Suppression of HGF receptor gene expression by oxidative stress is mediated through the interplay between Sp1 and Egr-1

Differential expression of placental 11β-HSD2 induced by high maternal glucocorticoid exposure mediates sex differences in placental and fetal development

A variety of adverse environmental factors during pregnancy cause maternal chronic stress. Caffeine is a common stressor, and its consumption during pregnancy is widespread. Our previous study showed that prenatal caffeine exposure (PCE) increased maternal blood glucocorticoid levels and caused abnormal development of offspring. However, the placental mechanism for fetal development inhibition caused by PCE-induced high maternal glucocorticoid has not been reported. This study investigated the effects of PCE-induced high maternal glucocorticoid level on placental and fetal development by regulating placental 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) expression and its underlying mechanism. First, human placenta and umbilical cord blood samples were collected from women without prenatal use of synthetic glucocorticoids. We found that placental 11β-HSD2 expression was significantly correlated with umbilical cord blood cortisol level and birth weight in male newborns but not in females. Furthermore, we established a rat model of high maternal glucocorticoids induced by PCE (caffeine, 60 mg/kg·d, ig), and found that the expression of 11β-HSD2 in male PCE placenta was decreased and negatively correlated with the maternal/fetal/placental corticosterone levels. Meanwhile, we found abnormal placental structure and nutrient transporter expression. In vitro, BeWo cells were used and confirm that 11β-HSD2 mediated inhibition of placental nutrient transporter expression induced by high levels of glucocorticoid. Finally, combined with the animal and cell experiments, we further confirmed that high maternal glucocorticoid could activate the GR-C/EBPα-Egr1 signaling pathway, leading to decreased expression of 11β-HSD2 in males. However, there was no significant inhibition of placental 11β-HSD2 expression, placental and fetal development in females. In summary, we confirmed that high maternal glucocorticoids could regulate placental 11β-HSD2 expression in a sex-specific manner, leading to differences in placental and fetal development. This study provides the theoretical and experimental basis for analyzing the inhibition of fetoplacental development and its sex difference caused by maternal stress.

Transcriptional study reveals a potential leptin-dependent gene regulatory network in zebrafish brain

The signal mediated by leptin hormone and its receptor is a major regulator of body weight, food intake and metabolism. In mammals and many teleost fish species, leptin has an anorexigenic role and inhibits food intake by influencing the appetite centres in the hypothalamus. However, the regulatory connections between leptin and downstream genes mediating its appetite-regulating effects are still not fully explored in teleost fish. In this study, we used a loss of function leptin receptor zebrafish mutant and real-time quantitative PCR to assess brain expression patterns of several previously identified anorexigenic genes downstream of leptin signal under different feeding conditions (normal feeding, 7-day fasting, 2 and 6-h refeeding). These downstream factors include members of cart genes, crhb and gnrh2, as well as selected genes co-expressed with them based on a zebrafish co-expression database. Here, we found a potential gene expression network (GRN) comprising the abovementioned genes by a stepwise approach of identifying co-expression modules and predicting their upstream regulators. Among the transcription factors (TFs) predicted as potential upstream regulators of this GRN, we found expression pattern of sp3a to be correlated with transcriptional changes of the downstream gene network. Interestingly, the expression and transcriptional activity of Sp3 orthologous gene in mammals have already been implicated to be under the influence of leptin signal. These findings suggest a potentially conserved regulatory connection between leptin and sp3a, which is predicted to act as a transcriptional driver of a downstream gene network in the zebrafish brain.

Oxidative stress responsive transcription factors in cellular signalling transduction mechanisms

Oxidative stress results from the imbalances in the development of reactive oxygen species (ROS) and antioxidants defence system resulting in tissue injury. A key issue resulting in the modulation of ROS is that it alters hosts molecular, structural and functional properties which is accomplished via various signalling pathways which either activate or inhibit numerous transcription factors (TFs). Some of the regulators include Nuclear erythroid-2 related factors (Nrf-2), CCAAT/enhancer-binding protein delta (CEBPD), Activator Protein-1 (AP-1), Hypoxia-inducible factor 1(HIF-1), Nuclear factor κB (NF-κB), Specificity Protein-1 (SP-1) and Forkhead Box class O (FoxO) transcription factors. The expression of these transcription factors are dependent upon the stress signal and are sometimes interlinked. They are highly specific having their own regulation cellular events. Depending upon the transcription factors and better knowledge on the type of the oxidative stress help researchers develop safe, novel targets which can serve as efficient therapeutic targets for several disease conditions.

