Remote ischaemic preconditioning of the hind limb reduces experimental liver warm ischaemia-reperfusion injury

BACKGROUND: Direct ischaemic preconditioning of the liver reduces ischaemia-reperfusion injury (IRI). Remote ischaemic preconditioning (RIPC) of a limb has been shown to reduce IRI to the heart. This study determined the effect of brief remote ischaemia to the limb in reducing early liver warm IRI. METHODS: Twenty-eight male rabbits were allocated to four groups: sham operated, RIPC alone, IRI alone, and RIPC plus IRI. RIPC was induced in the leg with a tourniquet, before liver IRI, by three alternate cycles of 10 min ischaemia followed by 10 min reperfusion. Liver IRI was produced by total inflow occlusion for 25 min. Markers of liver injury and systemic and hepatic haemodynamics were measured for 2 h after reperfusion. RESULTS: At 2 h, IRI alone was associated with increased serum levels of aminotransferases, and reduced mean arterial blood pressure, hepatic blood flow and peripheral oxygen saturation. There was significant improvement in these variables in animals that had RIPC before liver IRI, and hepatic venous nitrate/nitrite levels were also significantly higher. CONCLUSION: In this experimental model RIPC appeared to reduce liver IRI.     

小肠远端缺血预处理对大鼠肝脏热缺血再灌注损伤的保护作用

目的 观察小肠远端缺血预处理对大鼠肝脏热缺血再灌注损伤的保护作用.方法 将40只Wistar大鼠被随机分为4组:假手术组(Sham)、单纯远端缺血预处理组(RJPC)、单纯缺血再灌注组(IR)和远端缺血预处理+缺血再灌注组(RIPC+IR).远端缺血预处理方式采用于小肠系膜根部游离动脉血管并夹闭5 min后开放5 min,反复3次.缺血再灌注模型采用于肝蒂阻断肝脏供血45 min,阻断范围占整个肝脏的70%,开放复流3 h.检测血液中谷丙转氨酶(ALT)、乳酸脱氢酶(LDH)、一氧化氮(NO)和内皮素(ET)、肝脏苏木素-伊红(HE)病理、心血管指标.结果 复流3 h后,RIPC+IR组的ALT、LDH、心血管指标[平均动脉血压(MAP)、外周血氧饱和度(SaO2)]为(434.26±133.42)U/L、(2536±181)U/L、(83.1±7.3)mm Hg(1 mm Hg＝0.133 kPa)和(97.4±0.5)%,明显好于IR组(953.64±114.12)U/L、(5734±296)U/L、(67.1±7.4)mm Hg和(93.1±0.6)%(P<0.05).RJPC+IR组肝脏HE病理改变程度比IR组小.门静脉中IR组血清NO浓度(15.54±2.34)μmoL/L低于RIPC+IR组(18.10±1.82)μmol/L(P<0.05),外周血中,IR组血浆ET浓度(672.4±63.1)ng/L高于RIPC+IR组(451.7±63.6)ng/L(P<0.05),门静脉中IR组血清ET浓度(612.5±48.2)ng/L高于RIPC+IR组(401.5±51.2)ng/L(P<0.05).结论 小肠RIPC可以减轻肝脏缺血再灌注损伤,具有简便、易操作的特点,NO及ET可能在其中发挥了重要作用.     

N-acetylcysteine attenuates kidney injury in rats subjected to renal ischaemia-reperfusion.

