Hakan Parlakpinar

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

Abstract: 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.

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

Abstract: 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.

Protective Effect of Β-Carotene on Methotrexate-Induced Oxidative Liver Damage

In this study, the authors aimed to investigate the role of oxidative stress on the hepatic damage caused by methotrexate (MTX) and the possible protective effects of β-carotene against this damage. The rats were divided into four groups as control, MTX (20 mg/kg ip), β-carotene (10 mg/kg/day ip) + MTX, and β-carotene. Histopathologic alterations were evaluated for defining the liver damage. The tissue, malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GP-x) contents and serum aspartate aminotransferase (AST) and alanine aminotranferase (ALT) activities were also examined. Histopathologic damage for each group score findings have been determined as control: 0.66 ± 0.33; MTX: 7.0 ± 0.68; β-carotene + MTX: 3.3 ± 0.42; and β-carotene: 0.5 ± 0.3. In the MTX-treated group, MDA, AST, and ALT values were increased, while SOD and GP-x values were decreased compared with the control group. In the β-carotene + MTX-treated group, AST and ALT values significantly decreased, while all other parameters were similar to the control group. This study shows that β-carotene has a protective effect on MTX-induced oxidative hepatic damage. Consequently, it seems that an antioxidant agents like β-carotene may be useful in decreasing the side effects of chemotherapy.

Protective effect of melatonin on random pattern skin flap necrosis in pinealectomized rat

Abstract: Random pattern skin flaps are still widely used in plastic surgery. However, necrosis in the distal portion resulting from ischemia is a serious problem, increasing the cost of treatment and hospitalization. Free oxygen radicals and increased neutrophil accumulation play an important role in tissue injury and may lead to partial or complete flap necrosis. To enhance skin flap viability, a variety of pharmacological agents have been intensively investigated. The aim of this study is to test the effects of melatonin, the chief secretory product of the pineal gland and a highly effective antioxidant, on random pattern skin flap survival in rats. Herein, to investigate the physiological and pharmacological role of melatonin on dorsal skin flap survival. Pharmacological (0.4, 4 and 40 mg/kg) levels of melatonin were given intraperitoneally (i.p.). For this, pinealectomized (Px) and sham operated (non‐Px) rats were used. The effects of melatonin on levels of malondialdehyde (MDA), nitric oxide (NO), glutathione (GSH) and the activities of glutathione peroxidase (GSH‐Px) and superoxide dismutase (SOD) were measured in the skin flap. The ratio of skin flap necrosis was compared among the experimental groups by using planimetry. MDA and NO levels were found to be higher in Px than non‐Px rats; while GSH levels and GSH‐Px, and SOD activities were reduced. Melatonin administration to Px rats reduced MDA and NO levels and increased GSH, GSH‐Px, SOD levels. Melatonin also reduced the ratio of flap necrosis determined by using planimetry and supported through the photography. In conclusion, these results show that both physiological and pharmacological concentrations of melatonin improve skin flap viability.

Potent therapeutic effect of melatonin on aging skin in pinealectomized rats.

Abstract:  It is generally agreed that one of the major contributors to skin aging is reactive oxygen species. As organisms reach advanced age, free radical generation increases and the activity of tissue antioxidant enzyme system decreases. Melatonin is an antioxidant and free radical scavenger. The present study was first aimed to determine the morphometric and biochemical changes caused by long‐term pinealectomy in order to investigate the role of melatonin as skin architecture. Secondly, the effect of exogenous melatonin administration on these changes was determined. Rats were pinealectomized or sham operated (control) for 6 months. Half of the pinealectomized rats were treated with 4 mg/kg melatonin during the last month of the experiment. Pinealectomy resulted in important morphometric and biochemical changes in the back, abdominal and thoracic skin. The thickness of epidermis and dermis and the number of dermal papillae and hair follicles were reduced. Melatonin administration to pinealectomized rats significantly improved these alterations in all body areas (P < 0.005). On the contrary, in pinealectomized rats the levels of antioxidant enzymes, catalase and glutathione peroxidase were decreased. Melatonin restored the levels of these enzymes. The pinealectomy‐induced increases in lipid peroxidation in the abdominal and thoracic skin were significantly reduced by melatonin treatment (P < 0.005 and 0.01 respectively). These results suggest that melatonin is highly efficient anti‐aging factor and, as melatonin levels decrease with age, melatonin treatment may reduce age‐related skin changes.

