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T A Koeppel

Publications and source records attributed to T A Koeppel.

14 recordsLinked to original sources
PubMed2001

Impact of inhibition of complement by sCR1 on hepatic microcirculation after warm ischemia.

Recent observations provide evidence that complement is implicated as an important factor in the pathophysiology of ischemia/reperfusion injury (IRI). Here, we assessed the effects of complement inhibition on hepatic microcirculation by in vivo microscopy (IVM) using a rat model of warm hepatic ischemia clamping the left pedicle for 70 min. Ten animals received the physiological complement regulator soluble complement receptor type 1 (sCR1) intravenously 1 min prior to reperfusion. Controls were given an equal amount of Ringer's solution (n = 10). Microvascular perfusion and leukocyte adhesion were studied 30 to 100 min after reperfusion by IVM. Microvascular perfusion in hepatic sinusoids was significantly improved in the sCR1 group (80.6 +/- 0.6% of all observed sinusoids were perfused [sCR1] vs 67.3 +/- 1.2% [controls]). The number of adherent leukocytes was reduced in sinusoids (49.9 +/- 3.4 [sCR1] vs 312.3 +/- 14.2 in controls [adherent leukocytes per square millimeter of liver surface]; P < 0.001) as well as in postsinusoidal venules after sCR1 treatment (230.9 +/- 21.7 [sCR1] vs 1906.5 +/- 93.5 [controls] [adherent leukocytes per square millimeter of endothelial surface]; P < 0.001). Reflecting reduced hepatocyte injury, liver transaminases were decreased significantly upon sCR1 treatment compared to controls. Our results provide further evidence that complement plays a decisive role in warm hepatic IRI. Therefore, we conclude that complement inhibition by sCR1 is effective as a therapeutical approach to reduce microcirculatory disorders after reperfusion following warm organ ischemia.

Animals↗
PubMed1998

Complement inhibition by soluble complement receptor type 1 improves microcirculation after rat liver transplantation.

BACKGROUND: Recent observations provide evidence that complement is involved in the pathophysiology of ischemia/reperfusion injury. In this study, we assessed the impact of complement inhibition on hepatic microcirculation and graft function using a rat model of liver transplantation. METHODS: Arterialized orthotopic liver transplantation was performed in Lewis rats after cold preservation (University of Wisconsin solution, 4 degrees C, 24 h). Eight animals received the physiological complement regulator soluble complement receptor type 1 (sCR1) intravenously 1 min before reperfusion. Controls received Ringer's solution (n=8). Microvascular perfusion, leukocyte adhesion, and Kupffer cell phagocytic activity were studied 30-100 min after reperfusion by in vivo microscopy. RESULTS: Microvascular perfusion in hepatic sinusoids was improved in the sCR1 group (87+/-0.7% vs. 50+/-1%; P < 0.001). The number of adherent leukocytes was reduced in sinusoids (68.3+/-4.7 vs. 334.1+/-15.8 [adherent leukocytes per mm < or = liver surface]; P < 0.001) and in postsinusoidal venules after sCR1 treatment (306.6+/-21.8 vs. 931.6+/-55.9 [adherent leukocytes per mm < or = endothelial surface]; P < 0.001). Kupffer cell phagocytic activity was decreased in the sCR1 group compared to controls. Postischemic bile production reflecting hepatocellular function was increased by almost 200% (P = 0.004) after complement inhibition. Plasmatic liver enzyme activity was decreased significantly upon sCR1 treatment, indicating reduced parenchymal cell injury. CONCLUSIONS: Our results provide further evidence that the complement system plays a decisive role in hepatic ischemia/reperfusion injury. We conclude that complement inhibition by sCR1 represents an effective treatment to prevent reperfusion injury in liver transplantation.

Animals↗
PubMed1998

Role of glutathione in hepatic bile formation during reperfusion after cold ischemia of the rat liver.

