free radical injury. The application of AG during cancer chemotherapy may attenuate tissue damage and improve the therapeutic index of DOX.

Protective effect of lycopene on adriamycin-induced cardiotoxicity and nephrotoxicity

The aim of this study was to investigate the possible protective role of lycopene on adriamycin (ADR)-induced heart and kidney toxicity using biochemical and histopathological approaches. Rats were randomly divided into four groups. The first group received no medication and was regarded as the control group; the second group was injected with a single dose of ADR; the third group was treated with lycopene for 10 days before ADR injection and the last group was treated with lycopene for 2 days before and for 3 days after the administration of a single dose of ADR. ADR (10mg/kg) was intraperitoneally (i.p.) injected as a single dose and lycopene (4 mg/kg) was administered in corn oil by gavage. The levels of malondialdehyde (MDA) and reduced glutathione (GSH) in both the heart and kidneys were higher in the group treated with ADR alone than in the control group, and were lower in the groups administered with lycopene than in the ADR alone group. Although the activity of catalase (CAT) in the heart was higher in the ADR alone group than in the control group, it was lower in the kidneys. In particular, treatment with lycopene post-injection normalized both cardiac and kidney CAT activities. In heart and kidney tissues, glutathione peroxidase (GSH-Px) activities were not significantly different between all groups. Significant increases in the levels of plasma creatinine and urea were observed in the ADR group when compared to the control group, and these increases were normalized by lycopene treatment. Cardiac and renal histopathological changes were observed in the ADR group as compared to the control group. In contrast, these histopathological changes appeared nearly normal in the groups treated with lycopene pre- and post-injection. In conclusion, this study clearly indicated that ADR treatment markedly impaired cardiac and renal function and that treatment with lycopene might prevent this toxicity in rats.

Caffeic acid phenethyl ester (CAPE) attenuates cerebral vasospasm after experimental subarachnoidal haemorrhage by increasing brain nitric oxide levels

BACKGROUND

Cerebral vasospasm, a medical complication of aneurysmal subarachnoid hemorrhage (SAH), is associated with high morbidity and mortality rates, even after the aneurysm has been secured surgically or endovascularly. Evidence accumulated during the last decade suggest that scavenging a vasodilator, nitric oxide (NO), by superoxide anions (O(2)(-)), and activating a strong vasoconstructor, protein kinase C (PKC), are the two most important mechanisms in the pathogenesis of vasospasm. Our aim in this study was to determine whether caffeic acid phenethyl ester (CAPE), a non-toxic oxygen free radical scavenger, prevents vasospasm in an experimental rat model of SAH.

METHODS

Twenty eight rats (225-250 g) were divided into four groups equally: group 1, control group; group 2, SAH group; group 3, SAH plus placebo group; and group 4, SAH plus CAPE group. We used double haemorrhage method for SAH groups. Starting 6h after SAH, 10 micromol/kg CAPE or an equal volume of 0.9% saline were administered by intraperitoneal injection twice daily for 5 days to SAH plus CAPE and SAH plus placebo groups, respectively. CAPE or 0.9% saline injections were continued up to 5th day after SAH. Rats were sacrificed on the 5th day. Brain sections at the level of the pons were examined by light microscopy. Measurements were made for the cross-sectional areas of the lumen and the vessel wall (intimae plus media) of basilar artery by a micrometer. The levels of malondialdehyde (MDA), reduced glutathione (GSH), and nitric oxide (NO) were measured in rat brain tissue.

RESULTS

Administration of CAPE significantly attenuated the vasoconstriction of the basilar artery. There were marked narrowing in the lumens of and thickening in the walls of basilar arteries in the SAH, and the SAH plus placebo compared with CAPE group (p < 0.001). We also observed that CAPE administration significantly decreased the tissue level of MDA, while significantly increased the tissue levels of GSH, NO in the SAH plus CAPE group compared to only SAH group, p < 0.05.

