αB-crystallin reduces ristocetin­induced soluble CD40 ligand release in human platelets: suppression of thromboxane A2 generation.

Our group has previously shown that αB-crystallin (HSPB5), a small heat shock protein, inhibits human platelet aggregation by ristocetin, an activator of glycoprotein Ib/IX/V. In addition, it was demonstrated that glycoprotein Ib/IX/V activation induces soluble CD40 (sCD40) ligand release via thromboxane (TX) A2. In the present study, the effect of αB-crystallin on the ristocetin-induced sCD40 ligand release in human platelets was investigated. The ristocetin-induced release of sCD40 ligand was suppressed by αB-crystallin. In addition, αB-crystallin reduced the ristocetin-stimulated production of 11-dehydro-TX B2, a stable metabolite of TXA2. αB-crystallin did not suppress the platelet aggregation induced by U46619, a TXA2 receptor agonist. αB-crystallin had little effect on the U46619-induced phosphorylation of p38 mitogen-activated protein kinase or sCD40 ligand release. In addition, αB-crystallin failed to reduce the binding of SZ2, a monoclonal antibody against the sulfated sequence in the α-chain of glycoprotein Ib, to the ristocetin-stimulated platelets. These results strongly suggest that αB-crystallin extracellularly suppresses ristocetin-stimulated release of sCD40 ligand by inhibiting the TXA2 production in human platelets.

[Preclinical toxicological study of the new antibiotic eremomycin. Its acute toxicity for laboratory animals]. / Doklinicheskoe toksikologicheskoe izuchenie novogo antibiotika éremomitsina. Ostraia toksichnost' dlia laboratornykh zhivotnykh.

Eremomycin is relatively low toxic. LD50 of eremomycin on its intravenous administration to albino mice amounted to 1760 (1460-2130) mg/kg. It is 2.6, 3.5 and 6 times less toxic than ristomycin, vancomycin and teicoplanin, respectively. The rate of intravenous administration had no significant effect on eremomycin toxicity. Sensitivity of adult and preadolescent mice to eremomycin was almost the same. Eremomycin toxicity for male mice was somewhat higher than that for female mice. The use of 5 per cent glucose solution instead of distilled water as a solvent lowered 1.3-fold the toxicity of eremomycin in albino mice when it was administered intravenously. The toxic effect of eremomycin on the renal function played a significant role in the mechanism of the animal death due to the antibiotic. In experiments with guinea pigs eremomycin showed no allergenic effect. Unlike the other representatives of glycopeptide antibiotics, eremomycin had practically no local irritating effect which provided its recommendation for clinical trials not only as an intravenous but also intramuscular antibiotic.