Left ventricular assist device implantation causes platelet dysfunction and proinflammatory platelet-neutrophil interaction.

Blood flow through left ventricular assist devices (LVAD) may induce activation and dysfunction of platelets. Dysfunctional platelets cause coagulation disturbances and form platelet-neutrophil conjugates (PNC), which contribute to inflammatory tissue damage. This prospective observational cohort study investigated patients, who underwent implantation of a LVAD (either HeartMate II (HM II) (n = 7) or HeartMate 3 (HM 3) (n = 6)) and as control patients undergoing coronary artery bypass grafting (CABG) and/or aortic valve replacement (AVR) (n = 10). We performed platelet and leukocyte flow cytometry, analysis of platelet activation markers, and platelet aggregometry. Platelet CD42b expression was reduced at baseline and perioperatively in HM II/3 compared to CABG/AVR patients. After surgery the platelet activation marker ß-thromboglobulin and platelet microparticles increased in all groups while platelet aggregation decreased. Platelet aggregation was more significantly impaired in LVAD compared to CABG/AVR patients. PNC were higher in HM II compared to HM 3 patients. We conclude that LVAD implantation is associated with platelet dysfunction and proinflammatory platelet-leukocyte binding. These changes are less pronounced in patients treated with the newer generation LVAD HM 3. Future research should identify device-specific LVAD features, which are associated with the least amount of platelet activation to further improve LVAD therapy.

Multi-Modal Characterization of the Coagulopathy Associated With Extracorporeal Membrane Oxygenation.

OBJECTIVES: Extracorporeal membrane oxygenation is used to stabilize severe cardiocirculatory and/or respiratory failure. However, extracorporeal membrane oxygenation is associated with a coagulopathy characterized by thromboembolic and hemorrhagic complications. This study aimed to characterize the pathomechanism of the extracorporeal membrane oxygenation-associated coagulopathy and identify options to optimize its monitoring and therapy. DESIGN: Prospective observational clinical trial. SETTING: ICU of a university hospital. PATIENTS: Patients treated with venovenous extracorporeal membrane oxygenation (n = 10) due to acute respiratory distress syndrome and patients treated with venoarterial extracorporeal membrane oxygenation (n = 8) due to cardiocirculatory failure. One patient per group (venovenous extracorporeal membrane oxygenation or venoarterial extracorporeal membrane oxygenation) had surgery before extracorporeal membrane oxygenation. INTERVENTIONS: Blood was sampled before, and 1, 24, and 48 hours after extracorporeal membrane oxygenation implantation. Point-of-care tests (thrombelastometry/platelet aggregometry), conventional coagulation tests, whole blood counts, and platelet flow cytometry were performed. MEASUREMENTS AND MAIN RESULTS: Even before extracorporeal membrane oxygenation, plasmatic coagulation and platelet aggregation were impaired due to systemic inflammation, liver failure, anticoagulants (heparins, phenprocoumon, apixaban), and antiplatelet medication. During extracorporeal membrane oxygenation, hemodilution and contact of blood components with artificial surfaces and shear stress inside extracorporeal membrane oxygenation additionally contributed to coagulation and platelet defects. Fibrinogen levels, fibrin polymerization, platelet activation, and microparticle release were increased in venovenous extracorporeal membrane oxygenation compared to venoarterial extracorporeal membrane oxygenation patients. Point-of-care results were available faster than conventional analyses. Bleeding requiring blood product application occurred in three of 10 venovenous extracorporeal membrane oxygenation patients and in four of eight venoarterial extracorporeal membrane oxygenation patients. No thrombotic events were observed. In-hospital mortality was 30% for venovenous extracorporeal membrane oxygenation and 37.5% for venoarterial extracorporeal membrane oxygenation patients. CONCLUSIONS: The extracorporeal membrane oxygenation-associated coagulopathy is a multifactorial and quickly developing syndrome. It is characterized by individual changes of coagulation parameters and platelets and is aggravated by anticoagulants. The underlying factors of the extracorporeal membrane oxygenation-associated coagulopathy differ between venovenous extracorporeal membrane oxygenation and venoarterial extracorporeal membrane oxygenation patients and are best diagnosed by a combination of point-of-care and conventional coagulation and platelet analyses. Therapy protocols for treating extracorporeal membrane oxygenation-associated coagulopathy should be further validated in large-scale prospective clinical investigations.

Site-controlled formation of single Si nanocrystals in a buried SiO2 matrix using ion beam mixing.

