S1P-sPRR axis in renal ischemia-reperfusion injury: inflammation via a cut.

Inflammation is a determining factor in acute kidney injury (AKI) and subsequent kidney repair, yet its regulation is complicated and incompletely understood. In this issue, Feng and colleagues report that site-1 protease (S1P)-dependent cleavage of the (pro)renin receptor (PRR/ATP6AP2) generates soluble PRR (sPRR), which functions as an inflammation amplifier in ischemic AKI. Remarkably, S1P inhibition pharmacologically or genetically suppresses sPRR production and attenuates macrophage infiltration and activation, blunting AKI. The work elevates sPRR from a putative biomarker to a mechanistically active mediator of AKI. It also couples innate immune programming to local renin-angiotensin system engagement, suggesting an immuno-endocrine cross-talk and modulation in the kidney.