Rita Stangl

Postconditioning of the lower limb--protection against the reperfusion syndrome.

BACKGROUND Postconditioning-alternating brief cycles of reperfusion/reocclusion applied at the beginning of revascularization-is a potent therapeutic technique, attenuating ischemia-reperfusion injury. Vascular surgery on the lower limb with ischemia-reperfusion injury may give rise to serious systemic complications [organ dysfunction syndrome (MODS), systemic inflammatory response syndrome (SIRS)], a phenomenon called reperfusion-syndrome. MATERIAL AND METHODS We studied the effects of postconditioning on reperfusion-syndrome in a rodent experimental model. Wistar rats underwent 180 min of bilateral lower limb ischemia using an infrarenal crossclamping of the abdominal aorta. Postconditioning consisted of six cycles of 10-s aortic occlusion/10-s declamping at the beginning of reperfusion. Microcirculation of the lower limb was detected with laser Doppler flowmeter. After 4 h of reperfusion, plasma, urine, and histologic samples were collected. RESULTS One hundred eighty-minute ischemia resulted in significant hemodynamic changes after reperfusion. Postconditioning affected the character of the microcirculatory flow, the limb circulation stabilized with hyperemia during reperfusion. Postconditioning caused a significant reduction in systemic inflammatory response (TNF-α, oxygen-derived free radicals). The laboratory and histologic samples implied a significant decrease in distant organ (lung and renal) dysfunctions after postconditioning. CONCLUSION Postconditioning proves to be capable of conferring protection against different organ injuries caused by longer circulatory occlusions during elective major vascular operations.

Reduction of Liver Ischemia-Reperfusion Injury Via Glutamine Pretreatment

BACKGROUND Surgical methods that reduce bleeding during major hepatic resections lead to warm ischemia-reperfusion (I-R) injury of the liver. This is well known to have a considerable impact on the postoperative outcome. Much research work has been done to develop possible protective techniques. We aimed to investigate the effectivity of L-alanyl-L-glutamine dipeptide pretreatment in an animal model of hepatic I-R injury. MATERIALS AND METHODS Male Wistar rats underwent normothermic, 60 min segmental liver ischemia followed by 24 h of reperfusion. The animals (n=30) were divided into three experimental groups: sham operated, I-R, and glutamine (Gln) pretreated. Twenty-four h prior to I-R injury, rats in the Gln group received 500 mg/kg Dipeptiven infusion as glutamine pretreatment. Hepatic microcirculation during the first hour of reperfusion was monitored by noninvasive laser Doppler flowmeter. After a 24-h reperfusion period, liver tissue was analyzed by histologic and immunohistochemical assessments. Serum necroenzyme and antioxidant levels were measured. RESULTS In the Gln group, the integral of the reperfusion curve (RA) and the plateau maximum (PM(10)) of the flow graph showed improving tendency (RA: P=0.096; PM(10): P=0.084). Severity of histologic damage was reduced. Serum necroenzymes (ALT: P=0.042, AST: P=0.044) were significantly lower. Chemiluminescent intensity of liver and plasma was significantly decreased (P=0.0003 and P=0.0496). Further spectrophotometric analysis of liver homogenate samples also showed significant improvement of the redox homeostasis. CONCLUSIONS Our results suggest that L-alanyl-L-glutamine dipeptide pretreatment given 24 h prior to I-R injury could be an effective method to reduce liver damage caused by hepatic inflow occlusion.

Adenosine and inosine exert cytoprotective effects in an in vitro model of liver ischemia-reperfusion injury

