Alanyl-glutamine dipeptide inhibits hepatic ischemia-reperfusion injury in rats

Dynamics of glutamine synthetase expression in hepatic ischemia-reperfusion injury: Implications for therapeutic interventions

BACKGROUND

Hepatic ischemia-reperfusion injury (IRI) poses a great challenge in liver surgery and transplantation because of oxidative stress and inflammatory responses. The changes in glutamine synthetase (GS) expression during hepatic IRI remain unclear.

AIM

To investigate the dynamic expression of GS during hepatic IRI.

METHODS

Following hepatic ischemia for 1 h and reperfusion, liver tissue samples were collected at 0.5, 6, and 24 hours postreperfusion for fixation, embedding, sectioning. Hematoxylin and eosin staining and GS staining were performed.

RESULTS

GS expression rapidly decreases in hepatocytes around the central vein after IRI, reaching its lowest point at 6 hours postreperfusion, and then gradually recovers.

CONCLUSION

GS is highly sensitive to IRI, highlighting its potential role as an indicator of liver injury states and a target for therapeutic intervention.

Comparative Metabolomic Profiles of Vascular Involvement in Behçet's Disease

BACKGROUND

Behçet's disease is a systemic, inflammatory disease affecting multiple organs. Vascular involvement is the main cause of morbidity and mortality in Behçet's disease patients. Though clinically well-defined, there is limited information related to disease pathogenesis and vascular incidence in this patient group. The aim of this study is to investigate the unique metabolic signatures of Behçet's disease patients with vascular involvement.

METHODS

Metabolomic profiling was performed on serum samples of 48 Behçet's disease patients (18 with vascular involvement) and 40 healthy controls using gas chromatography-mass spectrometrybased untargeted metabolomics analysis. Multivariate and univariate statistical analyses were performed to find altered metabolites and pathways.

RESULTS

Untargeted metabolomics results showed that a total of 168 metabolites were identified. The comparison between the groups of Behçet's disease, vascular involvement in Behçet's disease, and the healthy control group showed that altered amino acid and oxidative stress pathways, especially with glutathione synthesis, could be an important stage for developing Behçet's disease.

CONCLUSION

In the present work, the untargeted metabolomics approach provided new molecular insights for a better understanding of Behçet's disease pathogenesis and also developing vascular involvement in Behçet's disease at the metabolite level. The results showed that vascular involvement in Behçet's disease could be highly linked with amino acid metabolism and also the antioxidant system, and these disease-related pathways could be evaluated with further experiments for diagnosis and prognosis of Behçet's disease and also for vascular involvement in Behçet's disease.

Alanyl-Glutamine Protects against Lipopolysaccharide-Induced Liver Injury in Mice via Alleviating Oxidative Stress, Inhibiting Inflammation, and Regulating Autophagy

Acute liver injury is a worldwide problem with a high rate of morbidity and mortality, and effective pharmacological therapies are still urgently needed. Alanyl-glutamine (Ala-Gln), a dipeptide formed from L-alanine and L-glutamine, is known as a protective compound that is involved in various tissue injuries, but there are limited reports regarding the effects of Ala-Gln in acute liver injury. This present study aimed to investigate the protective effects of Ala-Gln in lipopolysaccharide (LPS)-induced acute liver injury in mice, with a focus on inflammatory responses and oxidative stress. The acute liver injury induced using LPS (50 μg/kg) and D-galactosamine (D-Gal) (400 mg/kg) stimulation in mice was significantly attenuated after Ala-Gln treatment (500 and 1500 mg/kg), as evidenced by reduced plasma alanine transaminase (ALT) (p < 0.01, p < 0.001), aspartate transaminase (AST) (p < 0.05, p < 0.001), and lactate dehydrogenase (LDH) (p < 0.01, p < 0.001) levels, and accompanied by improved histopathological changes. In addition, LPS/D-Gal-induced hepatic apoptosis was also alleviated by Ala-Gln administration, as shown by a greatly decreased ratio of TUNEL-positive hepatocytes, from approximately 10% to 2%, and markedly reduced protein levels of cleaved caspase-3 (p < 0.05, p < 0.001) in liver. Moreover, we found that LPS/D-Gal-triggered oxidative stress was suppressed after Ala-Gln treatment, the effect of which might be dependent on the elevation of SOD and GPX activities, and on GSH levels in liver. Interestingly, we observed that Ala-Gln clearly inhibited LPS/D-Gal exposure-induced macrophage accumulation and the production of proinflammatory factors in the liver. Furthermore, Ala-Gln greatly regulated autophagy in the liver in LPS/D-Gal-treated mice. Using RAW264.7 cells, we confirmed the anti-inflammatory role of Ala-Gln-targeting macrophages.