BACKGROUND: The aim of the present study is to examine the effects of N-acetylcysteine (NAC), a thiol-containing anti-oxidant, on renal function and morphology, and biomarkers of oxidative stress, in rats subjected to renal ischaemia-reperfusion (IR). METHODS: Sprague-Dawley rats underwent unilateral nephrectomy and either contralateral renal IR (40 min of renal arterial clamping), or sham manipulation. Treatment groups were: (1) IR-Saline, (2) IR-NAC, (3) Sham-Saline and (4) Sham-NAC. The N-acetylcysteine was administered in a dose of 200 mg/kg intraperitoneally at 24, 12 and 2 h before, and 24, 48 and 72 h after, renal IR. Plasma creatinine was measured on days 1, 3 and 7 after IR, and kidney histology was assessed on day 7. In separate groups of animals we measured renal levels of the anti-oxidant glutathione, markers of systemic oxidative stress (plasma ascorbyl radical, urinary 8-iso-prostaglandin F2alpha), and glomerular filtration rate (GFR) by 51Cr-EDTA clearance, on day 1 after renal IR. RESULTS: Treatment with NAC ameliorated the decline in GFR and reduced hyperkalaemia on day 1 (P<0.05), lowered plasma creatinine levels on days 1 and 3 (P<0.05), and decreased renal interstitial inflammation on day 7 (P<0.05), after renal IR. Kidney glutathione levels decreased significantly in group IR-Saline in response to IR (P<0.05), but were completely repleted in group IR-NAC. Groups with renal IR injury and acute renal failure showed increased plasma ascorbyl radical levels, and elevated urinary 8-iso-prostaglandin F2alpha excretion, compared with sham (P<0.05). N-acetylcysteine treatment reduced plasma ascorbyl concentrations 24 h after renal IR (P<0.05), but had no effect on the rate of urinary 8-iso-prostaglandin F2alpha excretion. CONCLUSIONS: N-acetylcysteine improves kidney function, and reduces renal interstitial inflammation, in rats subjected to renal IR. These effects were associated with increased renal glutathione levels, and decreased plasma ascorbyl concentrations, suggesting that NAC attenuates renal and systemic oxidative stress in this model.     

Biphasic role for nitric oxide in experimental renal warm ischaemia-reperfusion injury.

BACKGROUND: Whilst nitric oxide has a clearly defined role in renal haemostasis, debate continues over its pathophysiology. This study investigated the function of nitric oxide in a model of renal warm ischaemia-reperfusion injury. METHODS: Rats underwent bilateral renal warm ischaemia (45 min) after pretreatment with nitric oxide donors, nitric oxide synthase (NOS) inhibitors or saline (control). Following reperfusion (20 min) a unilateral nephrectomy was performed to measure renal nitric oxide (as nitroxides) and oxidative DNA and protein damage. Renal function was measured on days 2 and 7 before terminal nephrectomy for analysis and morphology. RESULTS: The increase in renal nitric oxide level seen early in reperfusion (20 min) (P < 0.01) was prevented by inhibition of constitutive (cNOS) but not inducible (iNOS) NOS. The increase in oxidative damage (P < 0.01) was exacerbated by nitric oxide donors (P < 0.01) but ameliorated by NOS inhibition (P < 0.01). Control nitric oxide remained increased through to day 7 (P < 0.01) but was reduced by nitric oxide donors and cNOS inhibitors (P < 0.05). Oxidative damage returned towards normal in the control group, whereas both DNA and protein damage persisted following NOS inhibition (P < 0.01). CONCLUSION: Inhibition of the postischaemic increase in the level of nitric oxide was associated with an early decrease in, but eventual exacerbation of, oxidative damage. This suggests the prolonged increase in renal nitric oxide concentration was cytoprotective overall.     

Effect of low-dose N-acetyl-cysteine infusion on tourniquet-induced ischaemia-reperfusion injury in arthroscopic knee surgery