For future nanoelectronic devices - such as room-temperature single electron transistors - the site-controlled formation of single Si nanocrystals (NCs) is a crucial prerequisite. Here, we report an approach to fabricate single Si NCs via medium-energy Si+ or Ne+ ion beam mixing of Si into a buried SiO2 layer followed by thermally activated phase separation. Binary collision approximation and kinetic Monte Carlo methods are conducted to gain atomistic insight into the influence of relevant experimental parameters on the Si NC formation process. Energy-filtered transmission electron microscopy is performed to obtain quantitative values on the Si NC size and distribution in dependence of the layer stack geometry, ion fluence and thermal budget. Employing a focused Ne+ beam from a helium ion microscope, we demonstrate site-controlled self-assembly of single Si NCs. Line irradiation with a fluence of 3000 Ne+/nm2 and a line width of 4 nm leads to the formation of a chain of Si NCs, and a single NC with 2.2 nm diameter is subsequently isolated and visualized in a few nanometer thin lamella prepared by a focused ion beam (FIB). The Si NC is centered between the SiO2 layers and perpendicular to the incident Ne+ beam.

Kupffer cell activation in normal and fibrotic livers increases portal pressure via thromboxane A(2).

BACKGROUND/AIMS: Cirrhotic patients show an increased risk of variceal bleeding upon bacterial infections. Kupffer cells (KC) constitute the first macrophage population to become activated by bacterial beta-glucans and endotoxins derived from the gut. We therefore investigated whether and how KC activation increases portal pressure. METHODS: KC in normal and fibrotic livers from bile duct ligated (BDL) rats were activated by the beta-glucan component of zymosan in vivo and during isolated rat liver perfusion. RESULTS: Activation of KC in normal livers resulted in a severalfold increase of portal pressure in vivo as well as in isolated perfused liver preparations. This increase and the accompanying 40-fold stimulation of hepatic prostaglandin F(2alpha)/D(2) and thromboxane A(2) (TxA(2)) production in isolated perfused livers were attenuated by KC blockade. The TxA(2) synthase inhibitor furegrelate and the TxA(2) receptor antagonist BM 13.177 reduced the increase of portal perfusion pressure supporting TxA(2) as pivotal vasoconstrictor released by activated KC. Importantly, a more pronounced vasopressor response in fibrotic livers was related to a raise in KC density and a 10-fold increase of TxA(2) production after KC activation. CONCLUSIONS: KC activated by beta-glucans increase portal pressure through the release of TxA(2). This vasopressor response is augmented in BDL induced fibrosis.

IL-22-mediated liver cell regeneration is abrogated by SOCS-1/3 overexpression in vitro.

The IL-10-like cytokine IL-22 is produced by activated T cells. In this study, we analyzed the role of this cytokine system in hepatic cells. Expression studies were performed by RT-PCR and quantitative PCR. Signal transduction was analyzed by Western blot experiments and ELISA. Cell proliferation was measured by MTS and [(3)H]thymidine incorporation assays. Hepatocyte regeneration was studied in in vitro restitution assays. Binding of IL-22 to its receptor complex expressed on human hepatic cells and primary human hepatocytes resulted in the activation of MAPKs, Akt, and STAT proteins. IL-22 stimulated cell proliferation and migration, which were both significantly inhibited by the phosphatidylinositol 3-kinase inhibitor wortmannin. IL-22 increased the mRNA expression of suppressor of cytokine signaling (SOCS)-3 and the proinflammatory cytokines IL-6, IL-8, and TNF-alpha. SOCS-1/3 overexpression abrogated IL-22-induced STAT activation and decreased IL-22-mediated liver cell regeneration. Hepatic IL-22 mRNA expression was detectable in different forms of human hepatitis, and hepatic IL-22 mRNA levels were increased in murine T cell-mediated hepatitis in vivo following cytomegalovirus infection, whereas no significant differences were seen in an in vivo model of ischemia-reperfusion injury. In conclusion, IL-22 promotes liver cell regeneration by increasing hepatic cell proliferation and hepatocyte migration through the activation of Akt and STAT signaling, which is abrogated by SOCS-1/3 overexpression.

Characterization of organic anion transporter regulation, glutathione metabolism and bile formation in the obese Zucker rat.

BACKGROUND/AIMS: Alterations in hepatobiliary transporters may render fatty livers more vulnerable against various toxic insults. METHODS: We therefore studied expression and function of key organic anion transporters and their transactivators in 8-week-old obese Zucker rats, an established model for non-alcoholic fatty liver disease. RESULTS: Compared to their heterozygous littermates, obese animals showed a significant reduction in canalicular bile salt secretion, which was paralleled by significantly diminished Oatp2 mRNA and protein levels together with reduced nuclear HNF3beta, while expression of bile salt export pump, organic anion transporter (Oatp) 1 and multidrug resistance-associated protein (Mrp) 4 were unchanged. Impaired bile salt-independent bile flow in obese rats was associated with a 50% reduction of biliary secretion of the Mrp 2 model-substrates glutathione disulfide and S-(2,4-dinitrophenyl)glutathione. In line Mrp2 protein expression was reduced by 50% in obese rats. CONCLUSIONS: Oatp2 and Mrp2 expression is decreased in fatty liver and may impair metabolism and biliary secretion of numerous xenobiotics. Reduction of bile salt secretion and absence of biliary GSH excretion may contribute to impaired bile flow and posthepatic disorders associated with biliary GSH depletion.