V. Haktan Ozacmak

Beneficial effects of melatonin on reperfusion injury in rat sciatic nerve.

Abstract:  Studies have shown that ischemia–reperfusion (I/R) produces free radicals leading to lipid peroxidation and to damage of the nervous tissue. Melatonin, a main secretory product of the pineal gland, has free radical scavenging and antioxidant properties and has been shown to diminish I/R injury in many tissues. There are a limited number of studies related to the effects of melatonin on I/R injury in the peripheral nervous system. Therefore, in the present study, the protective effect of melatonin was investigated in rats subjected to 2 hr of sciatic nerve ischemia followed by 3 hr of reperfusion. Following reperfusion, nerve tissue samples were collected for quantitative assesment of malondialdehyde (MDA), an oxidative stress marker, and superoxide dismutase (SOD), a principal antioxidant enzyme. Samples were further evaluated at electron microscopic level to examine the neuropathological changes. I/R elevated the concentration of MDA significantly while there was a reduction at SOD levels. Melatonin treatment reversed the I/R‐induced increase and decrease in MDA and SOD levels, respectively. Furthermore, melatonin salvaged the nerve fibers from ischemic degeneration. Histopathologic findings in the samples of melatonin‐treated animals indicated less edema and less damage to the myelin sheaths and axons than those observed in the control samples. Our results suggest that administration of melatonin protects the sciatic nerve from I/R injury, which may be attributed to its antioxidant property.

Erythropoietin Stimulates Wound Healing and Angiogenesis in Mice

Erythropoietin exerts hematopoietic effects by stimulating proliferation of early erythroid precursors. Nonhematopoietic effects of erythropoietin have also been shown. It may act as a new angiogenic factor in wound healing. This study aimed to investigate the effect of systemic administration of recombinant human erythropoietin on wound healing in mice. Dorsal incisional wounds were performed in mice, which were then divided into two groups; a group treated for 7 days with recombinant human erythropoietin, and a control group. Sacrificing animals on day 7, the wound tissues were collected for analysis of wound breaking strength, malondialdehyde, a marker of lipid peroxidation, hydroxyproline, an index of reparative collagen deposition, reduced glutathione levels, and for histological evaluation. The immunohistochemical determination of vascular endothelial growth factor (VEGF) which is believed to be the most prevalent angiogenic factor throughout the skin repair process, was also studied. The treatment significantly increased wound breaking strength by decreasing malondialdehyde and increasing hydroxyproline levels on day 7 after wounding. No statistically meaningful change was observed in reduced glutathione content. VEGF was immunostained significantly more on wound tissue of treated animals compared to the control group. Recombinant human erythropoietin treatment may be effective in wound healing due to inhibition of lipid peroxidation, deposition of collagen, and VEGF expression in wound area.

Protective Effects of L-Arginine on Rat Terminal Ileum Subjected to Ischemia/Reperfusion

Objectives: Studies have shown that nitric oxide (NO) may play a major role in sustaining mucosal integrity; however, NO has been also implicated in the pathogenesis of ischemia/reperfusion (I/R)–related tissue injury. We investigated the effects of L-arginine and NG-nitro L-arginine methyl ester (L-NAME) on the acetylcholine-induced contractile response of ileum and the levels of malondialdehyde (MDA) and reduced glutathione (GSH). Histopathological changes were also evaluated in ileal preparations. Materials and Methods: Male Wistar Albino rats were subjected to mesenteric ischemia (30 min) followed by reperfusion (3 hours). Four groups were designed: sham-operated control; I/R; I/R and L-arginine pretreatment; and I/R and L-NAME pretreatment. After reperfusion, ileum specimens were collected to determine the parameters mentioned above. Results: Following reperfusion, a significant decrease in acetylcholine-induced contractile response, an increase in lipid peroxidation, a decrease in GSH content, and mucosal damage of the ileal preparations were observed. We showed that decreased contractility, increased lipid peroxidation, and reduced GSH content have been reversed by L-arginine but not by L-NAME. Mucosal injury was significantly lowered in the L-arginine group. Conclusions: Treatment with L-arginine exerted a protective effect in intestinal I/R injury, which was mediated in part by regulating MDA and GSH levels, consequently ameliorating impaired contractile response and mucosal injury.

