Maeng Bong Jin

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

Abstract 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.

Attenuation of ischemic liver injury by augmentation of endogenous adenosine

Hepatic grafts from non-heartbeating donors may alleviate the organ shortage, but they inherently suffer from warm ischemia. In the present study, we tested our hypothesis that augmentation of endogenous adenosine by inhibition of nucleoside transport with R75231 attenuates ischemic liver injury. Adult female beagle dogs underwent 2-hr hepatic vascular exclusion with venovenous bypass. R75231 was given to the animals by continuous intravenous infusion for 30 min before ischemia at a dose of 0.1 mg/kg (Group 2, n=6), 0.05 mg/kg (Group 3, n=6), or 0.025 mg/kg (Group 4, n=6). Nontreated animals were used as the control (Group 1, n= 10). Animal survival, hepatic tissue blood flow, liver function, and histopathology were analyzed. Two-week animal survival was 30% in Group 1, 83% in Group 2, 100% in Group 3, and 100% in Group 4. Postreperfusion hepatic tissue blood flow was markedly improved by the treatment. Treatment significantly attenuated liver enzyme release, lipid peroxidation, and changes in adenine nucleotides and purine catabolites. Structural abnormality of the liver after reperfusion was markedly improved by R75231 treatment, showing better architecture and less neutrophil infiltration. Preischemic administration of a nucleoside transport inhibitor ameliorated ischemic liver injury due to the positive effects of augmented endogenous adenosine, and is applicable clinically when the liver is procured from a controlled non-heartbeating donor.

Prolongation of canine liver allograft survival by a novel immunosuppressant, FTY720. Effect of monotherapy and combined treatment with conventional drugs

BACKGROUND The immunosuppressive effect and other properties of a novel immunosuppressant, FTY720, have been studied mostly in the experimental transplantation of various extrahepatic organs. In this experiment, we evaluated the antirejection potency and adverse effects of this agent on liver grafts using a canine liver transplantation model. METHODS Forty-eight orthotopic liver transplantations were performed by the standard technique under a veno-venous bypass. Liver recipients were divided into two studies: a single-dose study with FTY720 at various doses and a combined dose study with conventional immunosuppressants (cyclosporine or tacrolimus) alone and combined with FTY720. Survival, biochemical and hematological tests, blood levels of immunosuppressants, and postmortem histology were determined. RESULTS The median survival of untreated control animals was 9 days, whereas treatment with FTY720 at a dose of 0.1 mg/kg/day prolonged graft survival to 49.5 days. FTY720 at 1 mg/kg/day showed a slight but insignificant prolongation to 16 days, but when the dose was increased to 5 mg/kg/day, the graft was rejected at 10 days. The combination of FTY720, 0.1 mg/kg/day, with a subtherapeutic dose of cyclosporine, 5 mg/kg/ day, prolonged median animal survival from 40 days with cyclosporine alone to 74 days. A combination of FTY720 (0.1 mg/kg/day) with tacrolimus (0.5 mg/kg/ day) compromised animal survival, reducing survival from 83.5 days with tacrolimus alone to 30.5 days due to infectious complication and emaciation by overimmunosuppression. No evident drug-induced side effects were observed. CONCLUSIONS FTY720 has a potent immunosuppressive effect when used alone at 0.1 mg/kg/day in canine liver transplantation. FTY720 is a promising candidate for future clinical application in orthotopic liver transplantation.

