Antimicrobial peptides (AMPs) are molecules present in innate immune systems of vertebrates and invertebrates. These small peptides inhibit the growth of pathogens invading host's body. In this study, the toxicity effect of Temporin-Ra (T-Ra) antimicrobial peptide on A549 cell line was investigated by MTT assay. Furthermore, the toxicity of T-Ra peptide on human's red and white blood cells was investigated. Gene expression levels of TNF-α (tumor necrosis factor-alpha)aspro-inflammatory cytokine, and CD44 cancer marker were investigated by real time- PCR, 48 h after treatment of A549 cells by different concentrations of peptide. Moreover, the production of reactive oxygen species was studied by flow cytometer. According to our results, T-Ra viability of A549 cells decreased up to 15%, while had no hemolytic and cytotoxic effects on human blood cells. In addition, T-Ra increased the expression of pro- inflammatory cytokine (TNF-α) at the highest concentration (30 μg/ml), while decreased gene expression of CD44 cancer marker. Production of reactive oxygen species (ROS) in A549 cells treated by T-Ra significantly increased. In conclusion, our results revealed that T-Ra could induce the expression of TNF-α, which consequently decrease CD44 expression, increase the production of reactive oxygen species, and as a result induced death in A549 cell lines

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