Glutamine ameliorates lipopolysaccharide-induced cardiac dysfunction by regulating the toll-like receptor 4/mitogen-activated protein kinase/nuclear factor-kB signaling pathway

The inflammatory response of sepsis induced by lipopolysaccharide (LPS) may result in irreversible cardiac dysfunction. Glutamine (GLN) has a multitude of pharmacological effects, including anti-inflammatory abilities. Previous studies have reported that GLN attenuated LPS-induced acute lung injury and intestinal mucosal injury. The present study investigated whether GLN exerts potential protective effects on LPS-induced cardiac dysfunction. Male Sprague-Dawley rats were divided into three groups (15 rats per group), including the control (saline-treated), LPS and LPS+GLN groups. Pretreatment with 1 g/kg GLN was provided via gavage for 5 days in the LPS+GLN group, while the control and LPS groups received the same volume of normal saline. On day 6, a cardiac dysfunction model was induced by administration of LPS (10 mg/kg). After 24 h, the cardiac functions of the rats that survived were detected by echocardiography and catheter-based measurements. The serum levels of tumor necrosis factor α (TNF-α), interleukin (IL)-1β and IL-6 were detected by enzyme-linked immunosorbent assay, while the mRNA levels of toll-like receptor (TLR)4, TNF-α, IL-1β and IL-6 were examined by reverse transcription-quantitative polymerase chain reaction. The protein expression of TLR4, mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) were also determined by western blot analysis. The results of echocardiography and catheter-based measurements revealed that GLN treatment attenuated cardiac dysfunction. GLN treatment also attenuated the serum and mRNA levels of the pro-inflammatory cytokines. In addition, the protein levels of TLR4, phosphorylated (p-)extracellular signal-regulated kinase, p-c-Jun N-terminal kinase and p-P38 were reduced upon GLN pretreatment. Furthermore, GLN pretreatment resulted in decreased activation of the NF-κB signaling pathway. In conclusion, GLN has a potential therapeutic effect in the protection against cardiac dysfunction mediated by sepsis through regulating the TLR4/MAPK/NF-κB signaling pathway.

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.

Protection of rat liver against hepatic ischemia-reperfusion injury by a novel selenocysteine-containing 7-mer peptide

Hepatic ischemia-reperfusion (I-R) injury causes acute organ damage or dysfunction, and remains a problem for liver transplantation. In the I-R phase, the generation of reactive oxygen species aggravates the injury. In the current study, a novel selenocysteine-containing 7‑mer peptide (H-Arg-Sec-Gly-Arg-Asn-Ala-Gln-OH) was constructed to imitate the active site of an antioxidant enzyme, glutathione peroxidase (GPX). The 7‑mer peptide which has a lower molecular weight, and improved water‑solubility, higher stability and improved cell membrane permeability compared with other GPX mimics. Its GPX activity reached 13 U/µmol, which was 13 times that of ebselen (a representative GPX mimic). The effect of this GPX mimic on I‑R injury of the liver was assessed in rats. The 7‑mer peptide significantly inhibited the increase in serum hepatic amino‑transferases, tissue malondialdehyde, nitric oxide contents, myeloperoxidase activity and decrease of GPX activity compared with I‑R tissue. Following treatment with the 7‑mer peptide, the expression of B‑cell CLL/lymphoma‑2 (Bcl‑2) was significantly upregulated at the mRNA and protein level compared with the I‑R group, as determined by reverse transcription‑polymerase chain reaction and immunohistochemistry, respectively. By contrast, Bcl‑2 associated X protein (Bax) was downregulated by the 7‑mer peptide compared the I‑R group. Histological and ultrastructural changes of the rat liver tissue were also compared among the experimental groups. The results of the current study suggest that the 7‑mer peptide protected the liver against hepatic I‑R injury via suppression of oxygen‑derived free radicals and regulation of Bcl‑2 and Bax expression, which are involved in the apoptosis of liver cells. The findings of the present study will further the investigation of the 7-mer peptide as an effective therapeutic agent in hepatic I-R injury.

