The Role of IKK-2/NF-κB Signaling Cascade in the Activation of Peritoneal Macrophages by Humic Acids of Peat

Abstract

Introduction. Macrophages occupy a special place in the formation and coordination of the immune response, their population is characterized by heterogeneity, however, two main types are distinguished among them: pro-inflammatory (classically activated) macrophages M1, which are activated by interferon-γ (IFN-γ) or lipopolysaccharide (LPS) of bacteria, produce pro-inflammatory cytokines, nitric oxide (NO) and initiate an immune response, and anti-inflammatory (alternatively activated) macrophages M2, which are activated by such cytokines as interleukin 1 (IL-1), IL-10 or IL-13 and are associated with suppression of the immune response and tissue healing. The proinflammatory properties of macrophages are most often associated with the activation of an intracellular signaling cascade with the participation of the IKK-2 kinase complex and nuclear factor-κB (NF-κB), which is the most important signal transduction molecule. Previously, the authors showed that humic acids (HA) of peat cause the appearance of pro-inflammatory properties in macrophages; however, the intracellular mechanisms of such activation have not been studied.Aim. Study of the contribution of the intracellular signaling cascade IKK-2/NF-κB to the activation of pro-inflammatory properties of macrophages by humic acids of peat.Materials and methods. The studies were carried out using cultural methods and western blotting.Results and discussion. It was shown that the addition of the IKK-2 inhibitor to the macrophage culture reduced the ability of HA to stimulate the production of nitric oxide by the cells. Western blotting revealed that after 30 minutes simultaneous incubation of HA with macrophages, the content of the NF-κB p65 molecule in the cells increased, after 60 minutes it decreased to the values of intact control, and after 17 hours it decreased 3 times compared to the control level. However, the IKK-2 inhibitor after a 30-minutes incubation did not have a blocking effect on the IKK kinase, whereas in an hour of the co-incubation of the cells with the inhibitor and substances, a decrease in the level of NF-κB p65 was observed. This trend continued in 17 hours.Conclusion. The stimulating effect of peat humic acids on macrophages is realized, among other things, due to the activation of the IKK-2 kinase complex with further release of the p65 subunit of the NF-κB molecule. The dependence of the degree of NF-κB activation on the period of interaction of the cell with activating agents is traced. HA start the intracellular signaling cascade of the nuclear factor NF-κB already within the first 30 minutes.

Keywords

• humic acids
• nitric oxide
• ikk-2
• nf-κb
• immunoblotting