Protective effect of angiotensin II type I receptor antagonist, CV-11974, on ischemia and reperfusion injury of the liver

BACKGROUND Microcirculatory disturbance has been shown to play a critical role in hepatic ischemia and reperfusion (I/R) injury. Angiotensin II (AngII) is one of the most potent endogenous vasoconstrictors. Angiotensin II type I (AT1) receptor antagonist has been reported to have protective effects on I/R injury of the heart and kidney. However, effect on hepatic I/R injury has not been determined. In this study, we investigate our hypothesis that AT1 receptor antagonist, CV-11974, attenuates hepatic I/R injury. METHODS Twelve beagle dogs underwent a 2-hr total hepatic vascular exclusion with veno-venous bypass. CV-11974 was given to animals at a dose of 0.002 mg/ kg/min for 5 min followed by 0.001 mg/kg/min for 25 min via portal vein before ischemia (group II, n=6). Nontreated animals were used as the control (group I, n=6). Animal survival, hemodynamics, hepatic tissue blood flow (HTBF), liver function, platelet count, renin activity, and AngII concentration of hepatic vein, energy metabolism, and histopathology were analyzed. RESULTS Two-week survival was 33% in group I, in contrast, 100% in group II. Mean arterial blood pressure during early reperfusion was maintained, and HTBF after reperfusion was significantly higher in group II. Treatment attenuated liver enzyme release and decrease of platelet count, increased renin and AngII, suppressed ATP degradation during ischemia and enhanced ATP resynthesis after reperfusion. Neutrophil infiltration and histopathological damages were lessened in group II. CONCLUSIONS Our data demonstrated that the local renin-angiotensin system might play a role in hepatic microcirculation. AT1 receptor blockade with CV-11974 attenuated hepatic microcirculatory disturbance and ameliorated I/R injury.

Attenuation of ischemia and reperfusion injury of canine livers by inhibition of type II phospholipase A2 with LY329722.

Background. Membrane phospholipid breakdown, caused by ischemia and reperfusion (I/R) of the liver, releases free fatty acids including arachidonic acids and lysophospholipids, which serve as precursors of various inflammatory lipid derivatives. Phospholipase A2 (PLA2) is a key enzyme that initiates this reaction. In this study, we tested our hypothesis that a type II PLA2 inhibitor, LY329722, could attenuate hepatic I/R injury caused by a 2-hr total hepatic vascular exclusion (THVE) in dogs. Methods. Eighteen beagle dogs, subjected to a 2-hr THVE, were divided into three groups. Group 1 (n=6) was untreated and served as a control group. LY329722 was administered to animals in group 2 (n=6) intravenously (0.2 mg·kg−1·hr−1) for 60 min before ischemia, and to animals in group 3 (n=6) for 60 min starting 15 min before reperfusion (0.2 mg·kg−1·hr−1). Animal survival, systemic and splanchnic hemodynamics, hepatic tissue blood flow, liver functions, energy metabolism, hepatic venous thromboxane B2 and endothelin-1 levels, phospholipid levels and tumor necrosis factor-&agr; mRNA expression in liver tissue, and histopathologic findings were evaluated. Results. Two-week animal survival was 33% (two of six) in group 1, and 100% (six of six) in groups 2 and 3. LY329722 improved systemic and splanchnic hemodynamics, hepatic tissue blood flow, and energy metabolism, reduced liver enzyme, thromboxane B2, and endothelin-1 release, prevented hepatic phospholipid degradation and tumor necrosis factor-&agr; mRNA expression, and lessened histopathologic damage and the number of neutrophil infiltrating into the liver tissue. Conclusion. The present study demonstrated that a type II PLA2 inhibitor, LY329722, attenuated hepatic I/R injury caused by a 2-hr THVE model in dogs.

The role of endothelin-1 in hepatic ischemia and reperfusion injury.

