L-arginine protects from pringle manoeuvere of ischemia-reperfusion induced liver injury

Experimental Detection and Simulation of Terahertz Spectra of Aqueous L-Arginine

Terahertz (THz) wave is a good candidate for biological sample detection, because vibration and rotation energy levels of biomolecule are in THz band. However, the strong absorption of THz wave by water in biological samples hinders its development. In this paper, a method for direct detection of THz absorption spectra of L-arginine suspension was proposed by using a strong field THz radiation source combined with a polyethylene cell with micrometer thickness in a THz time-domain spectroscopy system. And the THz absorption spectrum of L-arginine solution was simulated by the density functional theory and the simulation result is in good agreement with the experimental results. Finally, the types of chemical bond interaction that cause the absorption peak are identified based on the experimental and simulation results. This work paves a way to investigate the THz absorption spectra and intramolecular interactions of aqueous biological samples.

Role of Nitric Oxide and Protein S-Nitrosylation in Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a process in which damage is induced in hypoxic tissue when oxygen supply is resumed after ischemia. During IRI, restoration of reduced nitric oxide (NO) levels may alleviate reperfusion injury in ischemic organs. The protective mechanism of NO is due to anti-inflammatory effects, antioxidant effects, and the regulation of cell signaling pathways. On the other hand, it is generally known that S-nitrosylation (SNO) mediates the detrimental or protective effect of NO depending on the action of the nitrosylated target protein, and this is also applied in the IRI process. In this review, the effect of each change of NO and SNO during the IRI process was investigated.

Hepatic ischemia reperfusion injury: effect of moderate intensity exercise and oxytocin compared to l-arginine in a rat model

Background

Hepatic ischemia reperfusion (IR) injury is considered as a main cause of liver damage and dysfunction. The l-arginine/nitric oxide pathway seems to be relevant during this process of IR. Although acute intense exercise challenges the liver with increased reactive oxygen species (ROS), regular training improves hepatic antioxidant status. Also, oxytocin (Oxy), besides its classical functions, it exhibits a potent antistress, anti-inflammatory, and antioxidant effects. This study was designed to evaluate the hepatic functional and structural changes induced by hepatic IR injury in rats and to probe the effect and potential mechanism of moderate intensity exercise training and/or Oxy, in comparison to a nitric oxide donor, l-arginine, against liver IR-induced damage.

Results

Compared to the sham-operated control group, the hepatic IR group displayed a significant increase in serum levels of ALT and AST, plasma levels of MDA and TNF-α, and significant decrease in plasma TAC and nitrite levels together with the worsening of liver histological picture. L-Arg, Oxy, moderate intensity exercise, and the combination of both Oxy and moderate intensity exercises ameliorated these deleterious effects that were evident by the significant decrease in serum levels of ALT and AST, significant elevation in TAC and nitrite, and significant decline in lipid peroxidation (MDA) and TNF-α, besides regression of histopathological score regarding hepatocyte necrosis, vacuolization, and nuclear pyknosis. Both the moderate intensity exercise-trained group and Oxy-treated group showed a significant decline in TNF-α and nitrite levels as compared to l-Arg-treated group. The Oxy-treated group showed statistical insignificant changes in serum levels of ALT, AST, and plasma levels of nitrite, MDA, TAC, and TNF-α as compared to moderate intensity exercise-trained group.

Conclusion

The combination of both moderate intensity exercise and Oxy displayed more pronounced hepatoprotection on comparison with l-Arg which could be attributed to their more prominent antioxidant and anti-inflammatory effects but not due to their NO-enhancing effect.

Pharmaceutical Preconditioning With Nitric Oxide Synthase and L-Arginine in Ischemic Tissues

BACKGROUND

Nitric oxide (NO) is a multifunctional signaling molecule involved in regulating vascular tone and tissue oxygenation. It is also an important cytoprotective agent against ischemia-reperfusion injury (IRI). Enhancing NO bioavailability via exogenous NO synthases (NOSs) and L-arginine promotes conversation to NO, circumventing the problem of nonfunctioning NOSs under hypoxic and acidic conditions. In this study, the authors evaluated the therapeutic efficacy of neuronal, inducible, and endothelial NOS and L-arginine on reperfusion-induced skin flap alterations.

