Opposite, binary regulatory pathways involved in IL-1-mediated stromelysin gene expression in rat mesangial cells

Progestin-inflammatory cytokine interactions affect matrix metalloproteinase-1 and -3 expression in term decidual cells: implications for treatment of chorioamnionitis-induced preterm delivery

CONTEXT

Chorioamnionitis (CAM)-elicited preterm delivery (PTD) is associated with elevated amniotic fluid levels of IL-1beta and TNF-alpha. We hypothesized that IL-1beta and TNF-alpha may induce matrix metalloproteinase (MMP)-1 and MMP-3 activity to promote PTD by degrading decidual and fetal membranes and cervical extracellular matrix.

OBJECTIVE

Our objective was to evaluate: 1) MMP-1 and MMP-3 expression in decidual sections from uncomplicated term, idiopathic preterm, and CAM-complicated deliveries, and 2) the separate and interactive effects of IL-1beta, TNF-alpha, medroxyprogesterone acetate (MPA), and a p38 MAPK inhibitor (SB203580) on MMP-1 and MMP-3 expression in term decidual cells (DCs).

INTERVENTIONS AND MAIN OUTCOME MEASURES

Decidua were immunostained for MMP-1 and MMP-3. Cultured term DCs were incubated with estradiol (E2) or E2 plus MPA with or without IL-1beta or TNF-alpha with or without SB203580. ELISA and Western blotting assessed secreted MMP-1 and MMP-3 levels, quantitative real-time RT-PCR assessed mRNA levels, and substrate gel zymography was used to determined MMP-1 and MMP-3 proteolytic activity.

RESULTS

MMP-1 and MMP-3 immunostaining was more prominent in CAM-complicated decidua vs. control preterm and term decidual specimens (P < 0.05). Compared with basal outputs by DCs incubated with E2, TNF-alpha enhanced MMP-1 and MMP-3 secretion by 14 +/- 3- and 9 +/- 2-fold, respectively, and IL-1beta increased MMP-1 and MMP-3 secretion by 13 +/- 3- and 19 +/- 2-fold, respectively (P < 0.05). Addition of MPA lowered basal MMP-1 and MMP-3 outputs by 70%, whereas the TNF-alpha- and IL-1beta-enhanced MMP-1 and MMP-3 levels were blunted by more than 50% (P < 0.05). SB203580 suppressed TNF-alpha- and IL-1beta-induced MMP-1 and MMP-3 secretion by severalfold. Western blotting confirmed the ELISA results, and mRNA levels corresponded with MMP-1 and MMP-3 protein levels. MMP-1 and MMP-3 proteolytic activity was confirmed by substrate gel zymography.

CONCLUSION

Augmented DC-expressed MMP-1 and MMP-3 in CAM-complicated pregnancies may promote PTD via decidual, fetal membrane, and cervical extracellular matrix degradation. Effects of progestin-p38 MAPK signaling inhibition on cytokine-enhanced MMP-1 and MMP-3 expression in term DCs suggest alternative mechanisms to prevent CAM-induced PTD.

AP-1-independent sensitization to oxidative stress-induced apoptosis by proteasome inhibitors

Hydrogen peroxide (H(2)O(2)) induces apoptosis of mesangial cells via c-Jun N-terminal kinase (JNK)-activator protein-1 (AP-1) and extracellular signal-regulated kinase (ERK)-AP-1 pathways. We recently found that subtoxic doses of proteasome inhibitors, MG132 and lactacystin, dramatically enhanced H(2)O(2)-induced apoptosis in mesangial cells. In this report, we examined molecular mechanisms involved in this phenomenon, especially focusing on AP-1 pathways. Reporter assays showed that MG132 induced activation of AP-1. However, pharmacological inhibitors of AP-1, retinoic acid, and curcumin, did not suppress the proapoptotic effect of MG132. Suppression of JNK-AP-1 by transfection with either a dominant-negative mutant of JNK or a dominant-negative mutant of c-Jun did not attenuate the apoptosis enhancement by MG132. Similarly, suppression of ERK-AP-1 by PD98059 or dominant-negative mutants of ERK did not affect the apoptosis-promoting effect of MG132. Interestingly, pretreatment with MG132 did not enhance activation of AP-1 by H(2)O(2). These data suggested a novel, AP-1-independent promotion of apoptosis by proteasome inhibitors.

