Downregulation of Salusin-β protects renal tubular epithelial cells against high glucose-induced inflammation, oxidative stress, apoptosis and lipid accumulation via suppressing miR-155-5p

Diabetic nephropathy (DN) is the main contributor to the excess mortality for patients suffering from diabetes. Here, C57BL/6 mice received 4 weeks of high-fat diet and intraperitoneal injection of STZ (100 mg/kg). Mice with random blood glucose level >= 16.7 mmol/L and positive urine protein were recognized as successful DN model. To construct an in vitro model, HK-2 cells were incubated with 30 mM glucose. RT-qPCR and western blot were employed to measure Salusin-beta levels in kidney tissues of DN mice and HG-induced HK-2 cells. Meanwhile, RT-qPCR was performed to detect miR-155-5p level in kidney tissues of DN mice and HG-induced HK-2 cells. TNF-alpha, IL-6, IL-1 beta, ROS, SOD and CAT levels were assessed using commercial assay kits. Furthermore, apoptosis of HK-2 cells was assessed via flow cytometric analysis and TUNEL staining. In addition, intracellular lipid accumulation and total cholesterol levels were detected using Oil red O staining and TC ELISA kit. Herein, Salusin-beta and miR-155-5p levels were distinctly upregulated in kidney tissues of DN mice and HG-induced HK-2 cells. Downregulation of Salusin-beta reduced miR-155-5p expression. Salusin-beta silencing dramatically relieved inflammatory and oxidative injury, suppressed apoptosis as well as lipid accumulation induced by HG in HK-2 cells. Besides, miR-155-5p elevation partially abrogated the alleviating effects Salusin-beta silencing on HG-induced RTEC injury. In summary, downregulation of Salusin-beta protected HK-2 cells against HG-induced inflammation, oxidative stress, apoptosis and ameliorated lipid accumulation through suppressing miR-155-5p, which indicated that Salusin-beta could be a potential therapeutic drug for DN.

Automated summary

The study found that Salusin-beta and miR-155-5p were significantly upregulated in kidney tissues of DN mice and HG-induced HK-2 cells. Downregulation of Salusin-beta reduced miR-155-5p expression. Silencing Salusin-beta significantly alleviated inflammation and oxidative injury induced by HG in HK-2 cells, suppressed apoptosis, and reduced lipid accumulation.