Antioxidants Inhibit Interleukin-1-induced Cyclooxygenase and Nitric-oxide Synthase Expression in Rat Mesangial Cells

Abstract

Glomerular mesangial cells produce reactive oxygen intermediates when stimulated by interleukin-1 (IL-1) or tumor necrosis factor. Recent observations suggest that reactive oxygen intermediates may play a role in IL-1 and tumor necrosis factor signaling and may upregulate gene expression. We therefore evaluated the effects of antioxidants on IL-1␤-induced cyclooxygenase-2 (Cox-2) and inducible nitric-oxide synthase (iNOS) expression in rat mesangial cells. The oxidant scavenger, pyrrolidine dithiocarbamate (PDTC), inhibited iNOS expression at the transcriptional level, since PDTC abolished iNOS mRNA accumulation. In contrast, PDTC inhibited Cox-2 expression at the post-transcriptional level, since PDTC did not affect IL-1␤-induced Cox-2 mRNA levels but inhibited Cox-2 protein expression and prostaglandin E 2 production. Another antioxidant, rotenone, which inhibits reactive oxygen intermediate production by inhibiting the mitochondrial electron transport system, did not inhibit IL-1␤-induced iNOS and Cox-2 mRNA expression but inhibited iNOS and Cox-2 protein expression, suggesting a post-transcriptional target for the inhibition of iNOS and Cox-2 expression induced by IL-1␤. These results suggest that not only transcriptional regulation but also post-transcriptional mechanisms are involved in redox-sensitive inhibition of cytokine induced Cox-2 and iNOS expression. These results suggest a novel approach for intervention in cytokine-mediated inflammatory processes. Interleukin-1 (IL-1)1 is a cytokine which mediates a variety of processes in host defense, such as inflammation and the cellular response to injury (1). During glomerular inflammation, cytokines from infiltrating macrophages and activated mesangial cells may act to sustain and promote glomerular damage. We have previously demonstrated that IL-1␤ induces cyclooxygenase-2 (Cox-2) and the inducible nitric-oxide synthase (iNOS) with increases in proinflammatory mediators, PGE 2 (2) and NO (3), in rat mesangial cells. The molecular signaling mechanisms by which IL-1␤ induces Cox-2 and iNOS includes transcriptional activation of these genes to produce increased levels of mRNA species which are "unstable." This mRNA is then translated into protein and degraded. These intracellular events are therefore potentially subject to regulation at the transcriptional or post-transcriptional level. Furthermore, the factors which control message stability and translational efficiency are not well understood.Mesangial cells produce reactive oxygen intermediates (ROI) with stimulation by endotoxin and cytokines, including IL-1 and tumor necrosis factor (4). ROI are produced during various electron-transfer reactions. When generated in excess, ROI can damage cells by peroxidizing lipids and disrupting proteins and nucleic acids. However, ROI may exert signaling functions and regulate gene expression at moderate concentrations (5-10). During glomerular inflammation, ROI from activated mesangial cells may act as signaling molecules. We have therefore evaluated the mechanisms ...

10t,12c-conjugated linoleic acid inhibits lipopolysaccharide-induced cyclooxygenase expression in vitro and in vivo

“…Several pharmacological agents have been shown to participate in the posttranscriptional regulation of COX-2 mRNA, such as dexamethasone (41) and leptomycin B (42). Pyrrolidine dithiocarbamate, an oxidant scavenger, and rotenone, an inhibitor of the mitochondrial electron transport system, have also been reported to inhibit the expression of COX-2 protein expression without affecting COX-2 mRNA level in primary mesangial cell cultures (43). The differential inhibition rate on COX-2 mRNA and protein expression by 10t,12c-CLA may be attributed to the posttranscriptional regulation of the gene product.…”

Hormetic Dietary Phytochemicals

“…FA is a phenolic compound with three distinctive structural motifs that can possibly contribute to its free radical scavenging capability (Srinivasan et al, 2007). It has been reported that FA decreases the levels of inflammatory mediators (prostaglandin E2 and TNF-α; Ou et al, 2003), and nitric oxide synthase (iNOS) expression and function (Tetsuka et al, 1996). In addition, hydrophobic ester derivatives of FA seem to have enhanced inhibitory activity on iNOS protein expression in LPS/interferon-γ (IFN-γ) activated RAW264.7 cells (Murakami et al, 2002).…”

p38 Mitogen-activated Protein Kinase Down-regulates Nitric Oxide and Up-regulates Prostaglandin E2 Biosynthesis Stimulated by Interleukin-1β

“…In primary cultures of mesangial cells, we demonstrated previously that IL-1␤ induced iNOS and Cox-2 expression, which in turn, increased NO and PGE 2 production. However, the signaling pathways by which IL-1 induces NO and PG biosyntheses are not well understood (2,28,32). Recently, much effort has been directed at defining the signal transduction pathways utilized by IL-1.…”