CsA, FK506, corticosteroids and rapamycin inhibit TNFα production by cultured PTEC

Abstract

In ths study we investigated the effect of immunosuppressive drugs on the interleukin-1 alpha (IL-lα) enhanced tumor necrosis factor alpha (TNFα) production by proximal tubular epithelial cells (PTEC). Under basal conditions cultured PTEC produce between 0 to 390 pg/ml/105 cells of TNFα. Upon stimulation with IL-1α an enhancement of TNFα production was seen in each cell line tested, ranging from 230 to 2424 pg/ml/105 cells. The presence of cyclosporin A (CsA) during stimulation with IL-1α inhibited the enhanced TNFα production 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, corticosteroids and rapamycin also inhibited TNFα production in a dose dependent fashion, although not as effectively as CsA. Two corticosteroids were tested for their inhibitory effect on TNFα production. It was found that dexamethasone at a concentration of 10 ng/ml inhibited TNFα production for almost 40%. A 100-fold higher concentration of hydrocortisone was necessary to yield similar inhibition. The effect of rapamycin on the IL-1α enhanced TNFα production differed from the effect of CsA. While CsA induced a maximal inhibition of 90%, rapamycin only induced a maximal inhibition of 37%, and even less inhibition at higher concentrations of the drug. The presence of the various drugs was essential for their inhibitory effect, because removal of the drug 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 concentrations of rapamycin and FK506 were used. Low concentrations of rapamycin with high concentrations of FK506 were synergistic. Since TNFα is likely to be an important mediator in renal allograft rejection, these data suggest that the beneficial effect of immunosuppressive drugs after renal transplantation may partly be due to the effect on TNFα production by renal parenchymal cells.