Sevim Ercan

The cytoprotective effects of verapamil and iloprost (zk-36374) on ischemia reperfusion injury of kidneys

We investigated the cytoprotective effects of verapamil, a Ca channel blocker, and of iloprost (ZK 36374), a stable prostacyclin analogue, on ischemia/reperfusion (I/R) injury in Wistar albino rat kidneys that were subjected to 60 min of warm ischemia and reperfusion. The groups included sham, ischemia-untreated (ISCH), verapamil-treated (VER), iloprost-treated (ILO), and verapamil + iloprost (VER+ILO)-treated rats. The 7-day survival of all the treated groups was better than that of the ISCH group. The creatinine concentration on the 3rd day was significantly lower in the VER+ILO group than in the ISCH group. Serum creatinine on day 3 was also low in the VER+ILO groups compared to the ISCH group, although the differences were not significant. The creatinine values on day 7 were significantly lower in the VER and ILO group than in the control, VER, or ILO groups. The malondialdehyde (MDA) concentrations of the kidney cortex tissue after reperfusion in all groups were higher than normal. The tissue-reduced glutathione (GSH) concentrations of the kidneys sampled immediately after reperfusion were significantly lower in the ISCH group than in all of the other treated groups. These results indicate that although verapamil and iloprost have independent cytoprotective effects on 60-min warm ischemia/reperfusion injury of rat kidneys, the protection afforded when both drugs are combined is synergistic. The mechanism of cytoprotection is not limited to the suppression of lipid peroxidation, and a nearly complete protection of reperfusion injury can be obtained by such an intervention.

Leukotriene C4 and prostaglandin E2 activities in the serum and cerebrospinal fluid during acute cerebral ischemia.

Lipoxygenase pathway products of arachidonic acid (AA) metabolism (known as leukotrienes, LTs) are produced in the brain during pathologic conditions such as ischemia, hemorrhage, trauma, and seizure in which the release of AA is sustained by the activation of local phospholipases. The most common type of LT in the central nervous system is an LTC4 which is a highly potent vasoconstrictor leading to increase in vascular permeability. In this study, we compared the serum (S) and cerebrospinal fluid (CSF) prostaglandin E2 (PGE2) and LTC4 levels in 13 consecutively admitted patients with acute cerebral ischemia aged 55-80 years with 10 age-matched controls. Patients with previous glucocorticosteroid and antiinflammatory drug usage were not included in the study. S and CSF samples were drawn during the first 72 h of the attack, and samples were evaluated by bioassay. There was no significant difference in S PGE2 and LTC4 values, whereas a significant difference was observed between CSF PGE2 and LTC4 values as compared with the control group. The high levels of CSF PGE2 and LTC4-like activity in acute cerebral ischemia may indicate that these mediators have a role to play in cerebral edema. The CSF PGE2/LTC4 ratio was also found to be reduced in the ischemic group implying higher LTC4 synthesis than PGE2 synthesis. In the light of these findings, we suggest that use of a selective antagonist of LTs may be helpful in reducing the ischemic penumbra during acute cerebral ischemia by controlling the vasogenic edema.

The alterations of leukotriene C4 and prostaglandin E2 levels following different ischemic periods in rat brain tissue

Leukotrienes and prostaglandins are formed from arachidonic acid by activation of local phospholipases in pathological conditions such as cerebral ischemia, subarachnoid hemorrhage, cerebral tumors and seizures. These mediators, especially leukotrienes have a very potent vasoconstrictor effect on cerebral arteries. Experimental studies have shown that this effect, by increasing vascular permeability causes vasogenic edema that contributes to the ischemic penumbra. In this study, after developing an experimental animal model simulating the concept of ischemic penumbra in the rat, the levels of leukotriene C and prostaglandin E2 produced in the forebrain were measured and the effects of these mediators in prolonged ischemia were investigated. The results, in the first 4 min of ischemia, showed that the arachidonic acid metabolites, particularly, leukotriene C4, reached a peak in the ischemic cerebral tissue in association with leukocyte accumulation. Later in the 15th min, significant decreases in leukotriene C4 and prostaglandin E2 levels were seen. In the 1st and 4th h, probably due to the stimulation of the relevant enzymes by free oxygen radicals in the ischemic tissue; the levels increase again, returning to control values by the 12th h. It is concluded that the use of lipoxygenase inhibitors and free radical scavengers may be helpful to limit the infarct area in the first 4 h of ischemia.

