Low-dose lipopolysaccharide inducing continuous and obvious increase in urinary protein in hyperglycemic rats and the underlying mechanism

Abstract

Proteinuria is an important hallmark of diabetic nephropathy models, however it takes a long time for the proteinuria and is not stable. Therefore, low-dose lipopolysaccharide (LPS) was investigated in this work to induce rapid and stable proteinuria in hyperglycemic rats and the underlying mechanism was studied. Hyperglycemia rats was induced by high-fat feeding combined with intraperitoneal injection of streptozotocin (STZ). After 21 days, the model rats received a subinjury dose of 0.8 mg / kg LPS intraperitoneally (i.p.). We detected related biochemical indexes at different time periods after LPS injection and examined the expression of glomerular podocyte-associated proteins. Simultaneously, we measured expression of inflammatory factors, apoptotic proteins and albumin (ALB) in the renal cortex and renal medulla, respectively. PAS (Periodic Acid Schiff) staining was used to observe renal pathology. After LPS injection, urinary microalbumin (umALB) increased significantly and lasted longer. The expression of Nephrin, Podocin and necroptosis factor kappa B (NF-κB) in rennal cortex and Interleukin 18 (IL-18), Caspase-1, NF-κB and ALB in the renal medulla was significantly changed. Pathologically, the glomerular basement membrane was observed to be significantly thickened, the renal tubules were dilated, and the epithelial cells fell off in a circle. LPS promoted the continuous increase in urinary microalbumin in hyperglycemic rats, which was related to the damage to the glomerular basement membrane and renal tubular epithelial cells and to the inflammatory reaction in the kidney involved in NF-κB signaling, and this pathological damage can help to establish a stable model of diabetic nephropathy with increased proteinuria.