The hematopoietic transcription factor PU.1 represses gelatinase A transcription in glomerular mesangial cells

PU.1 and epigenetic signals modulate 1,25-dihydroxyvitamin D3 and C/EBPα regulation of the human cathelicidin antimicrobial peptide gene in lung epithelial cells

LL-37, the only known human cathelicidin which is encoded by the human antimicrobial peptide (CAMP) gene, plays a critical role in protection against bacterial infection. We previously demonstrated that cathelicidin is induced by 1,25-dihydroxyvitamin D₃ (1,25(OH) ₂ D ₃ ) in human airway epithelial cells with a resultant increase in bactericidal activity. In this study we identify key factors that co-operate with 1,25(OH) ₂ D ₃ in the regulation of CAMP. Our results show for the first time that PU.1, the myeloid transcription factor (which has also been identified in lung epithelial cells), co-operates with the vitamin D receptor and CCAAT/enhancer binding protein α (CEBPα) to enhance the induction of CAMP in lung epithelial cells. Our findings also indicate that enhancement of 1,25(OH) ₂ D ₃ regulation of CAMP by histone deacetylase inhibitors involves co-operation between acetylation and chromatin remodeling through Brahma-related gene 1 (BRG1; a component of the SWItch/sucrose nonfermentable [SWI/SNF] complex). BRG1 can be an activator or repressor depending on BRG1-associated factors. Protein arginine methyltransferase 5 (PRMT5), a methlytransferase which interacts with BRG1, represses 1,25(OH) ₂ D ₃ induced CAMP in part through dimethylation of H4R3. Our findings identify key mediators involved in the regulation of the CAMP gene in lung epithelial cells and suggest new approaches for therapeutic manipulation of gene expression to increase the antibacterial capability of the airway.

Y-box Protein-1 Regulates the Expression of Collagen I in Hepatic Progenitor Cells via PDGFR-β/ERK/p90RSK Signalling

Y-box protein-1 (YB-1) is a highly conserved transcription factor that is involved in multiple biological processes via transcriptional regulation of several genes, including p53, cyclin D1, and EGFR. YB-1 has been reported to be overexpressed in injured livers. This study aims to explore the functions of YB-1 in hepatic progenitor cells (HPCs). Herein, chromatin immunoprecipitation sequencing (ChIP-sequencing) and RNA-sequencing assays identified that YB-1 participated in the biological adhesion process and ECM-receptor interactions in HPCs. Further study demonstrated that YB-1 modulated the expression of extracellular matrix components in HPCs. ChIP-sequencing assays established that PDGFR-β was a target gene of YB-1, and luciferase reporter assays confirmed that YB-1 negatively regulated PDGFR-β promoter activity in HPCs. In addition, PDGFR-β can regulate the expression of collagen I through ERK/p90RSK signalling, and disruption of the signalling pathway with a PDGFR-β inhibitor or ERK1/2 inhibitor abolished the regulatory effect of PDGFR-β on collagen I expression in HPCs. Conclusively, YB-1 can modulate the expression of collagen I in HPCs via direct binding to the PDGFR-β promoter, negatively regulating its expression. In addition, the ERK/p90RSK axis serves as the downstream signalling pathway of PDGFR-β.

Characterization of the transcriptional regulation of the human MT1-MMP gene and association of risk reduction for focal-segmental glomerulosclerosis with two functional promoter SNPs

BACKGROUND

The matrix metalloproteinase MT1-MMP (MMP-14) is an important player in wound healing, bone development, angiogenesis, inflammation and tumour invasion. MT1-MMP also plays an important role in the development and resolution of experimental kidney diseases. The role of MT1-MMP was investigated for distinction between minimal-change glomerulonephritis (MCGN) and focal-segmental glomerulosclerosis (FSGS) that can sometimes be difficult due to sampling error in renal biopsy.

METHODS

We defined the transcriptional regulation of the human MT1-MMP and the influence of single nucleotide polymorphisms (SNPs) within its promoter region in renal mesangial cells with reporter gene constructs and gel sift analysis. Genomic DNA from healthy blood donors (n = 500) and from kidney biopsies with defined renal diseases (MCGN: n = 189, FSGS: n = 311) was screened for MT1-MMP promoter SNPs.