The effect of iloprost and NDGA in ischemia reperfusion injury in rat liver

In this study, the effects of iloprost (ZK 36374) and NDGA on warm ischemia and reperfusion injury in rat liver were investigated. Rats were given isotonic saline (control group), iloprost 25 micrograms/kg i.v. (group II) just before warm ischemia or NDGA 10 micrograms/kg i.v. (group III) 5 min before reperfusion or the same drugs were given together (group IV). Serum SGOT, SGPT, and LDH values and tissue malondialdehyde (MDA), glutathione (GSH), prostaglandin (PG)E2, and leukotriene (LT)C4 levels were determined after ischemia-reperfusion injury. Histopathologic examination of the liver was carried out under the light microscope. The serum SGOT, SGPT and LDH levels improved significantly in groups II, III, and IV when compared with the control group (p < 0.05). There was a significant decrease (p < 0.05) in tissue MDA levels and significant increase (p < 0.05) in tissue GSH levels in group I, when compared with group IV and the control groups. The values did not differ significantly in group IV when compared to controls. The LTC4/PGE2 ratio was low and histologic findings were worse in group III. In conclusion, iloprost was found to be beneficial in preventing the ischemia-reperfusion injury in the rat livers. NDGA, either by direct toxic effect or by shifting the arachidonic acid metabolism to the cyclooxygenase route, was not found to be as effective. Iloprost and NDGA did not exert a synergist effect.

Role of endogenous endothelin peptides in intestinal ischemia-reperfusion injury in rats.

In this study, the effects of BQ123 (an ET(A) receptor antagonist), bosentan (a nonselective ET(A)-ET(B) antagonist), and phosphoramidon (an endothelin converting enzyme inhibitor) were investigated on intestinal mucosal lesion formation and changes in tissue PGE2 and LTC4 levels due to intestinal ischemia-reperfusion (I/R) injury in rats. Following 30 min of ischemia, the substances were given via the inferior caval vein, and 10 min later the intestine was subjected to reperfusion for 30 min. The intestinal specimens were evaluated both microscopically and the tissue PGE2 and LTC4 levels were obtained for each group. The histopathologic examination revealed a significant reduction in tissue injury in both BQ123 and phosphoramidon pretreated groups compared with the control group. Bosentan, on the contrary, did not decrease the injury. The pharmacologic examination revealed a significant reduction of PGE2-like activity in both BQ123 and phosphoramidon pretreated groups, compared with the control group, while LTC4-like activity remained unchanged except for an increase in the bosentan pretreated group.

The effect of nordihydroguaiaretic acid on leukotriene C4 and prostaglandin E2 production following different reperfusion periods in rat brain after forebrain ischemia correlated with morphological changes

Leukotriene C4 (LTC4) and prostaglandin E2 (PGE2) are the 5-lipoxygenase and cyclooxygenase metabolites of arachidonic acid (AA). They constrict blood vessels and enhance vascular permeability inducing vasogenic edema that may hurt the ischemic penumbra after cerebral ischemia and reperfusion. Nordihydroguaiaretic acid (NDGA) is known as the most potent inhibitor of 5-lipoxygenase in different tissues. Furthermore, it has considerable inhibitory activity against cyclooxygenase. In this study, after developing a global ischemic model in the rat, the levels of LTC4 and PGE2 in the forebrain were measured, following different reperfusion periods after 10 min ischemia including 8 rats for each reperfused group. Sham operations were performed for each corresponding control group (n = 8). AA metabolites were then correlated with neuropathological findings. In the combined reperfused groups both metabolites increased significantly when compared with 10 min, ischemic group (P < 0.05). In the 8 min reperfused group, PGE2 and LTC4 increased significantly compared with each corresponding control group (P < 0.005). These mediators also increased to high levels compared with the 4 min reperfused group (P < 0.05, P < 0.005). PGE2 and LTC4 were reduced significantly at the 15th and 60th min of reperfusion compared with the 8 min reperfused group (P < 0.05, P < 0.005). NDGA (0.1 mg/kg) reduced both metabolites in the 8 min reperfused group significantly (P < 0.05). Brain cortex specimens were taken for light and electromicroscopical investigations. No significant differences were noted between the structural changes in the 4, 8 and 15 min of reperfusion and NDGA administered groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Does PGE2 act as a mediator for endothelin release