Impact of alanyl-glutamine dipeptide on proliferative and inflammatory changes in jejunal mucosa after acute mesenteric ischemia

PURPOSE

The aim of our study was to determinate the impact of dipeptide (alanyl-glutamine) administration on inflammatory and proliferative changes in jejunal mucosa after acute mesenteric ischemia.

METHODS

Male Wistar rats (n=30) were divided into three groups: ischemia/reperfusion (IR) group which undergoes 60min of mesenteric ischemia and 1 or 24h of reperfusion (IR1, IR24, n=12). Groups with dipeptide administration (D+IR1, D+IR24, Dipeptiven con inf., i.v., 0.75 g/kg) prior to IR injury were followed by 1 and 24h of reperfusion. At the end of reperfusion period jejunal bioptic samples were obtained for histological (H&E), histochemical (Alcian blue) and immunohistochemical (anti-PCNA, anti-MPO) evaluations.

RESULTS

Our results pointed out a significant (p<0.001) increase of histopathological injury score in IR1 group compared to D+IR1 group. Immunohistochemical evaluation showed that MPO-positivity was significantly increased in IR groups after 1 (p<0.001) as well as 24h of reperfusion (p<0.01) compared to dipeptide pretreated groups. Proliferative/reparatory rate was assessed using anti-PCNA antibody and showed a significant increase (p<0.01) in PCNA cell positivity in lamina propria in dipeptide treated group compared to IR group.

CONCLUSION

In conclusion we may suggest that administration of alanyl-glutamine dipeptide prior to IR injury may help to protect small intestine and its mucous membrane integrity against insult such as intestinal ischemic/reperfusion injury presents.

Melatonin treatment protects liver of Zucker rats after ischemia/reperfusion by diminishing oxidative stress and apoptosis

Fatty livers occur in up to 20% of potential liver donors and increase cellular injury during the ischemia/reperfusion phase, so any intervention that could enable a better outcome of grafts for liver transplantation would be very useful. The effect of melatonin on liver ischemia/reperfusion injury in a rat model of obesity and hepatic steatosis has been investigated. Forty fa/fa Zucker rats were divided in 4 groups. 3 groups were subjected to 35 min of warm hepatic ischemia and 36 h of reperfusion. One experimental group remained untreated and 2 were given 10mg/kg melatonin intraperitoneally or orally. Another group was sham-operated. Plasma ALT, AST and hepatic content of ATP, MDA, hydroxyalkenals, NOx metabolites, antioxidant enzyme activity, caspase-9 and DNA fragmentation were determined in the liver. The expression of iNOS, eNOS, Bcl2, Bax, Bad and AIF were determined by RT-PCR Melatonin was effective at decreasing liver injury by both ways as assessed by liver transaminases, markers of apoptosis, of oxidative stress and improved liver ATP content. Melatonin administration decreased the activities or levels of most of the parameters measured in a beneficial way, and our study identified also some of the mechanisms of protection. We conclude that administration of melatonin improved liver function, as well as markers of pro/antioxidant status and apoptosis following ischemia/reperfusion in obese rats with fatty liver. These data suggest that this substance could improve outcome in patients undergoing liver transplantation who receive a fatty liver implant and suggest the need of clinical trials with it in liver transplantation.