RESULTS

Transcription of MT1-MMP is regulated by two enhancers, an Sp1 binding site and a regulatory region 1 (RR1). RR1 contains an Ets site binding the transcription factors Elf-1 and E1AF but not NFAT. The MT1-MMP promoter contains two SNPs (-378 T/C and -364 G/T) in close vicinity to the RR1. Occurrence of the SNP variant -378 C leads to strong inhibition of nuclear protein binding to the RR1 reducing its enhancer function. Appearance of either variant -378 C or variant -364 T in at least one copy of the MT1-MMP promoter was associated with a significant risk reduction for the development of FSGS (P < 0.048).

CONCLUSION

Genetic testing for MT1-MMP promoter SNPs could put renal biopsy results into new perspective. An independent study will be required to verify these findings and their possible diagnostic value for differentiation between certain renal diseases.

Regulation of MMP-2 Gene Transcription in Dermal Wounds

Matrix metalloproteinase-2 (MMP-2, gelatinase A) plays an essential role in angiogenesis, inflammation, and fibrosis. These processes are critical for wound healing and accordingly elevated levels of MMP-2 expression have been detected after skin injury. Our goal was to investigate the transcriptional activation of the MMP-2 gene in a model of skin injury by using two different MMP-2/LacZ-reporter mice. Upon skin injury MMP-2 expression was upregulated, whereas tissue from normal skin stained negative except for occasional macrophages, sweat glands, and hair follicles. Skin injury also activated MMP-2 proteolytic activity and reporter gene expression. We demonstrate that MMP-2 regulatory sequences -1686/+423 drive appropriate injury-induced MMP-2-promoter activation. Reporter gene expression was predominantly detectable in endothelial cells and in macrophages. Deletion of the 5' responsive element, denoted RE-1, residing at -1241/+423 bp of the regulatory sequence led to abrogated MMP-2 transcription in vivo. The findings define a crucial role for the enhancer element RE-1 in injury-induced MMP-2 transcription of the skin.

Polymeric meshes induce zonal regulation of matrix metalloproteinase‐2 gene expression by macrophages and fibroblasts

Matrix metalloproteinase-2 (MMP-2) is a key regulator in wound healing that orchestrates tissue remodeling. In the present study the spatial and temporal distribution of MMP-2 gene transcription, protein synthesis, and enzymatic activity were analyzed following polymeric mesh (polyglactin, polypropylene) implantation in transgenic reporter mice harboring MMP-2 regulatory sequences -1686/+423 or -1241/+423. Polymers induced MMP-2 promoter activity in macrophages within the foreign body granuloma via sequences -1686/+423 with concomitantly up-regulated protein synthesis and enzymatic activity. Macrophages distant from mesh filaments exhibited low MMP-2 expression levels. Fibroblasts surrounding mesh material displayed strong MMP-2 gene transcription independent of the included promoter sequences, whereas fibroblasts without close contact to mesh material had low MMP-2 synthesis rates due to silencing activity of sequences -1686/-1241. In vitro studies support a cellular crosstalk concept, as macrophages trans-repressed MMP-2 gene transcription in fibroblasts. The zonal and cell-specific regulation of MMP-2 gene transcription illuminates an intimate cellular crosstalk in foreign body reaction that may provide a new approach for mesh modification.

The Novel WD-repeat Protein Morg1 Acts as a Molecular Scaffold for Hypoxia-inducible Factor Prolyl Hydroxylase 3 (PHD3)

