Inhibition of NFkappaB activation with antioxidants is correlated with reduced cytokine transcription in PTC.

We recently reported that inhibition of the transcription factor nuclear factor-kappaB (NFkappaB) with pyrrolidinedithiocarbamate (PDTC) reduced interstitial monocyte infiltration in rats with proteinuric tubulointerstitial disease, whereas N-acetylcysteine (NAC) was not effective. Here we investigate the effects of antioxidants (PDTC, NAC, and quercetin) on NFkappaB activation and cytokine transcription in primary cultured rat proximal tubular epithelial cells (PTC) stimulated with lipopolysaccharide. Antioxidant-mediated inhibition of NFkappaB activation (PDTC, 20-100 microM; NAC, 100 mM; and quercetin, 50 microM) diminished the induction of both pro- [interleukin (IL)-1beta, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, and MIP-2] and anti-inflammatory (IL-10, transforming growth factor-beta1) cytokine transcription in PTC (RT-PCR analysis). PDTC and quercetin did not affect PTC viability, but NAC (100 mM) caused a threefold increase in lactate dehydrogenase leakage (P < 0.001). We conclude that NAC is unable to suppress NFkappaB activation in PTC at subtoxic and physiologically relevant concentrations. Furthermore, antioxidant-mediated inhibition of NFkappaB is correlated with the nonselective reduction of cytokine transcription in activated tubular cells. These data might explain the protective effects of PDTC-mediated NFkappaB inhibition in tubulointerstitial disease in vivo.