Ameliorative effect of supplementation with L-glutamine on oxidative stress, DNA damage, cell viability and hepatotoxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat hepatocyte cultures

The most potent of the dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is a persistent and ubiquitous environmental contaminant. And the health impact of exposure to TCDD is of great concern to the general public. Recent data indicate that L-glutamine (Gln) has antioxidant properties and may influence hepatotoxicity. The objective of the present study was undertaken to explore the effectiveness of Gln in alleviating the hepatotoxicity of TCDD on primary cultured rat hepatocytes. Gln (0.5, 1 and 2 mM) was added to cultures alone or simultaneously with TCDD (0.005 and 0.01 mM). The hepatocytes were treated with TCDD and Gln for 48 h. Then cell viability was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC), total glutathione (TGSH) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by liver micronucleus assay (MN) and 8-oxo-2-deoxyguanosine (8-OH-dG). The results of MTT and LDH assays showed that TCDD decreased cell viability but not L-glutamine. TCDD also increased TOS level in rat hepatocytes and significantly decreased TAC and TGSH levels. On the basis of increasing doses, the dioxin in a dose-dependent manner caused significant increases of micronucleated hepatocytes (MNHEPs) and 8-OH-dG as compared to control culture. Whereas, in cultures exposured with Gln alone, TOS levels were not changed and TAC and TGSH together were significantly increased in dose-dependent fashion. The presence of Gln with TCDD modulated the hepatotoxic effects of TCDD on primary hepatocytes cultures. Noteworthy, Gln has a protective effect against TCDD-mediated DNA damages. As conclusion, we reported here an increased potential therapeutic significance of L-glutamine in TCDD-mediated hepatic injury for the first time.

17β-estradiol attenuates reduced-size hepatic ischemia/reperfusion injury by inhibition apoptosis via mitochondrial pathway in rats

The aim of this study was to investigate the effect of 17β-estradiol (E2) on hepatocyte apoptosis after reduced-size hepatic ischemia/reperfusion (I/R) injury and its mechanism. A rat model of reduced-size hepatic I/R injury was established. Sprague-Dawley rats were randomly allocated into sham, I/R, and E2 + I/R group. 17β-Estradiol (4 mg/kg) or the vehicle was administered i.p. 1 h before ischemia and immediately after operation. For each group, 10 rats were used to investigate the survival during a week after reperfusion. Blood samples and liver tissues were obtained in the remaining animals after 3, 6, 12, and 24 h of reperfusion to assess serum aspartate aminotransferase and alanine aminotransferase levels, liver tissue malondialdehyde concentration, superoxide dismutase activity, and histopathologic changes. Apoptosis ratio; expression of cytochrome c, Bcl-2, and Bax proteins; and enzymatic activities of caspase 9 and caspase 3 were performed in the samples at 12 h after reperfusion. The serum aspartate aminotransferase and alanine aminotransferase levels and tissue malondialdehyde concentration were increased in the I/R group, whereas the increase was significantly reduced by E2. The superoxide dismutase activity, depressed by I/R injury, was elevated back to normal levels by treatment with E2. Severe hepatic damage was observed by light microscopy in the I/R group, whereas administration of E2 resulted in tissue and cellular preservation. Furthermore, E2 inhibited hepatocellular apoptosis by upregulating the ratio of Bcl-2 and Bax expression, reduced cytosolic cytochrome c level, and decreased caspase 9 and caspase 3 activities. The 7-day survival rate was significantly higher in the E2 + I/R group than in the I/R group. These results indicated that E2 protects liver tissues from reduced-size hepatic I/R injury by suppressing mitochondrial apoptotic pathways.

Age-related differences in hepatic ischemia/reperfusion: gene activation, liver injury, and protective effect of melatonin

BACKGROUND

Ischemia/reperfusion (I/R) causes functional and structural damage to liver cells, this being more pronounced with increasing age of the tissue. Melatonin is a pineal indole that has been shown to play an important role as a free radical scavenger and anti-inflammatory molecule.

MATERIAL AND METHODS

The age-dependent responses to I/R were compared in 2-mo-old and 14-mo-old male Wistar rats. After 35 min of hepatic ischemia followed by 36 h of reperfusion, rats were sacrificed. Sham-operated control rats underwent the same protocol without real vascular occlusion. Animals were intraperitoneally injected with 10 mg/kg melatonin 24 h before the operation, at the time of surgery, and 12 and 24 h after it. The tissues were submitted to histopathologic evaluation. The levels of ALT and AST were analyzed in plasma. The expression of TNF-α, IL-1β, IL-10, MCP-1, IFN-γ, iNOS, eNOS, Bad, Bax, Bcl2, AIF, PCNA, and NFKB1 genes were detected by RT-PCR in hepatic tissue.

