Immunoreactivities of NF-κB, IL-1β and IL-1R in the skin of Chinese brown frog (Rana dybowskii)

The cytokine interleukin-1 beta (IL-1β) is an evolutionarily conserved molecule that was originally identified in the immune system. Nuclear factor κB (NF-κB) plays a critical role in the activation of immune cells by upregulating the expression of many cytokines. In this study, we investigated the localization and expression level of IL-1β, its functional membrane receptor type I (IL-1R1) and NF-κB in the skin of Rana dybowskii during the breeding period and pre-hibernation. Histologically, the skin of Rana dybowskii consists of epidermis and dermis, and four kinds of cells were identified in the epidermis during the breeding period and pre-hibernation, while the dermis was composed of homogenous gel, mucous glands and granular glands. IL-1β, IL-1R1 and NF-κB were immunolocalized in the epithelial and glandular cells in both periods. Western blotting showed that there was no significant difference in the expression of IL-1β between the breeding period and pre-hibernation, whereas IL-1R1 and NF-κB were significantly higher in the pre-hibernation compared to the breeding period. These results suggested that IL-1β and NF-κB may collectively play important roles in the skin immune system of Rana dybowskii during the breeding period and pre-hibernation.