Mehmet Ozler

Antioxidant effects of melatonin in rats during chronic exposure to hyperbaric oxygen

Abstract:  In addition to its beneficial effects, hyperbaric oxygen (HBO) exposure causes some detrimental effects via oxidative stress. Previous experimental studies showed that melatonin is a useful agent to block single session HBO‐induced oxidative stress. In the present study, we investigated the antioxidant effect of exogenously administered as well as endogenously produced melatonin in lung and brain tissues of rats exposed to long term HBO. The HBO procedure was set as daily exposures to 2.5 ATA of oxygen for 1 hr and a total of 10 sessions. Twenty‐eight male Sprague–Dawley rats were divided into four groups as follows: control, daytime HBO, daytime HBO plus melatonin (5 mg/kg), nighttime HBO. Tissue oxidative/antioxidant status was examined by determining the protein carbonyl content as a criteria for oxidative stress and the activities of the antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px). HBO exposure for 10 days caused significant increases in protein carbonyl content and SOD levels of lung and brain, but GSH‐Px activities remained unaffected. The increases in protein carbonyls were blocked by exogenously administered melatonin and in part by nighttime exposure to darkness whereas the increase of SOD activity was only impeded by endogenously produced melatonin in brain tissue. Lung SOD activity was augmented by endogenous melatonin. In conclusion, melatonin blocks long‐term HBO‐induced cumulative oxidative stress as indicated changes in protein carbonyls. Both exogenously injected and physiologically secreted melatonin has this potential. The effects of HBO‐exposure and melatonin on the activities of the antioxidative enzymes are less clear.

Comparison of the effect of topical and systemic melatonin administration on delayed wound healing in rats that underwent pinealectomy

Abstract Objectives. Melatonin is a hormone which has many systemic effects in addition to its strong antioxidant properties. The aim of the present study was to investigate the difference between sytemic and topical administration of melatonin by forming a chronic wound model in rats whose release of basal melatonin was supressed by pinealectomy. Material and methods. Experimental animals used in the study were divided into four equal groups: (i) a group of normal animals with wound formation (control), (ii) a group of animals who underwent pinelaectomy and wound formation (PINx), (iii) a group that underwent PINx + systemic melatonin administration, and (iv) a group that underwent PINx + topical melatonin administration. Fifteen days after pinealectomy, a bipediculed flap was formed on the back of the rats under anesthesia and then six excisional skin wounds were produced in all groups. Following the treatment that lasted 7 days, on day 8 the wound surface areas were measured and wound tissues were removed under anesthesia. In these tissues the levels of malondialdehit (MDA) and hydroxyproline (OH-proline) and the activities of superoxide dismutase(SOD) and glutathion peroxidase (GSH-Px) were measured. Results. In the PINx group, OH-prolin levels decreased significantly compared to the control group and wound surface areas increased. MDA levels increased compared to the control group, and SOD and GSH-Px decreased accordingly. Conversely, in two melatonin groups in which melatonin was administered systemically or topically MDA decreased while SOD ve GSH-Px enzymes increased. Conclusion. In conclusion, in the present study it was shown that wound healing was prolonged in experimental animals deprived of melatonin through pinealectomy. Melatonin exerts positive effects on wound healing, whether it is administered topically or systemically.

Time-dependent course of hyperbaric oxygen-induced oxidative effects in rat lung and erythrocytes.

1  The oxygen toxicity of hyperbaric oxygen (HBO) treatment has long been of interest. There is an extensive amount of information regarding the role oxidative stress plays after HBO exposure in different tissues, but the question of the persistence of this oxidative effect has not been thoroughly elucidated. 2 The present study was performed to elucidate the persistence of the oxidative effects of HBO on rat lungs and erythrocytes after they had been subjected to 100% oxygen exposure. 3 Rats were divided into five groups. All animals, except those in the control group, were subjected to 100% oxygen for 2 h at 3 ATA (≡ 300 kPa). Rats were killed at 30, 60, 90 or 120 min after exposure and thiobarbituric acid‐reactive substances (TBARS) levels and the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined. 4 Thiobarbituric acid‐reactive substances levels and SOD and GPx levels were found to be significantly increased in lung tissue up to 60 min after exposure. Superoxide dismutase activity persisted at significantly high values for 90 min after exposure in erythrocytes and the lung. The TBARS levels in erythrocytes were also significantly higher for 60 min, whereas increased GPx activity was observed to persist for only 30 min. 5 The oxidative effect of HBO exposure declines to physiological levels within 90 min at most for erythrocytes and in lung tissue in rats. Further studies should focus on the molecular mechanisms that can be activated during this time interval.

