CSA, FK506, CORTICOSTEROIDS AND RAPAMYCIN INHIBIT TNF-ALPHA PRODUCTION BY CULTURED PTEC

In this study we investigated the effect of immunosuppressive drugs on the interleukin-1 alpha (IL-1alpha) enhanced tumor necrosis factor al pha (TNFalpha) production by proximal tubular epithelial cells (PTEC). Under basal conditions cultured PTEC produce between 0 to 390 pg/ml/1 0(5) cells of TNFalpha. Upon stimulation with IL-1alpha an enhancement of TNFalpha production was seen in each cell line tested, ranging fro m 230 to 2424 pg/ml/10(5) cells. The presence of cyclosporin A (CsA) d uring stimulation with IL-1alpha inhibited the enhanced TNFalpha produ ction in a dose dependent fashion, with a maximal inhibition of 90% at a concentration of 250 ng/ml. Inhibition was at the level of mRNA as could be demonstrated by Northern blot analysis. FK506, corticosteroid s and rapamycin also inhibited TNFalpha production in a dose dependent fashion, although not as effectively as CsA. Two corticosteroids were tested for their inhibitory effect on TNFalpha production. It was fou nd that dexamethasone at a concentration of 10 ng/ml inhibited TNFalph a production for almost 40%. A 100-fold higher concentration of hydroc ortisone was necessary to yield similar inhibition. The effect of rapa mycin on the IL-1alpha enhanced TNFalpha production differed from the effect of CsA. While CsA induced a maximal inhibition of 90%, rapamyci n only induced a maximal inhibition of 37%, and even less inhibition a t higher concentrations of the drug. The presence of the various drugs was essential for their inhibitory effect, because removal of the dru g from the PTEC by washing immediately resulted in loss of inhibition. Combinations of CsA and FK506 or rapamycin were not additive. However , combinations of rapamycin and FK506 were antagonistic when low conce ntrations of rapamycin and FK506 were used. Low concentrations of rapa mycin with high concentrations of FK506 were synergistic. Since TNFalp ha is likely to be an important mediator in renal allograft rejection, these data suggest that the beneficial effect of immunosuppressive dr ugs after renal transplantation may partly be due to the effect on TNF alpha production by renal parenchymal cells.