Corticosteroids worsen proteinuria and increase intraglomerular signaling by NF-ĸB in a model of membranous glomerulonephritis.

BACKGROUND/AIMS: Passive Heymann nephritis (PHN) is a model of human membranous glomerulonephritis characterized by heavy proteinuria. We have recently demonstrated activation of NF-κB by podocytes in this model. In this study, therefore, we have determined whether dexamethasone (DEX) and pyrrolidine dithiocarbamate (PDTC), therapies that inhibit NF-κB, influence proteinuria. METHODS: Twenty-one days after induction of PHN, rats were divided into three groups: group 1 received saline, group 2 received DEX for 7 days, and group 3 received PDTC for 7 days. The effects of these drugs on activation of NF-κB and proteinuria were then determined. RESULTS: DEX administration was associated with a very significant increase in proteinuria, whereas PDTC produced a slight decrease. Within the glomerulus, both agents were associated with increased levels of IL-1ß mRNA and protein, compared with untreated rats, and there was increased nuclear localization of p50 in both of the treated groups. Neither agent, therefore, inhibited NF-κB activation within the glomerulus. Both agents produced a decrease in the systemic anti-sheep Ig immune response, and there was reduced interstitial αß T-cell infiltration compared with controls. CONCLUSION: These data suggest that agents predicted to inhibit NF-κB might have opposing effects in membranous glomerulonephritis. The use of steroids to treat membranous glomerulonephritis, therefore, might produce unpredictable results, depending on whether suppression of the systemic immune response or inflammatory events within the kidney is more important in a particular patient.

5-aminoimidazole-4-carboxamide ribonucleoside and AMP-activated protein kinase inhibit signalling through NF-κB.

Activation of nuclear factor-kappa B (NF-κB) is one of the most important pro-inflammatory mechanisms in disease. In this study, we show that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), an intermediate in nucleoside metabolism, inhibits signalling by NF-κB in three cell types, including bovine aortic endothelial cells (BAEC). The block in the NF-κB signalling pathway occurred beyond degradation of IκB-α and movement of p65 into the nucleus of BAEC. There was, however, reduced binding of NF-κB from AICAR-treated cells to a κB-consensus oligonucleotide, suggesting that part of the mechanism was a reduction in NF-κB DNA-binding activity. Although AICAR is metabolized to ZMP and then adenosine, adenosine had no effect on activation of an NF-κB reporter. ZMP, however, activates the metabolic stress-sensing AMP-activated protein kinase (AMPK). Transfection of active AMPK into BAEC reduced NF-κB reporter activity compared with a kinase-dead mutant, suggesting that part of the ability of AICAR to inhibit NF-κB signalling is due to activation of AMPK. Inhibition of NF-κB signalling may be important in the anti-inflammatory action of drugs such as sulfasalazine and methotrexate, which led to the accumulation of AICAR within target cells.