Reducing Elevated Heart Rates in Patients with Multiple Organ Dysfunction Syndrome with The If (Funny Channel Current) Inhibitor Ivabradine.

INTRODUCTION: A heart rate higher than 90 beats/min indicates an unfavorable prognosis for patients with multiple organ dysfunction syndrome (MODS). We sought to investigate the effect of the pacemaker current (If) inhibitor ivabradine on heart rate, hemodynamics, and disease severity among patients with MODS. PATIENTS AND METHODS: In this prospective, controlled, randomized, open-label, two-arm phase II trial, 70 patients with MODS, a sinus rhythm of at least 90 beats/min, and contraindications to ß-blocker therapy were randomly assigned to receive the standard treatment ± ivabradine (5 mg twice daily) for 96 h via the enteral route. The primary outcome was the percentage of patients with a heart rate reduction of at least 10 beats/min after 96 h. Secondary outcomes included the effect of ivabradine on hemodynamics, disease severity, vasopressor use, mortality, and adverse events. RESULTS: There were no significant differences in the primary outcome between the ivabradine and control groups (P = 0.147). After 96 h, the daily median heart rate was reduced by 7 beats/min in the control group and by 16 beats/min in the ivabradine group (P = 0.014). No differences in secondary outcomes were observed. CONCLUSIONS: The number of critically ill patients with MODS and a sinus rhythm of at least 90 beats/min that experienced a heart rate reduction of at least 10 beats/min after oral ivabradine treatment did not differ significantly between groups. The moderate but significant reduction of heart rate by 7 beats/min did not affect hemodynamics or disease severity.

Staphylococcus aureus α-toxin triggers the synthesis of B-cell lymphoma 3 by human platelets.

The frequency and severity of bacteremic infections has increased over the last decade and bacterial endovascular infections (i.e., sepsis or endocarditis) are associated with high morbidity and mortality. Bacteria or secreted bacterial products modulate platelet function and, as a result, affect platelet accumulation at sites of vascular infection and inflammation. However, whether bacterial products regulate synthetic events in platelets is not known. In the present study, we determined if prolonged contact with staphylococcal α-toxin signals platelets to synthesize B-cell lymphoma (Bcl-3), a protein that regulates clot retraction in murine and human platelets. We show that α-toxin induced α(IIb)ß(3)-dependent aggregation (EC(50) 2.98 µg/mL ± 0.64 µg/mL) and, over time, significantly altered platelet morphology and stimulated de novo accumulation of Bcl-3 protein in platelets. Adherence to collagen or fibrinogen also increased the expression of Bcl-3 protein by platelets. α-toxin altered Bcl-3 protein expression patterns in platelets adherent to collagen, but not fibrinogen. Pretreatment of platelets with inhibitors of protein synthesis or the mammalian Target of Rapamycin (mTOR) decreased Bcl-3 protein expression in α-toxin stimulated platelets. In conclusion, Staphylococcusaureus-derived α-toxin, a pore forming exotoxin, exerts immediate (i.e., aggregation) and prolonged (i.e., protein synthesis) responses in platelets, which may contribute to increased thrombotic events associated with gram-positive sepsis or endocarditis.

Glycation of PDGF results in decreased biological activity.