CONCLUSIONS

Our results indicate that CAPE is effective in attenuating delayed cerebral vasoconstriction following experimental SAH. Our findings also suggest that the elevation of lipid peroxidation and reduction of NO bioavailability, resulting from the generation and the interaction of free radicals, have a significant role in the pathogenesis of vasospasm after SAH.

Vascular Reactivity to Various Vasoconstrictor Agents and Endothelium-Dependent Relaxations of Rat Thoracic Aorta in the Long-Term Period of Pinealectomy

In this study, the effects of reduced melatonin concentrations in the long-term period of pinealectomy on mean arterial blood pressure (BP) and vascular responses in isolated rat thoracic aorta were investigated. Rats were pinealectomized (Px) two months before the beginning of the studies. Rings of endothelium-intact and -denuded rat arteries were mounted in isolated tissue baths for the measurements of isometric contractile force. No significant difference was determined between the arterial BP of Px (88.1 +/- 1.9 mmHg) and control (83.8 +/- 1.2 mmHg) rats. All arteries isolated from control and Px rats showed essentially identical contractions in response to phenylephrine, serotonin, calcium, clonidine, vasopressin, and angiotensin-II. Only endothelin-1 (ET-1)-induced contractions in the endothelium-denuded vessels isolated from Px rats were found to be increased to some extent. Pinealectomy did not affect acetylcholine or sodium nitroprusside-induced relaxation in the rat aorta either. These data suggest that reduced melatonin levels two months after pinealectomy did not modify either the vascular reactivity to various vasoconstrictor agents except the partially increased contractile responses to ET-1 in the endothelium-denuded thoracic aortas of Px rats or the endothelium-dependent and -independent relaxations in rat thoracic aorta. Restoration of the increased vascular responses to some vasoconstrictor agents, which were reported previously, may be the reason of why the hypertension is temporary following pinealectomy.

Protective effect of caffeic acid phenethyl ester (CAPE) on myocardial ischemia-reperfusion-induced apoptotic cell death

Occlusion of coronary artery causes cardiomyocyte dysfunction. Reperfusion relieves ischemia by providing cells with metabolites and oxygen, thereby preventing extensive tissue damage. Although reperfusion salvages the myocardium, it also initiates a series of events including myocardial apoptosis and necrosis. The common inducers of apoptosis include reactive oxygen species (ROS). Caffeic acid phenethyl ester (CAPE) is known as an antioxidative, anti-inflammatory effects, may protect myocardial ischemia-reperfusion (MI/R)-induced apoptosis. We have previously reported that CAPE reduced MI/R-induced necrosis. Therefore, this study was focused to investigate protective effect of CAPE on the distinct form of cell death; apoptosis in an in vivo rat model. To produce MI/R, a branch of the descending left coronary artery was occluded for 30 min followed by 2 h reperfusion. ECG changes, blood pressure (BP), and heart rate (HR) were measured before occlusion and continued both occlusion and reperfusion. CAPE (50 micromol/kg) was given 10 min before ischemia via jugular vein. Extensive formation of DNA strand breaks, the typical biochemical feature of apoptosis, was detected with the use of the terminal deoxynucleotidyl transferase (TdT)-mediated d UTP-biotin nick and labeling (TUNEL) method. Also, cysteine aspartate specific proteinase (caspase)-3 and caspase-9 activities a universal effector of apoptosis, were determined. Trunk blood was extracted to determine the serum contents related to oxidant-antioxidant status. In hemodynamic parameters, there was no significant difference in HR or BP values among any group. CAPE administration had no a significant effect on hemodynamic parameters during ischemia or reperfusion. Control group revealed extensive TUNEL-positive cardiomyocytes especially in free wall of left ventricule, interventiculare septum and nearly apex zone. Intensity of TUNEL-positive cardiomyocytes reduced as a result of CAPE treatment compared to control group in the same sections. Result of the caspase activities was found to correlate with TUNEL evaluation. CAPE also, ameliorated antioxidant status. We propose that CAPE acts in the heart as a potent scavenger of free radicals to prevent the apoptotic effect of I/R. Further studies are needed to elucidate the mechanisms of apoptotic death machinery.