BACKGROUND: Temporary occlusion of blood flow is used during arthroscopic knee surgery in order to provide a bloodless surgical field. The resulting ischaemia-reperfusion causes lipid peroxidation, which contributes to tissue injury. The aim of the study was to investigate the effect of low-dose n-acetyl cysteine (NAC) infusion on oxidative stress by determining malondialdehyde (MDA) levels during arthroscopic knee surgery. METHODS: Thirty patients, ASA I - II, undergoing arthroscopic knee debridement under a tourniquet were divided into NAC and control groups. Anaesthesia was induced with propofol, fentanyl and vecuronium bromide and maintained with desflurane in an equal parts O(2)-N(2)O mixture. In the NAC group, an infusion of NAC, 5 mg kg(-1).h(-1), was started after intubation, and continued until extubation. An equal volume of saline was infused to the control group. Duration of ischaemia, anaesthesia time, total dose of NAC infused were also recorded. Venous blood and synovial membrane tissue samples were obtained 10 min after the onset of NAC infusion but before tourniquet inflation (t1), after 30 min of ischaemia (t2), and after 5 min of reperfusion following tourniquet release (t3). RESULTS: Plasma MDA levels were significantly lower in the NAC group on reperfusion. There were no differences between the groups in tissue MDA levels at ischaemia and reperfusion times. CONCLUSION: Low-dose n-acetyl cysteine infusion attenuates lipid peroxidation and ischaemia-reperfusion injury in arthroscopic knee surgery requiring tourniquet application.     

Murine renal ischaemia-reperfusion injury

SUMMARY:   Ischaemia/reperfusion is a major cause of acute kidney injury in native and transplant kidneys and is associated with significant morbidity and mortality. Murine models of renal ischaemia/reperfusion injury have great potential to improve understanding of the underlying processes and are an important focus of ongoing research into therapeutic and preventative strategies. Like all experimental models, murine models of renal ischaemia/reperfusion are prone to significant variability and results may be influenced by a number of technical and design factors. In this article we review the factors that may influence experimental results and provide a guide to conducting reproducible experiments in murine renal ischaemia/reperfusion.     

N-acetylcysteine reduces lung reperfusion injury after deep hypothermia and total circulatory arrest

OBJECTIVE: We hypothesized that the use of N-acetylcysteine would ameliorate the lung reperfusion injury observed after deep hypothermia and total circulatory arrest (DHTSA). METHODS: Experiments were carried out on 12 adult mongrel dogs of either sex weighing 25 to 30 kg. The animals were randomly divided into two groups of six animals each. All animals were cooled to an esophageal temperature of 15 degrees C during 30 minutes and underwent 60 minutes of DHTSA, followed by the reinstitution of cardiopulmonary bypass (CPB) and rewarming. Before rewarming, while 100 mL physiologic saline solution was added into the pump in group I, 50 mg/kg N-acetylcysteine(NAC) was given in group II. Heart rate, mean arterial pressure, pulmonary arterial pressure, left atrial pressure, central venous pressure, and cardiac output were recorded. To measure lung tissue malondialdehyde (MDA), water content and polymorphonuclear leukocytes (PMNs) count, lung tissue samples were taken before CPB and after weaning CPB. In addition, alveolar-arterial oxygen difference (AaDO(2))()for tissue oxygenation was calculated by obtaining arterial blood gas samples. Dynamic lung compliance (DLC) was measured before CPB and after CPB. RESULTS: MDA levels before CPB of 44.2 +/- 3.9 nmol/g tissue rose to 76.6 +/- 5.6 nmol/g tissue after weaning CPB in group I (p = 0.004). In group II also, the MDA levels increased from 43.5 +/- 4.2 to 57.4 +/- 5.6 nmol MDA/g tissue after weaning CPB (p = 0.006). The MDA increase in group II after CPB was found to be significantly lower than in group I (p = 0.006). The wet-to-dry lung weight ratio in the NAC group was 5.1 +/- 0.2, significantly less than in the control group (5.9 +/- 0.3), (p = 0.004). AaDO(2) significantly increased in the group I and II (p = 0.002 and p = 0.002, respectively); this elevation in group I was significant than in group II (p = 0.044). In histopathological examination, it was observed that neutrophil counts in the lung parenchyma rose significantly after CPB in both groups (p < 0.001). The increase in group I was significantly larger than group II (p < 0.001). CONCLUSIONS: Results represented in our study indicate that addition of NAC into the pump after DHTSA can reduce lung reperfusion injury.     

