Ischemia/reperfusion injury

Effects of dexpanthenol and N-acetylcysteine pretreatment in rats before renal ischemia/reperfusion injury

BACKGROUND

We investigated the anti-inflammatory and protective effects of concomitant use of dexpanthenol (DXP) and N-acetylcysteine (NAC) induced ischemia/reperfusion (I/R) injury of kidney.

METHODS

Forty rats were randomly divided into 5 groups. In all groups except for Group 1(Sham), renal arteries bilaterally occluded with vascular clamp for IR injury. Group 1(Sham), received a single dose of 10 mL/kg isotonic saline daily by intraperitoneal (IP) injection for three days. Group 2(IR), received a single dose of 10 mL/kg isotonic saline daily by IP injection for three days. Group 3(IR + NAC), received 300 mg/kg NAC daily by IP injection for three days. Group 4(IR + DXP), received 500 mg/kg DXP daily by IP injection for three days. Group 5(IR + NAC + DXP), received 500 mg/kg DXP and 300 mg/kg NAC daily by IP injection for three days. Serum urea (BUN), creatinine (Cr) and neutrophil gelatinase-associated lipocalin (NGAL, lipocalin 2, siderocalin) levels were measured as kidney function tests. TNF-α levels were measured as inflammatory marker. Tissue sections were evaluated histopathologically under light microscopy.

RESULTS

IR + NAC + DXP group received both NAC and DXP before induction of renal I/R and as the biochemical and histopathological data revealed the results of the IR + NAC + DXP group and sham group were similar. Biochemically and histopathologically, combined use of NAC and DXP has better results when each of them used alone.

CONCLUSION

We concluded that concomitant use of DXP and NAC plays a major role against I/R injury and may be useful in acute treatment of I/R induced renal failure.

Use of nitric oxide producer L-arginine during infusion therapy of experimental hemorrhagic shock

Experiments on rats showed that infusion of NO precursor L-arginine before bleeding enhanced their tolerance to hemorrhagic shock. When infused after blood loss as a component of saline solution, L-arginine improved efficiency of infusion therapy for hemorrhagic shock and increased survival rate of the animals.

Tadalafil significantly reduces ischemia reperfusion injury in skin island flaps

Introduction:

Numerous pharmacological agents have been used to enhance the viability of flaps. Ischemia reperfusion (I/R) injury is an unwanted, sometimes devastating complication in reconstructive microsurgery. Tadalafil, a specific inhibitor of phosphodiesterase type 5 is mainly used for erectile dysfunction, and acts on vascular smooth muscles, platelets and leukocytes. Herein, the protective and therapeutical effect of tadalafil in I/R injury in rat skin flap model is evaluated.

Materials and Methods:

Sixty epigastric island flaps were used to create I/R model in 60 Wistar rats (non-ischemic group, ischemic group, medication group). Biochemical markers including total nitrite, malondialdehyde (MDA) and myeloperoxidase (MPO) were analysed. Necrosis rates were calculated and histopathologic evaluation was carried out.

Results:

MDA, MPO and total nitrite values were found elevated in the ischemic group, however there was an evident drop in the medication group. Histological results revealed that early inflammatory findings (oedema, neutrophil infiltration, necrosis rate) were observed lower with tadalafil administration. Moreover, statistical significance (P < 0.05) was recorded.

Conclusions:

We conclude that tadalafil has beneficial effects on epigastric island flaps against I/R injury.

The impact of lifestyle-related risk factors on cardiac response to ischemia and possibilities to restore impaired ischemic tolerance

Risk factors (RF) of cardiovascular diseases associated with modern lifestyle, such as stress, chronically increased blood pressure, hyperglycemia and dyslipidemia have a negative impact on the heart exposed to ischemia: they may facilitate its lethal injury (myocardial infarction) and occurrence of sudden death due to ventricular arrhythmias. On the other hand, some stressful stimuli related to RF including reactive oxygen species, transient episodes of ischemia (hypoxia), high glucose and other may play a dual role in the pathogenesis of ischemia/reperfusion (I/R) injury (IRI). Besides their deleterious effects, these factors may trigger adaptive processes in the heart resulting in greater resistance against IRI, which is also a characteristic feature of the female myocardium. However, sensitivity to ischemia is increasing with age in both genders. Current research indicates that comorbidity related to lifestyle may impair the cardiac response to acute ischemia not only by interference with pathophysiological mechanisms of IRI per se, but via suppression of intrinsic protective mechanisms in the heart and its ability to tolerate the ischemic challenges, although the role of RF has not been unequivocally proven. Moreover, even pathologically altered myocardium need not completely lose its adaptive potential. In addition, increased ischemic tolerance can be induced by the pleiotropic (independent of the primary) effects of some hypolipidemic and antidiabetic drugs, even in the diseased myocardium. This review addresses the issue of the impact of RF on cellular cardioprotective mechanisms and the possibilities to restore adaptive potential in subjects challenged with several RF. Reactivation of adaptive processes in the myocardium taking into consideration gender and age can contribute to optimalization of antiischemic therapy.