Protective effects of melatonin on myocardial ischemia-reperfusion induced infarct size and oxidative changes

Free radicals, calcium overloading and loss of membrane phospholipids play an important role in the development of ischemia/reperfusion (I/R) injury. Melatonin is a well-known antioxidant and free radical scavenger. Melatonin may also reduce the intracellular calcium overloading and inhibit lipid peroxidation. This study was designed to investigate the effects of melatonin on the I/R-induced cardiac infarct size in an in vivo rat model. We also investigated glutathione (GSH) levels, an antioxidant the levels of which are influenced by oxidative stress, and malondialdehyde (MDA) levels, which is an index of lipid peroxidation. To produce cardiac damage, the left main coronary artery was occluded for 30 min, followed by 120 min reperfusion, in anesthetized rats. Melatonin (10 mg/kg) or vehicle was given 10 min before ischemia via the jugular vein. Infarct size, expressed as the percentage of the risk zone, was found significantly greater in I/R group than in the melatonin-treated I/R group. MDA levels were significantly higher, but GSH levels were lower in the I/R group than in the control group. Melatonin significantly reduced the MDA values and increased the GSH levels. These results suggest that oxidative stress contributes to myocardial I/R injury and melatonin administration exerts a mitigating effect on infarct size. Furthermore, the results indicated that melatonin improves the antioxidant capacity of the heart and attenuates the degree of lipid peroxidation after I/R.

Protective effects of melatonin on myocardial ischemia/reperfusion induced infarct size and oxidative changes

Free radicals, calcium overloading and loss of membrane phospholipids play an important role in the development of ischemia/reperfusion (I/R) injury. Melatonin is a well-known antioxidant and free radical scavenger. Melatonin may also reduce the intracellular calcium overloading and inhibit lipid peroxidation. This study was designed to investigate the effects of melatonin on the I/R-induced cardiac infarct size in an in vivo rat model. We also investigated glutathione (GSH) levels, an antioxidant the levels of which are influenced by oxidative stress, and malondialdehyde (MDA) levels, which is an index of lipid peroxidation. To produce cardiac damage, the left main coronary artery was occluded for 30 min, followed by 120 min reperfusion, in anesthetized rats. Melatonin (10 mg/kg) or vehicle was given 10 min before ischemia via the jugular vein. Infarct size, expressed as the percentage of the risk zone, was found significantly greater in I/R group than in the melatonin-treated I/R group. MDA levels were significantly higher, but GSH levels were lower in the I/R group than in the control group. Melatonin significantly reduced the MDA values and increased the GSH levels. These results suggest that oxidative stress contributes to myocardial I/R injury and melatonin administration exerts a mitigating effect on infarct size. Furthermore, the results indicated that melatonin improves the antioxidant capacity of the heart and attenuates the degree of lipid peroxidation after I/R.

Efficacy of melatonin as protectant against oxidative stress and structural changes in liver tissue in pinealectomized rats

Previous observations demonstrated that physiological levels of melatonin, the pineal secretory product, are important in protecting against oxidative stress-induced tissue damage. We investigated the effects of pinealectomy and administration of exogenous melatonin on liver tissue in rats. Pinealectomized (Px) and sham-operated (non-Px) rats were used. We evaluated structural changes, reduced glutathione (GSH) levels and malondialdehyde (MDA) levels. Rats were divided into three groups (10 rats in each group): control (non-Px), Px+vehicle and Px+melatonin (4 mg/kg given daily intraperitoneally for 10 days). Liver GSH levels were significantly lower in Px rats than in the control group. Melatonin administration significantly increased GSH levels (p < 0.05). Px caused a significant increase in MDA levels as compared with the control group and melatonin administration to Px rats significantly reduced MDA levels in the liver (p < 0.05). Sinusoidal dilatation to a varying degree developed in all Px rats. Severity of mononuclear cell infiltration and sinusoidal congestion were lower in Px+melatonin group than in the Px group. These findings suggest that a significant increase in oxidative and structural changes occur in rat livers after pinealectomy, which can be diminished by melatonin treatment.