METHODS

The vascular pedicle isolated rat skin flap model was used and underwent 3 hours of ischemia. At 30 minutes before ischemia, normal saline, endothelial-, inducible-, and neuronal NOSs (1/2 IU) and L-arginine (100 mg/kg body weight) were administered by means of intravenous infusion. The IRI-induced alterations were measured 5 days after the operation.

RESULTS

The 3 isoforms of NOS increased the flap vitality rate (VR) from 10% to 23% compared with the control group. L-Arginine treatment also increased the VR by approximately 15%. The combination of L-arginine with NOS resulted in even higher flap VRs. The best results could be achieved with the combination of endothelial NOS (2 IU) and L-arginine.

CONCLUSIONS

Modulation of NO bioavailability via exogenous application of NOSs and L-arginine significantly improved VRs in a skin flap rat model. This pharmacologic preconditioning has the potential to attenuate IRI-induced alterations in skin flaps.

Inducible Nitric Oxide Synthase and L-Arginine Optimizes Nitric Oxide Bioavailability in Ischemic Tissues Under Diabetes Mellitus Type 1

BACKGROUND

The mechanisms influencing the balance of nitric oxide (NO) bioavailability in tissues are negatively affected under diabetic and also under ischemic conditions. Free tissue transplantation for diabetic patients has to deal with both ischemic and diabetic circumstances, which lead to a significantly decrease in providing NO, thus increasing ischemia-reperfusion injury. In previous studies, we could prove that enhancing NO bioavailability leads to attenuated ischemia-reperfusion injury macrocirculatory and microcirculatory alterations in healthy and also in diabetes type 2 rats. This study is evaluating the role of inducible nitric oxide synthase in different dosages and L-arginine under diabetes type 1 conditions.

METHODS

Diabetic type 1 conditions were established via streptozotocin over a period of 4 weeks and verified via blood sugar, insulin, and C-peptide levels. Vascular pedicle isolated rat skin flap model that underwent 3 hours of ischemia was used. At 30 minutes before ischemia, normal saline, inducible nitric oxide synthase (NOS) (1/2 IE), and L-arginine (50 mg/kg body weight) were administered systemically. Ischemia/reperfusion (I/R)-induced alterations were measured 5 days after the operation.

RESULTS

The inducible NOS (iNOS) attenuated I/R-induced alterations under diabetic type 1 conditions significantly with vitality rates of 16.1% compared with control group (5.5%). Best results could be achieved with the combination of iNOS (1 IE) and L-arginine displaying vitality rates of 43%. Increased dosage of inducible nitric oxide (2 IE) led to decreased vitality rates (22.2%/27.4% without/with L-arginine).

CONCLUSIONS

Supporting the mechanisms of NO bioavailability via exogenous application of iNOS and L-arginine significantly attenuated I/R-induced alterations in a skin flap rat model. This pharmacologic preconditioning could be an easy and effective interventional strategy to uphold conversation of L-arginine to NO even on ischemic and type 1 diabetic conditions.

Effect of cardamonin on hepatic ischemia reperfusion induced in rats: Role of nitric oxide

Ischemia reperfusion (I/R) injury is a cellular damage in a hypoxic organ following the restoration of oxygen delivery. It may occur during organ transplantation, trauma and hepatectomies. Nitric oxide (NO) effects during hepatic I/R are complicated. The iNOS-derived NO has a deleterious effect, whereas eNOS-derived NO has a protective effect in liver I/R. Cardamonin (CDN) is an anti-inflammatory molecule and a novel iNOS inhibitor, and Nω-Nitro-L-arginine (L-NNA) is a NOS inhibitor. L-Arginine is a precursor of NOS. This study was designed to investigate the possible protective effects of CDN on hepatic I/R and the role of NO. Wistar rats were randomly divided into 5 groups (Sham, I/R, CDN, L-NNA and L-arginine). Liver ischemia was induced for 45min then reperfusion was allowed for 1h. L-Arginine and CDN ameliorated the deleterious effects of I/R through reducing the oxidative stress and hepatocyte degeneration. Both molecules decreased the elevated inflammatory cytokines and increased the antiapoptotic marker, Bcl2. Both agents increased NO and eNOS expression and decreased iNOS expression. In conclusion, increased NO/eNOS and suppression of iNOS expression have protective effects on I/R injury. While inhibition of eNOS and reduction of NO have deleterious effects on I/R injury. For the first time, we demonstrated that cardamonin improved functional and structural abnormalities of the liver following I/R by improving oxidative stress and inflammation and increasing the availability of NO produced by eNOS. Treatment with cardamonin could be a promising strategy in patients with hepatic I/R injury in different clinical situations.

