Mechanism of Yishen Jiangtang Decoction in regulating endoplasmic reticulum stress mediated Bcl-2/Caspase-3 to improve diabetic kidney disease

To explore the mechanism of Yishen Jiangtang Decoction (YSJTD) in improving diabetic kidney disease (DKD) based on the apoptotic Bcl-2/Caspase-3 pathway mediated by endoplasmic reticulum stress (ERS).

Thirty 8-week-old SPF male db/db mice were used to establish the DKD model and were randomly divided into model, YSJTD, ERS inhibitor (4-phenylbutyric acid [4-PBA]), and control groups (db/m mice), with 10 mice per group. Mice in the YSJTD and 4-PBA groups were gavaged daily with 5.6 mg/(g·d) YSJTD or 0.5 mg/(g·d) 4-PBA, respectively, whereas the model and control groups received sodium carboxymethyl cellulose. Each mouse was orally administered 0.01 mL/(g·d) for 8 weeks. The mice were administered 0.01 mL/(g·d) YSJTD or 0.5 mg/(g·d) 4-PBA via gavage for 8 weeks. The general condition of the mice was observed, and blood glucose and plasma lipid levels were measured. Oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were performed, and the area under the curve (AUC) was calculated. Renal pathological changes (assessed using hematoxylin and eosin, periodic acid-Schiff, and Masson staining) and cell apoptosis, evaluated via TUNEL staining, were examined. Protein expression levels of Caspase-3 and Bcl-2 in kidney tissues were analyzed using Western blotting. A DKD model was established using high-glucose-induced mouse glomerular mesangial cells, SV40 MES 13. The Cell Counting Kit-8 assay was used to screen for high glucose concentrations and to determine the concentration of the YSJTD drug-containing serum. Cells were divided into four groups: control, model (30 mmol/L high glucose), 10% YSJTD drug-containing serum (30 mmol/L high glucose + 10% drug-containing serum), and 1 mol/L 4-PBA (30 mmol/L high glucose + 1 mmol/L 4-PBA). Western blotting was used to detect the protein levels of GRP78, Caspase-3, and Bcl-2 in the cells.

Compared to the control group, the model, YSJTD, and 4-PBA groups exhibited significantly increased OGTT-AUC, ITT-AUC, triglyceride (TG), and cholesterol (CHOL) levels (P < 0.05). These groups also showed severe renal pathological damage, increased glycogen deposition, and exacerbated fibrosis in kidney tissues. Compared to the model group, both the YSJTD and 4-PBA groups showed significantly reduced OGTT-AUC, TG, and CHOL levels, alleviated renal pathological damage, and decreased glycogen deposition and fibrosis. The YSJTD group also exhibited significantly reduced ITT-AUC (P < 0.05). Compared to the control group, the model group exhibited an increased number of apoptotic cells in renal tissue, reduced Bcl-2 expression, and elevated Caspase-3 expression (P < 0.05). Compared to the model group, both the YSJTD and 4-PBA groups demonstrated a reduced number of apoptotic cells, decreased Caspase-3 expression, and increased Bcl-2 expression, with the YSJTD group showing a more pronounced decrease in apoptotic cells (P < 0.05). In vitro experiments revealed that, compared to the control group, the model group exhibited increased GRP78 and Caspase-3 expression, as well as decreased Bcl-2 expression (P < 0.05). Compared to the model group, the 10% YSJTD drug-containing serum and 1 mol/L 4-PBA groups showed reduced GRP78 and Caspase-3 expression, as well as upregulated Bcl-2 expression (P < 0.05).

YSJTD improves glucose and lipid metabolism disorders in DKD by inhibiting the ERS-induced apoptotic pathway mediated by Bcl-2/Caspase-3, thereby exerting protective effects on renal function.