Cellular defense against H2O2-induced apoptosis via MAP kinase-MKP-1 pathway

Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) is an oxidative stress-inducible gene. In this study, we investigated signaling pathways involved in oxidative stress-induced MKP-1 expression and its role in apoptosis of rat mesangial cells. Northern and Western blot analyses showed that H(2)O(2) induced expression of MKP-1 mRNA and protein in a dose-dependent manner, without affecting the stability of the transcript. H(2)O(2) induced phosphorylation of extracellular signal-regulated kinase, p38 MAP kinase, and c-Jun N-terminal kinase and consequently activated activator protein 1 (AP-1). Selective inhibitors of individual MAP kinases or a dominant-negative mutant of c-jun significantly suppressed the expression of MKP-1 by H(2)O(2). Inhibition of MKP-1 by a protein tyrosine phosphatase inhibitor (vanadate) enhanced H(2)O(2)-triggered apoptosis. Consistently, transfection with a wild-type MKP-1, but not its catalytically inactive mutant MKP-1CS, attenuated H(2)O(2)-induced apoptosis. These data elucidate, for the first time, that induction of MKP-1 by H(2)O(2) is mediated by the MAP kinase-AP-1 pathway and that the induced MKP-1 is involved in cellular defense against oxidative stress-induced apoptosis of mesangial cells.

Inflamed glomeruli-specific gene activation that uses recombinant adenovirus with the Cre/loxP system

The authors previously reported that bone marrow-derived CD11b(+)CD18(+) cells could be used as a vehicle to deliver foreign genes into inflamed glomeruli and that this vehicle cell (v-cell) could retard the progression of nephritis by delivering anti-inflammatory molecules. As a next step, the authors tried to establish a switching system by which v-cells are activated only at the inflamed glomeruli. A recombinant adenovirus (Ad) that expressed Cre recombinase under the control of the interleukin-1 beta (IL-1 beta) promoter (AxIL-1pr/Cre) was constructed and transfected into v-cells. After confirming that AxIL-1pr/Cre expresses Cre by lipopolysaccharide (LPS) treatment, AxIL-1pr/Cre was infected together with another Ad bearing a switching reporter unit in which the LacZ gene is activated under the control of the CAG promoter by the Cremediated excisional deletion of interposed stuffer DNA. Only a negligible number of double-infected (Cre/loxPCAG) cells expressed LacZ. This number, however, was significantly increased by LPS, which suggests that LPS-induced Cre effectively deletes the stuffer DNA, which allows for a complete CAG promoter. DBA/2j mice were then transplanted with Cre/loxPCAG cells via a tail vein and treated with anti-glomerular basement membrane (GBM) serum. To trace the transplanted cells, marker v-cells, infected with AxCANLacZ to constitutively express the LacZ gene, were also used. Although transplanted cells expressing LacZ collected in the spleen independent of anti-GBM treatment, they did not express the LacZ gene in the mice transplanted with Cre/loxPCAG cells. On the other hand, transplanted cells were recruited in the glomeruli and expressed the LacZ gene upon anti-GBM treatment. These results suggested that only the v-cells recruited in the glomeruli could be switched on and activate foreign genes.

Unexpected transcriptional induction of monocyte chemoattractant protein 1 by proteasome inhibition: involvement of the c-Jun N-terminal kinase-activator protein 1 pathway

Proteasome inhibitors, the well-known inhibitors of NF-kappaB, are recently considered therapeutic agents for inflammation. However, the anti-inflammatory properties of these agents have not been fully evaluated. In this report we describe a novel effect of proteasome inhibitors on the expression of monocyte chemoattractant protein 1 (MCP-1) in mesangial cells. We found that proteasome inhibitor MG132 dose-dependently induced expression of MCP-1 at the transcriptional level. The stimulatory effect was similarly observed with other proteasome inhibitors (proteasome inhibitor 1 and lactacystin) and in other cell types (NRK fibroblasts). The 5'-flanking region of the MCP-1 gene contains multiple AP-1 sites. To explore the mechanisms involved, we examined the effects of proteasome inhibition on the AP-1 pathway. Northern blot analysis showed that MG132 rapidly induced the expression of c-jun, but not c-fos. Immunoblot analysis showed that MG132 prevented degradation of c-Jun protein. Kinase assay revealed that c-Jun N-terminal kinase (JNK) was rapidly activated by MG132. Consistent with these results, a reporter assay showed that AP-1 activity was up-regulated after treatment with MG132. Curcumin, a pharmacological inhibitor of the JNK-AP-1 pathway, abrogated the induction of MCP-1 by MG132. Similarly, stable transfection with a dominant-negative mutant of c-Jun attenuated both MG132-induced activation of AP-1 and expression of MCP-1. The transcriptional activation by proteasome inhibitors was observed not only in MCP-1, but also in other AP-1-dependent genes, including stromelysin and mitogen-activated protein kinase phosphatase 1. These data revealed that proteasome inhibition triggered the expression of MCP-1 and other genes via the multistep induction of the JNK-c-Jun/AP-1 pathway.

