一氧化氮在缺血预处理保护大鼠移植肝脏再灌注损伤中的作用

目的　探讨一氧化氮 (NO)在缺血预处理 (IP)保护大鼠移植肝脏缺血再灌注损伤中的作用。方法　采用SD大鼠原位肝移植动物模型 ,供肝冷保存时间为 10 0min ,无肝期 2 5min。12 8只大鼠随机分成 4组 (n =32 ) :A组 (对照组 )、B组 (IP组 )、C组 [腺苷 (Ade)组 ]、D组 [NO合成抑制剂N L 精氨酸甲基脂 (NAME)组 ]。其中各组的半数用于观察存活率 ,另一半用于移植肝脏再灌注 2h后取血及肝脏检测。结果　IP组和Ade组的 1周存活率、胆汁分泌量、抗氧化酶活力及血清NO水平均明显高于对照组 (P <0 .0 5 ) ,血清丙氨酸氨基转移酶 (ALT)、肿瘤坏死因子(TNF)及肝组织中的过氧化物含量均明显低于对照组 (P <0 .0 5 )。肝组织损伤以窦状内皮细胞为主 ,并且是以凋亡的方式发生死亡 ,IP组和Ade组窦状内皮细胞损伤明显轻于对照组 (P <0 .0 0 1) ;NAME组的各种观察结果与对照组相近 (P >0 .0 5 )。结论　IP能够通过增加NO的合成来减轻再灌注早期窦状内皮细胞所受到的损伤 ,改善微循环 ,提高移植肝脏的功能。     

Interaction of eicosanoids and nitric oxide in renal reperfusion injury.

BACKGROUND: Both the eicosanoids and nitric oxide are known to play an important role in the pathogenesis of postischemic injury. Recent evidence has suggested that the generation of each may affect the other via a feedback loop. This was investigated in an experimental model of renal warm ischemia reperfusion injury. METHODS: Rats underwent bilateral renal warm ischemia (15-60 min) then reperfusion (20 or 80 min) followed by a unilateral nephrectomy to measure renal nitric oxide (as nitroxides) and eicosanoids. Renal function was measured on days 2 and 7 prior to terminal nephrectomy for tissue analysis. RESULTS: Vasodilator eicosanoids (6-KPGF1alpha and PGE2) fell on reperfusion in line with the duration of warm ischemia with a concomitant rise in the vasoconstrictor TxA2. The ratio of vasodilator to vasoconstrictor eicosanoids fell from 8.22 (2.3) in the control to 0.82 (0.1) in the 60-min warm ischemia group (P<0.01). Renal levels of nitroxides rose on reperfusion demonstrating an inverse correlation with the eicosanoid ratio (r2=0.86). Renal function was impaired at both day 2 and day 7 and showed a positive correlation with the eicosanoid ratio (r2=0.67 and 0.62, respectively). CONCLUSIONS: Renal warm ischemic injury is associated with a progressive fall in the ratio of vasodilator-to-vasoconstrictor eicosanoids from early in reperfusion through to day seven although nitric oxide was elevated throughout the same period. There was no evidence of coinduction of nitric oxide synthase and cyclooxygenase in this model.     

