Ursolic Acid Treatment Alleviates Diabetic Kidney Injury By Regulating The ARAP1/AT1R Signaling Pathway

Tian-Kui Ma; Li Xu; Ling-Xu Lu; Xu Cao; Xin Li; Lu-Lu Li; Xu Wang; Qiu-Ling Fan

doi:10.2147/DMSO.S222323

Ursolic Acid Treatment Alleviates Diabetic Kidney Injury By Regulating The ARAP1/AT1R Signaling Pathway

Diabetes Metab Syndr Obes. 2019 Dec 9:12:2597-2608. doi: 10.2147/DMSO.S222323. eCollection 2019.

Authors

Tian-Kui Ma^#¹, Li Xu^#^{1

2}, Ling-Xu Lu^#^{1

3}, Xu Cao¹, Xin Li¹, Lu-Lu Li¹, Xu Wang⁴, Qiu-Ling Fan¹

Affiliations

¹ Department of Nephrology, The First Hospital of China Medical University, Shenyang, Liaoning, People's Republic of China.
² Department of Clinical Laboratories, The First Hospital of China Medical University, Shenyang, Liaoning, People's Republic of China.
³ The First Respiratory Department, General Hospital of Fushun Mining Bureau, Fushun, Liaoning, People's Republic of China.
⁴ Department of Gastroenterology, The First Hospital of China Medical University, Shenyang, Liaoning, People's Republic of China.

^# Contributed equally.

Abstract

Purpose: This study aimed to investigate whether ursolic acid (UA) mitigates renal inflammation, oxidative stress and fibrosis by regulating the angiotensin II type 1 receptor-associated protein (ARAP1)/angiotensin II type 1 receptor (AT1R) signaling pathway and subsequently alleviating renal damage.

Methods: db/db mice were divided randomly into a diabetic nephropathy (DN) group and a UA treatment group. Light microscopy and electron microscopy were used to observe pathological changes in renal tissues. Immunohistochemistry (IHC) was employed to examine changes in the expression of ARAP1, AT1R, 8-hydroxydeoxyguanosine (8-OHdG), NADPH oxidase 2 (NOX2), the extracellular matrix protein fibronectin (FN), IL-1β and IL-18 in renal tissues. Western blotting and RT-qPCR were used to detect the respective changes in the protein and mRNA levels of ARAP1, AT1R, NOX4, NOX2, transforming growth factor-β1 (TGF-β1), FN, collagen IV, IL-1β and IL-18 in renal tissues and mesangial cells. In addition, immunofluorescence staining was employed to examine changes in FN and NOX2 expression in mesangial cells.

Results: UA treatment effectively reduced the body weights and blood glucose levels of db/db mice (p<0.05) as well as the urinary albumin/creatinine ratio (p<0.05). In addition, the renal tissue lesions and glomerulosclerosis index of the db/db mice were significantly improved after treatment (p<0.01). Histochemical analysis results showed significantly lower expression levels of ARAP1, AT1R, FN, NOX2, 8-OHdG, IL-1β and IL-18 in renal tissues in the UA treatment group than in the DN group. Western blotting and RT-qPCR data also revealed UA-induced decreases in the renal levels of the ARAP1, AT1, NOX4, NOX2, TGF-β1, FN, collagen IV, IL-1β and IL-18 proteins in vivo and/or in vitro (p<0.01). ARAP1 knockdown effectively reduced the expression of NOX2 and FN in vitro.

Conclusion: UA alleviated renal damage in type 2 diabetic db/db mice by downregulating proteins in the ARAP1/AT1R signaling pathway to inhibit extracellular matrix accumulation, renal inflammation, fibrosis and oxidative stress.

Keywords: ARAP1; AT1R; diabetic nephropathy; oxidative stress; renal fibrosis; ursolic acid.

Grants and funding

The National Natural Science Foundation of China (81770724; 81800642); The Ministry of Science and Technology of the People’s Republic of China - National Key Research and Development Program “Accurate Medical Research” Project 3. Clinical Cohort and Prognosis of Lupus Nephritis; The Natural Science Foundation of Liaoning Province (201602821); The Science and Technology Plan Project of Shenyang (F16⁃205⁃1⁃40); The Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program (RC170172).