Effects Of Ajoene Research Articles

Ajoene inhibits the activation of human endothelial cells induced by porcine cells: implications for xenotransplantation.

Ajoene, is an organosulfur compound derived from garlic that strongly inhibit platelet aggregation, proliferation of human lymphocytes induced by phytohemagglutinin, and in general, blocks membrane-mediated signaling of cell activation. As a thrombotic microangiopathy frequently complicates procedures designed to induce pig-to-baboon chimerism by infusion of large amounts of pig progenitor cells in baboons, it was thought that ajoene might be useful to prevent such complication. For such purpose, we studied the effects of ajoene on the activation of human umbilical vein endothelial cells (HUVEC) induced by pig peripheral blood mononuclear cells (p-PBMC). Co-cultures of p-PBMC with HUVEC results in activation of the HUVEC as shown by over-expression of E-selectin and vascular cells adhesion molecule-1 (VCAM-1). Ajoene (25 microm) strongly inhibits HUVEC activation induced by tumor necrosis factor-alpha (TNF-alpha) or p-PBMC as shown by a down regulation of VCAM-1 and of E-selectin expression. After 5 or 8 h of pre-treatment with Ajoene, HUVEC incubated with TNF and p-PBMC showed an E-selectin or VCAM-1 expression, respectively, at levels similar to the positive control indicating that the inhibitory effect is transient. Ajoene at concentration of 25 microm or lower did not affect HUVEC viability. Based on the finding that Ajoene has a strong, although transient, inhibitory effect on the activation of the endothelium induced by pig cells and its known anti-platelet activity, it is suggested that this garlic compound could be useful to prevent the development of microangiopathy and thrombotic disorders seen in primates infused with pig cells.

Inhibition by ajoene of protein tyrosine phosphatase activity in human platelets

The effects of ajoene (a potent antithrombotic agent obtained from garlic) on the tyrosine phosphorylation status of human platelet proteins were investigated by immunoblotting-based experiments using an anti-phosphotyrosine antibody. Incubation of platelets with ajoene enhanced the phosphorylation of at least four proteins (estimated MWs 76, 80, 84 and 120 kDa), both in resting platelets and in platelets subsequently stimulated with thrombin (0.1 U/ml). This effect was both dose- and incubation-time-dependent. High concentrations of ajoene (50 μM) or long periods of incubation (10 min) led to nonselective `hyperphosphorylation' of numerous proteins. The effects of ajoene on protein tyrosine phosphatase (PTP) activity in platelet lysates were also investigated. PTP activity was inhibited when platelets were incubated with ajoene before lysis, but not when ajoene was added to lysates of platelets which had not been pre-exposed to ajoene.

Effects of Ajoene on Lymphocyte and Macrophage Membrane-Dependent Functions

Ajoene, (E,Z) -4,5,9-trithiadeca-1,6,11-triene 9 oxide, is a compound originally isolated from ethanolic extracts of garlic that impairs platelet aggregation by inhibiting the functional exposure of platelet integrins GPIIb/IIIa. In vitro, Ajoene is toxic for several tumoral cell lines, and exert an antiproliferative effect on T. cruzi and murine malaria parasites. Here we show that Ajoene strongly inhibited the proliferation induced in human lymphocytes by the mitogens phytohemagglutinin (PHA), phorbol myristate acetate (PMA) and anti-CD3, and the capping formation induced in B lymphocytes by anti-IgM antibodies. On macrophages, Ajoene was also found to partially inhibit the lypopolysaccharide-induced production of Tumor Necrosis Factor (TNF), and to decrease the phagocytic activity of thioglycolate-elicited mouse peritoneal macrophages for IgG-opsonized, human erythrocytes. Ajoene also partially prevented the lytic effect of human and rabbit TNF on Actinomycin D-treated WEHI 164 cells. These results strongly suggest that Ajoene is a potent modulator of membrane-dependent functions of immune cells.