Genetically modified bone marrow continuously supplies anti-inflammatory cells and suppresses renal injury in mouse Goodpasture syndrome

In chronic inflammation, macrophages and neutrophils, which are derived from bone marrow, play a pivotal role. Therefore, reconstitution of bone marrow with anti-inflammatory stem cells may modify inflammation. In this study, transplantation-based gene therapy was applied to glomerular inflammation for a long-lasting suppression of the glomerular damage seen in chronic nephritis. Bone marrow cells were harvested from male donor mice, which had received 5-fluorouracil 3 days previously, and transduced with an interleukin 1 (IL-1) receptor antagonist (IL-1Ra) or a mock gene using a retrovirus vector. After confirmation that transduced cells possessed the transgene at approximately 0.7 copies per cell and secreted recombinant IL-1Ra, these cells were infused into sublethally irradiated (6 Gy) female recipients once daily for 4 consecutive days. These female recipient mice had the male Y antigen in bone marrow, liver, and spleen, and 10% to 20% of their spleen cells possessed the transgene even 8 weeks after transplantation. Glomerulonephritis was then induced in these mice. Renal function and histology were retarded in the mice whose bone marrow was reconstituted with IL-1Ra-producing cells compared with mock transduced cells. In situ hybridization using a Y painting probe revealed that transplanted donor cells were recruited into the glomerulus upon induction of nephritis, suggesting therapeutic effects were channeled through the secretion of IL-1Ra from these cells. Furthermore, the survival rate after a second challenge with nephrotoxic antibody was significantly improved in the IL-1Ra chimera. These results suggest that reconstitution of bone marrow for continuous supply of anti-inflammatory cells may be a useful strategy for the treatment of chronic inflammation.

Suppression of constitutive but not Il-1beta-inducible expression of monocyte chemoattractant protein-1 in mesangial cells by retinoic acids: intervention in the activator protein-1 pathway

Retinoic acid regulates a wide range of biologic processes, including inflammation. This study investigated the effect of all-trans-retinoic acid (t-RA) on the constitutive and cytokine-inducible expression of monocyte chemoattractant protein 1 (MCP-1) in rat mesangial cells. Serum-deprived mesangial cells exhibited substantial levels of MCP-1 mRNA, and the expression was markedly upregulated by interleukin-1beta (IL-1beta). Pretreatment with t-RA abrogated the constitutive mRNA expression but did not inhibit the IL-1beta-inducible expression. The similar effects were observed by 9-cis-RA. The suppressive effect of t-RA required retinoic acid receptors. t-RA did not affect the stability of MCP-1 mRNA, indicating that its suppressive effect was at the transcriptional level. Experiments that used pharmacologic and genetic inhibitors showed that the IL-1beta-inducible MCP-1 expression was dependent on nuclear factor-kappaB (NF-kappaB) and independent of activator protein 1 (AP-1). In contrast, the constitutive expression of MCP-1 was dependent on both NF-kappaB and AP-1. t-RA substantially inhibited the constitutive activity of AP-1 but did not inhibit NF-kappaB activity in mesangial cells. These data suggested that (1) constitutive and IL-1beta-inducible expression of MCP-1 was differently regulated by AP-1 and NF-kappaB and (2) t-RA inhibited selectively the constitutive expression of MCP-1 via intervention in the AP-1 pathway.

Spontaneous shift in transcriptional profile of explanted glomeruli via activation of the MAP kinase family

To understand how isolation and explantation of glomeruli affect the function of resident cells, the present study investigated the transcriptional profile of explanted normal glomeruli. We found that ex vivo incubation of glomeruli spontaneously expressed monocyte chemoattractant protein-1 (MCP-1) and stromelysin, the genes regulated by activator protein-1 (AP-1). The expression was suppressed by heparin and quercetin, the drugs with anti-AP-1 activities. The gene expression was preceded by 1) induction of AP-1 components c-fos and c-jun and 2) phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein (MAP) kinase, and c-Jun NH(2)-terminal kinase (JNK), the upstream inducers/activators of AP-1. Suppression of ERK by PD098059 abrogated induction of c-fos and c-jun, and the p38 MAP kinase inhibitor SB203580 attenuated c-fos expression. Furthermore, treatment with either PD098059, SB203580, or the JNK-AP-1 inhibitor curcumin diminished the expression of MCP-1 and stromelysin. The transcriptional profile of glomerular cells thus alters dramatically after explantation of glomeruli. It is, at least in part, due to activation of multiple MAP kinases that lead to induction of AP-1-dependent gene expression.

