Toll-like receptor 2-deficiency on bone marrow-derived cells augments vascular healing of murine arterial lesions.

AIMS: Neointimal hyperplasia contributes to arterial restenosis after percutaneous transluminal coronary angioplasty or vascular surgery. Neointimal thickening after arterial injury is determined by inflammatory processes. We investigated the role of the innate immune receptor toll-like receptor 2 (TLR2) in neointima formation after arterial injury in mice. MATERIALS AND METHODS: Carotid artery injury was induced by 10% ferric chloride in C57Bl/6J wild type (WT), TLR2 deficient (B6.129-Tlr2tm1Kir/J, TLR2-/-) and WT mice treated with a TLR2 blocking antibody. 21 days after injury, carotid arteries were assessed histomorphometrically and for smooth muscle cell (SMC) content. To identify the contribution of circulating cells in mediating the effects of TLR2-deficiency, arterial injury was induced in WT/TLR2-/--chimeric mice and the paracrine modulation of bone marrow-derived cells from WT and TLR2-/- on SMC migration compared in vitro. KEY FINDINGS: TLR2-/- mice and WT mice treated with TLR2 blocking antibodies exhibited reduced neointimal thickening (23.7 ± 4.2 and 6.5 ± 3.0 vs. 43.1 ± 5.9 µm, P < 0.05 and P < 0.01), neointimal area (5491 ± 1152 and 315 ± 76.7 vs. 13,756 ± 2627 µm2, P < 0.05 and P < 0.01) and less luminal stenosis compared to WT mice (8.5 ± 1.6 and 5.0 ± 1.3 vs. 22.4 ± 2.2%, both P < 0.001n = 4-8 mice/group). The phenotypes of TLR2-/- vs. WT mice were completely reverted in WT/TLR2-/- bone marrow chimeric mice (5.9 ± 1.5 µm neointimal thickness, 874.2 ± 290.2 µm2 neointima area and 2.7 ± 0.6% luminal stenoses in WT mice transplanted with TLR2-/- bone marrow vs. 23.6 ± 5.1 µm, 3555 ± 511 µm2 and 12.0 ± 1.3% in WT mice receiving WT bone marrow, all P < 0.05, n = 6/group). Neointimal lesions of WT and WT mice transplanted with TLR2-/- bone marrow chimeric mice showed increased numbers of SMC (10.8 ± 1.4 and 12.6 ± 1.4 vs. 3.8 ± 0.9 in TLR2-/- and 3.5 ± 1.1 cells in WT mice transplanted with TLR2-/- bone marrow, all P < 0.05, n = 6). WT bone marrow cells stimulated SMC migration more than TLR2-deficient bone marrow cells (1.7 ± 0.05 vs. 1.3 ± 0.06-fold, P < 0.05, n = 7) and this effect was aggravated by TLR2 stimulation and diminished by TLR2 blockade (1.1 ± 0.03-fold after stimulation with TLR2 agonists and 0.8 ± 0.02-fold after TLR2 blockade vs. control treated cells defined as 1.0, P < 0.05, n = 7). SIGNIFICANCE: TLR2-deficiency on hematopoietic but not vessel wall resident cells augments vascular healing after arterial injury. Pharmacological blockade of TLR2 may thus be a promising therapeutic option to improve vessel patency after iatrogenic arterial injury.

Xenon anesthesia impairs hepatic oxygenation and perfusion in healthy pigs.

BACKGROUND: Over the last 15 years, there has been growing interest in the noble gas xenon as a new inhalational anesthetic. This is due to its favorable pharmacological properties such as short onset and offset, as well as its hemodynamic stability. However, most volatile anesthetics appear to play an important role in the multi-factorial etiology of perioperative liver injury by decreasing liver blood flow with a subsequent reduction of hepatic oxygen supply. However, the effects of the anesthetic gas xenon on hepatic perfusion and oxygenation have not been completely investigated. METHODS: Following ethical approval, 18 anesthetized and acutely monitored pigs were randomly assigned to the two following groups: 9 animals received xenon anesthesia in increasing inspiratory concentrations of 0%, 20%, 50%, and 65% in addition to their basic intravenous anesthesia; 9 animals served as a control group. Measurement points for systemic and regional hemodynamic and oxygenation parameters were performed 30 min after changing the xenon concentration. RESULTS: Xenon elicited dose-dependent systemic hemodynamic changes such that the mean arterial pressure did not change, while the heart rate and cardiac output decreased by about 30%, thereby indicating an increase in the systemic vascular resistance. Portal venous blood flow decreased, while hepatic arterial blood flow was unchanged. The oxygen supply of the liver was reduced, but not the rate of indocyanine plasma disappearance from the liver. Furthermore, the increase of liver surface pO2 to systemic hyperoxia was absent, and hepatic lactate uptake was reduced. CONCLUSION: Xenon, in addition to basic intravenous anesthesia, elicited a decrease in heart rate and cardiac output and an increase in mean arterial pressure. Similar to volatile anesthetics, xenon does reduce portal venous flow and influences hepatic tissue oxygenation. In contrast, hepatic arterial blood flow remains stable in the presence of xenon, and no changes in the hepatic arterial buffer responses were evident. Xenon does affect hepatic perfusion and oxygenation.