Melatonin protects against myocardial doxorubicin toxicity in rats: role of physiological concentrations

Doxorubicin (Dox) is a widely used antineoplastic drug. Oxygen radical-induced injury of membrane lipids is considered to be the most important factor responsible for the development of Dox-induced cardiotoxicity. The pineal secretory product, melatonin, is known to be a potent free radical scavenger and its pharmacological concentrations have been shown to reduce Dox-induced cardiac damage. However, the physiological role of melatonin in the prevention of this damage is unknown. We investigated physiological and pharmacological effects of melatonin on Dox-induced changes in the levels of malondialdehyde (MDA), a lipid peroxidation product, and morphological changes in heart. Rats were pinealectomized (Px) or sham-operated (control) 2 months before the studies. Melatonin was administered [4 mg/kg, intraperitoneally (i.p.)] 1 hr before or 24 hr after the administration of a single dose of Dox (20 mg/kg, i.p.) and continued for 2 days. The levels of MDA Dox was found to be significantly higher in the Px rats (55.9 +/- 0.6 nmol/g tissue) than intact control animals (42.6 +/- 0.4). Dox administration to Px and non-Px rats significantly increased the MDA levels. Pre- and post-treatment with melatonin in both Px and intact rats significantly reduced MDA levels. Morphological changes parallelled the MDA alterations. These findings strongly suggest that both physiological and pharmacological concentrations of melatonin are important in protecting the heart from Dox-induced damage in rats. It would seem valuable to test melatonin in clinical trials for prevention of possible heart damage associated with Dox.

Amikacin-induced acute renal injury in rats: protective role of melatonin

It is well established that some agents such as aminoglycosides generate free oxygen radicals, leading to an increased oxireductase production, which in turn increases tissue toxicity. The aim of this study is to test whether melatonin, the chief secretory product of the pineal gland and a highly effective antioxidant and free radical scavenger, reduces the nephrotoxicity caused by amikacin (AK). Herein, we investigated the physiologic and pharmacological role of melatonin in influencing AK-induced nephrotoxicity. For this, pinealectomized (Px) and sham operated (non-Px) rats were used. Both AK and melatonin were administered to all groups. We investigated the effects of melatonin on AK-induced changes in levels of malondialdehyde (MDA), a lipid peroxidation product, glutathione (GSH), an antioxidant whose levels are influenced by oxidative stress, and blood urea nitrogen (BUN) and serum creatine (Cr) levels. Morphologic changes in the kidney were also examined by using light microscopy. MDA levels were found to be higher in Px than in non-Px AK-treated animals. Melatonin administration to Px rats reduced MDA levels. In relative to non-Px rats, Px animals treated with AK had significantly lower GSH concentrations while melatonin administration elevated GSH levels in the kidney; however, this stimulatory effect of melatonin was not observed in non-Px AK-treated rats. Treatment with AK alone resulted in significantly higher plasma Cr and BUN levels. Repeated administration of melatonin prevented the AK-induced elevation of plasma Cr and BUN levels. Morphologic damage to renal tubules as a result of AK was more severe in the renal cortex than in the medulla. The damage to the kidney induced by AK was reversed by melatonin in the Px rats. In conclusion, these results show that physiologic melatonin concentrations are important in reducing AK-induced renal damage, while pharmacologic concentrations of melatonin did not add to the beneficial effect.

The attenuation of vasospasm by using a sod mimetic after experimental subarachnoidal haemorrhage in rats

BACKGROUND

Delayed cerebral vasoconstriction and brain ischemia, are critical problems in the management of a patient affected by rupture of an intracranial aneurysm. Overexpression of Cu-Zn superoxide dismutase (Cu-Zn SOD) can reduce the extent of cerebral vasospasm. We, therefore investigated if vasospasm, can be prevented by a novel, stable, and cell permeable SOD mimetic, MnTBAP [Mn(III) tetrakis (4-benzoic acid) porphyrin] which permeates the biological membranes and scavenges superoxide anions and peroxynitrite.

