Effects of alpha- and beta-adrenergic agonists on Trypanosoma cruzi interaction with host cells

We studied the effects of adrenergic agonists on the capacity of blood trypomastigote forms of Trypanosoma cruzi to associate with (i.e., bind and/or penetrate) host cells in vitro. The extent of T. cruzi association with mouse macrophages in the presence of the beta-adrenergic agonist L-isoproterenol was significantly decreased with respect to mock-treated controls. Similar results were obtained when the parasite was pretreated with L-isoproterenol and was then allowed to interact with untreated macrophages. In contrast, pretreatment of trypomastigotes with either L-phenylephrine or methoxamine-alpha-adrenergic agonists--enhanced their reactivity with macrophages. Interaction with a nonphagocytic host cell was also decreased and increased by parasite pretreatment with beta- and alpha-adrenergic agonists, respectively. The L-isoproterenol and L-phenylephrine effects were no longer detectable 2 and 3 hr after their removal, respectively, and were therefore reversible. Atenolol, a specific beta 1 adrenoreceptor blocker inhibited the L-isoproterenol effect, whereas butoxamine, a specific beta 2 blocker, did not. Thus, beta 1-like but not beta 2-like binding sites appeared to be expressed on T. cruzi. Both prazosin and yohimbine, preferential alpha 1- and alpha 2-receptor blockers, respectively, abolished the L-phenylephrine effect. The opposite effects of alpha- and beta-adrenergic agonists suggested that the infectivity of T. cruzi may be regulated by activation of surface components comparable to the adreno-receptors.(ABSTRACT TRUNCATED AT 250 WORDS)