BACKGROUND/AIMS: Liver reperfusion following cold ischemia is frequently associated with diminished bile flow in patients undergoing liver transplantation. Glutathione is a major determinant of bile-acid independent bile flow, and the effects of cold ischemia on biliary glutathione excretion are unknown. METHODS: We examined the effects of cold ischemia (University of Wisconsin solution (4 degrees C), 24 h) with subsequent reperfusion (100 min) on biliary glutathione excretion in a recirculating system. Since glutathione might represent an important antioxidant within the biliary tract and oxidative stress in the biliary tract during reperfusion could contribute to the pathogenesis of bile duct injury after liver transplantation, we also assessed bile duct morphology in reperfused livers of mutant TR- -rats, in whom biliary excretion of glutathione is already impaired. RESULTS: Hepatic bile formation was diminished in reperfused Wistar rat livers after cold ischemia. Biliary glutathione concentrations and output were significantly decreased and correlated with postischemic changes in bile secretion. An increased biliary oxidized glutathione/glutathione ratio, indicating oxidative stress, was detected only immediately after the onset of reperfusion. Basal bile flow rates in TR- -rat livers which were already markedly reduced in control-perfused livers, decreased further during the early but not the later reperfusion period. Reperfusion of both Wistar and TR- -rat livers was not associated with electron microscopic evidence of bile duct damage. CONCLUSIONS: We conclude that impaired biliary excretion of glutathione contributes to decreased bile flow after cold ischemia. The absence of biliary glutathione does not appear to promote ultrastructural evidence of bile duct injury during reperfusion in the isolated perfused rat liver.

Adenosine↗
PubMed1997

Endotoxin impairs biliary glutathione and HCO3- excretion and blocks the choleretic effect of nitric oxide in rat liver.

Cholestasis in patients with sepsis has been attributed to the effects of endotoxin (lipopolysaccharides, LPS) and LPS-induced cytokines, which are also potent stimulators of systemic and hepatic nitric oxide (NO) synthesis. NO donors stimulate bile acid-independent bile flow in normal rat liver, but the effects of LPS-induced NO on bile formation remain unclear. To address this question we examined the effects of NO and its mediator guanosine 3',5'-cyclic monophosphate (cGMP) on bile flow and biliary HCO3- and glutathione excretion in isolated perfused rat livers (IPRL) from LPS-treated rats. Portal and systemic NO2- + NO3- plasma levels were increased 47-fold in LPS-treated rats and were also elevated in perfusate (6-fold) and bile (9-fold) after isolating and perfusing livers from these animals. Bile flow, HCO3-, and glutathione output were decreased by 33%, 25%, and 81% in these IPRL, respectively. Stimulation of NO synthesis with L-arginine or inhibition of inducible NO synthesis with aminoguanidine did not change bile flow, although pretreatment with aminoguanidine inhibited NO production by 85%. Moreover, the choleretic effects of infusions of the NO donors sodium nitroprusside (SNP) and S-nitroso-acetyl-penicillamine were markedly reduced in endotoxemic IPRL compared with normal controls, and SNP-induced HCO3- and glutathione excretion were reduced by 61% and 86%, respectively. SNP-induced cyclic GMP production was 2.3-fold lower than in normals, but the choleretic effect of dibutyryl cGMP was only slightly reduced in endotoxemic livers. These findings indicate that LPS reduces bile acid-independent bile flow primarily by inhibiting biliary excretion of glutathione and to a lesser extent HCO3-, whereas LPS-induced NO does not modulate bile formation in endotoxemia. Thus, impairment of the major determinants of bile acid-independent bile flow by LPS may contribute significantly to the pathogenesis of the cholestasis of sepsis.

Animals↗
PubMed1997

Extrahepatic biliary obstruction impairs microvascular perfusion and increases leukocyte adhesion in rat liver.

To determine if disturbances of the liver microcirculation may be of pathophysiological relevance for liver damage during acute biliary obstruction, we studied the effects of bile duct ligation (BDL) on hepatic microhemodynamics and leukocyte adhesion in rat liver in vivo. Male Wistar rats were subjected to BDL for 3 days and 7 days, respectively. Sham-operated controls underwent laparotomy without BDL. After 3 days, intravital fluorescence microscopy (IVM) and hydrogen gas (H2) clearance were performed to study hepatic microvascular perfusion. Furthermore, leukocyte-endothelial cell interactions were assessed by IVM. Intercellular adhesion molecule 1 (ICAM-1) protein expression was studied by Western blot analysis and tissue immunofluorescence after 3 and 7 days, respectively. Analysis of microvascular perfusion by IVM revealed a marked impairment of sinusoidal perfusion after 3 days. Assessment of H2 clearance confirmed that overall hepatic microvascular perfusion was decreased. In addition, increased leukocyte adhesion in sinusoids and venules could be observed. A concomitant increase of ICAM-1 expression in liver tissue was also noted within the first week after BDL. Our results show that BDL is followed by a marked depression of the hepatic microcirculation and increased leukocyte adhesion in vivo within 3 to 7 days. Together, these findings suggest that deficits in microvascular perfusion and increased neutrophil infiltration may represent a potential source of liver injury during acute biliary obstruction.

