Mehmet Kaya Ozer

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.

Ischemia-reperfusion leads to depletion of glutathione content and augmentation of malondialdehyde production in the rat heart from overproduction of oxidants: Can caffeic acid phenethyl ester (CAPE) protect the heart?

During restoration of blood flow of the ischemic heart induced by coronary occlusion, free radicals cause lipid peroxidation with myocardial injury. Lipid peroxidation end-products, such as malondialdehyde (MDA), have been used to assess oxygen free radical-mediated injury of the ischemic-reperfused (I/R) myocardium in rats. This experimental study assessed the preventive effect of caffeic acid phenthyl ester (CAPE), antioxidant, on I/R-induced lipid peroxidation in the rat heart. We are also interested in the role of CAPE on glutathione (GSH) levels, an antioxidant whose levels are influenced by oxidative stress. I/R leads to the depletion of GSH which is the major intracellular nonprotein sulphydryl and plays an important role in the maintenance of cellular proteins and lipid in their functional state and acts primarily to protect these important structures against the threat of oxidation. In addition, we also examined morphologic changes in the heart by using light microscopy. The left coronary artery was occluded for 30 min and then reperfused for 120 min more before the experiment was terminated. CAPE (50 μM kg−1) was administered 10 min prior to ischemia and during occlusion by infusion. At the end of the reperfusion period, rats were sacrificed, and the heart was quickly removed for biochemical determination and histopathological analysis. I/R was accompanied by a significant increase in MDA production and decrease in GSH content in the rat heart. 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 I/R plays a causal role in heart injury due to overproduction of oxygen radicals or insufficient antioxidant and CAPE exert cardioprotective effects probably by the radical scavenging and antioxidant activities.

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.

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.

Effect of aminoguanidine on ischemia-reperfusion induced myocardial injury in rats.

Myocardial ischemia-reperfusion (MI/R) has been implicated in the induction of inducible nitric oxide synthase (iNOS) that leads to increase production of nitric oxide (NO). Recently, excessive production of NO has been involved in causing myocardial injury. In our in vivo model, we examined the effects of aminoguanidine (AMG), a known iNOS inhibitor, on percentage infarct size in anaesthetized rats. A total of 14 rats were equally divided into two groups (n = 7 in each group). To produce myocardial necrosis, the left main coronary artery was occluded for 30 min, followed by 120 min of reperfusion, in anesthetized rats. AMG (200 mg kg−1) was given intravenously 10 min before occlusion. The volume of infarct size and the risk zone were determined by planimentry of each tracing and multiplying by the slice thickness. Infarct size was normalized by expressing it as a percentage of the area at risk. Hemodynamic parameters were measured via the left carotid artery. Compared to MI/R group, whereas AMG administration elevated mean arterial blood pressure, statistically reduced the myocardial infarct size (21± 1 and 14± 4%, respectively) and infract size/risk zone (53± 3 and 37± 5%, respectively) in rat model of ischemia-reperfusion. In conclusion, this study indicates that iNOS inhibitor, AMG, show reduction in NO’s side effect in I/R injury.

Ameliorating role of Caffeic acid phenethyl ester (CAPE) against isoniazid- induced oxidative damage in red blood cells

Isoniazid (INH) still remains a first-line drug both for treatment and prophylaxis of tuberculosis, but various organs toxicity frequently develops in patients receiving this drug. We aimed to investigate possible toxic effects of INH on rat red blood cells (RBCs), and to elucidate whether Caffeic acid phenethyl ester (CAPE) prevents a possible toxic effect of INH. Experimental groups were designed as follows: control group, INH group, INH + CAPE group. Compared with the control, the INH caused a significant increase in superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels, and a decrease in glutathione peroxidase (GSH-Px) and catalase (CAT), which are recently used to monitor the development and extent of damage due to oxidative stresses. CAPE administration to INH group ameliorated above changes due to INH.

Effects of pentoxifylline on amikacin-induced nephrotoxicity in rats.

