Ajoene could be useful to prevent the thrombotic microangiopathy that complicates attempts to induce chimerism in pig-to-baboon xenotransplantation
Introduction 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. Since a thrombotic microangiopathy frequently complicates procedures designed to induce pig-to-baboon chimerism by infusion of large amounts of p-PBMC in baboons, it was thought that ajoene might be useful to prevent such complication. Therefore, 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).
Materials and methods Monolayers of HUVEC were cultured with p-PBMC or TNFα for 5 h and the expression of HUVEC's E-selectin and VCAM-1 was measured by an immunoassay. To study the effect of Ajoene, HUVEC were incubated for 20 min with ajoene at different concentrations, washed, and incubated with p-PBMC or TNFα. In another set of experiments, HUVEC were incubated 20 min with Ajoene (25 μM), washed and after 20 min, 2, 4 or 5 h, were cultured with p-PBMC or TNFα. The effect of Ajoene on the viability of HUVEC was studied with MTS/PMS standard methods.
Results p-PBMC activate HUVEC as shown by over-expression of E-selectin and VCAM-1. Ajoene (25 mM) inhibit HUVEC activation induced by TNFa or p-PBMC as shown by a down regulation of VCAM-1 (Fig. A) and E-selectin (Fig. B) expression. After 5 h of pretreatment with Ajoene, HUVEC incubated with TNF and p-PBMC showed E-selectin expression at levels similar to the positive control indicating that the inhibitory effect is transient (Fig. B). Ajoene at concentration of 25 mM or lower did not affect HUVEC viability.
Conclusions Ajoene showed a strong, although transient for E-selectin, inhibitory effect on the activation of the endothelium induced by pig cells. Therefore, Ajoene could be useful to prevent the development of microangiopathy and thrombotic disorders seen in primates infused with pig cells.