[Data on liver enzyme and histological changes caused by intermittent clampings of the hepatoduodenal ligament in an experimental model]

Intermittent compression of the structures of the hepatoduodenal ligament, is often performed during liver surgery. As a result, changes in hepatic blood supply and consequent reperfusion induced tissue damages will develop. Ischemia-reperfusion injury, which occur in local and distant regions, influence outcome of hepatic surgery, and it is in close correlation with the duration of hypoxia during the intervention. In animal model the effect of Baron/Pringle manoeuvre was investigated in terms of changes in liver function tests and histology. The study was carried out on 12 Beagle dogs, clamping of the hepatoduodenal ligament for 3×15 minutes then half an hour reperfusion was performed followed by blood and tissue sampling. Significant histological changes were observed both in the liver as well as the small intestine. In terms of liver function changes, GPT elevation occurred the earliest, GOT and LDH were also increased at the end of the 30 minutes reperfusion. In this animal model, the third 15 minutes compression turned out to be too long. Elevation in GPT levels was the most sensitive marker.

Effects of cyclosporine pretreatment on tissue oxygen levels and cytochrome oxidase in skeletal muscle ischemia and reperfusion

We hypothesized that pretreatment with single-dose cyclosporine (CsA) prevents alterations and improves tissue oxygen and mitochondrial cytochrome oxidase redox (CytOx) state in skeletal muscle ischemia and reperfusion-reoxygenation (I/R). Latissimus dorsi muscle was prepared and mobilized in New Zealand white rabbits. Ischemia was induced for 4 h, followed by 2 h of reperfusion. The animals were randomized to receive a 60-mg/kg intravenous bolus of CsA (CsA group, n = 10) or physiologic saline (control, n = 10) at 10 min before ischemia onset. Muscle tissue oxygen tension (PtO(2)) and mitochondrial CytOx were measured during I/R simultaneously. High-energy phosphate (HEP) levels were determined using high-field (31)P magnetic resonance spectroscopy. Mitochondrial viability index and wet-to-dry ratio were used to assess the tissue viability between groups. Decreases in tissue oxygen levels and CytOx were slower during ischemia in the CsA group in comparison to control group, also the loss of phosphocreatine and adenosine triphosphate depletion. After ischemia, recovery of tissue oxygen, mitochondrial CytOx, and HEP was delayed in controls. Tissue PtO2 in the CsA group (P < 0.05) was significantly higher compared with that in the control group after I/R. Mitochondrial CytOx was also improved in the CsA group (P < 0.01 vs. control). Muscle HEP levels (phosphocreatine, adenosine triphosphate) were significantly preserved in the CsA group versus the control group (P < 0.01, P < 0.05). Mitochondrial viability index and wet-to-dry ratio confirmed significantly preserved tissue and lower edema formation in the CsA group. The pretreatment with single-dose CsA prevents alterations and improves tissue oxygenation and mitochondrial oxidation in skeletal muscle I/R.

Effects of biliverdin administration on acute lung injury induced by hemorrhagic shock and resuscitation in rats

Hemorrhagic shock and resuscitation induces pulmonary inflammation that leads to acute lung injury. Biliverdin, a metabolite of heme catabolism, has been shown to have potent cytoprotective, anti-inflammatory, and anti-oxidant effects. This study aimed to examine the effects of intravenous biliverdin administration on lung injury induced by hemorrhagic shock and resuscitation in rats. Biliverdin or vehicle was administered to the rats 1 h before sham or hemorrhagic shock-inducing surgery. The sham-operated rats underwent all surgical procedures except bleeding. To induce hemorrhagic shock, rats were bled to achieve a mean arterial pressure of 30 mmHg that was maintained for 60 min, followed by resuscitation with shed blood. Histopathological changes in the lungs were evaluated by histopathological scoring analysis. Inflammatory gene expression was determined by Northern blot analysis, and oxidative DNA damage was assessed by measuring 8-hydroxy-2′ deoxyguanosine levels in the lungs. Hemorrhagic shock and resuscitation resulted in prominent histopathological damage, including congestion, edema, cellular infiltration, and hemorrhage. Biliverdin administration prior to hemorrhagic shock and resuscitation significantly ameliorated these lung injuries as judged by histopathological improvement. After hemorrhagic shock and resuscitation, inflammatory gene expression of tumor necrosis factor-α and inducible nitric oxide synthase were increased by 18- and 8-fold, respectively. Inflammatory gene expression significantly decreased when biliverdin was administered prior to hemorrhagic shock and resuscitation. Moreover, after hemorrhagic shock and resuscitation, lung 8-hydroxy-2' deoxyguanosine levels in mitochondrial DNA expressed in the pulmonary interstitium increased by 1.5-fold. Biliverdin administration prior to hemorrhagic shock and resuscitation decreased mitochondrial 8-hydroxy-2' deoxyguanosine levels to almost the same level as that in the control animals. We also confirmed that biliverdin administration after hemorrhagic shock and resuscitation had protective effects on lung injury. Our findings suggest that biliverdin has a protective role, at least in part, against hemorrhagic shock and resuscitation-induced lung injury through anti-inflammatory and anti-oxidant mechanisms.