[Influence of clonidine-induced systemic sympathicolysis on oxygenation and perfusion of the liver. Investigations with healthy pigs under general anesthesia]. / Einfluss der Clonidin-induzierten systemischen Sympathikolyse auf die Oxygenierung und Perfusion der Leber. Untersuchungen am gesunden Hausschwein in Allgemeinanästhesie.

BACKGROUND: Increased sympathetic nervous activity which induces vasoconstriction and decreases perfusion may be an underlying mechanism behind the development of perioperative liver damage. This animal study was designed to assess how clonidine-induced systemic sympathicolysis affects liver oxygenation with respect to induced hypotension and vasodilatation under physiological conditions. METHODS: Following ethical approval 17 anesthetized and acutely instrumented pigs were randomly assigned to 2 groups. Group 1 consisted of 8 animals receiving intravenous clonidine (2 microg x kg(-1) bolus and 2 microg x kg(-1) x h(-1) for induction of sympathicolysis and group 2 consisted of 9 animals serving as controls. After obtaining baseline values, measurements were repeated 90 and 250 min after starting to reduce systemic sympathetic nervous activity. RESULTS: Clonidine-induced systemic sympathicolysis was associated with decreased mean arterial blood pressure, cardiac output and heart rate. Portal venous and hepatic arterial blood flow, oxygen delivery to the liver, oxygen uptake and liver tissue oxygen partial pressure remained unchanged. The plasma indocyanine green disappearance rate increased. CONCLUSION: We concluded that despite decreased mean arterial pressure and cardiac output, clonidine-induced systemic sympathicolysis did not affect liver oxygenation or perfusion.

Protective effects of PARP inhibition on liver microcirculation and function after haemorrhagic shock and resuscitation in male rats.

OBJECTIVE: The aim of this study was to investigate the impact of the water-soluble poly-(ADP)-ribose-polymerase (PARP) inhibitor 5-aminoisoquinolinone (5-AIQ) on liver microcirculation and function after haemorrhagic shock and resuscitation. DESIGN: Controlled, randomized animal study. SETTING: University animal care facility and research laboratory. SUBJECT: Male Sprague-Dawley rats were subjected to haemorrhagic shock for 1 h, followed by resuscitation with shed blood and crystalloid solution for a total of 5 h. INTERVENTIONS: The PARP inhibitor 5-AIQ (3 mg/kg; n=7) or vehicle (n=7) was administered 5 min prior to resuscitation. Sham-operated animals without induction of shock served as controls (n=7). MEASUREMENTS AND RESULTS: Using intravital fluorescence microscopy hepatic microcirculation was assessed at baseline, end of shock phase as well as 1 h and 5 h after resuscitation. Systemic arterial blood pressure and bile flow were continuously monitored. 5-AIQ treatment attenuated shock/resuscitation-induced increase of intrahepatic leukocyte-endothelial cell interaction with a marked reduction of both sinusoidal leukostasis and venular leukocyte adherence. Moreover, nutritive perfusion was found improved, guaranteeing sufficient oxygen supply to tissue, as indicated by low NADH autofluorescence, which was not different to that in controls. Most notably, excretory liver function reached baseline level over 5 h of reperfusion in 5-AIQ-treated animals. CONCLUSIONS: In the present setting of shock/resuscitation in male rats the PARP inhibitor 5-AIQ proved to be very effective in ameliorating compromised liver microcirculation and function. Further research has to confirm that PARP inhibition is a suitable tool in the acute treatment of patients suffering from reduced circulating blood volume and thus microcirculatory organ dysfunction.

Effects of systemically applied clonidine on intestinal perfusion and oxygenation in healthy pigs during general anaesthesia and laparotomy.