Animals↗
PubMed1997

The rat canalicular conjugate export pump (Mrp2) is down-regulated in intrahepatic and obstructive cholestasis.

BACKGROUND & AIMS: The excretion of various organic anions into bile is mediated by an adenosine triphosphate-dependent conjugate export pump, which has been identified as the canalicular isoform of the multidrug resistance protein (Mrp2). Mrp2 function is impaired in various experimental models of intrahepatic and obstructive cholestasis, but the underlying molecular mechanisms are unclear. The aim of this study was to investigate these molecular mechanisms. METHODS: The effects of endotoxin, ethinylestradiol, and common bile duct ligation (CBDL) on Mrp2 protein, messenger RNA (mRNA) expression, and Mrp2 tissue localization were determined in rat livers by Northern blotting, Western analysis, and tissue immunofluorescence. To assess whether changes were specific for Mrp2, we also examined the expression of canalicular ecto-adenosine triphosphatase (ecto-ATPase) and mdr P-glycoproteins (P-gp). RESULTS: All three cholestatic models resulted in a marked decrease in Mrp2 protein (P < 0.01) and its tissue localization at the canalicular membrane. Mrp2 mRNA levels diminished profoundly after endotoxin (P < 0.0005) and CBDL (P < 0.05), but did not change after ethinylestradiol. In contrast to Mrp2, protein expression of ecto-ATPase and P-gp remained unchanged in endotoxin- and ethinylestradiol-treated animals, whereas P-gp levels increased after CBDL (P < 0.05). CONCLUSIONS: Down-regulation of Mrp2 expression may explain impaired biliary excretion of amphiphilic anionic conjugates in these models of cholestasis.

ATP-Binding Cassette Transporters↗
PubMed1997

Inhibition of nitric oxide synthesis in ischemia/reperfusion of the rat liver is followed by impairment of hepatic microvascular blood flow.

BACKGROUND: Recent studies provide evidence that nitric oxide (NO) has beneficial effects in hepatic ischemia/reperfusion injury. The purpose of this study was to evaluate whether nitric oxide is involved in the regulation of hepatic microvascular perfusion after warm hepatic ischemia. Therefore, we performed a study using in vivo fluorescence microscopy. METHODS: Clamping of the left liver lobe was performed in male Wistar rats for the duration of 70 min. One experimental group (n=8) received L-NAME (Nw-nitro-L-arginine methyl ester hydrochloride), an NO-synthase inhibitor, 1 min prior to reperfusion. A second experimental group (n=8) received L-arginine (NO-substrate) continuously infused throughout the observation period. Controls (n=8) received equivalent volumes of an isotonic solution and underwent the same procedures. Hepatic microvascular blood flow and leukocyte-endothelial cell interaction was studied between 20 and 90 min after reperfusion using in vivo fluorescence microscopy. RESULTS: Inhibition of NO-synthesis during reperfusion by application of L-NAME caused a marked decrease in sinusoidal blood flow velocity. Furthermore, we noted an increase of non-perfused sinusoids in this group. Treatment with L-arginine improved functional perfusion of hepatic acini and reduced significantly the number of adherent leukocytes in sinusoids and venules compared to control animals. CONCLUSIONS: Our results provide further evidence that NO maintains postischemic hepatic microvascular perfusion and that inhibition of NO synthesis has detrimental effects on hepatic microhemodynamics during reperfusion.

Animals↗
PubMed1997

Effects of mixed ETA and ETB-receptor antagonist (Ro-47-0203) on hepatic microcirculation after warm ischemia.

