The differential effects of TNF-alpha and IL-1beta on proximal tubular MMP-9 and TIMP-1 expression are mediated through the TNF-RI, the IL-1-RI and the different signaling pathways of PKC, ERK1/2, and p38 MAPK. These findings may provide new insights into the role of proinflammatory cytokines TNF-alpha and IL-1beta in the development and possible therapeutic intervention in tubulointerstitial fibrosis.

Background: Renal cells such as mesangial cells are known to secrete metalloproteinases that are capable of degrading the constituents of the glomerular basement membrane (GBM). Disruption of the GBM via cytokine-induced alterations in matrixmetalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) may be an important mechanism in the renal disease process. In renal disease, both resident renal cells and infiltrating immune cells are capable of secreting pro-inflammatory cytokines including tumour necrosing factor-α (TNFα) and interleukin-1β (IL-1β). In this study, we examine the potential of these cytokines to alter levels of MMPs and TIMPs in human mesangial cells. Methods: The T-HMC human mesangial cell line was cultured in RPMI 1640 containing 5% serum. Cells at confluency were serum starved for 24 h prior to exposure to TNF-α (0.1–100 ng/ml) or IL-1β (0.1–100 ng/ml) or a combination of both for 48 h. Activity of MMP-9 was examined by gelatin zymography and TIMP-1 expression was analysed by Western blotting. Results: TNF-α but not IL-1β resulted in a dose-dependent increase in the latent form of MMP-9 and a decrease in TIMP-1 production. Co-treatment with IL-1β had no effect on the induction of MMP-9 but increased the inhibition of TIMP-1 in the presence of TNF-α. Inhibition of PKC provided evidence of the importance of this pathway in mediating the TNF-α-induced suppression of TIMP-1. Activation of the ERK 1/2 MAPK mediated both the upregulation of MMP-9 and the inhibition of TIMP-1 following TNF-α treatment. p38 MAPK activation was also found to be involved in the TNF-α-stimulated MMP-9. Conclusion: The cytokine TNF-α causes different effects on human mesangial MMP-9 and TIMP-1 expression which are mediated through the TNF-RI, and the different signalling pathways of PKC, ERK 1/2 and p38 MAPK. This suggests an important role for pro-inflammatory cytokines in renal disease progression.

Background: Mesangial cells are known to secrete metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) that are capable of disrupting the glomerular basement membrane (GBM). Disruption of the GBM appears to be an important mechanism in the renal disease process, however little is known about the mechanisms involved. Therefore we examined the potential role of nitric oxide (NO) in the regulation of MMP-9 and TIMP-1 by tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) using the human mesangial cell line (HMCL). Methods: The HMCL was treated with various concentrations of cytokines and NO inhibitors. Activity of MMP-9 was examined by gelatin zymography and TIMP-1 expression was analysed by Western blotting. NO production was measured using the Greiss assay. Results: In this study, stimulation of HMCL cells with TNF-α or IL-1β, alone or in combination, led to a substantial increase in NO production, which was shown to result from an increase in the expression of the inducible form of NOS (iNOS). Treatment of cells with the specific iNOS inhibitor L- potentiated the increase in MMP-9 production induced by TNF-α, but prevented the suppression of TIMP-1 production observed following cytokine treatment. The NO donor, sodium nitroprusside, also stimulated a substantial increase in NO production in HMCL cells, which was associated with a reduction in basal and TNF-α-stimulated MMP-9 and a potentiation of the cytokine-induced decrease in TIMP-1. Conclusions: Our study provides convincing evidence of a modulatory role for NO on cytokine-induced MMP-9 and TIMP-1 production in human mesangial cells.