Cell experiment:

Briefly, 5 × 105 cells/mL in RPMI 1640 supplemented with 10% heat-inactivated FCS are placed onto 96-well plates. Cecropin A is added to cell cultures at a final concentration of 10, 20, 30, 40 and 50 μM and cells are incubated for 24 h at 37℃ in a humidified atmosphere with 5% CO2. Then, 20 μL MTT (0.5 mg/mL) is added to each well and the plate is incubated for 4 h at 37℃. The MTT solution is removed and isopropyl alcohol containing 0.04 N hydrochloric acid is added to each well to dissolve the formazan crystal. Absorbance is determined on a spectrophotometric microplate reader at a test wavelength of 550 nm and a reference wavelength of 620 nm. The absorbance of the cells incubated in the absence of cecropin A (untreated cells) is set at 100%. Results are expressed as percentage of cell viability[1].

Cecropin A is a linear 37-residue antimicrobial polypeptide, with anticancer and anti-inflammatory activity.

Cecropin A shows anticancer activity. Cecropin A (10-50 μM) dose-dependently reduces the viability of HL-60 cells. Cecropin A (30 μM) promotes ROS production, causes mitochondrial membrane potential (δψm) collapse, and generates morphological changes in nuclear chromatin in HL-60 cells. Cecropin A (30 μM) also leads to an early apoptosis and cuases caspase-independent cell death in HL-60 cells[1]. Cecropin A has cytotoxicity on gram negative bacteria, including A. baumanii (CCARM 12005, CCARM 12035, CCARM 12036, CCARM 12037) with minimal inhibitory concentration (MIC) of 0.5-1 μM. Cecropin A (25 μM) significantly blocks the expression of mTNF-α, mIL-1β, and mMIP-2 mRNA and slightly inhibited the expression of mMIP-1 mRNA in RAW264.7 cells. Cecropin A (0.1, 0.25, 0.5, 1, 2.5, 5 μM) also inhibits NO production and reduces mTNF-α cytokine levels in LPS-stimulated RAW264.7 cells, and exihibits anti-inflammatory activity[2].

[1]. Cerón JM, et al. The antimicrobial peptide cecropin A induces caspase-independent cell death in human promyelocytic leukemia cells. Peptides. 2010 Aug;31(8):1494-503. [2]. Lee E, et al. Anti-inflammatory activities of cecropin A and its mechanism of action. Arch Insect Biochem Physiol. 2015 Jan;88(1):31-44.