Gut dysbiosis-derived reduction in predicted short-chain fatty acid-producing capacity is associated with oxalate-induced renal oxidative stress involving the Sp3/SOD2 regulatory axis

The gut microbiota and its metabolites, particularly short-chain fatty acids (SCFAs), have been linked to kidney stones, but the specific molecular mechanisms by which they regulate kidney injury remain unclear. This study aimed to investigate these underlying molecular mechanisms. We analyzed gut microbiota diversity in a population, examined the expression of target genes and constructed dynamic expression profiles using a publicly available single-cell RNA sequencing (scRNA-seq) dataset, and investigated the interrelationships among the transcription factors Sp1, Sp3, and SOD2 . Proximal tubular (PT) epithelial cells were treated with a combination of oxalate and SCFAs to assess the effects on cell viability and SOD2 expression. In the stone formers (SF) group, gut microbiota diversity and predicted SCFA-producing capacity were reduced, while predicted oxidative stress responses were enhanced. scRNA-seq revealed that during the transition of PT cells from a healthy to a stone-damaged state, SOD2 , Sp1, Sp3, and SLC16A3 exhibited similar change trajectories. Sp3 expression was significantly positively correlated with SOD2 , and in silico knockdown prediction indicated that Sp3 depletion may induce a significant downregulation of SOD2 expression. Preliminary cell experiments demonstrated that SCFAs may inhibit oxalate-induced damage to renal tubular epithelial cells by regulating SOD2 protein expression. This study suggests that in SF patients, the reduction in predicted SCFA-producing capacity caused by gut dysbiosis is associated with upregulation of SOD2 expression through Sp3-mediated transcriptional activation, a compensatory antioxidant response to oxalate-induced oxidative stress in PT cells. We therefore propose the following working hypothesis: the SCFA–Sp3– SOD2 axis may be involved in the “gut–kidney axis” mechanism underlying kidney stone formation; however, this requires direct measurement of SCFAs, verification of Sp3 binding to the SOD2 promoter, and confirmation in in vivo experiments.