Cytotoxic effect of Melittin peptide; major pain producing substance in European honeybee (Apis mellifera) venom on leishmaniasis parasite Leishmania donovani

Abstract

Melittin is a peptide in the venom of the European honeybee (Apis melifera). It has indicated various therapeutic effects including parasitic infections. Leishmaniasis is a parasitic disease caused by a protozoan parasite under the genus Leishmania. In Sri Lanka, Leishmania donovani is the parasite causing leishmaniasis of cutaneous origin. This study evaluates the anti-leishmanial property of melittin peptide against the L. donovani parasite. L. donovani promastigote cultures were established in M119 medium (HIMEDIA, Cat # AL189) supplemented with 20% fetal bovine serum (FBS, Sigma, Cat # F4135) at room temperature (26-300C). A standard series of Melittin peptide was prepared (30, 45, 60, 75, 90, 105, 120, 135, 150, 165 and 180 g/mL). Cytotoxicity for each concentration was assessed using an MTT (4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay by introducing stationary phase parasites at a concentration of 2 × 10⁶ cells/mL into each well of a 96-well flat-bottom microtiter plate. The experiment setup was repeated 12 times in each concentration for 24 and 48-hour incubation separately at room temperature (26-300C). The relative amount of formazan produced by viable cells in each well was quantified by measuring absorbance at 590 nm using an ELISA plate reader. Cell viability was assessed from the concentration-response curve, and the IC50 value was calculated. The highest toxicity was identified at 180 g/mL at 24 h (96.28  3.71%) and 48 h (96.12  0.44 %) periods. However, 50% mortality of the parasites were identified at 50.25 g/mL, and 50.50 g/mL concentration at 24 h and 48 h periods. The results revealed that the proliferation of L. donovani promastigote was inhibited in a dose-dependent manner, and the IC50 value of Melittin was denoted as 50.32 mg/mL, indicating an anti-leishmanial property.