Transcriptional Landscape of PARs in Epithelial Malignancies

G protein-coupled receptors (GPCRs), the largest family of cell receptors, act as important regulators of diverse signaling pathways. Our understanding of the impact of GPCRs in tumors is emerging, yet there is no therapeutic platform based on GPCR driver genes. As cancer progresses, it disrupts normal epithelial organization and maintains the cells outside their normal niche. The dynamic and flexible microenvironment of a tumor contains both soluble and matrix-immobilized proteases that contribute to the process of cancer advancement. An example is the activation of cell surface protease-activated receptors (PARs). Mammalian PARs are a subgroup of GPCRs that form a family of four members, PAR_1–4, which are uniquely activated by proteases found in the microenvironment. PAR₁ and PAR₂ play central roles in tumor biology, and PAR₃ acts as a coreceptor. The significance of PAR₄ in neoplasia is just beginning to emerge. PAR₁ has been shown to be overexpressed in malignant epithelia, in direct correlation with tumor aggressiveness, but there is no expression in normal epithelium. In this review, the involvement of key transcription factors such as Egr1, p53, Twist, AP2, and Sp1 that control PAR₁ expression levels specifically, as well as hormone transcriptional regulation by both estrogen receptors (ER) and androgen receptors (AR) are discussed. The cloning of the human protease-activated receptor 2; Par2 (hPar2) promoter region and transcriptional regulation of estrogen (E₂) via binding of the E₂–ER complex to estrogen response elements (ERE) are shown. In addition, evidence that TEA domain 4 (TEAD₄) motifs are present within the hPar2 promoter is presented since the YAP oncogene, which plays a central part in tumor etiology, acts via the TEAD₄ transcription factor. As of now, no information is available on regulation of the hPar3 promoter. With regard to hPar4, only data showing CpG methylation promoter regulation is available. Characterization of the PAR transcriptional landscape may identify powerful targets for cancer therapies.

LL-37 stimulates the functions of adipose-derived stromal/stem cells via early growth response 1 and the MAPK pathway

Background

LL-37 is a naturally occurring antimicrobial peptide found in the wound bed and assists wound repair. No published study has characterized the role of LL-37 in the function(s) of human mesenchymal stem cells (MSCs). This study investigated the functions of adipose-derived stromal/stem cells (ASCs) activated by LL-37 by performing both in vitro assays with cultured cells and in vivo assays with C57BL/6 mice with hair loss.

Methods

Human ASCs were isolated from healthy donors with written informed consent. To examine the effects of LL-37 on ASC function, cell proliferation and migration were measured by a cell counting kit (CCK-8) and a Transwell migration assay. Early growth response 1 (EGR1) mRNA expression was determined by microarray and real-time PCR analyses. The protein levels of EGR1 and regenerative factors were analyzed by specific enzyme-linked immunosorbent assays and western blotting.

Results

LL-37 treatment enhanced the proliferation and migration of human ASCs expressing formyl peptide receptor like-1. Microarray and real-time PCR data showed that EGR1 expression was rapidly and significantly increased by LL-37 treatment. LL-37 treatment also enhanced the production of EGR1. Moreover, small interfering RNA-mediated knockdown of EGR1 inhibited LL-37-enhanced ASC proliferation and migration. Activation of mitogen-activated protein kinases (MAPKs) was essential not only for LL-37-enhanced ASC proliferation and migration but also EGR1 expression; treatment with a specific inhibitor of extracellular signal-regulated kinase, p38, or c-Jun N-terminal kinase blocked the stimulatory effect of LL-37. EGR1 has a strong paracrine capability and can influence angiogenic factors in ASCs; therefore, we evaluated the secretion levels of vascular endothelial growth factor, thymosin beta-4, monocyte chemoattractant protein-1, and stromal cell-derived factor-1. LL-37 treatment increased the secretion of these regenerative factors. Moreover, treatment with the conditioned medium of ASCs pre-activated with LL-37 strongly promoted hair growth in vivo.

