In vitro leishmanicidal activity of antimicrobial peptide KDEL against Leishmania tarentolae

Leishmaniasis, caused by the intracellular protozoan parasite Leishmania, remains an important neglected tropical infectious disease. Infection may be lethal if untreated. Currently, the available drugs for the disease are limited by high toxicity and drug resistance. There is an urgent need to develop novel anti-leishmanial strategies. Antimicrobial peptides (AMPs) have been described as the first-line immune defense against pathogenic microbes and are being developed as emerging anti-parasitic therapies. In the present study, we showed the anti-leishmanial activity of the synthetic 4-amino acid peptide lysine, aspartic acid, glutamic acid, and leucine (KDEL), the endoplasmic reticulum retention sequence, against Leishmania tarentolae promastigote and amastigote. Different concentrations of KDEL peptides were incubated with promastigotes, MTT viability assay, and promastigote assay were carried out. Macrophages infected with GFP-transfected L. tarentolae promastigotes were incubated with KDEL peptides, and the anti-amastigote activity of the KDEL peptides was measured by fluorescence microscopy. The damage of L. tarentolae was observed by light microscopy and electron microscopy. The cell apoptosis was analyzed using the Annexin V-FITC/PI apoptosis detection kit and mitochondrial membrane potential assay kit and by flow cytometry. Results showed that L. tarentolae was susceptible to KDEL peptides in a dose-dependent manner, and KDEL peptides disrupted the surface membrane integrity and caused cell apoptosis. In our study, we found for the first time an AMP KDEL from Pseudomonas aeruginosa and proved its significant therapeutic potential as a novel anti-leishmanial drug.