Attenuation of ischemic injury by N-acetylcysteine preconditioning of the liver

BACKGROUND: Numerous previous studies have established the hepatoprotective properties of N-acetylcysteine (NAC). The present study was designed to investigate the effects of NAC on a warm hepatic ischemia-reperfusion rat model with a focus on the role of cAMP. MATERIALS AND METHODS: Fifty-six male Wistar rats were allocated randomly into the control group (n = 28) or the study group (group NAC, n = 28). Group NAC animals received an intravenous bolus dose of 0.3 mg/g NAC, whereas control animals were given an equal volume of normal saline. Subsequently, 60-min partial liver ischemia was induced by occlusion of blood inflow to the left and middle liver lobes. Aspartate aminotransferase, alanine aminotransferase, and alpha-glutathione S-transferase levels, platelet aggregation, and ischemic tissue cyclic adenosine 5-monophosphate (cAMP) levels were examined at 30, 60, and 120 min after reperfusion. Parts of the ischemic liver were sampled at the same time-points. Measurements were obtained from seven animals at each time point. RESULTS: The administration of NAC resulted in lower levels of aspartate aminotransferase, alanine aminotransferase, and alpha-glutathione S-transferase, decreased platelet aggregation, and increased levels of ischemic tissue cAMP at all time points after reperfusion. Histologically, fewer necrotic changes were observed in the NAC group at 60 and 120 min after reperfusion. All differences were statistically significant (P < 0.05). CONCLUSIONS: In the present study, NAC seems to attenuate hepatic ischemia-reperfusion damage, as demonstrated by liver function tests and liver histology. The effects of NAC appear to be mediated by the decrease in platelet aggregation and increase in the levels of cAMP observed in ischemic liver tissue.     

Nebivolol reduces experimentally induced warm renal ischemia reperfusion injury in rats

Ischemia/reperfusion injury, which is commonly seen in the field of renal surgery or transplantation, is a major cause of acute renal failure. The objective of the present study was to examine the role of nebivolol in modulating peroxynitrite species-induced inflammation and apoptosis after renal warm ischemia/reperfusion injury in rats. The present study was designed to investigate the effects of nebivolol on the renal warm ischemia/reperfusion injury in rats treated with the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester. After right nephrectomy, nebivolol was administered for 15 days. On the 16(th) day, ischemia was induced in contra lateral kidney for 45 min, followed by reperfusion for 24 hr. Renal function, inflammation, and apoptosis were estimated at the end of 24 hr reperfusion. Nebivolol improved the renal dysfunction and reduced inflammation and apoptosis after renal ischemia/reperfusion injury. In conclusion, nebivolol shows potent anti-apoptotic and anti-inflammatory properties due to its NO-releasing property. These findings may have major implications in the treatment of human ischemic acute renal failure.     

N-乙酰半胱氨酸对大鼠胆道梗阻肝功能损伤的保护作用及机制研究

目的 探讨N-乙酰半胱氨酸(N-acetylcysteine,NAC)对大鼠胆道梗阻所致肝功能损伤的保护作用及其机制。方法Wistar大鼠72只随机均分成3组：(1)胆道结扎+NAC组(DBL+NAC,n=24)：开腹结扎并切断胆总管,建模成功后经腹腔注射NAC（150 mg·kg-1·d-1）连续注射7 d;(2)胆道结扎组（DBL组,n=24）;(3)假手术组(SO组,n=24)：仅行开腹游离胆总管不予结扎和切断。建模成功后1、3、5、7d每组分别活杀6只大鼠,取静脉血及肝组织,检测肝功能、血浆肿瘤坏死因子α(TNF-α)在各时相点的变化并采用Griess法检测一氧化氮(NO)产生情况。结果 在DBL组、DBL+ NAC组谷-草转氨酶(AST)、血清谷丙转氨酶(ALT)、总胆红素(TBIL)、直接胆红素(DBIL)均随胆道梗阻时间延长而升高,但DBL组AST、ALT在各时间点均较DBL+NAC组明显升高(P＜0.05),而TBIL、DBIL在这两组间无明显差异(P＞0.05)。DBL组和DBL+ NAC组TNF-α、NO浓度变化也随梗阻时间延长而升高,但DBL组较DBL+ NAC组TNF-α、NO浓度升高更明显(P＜0.05)。结论N-乙酰半胱氨酸能有效改善胆道梗阻所致肝损害,并有可能是通过下调肝组织中TNF-α、NO的表达这一途径实现的。     