Hypoxia-inducible factor-1 (HIF-1), a transcriptional complex composed of an oxygen-sensitive alpha- and a beta-subunit, plays a pivotal role in cellular adaptation to low oxygen availability. Under normoxia, the alpha-subunit of HIF-1 is hydroxylated by a family of prolyl hydroxylases (PHDs) and consequently targeted for proteasomal degradation. Three different PHDs have been identified, but the difference among their in vivo roles remain unclear. PHD3 is strikingly expressed by hypoxia, displays high substrate specificity, and has been identified in other signaling pathways. PHD3 may therefore hydroxylate divergent substrates and/or connect divergent cellular responses with HIF. We identified a novel WD-repeat protein, recently designated Morg1 (MAPK organizer 1), by screening a cDNA library with yeast two-hybrid assays. The interaction between PHD3 and Morg1 was confirmed in vitro and in vivo. We found seven WD-repeat domains by cloning the full-length cDNA of Morg1. By confocal microscopy both proteins co-localize within the cytoplasm and the nucleus and display a similar tissue expression pattern in Northern blots. Binding occurs at a conserved region predicted to the top surface of one propeller blade. Finally, HIF-mediated reporter gene activity is decreased by Morg1 and reduced to basal levels when Morg1 is co-expressed with PHD3. Suppression of Morg1 or PHD3 by stealth RNA leads to a marked increase of HIF-1 activity. These results indicate that Morg1 specifically interacts with PHD3 most likely by acting as a molecular scaffold. This interaction may provide a molecular framework between HIF regulation and other signaling pathways.

Transcription regulatory complex including YB-1 controls expression of mouse matrix metalloproteinase-2 gene in NIH3T3 cells

Matrix metalloproteinase 2 (MMP-2) is a metalloproteinase belonging to a family of structurally related zinc-dependent endopeptidases capable of degrading extracellular matrix components. To elucidate the functional promoter of the mouse MMP-2 gene, systematic transient expression analysis of the 5'-flanking region of the MMP-2 gene was performed using serially nested deletions. The deletion analysis indicated that the proximal 327-bp sequence from nucleotide positions -313 to +14 relative to the transcription start site is essential for minimal promoter activity and that a 10-bp sequence of the promoter at positions -939 to -930 is required for high expression level of the MMP-2 gene. The 10-bp fragment functioned as a potent stimulator of heterologous SV40 promoter activity. This element is identical to the YB-1 binding motif (Y-box) present within the responsive element-1 (RE-1), which has been shown to act as a potent cis-activator of transcription of the rat MMP-2 gene. The binding of a nuclear factor(s) to the 10-bp fragment was also revealed by electrophoretic mobility shift assays (EMSAs). Antibody-supershift EMSAs of nuclear extracts from NIH 3T3 cells demonstrated YB-1 binding to the RE-1 sequence. It was concluded that the RE-1 is the conserved element for potent expression of MMP-2 gene among rodents.

Linked common polymorphisms in the gelatinase a promoter are associated with diminished transcriptional response to estrogen and genetic fitness

Gelatinase A (matrix metalloproteinase-2) plays a prominent role in multiple biologic processes. Prior studies have established critical roles for gelatinase A transcriptional regulation by defined enhancer elements. To determine possible functional single nucleotide polymorphisms within these elements, we determined the single nucleotide polymorphism distribution within 1,665 bp of the gelatinase A 5'-flanking region, using a healthy homogeneous Caucasian study group of 463 individuals. Among the polymorphisms detected, a G --> A transition at bp -1575 was located immediately 5' to a half-palindromic potential estrogen receptor binding site. In estrogen receptor-positive MCF-7 cells the -1575G allele functioned as an enhancer, whereas the -1575A allele reduced transcription activity significantly. Gel shift assays confirmed that the differences in allelic expression affected binding of the estrogen receptor-alpha to this region. Cotransfection experiments with an estrogen receptor-alpha expression vector in MDA-MB-231 cells, which do not constitutively express an estrogen receptor, revealed that estrogen receptor is absolutely required for enhancing activity. Allelic distribution analysis indicated that a previously reported C --> T transition within an Sp1 binding site at -1306 was in linkage disequilibrium with the -1575G --> A transition. Luciferase reporter studies of the linked variant -1575A -1306T allele versus the wild type -1575G -1306C allele demonstrated an additive reduction in estrogen-dependent reporter activity. The frequency of the -1575G --> A transition deviated significantly from the expected Hardy-Weinberg distribution in two independently assembled study populations consisting of healthy adult blood donors and newborns of Caucasian origin, both with a calculated 21% reduction in genetic fitness. Gelatinase A is a known estrogen-responsive gene and the demonstration of a loss of function polymorphism within an operational estrogen receptor binding site associated with a decrease in genetic fitness underscores the biologic significance of promoter polymorphism analyses.