Liver ischemia represents a common clinical problem. In the present study, using an in vitro model of hepatic ischemia-reperfusion injury, we evaluated the potential cytoprotective effect of the purine metabolites, such as adenosine and inosine, and studied the mode of their pharmacological actions. The human hepatocellular carcinoma-derived cell line HepG2 was subjected to combined oxygen-glucose deprivation (COGD; 0-14-24 h), followed by re-oxygenation (0-4-24 h). Adenosine or inosine (300–1,000 μM) were applied in pretreatment. Cell viability and cytotoxicity were measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and lactate dehydrogenase methods, respectively. The results showed that both adenosine and inosine exerted cytoprotective effects, and these effects were not related to receptor-mediated actions, since they were not prevented by selective adenosine receptor antagonists. On the other hand, the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA, 10 μM) markedly and almost fully reversed the protective effect of adenosine during COGD, while it did not influence the cytoprotective effect of inosine in the same assay conditions. These results suggest that the cytoprotective effects are related to intracellular actions, and, in the case of adenosine also involve intracellular conversion to inosine. The likely interpretation of these findings is that inosine serves as an alternative source of energy to produce ATP during hypoxic conditions. The protective effects are also partially dependent on adenosine kinase, as the inhibitor 4-amino-5-(3-bromophenyl)-7-(6-morpholino-pyridin-3-yl)pyrido[2,3-d]pyrimidine, 2HCl (ABT 702, 30 μM) significantly reversed the protective effect of both adenosine and inosine during hypoxia and re-oxygenation. Collectively, the current results support the view that during hypoxia, adenosine and inosine exert cytoprotective effects via receptor-independent, intracellular modes of action, which, in part, depend on the restoration of cellular bioenergetics. The present study supports the view that testing of inosine for protection against various forms of warm and cold liver ischemia is relevant.

Posztkondicionálás kísérletes alkalmazása aortakirekesztés kapcsánr

BACKGROUND Postconditioning - using alternating brief cycles of reperfusion/reocclusion applied just at the very beginning of reperfusion - has recently been described as a potent therapeutic technique, attenuating ischaemia-reperfusion injury. In vascular surgery, certain elective interventions involve cross-clamping of major arteries, resulting in temporary ischaemia in large peripheral organs, which thus suffer ischaemia-reperfusion injury. Patients undergoing these operations may develop also serious systemic complications such as multiple distant organ dysfunctions, SIRS, detrimental redistribution of the circulation or even shock, a phenomenon called reperfusion-syndrome. We studied the effects of postconditioning on reperfusion-syndrome in a rodent experimental model. MATERIAL AND METHODS Anaesthetized male Wistar rats underwent 180 minutes of bilateral lower limb ischaemia and 4 hours of reperfusion using an infrarenal cross-clamping of the abdominal aorta. Control animals underwent no additional intervention. Postconditioning consisted of 6 cycles of 10-second aortic occlusion/10-second declamping starting at the beginning of reperfusion. Haemodynamic parameters were observed with invasive arterial manometer, microcirculation of the lower limb was detected with laser-Doppler-flowmeter. After 4 hours of reperfusion serum, urine, and histological samples were collected. RESULTS 180-minute ischaemia resulted in significant haemodynamic changes after reperfusion. Postconditioning affected the character of the microcirculatory flow curves, the limb circulation stabilized with hyperaemia after reperfusion. Postconditioning caused a significant reduction in systemic inflammatory response (TNF-alpha, oxygen-derived free radicals). The laboratory and histological samples implied a significant decrease in remote organ (lung and renal) dysfunctions after postconditioning. CONCLUSION Postconditioning proves to be capable in conferring protection against different organ injuries caused by longer circulatory occlusions during elective major vascular surgeries.

Levosimendan: a cardiovascular drug to prevent liver ischemia-reperfusion injury?

Introduction Temporary occlusion of the hepatoduodenal ligament leads to an ischemic-reperfusion (IR) injury in the liver. Levosimendan is a new positive inotropic drug, which induces preconditioning-like adaptive mechanisms due to opening of mitochondrial KATP channels. The aim of this study was to examine possible protective effects of levosimendan in a rat model of hepatic IR injury. Material and Methods Levosimendan was administered to male Wistar rats 1 hour (early pretreatment) or 24 hours (late pretreatment) before induction of 60-minute segmental liver ischemia. Microcirculation of the liver was monitored by laser Doppler flowmeter. After 24 hours of reperfusion, liver and blood samples were taken for histology, immuno- and enzyme-histochemistry (TUNEL; PARP; NADH-TR) as well as for laboratory tests. Furthermore, liver antioxidant status was assessed and HSP72 expression was measured. Results In both groups pretreated with levosimendan, significantly better hepatic microcirculation was observed compared to respective IR control groups. Similarly, histological damage was also reduced after levosimendan administration. This observation was supported by significantly lower activities of serum ALT (pearly = 0.02; plate = 0.005), AST (pearly = 0.02; plate = 0.004) and less DNA damage by TUNEL test (pearly = 0.05; plate = 0.034) and PAR positivity (pearly = 0.02; plate = 0.04). Levosimendan pretreatment resulted in significant improvement of liver redox homeostasis. Further, significantly better mitochondrial function was detected in animals receiving late pretreatment. Finally, HSP72 expression was increased by IR injury, but it was not affected by levosimendan pretreatment. Conclusion Levosimendan pretreatment can be hepatoprotective and it could be useful before extensive liver resection.