Oxidative Stress Levels in Rats Following Exposure to Oxygen at 3 atm for 0 - 120 min

BACKGROUND Hyperbaric oxygen (HBO) is known to cause oxidative stress in several organs and tissues. We previously defined the pressure-related oxidative effects of HBO in several tissues of rats. This study was performed to elucidate the relationship of HBO exposure time to its oxidative effects. METHODS A total of 49 rats were randomly divided into 5 groups. Study groups were subjected to 3 atm HBO for 30, 60, 90, and 120 min except the control group. Their blood and lungs were removed immediately after exposure and used for analysis. Thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) levels were determined to reflect oxidant and antioxidant status. RESULTS TBARS levels were found to increase in a time-dependent manner in both erythrocytes [median (min-max); from 0.65 (0.39-0.84) with 30 min HBO exposure up to 1.26 (1.00-1.44) nmol x g(-1) hemoglobin after 120 min] and lung tissue [from 2140 (1550-2510) up to 5465 (5090-5950) nmol x g(-1) protein]. Similarly, SOD activity also presented a dose-dependent course from 0.06 (0.05-0.10) to 0.18 (0.14-0.26) U x g(-1) hemoglobin in erythrocytes and from 16,660 (3479-25,994) to 52,522.5 (41,362-65,799) U x g(-1) protein in lung tissue. In contrast, GSH-Px activity reflected an irregular trend; its levels were mostly found to be increased, but they were decreased at one stage (in the erythrocytes of 30-min exposed rats). CONCLUSIONS The results of this study exhibited a clear relationship of HBO-induced oxidative action to exposure time. This action was most pronounced from 90 to 120 min of exposure.

Long-term exposure to repetitive hyperbaric oxygen results in cumulative oxidative stress in rat lung tissue

Context: Despite its known benefits, hyperbaric oxygen (HBO) is also reported to enhance the production of reactive oxygen species and can cause oxidative stress in several tissues. Previous studies had shown that HBO-induced oxidative stress is directly proportional to both its exposure pressure and duration. Nevertheless, these studies were usually performed with single-session HBO exposure but its clinical use commonly depends on long-term exposure periods. Objective: To clarify the oxidative effect of long-term repetitive HBO in the lung tissue of rats. Materials and methods: Male Sprague-Dawley rats were divided into six study groups exposed to consecutive HBO sessions (2.8 atm/90 min) for 5, 10, 15, 20, 30, and 40 days. Animals were sacrificed 24 h after the last HBO session. An additional control group was set to obtain normal data. Lung malondialdehyde (MDA) and carbonylated protein (PCC) levels were determined as measures of oxidative stress along with the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase. Results: None of the measured parameters showed any changes among the groups exposed to 5–15 HBO sessions. However, MDA, PCC, and SOD were found to be significantly increased in the 20 to 40 session groups. Discussion and conclusion: These results indicate that repetitive treatment with HBO may cause oxidative stress in critical tissues including the lung. Although HBO-mediated free radicals are accepted to be responsible for the benefits of this therapeutic modality, especially in cases with prolonged exposure, possible injurious effects of supranormal values of bio-oxidative products need to be considered.

The protective effects of ozone therapy in a rat model of acetaminophen-induced liver injury

OBJECTIVES Acetaminophen (APAP) overdose may cause acute liver injury. Ozone therapy (OT) is shown to reduce inflammation and necrosis in several entities. Thus, we have designed this study to evaluate the efficacy of OT in a rat model of APAP-induced liver injury. METHODS Twenty-seven Sprague-Dawley rats were divided into three groups: sham, APAP and APAP+OT groups. In the APAP and the APAP+OT groups, liver injury was induced by oral administration of 1 g/kg APAP. The APAP+OT group received a single dose ozone/oxygen mixture (0.7 mg/kg) intraperitoneally 1h after APAP administration. All animals were killed at 24 hour after APAP administration. Blood samples and liver tissues were harvested to determine liver injury and oxidative stress parameters. Liver tissues and blood samples were obtained for biochemical and histopathological analyses. RESULTS APAP administration caused necrosis in the liver after 24h. The degrees of liver necrosis of the APAP group were higher than the other groups (in both p<0.05, respectively). In the APAP+OT group, liver antioxidant enzymes activities were significantly higher than the APAP group (p<0.05), but were lower than the sham group (p<0.05). In the sham group, serum neopterin, a marker of cell-mediated immunity, concentrations (4.8±1.2 nmol/L) were lower than the APAP (14.7±1.4 nmol/L) and APAP+OT groups (7.5±2.4 nmol/L) (in both p<0.05, respectively). CONCLUSION Our results showed that OT prevented liver necrosis in rats and reduced neopterin levels. These findings suggest that the use of OT as an adjuvant therapy which might improve the outcome in APAP induced liver injury.

Melatonin prevents peritoneal adhesions in rats

Background and Aim:  Intra‐abdominal adhesions are important postoperative complications following abdominal surgery. The adhesions that develop form the basis of more advanced pathology such as intestinal obstruction or infertility. Melatonin is secreted from the pineal gland in a circadian pattern; this molecule has potent antioxidant characteristics and has beneficial effects in many models of inflammation. The aim of this study was to evaluate the effects of melatonin on peritoneal adhesions created in rats.

