A novel VCP modulator KUS121 exerts renoprotective effects in ischemia-reperfusion injury with retaining ATP and restoring ERAD-processing capacity.

Acute kidney injury (AKI) is a life-threatening condition and often progresses to chronic kidney disease or the development of other organ dysfunction even after recovery. Despite the increased recognition and high prevalence of AKI worldwide, there has been no established treatment so far. The aim of this study was to investigate the renoprotective effect of Kyoto University substance 121 (KUS121), a novel valosin-containing protein modulator, on AKI. In in vitro experiments, we evaluated cell viability and ATP levels of proximal tubular cells with or without KUS121 under endoplasmic reticulum (ER) stress conditions. In in vivo experiments, the effects of KUS121 were examined in mice with AKI caused by ischemia-reperfusion injury. ER-associated degradation (ERAD)-processing capacity was evaluated by quantification of the ERAD substrate CD3delta-YFP. KUS121 protected proximal tubular cells from cell death under ER stress. The apoptotic response was mitigated as indicated by the suppression of C/EBP homologous protein expression and caspase-3 cleavage, with maintained intracellular ATP levels by KUS121 administration. KUS121 treatment suppressed the elevation of serum creatinine and neutrophil gelatinase-associated lipocalin levels and attenuated renal tubular damage after ischemia-reperfusion. The expression of inflammatory cytokines in the kidney was also suppressed in the KUS121-treated group. Valosin-containing protein expression levels were not altered by KUS121 both in vitro and in vivo. KUS121 treatment restored ERAD-processing capacity associated with potentiation of its upstream pathway, phosphorylated inositol-requiring enzyme-1α, and spliced X box-binding protein-1. In conclusion, these findings indicate that KUS121 can protect renal tubular cells from ER stress-induced injury, suggesting that KUS121 could be a novel and promising therapeutic compound for ischemia-associated AKI. NEW & NOTEWORTHY Novel findings of this study are as follows: 1 ) Kyoto University substance 121 (KUS121), a novel valosin-containing protein (VCP) modulator, can reduce ATP consumption of VCP; 2 ) KUS121 reduced endoplasmic reticulum (ER) stress and improved cell viability in proximal tubular cells; 3 ) KUS121 exerted renoprotective effects against ischemia-reperfusion injury; and 4 ) KUS121 may prevent ischemic acute kidney injury with ATP retention and restoring ER-associated degradation capacity.