METHODS

28 rats (225-250 g) were divided equally into four groups: group 1: control; group 2: SAH only; group 3: SAH plus placebo; and group 4: SAH plus MnTBAP. We used a double haemorrhage method to produce SAH. Starting six hours after SAH, 5 mg/kg MnTBAP (Calbiochem, Darmstadt-Germany; Cat. No 475870)) or an equal volume of 0.9% saline (37 degrees C) was administered by intraperitoneal injection twice daily for 5 days to groups 4 and 3 respectively. MnTBAP or 0.9% saline injections were continued up to fifth day after SAH and rats were sacrificed on the fifth day. Brain sections at the level of the pons were examined by light microscopy. Planimetric measurements were made for the cross-sectional areas of the lumen and the vessel wall (intima plus media) of the basilar artery by a micrometer.

FINDING

Administration of MnTBAP significantly attenuated the vasoconstriction of the basilar artery in group 4 compared with the groups 2 and 3 (p<0.001).

INTERPRETATION

These results suggest that this SOD mimetic (MnTBAP) attenuates delayed cerebral vasoconstriction following experimental SAH and that superoxide anions have a role in the pathogenesis of vasospasm after SAH.

The protective effects of physiological and pharmacological concentrations of melatonin on renal ischemia-reperfusion injury in rats

Reactive oxygen species have been implicated in the pathophysiology of renal ischemia reperfusion (I/R) injury. The pineal secretory product melatonin is known to be a potent free radical scavenger and antioxidant. This study was designed to investigate the effects of physiological and pharmacological concentrations of melatonin on I/R injury. Rats were pinealectomized (Px) or sham-operated (control) 2 months before the I/R studies. There were eight groups of eight rats each. After a right nephrectomy to produce damage, left renal vessels were occluded for 60 min, followed by 24 h reperfusion, in rats. Malondialdehyde (MDA) levels resulting from I/R were significantly higher in the pinealectomized rats than in the control group. Melatonin administration (4 mg kg(-1) i.p. either before ischemia or reperfusion) to Px and sham-operated rats significantly reduced the MDA values and returned them to the control values. Morphological changes in the groups were similar to the MDA levels. Serum levels of blood urea nitrogen and creatine were unchanged. These results suggest that physiological and pharmacological melatonin concentrations are important for the reduction of I/R-induced damage. We also demonstrated that melatonin, even when administrated just before reperfusion, had a protective effect on I/R injury. It would seem valuable to test melatonin in clinical trials for the prevention of possible I/R injury.

The beneficial effect of melatonin on chronic cyclosporin A nephrotoxicity in rats

Cyclosporin A (CsA)-induced nephrotoxicity may be the consequence of oxidative stress. Anti-oxidant agents could be useful in reducing CsA toxicity. In this light microscopy study, tubular dilatation, atrophy, vacuolization and tubulointerstitial fibrosis were observed in rats given CsA, whereas in rats given CsA plus melatonin, no histological changes occurred. It is concluded that melatonin could be useful for reducing the nephrotoxic effects of CsA.

Myocardial ischemia-reperfusion in rats: reduction of infarct size by either supplemental physiological or pharmacological doses of melatonin

Myocardial ischemia-reperfusion (I/R) represents a clinically relevant problem associated with thrombolysis, angioplasty and coronary bypass surgery. I/R injury is believed to be a consequence of free radical generation in the heart especially during the period of reperfusion. The pineal secretory product, melatonin, is known to be a potent free radical scavenger and pharmacological concentrations have been shown to reduce the I/R-induced cardiac damage in isolated rat hearts. However, the physiological role of melatonin in the prevention of this damage is unknown. Rats were pinealectomized or sham-operated (control) 2 months before the I/R studies. To produce cardiac damage, the left main coronary artery was occluded for 30 min, followed by 120 min reperfusion, in anesthetized rats. Infarct size, expressed as the percentage of the risk zone, was found significantly higher in pinealectomized rats (49+/-3.4%) than in the control group (34+/-3.6%). Melatonin administration (4 mg/kg, either before ischemia or reperfusion) to pinealectomized rats significantly reduced the infarct size values and returned them to the control values. On the other hand, melatonin administration (4 mg/kg) to sham-operated rats failed to attenuate significantly the I/R-induced infarct size. These results suggest that physiological melatonin concentrations are important in reducing the I/R-induced myocyte damage, while pharmacological concentrations of melatonin did not add to the beneficial effect. As melatonin levels have been reported to decrease with age, melatonin replacement therapy may attenuate I/R-induced myocardial injury, especially in older patients.

