Effects of uPA on mesangial matrix changes in the kidney of diabetic rats.

OBJECTIVE

To investigate the effect of urokinase-type plasminogen activator (uPA) on mesangial matrix in the kidney of diabetic rats and its related mechanisms.

METHODS

Diabetic Sprague-Dawley (SD) rats induced by intraperitoneal injection of streptozotocin (STZ) were randomly and evenly divided into two groups: DM + vehicle, and DM + uPA (2500 U kg(-1) uPA via tail vein once a day for four weeks). The normal SD rats without diabetes were considered as control group. Rats in the three groups were executed and the heart blood was sampled for determination of blood glucose and serum creatinine. Meanwhile, kidney tissues of rats were also harvest for measurement of glomerular area, volume, and mesangial area by periodic acid silver methenamine (PASA) staining. The expression of urokinase-type plasminogen activator receptor (uPAR), plasminogen activator inhibitor-1 (PAI-1), and collagen IV in renal tissues was tested with immunohistochemistry.

RESULTS

Compared with control, the DM rats had obvious albuminuria, significantly (p < 0.01) increased glomerular volume and mesangial matrix area, and significantly (p < 0.05) higher expression of uPAR, PAI-1 and collagen IV in mesangial matrix, significantly up-regulated (p < 0.05) glomerular uPAR, PAI-1, and collagen IV expression. After treated with uPA, the diabetic rats had significantly (p < 0.05) reduced albuminuria, significantly (p < 0.01) improved glomerular volume and mesangial matrix, significantly (p < 0.05) down-regulated PAI-1 and collagen IV expression in mesangial matrix. However, the uPAR expression in renal tissues were unchangeable (p > 0.05) and PAI-1 and collagen IV expression were significantly (p < 0.05) reduced when diabetic rats were treated with uPA.

CONCLUSION

uPA can down-regulate glomerular PAI-1 expression in the DM rats but not significantly influence uPAR expression, suggesting that uPA might regulate the mesangial cell (MC) and its matrix expression and improve diseased diabetic mesangial matrix via its combination with uPAR to uptake PAI-1 and accelerate its degradation.