The protective effect of melatonin on ischemia–reperfusion injury in the groin (inferior epigastric) flap model in rats

Abstract:  Inadequate blood perfusion and ischemia–reperfusion (I/R) injury in the surgical skin flap are believed to be the major factors that cause harmful changes within the tissue and vasculature, resulting in flap necrosis. Reactive oxygen radical species (ROS), in part, are believed to play an important role in this injury. Melatonin, in many physiological conditions, has been shown to have direct and indirect antioxidative effects and free‐radical‐scavenging properties. Therefore, it may have a beneficial effect on I/R‐induced flap injury. In this study, the possible protective effects of melatonin were investigated in I/R injury of rat epigastric (axial pattern) flaps. Ischemia was achieved for 12 h by occlusion of inferior epigastric artery. Melatonin or vehicle was administered 1 h before flap elevation and was continued for 6 days after ischemia. I/R injury elevated malondialdehyde (MDA), an end product of lipid peroxidation, and nitric oxide (NO) levels while the glutathione (GSH) content was reduced. Myeloperoxidase (MPO) activity, which is known to be related to tissue neutrophil accumulation, was found to be statistically higher in the I/R group when compared with the sham group. Administration of melatonin significantly decreased MDA, NO and MPO levels and elevated the GSH content. Moreover, melatonin reduced the flap necrosis area, which was determined using a planimetric method. In conclusion, melatonin, a potent scavenger of free radicals, plays a major role in preventing the inferior epigastric arterial I/R‐induced flap necrosis, based on planimetric flap survival and biochemical results. The beneficial effects of melatonin in I/R injury implies the involvement of free radicals in flap damage.

Myocardial ischemia/reperfusion-induced oxidative renal damage in rats: protection by caffeic acid phenethyl ester (CAPE).

Myocardial ischemia-reperfusion (MI/R) may induce renal damage. A rat model of M/IR injury was established. The left coronary artery was clamped for 30 min, constituting the ischemic period, and was then released for 120 min, thus constituting the reperfusion period. The purpose of this study was to evaluate the effects of caffeic acid phenethyl ester (CAPE), an antioxidant, on renal dysfunction in rats undergoing MI/R. CAPE (50 μmol/kg) was administered by infusion 10 min before ischemia and during occlusion. Hemodynamic changes were recorded during the different periods. At the end of the reperfusion period, rats were sacrificed, and the kidneys were quickly removed for biochemical determination and histopathological analysis. MI/R was accompanied by a significant increase in malondialdehyde (MDA) production and decrease in glutathione (GSH) content in the rat kidney. Administration of CAPE reduced MDA production and prevented depletion of GSH content. These beneficial changes in these biochemical parameters were also associated with parallel changes in histopathological appearance. These findings imply that MI/R plays a causal role in kidney injury through overproduction of oxygen radicals or insufficient antioxidant, and CAPE exerts renal-protective effects probably by its radical scavenging and antioxidant activities.