Physiological and pharmacological concentrations of melatonin protect against cisplatin-induced acute renal injury

Cisplatin [cis-diaminedichloroplatinum(II), CDDP] is a widely used antineoplastic drug. However, it has major side-effects such as acute tubular necrosis (ATN). There are a number of studies concerning the role of reactive oxygen radical species in the pathophysiology of CDDP-dependent ATN. Several antioxidant agents have been reported to prevent this side-effect but there is no study regarding the protective action of either physiological or pharmacological concentrations of melatonin. Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger and indirect antioxidant. We investigated the effects of melatonin on CDDP-induced changes of renal malondialdehyde (MDA), a lipid peroxidation product, and blood urea nitrogen (BUN) and serum creatine (Cr). The morphological changes in kidney were also examined using light microscopy. The rats were divided into two groups: pinealectomized (Px) and sham-operated (non-Px). Both CDDP and melatonin were administered to all groups. MDA levels were found to be higher in Px than non-Px animals. CDDP administration to Px or non-Px rats increased renal MDA levels and melatonin administration either before or after CDDP injection caused significant decreases in MDA in kidney compared with those in rats treated with CDDP alone. Serum levels of BUN and Cr did not change as a result of any treatment. Morphological tubule damage because of CDDP was more severe in the renal cortex than in the medulla. The damage to the kidney induced by CDDP was reversed by melatonin. The results show that pharmacological and physiological concentrations of melatonin reduce CDDP-induced renal injury.

Effects of physiological and pharmacological concentrations of melatonin on ischemia-reperfusion arrhythmias in rats: can the incidence of sudden cardiac death be reduced?

Cardiac arrhythmias during ischemia-reperfusion (I/R) are believed to be related to free radicals generated in the heart especially during the period of reperfusion. The pineal secretory product, melatonin, is known to be a potent free radical scavenger and its pharmacological concentrations have been shown to reduce the I/R-induced arrhythmias in isolated rat hearts. However, the physiological role of melatonin in the prevention of these arrhythmias is unknown. Rats were pinealectomized (Px) or sham-operated (non-Px) (control) 2 months before the I/R studies. To produce arrhythmias, left main coronary artery was occluded for 7 min, followed by 7 min reperfusion, in anesthetized rats. The incidence of mortality resulted from irreversible ventricular fibrillation (VF) was found significantly higher in the Px rats (63%) than in the control group (25%). Melatonin administration (0.4 mg/kg, either before ischemia or reperfusion) to Px rats significantly reduced the incidence of total (irreversible plus reversible) and irreversible VF and returned them to control values. On the other hand, melatonin administration (0.4 and 4 mg/kg) to non-Px rats failed to attenuate the I/R arrhythmias, significantly. These results suggest that physiological melatonin concentrations are important to reduce the I/R-induced VF and mortality, while pharmacological concentrations of melatonin did not increase its beneficial effect on these arrhythmias. As melatonin levels have been reported to decrease with age, melatonin replacement therapy may attenuate the incidence of sudden cardiac death especially in older patients.

Effects of captopril and losartan on myocardial ischemia-reperfusion induced arrhythmias and necrosis in rats