Effect of ischemia post-conditioning on skeletal muscle oxidative injury, mTOR, Bax, Bcl-2 proteins expression, and HIF-1α/β-actin mRNA, IL-6/β-actin mRNA and caveolin-3/β-actin mRNA expression in ischemia-reperfusion rabbits

This study is designed to investigate the effect of ischemia post-conditioning on IR-induced skeletal muscle injury in limbs of experimental rabbits. Rabbits are randomized to one of the following three groups: sham control, ischemic reperfusion, ischemic postconditioning. The lipid peroxidation level, antioxidant enzymes activities, skeletal muscle mammalian target of rapamycin (mTOR), Bax, Bcl-2 proteins expression and Bcl-2/Bax, and HIF-1α/β-actin mRNA, interleukin-6 (IL-6)/β-actin mRNA and caveolin-3/β-actin mRNA expression were tested in the current study. The results suggested that ischemic postconditioning might decrease lipid peroxidation level, lactic dehydrogenase (LDH), creatine kinase (CK) activities, Bcl-2 proteins expression and Bcl-2/Bax, HIF-1α/β-actin mRNA expression and increase skeletal muscle antioxidant enzymes activities, Bax protein expression and IL-6/β-actin mRNA and caveolin-3/β-actin mRNA expression. These indicated that protective effect of ischemic postconditioning against IR-induced skeletal muscle injury involve into a complex molecular mechanism. Our research results may offer a theoretical guidance for therapy of related clinical diseases.

Expansion of cardiac ischemia/reperfusion injury after instillation of three forms of multi-walled carbon nanotubes

Background

The exceptional physical-chemical properties of carbon nanotubes have lead to their use in diverse commercial and biomedical applications. However, their utilization has raised concerns about human exposure that may predispose individuals to adverse health risks. The present study investigated the susceptibility to cardiac ischemic injury following a single exposure to various forms of multi-walled carbon nanotubes (MWCNTs). It was hypothesized that oropharyngeal aspiration of MWCNTs exacerbates myocardial ischemia and reperfusion injury (I/R injury).

Methods

Oropharyngeal aspiration was performed on male C57BL/6J mice with a single amount of MWCNT (0.01 - 100 μg) suspended in 100 μL of a surfactant saline (SS) solution. Three forms of MWCNTs were used in this study: unmodified, commercial grade (C-grade), and functionalized forms that were modified either by acid treatment (carboxylated, COOH) or nitrogenation (N-doped) and a SS vehicle. The pulmonary inflammation, serum cytokine profile and cardiac ischemic/reperfusion (I/R) injury were assessed at 1, 7 and 28 days post-aspiration.

Results

Pulmonary response to MWCNT oropharyngeal aspiration assessed by bronchoalveolar lavage fluid (BALF) revealed modest increases in protein and inflammatory cell recruitment. Lung histology showed modest tissue inflammation as compared to the SS group. Serum levels of eotaxin were significantly elevated in the carboxylated MWCNT aspirated mice 1 day post exposure. Oropharyngeal aspiration of all three forms of MWCNTs resulted in a time and/or dose-dependent exacerbation of myocardial infarction. The severity of myocardial injury varied with the form of MWCNTs used. The N-doped MWCNT produced the greatest expansion of the infarct at any time point and required a log concentration lower to establish a no effect level. The expansion of the I/R injury remained significantly elevated at 28 days following aspiration of the COOH and N-doped forms, but not the C-grade as compared to SS.

Conclusion

Our results suggest that oropharyngeal aspiration of MWCNT promotes increased susceptibility of cardiac tissue to ischemia/reperfusion injury without a significant pulmonary inflammatory response. The cardiac injury effects were observed at low concentrations of MWCNTs and presence of MWCNTs may pose a significant risk to the cardiovascular system.

Lung Ischemia Reperfusion Injury

Lung ischemia reperfusion injury (LIRI) is a pathologic process occurring when oxygen supply to the lung has been compromised followed by a period of reperfusion. The disruption of oxygen supply can occur either via limited blood flow or decreased ventilation termed anoxic ischemia and ventilated ischemia, respectively. When reperfusion occurs, blood flow and oxygen are reintroduced to the ischemic lung parenchyma, facilitating a toxic environment through the creation of reactive oxygen species, activation of the immune and coagulation systems, endothelial dysfunction, and apoptotic cell death. This review will focus on the mechanisms of LIRI, the current supportive treatments used, and the many therapies currently under research for prevention and treatment of LIRI.

Hyperbaric oxygen therapy alleviates oxidative stress and tissue injury in renal ischemia/reperfusion injury in rats

Hyperbaric oxygen (HBO) therapy has been shown to attenuate renal ischemia/reperfusion (I/R) injury in rats, when applied in the early reperfusion period. The aim of this study was to elucidate possible beneficial effects of HBO therapy on renal I/R injury, when applied 24 h after ischemia. Rats were randomized into three groups: (1) control group (n = 20), (2) I/R group (n = 20), and (3) I/R + HBO group (n = 20). Renal I/R injury was created by interrupting renal blood flow for 30 min with a non-traumatic vascular clamp. HBO therapy was administered 24 h after I/R injury and continued for 5 days. At the end of the study, rats were sacrificed under anesthesia, blood was drawn, and right kidneys were harvested for analysis. Renal I/R injury increased serum and tissue malondialdehyde (MDA) levels and reduced superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels. HBO therapy attenuated MDA levels by increasing SOD and GPx activities. HBO therapy also prevented neutrophil infiltration and tissue injury in kidneys. Taken together, HBO therapy has been found to be effective in the delayed period of I/R injury.

