The Effects of Puerarin on Autophagy Through Regulating of the PERK/eIF2α/ATF4 Signaling Pathway Influences Renal Function in Diabetic Nephropathy

Abstract

Background and Purpose

Autophagy is the main protective mechanism against aging in podocytes, which are terminally differentiated cells that have a very limited capacity for mitosis and self-renewal. Here, a streptozotocin-induced DN C57BL/6 mouse model was used to investigate the effects of puerarin on the modulation of autophagy under conditions associated with endoplasmic reticulum stress (ERS). In addition, this study aimed to identify the potential underlying molecular mechanisms.

Methods and Results

DN C57BL/6 mouse model was induced by streptozotocin (150 mg/kg) injection. The mice were administered rapamycin and puerarin, respectively, daily for up to 8 weeks. After the serum and kidney samples were collected, the fasting blood glucose (FBG), parameters of renal function, histomorphology, and the podocyte functional proteins were analyzed. Moreover, the autophagy markers and the expressions of PERK/ATF4 pathway were studied in kidney. Results found that the FBG level in DN mice was significantly higher than in normal mice. Compared with DN model mice, puerarin-treated mice showed an increased expression of podocyte functional proteins, including nephrin, podocin, and podocalyxin. Furthermore, the pathology and structure alterations were improved by treatment with rapamycin and puerarin compared with the DN control. The results indicated an elevated level of autophagy in rapamycin and puerarin groups compared with the DN model, as demonstrated by the upregulated expression of autophagy markers Beclin-1, LC3II, and Atg5, and downregulated p62 expression. In addition, the levels of PERK, eIF2α, and ATF4 were reduced in the DN model, which was partially, but significantly, prevented by rapamycin and puerarin.

Conclusion

This study emphasizes the renal-protective effects of puerarin in DN mice, particularly in the modulation of autophagy under ERS conditions, which may be associated with activation of the PERK/eIF2α/ATF4 signaling pathway. Therefore, PERK may be a potential target for DN treatment.

Keywords:

• diabetic nephropathy
• autophagy
• PERK
• puerarin

Abbreviations

DM, diabetes mellitus; DN, diabetic nephropathy; ECM, extracellular matrix; PERK, protein kinase R-like endoplasmic reticulum kinase; ERS, endoplasmic reticulum stress; PR: puerarin; STZ, streptozotocin; FBG, fasting blood glucose; BUN, blood urea nitrogen; Scr, serum creatinine; Ucr, urine creatinine; HE, hematoxylin-eosin; RT-qPCR, real-time quantitative polymerase chain reaction; UPR, unfolded protein response.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 81960671], and the Guangxi Natural Science Foundation [grant numbers 2018GXNSFBA281096, 2018GXNSFBA281037].