Continuous insulin infusion reduces infectious complications in diabetics following coronary surgery

BACKGROUND: This study was undertaken to evaluate the effects of a continuous insulin infusion protocol on postoperative infection and mortality. METHODS: Patients who underwent coronary artery bypass grafting from January 1997 until December 1998 were included in this study (n = 761). A continuous insulin drip protocol (IDP) designed to titrate blood sugar levels to 120-160 mg/dL in the immediate postoperative period was instituted in 1998. Comparisons of diabetic and nondiabetic data before and after initiation of the IDP were made. RESULTS: Of the 761 patients who underwent coronary revascularization, diabetics accounted for 32%. There was no significant difference in age, gender, diabetic status, urgency of operation, or operative time between 1997 and 1998 diabetics and nondiabetics. Overall, wound infections occurred in 3% (23/761) of patients. In 1997, the infection rate was significantly higher in diabetics than nondiabetics (p = 0.0007). After initiation of the IDP in 1998, the infection rate for the diabetic population was reduced to that of the nondiabetic population. There was no significant difference in the mortality rate between 1997 diabetics (4%) and 1998 diabetics (5%) (p = 0.5759) or in the length of stay for 1997 diabetics versus nondiabetics (p = 0.1906). There were no mortalities among patients with wound infections. CONCLUSION: Initiation of the IDP and the subsequent tight control of blood sugars in the immediate postoperative period proved to reduce the incidence of wound infection in the diabetic population. There was no significant difference in the mortality rate or length of hospitalization.     

Mechanisms of reperfusion injury after warm ischemia of the liver

The review highlights recent advances in our understanding of basic mechanisms of reperfusion injury after warm hepatic ischemia. Kupffer cells play a central role as the initial cytotoxic cell type and as a source of many proinflammatory mediators. Subsequently, neutrophils are activated and recruited into the liver. Factors and conditions are outlined that determine whether neutrophils undergo apoptosis without causing damage or migrate out of the sinusoids and attack parenchymal cells. In addition to the inevitable inflammatory response during reperfusion, microcirculatory perfusion failure, due to an imbalance between the actions of vasodilators and vasoconstrictors, also has a serious impact on reperfusion injury. A better understanding of the basic pathophysiology will reveal potential targets for therapeutic interventions and will show us how to avoid risk factors that may aggravate reperfusion injury. Received for publication on March 30, 1998; accepted on March 31, 1998     

Hyperglycaemia and renal ischaemia-reperfusion injury.

Introduction Hyperglycaemia is most probably a contributing factor in thedevelopment of ischaemic acute renal failure (ARF) in many patients.Both clinical and experimental data suggest that hyperglycaemiaincreases the risk of ARF [1–3]. Hyperglycaemia also worsensthe outcome in renal transplantation [4,5]. Conversely, ischaemia–reperfusion(I/R) combined with hyperglycaemia could also be important inthe development of diabetic nephropathy. Studies in our laboratoryshow that a brief renal ischaemia results in a progressive injuryleading to end-stage renal failure in diabetic animals [6,7].The mechanisms behind this increased sensitivity to renal I/Rduring hyperglycaemia are still poorly understood. Experimental findings An increased susceptibility to renal I/R injury in diabeticrats has been shown in several studies [1,3,6–9]. Furthermore,non-diabetic rats and dogs are more vulnerable     