Inhibition of nitric oxide synthase reduces renal ischemia/reperfusion injury

BACKGROUND: The role of nitric oxide (NO) production because of inducible nitric oxide synthase (iNOS) in the pathogenesis of renal ischemia/reperfusion (I/R) injury is unclear. In this study the roles of both iNOS and NO were characterized in a rat model of renal I/R injury. In addition, the effect of iNOS inhibition on renal function was evaluated. METHODS: Sprague-Dawley rats underwent 45 min of left renal ischemia and contralateral nephrectomy followed by various periods of reperfusion and renal function analysis [plasma creatinine, fractional excretion of sodium (FENa), creatinine clearance (CrCl), and measurement of plasma and urine NO levels]. In addition, the effect of treatment with 1400W, a highly selective iNOS inhibitor, was evaluated. RESULTS: Renal dysfunction peaked at 48 h after reperfusion and immunohistochemistry studies revealed iNOS expression in the vasculature (3 h) and renal tubules (48 h) after reperfusion. Renal function improved significantly in treated animals compared to controls [creatinine of 1.1 v. 1.9 mg/dl (P < 0.05) and CrCl of 0.54 v. 0.31 ml/min (P < 0.05), respectively]. In addition, FENa was decreased by 50%, plasma NO levels were significantly lower (32.7 v. 45.7 micromol/L, P < 0.01), and deposition of nitrotyosine in the tubules of treated rats was less than in control animals. CONCLUSIONS: These data support the hypothesis that iNOS and NO are involved in the pathogenesis of renal I/R injury and suggests that use of iNOS inhibitors may be a valuable therapeutic strategy clinical situations where renal I/R may be prevalent.     

Inhibition of inducible nitric oxide synthase reduces renal ischemia/reperfusion injury

BACKGROUND: Nitric oxide (NO), produced via inducible nitric oxide synthase (iNOS), is implicated in the pathophysiology of renal ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the effects of the iNOS inhibitors L-N6-(1-iminoethyl)lysine (L-NIL) and aminoethyl-isothiourea (AE-ITU) on (a) renal dysfunction and injury mediated by bilateral I/R of rat kidneys in vivo and (b) cytokine-stimulated NO production by primary cultures of rat proximal tubule (PT) cells.METHODS: Male Wistar rats subjected to bilateral renal ischemia (45 min) followed by reperfusion (6 h). Rats were administered either L-NIL (3 mg/kg IV bolus 15 min prior to I/R followed by 1 mg/kg/h throughout I/R) or AE-ITU (1 mg/kg IV bolus 15 min prior to I/R followed by 1 mg/kg/h throughout I/R). Serum and urinary biochemical indicators of renal dysfunction and injury were measured; serum creatinine (SCr, glomerular dysfunction), fractional excretion of Na+ (FENa, tubular dysfunction), serum aspartate aminotransferase (sAST, I/R injury) and urinary N-acetyl-beta-d-glucosaminidase (uNAG, tubular injury). Additionally, renal sections were used for histological grading of renal injury and for immunological evidence of nitrotyrosine formation. Nitrate/nitrate levels in plasma were measured using the Griess assay and used as an indicator of NO production. Primary cultures of rat PT cells were incubated with interferon-gamma(IFN-gamma, 100 IU/mL) and lipopolysaccharide (LPS, 10 microg/mL) for 24 h, either in the absence or presence of increasing concentrations of L-NIL or AE-ITU (0.001 to 1 mmol/L) after which nitrite/nitrate levels were measured using the Griess assay.RESULTS: L-NIL and AE-ITU significantly reduced the I/R-mediated increases in SCr, FENa, sAST and uNAG, indicating attenuation of I/R-mediated renal dysfunction and injury. Specifically, L-NIL and AE-ITU reduced the I/R-mediated glomerular and tubular dysfunction and biochemical and histological evidence of tubular injury. Both L-NIL and AE-ITU attenuated the plasma levels of nitrate (indicating reduced NO production) and the immunohistochemical evidence of the formation of nitrotyrosine. In vitro, L-NIL and AE-ITU both significantly reduced cytokine-stimulated NO production by primary cultures of rat PT cells in a dose-dependent manner.CONCLUSIONS: These results suggest that L-NIL and AE-ITU reduce the renal dysfunction and injury associated with I/R of the kidney, via inhibition of iNOS activity and subsequent reduction of NO (and peroxynitrite) generation. We propose that selective and specific inhibitors of iNOS activity may be useful against the NO-mediated renal dysfunction and injury associated with I/R of the kidney.     

