CONTEXT

Elevated uric-acid levels in the blood are closely associated with hypertension, metabolic syndrome, diabetic nephropathy, cardiovascular diseases, and chronic kidney disease (CKD). A high-glucose diet promotes the accumulation of uric acid. Fibrosis commonly occurs in patients with late-stage type 1 or 2 diabetes and can lead to organ dysfunction.

OBJECTIVE

The study intended to investigate whether high uric acid under high glucose conditions can promote the fibrotic progression of diabetic nephropathy by activating the reactive oxygen species (ROS)/ "nod-like receptor (NLR) family pyrin domain containing 3" (NLRP3)/ "Src homology 2 (SH2) domain-containing protein tyrosine phosphatase-2" (SHP2) pathway, which can promote epithelial-mesenchymal transition (EMT) in renal tubular epithelial cells.

DESIGN

The research team conducted an animal study.

SETTING

The study took place at the Affiliated Hospital of Hebei University in Baoding, Hebei Province, China.

ANIMALS

The animals were 14 healthy, male, C57BL/6J mice.

OUTCOME MEASURES

The research team: (1) using Masson's trichrome staining, examined the fibrosis of renal, tubular epithelial cells in the streptozotocin (STZ) modeling and the STZ modeling + uric-acid groups; (2) used Western Blot analysis to detect the protein expression of NLRP3, "nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase 2" (NOX2), NOX4, alpha-smooth muscle actin (α-SMA), fibronectin 1 (FN-1), collagen-I, and mothers against decapentaplegic homolog 2/3 (SMAD2/3); (3) conducted in-vitro experiments by dividing transformed C3H mouse kidney-1 (TCMK-1) cells into different groups: STZ modeling group, STZ modeling + high-glucose group, STZ modeling + high-glucose + advanced glycation end (AGE) product group, STZ modeling+ high-glucose + AGE + uric-acid group, STZ modeling+ high glucose + SHP2 small interfering RNA (SiRNA) group, STZ modeling + high glucose + SHP2 SiRNA + AGE group, and STZ modeling+ high-glucose + SHP2 SiRNA + AGE + uric-acid group for Western Blot experiments; and (4) performed immunofluorescence, CCK-8, and transwell experiments on the seven groups of TCMK-1 cells with different treatments.

RESULTS

The STZ modeling + uric acid group's levels of fibrosis was significantly higher than that of the STZ modeling group (P < .01). Additionally, the STZ modeling + uric acid groups' expression of α-SMA, FN-1, collagen-I, P-SMAD2, P-SMAD3, NLRP3, and reactive oxygen species (ROS), EMT, and SMAD-related proteins were significantly higher than those of the STZ modeling group (P < .01). The protein expression of SHP2, P-SMAD2, α-SMA, and FN-1 for the STZ modeling + high glucose + SHP2 SiRNA, the STZ modeling + high glucose + SHP2 SiRNA + AGE, and the STZ modeling + high glucose + SHP2 SiRNA + AGE + uric acid groups were significantly lower than those of the STZ modeling + high glucose, STZ modeling + high glucose + AGE, and the STZ modeling + high glucose + AGE + uric acid groups, respectively. Immunofluorescence indicated that the STZ modeling+ high glucose + AGE + uric acid group had the highest relative fluorescence intensity, while the three groups treated with SHP2 SiRNA showed the least expression. The cell counting kit-8 (CCK-8) assay showed that STZ modeling group had less cell proliferation, STZ modeling + high sugar group had less cell proliferation than STZ modeling + high sugar +AGE group, STZ modeling + high sugar +AGE+ uric acid group had the highest cell proliferation, STZ modeling + high sugar +SHP2 SiRNA group and STZ modeling + high sugar +SHP2 SiRNA+AGE group and STZ modeling + high sugar +SHP2 SiRNA+AGE+ uric acid group showed the least number of cell proliferation. The results of the transwell cell migration assay were consistent with the CCK-8 assay.

CONCLUSIONS

In a high-glucose environment, high uric acid can promote the fibrotic progression of diabetic nephropathy by activating the ROS/NLRP3/SHP2 pathway, leading to mesenchymal transition between renal tubular epithelial cells.