Antioxidant, Antiapoptotic and Inflammatory Effects of Interleukin-18 Binding Protein on Kidney Damage Induced by Hepatic Ischemia Reperfusion

OBJECTIVE

Acute kidney injury (AKI) is a serious condition that can be induced by liver transplantation, major hepatic resection or prolonged portal vein occlusion. The AKI can increase the frequency of postoperative complications. In the current study, we aimed to investigate whether interleukin-18 binding protein (IL-18BP) pretreatment has a protective effect against possible kidney injury-mediated liver ischemia-reperfusion (IR) achieved by Pringle maneuver in an experimental rat model.

MATERIALS AND METHODS

A total of 21 Wistar albino rats were included in this study. Animals were equally and randomly separated into 3 groups as follows: Sham (n = 7), IR group (n = 7) and IR + IL-18BP group (n = 7). Serum aspartate transaminase, alanine aminotransaminase and lactate dehydrogenase enzyme activities and serum urea and creatinine levels were determined. Tumor necrosis factor-α, IL-6, IL-1β, interferon gamma, total oxidant status, total antioxidant status and oxidative stress index were measured in kidney tissue homogenate samples. Histopathological examination and immunohistochemical Caspase-3 staining were applied to examine the general morphologic structure and apoptosis.

RESULTS

Renal total oxidant status; oxidative stress index; IL-18 levels; serum aspartate transaminase, alanine aminotransaminase and lactate dehydrogenase activities and creatinine levels were significantly lower in IR + IL-18BP group, when compared with the IR group. Beside this, total antioxidant status levels were remarkably higher in IR + IL-18BP group, when compared with the IR group. The caspase-3 expression degree in IR group was remarkably higher than other groups.

CONCLUSIONS

It has been demonstrated that IL-18BP pretreatment may have inflammatory, antioxidant and antiapoptotic effects against AKI induced by hepatic IR.

Nebivolol Ameliorates Hepatic Ischemia/Reperfusion Injury on Liver But Not on Distant Organs

INTRODUCTION

Hepatic ischemia/reperfusion injury may occur after large tumor resection and liver transplantation procedures. Nitric oxide was shown to have protective effects on ischemia/reperfusion injury. Nebivolol is a compound that has been reported to improve nitric oxide release. We evaluated the effects of nebivolol in a rat liver ischemia/reperfusion model.

METHODS

A total of 40 rats were randomly divided into four groups (n = 10 each). Group I underwent only laparotomy, Group II was administered nebivolol and then underwent laparotomy, Group III underwent laparotomy and hepatic ischemia/reperfusion, and Group IV was administered nebivolol and then underwent laparotomy and hepatic ischemia/reperfusion. Serum AST, ALT, urea, and creatinine levels, and TAS and TOS levels of liver, lung, and kidney tissues were determined. Histopathological determination was also performed.

RESULTS

Nebivolol significantly reduced liver function tests in group IV, but it did not improve renal functions. Oxidative stress and abnormal histopathological findings were found to be reduced in liver tissue in group IV. Although the oxidative stress was increased after hepatic ischemia/reperfusion, nebivolol could not reduce the oxidative stress in kidney tissue. There were no significant differences between group III and group IV in terms of the histopathological changes in kidney tissue. There were no significant differences in lung tissue between the groups.

CONCLUSIONS

The results of this study suggest that nebivolol has protective effects on liver but not on distant organs in a hepatic ischemia/reperfusion injury model. These experimental findings indicate that nebivolol may be useful in the treatment of hepatic ischemia/reperfusion injury.