Influence of ShuJinHuoXue tablets on ischemia reperfusion injury of animals' skeletal muscle

Ischemia-reperfusion (IR) can lead to serious tissue oxidative injury in animals. ShuJinHuoXue tablet (SJHXT) is a Chinese Traditional Medicine which can relax the muscles and stimulate the blood circulation and has been used as a clinical medicine. In the present study, we investigated the effects of SJHXT pretreatment on oxidative injury using an animal model of acute limb IR. Results showed that SJHXT pre-treatment (200, 300 and 400 mg/kg/day) markedly reduced serum endothelin-1 (ET-1), thromboxane B2 (TXB₂) levels and thromboxane B2/6-keto- prostaglandin F1α (TXB₂/6-Keto-PGF(1α)), wet weight/dried weight (W/D) ratio, myeloperoxidase (MPO), creatine kinase (CK), lactate dehydrogenase (LDH) activities, and increased serum nitric oxide (NO), 6-Keto-PGF(1α) levels and NO/ET-1 ratio in the IR+SJHXT groups. In addition, the SJHXT pre-treatment (200, 300 and 400 mg/kg/day) markedly reduced skeletal muscle Ca²⁺, malondialdehyde (MDA) levels, increased Na⁺-K⁺-ATPase, Ca²⁺-Mg²⁺-ATPase, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities. Our results suggest that SJHXT pre-treatment may improve skeletal muscle blood vessel microcirculation, decrease skeletal muscle oxidative injury and enhance antioxidant enzymes activities in IR animals.

Effects of α-MSH on ischemia/reperfusion injury in the rat sciatic nerve

Background:

Ischemia/reperfusion (I/R) causes the production of toxic free radicals and leads to pathological changes in nerve tissue. We investigated the effect of alpha-melanocyte stimulating hormone (α-MSH) in a rat model for sciatic nerve I/R and discuss the possible cytoprotective and antioxidant mechanism of α-MSH against ischemic fiber degeneration.

Methods:

Experiments were performed using 42 adult male Wistar rats. Rats were divided into six experimental groups: control group, ischemia group, I/R groups, and α-MSH treated groups. Ischemia was produced by clamping of the femoral vessels. Immediately after ischemia that lasted 3 h, 75 μg/kg of α-MSH was administered subcutaneously before reperfusion and the tissue malondialdehyde (MDA) level was evaluated as an indicator of lipid peroxidation in groups with different reperfusion periods.

Results:

The reperfusion injury did not begin in the first hour of reperfusion after 3 h of ischemia, and MDA levels increased on the first day of reperfusion. During the first day, blood MDA levels were decreased in the α-MSH group compared to the control group. The tissue from animals pre-treated with α-MSH showed fewer morphological alterations. Myelin breakdown was significantly diminished after treatment with α-MSH, and the ultrastructural features of axons showed remarkable improvement. Two-way analysis of variance was used for comparing three or more groups. When a significant difference existed, the post-hoc multiple-comparison test was applied to demonstrate the differences.

Conclusions:

The results confirm that pre-treatment with α-MSH after ischemia protected the peripheral nerves against I/R injury.

Platelet-mediated vascular dysfunction during acute lung injury

CONTEXT

Platelets have significant roles in initiating and mediating reduced alveolar blood flow, microvascular leak, and ventilation/perfusion mismatch caused by metabolic changes and altered signal transduction caused by ischemia-reperfusion.

OBJECTIVE

This review focuses on platelet mechanisms of vascular dysfunction in the lung and presents a hypothesis for interplay between platelet activation, endothelial damage and fibrinogen. The purpose is to discuss current knowledge regarding mechanisms of platelet-mediated endothelial injury and implications for new strategies to treat vascular dysfunction associated with acute lung injury (ALI).

METHODS

Literature from a number of fields was searched using Medline and Google Scholar.

RESULTS

Activated platelets contribute to redox imbalance through reactive oxygen species production, pro-leak molecules such as PAF and serotonin, and recruitment of inflammatory cytokines and leukocytes to the damaged endothelium.

CONCLUSION

Platelets are a critical component of pulmonary ALI, acting in conjunction with fibrinogen to mediate endothelial damage through multiple signal transduction pathways.

Toll-like receptors in ischaemia and its potential role in the pathophysiology of muscle damage in critical limb ischaemia

Toll-like receptors (TLRs) are key receptors of the innate immune system which are expressed on immune and nonimmune cells. They are activated by both pathogen-associated molecular patterns and endogenous ligands. Activation of TLRs culminates in the release of proinflammatory cytokines, chemokines, and apoptosis. Ischaemia and ischaemia/reperfusion (I/R) injury are associated with significant inflammation and tissue damage. There is emerging evidence to suggest that TLRs are involved in mediating ischaemia-induced damage in several organs. Critical limb ischaemia (CLI) is the most severe form of peripheral arterial disease (PAD) and is associated with skeletal muscle damage and tissue loss; however its pathophysiology is poorly understood. This paper will underline the evidence implicating TLRs in the pathophysiology of cerebral, renal, hepatic, myocardial, and skeletal muscle ischaemia and I/R injury and discuss preliminary data that alludes to the potential role of TLRs in the pathophysiology of skeletal muscle damage in CLI.

Fish oil improves hemodynamic stabilization and inflammation after resuscitation in a rat model of hemorrhagic shock

Background

Hemorrhagic shock followed by resuscitation stimulates an inflammatory response. This study tests the hypothesis that treatment with fish oil will attenuate inflammatory responses and stabilize hemodynamics.