Kidney ischaemia-reperfusion injury and polyribosome structure

BACKGROUND: Inhibition of protein synthesis and polyribosome disaggregation are the early events in cell injury provoked by various pathogenic mechanisms, including energy depletion. Polyribosome disaggregation might be expected to occur during ischaemia-reperfusion injury due to ischaemic energy depletion, but also due to detrimental effects of reactive oxygen species on various macromolecules and cellular structures. METHODS: Mouse kidney ischaemia-reperfusion injury was provoked by temporary clamping of the renal artery. The polyribosome sedimentation pattern was analyzed by sucrose density centrifugation of kidney postmitochondrial supernatant. RESULTS AND CONCLUSIONS: Ischaemia for 5 min in the mouse kidney provoked polyribosome disaggregation and an increase of monomer ribosome fraction which was augmented during 10-360 min of reperfusion. Recovery of polyribosome aggregates appeared between 6 and 24 h of reperfusion. Cycloheximide pretreatment prevented only polyribosome disaggregation caused by ischaemia and not that caused by reperfusion. This indicates different mechanisms of polyribosome disaggregation during ischaemia and reperfusion. It probably occurs in the former due to inhibition of initiation of translation, resulting in accumulation of unprogrammed monomer ribosomes, and in the latter due to the splitting of mRNA and breakdown of polyribosomes. Reperfusion did not increase ribonuclease activity in kidney cytosol, but increased the tissue concentration of malonaldehyde, indicating an augmentation in oxygen free radical generation. Possibly these may have caused a non-enzymatic breakdown of polyribosomes. However, pretreatment with allopurinol did not prevent polyribosome breakdown during ischaemia-reperfusion injury.     

Endoglin regulates renal ischaemia-reperfusion injury.

BACKGROUND: Renal ischaemia-reperfusion (I-R) can cause acute tubular necrosis and chronic renal deterioration. Endoglin, an accessory receptor for Transforming Growth Factor-beta1 (TGF-beta1), is expressed on activated endothelium during macrophage maturation and implicated in the control of fibrosis, angiogenesis and inflammation. METHODS: Endoglin expression was monitored over 14 days after renal I-R in rats. As endoglin-null mice are not viable, the role of endoglin in I-R was studied by comparing renal I-R injury in haploinsufficient mice (Eng(+/-)) and their wild-type littermates (Eng(+/+)). Renal function, morphology and molecular markers of acute renal injury and inflammation were compared. RESULTS: Endoglin mRNA up-regulation in the post-ischaemic kidneys of rats occurred at 12 h after I-R; endoglin protein levels were elevated throughout the study period. Expression was initially localized to the vascular endothelium, then extended to fibrotic and inflamed areas of the interstitium. Two days after I-R, plasma creatinine elevation and acute tubular necrosis were less marked in Eng(+/-) than in Eng(+/+) mice. Significant up-regulation of endoglin protein was found only in the post-ischaemic kidneys of Eng(+/+) mice and coincided with an increased mRNA expression of the TGF-beta1 and collagen IV (alpha1) chain genes. Significant increases in vascular cell adhesion molecule-1 (VCAM-1) and inducible nitric oxide synthase (iNOS) expression, nitrosative stress, myeloperoxidase activity and CD68 staining for macrophages were evident in post-ischaemic kidneys of Eng(+/+), but not Eng(+/-) mice, suggesting that impaired endothelial activation and macrophage maturation may account for the reduced injury in post-ischaemic kidneys of Eng(+/-) mice. CONCLUSIONS: Endoglin is up-regulated in the post-ischaemic kidney and endoglin-haploinsufficient mice are protected from renal I-R injury. Endoglin may play a primary role in promoting inflammatory responses following renal I-R.