Inhibition of Cytokine-induced Matrix Metalloproteinase 9 Expression by Peroxisome Proliferator-activated Receptor α Agonists Is Indirect and Due to a NO-mediated Reduction of mRNA Stability

Abstract

Rat renal mesangial cells express high levels of matrix metalloproteinase 9 (MMP-9) in response to inflammatory cytokines such as interleukin 1␤ (IL-1␤). We tested whether ligands of the peroxisome proliferator-activated receptor (PPAR␣) could influence the cytokineinduced expression of MMP-9. Different PPAR␣ agonists dose-dependently inhibited the IL-1␤-triggered increase in gelatinolytic activity mainly by decreasing the MMP-9 steady-state mRNA levels. PPAR␣ agonists on their own had no effects on MMP-9 mRNA levels and gelatinolytic activity. Surprisingly, the reduction of MMP-9 mRNA levels by PPAR␣ activators contrasted with an amplification of cytokine-mediated MMP-9 gene promoter activity and mRNA expression. The potentiation of MMP-9 promoter activity functionally depends on an upstream peroxisome proliferator-responsive element-like binding site, which displayed an increased DNA binding of a PPAR␣ immunopositive complex. In contrast, the IL-1␤-induced DNA-binding of nuclear factor B was significantly impaired by PPAR␣ agonists. Most interestingly, in the presence of an inducible nitric-oxide synthase (iNOS) inhibitor, the PPAR␣-mediated suppression switched to a strong amplification of IL-1␤-triggered MMP-9 mRNA expression. Concomitantly, activators of PPAR␣ potentiated the cytokineinduced iNOS expression. Using actinomycin D, we found that NO, but not PPAR␣ activators, strongly reduced the stability of MMP-9 mRNA. In contrast, the stability of MMP-9 protein was not affected by PPAR␣ activators. In summary, our data suggest that the inhibitory effects of PPAR␣ agonists on cytokine-induced MMP-9 expression are indirect and primarily due to a superinduction of iNOS with high levels of NO reducing the half-life of MMP-9 mRNA.Dysregulation of extracellular matrix turnover is an important feature of glomerular inflammatory processes and may result in the loss of the mechanical and functional integrity of the glomerulus (1-3). Physiologically, the balance between synthesis and degradation of matrix proteins is guaranteed by the action of a family of zinc-dependent, neutral proteinases designated matrix metalloproteases (MMPs).1 A tight regulation of these proteases is accomplished by different mechanisms, including the regulation of gene expression, the processing of the inactive zymogenes by other proteases, and finally, the inhibition of the active enzymes by the action of endogenous inhibitors of MMPs, the TIMPs (for review, see Ref. 4). Cultured mesangial cells (MC) respond to proinflammatory cytokines such as tumor necrosis factor or interleukin-1␤ (IL-1␤) with the production of several MMPs, including MMP-9 (gelatinase-B), mainly due to an increase in gene transcription (5, 6). The transcriptional regulation of the rat MMP-9 gene by proinflammatory cytokines is localized to a 0.7-kb region upstream from the transcriptional start site and critically depends on the binding sites for activator protein-1 (AP-1) and nuclear factor B (NF-B) transcription factors, respectively (5, 7). Besides MMP-9, MC under inf...

Peroxisome Proliferator-activated Receptor-γ Down-regulates Chondrocyte Matrix Metalloproteinase-1 via a Novel Composite Element

“…Computer analysis of the human MMP3 (GenBank TM accession number AF405705) allowed us to identify a degenerated DR1-PPRE overlapping an AP1 element at position Ϫ73 to Ϫ63 (CAAGGATGAGTCA). Two PPREs were recently identified in the rat MMP9 promoter (48). Most interesting, we found a degenerated PPRE sequence overlapping an AP1 element (TGAGTCAGAAGTTCG) at position Ϫ1661 to Ϫ1646 in the human MMP9 promoter (GenBank TM accession number AF538 844).…”

α3β1 integrin regulates MMP-9 mRNA stability in immortalized keratinocytes: a novel mechanism of integrin-mediated MMP gene expression

“…Parallel blots with anti-phospho-ERK confirmed ERK activation in RasV12-infected cells and inhibition of ERK activation by treatment with U0126 (pERK panel). α3β1 integrin regulates MMP-9 mRNA stability production/secretion (Akool et al, 2003;Eberhardt et al, 2002;Jiang and Muschel, 2002;Morini et al, 2000;Sehgal and Thompson, 1999;Thant et al, 2000;Westermarck and Kahari, 1999). In order to determine whether α3β1 regulates MMP-9 mRNA levels, we performed northern blot analysis on total RNA isolated from MK cells cultured on LN-5 ECM in the presence of serum for 4 days, conditions which support similarly high survival of both MK +/+ cells and MK -/-cells (Manohar et al, 2004).…”

“…Although most published studies have focused on transcriptional control of MMP-9 (reviewed by Westermarck and Kahari, 1999), there is increasing evidence that its expression can also be regulated at the steps of mRNA stability, translation and protein secretion (Akool et al, 2003;Eberhardt et al, 2002;Jiang and Muschel, 2002;Morini et al, 2000;Sehgal and Thompson, 1999;Thant et al, 2000). The ability to modulate MMP-9 expression at multiple steps through distinct signaling pathways may be particularly important during malignant conversion and metastasis, when tumor cells need to induce or maintain MMP-9 levels in response to changing environmental cues.…”

αCP1 Mediates Stabilization of hTERT mRNA by Autocrine Human Growth Hormone

“…mRNA Decay Measurements-To estimate the mRNA decay rates, transcription was inhibited by adding 5 g/ml actinomycin D in medium (56). RNA was extracted at the indicated times, and the endogenous hTERT and ␤-actin mRNA levels were analyzed by Northern blotting.…”