Methods

Male SD rats (n = 48; 250~300 g) were randomly divided into 4 groups: SHAM, hemorrhagic shock (HS), hemorrhagic shock/resuscitation (HS/R) and fish oil (FO). Shock was induced, and a mean arterial pressure (MAP) was maintained at 35 to 40 mmHg for 60 minutes. Resuscitation was carried out by returning half of the shed blood and Ringer's lactate solution to the animal. In FO group, fish oil (0.2 g/Kg) was infused through caudal vena at 30 minutes after shock. Half of each group was killed at 30 minutes and at 4 hours after resuscitation. Then several kinds of inflammation and oxidative stress indicators such as IL-6, MPO and GSH were tested.

Result

FO group required less resuscitative fluid and had higher urinary output at the recovery periods from hemorrhagic shock than HS/R group(p < 0.001). After resuscitation, the MAP of HS/R group markedly declined than FO group (p < 0.001). The inflammatory indexes of FO group were lower than HS group and HS/R group and the same as sham group. But the level of endotoxin in FO group was significantly higher than sham group at 4 hours.

Conclusion

Fish oil pretreatment before fluid resuscitation showed a beneficial effect to the hemodynamic stabilization and inflammation reduction in HS/R rat model.

Evaluation of ischemia-reperfusion liver injury by near-infrared spectroscopy in an experimental swine model: the effect of desferoxamine

INTRODUCTION

Ischemia-reperfusion (I-R) injury has long been regarded a primary factor for the physiological dysfunction that can occur following major liver resection performed under vascular control. The aim of our study was to assess the effect of treatment with desferoxamine (DFO), a potent antioxidative agent, monitoring the I-R injury on a porcine model of major hepatectomy.

MATERIALS AND METHODS

Twelve female pigs were allocated to control (n = 6) and DFO groups (n = 6) and underwent 30 min of liver ischemia, during which a ≥30% hepatectomy was performed, followed by six hours of postoperative monitoring. The DFO group animals were preconditioned with a continuous iv solution of DFO to a total dose of 100 mg/kg during their postoperative period. Liver remnants (≈70% of initial liver volume) were evaluated by means of infrared spectroscopy, serum lactate measurement of the systemic, portal and hepatic vein blood, and by immunohistochemical assessment of apoptosis in consecutive liver biopsies.

RESULTS

DFO group demonstrated considerably faster restoration of tissue oxygenation (92.33% vs. 80%, p < .05) and serum lactate values (1.23 mmol/l vs. 2.27 mmol/l, p < .05). Moreover, apoptosis as estimated by TUNEL and caspase-3 staining was significantly lower in the DFO group (0.06% vs. 1.17% and 1.17% vs. 2%, respectively, p < .05). The severity of the I-R injury showed a linear correlation to the restoration of tissue oxygenation, as estimated by infrared-spectroscopy (r(2) = 0.81, p < .01).

CONCLUSION

Iron chelation with DFO appears to attenuate I-R injury of the liver remnant following hepatectomy, as reflected by faster restoration of tissue oxygenation and lower apoptotic activity.

Heparan sulfate glycosaminoglycan mimetic improves pressure ulcer healing in a rat model of cutaneous ischemia-reperfusion injury

Pressure ulcers are a major clinical problem, with a large burden on healthcare resources. This study evaluated the effects of the heparan sulfate glycosaminoglycan mimetic, OTR4120, on pressure ulceration and healing. Ischemia-reperfusion (I-R) was evoked to induce pressure ulcers by external clamping and then removal of a pair of magnet disks on rat dorsal skin for a single ischemic period of 16 hours. Immediately after magnet removal, rats received an intramuscular injection of OTR4120 weekly for up to 1 month. During the ischemic period, normal skin perfusion was reduced by at least 60% and at least 20-45% reperfused into the ischemic region after compression release. This model caused sustained skin incomplete necrosis for up to 14 days and led to grade 2-3 ulcers. OTR4120 treatment decreased the area of skin incomplete necrosis and degree of ulceration. OTR4120 treatment also reduced inflammation and increased angiogenesis. In OTR4120-treated ulcers, the contents of vascular endothelial growth factor, platelet-derived growth factor, and transforming growth factor beta-1 were increased. Moreover, OTR4120 treatment promoted early expression of alpha-smooth muscle actin and increased collagen biosynthesis. Long-term restoration of wounded tissue biomechanical strength was significantly enhanced after OTR4120 treatment. Taken together, we conclude that OTR4120 treatment reduces pressure ulcer formation and potentiates the internal healing bioavailability.

Leukotriene biosynthesis inhibition ameliorates acute lung injury following hemorrhagic shock in rats

Background

Hemorrhagic shock followed by resuscitation is conceived as an insult frequently induces a systemic inflammatory response syndrome and oxidative stress that results in multiple-organ dysfunction syndrome including acute lung injury. MK-886 is a leukotriene biosynthesis inhibitor exerts an anti inflammatory and antioxidant activity.

Objectives

The objective of present study was to assess the possible protective effect of MK-886 against hemorrhagic shock-induced acute lung injury via interfering with inflammatory and oxidative pathways.

