[Study on the promotion of podocyte pyroptosis by high glucose-stimulated GMC-derived exosomes and the intervention effects of Tongluo Yishen Formula].

Abstract

Objective To investigate the effects of exosomes (Exo) derived from high glucose-stimulated glomerular mesangial cells (GMC) on the kidneys of C57BL/6 mice and the intervention mechanism of Tongluo Yishen Formula (TLYSF). Methods The rat GMC were divided into a normal glucose group (NG, with 5.6 mmol/L glucose) and a high glucose group (HG, with 30 mmol/L glucose). After 24 hours of culture, the supernatant was collected, and exosomes were extracted using the ultracentrifugation method. The exosomes were then identified by transmission electron microscopy and Western blot analysis. Male C57BL/6 mice were divided into three groups: NO-Exo group, NG-Exo group, and HG-Exo group. These groups were respectively administered tail vein injections of PBS buffer, exosomes derived from GMC cultured in normal glucose, and exosomes derived from GMC cultured in high glucose, three times a week for a total of 8 weeks. After 8 weeks, the mice in the HG-Exo group were randomly divided into three subgroups: the HG-Exo group [gavaged with saline], the HG-Exo+TLYSF group [gavaged with TLYSF at 34.32 g/(kg.d)], and the HG-Exo + VAL group [gavaged with valsartan suspension at 10.4 mg/(kg.d)], and the intervention lasted for 4 weeks. Urinary microalbumin (mALb), urinary N-acetyl-β-D-aminoglucosidase (NAG), glycated hemoglobin (HbA1c), serum creatinine (Scr) and urea nitrogen (BUN) were detected. Transmission electron microscopy was used to observe the ultrastructure of renal tissues. TUNEL was used to detect the DNA damage of renal tissue cells. Immunofluorescence was used to detect the expression of NOD-like receptor family pyrin domain containing 3 (NLRP3) and wilms tumor 1(WT-1). RT-PCR was used to detect the mRNA levels of NLRP3, cysteinyl aspartate-specific proteinase 1 (caspase-1), interleukin-1 beta (IL-1β), miR-200c-3p and miR-148a-3p. Western Blot was employed to detect the protein expression of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1 and IL-1β. Results Compared with the NG-Exo group, mice in the HG-Exo group exhibited significantly increased levels of mALb, urinary NAG, Scr and BUN. Transmission electron microscopy revealed ruptured podocyte membranes and swollen mitochondria. The positive rate of cells stained by the TUNEL increased, with elevated optical density of NLRP3 and decreased optical density of WT-1. Additionally, there was a significant increase in the level of NLRP3, caspase-1, IL-1β mRNA, as well as miR-200c-3p and miR-148a-3p. The protein expression of NLRP3, ASC, caspase-1, and IL-1β also increased. Compared with HG-Exo group, mice in the HG-Exo+TLYSF group showed decreased levels of mALb, urinary NAG, Scr, and BUN. The podocyte membranes were relatively intact, and mitochondrial damage was alleviated. The positive rate of cells stained by the TUNEL decreased, along with a reduction in the optical density of NLRP3 and an increase in the optical density of WT-1. Furthermore, the mRNA expression levels of NLRP3, caspase-1, IL-1β, miR-200c-3p, and miR-148a-3p were all downregulated to varying degrees. The protein expression levels of NLRP3, ASC, caspase-1, and IL-1β also decreased. Conclusion Exosomes derived from GMC stimulated by high glucose can damage the kidneys of mice and induce podocyte pyroptosis. TLYSF may ameliorate podocyte pyroptosis by downregulating the expression of exosomal miR-200c-3p and miR-148a-3p and inhibiting the activation of the NLRP3/ASC/caspase-1 pathway.