Hyperglycemia-induced NETs Promotes Renal Fibrosis

ObjectiveDiabetic nephropathy is characterized by fibrosis.Studies have shown that neutrophil extracellular traps(NETs),which composed of decondensed chromatin and antimicrobials,could be released from neutrophils after hyperglycemia stimulation.Whether NETs promotes diabetic renal fibrosis were further examined here.MethodsSTZ-induced diabetic mice and their vehicle-treated controls were used 16 weeks after successful induction.Levels of serum creatinine and urinary albumin to creatinine ratio(UACR)in diabetic mice were significantly increased compared to controls.Renal tissues from donors of normoglycemic subjects,patients with diabetes and diabetic kidney disease(DKD)were collected.Periodic Acid-Schiff stain(PAS)and Sirius-Red stain further confirmed renal fibrosis in diabetic mice or patients with DKD.ResultsIn diabetic mice,NETs-related markers MPO and Cit-histone3 immunostaining inside renal tubules were associated with increased ?-SMA and decreased E-Cadherin,which were markers of renal fibrosis.In patients with diabetic kidney disease,fibrosis of renal tubules was also accompanied by NETs formation.In control mice or normoglycemic subjects,little renal fibrosis or NETs formation was seen in kidney tissues.To further explore whether NETs induced by hyperglycemia promotes fibrosis of HK-2(human proximal tubule epithelial)cells,neutrophils isolated from peripheral blood of health donors were treated with normal glucose(NG,5 mmol/L),high glucose(HG,25 mmol/L),phorbol 12-myristate 13-acetate(PMA,25 nmol/L),respectively.Sytox Green and dsDNA quantitation showed NETs could be induced by HG through autophagy.After exposure to NETs(100ng/mL,24h)related by hyperglycemia,a decreased level of E-Cadherin(epithelial cell marker),and increased levels of Snail and ZEB,was determined by Western Blot In HK-2 cells.These results indicated that HK-2 cells underwent a partial epithelial-mesenchymal transition(EMT)after exposure from hyperglycemia related NETs.ConclusionNETs induced by hyperglycemia might promote diabetic kidney fibrosis.