Materials and methods

Eighteen adult Albino rats were assigned to three groups each containing six rats: group I, sham group, rats underwent all surgical instrumentation but neither hemorrhagic shock nor resuscitation was done; group II, Rats underwent hemorrhagic shock (HS) for 1 hr then resuscitated with Ringer's lactate (1 hr) (induced untreated group, HS); group III, HS + MK-886 (0.6 mg/kg i.p. injection 30 min before the induction of HS, and the same dose was repeated just before reperfusion period). At the end of experiment (2 hr after completion of resuscitation), blood samples were collected for measurement of serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The trachea was then isolated and bronchoalveolar lavage fluid (BALF) was carried out for measurement of leukotriene B₄ (LTB₄), leukotriene C₄ (LTC₄) and total protein. The lungs were harvested, excised and the left lung was homogenized for measurement of malondialdehyde (MDA) and reduced glutathione (GSH) and the right lung was fixed in 10% formalin for histological examination.

Results

MK-886 treatment significantly reduced the total lung injury score compared with the HS group (P < 0.05). MK-886 also significantly decreased serum TNF-α & IL-6; lung MDA; BALF LTB₄, LTC₄ & total protein compared with the HS group (P < 0.05). MK-886 treatment significantly prevented the decrease in the lung GSH levels compared with the HS group (P < 0.05).

Conclusions

The results of the present study reveal that MK-886 may ameliorate lung injury in shocked rats via interfering with inflammatory and oxidative pathways implicating the role of leukotrienes in the pathogenesis of hemorrhagic shock-induced lung inflammation.

Microvascular tissue oxygenation and oxidative metabolism changes in the pedicled latissimus dorsi muscle during graded hypoxia: correlation between near infrared and 31P nuclear magnetic resonance spectroscopy

BACKGROUND

In this study, the microvascular tissue oxygenation and oxidative muscle metabolism during graded hypoxia and reoxygenation were examined in a rabbit model by near-infrared (NIR) spectroscopy and correlated with high-energy phosphates measured by (31)P nuclear magnetic resonance (NMR) spectroscopy.

MATERIALS AND METHODS

Graded hypoxia was performed in a New Zealand rabbit model (n = 20, 2.0 ± 0.4 kg) by a stepwise reduction of the fraction of inspired oxygen (FiO(2)) from 0.3 to 0.05 (intervention group versus control group). Recovery and reoxygenation were achieved using FiO(2) of 0.3. A noninvasive NIR spectroscopy sensor and NMR probe was positioned on the surface of the prepared pedicled latissimus dorsi muscle. Microvascular tissue oxygenation (oxyhemoglobin, HbO(2); deoxyhemoglobin, HHb) and redox state of cytochrome oxidase (CytOx) were measured by NIR spectroscopy and correlated with standard values of oxidative muscle metabolism (phosphocreatine, PCr; adenosine triphosphate, ATP) measured by time-resolved (31)P NMR spectroscopy (4.7T).

RESULTS

Significant correlation was found between PCr and HbO(2) (r = 0.85, P < 0.001) and HHb (r = -0.75, P < 0.001). β-ATP levels correlated significantly with CytOx (r = 0.87, P < 0.001).

CONCLUSIONS

The data suggest that changes in high-energy phosphates (PCr- and ATP-levels) correlate closely with microvascular tissue oxygenation (HbO(2), HHb, CytOx) measured by NIR spectroscopy.

[Acute and critical ischemia of the lower limb]

Acute limb arterial occlusion has great clinical significance due to its high mortality and complication rates. Its diagnosis is easy; however staging after long-term occlusions can be very difficult with lack of exact criteria. It is crucial, since reversible stage should undergo revascularization, while with irreversible stage only amputation is curative. Due to occlusion, long-term ischemia occurs, resulting in injury of the muscle fibers and endothelial cells. In case of revascularization the reperfusion causes more damage, than ischemia alone locally and initiates a remote organ injury. The aim of the review is to summarize the knowledge and fact and focus on some exact methods or parameters which can determine the degree of injury. One of these methods is a new approach which is the use of enzyme-histochemical reactions, and could give rapid, precise results even preoperatively regarding tissue viability. Routine clinical application of it is predictable after proper standardization.

Hematological and hemostaseological alterations after warm and cold limb ischemia-reperfusion in a canine model

PURPOSE

Acute ischemia-reperfusion (I/R) of extremities means serious challenge in the clinical practice. Furthermore, the issue of preventive cooling is still controversial. In this canine model we investigated whether limb I/R -with or without cooling- has an influence on hematological and hemostaseological factors.

METHODS

Femoral vessels were exposed and clamped for 3 hours. After release the clamps, 4-hour reperfusion was secured. The same procedures with cooling using ice bags, as well as warm and cold sham-operations were performed. Before operations, from the excluded limb by the end of ischemia, during the reperfusion, and for 5 postoperative days afterwards blood samples were collected for testing hematological and blood coagulation parameters.

RESULTS

After I/R activated partial thromboplastin time was elongated on 2nd-4th postoperative days. The highest values were on the 2nd day in cold I/R group, accompanied by increased prothrombin time values. The hematological parameters and fibrinogen level showed non-specific changes. In excluded ischemic limb the blood composition showed controversial data. Cold ischemia induced larger alterations, however platelet count, hematocrit changed more expressly in warm ischemia.

CONCLUSION

These results indicate the risk of coagulopathy following limb I/R on early post-eventually days, which risk is higher in the case of cold I/R.