There is evidence that endothelin (ET) is involved in disturbances of the hepatic microcirculation after warm ischemia. In this study we investigated the influence of a mixed ETA-, ETB-receptor antagonist (Bosentan) on ischemia-reperfusion damage of the liver by means of intravital fluorescence microscopy (IVM). Clamping of the left liver lobe (= warm ischemia) was performed in 16 male Wistar rats for 70 min. The treatment group (N = 8) received 15 mg/kg Bosentan (Ro-47-0203) 1 min prior to reperfusion. Controls (N = 8) received an equivalent amount of Ringer's solution. Between 20 and 90 min after reperfusion, leukocyte-endothelial cell interactions in sinusoids and postsinusoidal venules as well as perfusion of hepatic acini were studied. Application of Bosentan improved sinusoidal blood flow, attenuated manifestations of microvascular perfusion failure, and decreased the number of rolling leukocytes in postsinusoidal venules. Our results provide further evidence that ET is involved in postischemic impairment of hepatic microhemodynamics during reperfusion.

Animals↗
PubMed1996

Impact of N-acetylcysteine on the hepatic microcirculation after orthotopic liver transplantation.

Recent observations showed an improvement of hepatic macro- and microhemodynamics as well as survival rates after warm ischemia of the liver following treatment with N-acetylcysteine (NAC). In this study we assessed the influence of NAC on the hepatic microcirculation after orthotopic liver transplantation (OLT) using intravital fluorescence microscopy. OLT with simultaneous arterialization was performed in 16 male Lewis rats following cold storage in University of Wisconsin solution for 24 hr. Within the experimental group (n = 8) donors received NAC (400 mg/kg) 25 min before hepatectomy. In addition, high-dose treatment of recipients with NAC (400 mg/kg) was started with reperfusion. Control animals (n = 8) received an equivalent amount of Ringer's solution. Intravital fluorescence microscopy was performed 30-90 min after reperfusion assessing acinar and sinusoidal perfusion, leukocyte-endothelium interaction, and phagocytic activity. Treatment with NAC reduced the number of nonperfused sinusoid from 52.4 +/- 0.8% to 15.7 +/- 0.5% (p = 0.0001) (mean +/- SEM). Furthermore, we achieved a significant reduction of leukocytes adhering to sinusoidal endothelium (per mm2 liver surface) from 351.9 +/- 13.0 in controls to 83.6 +/- 4.2 in the experimental group (P = 0.0001). In postsinusoidal venules, treatment with NAC decreased the number of sticking leukocytes (per mm2 endothelium) from 1098.5 +/- 59.6 to 425.9 +/- 37.7 (P = 0.0001). Moreover, bile flow was significantly increased after therapy with NAC (4.3 +/- 1.2 vs. 2.2 +/- 0.7 ml/90 min x 100g liver) (P < 0.05). Phagocytic activity was not influenced by application of NAC. We conclude that high-dose therapy with NAC in OLT attenuates manifestations of microvascular perfusion failure early after reperfusion and should be considered as a means to reduce reperfusion injury.

Acetylcysteine↗
PubMedDate not supplied

Improvement of hepatic microhemodynamics by N-acetylcysteine after warm ischemia.

In this study we investigated the influence of N-acetylcysteine (NAC) on the hepatic microcirculation after warm ischemia by intravital fluorescence microscopy. Clamping of the left liver lobe was performed in 20 male Wistar rats for 70 min. The treatment group (n = 10) received 400 mg NAC/kg body weight 20 min prior to clamping. After reperfusion, acinar and sinusoidal perfusions were observed as well as the leukocyte-endothelium interaction. Phagocytic activity was assessed after application of latex beads. NAC reduced the number of nonperfused sinusoids in all acinar zones. A reduction in zone 1 (portal) was achieved from 15.5 to 7.1% (p < 0.0001), in zone 2 (midzonal) from 14.6 to 6.1% (p < 0.0001) and in zone 3 (central) from 11.9 to 2.9% (p < 0.0001). There were no significant differences in leukocyte adherence as well as in phagocytic activity detectable. We conclude that NAC improves hepatic microcirculation after warm ischemia by increasing sinusoidal blood flow.

Acetylcysteine↗