Regulating the GTP cyclohydrolase 1/tetrahydrobiopterin axis in the distal tubule inhibits ferroptosis and alleviates crush syndrome-related acute kidney injury in mice.

Abstract

Ferroptosis in the proximal tubules has been implicated in the pathogenesis of crush syndrome-related acute kidney injury (CS-AKI). However, whether ferroptosis occurs in the distal tubules and the underlying mechanisms remain unclear. In normal human kidneys, compared with proximal tubules, the ferroptosis driver gene acyl-CoA synthetase long-chain family member 4 (ACSL4) is highly expressed in distal tubules, while the ferroptosis suppressor gene Glutathione Peroxidase 4 (GPX4) is expressed at lower levels. Similarly, in our CS-AKI mouse model kidneys, ferroptosis was activated: ACSL4 was upregulated and GPX4 was downregulated, compared to normal control group (NC group). Notably, ACSL4 expression remained higher and GPX4 expression lowered in distal tubules than in proximal tubules in both NC and CS-AKI groups. Our results demonstrate ferroptosis activation in distal tubules both in vivo and in vitro, and suggest that this activation is linked to inhibition of the GTP cyclohydrolase 1 (GCH1) pathway. We further evaluated a therapeutic strategy using rosmarinic acid (RA) to regulate the GCH1/tetrahydrobiopterin (BH4) axis and inhibit ferroptosis in the distal tubules of CS-AKI mice. Following RA treatment, the expression of ACSL4 in distal tubules was significantly downregulated, while both GCH1 and BH4 levels were significantly upregulated. In addition, the distal tubular injury marker urinary neutrophil gelatinase-associated lipocalin (uNGAL) was markedly reduced. These findings provide new insights into the treatment of CS-AKI by targeting ferroptosis in both distal and proximal tubules.