Effect of protease inhibitor on ischemia-reperfusion injury to rat liver

Changes in extra- and intracellular pH in hepatocytes exposed to gabexate mesilate

Gabexate mesilate (GM) is a synthetic inhibitor of plasmatic and pancreatic serine proteases licensed for the treatment of pancreatitis. Here we show that in suspensions of isolated hepatocytes, profound changes in extracellular, cytoplasmic, and vesicular pH occur after addition of GM. Isolated hepatocytes obtained by collagenase perfusion of rat liver were pre-incubated with 1, 2, and 4 mM GM. Extracellular pH (pH in the incubation medium) was measured by a conventional pH electrode, cytosolic and vesicular pH were measured by fluorescence changes of 2',7'-biscarboxyethyl-5,6-carboxyfluorescein acetoxymethyl ester (BCECF-AM) and fluorescein dextran, respectively. Incubation of hepatocytes with GM resulted in a dose-dependent decrease of extracellular pH. Cytosolic pH decreased rapidly and markedly in a dose-dependent manner during the first minutes and gradually returned towards baseline. Simultaneously, GM induced a rapid alkalinization of acidic vesicles. The presence of bis-(p-nitrophelyl) phosphate (BNPP), an esterase inhibitor, reduced the extent of extracellular acidification. Incubation of hepatocytes in the presence of dimethylamiloride, an Na+/H+ exchanger inhibitor, or in a sodium-free medium, did not modify the rate and extent of extracellular acidification. GM, a commercially available pharmacological agent, could be useful to manipulate extra- and intracellular pH.

Sivelestat sodium hydrate inhibits neutrophil migration to the vessel wall and suppresses hepatic ischemia-reperfusion injury

BACKGROUND

Sivelestat sodium hydrate (sivelestat) is a specific neutrophil elastase inhibitor that is effective in treating acute lung injury associated with systemic inflammatory response syndrome. As such, it may be useful in treating hepatic ischemia-reperfusion injury (IRI), a condition in which neutrophils transmigrate into the interstitium, leading to release of neutrophil elastase from neutrophils and consequent damage to the affected tissue, particularly in cases of hepatic failure after liver transplantation or massive liver resection.

AIMS

The purpose of this study was to examine whether treatment with sivelestat inhibits neutrophil adhesion and migration to the vessel wall and suppresses hepatic IRI.

METHODS

Whether and, if so, the extent to which sivelestat suppresses the adhesion and migration of neutrophils and reduces liver damage in hepatic IRI was examined in a human umbilical vein endothelial cell (HUVEC) model and a rat hepatic IRI model.

RESULTS

In the HUVEC model, the extent of the adhesion and migration of neutrophils stimulated by platelet-activating factor were found to be dose-dependently inhibited by sivelestat treatment (p < 0.05). In the rat model, serum liver enzyme levels were significantly lower at 12 h after reperfusion, and the number of neutrophils that had migrated to extravascular sites was significantly less in the treatment group compared to the control group (p < 0.05).

CONCLUSION

Sivelestat inhibits the adhesion and migration of neutrophils to vascular endothelium in hepatic IRI, thereby suppressing liver injury.

Regulating surgical oncotaxis to improve the outcomes in cancer patients

Excessive surgical stress and postoperative complications cause a storm of perioperative cytokine release, which has been shown to enhance tumor metastasis in experimental models. We have named this phenomenon "surgical oncotaxis". The mechanisms that underpin this process are thought to be excessive corticosteroid secretion, coagulopathy in the peripheral vasculature, immune suppression and excessive production of reactive oxygen species. Nuclear factor-kappa B (NFkB) activation plays a key role in these mechanisms. Minimally invasive surgical techniques should be used, and postoperative complications should be avoided whenever possible to lessen the impact of surgical oncotaxis. Furthermore, there may be a role for a small preoperative dose of corticosteroid or the use of free radical scavengers in the perioperative period. Recently, there has been a great deal of interest in omega-3 fatty acid, because it regulates NFkB activation. The use of multimodal treatments that regulate surgical oncotaxis may be as important as chemotherapy for determining the outcome of patients with cancer undergoing surgery.

Effect of portal vein occlusion on the pancreas: an experimental model

BACKGROUND

The effects of portal vein occlusion on the pancreas are not clearly understood. Therefore, we studied histomorphological changes induced in the rat pancreas by various periods of portal vein occlusion.

MATERIALS AND METHODS

Sixty female Wistar albino rats were randomly allocated into four groups of 15 each. In Group I (control), rats underwent sham laparotomy to expose the portal vein proximal to its bifurcation. In Groups II-IV, rats underwent laparotomy followed by portal vein occlusion by clamping for 15, 30, and 60 minutes respectively. The pancreas was removed immediately after sham laparotomy in Group I and immediately after clamp release in Groups II-IV. Pancreatic tissue specimens were subjected to histochemical analysis for cell typing and diagnosis, immunohistochemical analysis for identification of the inflammatory markers tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), endothelial nitric oxide synthase (eNOS), and inducible NOS (iNOS), and TUNEL analysis was carried out for identification of apoptotic cells.

