Interleukin-23 reshapes kidney resident cell metabolism and promotes local kidney inflammation.

Interstitial kidney inflammation is present in various nephritides in which serum IL-23 is elevated. Here we show that IL-23 receptor (IL-23R) expressing murine and human renal tubular epithelial cells (TEC) respond to IL-23 by inducing intracellular calcium flux, enhanced glycolysis, and the upregulation of calcium/calmodulin kinase IV (CaMK4) which results in suppression of the expression of the arginine degrading enzyme arginase 1 (ARG1) thus increasing in situ levels of free L-Arginine (Arg). Limited availability of Arg suppresses the ability of infiltrating T cells to proliferate and produce inflammatory cytokines. TEC from humans and mice with nephritis express increased levels of IL-23R and CaMK4 but reduced levels of ARG1. TEC-specific deletion of Il23r or Camk4 suppressed inflammation whereas deletion of Arg1 exacerbated inflammation in different murine disease models. Finally, TEC-specific delivery of a CaMK4 inhibitor specifically curbed the renal inflammation in lupus-prone mice without affecting systemic inflammation. Our data offer first evidence on the immunosuppressive capacity of TEC through a mechanism that involves competitive uptake of Arg and signify the importance of modulation of an inflammatory cytokine on the function of non-lymphoid cells, which leads to the establishment of an inflammatory microenvironment. New approaches to treat kidney inflammation should consider restoring the immunosuppressive capacity of TEC.