Conclusions

These findings show that LL-37 increases EGR1 expression and MAPK activation, and that preconditioning of ASCs with LL-37 has a strong potential to promote hair growth in vivo. This study correlates LL-37 with MSC functions (specifically those of ASCs), including cell expansion, cell migration, and paracrine actions, which may be useful in terms of implantation for tissue regeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0313-4) contains supplementary material, which is available to authorized users.

The miR-199a/Brm/EGR1 axis is a determinant of anchorage-independent growth in epithelial tumor cell lines

In epithelial cells, miRNA-199a-5p/-3p and Brm, a catalytic subunit of the SWI/SNF complex were previously shown to form a double-negative feedback loop through EGR1, by which human cancer cell lines tend to fall into either of the steady states, types 1 [miR-199a(−)/Brm(+)/EGR1(−)] and 2 [miR-199a(+)/Brm (−)/EGR1(+)]. We show here, that type 2 cells, unlike type 1, failed to form colonies in soft agar, and that CD44, MET, CAV1 and CAV2 (miR-199a targets), all of which function as plasma membrane sensors and can co-localize in caveolae, are expressed specifically in type 1 cells. Single knockdown of any of them suppressed anchorage-independent growth of type 1 cells, indicating that the miR-199a/Brm/EGR1 axis is a determinant of anchorage-independent growth. Importantly, two coherent feedforward loops are integrated into this axis, supporting the robustness of type 1-specific gene expression and exemplifying how the miRNA-target gene relationship can be stably sustained in a variety of epithelial tumors.

Sp1 and the 'hallmarks of cancer'

For many years, transcription factor Sp1 was viewed as a basal transcription factor and relegated to a role in the regulation of so-called housekeeping genes. Identification of Sp1's role in recruiting the general transcription machinery in the absence of a TATA box increased its importance in gene regulation, particularly in light of recent estimates that the majority of mammalian genes lack a TATA box. In this review, we briefly consider the history of Sp1, the founding member of the Sp family of transcription factors. We review the evidence suggesting that Sp1 is highly regulated by post-translational modifications that positively and negatively affect the activity of Sp1 on a wide array of genes. Sp1 is over-expressed in many cancers and is associated with poor prognosis. Targeting Sp1 in cancer treatment has been suggested; however, our review of the literature on the role of Sp1 in the regulation of genes that contribute to the 'hallmarks of cancer' illustrates the extreme complexity of Sp1 functions. Sp1 both activates and suppresses the expression of a number of essential oncogenes and tumor suppressors, as well as genes involved in essential cellular functions, including proliferation, differentiation, the DNA damage response, apoptosis, senescence and angiogenesis. Sp1 is also implicated in inflammation and genomic instability, as well as epigenetic silencing. Given the apparently opposing effects of Sp1, a more complete understanding of the function of Sp1 in cancer is required to validate its potential as a therapeutic target.

Increased NQO1 but not c-MET and survivin expression in non-small cell lung carcinoma with KRAS mutations

Cigarette smoking is one of the most significant public health issues and the most common environmental cause of preventable cancer deaths worldwide. EGFR (Epidermal Growth Factor Receptor)-targeted therapy has been used in the treatment of LC (lung cancer), mainly caused by the carcinogens in cigarette smoke, with variable success. Presence of mutations in the KRAS (Kirsten rat sarcoma viral oncogene homolog) driver oncogene may confer worse prognosis and resistance to treatment for reasons not fully understood. NQO1 (NAD(P)H:quinone oxidoreductase), also known as DT-diaphorase, is a major regulator of oxidative stress and activator of mitomycins, compounds that have been targeted in over 600 pre-clinical trials for treatment of LC. We sequenced KRAS and investigated expression of NQO1 and five clinically relevant proteins (DNMT1, DNMT3a, ERK1/2, c-MET, and survivin) in 108 patients with non-small cell lung carcinoma (NSCLC). NQO1, ERK1/2, DNMT1, and DNMT3a but not c-MET and survivin expression was significantly more frequent in patients with KRAS mutations than those without, suggesting the following: (1) oxidative stress may play an important role in the pathogenesis, worse prognosis, and resistance to treatment reported in NSCLC patients with KRAS mutations, (2) selecting patients based on their KRAS mutational status for future clinical trials may increase success rate, and (3) since oxidation of nucleotides also specifically induces transversion mutations, the high rate of KRAS transversions in lung cancer patients may partly be due to the increased oxidative stress in addition to the known carcinogens in cigarette smoke.