Protective role of nitric oxide in ischemia and reperfusion injury of the liver

Background: The suppressed production of nitric oxide (NO), associated with endothelial dysfunction, is thought to be a cause of ischemia and reperfusion injury of the liver. But findings of the salutary effects of NO enhancement on such injury have been conflicting. In this study, we tested our hypothesis that NO enhancement would attenuate ischemic liver injury. For this purpose, an NO precursor, L-arginine, and a novel NO donor, FK409, were applied to a 2-hour total hepatic vascular exclusion model in dogs.Study Design: L-arginine was administered IV at a dose of 100 mg/kg twice (n = 5), while 300 mg/kg twice of FK409 was infused continuously into the portal vein (n = 5). The drugs were given to the animals for 30 and 60 minutes before and after ischemia, respectively. Nontreated animals were used as the control (n = 10). Two-week survival, systemic and hepatic hemodynamics indices, liver function tests, energy metabolism, and histopathology were analyzed.Results: Both treatments comparably augmented hepatic tissue blood flow, decreased liver enzyme release, and increased high-energy phosphate restoration during the reperfusion period, all of which contributed to rescuing all of the treated animals from the 2-hour total hepatic ischemia. In contrast, ischemia caused 70% mortality in the control group. Histologically, structural abnormality and neutrophil infiltration were markedly attenuated by the treatments. Systemic hypotension was observed in the animals treated with FK409, however.Conclusions: Our data demonstrate that NO enhancement alleviates the liver injury caused by ischemia and reperfusion. The supplementation of L-arginine, rather than FK409, is considered more applicable to clinical use because of the absence of systemic adverse effects.     

Acute remote ischemic preconditioning II: the role of nitric oxide

The purpose of this study was to determine whether nitric oxide (NO) plays a role in the mechanism of acute "classic" as well as acute remote ischemic preconditioning (IP). Thirty-two male Wistar rats were divided into five experimental groups. The rat cremaster flap in vivo microscopy model was used for assessment of ischemia/reperfusion injury. In the control group (CG, n = 8), a 2-hr flap ischemia was induced after preparation of the cremaster muscle. The animals of group NO (n = 6) received 500 nmol/kg of the NO-donor spermine/nitric oxide complex (Sper/NO) intravenously 30 min prior to ischemia. The group LN + P (L-NAME + preclamping, n = 6) received 10 mg/kg Nomega-nitro-L-arginine methyl ester (L-NAME) intravenously before preclamping of the flap pedicle (10-min cycle length, 30-min reperfusion). L-NAME (10 mg/kg) was administered in group LN + T (L-NAME + tourniquet, n = 6) before ischemia of the right hindlimb was induced, using a tourniquet for 10 min after flap elevation. The limb was then reperfused for 30 min. Thereafter, flap ischemia was induced in each group as in group CG. In vivo microscopy was performed after 1 hr of flap reperfusion in each animal. Group NO demonstrated a significantly higher red blood cell velocity (RBV) in the first-order arterioles and capillaries, a higher capillary flow, and a decreased number of leukocytes adhering to the endothelium (stickers) of the postcapillary venules by comparison to all other groups (P < 0.05). The average capillary RBV and capillary flow were still higher in the CG than in the groups receiving L-NAME (P < 0.05). The data show that NO plays an important role in the mechanism of both acute "classic" as well as acute remote IP, since the administration of a NO-donor previous to ischemia simulates the effect of IP, whereas the nonspecific blocking of NO synthesis by L-NAME abolishes the protective effect of flap preconditioning.     

Inhibiting inducible nitric oxide synthase with rutin reduces renal ischemia/reperfusion injury

Background

Nitric oxide (NO) seems to play an important role during renal ischemia/reperfusion (I/R) injury. We investigated whether rutin inhibits inducible nitric oxide synthase (iNOS) and reduces 3-nitrotyrosine (3-NT) formation in the kidneys of rats during I/R.