The nephrotoxicity of amikacin (AK) was prevented with pentoxifylline (PTX) in a rat model. Rats were received a single injection of AK (1.2 g/kg, i.p.) with or without PTX pretreatment (25 mg/kg, orally). Renal morphology was investigated by light microscopy. Tissue samples and trunk blood were also obtained to determine renal malondialdehyde (MDA), blood urea nitrogen (BUN), and creatinine (Cr) levels. MDA production was found to be higher in AK group. PTX administration caused a significant decrease in MDA production. Morphological damage in rats given AK was severe in the kidney, whereas in rats given AK plus PTX, no histological changes occurred. It is concluded that PTX could be useful for reducing the nephrotoxic effects of AK.

Effects of captopril and angiotensin II receptor blockers (AT1, AT2) on myocardial ischemia-reperfusion induced infarct size.

The renin-angiotensin system (RAS) plays a major role in regulating the cardiovascular system, and disorders of the RAS contribute largely to the cardiac pathophysiology, including myocardial ischemia-reperfusion (MI/R) injury. Two subtypes of angiotensin II (Ang II) receptors have been defined on the basis of their differential pharmacological properties. The current study was undertaken to address the question as to whether the inhibition of the angiotensin converting enzyme (ACE) by captopril and the AT1 and AT2 receptor blockers losartan and PD123319 modulate MI/R-induced infarct size in an in vivo rat model. To produce necrosis, a branch of the descending left coronary artery was occluded for 30 min followed by two hours of reperfusion. ECG changes, blood pressure, and heart rate were measured during the experiment. Captopril (3 mg/kg), losartan (2 mg/kg), and PD123319 (20 μg/kg/min) were given in an IV 10 min before ischemia and were continued during the ischemic period. The infarcted area was measured by TTC staining. The volume of infarct and the risk zone was determined by planimetry. Compared to the control group (55.62±4.00%) both captopril and losartan significantly reduced the myocardial infarct size (30.50±3.26% and 37.75±4.44%), whereas neither PD123319 nor PD123319+losartan affected the infarct size volume (46.50±3.72% and 54.62±2.43%). Our data indicates that captopril and losartan exert cardioprotective activity after an MI/R injury. Also, infarct size reduction by losartan was halted by a blockade of the AT2 receptor. Therefore, the activation of AT2 receptors may be potentially protective and appear to oppose the effects mediated by the AT1 receptors.

Effects of misoprostol on cisplatin-induced renal damage in rats

Cisplatin (CP) is a potent anticancer drug. However, it has side effects on kidney such as nephrotoxicity. Abnormal production of reactive oxygen species (ROS) has been accused in the etiology of CP-induced nephrotoxicity. Several ROS scavengers have been reported to prevent nephrotoxicity after CP administration. In this study, we used prostaglandin E1 (PGE1) analogues misoprostol (MP) to reduce this damage. MP has gained considerable interest as a ROS scavenger. Rats were received a single injection of CP (5 mg/kg, i.p.) with or without MP pretreatment (200 mcg/kg, orally). The renal tissue morphology was investigated by light microscopy. Trunk blood was also obtained to determine lipid peroxidation product malondialdehyde (MDA) and activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT). CP administration increased MDA production and decreased SOD and CAT levels in the kidney tissue when compared to the control group. Morphological damage in CP administrated rats was also severe in the kidney tissue. MP treatment after CP application protected the renal tissues from CPs side effect. These findings indicate that MP has beneficial effects on CP induced nephrotoxicity in rats.

Renal damage in rats induced by myocardial ischemia/reperfusion: Role of nitric oxide

Background: It has been demonstrated that myocardial ischemia/reperfusion (MI/R) causes renal damage. However, the mechanism underlying this damage in kidneys during revascularization of myocardium is unclear. Direct renal ischemia/reperfusion has been implicated in the induction of inducible nitric oxide synthase (iNOS) that leads to increase production of nitric oxide (NO). Recently, excessive production of NO has been found to be involved in causing renal injury by formatting peroxinitrite (ONOO–). The aim of this study was to investigate whether NO has a role in this damage, using aminoguanidine (AMG), a known iNOS inhibitor and an antioxidant, in rats undergoing MI/R.