The effects of sulforaphane on the liver and remote organ damage in hepatic ischemia-reperfusion model formed with pringle maneuver in rats

BACKGROUND

The purpose of this study was to investigate the effect of Sulforaphane on ischemia/ reperfusion (IR) injury of the liver and distant organs resulting from liver blood flow arrest.

MATERIALS AND METHODS

Fourty Wistar rats were assigned into four groups, each included 10 rats were used. Group I as only laparatomy, Group II laparatomy and Sulforaphane application, Group III hepatic IR; and Group IV as hepatic IR and Sulforaphane application group. Animals were subjected to liver ischemia for 30 min and then reperfusion is started. 5 mg/kg Sulforaphane was applied via oral lavage 15 minutes before initiating the experimental study. Blood samples were taken from the animals for biochemical analysis at 60th minutes of the experiment in the first and second groups; 30 minutes after beginning reperfusion in the third and forth groups. Simultaneously, liver, lung and kidney tissues were sampled for biochemical and histopathological examinations.

RESULTS

The administration of sulforaphane significantly reduced the serum TOA and liver TOA levels, increased the serum TAC and liver TAC levels and also decreased The OSI and liver OSI levels. In the histopathologic examination, the injury was reduced by the administration of sulforaphane. Administration of sulforaphane did not lead to any significant changes in any parameter including histopathological parameters in both the kidney and the lung.

CONCLUSIONS

Sulforaphane reduced the liver oxidative stress from I/R injury. A histological injury in liver was reduced by sulforaphane administration. However, there were no significant effects of sulforaphane on the remote organ injuries induced by IR.

The protective effect of diosmin on hepatic ischemia reperfusion injury: an experimental study

Liver ischemia reperfusion injury (IRI) is an important pathologic process leading to bodily systemic effects and liver injury. Our study aimed to investigate the protective effects of diosmin, a phlebotrophic drug with antioxidant and anti-inflammatory effects, in a liver IRI model. Forty rats were divided into 4 groups. Sham group, control group (ischemia-reperfusion), intraoperative treatment group, and preoperative treatment group. Ischemia reperfusion model was formed by clamping hepatic pedicle for a 60 minute of ischemia followed by liver reperfusion for another 90 minutes. Superoxide dismutase (SOD) and catalase (CAT) were measured as antioaxidant enzymes in the liver tissues, and malondialdehyde (MDA) as oxidative stress marker, xanthine oxidase (XO) as an oxidant enzyme and glutathione peroxidase (GSH-Px) as antioaxidant enzyme were measured in the liver tissues and the plasma samples. Hepatic function tests were lower in treatment groups than control group (p<0.001 for ALT and AST). Plasma XO and MDA levels were lower in treatment groups than control group, but plasma GSH-Px levels were higher (p<0.05 for all). Tissue MDA levels were lower in treatment groups than control group, but tissue GSH-Px, SOD, CAT and XO levels were higher (p<0.05 for MDA and p<0.001 for others). Samples in control group histopathologically showed morphologic abnormalities specific to ischemia reperfusion. It has been found that both preoperative and intraoperative diosmin treatment decreases cellular damage and protects cells from toxic effects in liver IRI. As a conclusion, diosmin may be used as a protective agent against IRI in elective and emergent liver surgical operations.

Conventional, but not remote ischemic preconditioning, reduces iNOS transcription in liver ischemia/reperfusion

AIM: To study the effects of preconditioning on inducible nitric oxide synthase (iNOS) and interleukin 1 (IL-1) receptor transcription in rat liver ischemia/reperfusion injury (IRI).

METHODS: Seventy-two male rats were randomized into 3 groups: the one-hour segmental ischemia (IRI, n = 24) group, the ischemic preconditioning (IPC, n = 24) group or the remote ischemic preconditioning (R-IPC, n = 24) group. The IPC and R-IPC were performed as 10 min of ischemia and 10 min of reperfusion. The iNOS and the IL-1 receptor mRNA in the liver tissue was analyzed with real time PCR. The total Nitrite and Nitrate (NOx) in continuously sampled microdialysate (MD) from the liver was analyzed. In addition, the NOx levels in the serum were analyzed.

