Figure 10
Validation of phenylethylamide (PEA) compounds for their inhibitory activities against 5-HTR using derivatives with different side chains (‘X’ and ‘Y’ of PEA skeleton). (a) Screening of 45 PEA derivatives for their effects on hemocyte phagocytosis of S. exigua with HB 44, a potent bacterial metabolite, as reference. PEA compounds (300 ng/larva) were injected into hemocoels of L5 larvae along with FITC-tagged bacteria. After incubating for 15 min, hemocytes were assessed for phagocytosis. Asterisks above standard deviation bars indicate significant difference compared to control (‘CON’ without inhibitor) at Type I error = 0.05 (*), 0.01 (**), and 0.005 (***) (LSD test). (b) Chemical structures of three selected PEA compounds and their median inhibitory doses (IC50). (c) Competitive inhibition of the three selected PEA derivatives with 5-HT against Se-5HTR mediated phagocytosis. For dose-response analysis of inhibitory compounds (0, 0.3, 3, 30, and 300 ng/larva), a fixed 5-HT concentration (1 µg/larva) was used. For dose-response of 5-HT (0, 2, 20, 200 and 2,000 ng/larva), a fixed HB compound concentration (1 µg/larva) was used. ‘CON’ represents a positive control without any inhibitor.