RESULTS

I/R was associated with significant increases in the expression of pro-inflammatory and pro-apoptotic genes in liver. Older rats submitted to I/R were found to respond with increased liver damage as compared with young rats, with serum ALT and AST levels significantly higher than in young animals. Mature rats also showed more evident increases in expression of pro-inflammatory cytokines (IL-1β, MCP-1, and IFN-γ) as well as a decrease in the mRNA expression of IL-10 as compared with young animals. Pro-apoptotic genes (Bax, Bad, and AIF) were significantly enhanced in liver after I/R, without differences between young and mature animals. However, the expression of Bcl2 gene did not show any change. Melatonin treatment was able to lower the expression of pro-inflammatory cytokines and pro-apoptotic genes and to improve liver function, as indicated by normalization of plasma AST and ALT levels and by reduction of necrosis and microsteatosis areas.

CONCLUSIONS

Melatonin treatment was able to reduce the I/R-stimulated pro-inflammatory and pro-apoptotic genes in the rat liver. Since older animals showed a more marked increase in inflammation and in liver injury, the treatment was more effective in those subjects.

Effect of glutamine on the total antioxidant system of rats subjected to renal ischemia and reperfusion

PURPOSE: To evaluate the protective effects of glutamine administered before renal ischemia-reperfusion on plasma antioxidant protection, and lung and renal tissue injury. METHODS: 33 rats underwent right nephrectomy. On the eighth postoperative day, animals were randomized into three groups (n=11): glutamine, control and sham. Each group of animals received, by gavage, a particular diet for 7 days. On day 14 following nephrectomy, the animals were subjected to left renal ischemia-reperfusion. After this, blood samples were collected and the animals were killed. At necropsy the kidney and lung were removed for histology. RESULTS: The levels of total antioxidant capacity were higher in the glutamine group and control group compared with the sham group. The levels of glutathione peroxidase in both the sham and glutamine groups were higher when compared with the control group (p<0.05). The level of superoxide dismutase in the sham group was clearly higher than that in the glutamine and control groups. Histological examination showed no differences between the three groups. CONCLUSION: Prior intake of glutamine improves total antioxidant capacity and increases glutathione peroxidase levels in rats subjected to renal ischemia-reperfusion.

Modulatory effect of l-glutamine on 2,3,7,8 tetrachlorodibenzo-p-dioxin-induced liver injury in rats

The aim of this study was to explore the effectiveness of l-glutamine (Gln) in alleviating the toxicity of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in liver of rats. Rats were intraperitoneally administered Gln and TCDD doses daily for 21 days. In the liver of rats, the biochemical tests, pathological examination and micronucleus (MN) test were performed. TCDD significantly decreased the activities of antioxidant enzymes and serious pathological findings. Moreover, the rate of MNs in hepatocytes increased after treatment with dioxin. In rats treated with Gln alone, the MNs remained unchanged, but the ratio of glutathione (GSH) and the activity of glutathione peroxidase (GSH-Px) were significantly increased. Gln also prevented the suppression of GSH-Px (except for superoxide dismutase and catalase) and GSH in the livers of animals exposed to TCDD and displayed a strong protective effect against MNs. Thus, our findings for Gln might provide new insight into the development of therapeutic and preventive approaches in TCDD toxicity.

Protective effects of glutamine preconditioning on ischemia-reperfusion injury in rats

BACKGROUND

Hepatic ischemia-reperfusion injury is a common phenomenon in hepatic surgical procedures and can result in further severe damage. This study aimed to investigate the protective effects of glutamine preconditioning on hepatic ischemia-reperfusion injury in rats and its dose-dependency.

METHODS

Thirty-two healthy male Wistar rats were randomly divided into four groups (n=8 per group). One group received 0.9% NaCl (control) and the other three received glutamine (Gln groups) 4 hours before ischemia. The Gln groups were named GL, GM, and GH according to the glutamine dose. The liver was subjected to 1 hour of ischemia and 2 hours of reperfusion. Two hours later, the levels of alanine aminotransferase (ALT), intracellular free calcium (Ca2+), and activity of Na+/K+ adenosine triphosphatase (ATPase) and superoxide dismutase (SOD) were assessed, and liver tissue sections were examined under a microscope.