Gene, stimulus and cell-type specific regulation of activator protein-1 in mesangial cells by lipopolysaccharide and cytokines

Activator protein-1 (AP-1) plays an important role in the regulation of gene expression in mesangial cells (MC) during the pathogenesis of glomerular inflammatory disease. The precise regulation of the AP-1 family by agents that are known to activate MC is, however, poorly understood. The action of platelet-derived growth factor (PDGF) and, for the first time, lipopolysaccharide (LPS), interleukin-6 (IL-6), interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) on AP-1 gene expression in MC was therefore studied. Whilst the expression of JunD was not affected by any of the mediators, the mRNA levels of c-fos and JunB were induced by LPS, IL-6, IFN-gamma, PDGF and TNF-alpha, and that of c-jun by LPS, IFN-gamma, PDGF and TNF-alpha. Electrophoretic mobility shift assays showed a time-dependent increase in AP-1 DNA binding activity with JunB representing the major mediator-inducible member involved in DNA-protein interactions. However, stimulus-specific changes in the kinetics and magnitude of AP-1 mRNA expression and DNA binding activity were identified and, additionally, the results showed the potential existence of cell-type-specific mechanisms in the regulation of the AP-1 family. These studies provide novel insights into the mediator-specific modulation of AP-1-regulated gene expression and the activation of MC in renal diseases.

Bioflavonoid quercetin inhibits interleukin-1-induced transcriptional expression of monocyte chemoattractant protein-1 in glomerular cells via suppression of nuclear factor-kappaB

Flavonoids are semiessential food components that possess anti-inflammatory properties. This report describes a novel potential of bioflavonoid quercetin as an inhibitor of monocyte chemoattractant protein-1 (MCP-1) in glomerular cells. Cultured mesangial cells as well as isolated glomeruli expressed MCP-1 mRNA in response to interleukin-1beta (IL-1beta). Quercetin dramatically inhibited the cytokine-triggered MCP-1 expression. To explore the mechanisms involved, effects of quercetin on the putative transcriptional activators of MCP-1, nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), were examined. Exposure of the cells to IL-1beta caused activation of NF-kappaB without significant upregulation of AP-1 activity. NF-kappaB inhibitor MG132 diminished the IL-1-induced expression of MCP-1 in mesangial cells and isolated glomeruli, whereas c-Jun/AP-1 inhibitor curcumin did not affect this process. Consistently, NF-kappaB-inactive mesangial cells expressing a super-repressor mutant of IkappaBalpha showed blunted expression of MCP-1 by IL-1beta. In contrast, AP-1-inactive mesangial cells expressing a dominant-negative mutant of c-Jun exhibited the same level of MCP-1 mRNA as that in control cells. These results suggest that: (1) quercetin has the ability to attenuate activation of NF-kappaB; and (2) it inhibits IL-1-triggered MCP-1 expression via suppression of NF-kappaB, but not AP-1, in glomerular cells.

Oxidant-induced apoptosis of glomerular cells: intracellular signaling and its intervention by bioflavinoid

Oxidant stress plays a crucial role in the generation of a wide range of glomerular disease. In the first part of this article, we describe intracellular signaling pathways involved in the oxidant-initiated apoptosis of mesangial cells, especially highlighting the tyrosine kinase-c-Jun/AP-1 pathway. In the second part, we address a novel potential of bioflavonoid quercetin as an inhibitor of apoptosis in glomerular cells. Possible mechanisms for the antiapoptotic action of quercetin and its therapeutic utility are discussed.

c-Jun/AP-1, but not NF-kappa B, is a mediator for oxidant-initiated apoptosis in glomerular mesangial cells

Oxidant stress is a trigger of cell death in various cell types. Hydrogen peroxide (H2O2) induced mesangial cell death with nuclear condensation and DNA fragmentation typical of apoptosis. To explore molecular mechanisms involved in this process, redox-sensitive transacting molecules, activator protein-1 (AP-1) and nuclear factor-kappa B (NF-kappa B), have been brought into focus. Northern blot analysis and transient transfection assays using reporter plasmids showed that H2O2 activated both AP-1 and NF-kappa B. Downregulation of c-Jun/AP-1 using a transdominant negative mutant of c-jun, an antisense c-jun, or a pharmacologic inhibitor curcumin inhibited the H2O2-initiated apoptosis. In contrast, inhibition of the NF-kappa B activation using a transdominant negative mutant of the p50 NF-kappa B subunit did not affect the H2O2-triggered cellular death. These data elucidated that c-Jun/AP-1, but not NF-kappa B, is involved in the oxidant-initiated cell death program in glomerular mesangial cells.