The Protective Effects of Apocynin on Kidney Damage Caused by Renal Ischemia/Reperfusion

PURPOSE This experimental study was designed to explore the protective effect of apocynin, the NADPH-oxidase inhibitor, on kidney damage induced by ischemia/reperfusion (I/R) in a rat model. METHODS Thirty-two rats were randomly divided into a control group and three I/R groups (1-hour ischemia followed by 23-hour reperfusion). Three I/R groups were treated by apocynin (20 mg/kg, i.p.) at two different time points (before ischemia and during ischemia). The histopathological findings, including apoptotic changes, and also tissue malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathion peroxidase (GPX), reduced glutathione (GSH), myeloperoxidase (MPO), blood urea nitrogen (BUN), and serum creatinine (Cr) levels, were determined. RESULTS Kidney tissue MDA and MPO, and serum BUN and Cr levels were found to be significantly higher in the I/R group, but there was no statistically significant difference in the levels of SOD, CAT, GPX, and GSH between the I/R and the control groups. Although apocynin significantly reduced MDA and MPO in group 3 and increased GPX in both treatment groups when compared to the I/R group, the elevated BUN and Cr levels were significantly reduced in treatment groups. Renal I/R injury also induced extensive tubular necrosis, glomerular damage, and apoptosis in the histological evaluation. Apocynin, especially when used during ischemia, ameliorated these histological damages in different amounts in treatment groups. CONCLUSION The beneficial effects of apocynin on renal I/R injury were evaluated for the first time.

Beneficial Effects of Aminoguanidine on Skin Flap Survival in Diabetic Rats

Random flaps in DM patients have poor reliability for wound coverage, and flap loss remains a complex challenge. The protective effects of aminoguanidine (AG) administration on the survival of dorsal random flaps and oxidative stress were studied in diabetic rats. Two months after the onset of DM, dorsal McFarlane flaps were raised. Forty rats were divided into four groups: (1) control, (2) AG, (3) DM, and (4) DM + AG groups. Flap viability, determined with the planimetric method, and free-radical measurements were investigated. In addition, HbA1c and blood glucose levels, body weight measurements, and histopathological examinations were evaluated. The mean flap necrotic areas (%) in Groups I to IV were 50.9 ± 13.0, 32.9 ± 12.5, 65.2 ± 11.5, and 43.5 ± 14.7, respectively. The malondialdehyde (MDA) and nitric oxide (NO) levels were higher in the DM group than in the nondiabetic group, while the reduced glutathione (GSH) levels and superoxide dismutase (SOD) activity were reduced as a result of flap injury. In the diabetic and nondiabetic groups, AG administration significantly reduced the MDA and NO levels and significantly increased GSH content and SOD enzyme activity. We concluded that AG plays an important role in preventing random pattern flap necrosis.

Protective effect of aminoguanidine against nephrotoxicity induced by amikacin in rats

Aminoglycoside antibiotics have long been used in antibacterial therapy. Despite their beneficial effects, aminoglycosides have considerable nephrotoxic and ototoxic side effects. It has been reported that reactive oxygen radical species (ROS) play role in the pathophysiology of aminoglycosides-induced nephrotoxicity. Aminoguanidine (AG) is an effective antioxidant and free radical scavenger which has long been known to protect against nephrotoxicity. We investigated the effects of AG on amikacin (AK)-induced changes of renal malondialdehyde (MDA), glutathione (GSH), blood urea nitrogen (BUN), serum creatinine (Cr) and albumin (Alb) which are used to monitor the development of renal tubular damage. Morphological changes in the kidney were also examined using light microscopy. A total of 21 rats were equally divided into three groups which were: (1) injected with saline, (2) injected with AK, and (3) injected with AK+AG, respectively. AK administration to control rats increased renal MDA and decreased GSH levels. AG administration before AK injection caused significant decreases in MDA and increases in GSH levels in kidneys compared to rats treated with AK alone. The serum BUN level increased slightly, Cr and serum Alb did not change as a result of any treatment. AG tended to decrease the level of serum BUN and did not cause any change in Alb or Cr levels. Morphological changes, including glomerular, tubular epithelial alterations and interstitial edema, were clearly observed in AK-treated rats. In addition, AG reversed the morphological damage to the kidney induced by AK. The results show that AG has a protective effect on nephrotoxicity induced by AK and may therefore improve the therapeutic index of AK.