Methods

Wistar albino rats were nephrectomized unilaterally and, 2 weeks later, subjected to 45 minutes of left renal pedicle occlusion followed by 3 hours of reperfusion. We intraperitoneally administered L-N6-(1-iminoethyl)lysine (L-NIL; 3 mg/kg) for 30 minutes or rutin (1 g/kg) for 60 minutes before I/R. After reperfusion, kidney samples were taken for immunohistochemical analysis of iNOS and 3-NT. We measured plasma nitrite/nitrate and cyclic guanosine monophosphate (cGMP) to evaluate NO levels.

Results

Ischemia/reperfusion caused plasma cGMP to increase significantly. Similarly, plasma nitrite/nitrate was elevated in the I/R group compared with the control group. Histochemical staining was positive for iNOS and 3-NT in the I/R group. Pretreatment with L-NIL or rutin significantly mitigated the elevation of plasma cGMP and nitrite/nitrate. These changes in biochemical parameters were also associated with changes in immunohistochemical appearance. Pretreatment with L-NIL or rutin significantly decreased the incidence and severity of iNOS and 3-NT formation in the kidney tissues.

Conclusion

Our findings suggest that high activity of iNOS causes renal I/R injury, and that rutin exerts protective effects, probably by inhibiting iNOS.     

Protective role of nitric oxide induced by ischemic preconditioning on cold ischemic-reperfusion injury of rat liver graft

Aims

To investigate the protective role of nitric oxide (NO) induced by ischemic preconditioning (IP) on cold ischemic-reperfusion (IR) injury of rat liver grafts.

Methods

One hundred twenty-eight male Sprague Dawley rats used for orthotopic liver transplantation were randomly divided into four groups (n = 32): administering heparin before ischemic reperfusion (control group); IP with 10-minute ischemia and 10-minute reperfusion before IR (IP group); adenosine before IR (Ade group); and L-NAME (NG-nitro-L-arginine methyl ester) + IP before IR (NAME group). Half of each group were used to investigate 1-week recipient survival rate, and another to obtain blood and hepatic tissue samples after 2-hour reperfusion.

Results

One-week survival bile production, serum NO, and antioxidase activity were higher but serum alanine aminotransferase, tumor necrosis factor-α, and superoxide levels in hepatic tissue were lower in the IP group and Ade group versus the control group or NAME group. Liver sinusoidal endothelial cells in the IP and Ade groups showed less injury than the other groups.

Conclusion

NO induced by IP can improve 1-week survival and rat liver function as well as protect liver sinusoidal endothelial cells.     

Antioxidative effects of exogenous nitric oxide versus antioxidant vitamins on renal ischemia reperfusion injury

The objectives of this study were to compare the protective influence of exogenous nitric oxide on renal ischemia reperfusion (I/R) injury with that of the antioxidant vitamins C and E. Sprague-Dawley rats were divided into three groups ( n=12 per group). Normal saline solution was given in group 1, a vitamin C (200 mg/kg/d) plus vitamin E (100 mg/kg/d) combination in group 2 for 3 days before operating and Na-nitroprusside (5 mg/kg/d) in group 3 before reperfusion. The left kidneys were exposed to warm ischemia for 40 min followed by reperfusion for 90 min. The right kidneys were used as internal controls. After both kidneys were removed, histopathological examinations were performed, and oxidative and antioxidative parameters were measured. In the postischemic reperfused rat kidneys, the renal lipid peroxidation level was significantly lower, and the renal GSH level higher in the group given Na-nitroprusside compared with groups 1 and 2. Renal specific xanthine oxidase activity was also significantly lower in the group treated with Na-nitroprusside than in the groups given vitamins or saline. There was a significant, negative correlation between lipid peroxidation and reduced glutathione levels. Our results suggest that the exogenous nitric oxide (Na-nitroprusside) inhibits xanthine oxidase, and has more apparent preventive features for renal I/R injury than the antioxidant vitamins C+E.     