Early growth response protein 1 upregulation and nuclear translocation by 2'-benzoyloxycinnamaldehyde induces prostate cancer cell death

2'-Benzoyloxycinnamaldehyde (BCA) induces apoptosis in human cancer cells through ROS generation. BCA upregulates proapoptotic genes such as activating transcription factor 3 (ATF3), NSAID-activated gene 1 protein (NAG-1), and growth arrest and DNA-damage-inducible protein alpha (GADD45A) in prostate cancer cells. These genes are known to be induced by transcription factor early growth response protein 1 (EGR1). BCA induces significant EGR1 upregulation, while EGR1 knockdown decreases the induction of these genes with concurrent alleviation of cell death by BCA. Antioxidant glutathione pretreatment with BCA removes EGR1 expression increase, suggesting that EGR1 upregulation is dependent on oxidative stress generated by BCA. In prostate cancer cells, EGR1 localizes in the cytoplasm; however, BCA remarkably upregulates EGR1 nuclear translocalization, suggesting its possible effect as a transcriptional activator. BCA induces transient upregulation of importin-7 (IPO7) which is critical for EGR1 nuclear translocation, and IPO7 knockdown led to a significant decrease in chemosensitivity to BCA. Taken together, our findings suggest that BCA induces prostate cancer cell death via EGR1 upregulation and nuclear translocalization, followed by activation of proapoptotic target genes.

Downstream and intermediate interactions of synovial sarcoma-associated fusion oncoproteins and their implication for targeted therapy

Synovial sarcoma (SS), an aggressive type of soft tissue tumor, occurs mostly in adolescents and young adults. The origin and molecular mechanism of the development of SS remain only partially known. Over 90% of SS cases are characterized by the t(X;18)(p11.2;q11.2) translocation, which results mainly in the formation of SS18-SSX1 or SS18-SSX2 fusion genes. In recent years, several reports describing direct and indirect interactions of SS18-SSX1/SSX2 oncoproteins have been published. These reports suggest that the fusion proteins particularly affect the cell growth, cell proliferation, TP53 pathway, and chromatin remodeling mechanisms, contributing to SS oncogenesis. Additional research efforts are required to fully explore the protein-protein interactions of SS18-SSX oncoproteins and the pathways that are regulated by these partnerships for the development of effective targeted therapy.

SOD1 Transcriptional and Posttranscriptional Regulation and Its Potential Implications in ALS

Copper-zinc superoxide dismutase (SOD1) is a detoxifying enzyme localized in the cytosol, nucleus, peroxisomes, and mitochondria. The discovery that mutations in SOD1 gene cause a subset of familial amyotrophic lateral sclerosis (FALS) has attracted great attention, and studies to date have been mainly focused on discovering mutations in the coding region and investigation at protein level. Considering that changes in SOD1 mRNA levels have been associated with sporadic ALS (SALS), a molecular understanding of the processes involved in the regulation of SOD1 gene expression could not only unravel novel regulatory pathways that may govern cellular phenotypes and changes in diseases but also might reveal therapeutic targets and treatments. This review seeks to provide an overview of SOD1 gene structure and of the processes through which SOD1 transcription is controlled. Furthermore, we emphasize the importance to focus future researches on investigating posttranscriptional mechanisms and their relevance to ALS.

Suppression of liver regeneration and hepatocyte proliferation in hepatocyte-targeted glypican 3 transgenic mice

Glypican 3 (GPC3) belongs to a family of glycosylphosphatidylinositol-anchored, cell-surface heparan sulfate proteoglycans. GPC3 is overexpressed in hepatocellular carcinoma. Loss-of-function mutations of GPC3 result in Simpson-Golabi-Behmel syndrome, an X-linked disorder characterized by overgrowth of multiple organs, including the liver. Our previous study showed that GPC3 plays a negative regulatory role in hepatocyte proliferation, and this effect may involve CD81, a cell membrane tetraspanin. To further investigate GPC3 in vivo, we engineered transgenic (TG) mice overexpressing GPC3 in the liver under the control of the albumin promoter. GPC3 TG mice with hepatocyte-targeted, overexpressed GPC3 developed normally in comparison with their nontransgenic littermates but had a suppressed rate of hepatocyte proliferation and liver regeneration after partial hepatectomy. Moreover, gene array analysis revealed a series of changes in the gene expression profiles in TG mice (both in normal mice and during liver regeneration). In unoperated GPC3 TG mice, there was overexpression of runt related transcription factor 3 (7.6-fold), CCAAT/enhancer binding protein alpha (2.5-fold), GABA A receptor (2.9-fold), and wingless-related MMTV integration site 7B (2.8-fold). There was down-regulation of insulin-like growth factor binding protein 1 (8.4-fold), Rab2 (5.6-fold), beta-catenin (1.7-fold), transforming growth factor beta type I (3.1-fold), nodal (1.8-fold), and yes-associated protein (1.4-fold). Changes after hepatectomy included decreased expression in several cell cycle-related genes.

