Veterinary session

The rise of antimicrobial resistance has become a serious problem worldwide, affecting both animal and human health. To solve this problem, the demand for searching for new alternative substances that can replace conventional antibiotics has increased. Antimicrobial peptides (AMPs) are small oligopeptides, naturally occurring in the organism as part of innate immunity. They possess remarkable advantages over antibiotics, as in addition to their direct antimicrobial effect, their propensity to develop resistance is lower, and they can also exert immunomodulatory effects. AMPs offer a favorable solution in the field of veterinary medicine as well, however, there is still only a few literature data available about the effects of these molecules in farm animals at a cellular level.

The liver plays an important role in the maintenance of homeostasis and in inflammatory processes, therefore, in our experiment, the immunomodulatory effects of the insect-derived AMP cecropin A were investigated on a primary hepatocyte-non-parenchymal cell co-culture of chicken origin. During the experiment, cecropin A was used in different concentrations (1; 3.125; 6.25; 12.5 and 25 µg/ml) alone and in polyinosic-polycytidylic acid (Poly I:C, 50 µg/ml)-induced inflammation. After sampling from the supernatant, cell viability was examined by the colorimetric measurement of the extracellular lactate dehydrogenase (LDH) activity. In addition, the effect of cecropin A (1; 3.125 and 6.25 µg/ml) on the immune response was determined by the measurement of the levels of interleukin (IL)-6, IL-10 and interferon (IFN)-γ, using the Luminex method. The concentration of transforming growth factor (TGF)-ß1 was measured with ELISA method.

Based on our results, the lower concentrations of cecropin A (1; 3.125; 6.25 µg/ml) did not affect the LDH activity, however, in the case of its higher concentrations (12.5; 25 µg/ml), a significant decrease was detected in the membrane integrity. At a concentration of 1 µg/ml solely applied cecropin A, and in the case of inflammation induced by Poly I:C, at concentrations of 1 and 6.25 µg/ml – and in the case of IL-6 also at 3.125 µg/ml –, the treatments resulted in a significant decrease in the IL-6, IL-10 and INF-γ production. In the case of TGF-ß1, the addition of a 6.25 µg/ml solution of cecropin A used alone showed a significant reduction in cytokine production.

According to our experiment, cecropin A applied at low concentrations did not affect the viability of the cells, therefore, it might be safely used in the living organism. However, the administration of its higher concentrations should be considered from the point of view of the liver. Based on our results, cecropin A also displayed an immunomodulatory effect on the tested parameters, as it was able to influence the production of IL-6, IL-10, IFN-γ and TGF-ß1. As a consequence, cecropin A might be a promising candidate for the development of new antimicrobial agents in the future.