istration of Big ET-1, a precursor of ET-1, induced peripheral and coronary vasoconstriction, which was almost completely blocked by bosentan, a nonselective ET receptor antagonist. In addition, bosentan alone did not induce any significant hemodynamic changes in normal anesthetized dogs. According to these results, Teerlink and colleagues suggested that ET-1 does not play a crucial role in the normal hemodynamic condition. In pathological conditions, there are many reports indicating that impaired liver produced ET-1. The main sources of ET-1 in the injured liver are sinusoidal endothelial cells and stellate cells.7,8 We have already reported that, in a canine 2-h total hepatic vascular exclusion model, plasma ET-1 concentration in the hepatic vein was enhanced, leading to the elevation of peripheral plasma ET-1 concentration.9 In experimental series focused on hepatic ischemia and reperfusion injury, we revealed several therapeutic methods, such as the use of oxygen radical inhibitors,10,11 an adenosine transport inhibitor,12 a nitric oxide donor and precursor,13 prostaglandin E1 and I2 analogs,14 a phosphodiesterase III inhibitor,15 a phospholipase A2 inhibitor,16 and an angiotensin II type 1 receptor antagonist,17 to prevent ET-1 adverse effects on the hepatic microcirculation. AwETN-40, an anti-ET-1 antibody,9 and TAK-044, a nonselective ET receptor antagonist,18 were also tested. All of these experiments indicate that the inhibition of ET-1 effects suppresses portal pressure elevation, exerts marked hepatic microcirculatory improvement, and attenuates hepatic injury even after a 2-h complete hepatic ischemia. The mechanisms of the hepatic circulatory impairment caused by ET-1 actions are explained by two theories. Okumura et al.19 revealed that ET-1 induced hepatic sinusoidal vascoconstriction accompanied by reduced sinusoidal width. On the other hand, Kaneda et al.20 indicated that ET-1 induced a striking constriction of the distal segment of pre-terminal portal venules, Endothelin (ET) is a potent vasoconstrictor isolated from the supernatant of porcine aortic endothelial cells.1 ET has three isotypes, ET-1, ET-2, and ET-3,2 which have 21 amino acid residues originating from a larger precursor protein. The protein, named Big ET-1 is converted to ET-1 by the action of ET-converting enzyme.3 ET-1 exerts a paracrine effect on hepatic stellate and smooth muscle cells. Moreover, ET-1 has autocrine or intracrine effects on endothelial cells. The actions of ET-1 are promoted by its binding to specific receptors on the cell surface. Two kinds of receptors, named ET-A and ET-B receptors, have been verified,4 for which signals are transferred via guanosine triphosphate (GTP)-binding proteins. ET-A receptors are located on vascular smooth muscle cells and their affinity to ET-1 is higher than that to ET-2 or ET-3. The binding potency of ET-1 for ET-A is 100 times stronger than that of ET-3.5 The main action mediated by the ET-A receptor is vasoconstriction. The distribution of ET-B receptors is widespread; for example, they are found on smooth muscle cells and endothelial cells. The actions of ET-B receptors are different in different cell types. When ET-1 binds ET-B receptors on endothelial cells, it prompts nitric oxide release, resulting in the relaxation of vascular smooth muscle. On the other hand, ET-1 binding to ET-B receptors on smooth muscle cells induces vascular constriction. ET-B receptors are divided into two types. Endotheliumdependent relaxation is caused by ET-B1 receptors, and ET-B2 receptors promote smooth muscle vasoconstriction. The physiological role of ET-1 has been investigated by Teerlink et al.,6 using anesthetized dogs. The admin-

A rescue case of an idiopathic cecum perforation accompanied with sub-acute fulminant hepatitis

症例は38歳女性. 亜急性型劇症肝炎で生体肝移植の適応評価のため当科に転院しICU管理となった. 高容量持続的血液透析濾過と血漿交換を併用する保存的治療を行ったが, 入院10日目に発症した上行結腸破裂に対し右半結腸切除術を行い回腸に人工肛門を増設した. その後肝機能は順調に回復し入院30日目で一時退院, 5カ月後に再入院し人工肛門を閉鎖し現在社会復帰している. 切除した結腸の穿孔部は虚血性腸炎の病理診断を得た. 亜急性型劇症肝炎の保存的治療中に虚血性腸炎による大腸穿孔の報告はなく, その臨床経過と大腸穿孔の原因に考察を加え報告した.

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. Non-treated 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.