DKK3 promotes oxidative stress injury and fibrosis in HK-2 cells by activating NOX4 via β-catenin/TCF4 signaling

Wnt/β-catenin Pathway Aggravates Renal Fibrosis by Activating PUM2 Transcription to Repress YME1L-mediated Mitochondrial Homeostasis

Chronic kidney disease (CKD) affects more than 10% of people worldwide and is a leading cause of death. However, the pathogenesis of CKD remains elusive. The oxidative stress and mitochondrial membrane potential were detected using Enzyme-linked immunosorbent assay and JC-1 assay. Co-immunoprecipitation, dual-luciferase assay, chromatin IP, RNA IP and RNA pull-down were used to validate the interactions among genes. Exploiting a H2O2-induced fibrosis model in vitro, PUM2 expression was upregulated in Human kidney 2 cell (HK-2) cells, along with reduced cell viability, enhanced oxidative stress, impaired mitochondrial potential, and upregulated expressions of fibrosis-associated proteins. While PUM2 knockdown reversed the H2O2-induced injury in HK-2 cells. Mechanically, Wnt/β-catenin pathway activated PUM2 transcription via TCF4. It was further identified that Wnt/β-catenin pathway inhibited YME1L expression through PUM2-mediated destabilizing of its mRNA. PUM2 aggravated H2O2-induced oxidative stress, mitochondrial dysfunction, and renal fibrosis in HK-2 cell via suppressing YME1L expression. Our study revealed that Wnt/β-catenin aggravated renal fibrosis by activating PUM2 transcription to repress YME1L-mediated mitochondrial homeostasis, providing novel insights and potential therapeutic targets for the treatment of kidney fibrosis.

NRF1-induced mmu_circ_0001388/hsa_circ_0029470 confers ferroptosis resistance in ischemic acute kidney injury via the miR-193b-3p/TCF4/GPX4 axis

AIMS

Circular RNAs (circRNAs) are critical in the progression of ischemic acute kidney injury (AKI). Nevertheless, the specific functions and regulatory pathways of mmu_circ_0001388 and hsa_circ_0029470 remain elusive.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) was utilized to assess the expression patterns of mmu_circ_0001388, hsa_circ_0029470, and miR-139b-3p. Protein expressions of nuclear respiratory factor 1 (NRF1), transcription factor 4 (TCF4), glutathione peroxidase 4 (GPX4), and Acyl-CoA synthetase long-chain family member 4 (ACSL4) were identified via immunoblotting. Furthermore, the functions and control mechanisms of mmu_circ_003062 and hsa_circ_0075663 were examined via diverse cell and animal studies, encompassing bioinformatics prediction, dual-luciferase reporter (DLR), chromatin immunoprecipitation (ChIP), fluorescence in situ hybridization (FISH), flow cytometry (FCM), hematoxylin and eosin (H&E) staining, dihydroethidium (DHE), TUNEL, immunohistochemistry, and transmission electron microscopy (TEM), and Fe2+ assay.

KEY FINDINGS

Initially, the induction of mmu_circ_0001388 by NRF1 was observed in vitro and in vivo following ischemia/reperfusion (I/R) injury. Subsequently, knockdown or overexpression of mmu_circ_0001388 was found to either promote or inhibit ferroptosis caused by I/R in Boston University mouse proximal tubule (BUMPT) cells, respectively. From a mechanistic standpoint, mmu_circ_0001388 was found to function as a sponge for miR-193b-3p, which promoted TCF4 and subsequently enhanced GPX4, thereby suppressing ferroptosis. Finally, the overexpression of mmu_circ_0001388 was shown to ameliorate I/R-induced AKI in mice. In parallel, hsa_circ_0029470, homologous to mmu_circ_0001388, demonstrated an identical control pathway in human renal tubular epithelial (HK-2) cells.

SIGNIFICANCE

The NRF1/mmu_circ_0001388, hsa_circ_0029470/miR-193b-3p/TCF4/GPX4 axis is pivotal in regulating ferroptosis induced by ischemic AKI and holds potential as a therapeutic target.