EFFECT OF TGF-BETA-1 AND TNF-ALPHA ON THE PLASMINOGEN SYSTEM OF RAT PROXIMAL TUBULAR EPITHELIAL-CELLS

Rat proximal tubular epithelial cells derived from Wistar-Kyoto and sp ontaneously hypertensive rats were grown to confluency on semipermeabl e tissue culture inserts, and the plasminogen system of these cells wa s analyzed using enzyme assays, Western analysis, zymography, and reve rse transcriptase-polymerase chain reaction. The tubular epithelial ce lls are capable of activating exogenous plasminogen to plasmin by endo genous plasminogen activators. The cells produce tissue-plasminogen ac tivator, urokinase-plasminogen activator, plasminogen activator inhibi tor-1, and urokinase-plasminogen activator receptor. These cells also produce the Heymann nephritis autoantigen, gp330 (megalin), and an ass ociated protein of 45 kd (RAP). Incubation with transforming growth fa ctor-beta 1 resulted in a decrease in plasminogen activation, primaril y because of an increase in plasminogen activator inhibitor-1 RNA and protein and a decrease in u-PA RNA as noted by quantitative reverse tr anscriptase-polymerase chain reaction, Western analysis, and zymograph y. Incubation of these cells with tumor necrosis factor-alpha resulted in an increase in plasminogen activating ability, presumably through an increase in urokinase. Gp330 and the associated 45-kd protein (RAP) RNA were decreased in cells treated with tumor necrosis factor-alpha. The data presented indicates that these transformed proximal tubular epithelial cells may be used to study changes that may occur during He ymann nephritis with respect to the plasminogen system and the autoant igen gp330.