内源性一氧化氮在非创伤性缺血预处理中对兔肺的保护作用

目的探讨内源性一氧化氮（NO）在非创伤性缺血预处理（N—WIP）中对兔肺缺血／再灌注（I／R）损伤的保护作用及可能机制。方法采用N-WIP及经典缺血预处理（C-IP）的动物模型，比较两种缺血预处理方法中内源性NO对兔肺在缺血／再灌注损伤中的保护效应。将40只大白兔随机平均分为4组：对照组、I／R组、C—IP组和NWIP组。对比观察各组血清及肺组织中NO2^-／NO3^-、丙二醛（MDA）含量及超氧化物歧化酶（SOD）活性以及肺湿／干重比。结果N—WIP组和C-IP组的兔肺再灌注后NO2^-／NO3^-含量均高于I／R组（P〈0．01），甚至高于对照组（P〈0．05）。两种缺血预处理组SOD活性均高于I／R组（P〈0．01），肺湿／干重比和MDA含量均低于I／R组（P〈0．05，P〈0．01）。结论N-WIP与C-IP对移植肺在缺血／再灌注损伤中具有同等强度的保护作用。其机制可能是通过诱发内源性一氧化氮（NO）舒张血管，从而起到保护血管内皮的效应。     

The role of nitric oxide pathway in the renal ischemia-reperfusion injury in rats

INTRODUCTION: Nitric oxide (NO), synthesized from L-arginine by the enzyme nitric oxide synthase (NOS), seems to play an ambiguous role during tissue ischemia-reperfusion injury. Our objective was to evaluate the effects of L-arginine, a NO donor, and N(G)-nitro-L-arginine-methylester (L-NAME), a NOS inhibitor, on oxidative stress, renal dysfunction, histologic alterations and surgical mortality rate induced by renal ischemia-reperfusion (RIR) in uninephrectomized rats. MATERIALS AND METHODS: One-hundred and ninety-seven Wistar rats were randomized into five experimental groups. Group 1: sham operation; group 2: right uninephrectomy (UNI); group 3: UNI + RIR in the contralateral kidney; group 4: UNI + L-NAME (20 mg/kg; intraperitoneally) + RIR; and group 5: UNI + L-arginine + RIR. The effect of the drugs was evaluated by lipid peroxidation measured by the renal malondialdehyde (MD) content and chemiluminescence (CL) levels, serum creatinine (Cr) levels, urinary volume, tubular necrosis and athrophy, inflammatory infiltrate, interstitial fibrosis as histologic evaluation and surgical mortality rate after the procedures. A P value less than 0.05 was considered significant. RESULTS: Right uninephrectomy did not alter the renal parameters. RIR increased Cr levels (at 24 and 96 h of reperfusion), index of lipid peroxidation (both MD and QL levels), and worsened the histologic aspects. Pretreatment with L-arginine reduced the kidney levels of QL when compared with the non-treated group (5574 +/- 909 vs. 13 660 +/- 1104 cps/mg of protein; P < 0.05) but increased the MD levels (0.97 +/- 0.24 vs. 0.79 +/- 0.06 nmol/mg of protein; P < 0.05). Moreover, L-arginine attenuated the increment of Cr levels, inflammatory infiltrate and tubular athrophy in rats subjected to RIR (P < 0.05). On the other hand, pretreatment with L-NAME increased both CL (17 482 +/- 4397 vs. 13 660 +/- 1104 cps/mg of protein; P < 0.05) and MD levels (1.16 +/- 0.11 vs. 0.79 +/- 0.06 nmol/mg of protein; P < 0.05). Furthermore, L-NAME worsened the renal dysfunction (P < 0.05) at 192 h after the RIR, and surgical mortality rates were similar (P > 0.05). CONCLUSION: L-arginine has a tendency to exert a beneficial effect on renal damage during RIR in rats. Moreover, L-NAME seems to worsen the renal damage by increasing the kidney-levels of CL and impairment of renal function probably due to reduction of NO production.     

