TDK conference 2022

Nowadays, the increasing spread of antimicrobial resistance (AMR) is a cause of considerable concern, which encourages a lot of research into the development of alternative drugs that can be effectively used to treat bacterial infections and the inflammatory symptoms caused by them. Innate Defense Regulator-1002 (IDR-1002), an antimicrobial peptide (AMP) produced in bovine neutrophil cells, as a derivative of bactenecin, may prove to be a promising candidate for this purpose due to its powerful immunomodulatory effect.

During the course of our work, we studied the immunomodulatory and antioxidant effect of IDR-1002 on hepatocyte - non-parenchymal cell co-cultures of chicken origin in the presence of lipoteicholic acid (LTA)-induced inflammation. LTA was added to the cell cultures at a concentration of 50 µg/ml, and then the LTA-containing nutrient liquid was supplemented with IDR-1002 solution at a concentration of 10, 30, 90 µg/ml. The effect of IDR-1002 was also examined in the above mentioned concentrations on LTA-free cultures, and then the cells were incubated with the supplemented nutrient fluid for 24 hours. The metabolic activity of the cells was assessed with the CCK-8 test, and the degree of membrane damage was assessed by measuring the activity of the lactate dehydrogenase (LDH) enzyme. The immunomodulatory effect was determined by measuring the concentration of interleukin (IL)-6 and interleukin (IL)-8, and the degree of oxidative stress was determined by measuring the extracellular hydrogen peroxide level.

Based on our results, it can be seen that the metabolic activity of the cells increased significantly after treatment with a high concentration (90 µg/ml) of IDR-1002, while in other cases no deviation was detectable. Supplementation with LTA and IDR-1002 at a concentration of 90 µg/ml significantly increased the LDH enzyme activity of the nutrient medium compared to the absolute control and the control containing only LTA. IDR-1002 applied in all three concentrations significantly reduced IL-6 production compared to the control without LTA as well as both IL-6 and IL-8 production induced by LTA. The cells' H2O2 production was significantly reduced after the application of IDR-1002 at a concentration of 30 µg/ml, in addition, the significant H2O2 emission induced by LTA was successfully reduced by all three concentrations of the peptide.

Overall, we can conclude that although the probability of membrane damage may increase in the case of using a high concentration of IDR-1002, at the same time the metabolic activity of the cells did not show a decrease, thus the peptide cannot be considered cytotoxic. Furthermore, the AMP treatment decreased the production of inflammatory cytokines induced by LTA, and positively influenced the oxidative status of the cells, so we can conclude that the AMP we are examining proves to be a promising candidate for the future therapy of bacterial infections with inflammatory processes.