Posztkondicionálás kísérletes alkalmazása aortakirekesztés kapcsán Effect of postconditioning in major vascular operations on rats

BACKGROUND Postconditioning - using alternating brief cycles of reperfusion/reocclusion applied just at the very beginning of reperfusion - has recently been described as a potent therapeutic technique, attenuating ischaemia-reperfusion injury. In vascular surgery, certain elective interventions involve cross-clamping of major arteries, resulting in temporary ischaemia in large peripheral organs, which thus suffer ischaemia-reperfusion injury. Patients undergoing these operations may develop also serious systemic complications such as multiple distant organ dysfunctions, SIRS, detrimental redistribution of the circulation or even shock, a phenomenon called reperfusion-syndrome. We studied the effects of postconditioning on reperfusion-syndrome in a rodent experimental model. MATERIAL AND METHODS Anaesthetized male Wistar rats underwent 180 minutes of bilateral lower limb ischaemia and 4 hours of reperfusion using an infrarenal cross-clamping of the abdominal aorta. Control animals underwent no additional intervention. Postconditioning consisted of 6 cycles of 10-second aortic occlusion/10-second declamping starting at the beginning of reperfusion. Haemodynamic parameters were observed with invasive arterial manometer, microcirculation of the lower limb was detected with laser-Doppler-flowmeter. After 4 hours of reperfusion serum, urine, and histological samples were collected. RESULTS 180-minute ischaemia resulted in significant haemodynamic changes after reperfusion. Postconditioning affected the character of the microcirculatory flow curves, the limb circulation stabilized with hyperaemia after reperfusion. Postconditioning caused a significant reduction in systemic inflammatory response (TNF-alpha, oxygen-derived free radicals). The laboratory and histological samples implied a significant decrease in remote organ (lung and renal) dysfunctions after postconditioning. CONCLUSION Postconditioning proves to be capable in conferring protection against different organ injuries caused by longer circulatory occlusions during elective major vascular surgeries.

Levosimendan administration in limb ischemia: Multicomponent signaling serving kidney protection

Aims and Objectives Acute renal failure is a severe complication of lower extremity major arterial reconstructions, which could even be fatal. Levosimendan is a dual-acting positive inotropic and vasodilatory agent, which is suspected to have protective effects against cardiac ischemia. However, there is no data available on lower limb or remote organ ischemic injuries therefore the aim of the study was to investigate the effect of levosimendan on lower limb ischemia-reperfusion injury and the corollary renal dysfunction. Methods Male Wistar rats underwent 180 min bilateral lower limb ischemia followed by 4 or 24 hours of reperfusion. Intravenous Levosimendan was administered continuously (0.2μg/bwkg/min) throughout the whole course of ischemia and the first 3h of reperfusion. Results were compared with sham-operated and ischemia-reperfusion groups. Hemodynamic monitoring was performed by invasive arterial blood pressure measurement. Kidney and lower limb muscle microcirculation was registered by a laser Doppler flowmeter. After 4h and 24h of reperfusion, serum, urine and histological samples were collected. Results Systemic hemodynamic parameters and microcirculation of kidney and the lower limb significantly improved in the Levosimendan treated group. Muscle viability was significantly preserved 4 and 24 hours after reperfusion. At the same time, renal functional laboratory tests and kidney histology demonstrated significantly less expressive kidney injury in Levosimendan groups. TNF-α levels were significantly less elevated in the Levosimendan group 4 hours after reperfusion. Conclusion The results claim a protective role for Levosimendan administration during major vascular surgeries to prevent renal complications.