Advanced glycation end products (AGEs) are formed by the non-enzymatic glycation of proteins by reducing carbohydrates or alpha-oxo-aldehydes such as glyoxal and methylglyoxal and further rearrangements, eliminations and oxidations. AGE-modifications alter peptide structure, function and stability and accumulate under several pathophysiological conditions such as diabetes and are considered a biomarker of ageing. PDGF is a major regulator of wound healing, which is impaired in hyperglycaemia and ageing. We analyzed whether glycated PDGF has impaired activity in cell culture models and occurs in human subjects. PDGF was AGE-modified by the alpha-oxo-aldehydes glyoxal and methylglyoxal, which was shown by Western-blotting using alpha-carboxymethyllysine (CML) or alpha-arginine-pyrimidine (Arg-Pyr) antibodies. In mouse AKR-2B fibroblasts, this AGE-modified PDGF exhibited reduced signalling to AKT and ERK resulting in decreased cell proliferation. In the human osteosarcoma cell line 143B, PDGF signalling towards the AKT-kinase was decreased when using modified PDGF-AA, -AB, and -BB whereas the constitutive active ERK was not affected. Secreted proteins from collagen-activated platelets from diabetic subjects contained more CML-modified proteins compared to healthy controls. PDGF protein as a platelet protein coprecipitated in immunoprecipitation experiments with alpha-CML-antiserum. In summary, our data suggest that AGE-modification of PDGF contributes to reduced wound healing in diabetic patients.

Influence of systemically given placebo, trapidil and isosorbide dinitrate on norepinephrine-evoked hand vein constriction in healthy subjects.

Since trapidil (CAS 15421-84-8) is able to dilate human hand veins after local intravenous administration, four studies were carried out in healthy male volunteers using the dorsal hand vein compliance technique to test the influence of common systemic single doses of trapidil (200 mg orally, 100 mg intravenously) and isosorbide dinitrate (CAS 87-33-2, 20 mg orally) on norepinephrine (CAS 51-41-2)-evoked hand vein constriction in comparison with oral placebo. Oral placebo and oral trapidil were studied in a randomized double-blind cross-over design in 10 subjects aged 20 to 30 years, and oral isosorbide dinitrate and intravenous trapidil, in a randomized open cross-over design in 8 subjects aged 22 to 29 years. In the three similar studies with oral medications dose-response curves for venoconstriction by locally infused norepinephrine were established before and 1 h, 2 h and 3 h after oral medication and ED50 values of norepinephrine were calculated. The control dose-response curves and ED50 values of norepinephrine did not differ significantly. After oral placebo administration the dose-response curves of norepinephrine did not change significantly, but the ED50 of norepinephrine increased 3 h after placebo (from 12.1 to 31.7 ng/ min), indicating a lessening in norepinephrine effect at this time. After oral trapidil application the dose-response curves of norepinephrine shifted to the left compared with the pre-treatment curve (significantly 2 h after trapidil) and the corresponding curves after placebo with a significant decrease in the ED50 of norepinephrine 3 h after trapidil compared with placebo (from 31.7 to 12.6 ng/ min). After oral isosorbide dinitrate administration the dose-response curves of norepinephrine did not differ significantly from the pre-treatment curve, but they shifted to the left compared with the corresponding curves after placebo (significantly 3 h after isosorbide dinitrate). The ED50 of norephinephrine decreased significantly 2 h after isosorbide dinitrate compared with the pre-treatment value (from 9.4 to 3.3 ng/min) as well as 1 h, 2 h and 3 h after isosorbide dinitrate compared with placebo (from 32.4/21.3/31.7 to 7.3/3.3/6.0 ng/min). Therefore, oral trapidil and isosorbide dinitrate did not weaken norepinephrine-evoked hand vein constriction as expected but strengthened it slightly. Intravenously given trapidil led only to an insignificant short decrease followed by an insignificant increase in permanent venoconstriction due to local norepinephrine infusion. The data suggest that after systemic administration of trapidil or isosorbide dinitrate a hand vein constriction, which could be a reflex consequence of a drug-induced decrease in central venous pressure, exceeds an only discreet direct hand vein dilation.

P2Y12 ADP receptor-dependent tyrosine phosphorylation of proteins of 27 and 31 kDa in thrombin-stimulated human platelets.