Attenuation of renal ischemia/reperfusion injury by a triple drug combination therapy

BACKGROUND: Renal ischemia is of great clinical interest because of its role in renal failure and renal graft rejection. The purpose of this study was to investigate the therapeutic effects of a combination therapy of: n-acetyl cysteine (NAC), a potent antioxidant, sodium nitroprusside (SNP), a nitric oxide donor and phosphormidon (P), an endothelin-1 converting enzyme inhibitor, on tissue protection against renal ischemia/reperfusion injury in the canine model. METHODS: In this study, 15-20 kg male dogs were subjected to 90 minutes of warm unilateral renal ischemia after removal of one kidney and then divided into control, ischemia alone and treatment groups. Blood samples were collected from these dogs for measurement of kidney function tests and the kidneys were harvested at different time intervals for morphological evaluation, immunostaining and Tunnel Assay. RESULTS: Kidney function tests (serum creatinine and blood urea nitrogen [BUN]) showed a significant difference between untreated and treated groups. ** P <0.01, * P< 0.0001 for treated versus untreated. The protective effect of the combination therapy is also supported by light microscopic studies, immunostaining of renal tissue sections for pro-inflammatory cytokines (TNF-alpha and IFN-gamma), iNOS, and apoptosis by TUNEL assay. CONCLUSIONS: Our results suggest that pre-administration of a combination of NAC, SNP, and P attenuates renal ischemia/reperfusion injury. This has potential application in preservation of donor kidney for transplantation by protecting cells against free radical damage.     

Modulation of lung reperfusion injury by nitric oxide: impact of inspired oxygen fraction

BACKGROUND: Attempts to attenuate lung reperfusion injury by administration of inhaled nitric oxide have yielded conflicting results. We hypothesized that the inspired oxygen fraction may play an important role in determining the outcome of nitric oxide therapy. METHODS: Rat lungs were reperfused in a circuit incorporating a support animal either immediately after flushing (group A) or after 24-hr hypothermic storage (groups B-D). During the first 10 min of reperfusion, grafts were ventilated with 95% oxygen in groups A and B, 95% oxygen and 20 ppm nitric oxide in group C, and 20% oxygen and 20 ppm nitric oxide in group D. Ventilation during the subsequent 50 min of reperfusion was with 100% oxygen only, in all groups. RESULTS: Graft function in group B was poor compared to group A in terms of blood flow and pulmonary artery and peak airway pressures. In group C, although 5 out of 10 grafts functioned at control levels, the remainder performed poorly. Function in group D, on the other hand, was uniformly good. CONCLUSIONS: Inhaled nitric oxide can prevent lung reperfusion injury, but this effect may be compromised by concurrent ventilation with high oxygen concentrations.     

Protective effect of ischaemic preconditioning against ischaemia-induced reperfusion injury of skeletal muscle: how many preconditioning cycles are appropriate?

We investigated the efficacy of ischaemic preconditioning (IPC), consisting of repeated brief episodes of vascular occlusion followed by reperfusion, as protection against ischaemia-reperfusion injury of skeletal muscle, using a rat amputation-like model. Wistar rats underwent temporary amputation at the level of the femur, excluding the femoral vessels. The femoral artery and vein were clamped for 4h, using a micro-clamp, in the groups exposed to ischaemia. The rats were randomly divided into eight groups: a control (C) group (n = 7) with non-amputated and non-ischaemic hind limbs; a sham control (SC) group (n = 7) with amputated but non-ischaemic hind limbs; an ischaemia-reperfusion (IR) group (n = 7) with amputated and ischaemic hind limbs; and five IPC groups (n = 7 in each) with hind limbs that were subjected to 4h of ischaemia after one to five cycles of brief ischaemia and reperfusion for 10 min each, respectively. All rats were sacrificed 24h after reperfusion. The viability of the anterior tibial muscles was evaluated using nitroblue tetrazolium staining. The total viable area ratio (T-VAR) of the muscle tissue was calculated in each animal as follows: T-VAR\total viable area/total slice areae 100%. The T-VAR values of the eight groups were as follows: C group, 100% +/- 0%; SC group, 100% +/- 0%; IR group, 73.5% +/- 1.7%; IPC1 group, 79.4% +/- 6.5%; IPC2 group, 70.5% +/- 6.2%; IPC3 group, 90.6% +/- 2.8%; IPC4 group, 90.0% +/- 1.6%; and IPC5 group, 87.8% +/- 1.8%. The T-VARs in the IPC3, IPC4 and IPC5 groups were significantly higher (alpha < 0.01) than those in the IR group. In contrast, there were no significant differences between the T-VARs of the IPC1 and IPC2 groups and those of the IR group. In conclusion, three to five cycles of IPC could protect skeletal muscle against ischaemia. 2002 The British Association of Plastic Surgeons.     