BACKGROUND AND OBJECTIVE: Clonidine, which is used for induction of sympatholysis and prevention or treatment of alcohol withdrawal in anaesthesia and intensive care medicine, may have deleterious effects on intestinal mucosal perfusion. This study was designed to investigate the effects of clonidine on intestinal perfusion and oxygenation. METHODS: Following ethical approval 17 anaesthetized, and acutely instrumented pigs were randomly assigned to two groups: eight animals received intravenous clonidine (2 microg kg(-1) bolus and 2 microg kg(-1) h(-1)), nine animals served as a control group. Measurement points for systemic and regional haemodynamic and oxygenation parameters were 135 and 315 min after starting the clonidine application. RESULTS: Clonidine elicited systemic haemodynamic changes (median [25-75th interquartile range]): heart rate (106 [91, 126] to 84 [71, 90] beats min(-1)) cardiac output (147 [123, 193] to 90 [87, 107] mL min(-1) kg(-1)) and mean arterial pressure (77 [72, 93] to 69 [61, 78] mmHg) decreased. Despite systemic haemodynamic changes, the superior mesenteric artery blood flow did not change in the clonidine group. The vascular resistance of the superior mesenteric artery decreased. The small intestinal oxygen supply, the mucosal and the serosal tissue oxygen partial pressure did not change. CONCLUSIONS: Systemic sympatholysis induced by intravenously applied clonidine in addition to basic intravenous anaesthesia elicited a decrease in cardiac output and mean arterial pressure. However, regional macrohaemodynamic perfusion was maintained and intestinal oxygenation did not change. Clonidine does not impair intestinal mucosal and serosal oxygenation under physiological conditions.

Effects of xenon anaesthesia on intestinal oxygenation in acutely instrumented pigs.

BACKGROUND: Xenon is a narcotic gas that might be able to replace volatile anaesthetics or nitrous oxide due to its favourable pharmacological properties, such as providing haemodynamic stability. Intestinal oxygenation is affected by most volatile anaesthetics as a result of cardiodepressive effects. Reducing oxygenation of the gut might be a factor leading to perioperative organ dysfunction. This animal study was designed to assess the effects of xenon on intestinal oxygenation. METHODS: After ethical approval, 24 anaesthetized, acutely instrumented pigs were randomly assigned to three groups: nine animals received xenon anaesthesia with inspiratory concentrations of 0, 20, 50 and 65% in addition to their basic i.v. anaesthesia, nine animals served as a study control group, and five animals were used to assess model stability. Measurement of systemic and regional haemodynamic and oxygenation parameters was made 30 min after changing the xenon concentration. RESULTS: Xenon elicited dose-dependent systemic haemodynamic changes: heart rate and cardiac output decreased by 30%, while mean arterial pressure was stable. Superior mesenteric artery blood flow was lower in the xenon group. Vascular resistance of the superior mesenteric artery increased. The small intestinal oxygen supply decreased with increasing xenon concentration; the mucosal tissue oxygen partial pressure decreased but did not reach hypoxic (<5 mm Hg) values. Serosal tissue oxygen partial pressure was maintained. CONCLUSIONS: Xenon, in addition to basic i.v. anaesthesia, elicited a decrease in cardiac output and maintained mean arterial pressure. Intestinal oxygenation was maintained, although regional macrohaemodynamic perfusion decreased. Xenon does not impair intestinal oxygenation under physiological conditions.

Increased cytosolic Ca2+ amplifies oxygen radical-induced alterations of the ultrastructure and the energy metabolism of isolated rat pancreatic acinar cells.

BACKGROUND: Oxygen radicals have been implicated as important mediators in the early pathogenesis of acute pancreatitis, but the mechanism by which they produce pancreatic tissue injury remains unclear. We have, therefore, investigated the effects of oxygen radicals on isolated rat pancreatic acinar cells as to the ultrastructure, cytosolic Ca2+ concentration and energy metabolism. METHODS: Acinar cells were exposed to an oxygen radical-generating system consisting of xanthine oxidase, hypoxanthine and chelated iron ions. Cell injury was assessed by LDH release and electron microscopy. Cytosolic Ca2+ levels and mitochondrial membrane potential were determined by flow cytometry; adenine nucleotide concentrations by HPLC. Mitochondrial dehydrogenase activity was measured by spectrophotometric assay. RESULTS: Oxygen radicals damaged the plasma membrane as shown by a 6-fold LDH increase in the incubation medium within 180 min. At the ultrastructural level, mitochondria were the most susceptible to oxidative stress. In correlation to the pronounced mitochondrial damage, the mitochondrial dehydrogenase activity declined by 70%, whereas the mitochondrial membrane potential was enhanced by 27% after 120 min. Together this may cause the 85% decrease in the ATP concentration and the corresponding increase in ADP/AMP observed in parallel. In addition, an immediate 26% increase in cytosolic Ca2+ was found, a change which could be inhibited by BAPTA, reducing cellular damage. CONCLUSION: Cytosolic Ca2+ synergizes with oxygen radicals causing alterations of the ultrastructure and energy metabolism of acinar cells which might contribute to the cellular changes found in early stages of acute pancreatitis.