In thrombin-stimulated human platelets several proteins undergo rapid and transient changes in tyrosine phosphorylation. We demonstrate that a set of proteins of 27, 29, 31, 34, and 39 kDa is affected by released ADP and P2Y12 receptor signaling during platelet activation. AR-C69931MX, an antagonist of the Gi(2)-coupled P2Y12 ADP receptor, inhibits initial tyrosine phosphorylation of p27 and p31 and prevents subsequent dephosphorylation of p29, p34, and p39. Antagonists of the Gq-coupled P2Y1 ADP receptor have no effect. Precluding integrin alpha(IIb)beta(3) outside-in signaling with RGDS or S1197 does not affect the increase in tyrosine phosphorylation of the set of proteins but inhibits their subsequent dephosphorylation. Besides the ADP analogue 2-MeS-ADP, other platelet agonists such as collagen and the TXA(2)-mimetic U46619 also induce p27 and p31 tyrosine phosphorylation in a P2Y12 receptor-dependent manner. Tyrosine phosphorylation of p27 and p31 in response to collagen, but not thrombin, is prevented by aspirin and the TXA(2) receptor antagonist SQ29548, indicating that the effect of collagen strongly relies on TXA(2) signaling. Furthermore, epinephrine, acting via inhibitory Gz-coupled alpha(2A)-adrenoceptors, bypasses the inhibitory effect of AR-C69931MX on thrombin-induced p27 and p31 tyrosine phosphorylation. Finally, we demonstrate that tyrosine phosphorylation of p27 and p31 downstream of P2Y12 receptors is due to the inhibition of adenylyl cyclase but not phosphoinositide 3-kinase (PI 3-K) activation. Elevating cAMP levels with PGI(2) or forskolin precludes thrombin-induced p27 and p31 tyrosine phosphorylation. Moreover, direct inhibition of adenylyl cyclase by SQ22536 reverses the effect of AR-C69931MX. Our data indicate that the observed changes in tyrosine phosphorylation are the result of both primary Gq signaling, initiating the release of ADP, as well as subsequent P2Y12 receptor-mediated Gi coupling.

ADP secretion and subsequent P2Y12 receptor signalling play a crucial role in thrombin-induced ERK2 activation in human platelets.

Stimulating human platelets with thrombin induces the activation of the extracellular signal-regulated kinase 2 (ERK2). We demonstrate that this effect is highly dependent on ADP secretion and P2Y12 receptor signalling. AR-C69931MX (10 microM), a specific antagonist of the Gi-coupled P2Y12 ADP receptor, inhibits ERK2 activation induced by thrombin. Antagonists of the Gq-coupled P2Y1 ADP receptor, A3P5P (500 microM) and MRS2179 (100 microM), have no effect. ADP and its more potent analogue 2-methylthio-ADP alone (both up to 100 microM) do not induce ERK2 activation. Furthermore, we show that the inhibitory effect of AR-C69931MX on ERK2 activation induced by 0.1 U/ml thrombin as well as on platelet aggregation can be bypassed by epinephrine (1 and 10 microM), whereas epinephrine alone has no effect. Epinephrine acts on platelets mainly via alpha(2A)-adrenergic receptors, which, like P2Y12 receptors, couple to inhibitory G proteins. In addition, 2-methylthio-ADP as well as epinephrine provoke ERK2 activation at a thrombin concentration that alone has no detectable effect (0.05 U/ml). Thromboxane A2 (TXA2), which, like ADP, is released by activated platelets, acts as a positive feedback mediator. Stimulating the Gq-coupled TXA2 -receptor with U46619 (10 microM), which leads to ADP secretion and P2Y12 receptor-dependent platelet aggregation, also induces P2Y12-related ERK2 activation. The inhibition of U46619-induced ERK2 activation and platelet aggregation by AR-C69931MX are also rescued by epinephrine. Pretreatment with aspirin inhibits ERK2 activation induced by 0.1 U/ml thrombin, but has no effect at high concentrations of thrombin. The combination of U46619 and thrombin, at concentrations which alone have no effect, provokes ERK2 activation, suggesting that thrombin and released TXA2 act synergistically. Our data indicate that both primary signalling through Gq, which evokes ADP secretion, as well as subsequent coupling via Gi by the P2Y12 receptor are required for ERK2 activation.