Donor pretreatment with tetrahydrobiopterin saves pancreatic isografts from ischemia reperfusion injury in a mouse model

Depletion of the nitric oxide synthase cofactor tetrahydrobiopterin (H4B) during ischemia and reperfusion is associated with severe graft pancreatitis. Since clinically feasible approaches to prevent ischemia reperfusion injury (IRI) by H4B-substitution are missing we investigated its therapeutic potential in a murine pancreas transplantation model using different treatment regimens. Grafts were subjected to 16 h cold ischemia time (CIT) and different treatment regimens: no treatment, 160 μM H4B to perfusion solution, H4B 50 mg/kg prior to reperfusion and H4B 50 mg/kg before recovery of organs. Nontransplanted animals served as controls. Recipient survival and endocrine graft function were assessed. Graft microcirculation was analyzed 2 h after reperfusion by intravital fluorescence microscopy. Parenchymal damage was assessed by histology and nitrotyrosine immunohistochemistry, H4B tissue levels by high pressure liquid chromatography (HPLC). Compared to nontransplanted controls prolonged CIT resulted in significant microcirculatory deterioration. Different efficacy according to route and timing of administration could be observed. Only donor pretreatment with H4B resulted in almost completely abrogated IRI-related damage showing graft microcirculation comparable to nontransplanted controls and restored intragraft H4B levels, resulting in significant reduction of parenchymal damage (p < 0.002) and improved survival and endocrine function (p = 0.0002 each). H4B donor pretreatment abrogates ischemia-induced parenchymal damage and represents a promising strategy to prevent IRI following pancreas transplantation.

Role of free radicals in liver diseases

Reactive oxygen and nitrogen species (ROS and RNS) are produced by metabolism of normal cells. However, in liver diseases, redox is increased thereby damaging the hepatic tissue; the capability of ethanol to increase both ROS/RNS and peroxidation of lipids, DNA, and proteins was demonstrated in a variety of systems, cells, and species, including humans. ROS/RNS can activate hepatic stellate cells, which are characterized by the enhanced production of extracellular matrix and accelerated proliferation. Cross-talk between parenchymal and nonparenchymal cells is one of the most important events in liver injury and fibrogenesis; ROS play an important role in fibrogenesis throughout increasing platelet-derived growth factor. Most hepatocellular carcinomas occur in cirrhotic livers, and the common mechanism for hepatocarcinogenesis is chronic inflammation associated with severe oxidative stress; other risk factors are dietary aflatoxin B(1) consumption, cigarette smoking, and heavy drinking. Ischemia-reperfusion injury affects directly on hepatocyte viability, particularly during transplantation and hepatic surgery; ischemia activates Kupffer cells which are the main source of ROS during the reperfusion period. The toxic action mechanism of paracetamol is focused on metabolic activation of the drug, depletion of glutathione, and covalent binding of the reactive metabolite N-acetyl-p-benzoquinone imine to cellular proteins as the main cause of hepatic cell death; intracellular steps critical for cell death include mitochondrial dysfunction and, importantly, the formation of ROS and peroxynitrite. Infection with hepatitis C is associated with increased levels of ROS/RNS and decreased antioxidant levels. As a consequence, antioxidants have been proposed as an adjunct therapy for various liver diseases.

Epicardial measurement of alterations in extracellular pH and electrolytes during ischemia and reperfusion in cardiac surgery

Simultaneous measurements of extracellular pH, potassium (K(+)), and calcium (Ca(2+)) activity might be indicative of myocardium vitality or ischemia. Ten consecutive patients undergoing elective coronary artery bypass grafting were studied. Epicardial extracellular pH, potassium, and calcium were measured by a miniaturized disposable multi-sensor probe. Blood gases and electrolytes were derived with measurements of arterial and mixed venous blood samples at intervals during surgery. The mean epicardial baseline levels for pH in all patients were 8.04+/-0.22 arbitrary units (AU) for the right ventricle (RV) and 8.03+/-0.21 AU for the left ventricle (LV); for Ca(2+) 0.23+/-0.07 mmol/l (RV) and 0.20+/-0.10 mmol/l (LV); and for K(+) 4.54+/-1.51 mmol/l (RV) and 4.38+/-0.57 mmol/l (LV). Before ischemia, epicardial pH was moderately (p<0.05), and K(+), and Ca(2+) were closely correlated (p<0.001) with blood values. During reperfusion, epicardial measurements were weakly correlated (p<0.001) with blood values for pH, venous K(+) and Ca(2+), but moderately correlated with arterial K(+) and Ca(2+) (p<0.01). The measurements indicated intraoperative episodes of ischemia and reperfusion with reproducible trends of extracellular pH, K(+), and Ca(2+), which results in electrolyte patterns applicable for detecting inadequate myocardial protection during cardiac surgery in patients.

