Journal: Frontiers in Cell and Developmental Biology

Article Title: CaSR regulates SLC26A6 expression via the PKA-FOXO4 signaling axis to promote experimental calcium oxalate kidney stone formation in rats

doi: 10.3389/fcell.2026.1746423

Figure Lengend Snippet: Calcium oxalate crystals upregulate CaSR and SLC26A6 expression in vivo and in vitro . (A) Representative images of renal tissue pathological sections from each group of rats (HE staining, Pizzolato’s staining, and polarized light microscopy). (B) Western blotting detection of CaSR and SLC26A6 protein expression levels in NRK-52E cells after COM crystal intervention. (C,D) RT-qPCR (C) and Western blotting (D) detection of CaSR and SLC26A6 mRNA and protein expression levels in renal tissues of each group of rats. (E) Immunohistochemical analysis revealed the tubular localization patterns of CaSR and SLC26A6 in rat kidney tissue. Low-power field images demonstrated their widespread distribution within both the renal cortex and medulla. Precise cellular colocalization could only be assessed through high-power confocal analysis combined with segment-specific markers, representing a limitation of this study. Data are presented as mean ± standard deviation, *p < 0.05, **p < 0.01 vs. NC group or Control group.

Article Snippet: Rabbit polyclonal antibodies against CaSR (73303S) and Phospho-PKA Substrate (9624S) were purchased from Cell Signaling Technology Company.

Techniques: Expressing, In Vivo, In Vitro, Staining, Light Microscopy, Western Blot, Quantitative RT-PCR, Immunohistochemical staining, Standard Deviation, Control

Journal: Frontiers in Cell and Developmental Biology

Article Title: CaSR regulates SLC26A6 expression via the PKA-FOXO4 signaling axis to promote experimental calcium oxalate kidney stone formation in rats

doi: 10.3389/fcell.2026.1746423

Figure Lengend Snippet: CaSR regulates SLC26A6 expression via the transcription factor FOXO4. (A) Western blotting detection of p-FOXO4 (Thr451) and SLC26A6 protein expression levels in NRK-52E cells treated with CaSR agonist (R568, 30 μM) or inhibitor (NPS-2143, 10 μM) in the presence of COM crystals. (B) Western blotting detection of SLC26A6 protein expression levels in NRK-52E cells treated with FOXO4 agonist (TNF-α, 20 ng/mL) or inhibitor (JY-2, 30 μM) in the presence of COM crystals. (C) Dual-luciferase reporter gene assay detecting the effect of FOXO4 on SLC26A6 promoter activity. Data are presented as mean ± standard deviation, *p < 0.05, **p < 0.01 vs. COM group; #p < 0.05, ##p < 0.01 vs. specified group.

Article Snippet: Rabbit polyclonal antibodies against CaSR (73303S) and Phospho-PKA Substrate (9624S) were purchased from Cell Signaling Technology Company.

Techniques: Expressing, Western Blot, Luciferase, Reporter Gene Assay, Activity Assay, Standard Deviation

Journal: Frontiers in Cell and Developmental Biology

Article Title: CaSR regulates SLC26A6 expression via the PKA-FOXO4 signaling axis to promote experimental calcium oxalate kidney stone formation in rats

doi: 10.3389/fcell.2026.1746423

Figure Lengend Snippet: CaSR promotes FOXO4 phosphorylation via the PKA signaling pathway. (A) Western blotting detection of p-PKA substrate and p-FOXO4 (Thr451) protein expression levels in NRK-52E cells treated with CaSR agonist (R568, 30 μM) or inhibitor (NPS-2143, 10 μM) in the presence of COM crystals. (B) Western blotting detection of p-FOXO4 (Thr451) and SLC26A6 protein expression levels in NRK-52E cells treated with PKA agonist (8-Bromo-cAMP, 30 μM) or inhibitor (H-89 2HCl, 30 μM) in the presence of COM crystals. Data are presented as mean ± standard deviation, *p < 0.05, **p < 0.01 vs. COM group; #p < 0.05, ##p < 0.01 vs. specified group.