RESULTS

Histochemistry revealed signs of inflammation in pancreatic tissue from rats subjected to portal vein occlusion. Immunohistochemistry revealed that the expression of proinflammatory cytokines TNF-alpha and IL-1beta and the oxidative damage indicator iNOS in rat pancreatic tissue increased progressively with the duration of portal vein occlusion. TUNEL assay revealed no signs of apoptosis in any of the groups.

CONCLUSION

We conclude that portal vein occlusion triggers an inflammatory response in the pancreas that worsens the longer the occlusion lasts.

Effects of dietary supplements on the space radiation-induced reduction in total antioxidant status in CBA mice

In the present study, the total antioxidant status was used as a biomarker to evaluate oxidative stress induced by proton, HZE-particle and gamma radiation in CBA mice. The results demonstrated that the plasma level of TAS was significantly decreased (P < 0.05) in CBA mice after exposure to a 50-cGy dose of radiation from HZE particles or a 3-Gy dose of radiation from protons or gamma rays. Diet supplementation with Bowman-Birk Inhibitor Concentrate (BBIC), L-selenomethionine (L-SeM), or a combination of N-acetyl cysteine, sodium ascorbate, co-enzyme Q10 (CoQ10), alpha-lipoic acid, L-SeM and vitamin E succinate could partially or completely prevent the reduction in the plasma level of TAS in CBA mice exposed to proton or HZE-particle radiation. The selected antioxidant combination with or without CoQ10 has a comparable protective effect on the gamma-radiation-induced drop in TAS in CBA mice. These results indicate that BBIC, L-SeM and the selected antioxidant combinations may serve as countermeasures for space radiation-induced adverse biological effects.

Effects of gabexate mesilate on ischemia-reperfusion-induced testicular injury in rats

The aim of this study was to determine the effects of a synthetic serine protease inhibitor, gabexate mesilate (GM), in rats with ischemia-reperfusion (I-R) damage due to unilateral testicular torsion. Thirty male Sprague-Dawley rats were separated into three groups, each containing ten rats. A sham operation was performed in group 1 (control). In group 2 (I-R/untreated), 1 h detorsion of the testis was performed after 6 h of unilateral testicular torsion. In group 3 (I-R/GM), after performing the same surgical procedures as in group II, gabexate mesilate was given intravenously. In all experimental rats, ipsilateral orchiectomies were performed for histological examination and measuring the tissue levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). MDA values and the testicular injury score decreased and SOD, CAT and GSH-Px values increased in the GM-treated group compared to the I-R/untreated group. The Tc-99m pertechnetate uptake ratio and the perfusion index were significantly decreased in the group 2 compared to the group 1 and 3 rats. In group 3, these values were significantly increased compared to group 2. Most of the specimens in the GM-treated group showed grade-I testicular injury. However, the injuries in the I-R/untreated rats varied between grade-III and grade-IV. The results of this study show that GM may play a role in reducing the injury caused by I-R.

Evaluation of a protease inhibitor in the prevention of ischemia and reperfusion injury in hepatectomy under intermittent Pringle maneuver

BACKGROUND

The severity of ischemia and reperfusion (I/R) injury is an important determinant of patient outcome in hepatic surgery. The aim of this study was to investigate the efficacy of a protease inhibitor in alleviating I/R injury to human liver in the setting of hepatectomy under intermittent Pringle maneuver.

METHODS

Sixty patients who underwent liver resection under conditions of intermittent inflow occlusion were randomly assigned to 2 groups (n = 30 each) according to the use of a synthetic protease inhibitor (gabexate mesilate or GM). GM was administered intravenously at a dosage of 2.0 mg/kg/h starting 12 hours before surgery until postoperative day 2. Preoperative and intraoperative clinical variables and postoperative outcomes were evaluated. The plasma levels of a cytokine, interleukin (IL)-6, as well as laboratory biochemical liver function parameters were analyzed to evaluate hepatic I/R injury.

RESULTS

The 2 groups of patients were comparable with regard to hepatic inflow occlusion time, extent of liver resection, and background liver histology. The preoperative administration of GM (GM group) substantially alleviated hepatic I/R injury compared with the untreated control group; postoperative serum transaminase levels were significantly decreased in association with marked suppression of IL-6 levels in blood circulation during surgery. This was accompanied by a lower incidence of postoperative complications. The patients without postoperative complications had significantly lower activities of plasma IL-6 at 24 hours after surgery.