RESULTS: After 4 h of reperfusion, the iNOS mRNA was significantly higher in the R-IPC (ΔCt: 3.44 ± 0.57) group than in the IPC (ΔCt: 5.86 ± 0.82) group (P = 0.025). The IL-1 receptor transcription activity was reduced in the IPC group (ΔCt: 1.88 ± 0.53 to 4.81 ± 0.21), but not in the R-IPC group, during reperfusion (P = 0.027). In the MD, a significant drop in the NOx levels was noted in the R-IPC group (12.3 ± 2.2 to 4.7 ± 1.2 μmol/L) at the end of ischemia compared with the levels in early ischemia (P = 0.008). A similar trend was observed in the IPC group (11.8 ± 2.1 to 6.4 ± 1.5 μmol/L), although this difference was not statistically significant. The levels of NOx rose quickly during reperfusion in both groups.

CONCLUSION: IPC, but not R-IPC, reduces iNOS and IL-1 receptor transcription during early reperfusion, indicating a lower inflammatory reaction. NOx is consumed in the ischemic liver lobe.

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.

The nitric oxide pathway--evidence and mechanisms for protection against liver ischaemia reperfusion injury

Ischaemia reperfusion (IR) injury is a clinical entity with a major contribution to the morbidity and mortality of liver surgery and transplantation. A central pathway of protection against IR injury utilizes nitric oxide (NO). Nitric oxide synthase (NOS) enzymes manufacture NO from L-arginine. NO generated by the endothelial NOS (eNOS) isoform protects against liver IR injury, whereas inducible NOS (iNOS)-derived NO may have either a protective or a deleterious effect during the early phase of IR injury, depending on the length of ischaemia, length of reperfusion and experimental model. In late phase hepatic IR injury, iNOS-derived NO plays a protective role. In addition to NOS consumption of L-arginine during NO synthesis, this amino acid may also be metabolized by arginase, an enzyme whose release is increased during prolonged ischaemia, and therefore diverts L-arginine away from NOS metabolism leading to a drop in the rate of NO synthesis. NO most commonly acts through the soluble guanylyl cyclase-cyclic GMP- protein kinase G pathway to ameliorate hepatic IR injury. Both endogenously generated and exogenously administered NO donors protect against liver IR injury. The beneficial effects of NO on liver IR are not, however, universal, and certain conditions, such as steatosis, may influence the protective effects of NO. In this review, the evidence for, and mechanisms of these protective actions of NO are discussed, and areas in need of further research are highlighted.

The influence of short-term L-arginine supplementation on rats' muscular and hepatic cells in ischemia-reperfusion syndrome

Due to the complex mechanisms of L-arginine activity, it is difficult to determine the clinical significance of supplementation with this amino acid. The objective of this study was to determine the influence of short-term supplementation with L-arginine in stress conditions, induced by ischemia-reperfusion syndrome, by assessing the damage to muscular and hepatic cells on the basis of creatine kinase (CK), alanine aminotransferase (ALAT) and aspartic aminotransferase (AspAT) activity in blood and the level of oxygen free radicals in analyzed tissues of rats. We observed that induced ischemia of hind limb caused an increase in CK, ALAT and AspAT activity and an increase in the level of free radicals in liver, but not in skeletal muscle. Supplementation with L-arginine led to a reduction in serum activity of CK and AspAT and reduction of the level of free radicals in analysed tissues. Simultaneous supplementation with L -arginine AND L-NAME resulted in a reversal of changes induced by L-arginine supplementation in the case of AspAT and free radicals in skeletal muscle. The results indicate that under conditions of ischemia-reperfusion, short-term administration of L-arginine has a protective effect on skeletal muscle manifesting itself by reduction of CK in the serum and reduction of free radicals level in THIS tissue.

Remote or conventional ischemic preconditioning--local liver metabolism in rats studied with microdialysis

BACKGROUND

Ischemic preconditioning (IPC) of the liver decreases liver injury secondary to ischemia and reperfusion. An attractive alternative to IPC is remote ischemic preconditioning (R-IPC), but these two methods have not previously been compared.