Article Snippet: Rabbit polyclonal antibodies against CaSR (73303S) and Phospho-PKA Substrate (9624S) were purchased from Cell Signaling Technology Company.

Techniques: Phospho-proteomics, Western Blot, Expressing, Standard Deviation

Journal: Frontiers in Cell and Developmental Biology

Article Title: CaSR regulates SLC26A6 expression via the PKA-FOXO4 signaling axis to promote experimental calcium oxalate kidney stone formation in rats

doi: 10.3389/fcell.2026.1746423

Figure Lengend Snippet: Crystal deposition and tissue damage in the kidneys of rats from each group (A) Hematoxylin and eosin (HE) staining, polarized light microscopy, and Pizzolato’s calcium salt staining of kidney tissue from rats in the EG, CaSR-a, and CaSR-i groups. HE staining reveals tubular architecture and the extent of damage; polarized light microscopy reveals the birefringence of calcium oxalate crystals; Pizzolato’s staining stains calcium oxalate crystals black. (B) Hematoxylin and eosin (HE) staining, polarized light microscopy, and Pizzolato’s calcium salt staining of renal tissues from rats in the EG, PKA-i, and FOXO4-i groups. HE staining reveals the extent of tubular damage in each group; polarized light microscopy and calcium salt staining jointly confirm differences in crystal deposition among the groups.

Article Snippet: Rabbit polyclonal antibodies against CaSR (73303S) and Phospho-PKA Substrate (9624S) were purchased from Cell Signaling Technology Company.

Techniques: Staining, Light Microscopy

Journal: Frontiers in Cell and Developmental Biology

Article Title: CaSR regulates SLC26A6 expression via the PKA-FOXO4 signaling axis to promote experimental calcium oxalate kidney stone formation in rats

doi: 10.3389/fcell.2026.1746423

Figure Lengend Snippet: Effects of intervening in the CaSR-PKA-FOXO4 signaling axis on urinary biochemical indicators and renal protein expression in rats. (A) Western blotting detection of p-PKA substrate, p-FOXO4 (Thr451), and SLC26A6 protein expression levels in renal tissues of each group of rats. (B) Concentrations of calcium ions and oxalate in 24-h urine of each group of rats. (C) Quantitative analysis of SLC26A6 protein expression from (A) . Data are presented as mean ± standard deviation, *p < 0.05, **p < 0.01 vs. E.G., group.

Article Snippet: Rabbit polyclonal antibodies against CaSR (73303S) and Phospho-PKA Substrate (9624S) were purchased from Cell Signaling Technology Company.

Techniques: Expressing, Western Blot, Standard Deviation

Journal: Frontiers in Cell and Developmental Biology

Article Title: CaSR regulates SLC26A6 expression via the PKA-FOXO4 signaling axis to promote experimental calcium oxalate kidney stone formation in rats

doi: 10.3389/fcell.2026.1746423

Figure Lengend Snippet: Schematic diagram of the mechanism by which CaSR synergistically promotes calcium oxalate stone formation through dual signaling pathways. Under stimulation by calcium oxalate crystals (COM), the calcium-sensing receptor (CaSR) on the membrane of renal tubular epithelial cells is activated. The activated CaSR activates protein kinase A (PKA) via G proteins. PKA then functions through two parallel pathways: Phosphorylates Signal Transducer and Activator of Transcription 3 (STAT3), causing its nuclear translocation and upregulation of the tight junction protein Claudin-14 expression. Claudin-14 inhibits paracellular calcium reabsorption, leading to hypercalciuria; Phosphorylates Forkhead box protein O4 (FOXO4), causing its nuclear translocation and binding to the SLC26A6 gene promoter, upregulating its expression and promoting oxalate secretion into the lumen, leading to hyperoxaluria. The increased excretion of urinary calcium and oxalate collectively exacerbates the supersaturation of calcium oxalate in urine, ultimately promoting kidney stone formation.

Article Snippet: Rabbit polyclonal antibodies against CaSR (73303S) and Phospho-PKA Substrate (9624S) were purchased from Cell Signaling Technology Company.

Techniques: Protein-Protein interactions, Membrane, Translocation Assay, Expressing, Binding Assay