CONCLUSIONS

This prospective randomized study demonstrated the hepatoprotective effect of a synthetic protease inhibitor in the setting of hepatectomy under the intermittent Pringle maneuver.

Effect of synthetic protease inhibitor gabexate mesilate on the attenuation of ischemia/reperfusion injury in canine kidney autotransplantation

BACKGROUND

Kidneys from non-heart-beating donors are associated with delayed graft function and a high rejection rate due to the long period of warm ischemia. Gabexate mesilate (GM), a synthetic serine protease inhibitor, has been shown to improve organ function by suppressing cytokine activity and neutrophil function after ischemia/reperfusion. In this study, we evaluated the effect of GM on renal function after warm ischemia in a canine kidney autotransplantation model.

METHODS

After 60 minutes of warm ischemia, the left kidney was transplanted into the iliac fossa, and the right kidney was removed. The control group (n = 7) and GM group (n = 7) were evaluated for serum creatinine and blood urea nitrogen (BUN) concentrations, renal tissue blood flow, resistive index, pulsatility index, interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha mRNA expression levels in peripheral blood mononuclear cells, apoptotic index, CD10 immunolabeling as an indicator of brush border injury, and standard histopathology.

RESULTS

Compared with controls, administration of GM resulted in lower serum creatinine concentrations (11.3 +/- 2.4 vs 5.2 +/- 3.3 mg/dL at 72 hours; P = .04) and BUN concentrations (188 +/- 26 mg/dL vs 98 +/- 41 mg/dL at 72 hours; P = .04), as well as better tissue blood flow, improvement of brush border injury and apoptotic index (each P < .05). The expression of IL-1beta and TNF-alpha mRNA did not change after administration of GM.

CONCLUSIONS

The present study shows that GM protected renal function after warm ischemia/reperfusion by inhibition of serine proteases, maintenance of tissue blood flow, and amelioration of tubular apoptosis.

Commonly consumed and naturally occurring dietary substances affect biomarkers of oxidative stress and DNA damage in healthy rats

The influence of black currant juice, Bowman-Birk protease inhibitor (BBI), kolaviron (a biflavonoid fraction of Garcinia kola seed), sugars, vitamin C and tert-butyl hydroperoxide on a wide range of biomarkers for oxidative stress, DNA damage and sugar or lipid metabolism has been investigated in male F 344 rats. The selected pro-oxidant control, tert-butyl hydroperoxide, significantly increased plasma and liver 2-amino-adipic semialdehyde (AAS), a marker of protein oxidation (p <0.05) whereas lipid oxidation assessed as malon dialdehyde (MDA) and DNA oxidation were not significantly increased. Feeding BBI also increased the level of oxidized protein in plasma and liver at the higher dose level (0.5%). No effect was observed at the lower dose level (0.25%), which even decreased lipid oxidation in plasma. BBI did not affect background levels of DNA strand breaks or oxidation (comets). In rats exposed to black currant juice, a statistically significant decrease in liver AAS and MDA was observed. This effect could not be explained by its content of sugars or of the known redox active constituent, vitamin C. The lowering effect of black currant juice on protein and lipid oxidation was similar in magnitude to that of the known liver protectant, kolaviron. In rats treated with kolaviron (200 mg/kg body weight), background AAS levels were significantly reduced in both plasma and liver whereas the effect on MDA only reached statistical significance in plasma. Kolaviron was the only extract tested which decreased oxidative damage to DNA in the liver. The erythrocyte antioxidant enzyme activities, catalase and glutathione peroxidase were decreased in rats treated with tert-butyl hydroperoxide (p <0.05) but were not affected by the other treatments. Black currant juice and sugars increased plasma triglyceride levels and black currant juice increased plasma cholesterol but neither of them nor any other treatment affected blood glucose, erythrocyte HbA1c or fructosamine. We conclude that markers of oxidative stress may be modified by several mechanisms after feeding rats with complex dietary factors and that both pro- and antioxidant effects may consequently be observed simultaneously after short-term feeding of antioxidant-rich foods, herb medicines, or known pro- and antioxidants.

Modulation of L-arginine transport and nitric oxide production by gabexate mesylate

Gabexate mesylate, a non-antigenic synthetic inhibitor of trypsin-like serine proteinases, is a drug used efficiently in the treatment of pancreatitis and disseminated intravascular coagulation and as a regional anticoagulant for haemodialysis. Considering the structural similarity between L-arginine and gabexate mesylate, the effect of this drug on L-arginine transport, nitric oxide (NO) formation and constitutive NO synthase activity in human platelets was investigated. Data have shown that gabexate mesylate inhibited competitively L-arginine uptake by increasing the K(m) value from 22+/-2 to 86+/-6 microM. The K(i) value was 158 microM at pH 7.4 and 37 degrees. Furthermore, gabexate mesylate decreased dose and time-dependent nitrite and nitrate formation (NO(x) release) and cGMP accumulation in whole cells. In addition, gabexate mesylate inhibited constitutive nitric oxide synthase in a cell-free extract. We concluded that gabexate mesylate could be considered an effective modulator of cellular NO synthesis.

