Involvement of the NF-kappa B signaling pathway in the renoprotective effects of isorhamnetin in a type 2 diabetic rat model

The aim of the present study was to investigate the renoprotective effects of isorhamnetin (ISO) in type 2 diabetic rats and its effects on the nuclear factor-kB (NF-kB) signaling pathway, which is associated with diabetic nephropathy. The type 2 diabetic rat model was established by a high-fat diet plus streptozocin injection and the rats were subsequently treated with two dosages of ISO, respectively. The levels of blood glucose were determined. Urinary osteopontin, kidney injury molecule-1 (KIM-1) and albumin were measured to evaluate the renal function of the rats. Renal NF-kappa B signaling activity was assessed by measuring the levels of NF-kappa B p65, phospho-NF-kappa B p65, inhibitor of NF-kappa B (I kappa B alpha) and phospho-I kappa B alpha, and the NF-kappa B p65 DNA-binding activity. Downstream inflammatory mediators [tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6, intercellular adhesion molecule-1 (ICAM-1) and transforming growth factor-beta 1 (TGF-beta 1)] of the NF-kappa B signaling pathway were investigated to evaluate the renal inflammatory response. Renal levels of malondialdehyde and total superoxide dismutase were detected to access the oxidative stress. Furthermore, glomerular mesangial cells (GMCs) were treated with lipopolysaccharide and ISO. In the cellular experiment, the NF-kappa B signaling activity, levels of TNF-alpha, IL-1 beta, IL-6, ICAM-1 and TGF-beta 1, and oxidative stress were also investigated. The results showed that ISO decreased the levels of urinary osteopontin, KIM-1 and albumin. ISO also inhibited the NF-kappa B signaling activity, decreased the production of inflammatory mediators and attenuated oxidative stress in diabetic rats and GMCs. The present investigations revealed that ISO had ameliorative effects on diabetes-induced renal damage and the activity may be associated with the negative regulation of NF-kappa B signaling pathway.