Involvement of NF-κBIZ and related cytokines in age-associated renal fibrosis

Chronic inflammation is a major contributor to age-related nephropathic changes, including renal fibrosis. In this study, various experimental paradigms were designed to delineate the role played by NF-?BIZ (also known as I?B?) in age-associated renal fibrosis. Analyses based on RNA-sequencing findings obtained by next generation sequencing (NGS) revealed the upregulations of NF-?BIZ and of IL-6 and MCP-1 (both known to be regulated by NF-?BIZ) during aging. The up-regulation of NF-?BIZ in aged rat kidneys coincided with increased macrophage infiltration. In LPS-treated macrophages, oxidative stress was found to play a pivotal role in NF-?BIZ expression, suggesting age-related oxidative stress is associated with NF-?BIZ activation. Furthermore, these in vitro findings were confirmed in LPS-treated old rats, which showed higher levels of oxidative stress and NF-?BIZ in kidneys than LPS-treated young rats. Additional in vitro experiments using macrophages and kidney fibroblasts demonstrated NF-?BIZ and related cytokines participate in fibrosis. In particular, increased levels of NF-?BIZ-associated cytokines in macrophages significantly up-regulated TGF-β induced kidney fibroblast activation. Moreover, experiments with NF-?BIZ knocked down macrophages showed reduced TGF-β- induced kidney fibroblast activation. The findings of the present study provide evidence regarding an involvement of NF-?BIZ in age-associated progressive renal fibrosis and provides potential targets for its prevention.