To investigate the effect of iloprost (ZK 36374) and thromboxane synthetase inhibitor UK 38485 on endothelin release by the intestinal vascular endothelium after ischemia/reperfusion (IR) injury, five experimental groups were formed. The groups consisted of sham, control, iloprost treated (ILO), UK 38485 treated (TSI), and iloprost + UK 38485 treated (ILO + TSI) groups. The last three groups received the corresponding agents and then the superior mesenteric artery was clamped for 30 min followed by 90 min reperfusion. Endothelin levels in the portal blood and malondialdehyde (MDA), prostaglandin E2 (PGE2) and leukotriene C4 (LTC4) levels in the intestinal tissue were determined. The MDA levels increased significantly in the control group and this increase was reversed in ILO, TSI, and ILO + TSI groups, the two drugs together showing a synergistic effect in preventing lipid peroxidation. The changes in the LTC4 levels were not significant among the groups. The increased endothelin levels in the control group were reversed in ILO and TSI groups but these two agents did not have a synergistic effect. Increased PGE2 levels were reversed with iloprost but neither UK 38485 nor the combination of the two agents was effective in decreasing PGE2 levels. It is concluded that endothelin release after mesenteric IR injury is relatively unrelated to lipid peroxidation and the lipoxygenase pathway. The cylooxygenase pathway has a direct effect on endothelin release and PGE2 may act as a mediator.

The effects of indomethacin, NDGA, allopurinol and superoxide dismutase on prostaglandin E2 and leukotriene C4 levels after mesenteric ischemia-reperfusion injury

In this study, the changes of arachidonic acid metabolites after an ischemia-reperfusion (I/R) period are investigated. The cyclooxygenase and lipoxygenase metabolites were found to be significantly increased after a 45 min period of ischemia followed by 5 min of reperfusion. Prostaglandin E2 (PGE2)- and leukotriene C4 (LTC4)-like activities did not change in the ischemic period, but they both increased after reperfusion. A cyclooxygenase inhibitor indomethacin and lipoxygenase inhibitor nordehydroguaretic acid (NDGA) decreased PGE2- and LTC4-like activities, respectively, while allopurinol and superoxide dismutase (SOD) decreased both activities. According to our results, it can be assumed that free oxygen radicals are responsible for the elevation of PGE2- and LTC4-like activities and both of these arachidonic acid metabolites and free oxygen radicals are the main necrotizing agents in ischemia-reperfusion induced damage.

The effects of prostacyclin analogue ZK 36374 and thromboxane synthetase inhibitor UK 38485 on mesenteric ischemia in guinea pigs

The effects of ZK 36374, a prostacyclin analogue and UK 38485, a thromboxane synthetase inhibitor were studied in guinea pigs after performing mesenteric arterial occlusion. In this study, while ZK 36374 significantly lowered the alkaline phosphatase and creatine phosphokinase values two hours after mesenteric arterial occlusion when compared with the control group (p less than 0.005), UK 38485 did not induce any change. In guinea pigs, when given together, ZK 36374 and UK 38485 lowered the enzyme levels to preligation values and the difference was nonsignificant (p greater than 0.1). The histopathologic investigation of the small intestine after giving ZK 36374 and UK 38345 together revealed minimal changes. These findings stress the importance of preserving the PGI2 levels in the PGI2/TXA2 ratio in preventing the increase of lysosomal enzyme levels and histopathologic changes after mesenteric arterial occlusion in guinea pigs.

Establishment of a primary pleomorphic xanthoastrocytoma cell line: in vitro responsiveness to some chemotherapeutics.

BACKGROUND Anaplastic pleomorphic xanthoastrocytoma is an aggressively growing, malignant, and eventually fatal tumor of the central nervous system. Testing chemotherapeutic drug sensitivity under in vitro conditions would be a useful strategy to determine sensitive or resistant drugs for fatal brain cancers. OBJECTIVE To establish primary cell cultures of excised tumor tissue from pleomorphic xanthoastrocytoma–bearing patients and to test their sensitivity against various anticancer chemotherapy drugs. METHODS Prepared suspensions of the excised tumor tissue from a patient who had a recurrent grade 3 pleomorphic xanthoastrocytoma was cultured in culture dishes until cells began to grow. Immunofluorescent and immunohistochemical visualizations were performed using confocal and light microscopy. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in comparison with 3H-thymidine incorporation assay was used to test cellular toxicity of several anticancer drugs. RESULTS We established vigorously growing primary cells of the tumor. Drug sensitivity testing was conducted successfully. CONCLUSION Primary cell cultures of surgically removed tumor tissues may be useful in studies of cancer biology and chemotherapeutic drug sensitivity for recurrent malignant brain tumors, particularly for anaplastic pleomorphic xanthoastrocytoma.