MATERIAL AND METHODS

Eighty-seven rats were randomized into four groups: sham operated (n = 15), 1 h segmental ischemia (IRI, n = 24), preceded by IPC (n = 24), or R-IPC (n = 24) (to the left hindleg). IPC and R-IPC were performed with 10 min ischemia and 10 min of reperfusion. Analyses of liver microdialysate (MD), serum transaminase levels, and liver histology were made.

RESULTS

Rats treated with IPC and R-IPC had significantly lower AST, 71.5 (19.6) IU/L respective 96.6 (12.4) at 4 h reperfusion than those subjected to IRI alone, 155 (20.9), P = 0.0004 and P = 0.04 respectively. IPC also had lower ALT levels, 41.6 (11.3) IU/L than had IRI 107.4 (15.5), P = 0.003. The MD glycerol was significantly higher during ischemia in the R-IPC [759 (84) μM] and the IRI [732 (67)] groups than in the IPC 514 (70) group, P = 0.022 and P = 0.046 respectively. The MD glucose after ischemia was lower in the IPC group 7.1 (1.2) than in the IRI group 12.7 (1.6), P = 0.005. Preconditioning to the liver caused an direct increase in lactate, glucose and glycerol in the ischemic segment compared with the control segment an effect not seen in the R-IPC and IRI groups.

CONCLUSIONS

IPC affects glucose metabolism in the rat liver, observed with MD. IPC reduces liver cell injury during ischemic and reperfusion in rats. R-IPC performed over the same length of time as IPC does not have the same effect as the latter on ALT levels and MD glycerol; this may suggest that R-IPC does not offer the same protection as IPC in this setting of rat liver IRI.

Role of nitric oxide in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) occurs upon restoration of hepatic blood flow after a period of ischemia. Decreased endogenous nitric oxide (NO) production resulting in capillary luminal narrowing is central in the pathogenesis of IRI. Exogenous NO has emerged as a potential therapy for IRI based on its role in decreasing oxidative stress, cytokine release, leukocyte endothelial-adhesion and hepatic apoptosis. This review will highlight the influence of endogenous NO on hepatic IRI, role of inhaled NO in ameliorating IRI, modes of delivery, donor drugs and potential side effects of exogenous NO.

Molecular biology of liver ischemia/reperfusion injury: established mechanisms and recent advancements

Hepatic ischemia/reperfusion (I/R) injury occurs in a variety of clinical contexts, including transplantation, liver resection surgery, trauma, and hypovolemic shock. The mechanism of organ damage after I/R has been studied extensively and consists of complex interactions of multiple inflammatory pathways. The major contributors to I/R injury include production of reactive oxygen species, release of proinflammatory cytokines and chemokines, and activation of immune cells to promote inflammation and tissue damage. Recent research has focused on the mechanisms by which these immune responses are initially activated through signaling molecules and their cellular receptors. Thorough understanding of the pathophysiology of liver I/R may yield novel therapeutic strategies to reduce I/R injury and lead to improved clinical outcomes.

Hyperbaric oxygen therapy protects the liver from apoptosis caused by ischemia-reperfusion injury in rats

PURPOSE

: The present paper aimed to investigate the role of hyperbaric oxygen treatment (HBO) and the apoptosis in rat liver ischemia-reperfusion injury (IRI).

METHODS

: Thirty-seven male Wistar rats were subjected to 30 minutes of hepatic ischemia and 30 minutes of reperfusion and randomly distributed into six groups: G-I/R (n = 8), control without HBO; G-HBO/I (n = 8), HBO only during the ischemia period; G-HBO/R (n = 8), HBO only during the reperfusion period; G-HBO-I/R (n = 8), HBO during both the ischemia and reperfusion periods; G-Sh (n = 3), HBO without ischemia or reperfusion as sham group; G-C (n = 2) for control of current apoptosis expression on the normal liver tissue. HBO was carried out using a transparent, cylindrical acrylic chamber with a pressure of 2.0 ATA. Hepatic samples were stained for caspase-3 cleavage.