Ozone therapy prevents renal inflammation and fibrosis in a rat model of acute pyelonephritis

Abstract Introduction. Not only bacterial characteristics but also oxidative/nitrosative stress could play a significant role in renal parenchymal inflammatory processes in acute pyelonephritis (APN). This study was conducted to evaluate the effect of ozone therapy (OT), as an immunomodulator and antioxidant, on the renal function, morphology and biochemical parameters of oxidative stress in an experimental model of APN in rats. Materials and methods. Forty rats were divided equally into five groups as control, APN, APN + Antibiotic, APN + OT, and APN + Antibiotic + OT. APN was induced by 0.1 ml of freshly prepared Escherichia coli (ATCC 25922) solution containing 1010 colony-forming unit/ml into the kidney. A control group was administered 0.1 ml of 0.9 % NaCl solution. Treatment was begun 72 h after bacterial inoculation. Control and APN groups were given 0.9% NaCl solution, APN + Antibiotic and APN + OT were given either antibiotic (ciprofloxacine 150 mg/kg intramuscular/twice daily) or OT. APN + Antibiotic + OT group was given both antibiotic and OT for five consecutive days. At the end of the seventh day, animals were killed via decapitation and trunk blood was collected. Both kidneys were harvested and one half of each kidney were immediately stored for antioxidant enzyme activity, tissue lipid peroxidation and protein carbonyl content. The remainder was fixed for histopathologic examination. Results. E. coli-induced APN increased the renal glomerular and tubular dysfunction, oxidative stress parameters and antioxidant enzyme activities. Either antibiotherapy or OT markedly ameliorated renal dysfunction, the antioxidant status of the kidneys and histopathological injuries subjected to E. coli-induced APN. Interestingly, the combination of antibiotherapy and OT was much more effective than either of the treatment modalities alone. Conclusion. The combination of antibiotherapy and OT markedly ameliorated renal dysfunction and improved antioxidant status and histopathologic modalities in rats subjected to E. coli-induced APN than either antibiotherapy or OT treatment alone. Therefore, OT may be considered as an adjuvant therapy to classical antibiotherapy to prevent renal inflammation and fibrosis in APN.

Effects of medical ozone therapy on acetaminophen-induced nephrotoxicity in rats

Acetaminophen (APAP), also known as paracetamol, is the commonest cause of toxic ingestion in the world. Because overdose of APAP has life-threatening effects on kidney, treatment of APAP-induced nephrotoxicity has life-saving importance. Aim of the study was to evaluate the efficacy of medical ozone therapy in experimental model of APAP toxication. Twenty-one male Wistar rats (200–250 g) were randomly assigned into three groups containing seven rats each: Sham, control (only APAP treated), and APAP + ozone therapy groups. Rats were killed 48 hours after administration of APAP. Urea, creatinine levels in the blood, and malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activity in renal tissue were measured. Kidney tissues were stained with hematoxylin and eosin for histological assessment. APAP administration deteriorated the renal functions and significantly elevated renal MDA levels and depleted SOD and GSH-Px activities. Ozone therapy significantly reduced the MDA level, increased the SOD and GSH-Px activities, and normalized the renal histology. In conclusion, our study results are consistent with encouraging data for ozone therapy on APAP-induced nephrotoxicity in rats by improving antioxidant mechanism and oxidative stress.

Poly(ADP-ribose) polymerase inhibition modulates experimental acute necrotizing pancreatitis-induced oxidative stress, bacterial translocation and neopterin concentrations in rats

Various studies have been performed to find out novel treatment strategies for acute necrotizing pancreatitis (ANP). Inhibition of poly(ADP-ribose) polymerase (PARP) is shown to reduce inflammation in several pathological conditions. We aimed to evaluate the efficacy of benzamide, a PARP inhibitor, in an experimental model of ANP. Thirty Sprague–Dawley rats were divided into three groups: sham-operated, ANP and ANP + benzamide groups. All groups except the sham-operated group were subjected to the ANP procedure, induced by infusing of 1 mL/kg of 3% sodium taurocholate into the common biliopancreatic duct. The ANP + benzamide group received 100 mg/kg/day benzamide intraperitoneally for a total of three days after induction of pancreatitis. The surviving animals were killed at the fourth day and the pancreas was harvested for biochemical, microbiological and histological analysis. Blood samples were also obtained from the animals. In the ANP group, a significant increase was observed in concentrations of serum amylase and neopterin and tissue oxidative stress indices (malondialdehyde, superoxide dismutase and glutathione peroxidase). Almost all of these changes were found to be reversed to near their normal values in the ANP + benzamide group. Histological injury scores were significantly higher in the ANP group than in the sham group (P < 0.05, ANP versus sham), and were significantly lower in the ANP + benzamide group than in the ANP group (P < 0.05, ANP + benzamide versus ANP). Evaluation of bacterial translocation identified significantly fewer infected sites in the ANP + benzamide group than in the ANP animals (P < 0.01). We observed that inhibition of PARP with benzamide reduced the severity, the mortality, the bacterial translocation rates and the neopterin concentrations in an experimental ANP model in rats. These findings suggest that it may be possible to improve the outcome of ANP by using PARP inhibitors.