Hepatocyte protection by a protease inhibitor against ischemia/reperfusion injury of human liver

BACKGROUND

Total clamping of the hepatic pedicle can induce profound hepatic ischemia/reperfusion (I/R) injury, which remains a potentially lethal problem after hepatectomy.

STUDY DESIGN

The purpose of this study was to evaluate the efficacy of a protease inhibitor in ameliorating I/R injury of the human liver. In a prospective, randomized, clinical study, 66 patients who underwent liver resection under conditions of continuous inflow occlusion were randomly assigned to three groups: 25 patients were given a synthetic protease inhibitor (gabexate mesilate [GM], 2.0 mg/kg/hr) intravenously starting 24 hours before surgery until postoperative day 3 (preop GM group); 16 were similarly given GM at the beginning of surgery (intraop GM group); and 25 served as controls (without GM group). Laboratory data and intraoperative and postoperative variables were analyzed and plasma levels of cytokines--tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6)--were measured to determine the relationship between surgical stress and hepatic I/R injury.

RESULTS

The three groups of patients were similar in terms of age, gender, preoperative assessments, hepatic inflow occlusion time (approximately 50 minutes), extent of resection (proportion of major and minor hepatectomy), and background liver conditions. Preoperative administration of gabexate mesilate (preop GM group) substantially ameliorated hepatic I/R injury as compared with the other patients (intraop and without GM groups); postoperative serum transaminase levels were notably decreased in association with marked suppression of IL-6 levels in blood circulation during liver surgery. This was accompanied by a lower rate of postoperative complications and no mortality. Gabexate mesilate pretreatment abrogated the positive correlation between postreperfusion hepatocyte injury and hepatic ischemia time.

CONCLUSIONS

Preoperative administration of GM is useful for preventing I/R injury of the human liver, accompanied by suppression of the plasma proinflammatory cytokine IL-6.

Kupffer cells protect liver from ischemia-reperfusion injury by an inducible nitric oxide synthase-dependent mechanism

The aim of this study was to investigate the role of nitric oxide (NO) in rat hepatic ischemia-reperfusion (I/R) injury. Animals were divided into four groups: Group I, control; Group II, gadolinium chloride (GdCl3), a Kupffer cell depleting agent, pretreated; Group III, S-methylisothiourea (SMT), a potent inducible NO synthase (iNOS) inhibitor, pretreated; Group IV, pretreated with SMT, then treated with S-Nitroso-N-acetylpenicillamine (SNAP), a NO donor, after ischemia. Sprague-Dawley rats underwent left lateral and median lobe ischemia for 60 min and reperfusion for 120 min. The left lateral and median lobes were used as ischemic lobes, and the right lateral lobe in the same rat was used as a control lobe. The total NOS (tNOS), iNOS, constitutive NOS (cNOS) activity, and liver protein were determined. The liver tissue malonaldehyde (MDA) level was measured as an index of lipid peroxidation. Liver histology was also examined. The liver tNOS activity in ischemic lobes of Group I, II, III, and IV was increased by 214%, 86%, 61%, and 45%, respectively. The increase in tNOS activity is mainly due to the induction of iNOS activity in the ischemic lobes of rat liver. GdCl3 significantly decreased the tNOS by 66% in the ischemic lobes. GdCl3 significantly increased MDA by 39% in the ischemic lobes. SMT significantly decreased tNOS and iNOS activity by 66% and 85% in ischemic lobes. SMT increased MDA by 67% in the ischemic lobes. SMT + SNAP treatment increased iNOS activity by 117% in the ischemic lobes in comparison with the ischemic lobes of the SMT group. SMT + SNAP treatment decreased MDA by 39% in the ischemic lobes. SMT + SNAP treatment also decreased the sinusoidal congestion and spotty necrosis of hepatocytes in the ischemic lobes. iNOS immunostaining showed an obvious increase in sinusodial area of the ischemic lobes where most Kupffer cells were interspersed. In conclusion, in this model of liver I/R injury, I/R increased the activity of tNOS and iNOS, but not the cNOS activity. Kupffer cells might be the major source of the induction of iNOS activity. The iNOS specific inhibitor SMT increased the lipid peroxidation and the tissue damage in hepatic I/R injury. On the contrary, the NO donor SNAP increased the activity of iNOS and decreased the hepatic injury in this study. Kupffer cells could protect liver from I/R injury by an iNOS-dependent mechanism, thus NO production has a beneficial role in hepatic IR injury.