Neuroprotective Efficacy of the Peroxisome Proliferator-Activated Receptor-γ Ligand in Chronic Cerebral Hypoperfusion

Chronic cerebral hypoperfusion can cause learning and memory impairment and neuronal damage resembling the effects observed in vascular dementia. PPAR-γ agonists were shown to modulate inflammatory response and neuronal death following cerebral ischemia. The present study was designed to evaluate possible neuroprotective effects of rosiglitazone, a PPAR-γ agonist, in rat model of chronic cerebral hypoperfusion. Cerebral hypoperfusion was induced by permanent bilateral occlusion of the common carotid arteries. Oral administration of rosiglitazone (1.5, 3, and 6 mg/kg/day) or vehicle was carried out for 5 weeks, starting one week before the surgery. Cognitive performance was assessed using the Morris water maze. The density of S100B protein-immunoreactive astrocytes and the OX-42-labeled microglial activation were estimated. Synaptogenesis was also evaluated by the measurement of synaptophysin, the pre-synaptic vesicular protein, level via western blotting technique. Cerebral hypoperfusion for 30 days induced a significant cognitive impairment along with hyperactivation of both microglial and astroglial cells, and reduction of synaptophysin level. Rosiglitazone treatment (3 and 6 mg/kg) not only suppressed the activation of astrocytes and microglia markedly but also alleviated the impairment of memory and increased the synaptophysin level. In conclusion, our results suggest that the chronic administration of rosiglitazone significantly prevents chronic cerebral hypoperfusion-induced brain damage, at least, partly through suppressing glial activation and preserving synaptic plasticity. Thus, it appears that rosiglitazone may be a promising pharmacological agent in the development of therapeutic approaches for the prevention or treatment of cerebrovascular diseases.

L-Arginine and melatonin interaction in rat intestinal ischemia--reperfusion.

We investigated the combinative effects of l‐arginine and melatonin on the contractile responses of terminal ileum after the intestinal ischemia–reperfusion (I/R), in vivo. Male rats were subjected to mesenteric ischemia (30 min) followed by reperfusion (180 min). We have observed a dramatic decrease in spontaneous basal activity and Ach‐induced contractile response. Our data clearly showed that the contractility decrease was ameliorated by l‐arginine but not by l‐NAME. Melatonin has reversed the inhibition of contractility caused by I/R injury in part. We did not observe an augmentation in the contractility of ileum when we use melatonin and l‐arginine in combination, in fact, melatonin decreased the protective effect of l‐arginine in intestinal I/R injury.

Agmatine attenuates intestinal ischemia and reperfusion injury by reducing oxidative stress and inflammatory reaction in rats

Aims: Oxidative stress and inflammatory response are major factors causing several tissue injuries in intestinal ischemia and reperfusion (I/R). Agmatine has been reported to attenuate I/R injury of various organs. The present study aims to analyze the possible protective effects of agmatine on intestinal I/R injury in rats. Main methods: Four groups were designed: sham control, agmatine‐treated control, I/R control, and agmatine‐treated I/R groups. IR injury of small intestine was induced by the occlusion of the superior mesenteric artery for half an hour to be followed by a 3‐hour‐long reperfusion. Agmatine (10 mg/kg) was administered intraperitoneally before reperfusion period. After 180 min of reperfusion period, the contractile responses to both carbachol and potassium chloride (KCl) were subsequently examined in an isolated‐organ bath. Malondialdehyde (MDA), reduced glutathione (GSH), and the activity of myeloperoxidase (MPO) were measured in intestinal tissue. Plasma cytokine levels were determined. The expression of the intestinal inducible nitric oxide synthase (iNOS) was also assessed by immunohistochemistry. Key findings: The treatment with agmatine appeared to be significantly effective in reducing the MDA content and MPO activity besides restoring the content of GSH. The treatment also attenuated the histological injury. The increases in the I/R induced expressions of iNOS, IFN‐&ggr;, and IL‐1&agr; were brought back to the sham control levels by the treatment as well. Significance: Our findings indicate that the agmatine pretreatment may ameliorate reperfusion induced injury in small intestine mainly due to reducing inflammatory response and oxidative stress.

The effects of S-nitrosoglutathione on intestinal ischemia reperfusion injury and acute lung injury in rats: Roles of oxidative stress and NF-κB

BACKGROUND Intestinal ischemia and reperfusion (I/R) induces oxidative stress, inflammatory response, and acute lung injury. S-nitrosoglutathione (GSNO), a nitric oxide donor, has been documented to have protective effects on experimental ischemia models. AIM The aim of this study was to examine the effect of GSNO on I/R-induced intestine and lung damage and detect the potential mechanisms emphasizing the protective role of GSNO. METHODS Intestinal I/R was induced by occluding the superior mesenteric artery for 30 min followed by reperfusion for 180 min. GSNO was administered intravenously before reperfusion period (0.25 mg/kg). The levels of lipid peroxidation, reduced glutathione, and myeloperoxidase (MPO), histopathological evaluation and immunohistochemical expressions of both nuclear factor KappaB (NF-κB) and inducible nitric oxide (iNOS) in intestine and lung tissues were assessed. RESULTS Histolopathologic evaluation demonstrated that intestinal I/R induced severe damages in the intestine and the lung tissues. Histopathological scores decreased with GSNO treatment. GSNO treatment reduced lipid peroxidation and MPO levels and inhibited expression of NF-κB and iNOS in the intestine. CONCLUSION Our results suggest that GSNO treatment may ameliorate the intestinal and lung injury in rats, at least in part, by inhibiting inflammatory response and oxidative stress.