Linked common polymorphisms in the gelatinase a promoter are associated with diminished transcriptional response to estrogen and genetic fitness

Gelatinase A (matrix metalloproteinase-2) plays a prominent role in multiple biologic processes. Prior studies have established critical roles for gelatinase A transcriptional regulation by defined enhancer elements. To determine possible functional single nucleotide polymorphisms within these elements, we determined the single nucleotide polymorphism distribution within 1,665 bp of the gelatinase A 5'-flanking region, using a healthy homogeneous Caucasian study group of 463 individuals. Among the polymorphisms detected, a G --> A transition at bp -1575 was located immediately 5' to a half-palindromic potential estrogen receptor binding site. In estrogen receptor-positive MCF-7 cells the -1575G allele functioned as an enhancer, whereas the -1575A allele reduced transcription activity significantly. Gel shift assays confirmed that the differences in allelic expression affected binding of the estrogen receptor-alpha to this region. Cotransfection experiments with an estrogen receptor-alpha expression vector in MDA-MB-231 cells, which do not constitutively express an estrogen receptor, revealed that estrogen receptor is absolutely required for enhancing activity. Allelic distribution analysis indicated that a previously reported C --> T transition within an Sp1 binding site at -1306 was in linkage disequilibrium with the -1575G --> A transition. Luciferase reporter studies of the linked variant -1575A -1306T allele versus the wild type -1575G -1306C allele demonstrated an additive reduction in estrogen-dependent reporter activity. The frequency of the -1575G --> A transition deviated significantly from the expected Hardy-Weinberg distribution in two independently assembled study populations consisting of healthy adult blood donors and newborns of Caucasian origin, both with a calculated 21% reduction in genetic fitness. Gelatinase A is a known estrogen-responsive gene and the demonstration of a loss of function polymorphism within an operational estrogen receptor binding site associated with a decrease in genetic fitness underscores the biologic significance of promoter polymorphism analyses.

Differential regulation of interleukin-10 production by genetic and environmental factors--a twin study

Interleukin-10 (IL-10) has a critical role in the regulation of immune responses. The relative contribution of genetic and environmental factors to IL-10 production is under debate. We performed a twin study in 246 monozygotic and dizygotic twins to assess the heritability of IL-10 production after LPS stimulation in whole blood. In addition, the influence of promoter single nucleotide polymorphisms (-1082, -819 and -592) on transcriptional activity and their binding to nuclear factors was studied in luciferase reporter gene and electrophoretic mobility shift assays. IL-10 production showed a genetic determination with a heritability of 0.5. Decreasing body mass index (BMI), smoking and female gender lead to decreased IL-10 production. In monocytes, the -1082A allele showed higher binding affinity to the transcription factor PU.1 resulting in decreased transcriptional activity of -1082A promoter haplotypes. Genetic determination of IL-10 secretion is probably lower than that previously reported. Fifty percent of the observed variability explained by genetic factors. Female individuals produce less IL-10 than male subjects. Environmental factors like smoking and decreasing BMI exert suppressing effects on IL-10 production. Although the -1082A allele shows higher binding affinity to the PU.1 transcription factor and lower transcriptional activity, this polymorphism probably explains only a small fraction of the observed heritability.

