In contrast to its anti-inflammatory and anti-apoptotic peripheral effect, levosimendan failed to induce a long-term neuroprotective effect in a rat model of mild septic encephalopathy: a pilot study

Levosimendan shows protective myocardial characteristics and is administered to enhance cardiac contractility in patients. However, currently little is known about levosimendan's effect on brain. The aim of this pilot study was to investigate the long-term effect of levosimendan on brain and during mild rat sepsis in comparison to its peripheral mode of action. Adult rats (n=40) were divided into four groups with n=10 per group: (I) sham, (II) levosimendan (283 μg/kg body weight i.v.), (III) lipopolysaccharide (LPS, 8 mg/kg body weight i.p.), and (IV) LPS+levosimendan. Levosimendan was given 24h after injecting LPS. Psychometric investigations were conducted using a Morris water maze (MWM) and a holeboard test. In cerebral and splenic tissue, IL-1β, Il-6, TNFalpha levels, and apoptosis were determined; cerebral tissue corticosterone concentration was measured 6 days after injecting LPS. Blood cytokine concentrations were determined 1 day and 6 days after injecting LPS. Rats that received an LPS injection spent more time in the outer zone of the MWM according to increased cerebral corticosterone levels, and showed decreased cognitive abilities. LPS induced a reduction in body weight, increased splenic apoptosis and blood cytokine level. Levosimendan showed anti-inflammatory and anti-apoptotic properties in spleen but failed to show a long-term neuroprotective effect.

Levosimendan's effect on platelet function in a rat sepsis model

Although studies have evaluated the efficacy of levosimendan in heart failure during sepsis, it still is a subject of controversy whether levosimendan produces an effect on platelets. In this study, the short- and long-term effects of levosimendan on platelet aggregation were investigated in untreated animals and in a rat model of sepsis. Therefore, adult rats (n = 40) were randomly divided into four groups with n = 10 per group: (I) sham, (II) levosimendan (bolus 53 µg/kg + 285 µg/kg/hour, intravenously (i.v.) injected), (III) LPS (lipopolysaccharide, 8 mg/kg body weight intraperitoneally injected), and (IV) LPS + levosimendan. Levosimendan was given 24 hours after LPS injections. The number of platelets was determined. Platelet aggregation was measured using venous blood from rats 10 minutes and 5 days after levosimendan application with Dynabyte Multiplate system. Aggregation responses were evaluated with adenosine diphosphate (10 µM) and collagen (5 µg/ml). In addition to clinical dosage, the in vitro effect of high-dosage levosimendan on platelet function was investigated. The results clearly showed that LPS significantly reduced the platelet aggregation 1 day after injection compared to controls; 6 days after LPS, a marked increase (p < 0.01) was noted. This result is associated with numbers of platelets. Levosimendan (bolus 53 µg/kg + 285 µg/kg/hour i.v.) had no significant effect on the platelets of rats in contrast to the high-dosage in vitro findings. Thus, the in vivo use of levosimendan does not affect blood coagulation significantly in this rat model. This also applies under the conditions of decreased and increased numbers of platelets during mild sepsis.

Evaluation of a low molecular weight modulator of human plasminogen activator inhibitor-1 activity

A critical component in the regulation of thrombus formation and clearance is the balance between tissue plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1). An increase in the plasma concentration of PAI-1 has been proposed as a risk factor in thrombotic disease. Inhibition of PAI-1 activity may have utility in the treatment of thromboembolic disease. We report here the evaluation of three diketopiperazine-based low molecular weight inhibitors of PAI-1 activity (XR334, XR1853 and XR5082). In vitro these compounds reversed the inhibitory effects of PAI-1 against both tPA and urokinase (UK) (IC50: 5 to 80 muM). In contrast, other serpin-serine protease interactions, including alpha 1-antitrypsin-trypsin, alpha 2-antiplasmin- plasmin and antithrombin-thrombin, were not affected, neither did these inhibitors affect global tests of haemostasis. In the light of this promising in vitro profile these compounds were evaluated in a standard radioisotopic assay of clot lysis in whole rat blood following intravenous administration. In this assay these compounds dose-dependently enhanced fibrinolysis ex vivo. After intravenous bolus administration XR334, XR1853 and XR5082 at 5 mg/kg increased clot lysis by 32.0 +/- 5.1% SEM (n = 25, p < 0.01), 36.7 +/- 3.5% SEM (n = 36, p < 0.01) and 60.0 +/- 2.8% SEM (n = 17, p < 0.01) respectively compared to vehicle. Intravenous infusion of these compounds (1 mg/kg/min for 20 min) significantly prolonged (approximately twofold) the time to blood vessel occlusion in the rat electrically-stimulated carotid artery thrombosis model. Thus, these low molecular weight inhibitors of PAI-1 activity enhanced fibrinolysis ex vivo and protected against thrombus formation in the rat.