Allopurinol Prevents Erythrocyte Deformability Impairing but Not the Hematological Alterations After Limb Ischemia–Reperfusion in Rats

The measurement of red blood cell deformability provides a possible method for detecting the effect of ischemia-reperfusion on erythrocytes. In our study the effect of 1-h ischemia-reperfusion with or without allopurinol pretreatment on hematological parameters and red blood cell deformability was investigated in a follow-up experiment of 26 male CD outbred rats that were subjected to unilateral hind-limb ischemia by microvascular clips on femoral vessels for 1 h (IR, n = 6), some rats received allopurinol pretreatment under the same conditions (50 mg/kg, AP + IR, n = 8), others were subjected to sham operation (n = 6), and the rest of animals served as control (n = 6). Measurement of erythrocyte deformability using a bulk filtrometer with special setting of cell suspension hematocrit (1%), and determination of hematological parameters were performed daily for one week. In the IR group, relative cell transit time increased significantly on postoperative days 1 and 2, which was not observed in the other groups. Settings for the measurement of erythrocyte deformability by reducing the blood sample volume gave the possibility of monitoring the resulting changes in rats. Mean corpuscular volume and hemoglobin, platelet count, and platelet volume were higher in the IR and AP + IR groups than in the other groups. In summary, short-term ischemia and reperfusion induced lower red blood cell deformability in the early postoperative period, which could be prevented by allopurinol pretreatment.

Nitric oxide mechanism of protection in ischemia and reperfusion injury

In 1992 nitric oxide (NO) was declared molecule of the year by Science magazine, and ever since research on this molecule continues to increase. Following this award, NO was shown to be a mediator/protector of ischemia and reperfusion injury in many organs, such as the heart, liver, lungs, and kidneys. Controversy has existed concerning the actual protective effects of NO. However, literature from the past 15 years seems to reinforce the consensus that NO is indeed protective. Some of the protective actions of NO in ischemia and reperfusion are due to its potential as an antioxidant and anti-inflammatory agent, along with its beneficial effects on cell signaling and inhibition of nuclear proteins, such as NF-kappa B and AP-1. New therapeutic potentials for this drug are also continuously emerging. Exogenous NO and endogenous NO may both play protective roles during ischemia and reperfusion injury. Sodium nitroprusside and nitroglycerin have been used clinically with much success; though only recently have they been tested and proven effective in attenuating some of the injuries associated with ischemia and reperfusion. NO inhalation has, in the past, mostly been used for its pulmonary effects, but has also recently been shown to be protective in other organs. The potential of NO in the treatment of ischemic disease is only just being realized. Elucidation of the mechanism by which NO exerts its protective effects needs further investigation. Therefore, this paper will focus on the mechanistic actions of NO in ischemia and reperfusion injury, along with the compound's potential therapeutic benefits.

Caffeic acid phenethyl ester prevents ovary ischemia/reperfusion injury in rabbits

Protective effect of caffeic acid phenethyl ester (CAPE) on ovary ischemia/reperfusion (IR) injury was investigated in this study. Twenty four New Zealand rabbits were divided into 4 groups as follows: group S served as sham. Group C was intraperitoneally injected with CAPE (8.5mg/kg). In groups E+IR and C+IR, 1% ethanol and CAPE was given intraperitoneally before torsion, respectively. Then, the ovaries were subjected to IR in both groups. Ovary reduced glutathione (GSH) level and glutathione peroxidase (GSH-Px) activity in group E+IR were significantly reduced compared to that of group S. GSH level and GSH-Px activity was significantly increased in group C+I/R. Thiobarbituric acid reactive substances (TBARS) and catalase (CAT) activity in group E+I/R was significantly higher than in group S. CAT activity was decreased to normal levels by CAPE treatment in group C+I/R, while TBARS in group C+IR was significantly reduced compared to that of E+IR. According to histopathological examination, severe congestion, hemorrhage, edema and leukocyte infiltration were observed in E+I/R group. CAPE prominently reduced degenerative effects of IR injury thus it alleviates free radical damage. In conclusion, CAPE which is able to prevent IR-induced injury in the ovaries may be of therapeutic value before the surgical correction.

Anchoring fusion thrombomodulin to the endothelial lumen protects against injury-induced lung thrombosis and inflammation

RATIONALE

Endothelial thrombomodulin (TM) regulates thrombosis and inflammation. Diverse forms of pulmonary and vascular injury are accompanied by down-regulation of TM, which aggravates tissue injury. We postulated that anchoring TM to the endothelial surface would restore its protective functions.

OBJECTIVES

To design an effective and safe strategy to treat pulmonary thrombotic and inflammatory injury.

METHODS

We synthesized a fusion protein, designated scFv/TM, by linking the extracellular domain of mouse TM to a single-chain variable fragment of an antibody to platelet endothelial cell adhesion molecule-1 (PECAM-1). The targeting and protective functions of scFv/TM were tested in mouse models of lung ischemia-reperfusion and acute lung injury (ALI) caused by intratracheal endotoxin and hyperoxia, both of which caused approximately 50% reduction in the endogenous expression of TM.

MEASUREMENTS AND MAIN RESULTS

Biochemical assays showed that scFv/TM accelerated protein C activation by thrombin and bound mouse PECAM-1 and cytokine high mobility group-B1. After intravenous injection, scFv/TM preferentially accumulated in the mouse pulmonary vasculature. In a lung model of ischemia-reperfusion injury, scFv/TM attenuated elevation of early growth response-1, inhibited pulmonary deposition of fibrin and leukocyte infiltration, and preserved blood oxygenation more effectively than soluble TM. In an ALI model, scFv/TM, but not soluble TM, suppressed activation of nuclear factor-kappaB, inflammation and edema in the lung and reduced mortality without causing hemorrhage.

CONCLUSIONS

Targeting TM to the endothelium using an scFv anchor enhances its antithrombotic and antiinflammatory effectiveness in models of ALI.