Transcription factor Ets-1 regulates gelatinase a gene expression in mesangial cells

Ets transcription factors are involved in cell growth and angiogenesis. Ets-1 targets include members of the matrix metalloproteinase superfamily. In inflammatory glomerular diseases, the patterns and regulation of Ets expression have not been fully characterized. In the present study, nuclear binding activities to the consensus Ets-1/PEA3 motif were detected in mesangial cells (MC), and the Ets-1 protein was positively identified by Western blotting, reverse transcription PCR (RT-PCR), and DNA-binding studies. The 5' flanking regions of the human and rat gelatinase A genes contain clusters of potential Ets-1 binding motifs, one of which is evolutionarily conserved. Using a series of 5' deletion reporter constructs of the rat gelatinase A gene and an Ets-1 expression plasmid, a concentration-dependent threefold trans-activation of gene expression mapped to the conserved Ets-1 binding motif at -1004/-1053 bps, designated responsive element-2 (RE-2). The RE-2 was operative within the context of the homologous gelatinase A promoter but not with a heterologous simian virus 40 promoter. Specific Ets-1 binding to this sequence was demonstrated by DNA-binding studies. Transient expression of an Ets-1 expression plasmid increased gelatinase A protein expression. Our findings identify an additional matrix metalloproteinase family member, gelatinase A, as an Ets-1 responsive gene in MC that may play a role in the high level expression of this enzyme in inflammatory glomerular diseases.

Mesangial cell gelatinase A synthesis is attenuated by oscillating hyperbaric pressure

Glomerular hypertension has been established as a major factor contributing to glomerular scarring. Underlying cellular mechanisms leading to matrix accumulation are largely unknown. The isolated effect of oscillating hyperbaric pressure [OP; P(max) 50 mmHg (1 mmHg=0.133 kPa), P(mean) 24 mmHg, with a fixed oscillation of 60/min] on matrix-degrading protease secretion by rat mesangial cells (MCs) was analysed using a pressure chamber model described previously [Mertens, Espenkott, Venjakob, Heintz, Handt and Sieberth (1998) Hypertension 32, 945-952]. MCs were grown under atmospheric pressure (AP) or a controlled OP, and protease synthesis and gene transcription were analysed. A distinct biphasic cellular response to OP with stimulated gelatinase A protein expression and enzyme activity during the initial 24 h, and subsequent inhibition, was apparent, as shown by gelatin zymography. Gelatinase B activity remained unchanged. The abundance of gelatinase A transcripts, determined by reverse transcriptase-PCR, indicated a concordant regulation of gene transcription. To elucidate underlying regulatory events, reporter constructs were transfected. In these experiments, a recently identified response element, RE-1, conferred a significant stimulatory effect within the initial 4 h of OP. Nuclear protein/RE-1 binding studies revealed additional complexes from 5 min up to 3 h after OP exposure, with intensities dependent on P(max). STAT3 was identified as a component of these novel complexes. Down-regulation of cis-activity after 48 h of OP exposure was not transferred via the proximal 1686 bp of the gelatinase A regulatory sequence. In conclusion, hyperbaric OP elicits time-dependent changes in rat MC gelatinase A gene transcription.

The potential of bone marrow-derived cells to differentiate to glomerular mesangial cells

Bone marrow stem cells (BMC) develop into hematopoietic and mesenchymal lineages but have not been known to differentiate into glomerular cells. To investigate whether such differentiation is possible, a search was made for donor glomerular cells in lethally irradiated C57BL/6j (B6) mice given transplants of BMC from syngeneic mice transgenic for green fluorescence protein (GFP) ([GFP-->B6] mice). After the recipients of donor BMC manifested GFP-positive cells in their glomeruli, the numbers of such cells increased markedly, in a time-dependent manner, from 2 wk to 24 wk after bone marrow transplantation. Immunohistochemical analyses revealed that most GFP-positive cells in the glomeruli were neither macrophages nor T cells. With the use of a laser-scanning confocal microscope, GFP-positive cells were observed within the mesangium of [GFP-->B6] mice. Furthermore, indirect immunofluorescence assays demonstrated that desmin-positive cells in the glomeruli of these chimeric mice were also positive for GFP. Among glomerular cells isolated from [GFP-->B6] mice 24 wk after bone marrow transplantation and then cultured, the majority of cells (approximately 84%) stained for desmin and approximately 60% of the desmin-positive cells expressed GFP. In addition, these GFP-positive cells in the cultures contracted in response to angiotensin II stimulation. These results suggest that bone marrow-derived cells may have the potential to differentiate into glomerular mesangial cells.