Effects of cecropin A on cytokine production and tight junction protein expression in chicken ileal explant cultures

In an era of antimicrobial resistance (AMR), identifying alternatives to conventional antibiotics in livestock farming is vital for veterinary medicine and public health. Due to the constant exposure to pathogens and the need for optimal productivity, maintaining gut homeostasis is essential in poultry. Therefore, investigating antimicrobial alternatives that can support gut health is of key importance. Host defense peptides (HDPs) have been identified as promising candidates due to their beneficial effects on the gut; however, there is still much to clarify regarding the individual peptides' mechanism of action. In the present study, the HDP cecropin A (CecA) was applied to chicken-derived ex vivo ileal explant cultures to examine its impact on immune response and tight junction (TJ) protein expression. CecA was applied at 3.125 and 6.25 µg/mL concentrations, either alone (Cec-low and Cec-high) or in polyinosinic-polycytidylic acid (Poly I:C, 50 µg/mL)-induced inflammatory conditions (PI:C + Cec-low and PI:C + Cec-high). The experiment revealed that CecA had no impact on cell viability, as reflected by unchanged metabolic activity and extracellular lactate dehydrogenase activity. Regarding the immune state, Cec-high and PI:C + Cec-high increased the production of interleukin (IL)-2, whereas IL-6 concentration was decreased by PI:C + Cec-low treatment. Furthermore, Cec-high elevated the intracellular expression of the TJ protein claudin-3. In conclusion, CecA displayed immunomodulatory activity in chicken intestinal cells and supported epithelial integrity without exerting cytotoxic effects.