RESULTS

The Gln and control groups differed in the concentration of intracellular free calcium (P<0.05), and the activity of Na+/K+ ATPase and SOD in the Gln groups was higher than in the control group (P<0.05). The ALT level was lower in the GM and GH groups than in the control group (P<0.05). The levels of Na+/K+ ATPase and SOD rose gradually with increasing glutamine dose (P<0.05), and the concentration of Ca2+ declined gradually with increasing glutamine dose (P<0.05). The degree of hepatocyte injury was milder in the Gln groups than in the control group.

CONCLUSIONS

Glutamine preconditioning protected effectively against hepatic ischemia-reperfusion injury. These protective effects were related to the dose of glutamine and due to the reduction of intracellular calcium overload and the improvements in the activity of Na+/K+ ATPase and SOD.

Preconditioning with L-alanyl-L-glutamine in a Mongolian Gerbil model of acute cerebral ischemia/reperfusion injury

PURPOSE: To investigate the effect of L-alanyl-L-glutamine (L-Ala-Gln) preconditioning in an acute cerebral ischemia/reperfusion (I/R) model in gerbils. METHODS: Thirty-six Mongolian gerbils (Meriones unguiculatus), (60-100g), were randomized in 2 groups (n=18) and preconditioned with saline 2.0 ml (Group-S) or 0.75g/Kg of L-Ala-Gln, (Group-G) administered into the femoral vein 30 minutes prior to I/R. Each group was divided into three subgroups (n=6). Anesthetized animals (urethane, 1.5g/Kg, i.p.) were submitted to bilateral occlusion of common carotid arteries during 15 minutes. Samples (brain tissue and arterial blood) were collected at the end of ischemia (T0) and after 30 (T30) and 60 minutes (T60) for glucose, lactate, myeloperoxidase (MPO), thiobarbituric acid reactive substances (TBARS), glutathione (GSH) assays and histopathological evaluation. RESULTS: Glucose and lactate levels were not different in studied groups. However glycemia increased significantly in saline groups at the end of the reperfusion period. TBARS levels were significantly different, comparing treated (Group-G) and control group after 30 minutes of reperfusion (p<0.05) in cerebral tissue. Pretreatment with L-Ala-Gln promoted a significant increase in cerebral GSH contents in Group-G at T30 (p<0.001) time-point compared with Group-S. At T30 and T60, increased levels of GSH occurred in both time-points. There were no group differences regarding MPO levels. Pyknosis, presence of red neurons and intracellular edema were significantly smaller in Group-G. CONCLUSION: Preconditioning with L-Ala-Gln in gerbils submitted to cerebral ischemia/reperfusion reduces oxidative stress and degeneration of the nucleus (pyknosis) and cell death (red neurons) in the cerebral tissue.

Attenuation of warm ischemia-reperfusion injury in the liver by bucillamine through decreased neutrophil activation and Bax/Bcl-2 modulation

BACKGROUND AND AIM

Liver transplantation and resection surgery involve a period of ischemia and reperfusion to the liver, which initiates an inflammatory cascade resulting in liver and remote organ injury. Bucillamine is a low molecular weight thiol antioxidant that is capable of rapidly entering cells. We hypothesized that bucillamine acts by replenishing glutathione levels, thus reducing neutrophil activation, modulating Bax/Bcl-2 expression, and subsequently, attenuating the effects of warm ischemia-reperfusion injury (IRI) in the liver.

METHODS

The effect of bucillamine was studied in a rat model of liver IRI with 45 min of partial (70%) liver ischemia and 3 h of reperfusion. Liver injury was assessed by measuring serum transaminases (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]) and liver histology. Oxidative stress was quantified by measuring F(2) isoprostane and glutathione levels. Leukocyte adhesion was assessed by intravital microscopy, and inflammatory cytokine response was assessed by measuring serum cytokine-induced neutrophil chemoattractant-1 (CINC-1) levels. Bax and Bcl-2 expression was measured by reverse transcription-polymerase chain reaction.