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 (AT (1)) receptor blockers improve ischemia-reperfusion induced arrhythmias and infarct size in several animal models. However, the effects of pretreatment with ACEIs or AT (1) receptor blockers on acute myocardial infarct size and arrhythmias are controversial. Thus, we sought to assess the comparative effects of pretreatment with ACEI captopril and AT (1)-receptor blocker losartan on myocardial infarct size and arrhythmias in a rat model of ischemia-reperfusion. We randomly assigned 92 male Wistar rats for arrhythmias ( n= 60) and necrosis ( n= 32) experiments. To produce arrhythmia, the left main coronary artery was occluded for 7 min, followed by 7 min of reperfusion and to produce necrosis, the the left main coronary artery was occluded for 30 min, followed by 120 min of reperfusion. Captopril (3 mg kg (-1)) and losartan (0.2 and 2 mg kg (-1)) were given intravenously 10 min before occlusion. Captopril reduced the incidences of ventricular fibrillation (VF) and mortality associated with irreversible VF, whereas the studied doses of losartan did not. Captopril also decreased the number of ventricular beats on reperfusion. Losartan 2 mg kg (-1) reduced both the number of ventricular premature beats and the incidence of ventricular tachycardia (VT) on reperfusion, while losartan at dose of 0.2 mg kg (-1) had no effect on these arrhythmias. Compared to the control group, both captopril and losartan reduced myocardial infarct size in the rat model of ischemia-reperfusion, but this was statistically significant for captopril only. In this experimental model, although captopril did not reduce the incidence of reperfusion-induced VT, it was more effective than the AT (1)-receptor blocker losartan at preventing mortality associated with irreversible VF and to reduce myocardial infarct size in rat model of ischemia-reperfusion.

Effects of chronic ethanol consumption on alpha-adrenergic-induced contractions and endothelium-dependent relaxations in rat thoracic aorta

The effects of chronic oral administration of ethanol (7.2% daily during 24 weeks) on the contractions induced by phenylephrine (Phe) and the endothelium-dependent relaxation responses to acetylcholine (ACh) were studied in rat thoracic aorta. Ethanol pretreatment significantly attenuated the contractile responses to Phe, resulting in parallel shift of the concentration-response curve to the right. EC(50)values of Phe were 64.6+/-11.2 and 95.5+/-8.5 nmol l(-1)in control and ethanol-fed rats, respectively. On the other hand, either calcium-induced contractions or relaxation responses to ACh and sodium nitroprusside were similar in the vessels of the control and ethanol-treated rats. These results suggest that chronic ethanol ingestion significantly attenuates the alpha(1)-adrenergic-induced contractions but does not affect the relaxation responses mediated by nitric oxide in rat aortic rings.

Melatonin administration prevents the nephrotoxicity induced by gentamicin

OBJECTIVE

To investigate the effect of melatonin on the antioxidant enzyme activity and renal tubular necrosis induced by gentamicin.

MATERIALS AND METHODS

Twenty-four adult male Sprague-Dawley rats were divided into three equal groups. In group 1, the rats were injected with vehicle (controls), in group 2 they were injected with gentamicin for 5 days and in group 3 injected with gentamicin plus melatonin for 5 days. At 24 h after the last injection, rats were killed and the renal cortex separated from the medulla. Most of the cortex was homogenized but a small sample was fixed in formaldehyde solution for histological examination by light microscopy. Blood samples were also taken to assess the serum levels of urea, creatinine, Na+, K+ and gamma-glutamyl transpeptidase (gamma-GT); before death, urine samples were analysed for protein content. Crude extracts of the cortex were used to determine lipoperoxides, reduced glutathione (GSH-Px), catalase and superoxide dismutase (SOD). The results were compared using the Mann-Whitney U-test.

RESULTS

Compared with the controls rats, gentamicin caused hyperproteinuria, an increase in the level of gamma-GT in serum, a marked increase in lipoperoxides and a significant decrease of GSH-Px, catalase and SOD activity in the kidney. In the rats in group 3 there was a marked restoration in lipid peroxidation, GSH-Px, catalase, SOD activity and proteinuria, and in gamma-GT in serum. In rats in group 2 there was widespread tubular necrosis (grade 2-4) but in rats in group 3 there was a marked reduction in the extent of tubular damage. There was no significant difference in serum levels of Na+, K+, blood urea nitrogen and creatinine.

CONCLUSION

These results indicate that melatonin prevents the tubular necrosis induced by gentamicin in rats, presumably because it is a potent antioxidant and restores antioxidant enzyme activity in the rat kidney.