FIGURE 1.

Insect CAMPs selectively induce parasite reductase activity and ATP production in conditioned medium. A, trypanosomal viability assay based on MTT reductase activity (9) in the presence of parasite-conditioned medium (CM), fresh non-conditioned parasite growth medium (NCM) at indicated amounts of insect-derived (CAMEL), and mammalian-CAMP (the cathelicidin, CRAMP) (60) in 100 μl. The effects of α-defensin (cryptdin-4) and β-defensin-3, the cathelicidin, protegrin-1, and amphibian-pexiganan (8) were similar to CRAMP and are not shown. B, cross-stimulation of CAMEL-induced reductase activity among different parasite strains (CL and Brazil (BR)) as indicated. Control reactions of MTT reductase activities of parasites in NCM or CM or alone were not significantly different (not shown). C, the effect of a P6 subfragment of trialysin (6) (P6-trialysin) (shown in μg) compared with CAMEL on parasite reductase activity. D, P6-trialysin and CAMEL treatment (3.5 μg each) in CM of the Brazil strain T. cruzi increased the ATP content ∼3.5–5-fold over that of cells in medium alone (no Rx); untreated cells in CM and NCM alone had similar ATP content (not shown). The inset table shows MTT reductase activity and ATP content of stationary-phase parasites in in vitro reactions with 3.5 μg of P6-trialysin in CM from Brazil strain compared with those in which parasites were preincubated for 30 min with the mitochondrial poison carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) (10 μm) before the assay. Parasites were treated under the indicated conditions for 2 h and then subjected to the MTT reductase assay, which is calculated based on % MTT conversion to formazan over 24 h compared with the untreated stationary-phase parasites in control reactions that retain full viability (taken as 100%). Activity is expressed as the mean % of untreated controls ± S.D. (n = 9 for experiments in panels A–C, n = 6 for those on panel D).