RESULTS

The model produced significant liver injury with elevated transaminases and an acute inflammatory response. Bucillamine reduced the liver injury, as indicated by reduced AST (932 ± 200.8 vs 2072.5 ± 511.79, P < 0.05). Bucillamine reduced Bax expression, serum CINC-1 levels, and neutrophil adhesion, and upregulated Bcl-2. However, bucillamine did not affect tissue glutathione levels nor the levels of oxidative stress, as measured by plasma and hepatic F(2) isoprostane levels.

CONCLUSIONS

Bucillamine reduces warm ischemia-reperfusion in the liver by inhibiting neutrophil activation and modulating Bax/Bcl-2 expression.

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.

Glutamine attenuates lipopolysaccharide-induced acute lung injury

OBJECTIVES

It has been reported that glutamine (GLN) can attenuate acute lung injury after sepsis. GLN is also thought to be a precursor of glutathione (GSH) synthesis. Using the GSH synthesis blocker, L-buthionine-(S,R)-sulfoximine (BSO), we investigated the role of GSH synthesis in the protective effect of GLN on acute lung injury.

METHODS

In this study, we used an acute lung injury model induced by intratracheal injection of lipopolysaccharide (1 mg mL(-1) kg(-1)). GLN (0.75 g/kg, intravenous) and BSO (2 mmol/kg, intraperitoneal) were administrated simultaneously. At 2 and 18 h after the injections, the rats were sacrificed by right ventricular puncture and bronchoalveolar lavage was done. The lower right lung was excised for histologic examination. Total protein concentration and total cell and neutrophil counts in the bronchoalveolar lavage fluid were determined. CD11b expression in the blood was determined by flow cytometry. We also analyzed myeloperoxidase activity, and GSH and interleukin-8 levels in lung tissues.

RESULTS

GLN supplementation reduced the total protein concentration and total cell and neutrophils counts in bronchoalveolar lavage fluid after lipopolysaccharide challenge. GLN enhanced GSH synthesis and attenuated interleukin-8 release and myeloperoxidase activity in lung tissues. GLN also decreased CD11b expression in blood neutrophils and prevented lung histologic changes. BSO abolished the effects of GLN and attenuated its protection on acute lung injury.

CONCLUSION

These results indicate that GLN could prevent neutrophil recruitment and infiltration, protect the alveolar barrier, and attenuate inflammatory injury during sepsis. This effect may be related to enhanced GSH synthesis.

Short-term alanyl-glutamine dipeptide pretreatment in liver ischemia–reperfusion model: Effects on microcirculation and antioxidant status in rats

BACKGROUND & AIMS

Ischemia-reperfusion (I-R) injury is responsible for the morbidity associated with liver surgery. Production of toxic free radicals influences the microcirculation. The aim of our study was to examine the effect of glutamine (Gln) supplementation--adminstered in alanyl-glutamine dipeptide form--on liver function, immuno/histopathology and the oxidative state of the liver after injury.

METHODS

Two-hundred and fifty grams male Wistar rats underwent normothermic, 60 min, segmental liver ischemia followed by 6 h of reperfusion. The animals (n = 45) were divided into three groups: sham operated, I-R and parenteral Gln pretreatment. Hepatic microcirculation was monitored by laser Doppler flowmetry. At the 6 h of reperfusion, histological alterations, TUNEL reaction, active caspase-3 reaction, serum and liver tissue antioxidant levels, serum ALAT, ASAT and TNF-alpha levels were measured.

RESULTS

Upon reperfusion, the Gln group had significantly (p<0.05) higher flow rates than the I-R group and, at the end of the 6h of reperfusion, significantly (p<0.05) lower serum ALAT and ASAT levels. The liver chemiluminescent intensity was lower, free SH-groups were elevated, while the reducing power was decreased in the Gln-pretreated group. Positive staining for caspase-3 after Gln pretreatment was significantly increased in contrast to the control tissues.

CONCLUSION

Glutamine pretreatment is beneficial in supporting hepatic microcirculation and can prevent hepatocellular necrosis in liver reperfusion injury.