Levamisole inhibits in vivo rat platelet aggregation by a release of prostacyclin-like factor

Signal transduction in Plasmodium-Red Blood Cells interactions and in cytoadherence

Malaria is responsible for more than 1.5 million deaths each year, especially among children (Snow et al. 2005). Despite of the severity of malaria situation and great effort to the development of new drug targets (Yuan et al. 2011) there is still a relative low investment toward antimalarial drugs. Briefly there are targets classes of antimalarial drugs currently being tested including: kinases, proteases, ion channel of GPCR, nuclear receptor, among others (Gamo et al. 2010). Here we review malaria signal transduction pathways in Red Blood Cells (RBC) as well as infected RBCs and endothelial cells interactions, namely cytoadherence. The last process is thought to play an important role in the pathogenesis of severe malaria. The molecules displayed on the surface of both infected erythrocytes (IE) and vascular endothelial cells (EC) exert themselves as important mediators in cytoadherence, in that they not only induce structural and metabolic changes on both sides, but also trigger multiple signal transduction processes, leading to alteration of gene expression, with the balance between positive and negative regulation determining endothelial pathology during a malaria infection.

Different patterns of inhibition of adrenaline-induced platelet aggregation and kinetics in vivo by acetylsalicylic acid and indobufen

The inhibitory effect of 50 mg/kg lysyl acetylsalicylic acid (ASA) intravenously injected 24 and 4 h before 80 micrograms/kg adrenaline, 40 mg/kg indobufen injected 15 min before, or a combination of ASA plus indobufen on the platelet aggregation and kinetics was evaluated in anaesthetized dogs previously injected with 111indium- (111In-) labelled platelets using gamma-camera dynamics studies. The highest degree of inhibition, indicated by the lowest platelet aggregation ratio decrease and the most significant 111In-labelled platelet mobilization from hepatic and splenic stores with a corresponding increase of labelled and unlabelled platelet counts in blood, was obtained in ASA-treated dogs. Such changes were less marked when ASA plus indobufen was injected. In indobufen-treated dogs a similar mobilization of 111In-labelled platelets with an increase in circulating platelet numbers was evident only after the second adrenaline injection. It is concluded that platelet mobilization is mainly dependent on the production of an ASA-sensitive substance.

Role of levamisole as immunomodulant in mouse lymphoma model

Levamisole (LMS) has been considered an immunorestorative agent capable of enhancing host's antitumor immune responses. Clinical studies showed that LMS plays a significant role in adjuvant chemotherapy of colorectal cancer. Therefore studies were performed to test whether LMS would be able to restore graft responsiveness in mice with drug-dependent, age-dependent or virus-dependent immunodeficiency. The results show that LMS has little or no influence on the limited antitumor effects of Dacarbazine or Ara-C in mice bearing allogeneic leukemias (i.e. in a host-tumor model in which immuno-chemotherapy synergism occurs with less immunodepressive anticancer drugs). Moreover LMS does not alleviate allograft response inhibition produced by high-dose Dacarbazine or by a mouse RNA virus. However the agent restored graft responsiveness in aged animals. The limited immunoenhancing effects of LMS, as detected in the present study, suggest that the clinical efficacy of the agent could be due to mechanisms not entirely related to its immunopharmacological properties.