PDK4-dependent lactate production and lactylation promote renal calcium oxalate crystal-induced EMT and mitochondrial...

Urolithiasis is a highly prevalent urinary system disease imposing a significant global health burden, with calcium oxalate (CaOx) stones constituting the majority of cases. The underlying metabolic and epigenetic mechanisms driving CaOx stone formation remain incompletely understood.

Through integrated single-cell, spatial, and bulk transcriptomic analyses, this study identified PDK4 as a key gene upregulated by CaOx stones in renal proximal tubular epithelial cells (PTECs). In vitro and in vivo models of CaOx stones were established using calcium oxalate monohydrate (COM) treatment and glyoxylic acid (Gly) induction, respectively. Genetic and pharmacological inhibition of PDK4, knockdown of lactate dehydrogenase a (LDHA), and TGF-β inhibitor SB-431542 intervention were employed. Assays for lactate measurement, protein lactylation, epithelial-mesenchymal transition (EMT) markers, mitochondrial function, chromatin immunoprecipitation (ChIP)-qPCR for SMAD3 binding to the GPX4 promoter, and signaling pathway components (TGF-β/SMAD3/GPX4) were performed.

CaOx stones upregulated PDK4 expression in PTECs, leading to glycolytic dysfunction and lactate accumulation. Elevated lactate drove protein lactylation, which subsequently activated the TGF-β/SMAD3 signaling and enhanced SMAD3 binding to the GPX4 promoter to repress GPX4 transcription. This cascade ultimately exacerbated CaOx stone-induced epithelial-mesenchymal transition (EMT) and mitochondrial dysfunction in PTECs. Conversely, pharmacological inhibition of TGF-β signaling alleviated CaOx stone-induced renal injury, EMT, and mitochondrial dysfunction in vivo. Inhibition of PDK4 or reduction of lactate production blocked this axis and attenuated the pathological processes.

These findings delineate a novel PDK4/lactate/lactylation/TGF-β/SMAD3/GPX4 metabolic-epigenetic regulatory axis in CaOx stone-induced renal injury. This pathway provides new mechanistic insights and identifies potential therapeutic targets for nephrolithiasis.