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.     

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.     

Analysis of nitric oxide activity in prevention of reperfusion injury

This project was designed to determine the role of nitric oxide (NO) in the prevention of ischemia-reperfusion injury. Inferiorly based rectus abdominis muscle flaps were elevated in pigs and subjected to 6 hours of ischemia followed by 4 hours of reperfusion. Group I animals received a bolus of L-arginine before reperfusion, and a continuous infusion once flow was restored. Group II animals served as controls and received an equal volume of saline as a bolus and subsequent continuous infusion. Microdialysis was used to measure tissue NO levels, and these were correlated with muscle survival determined by vital staining with nitroblue tetrazolium. The results demonstrated a significant increase in tissue NO levels in L-arginine-supplemented animals (p < 0.05), which in turn correlated with a significant increase in muscle survival (p = 0.0051). These results suggest that administration of supplemental L-arginine to ischemic skeletal muscle during reperfusion results in increased NO production and decreased tissue damage.     

Reduction of renal ischemia reperfusion injury by hydrogen sulfide preconditioning through inhibiting oxidative stress

Objective To investigate the possible role of oxidative stress in the protection of hydrogen sulfide during renal ischemia reperfusion. Methods Male Wistar rats were randomly divided into 3 groups: sham operation (Sham) group, renal ischemia reperfusion (IR) group subject to occlusion of left renal pedicle for 45 min then reperfusion for 24 h, and sodium hydrosulfide (NaHS) preconditioning group with continuous infusion of NaHS (450 nmol/min) by left renal artery for 10 min before ischemia reperfusion. Renal injuries were evaluated by PAS staining. The protein levels of NADPH oxidase (NOX) 4, NOX2 were analyzed by Western blotting. The reactive oxygen species (ROS) level of renal tissue was determined by dihydroethidium (DHE) staining assay. Renal superoxide dismutase (SOD), malonic dialdehyde (MDA) and Scr, BUN were evaluated by chromatometry assay. Cell apoptosis were evaluated by TdT-mediated dUTP nick end labeling (TUNEL) staining. Results Compared with Sham group, in IR group the renal NOX4 and NOX2 protein expressions, the existence of acute tubular necrosis and ROS expression were up-regulated (all P＜0.01); MDA, Scr, and BUN were increased and SOD was decreased significantly in IR-treated kidney (all P＜0.01); Moreover, more apoptotic cells presented in the risk zone of IR-treated kindey (P＜0.01). The effects induced by IR were inhibited by NaHS. Compared to that in IR group, NaHS precondition reversed IR-induced damages of renal function and renal tissue, increased SOD activity and decreased MDA expression (all P＜0.05), as well as reduced the expression of NOX4, NOX2 and ROS (all P＜0.05). Moreover, NaHS precondition reduced apoptosis after IR (P＜0.05). Conclusions NaHS alleviates renal ischemia reperfusion injury through inhibiting oxidative stress. Hydrogen sulfide can decrease ROS by inhibiting the activation of NOX, further inhibit the activation of NOD-like receptor, and alleviate kidney damage.