RESULTS

: Apoptotic cells were identified in all groups. In the hepatic specimens of animals HBO-treated during ischemia (GHBO-I), there was a significant decrease (P < 0.001) in the number of cells undergoing apoptosis (1.62 +/- 0.91). The apoptotic index showed no significant difference in the animals HBO-treated during ischemia/reperfusion (5.75 +/- 1.28) compared with the G-I/R (3.5 +/- 0.75), which had no HBO treatment. The apoptosis index (11.25 +/- 1.90) was significantly higher (P < 0.01) in HBO-treated animals during the reperfusion period when compared with any of the other groups.

CONCLUSION

: A favorable effect was obtained when hyperbaric oxygen was administered early during ischemia. The hyperbaric oxygen in later periods of reperfusion was associated with a more severe apoptosis index. (c) 2009 Wiley-Liss, Inc. Microsurgery 2009.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Pulmonary perfusion with L-arginine ameliorates post-cardiopulmonary bypass lung injury in a rabbit model

BACKGROUND

Post-cardiopulmonary bypass (CPB) lung injury is the combination of whole body inflammatory response and local ischemia-reperfusion (IR) injury. We investigated the benefit of pulmonary perfusion with L-arginine in protection against post-CPB lung injury.

METHODS

New Zealand white rabbits (n = 50, weight, 2.5-2.8 kg) were divided into five groups (n = 10 each): sham (sham sternotomy), CPB (CPB without pulmonary perfusion), perfusion (CPB with pulmonary perfusion), L-arginine (CPB with perfusion + L-arginine), and L-NAME (CPB with perfusion + L-NAME). The duration of CPB was 60 min followed by 2 h of reperfusion. Pulmonary perfusion was performed every 20 min through the pulmonary artery during CPB. Checking parameters included: (1) pulmonary vascular resistance, (2) pulmonary artery endothelium relaxation (organ chamber study), and (3) IR marker (myeloperoxidase) and inflammatory markers (TNF-α, IL-B, NF-κB).

RESULTS

CPB induced pulmonary artery endothelium dysfunction manifested by increased pulmonary vascular resistance and impaired pulmonary artery relaxation. Pulmonary perfusion could significantly reverse the phenomenon (P < 0.01) while provision of NO precursor-L-arginine with pulmonary perfusion together further possessed significant relaxation ability for pulmonary arterial endothelium compared with perfusion alone (P < 0.05). Accordingly, lung parenchyma myeloperoxidase activity and inflammatory cytokine level were also markedly increased after CPB (P < 0.05). Pulmonary perfusion could partially decrease the response, whereas additional L-arginine further attenuated inflammatory cytokine release (P < 0.05).

CONCLUSIONS

Pulmonary perfusion during CPB partially ameliorates CPB-induced lung injury. Pulmonary perfusion with L-arginine could further attenuate lung injury by restoring endothelial function and decreasing inflammatory response.

Ca2+ concentrations are key determinants of ischemia-reperfusion-induced apoptosis: significance for the molecular mechanism of Bcl-2 action

The mechanism of action of the anti-apoptotic oncogene Bcl-2 and Ca2+ regulation in ischemia-reperfusion injury is still obscure. In this present study, we investigated mitochondrial Ca2+ overloads and mechanism of action of Bcl-2. Eighteen Wistar rats were divided into sham-operated control group (I) (n = 6), ischemia and reperfusion group (II) (n = 6), and amlodipine-treated group (1 mg kg(-1) body weight/daily by oral route for 7 days before inducing ischemia-reperfusion maneuver) (III) (n = 6). Rats were subjected to 1 h of hepatic ischemia followed by 3-h reperfusion. Mitochondrial Ca2+ content was determined and damage was confirmed by transmission electron microscopy. Decrease of mitochondrial Ca2+ level is related to reduction of apoptosis and cellular changes, viz. increased Bcl-2 expression followed by reduction in secondary endoplasmic reticulum, whereas ischemia/reperfusion group shows overloading Ca2+ ions and decrease in Bcl-2 expression as compared to sham-operated rats. Thus, Bcl-2-dependent reduction of Ca2+ is an important component of the anti-apoptotic program in ischemia-reperfusion injury.

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.