CONCLUSION

Our results indicate that in GPC3 TG mice, hepatocyte overexpression of GPC3 suppresses hepatocyte proliferation and liver regeneration and alters gene expression profiles, and potential cell cycle-related proteins and multiple other pathways are involved and affected.

Decreased Serum Hepatocyte Growth Factor (HGF) in Individuals with Anxiety Increases After Zinc Therapy

Aim:

To assess serum Hepatocyte Growth Factor (HGF) levels in individuals with anxiety and to test the hypothesis that there is a relationship between HGF levels and zinc therapy.

Subjects and methods:

Serum from 19 individuals with anxiety and 19 controls were tested for serum HGF using ELISAs. HGF serum concentration in individuals with anxiety before zinc and anti-oxidant therapy was compared to levels after therapy. Zinc and copper levels in anxiety patients, pre and post therapy, were also measured and compared.

Results:

Individuals with anxiety had significantly lower serum levels of HGF compared to controls (P = 0.0005). HGF concentration rose significantly (normalized) after zinc therapy (P = 0.04) and zinc levels increased significantly in these same patients (P = 0.0002).

Discussion:

These results suggest an association between HGF serum levels and individuals with anxiety and demonstrate that zinc therapy is associated with increasing HGF levels.

Decreased Serum Hepatocyte Growth Factor (HGF) in Individuals with Depression Correlates with Severity of Disease

AIM

To assess serum Hepatocyte Growth Factor (HGF) levels in individuals with depression and to test the hypothesis that there is a relationship between severity of depression and HGF concentration.

SUBJECTS AND METHODS

Serum from 26 clinically depressed individuals and 19 controls were tested for serum HGF using ELISAs. Correlation was established between HGF concentration and disease severity.

RESULTS

Depressed individuals had significantly lower serum levels of HGF compared to controls (P < 0.0001). HGF concentration correlated with overall depressive behavior (P = 0.03) and specifically depression (P = 0.02), but not anxiety (P = 0.36).

DISCUSSION

These results suggest an association between HGF serum levels and clinically depressed individuals and demonstrate a correlation between severity of depression and HGF levels. Further studies of the predictive strength of HGF as a biomarker for depression may be warranted.

Tolfenamic acid decreases c-Met expression through Sp proteins degradation and inhibits lung cancer cells growth and tumor formation in orthotopic mice

The nonsteroidal anti-inflammatory drug (NSAID), tolfenamic acid (TA) is emerging as a new anti-cancer agent. TA induces the degradation of specific Specificity protein (Sp) transcription factors, Sp1, Sp3 and Sp4 which are associated with tumor growth and metastasis. In this study we have evaluated the effect of TA on lung cancer using both in vitro and in vivo models. TA in a dose dependent manner inhibited proliferation and cell viability of two different lung cancer cells, A549 and CRL5803. TA treatment for 48 h significantly decreased the expression of Sp1, Sp3 and Sp4. The hepatocyte growth factor receptor, c-Met is overexpressed in a variety of cancers including lung cancer and Sp proteins mediate the regulation of c-Met. TA diminished the expression of c-Met protein and modulates its downstream signaling pathway. Furthermore, TA treatment significantly increased the number of apoptotic cells and pro-apoptotic markers c-PARP and Bax confirming the activation of apoptotic pathways. In vivo studies using the orthotopic mice model for lung cancer showed that TA (25 mg/kg/2 days and 50 mg/kg/2 days) resulted in a dose dependent decrease in tumor formation. The immunohistochemical staining of lung tissue showed high expression of Sp1, Sp3, Sp4, c-Met and phospho Met in control group and a dose dependent decrease in TA treated groups. The crucial findings of this study support that targeting c-Met with a potent inhibitor of Sp proteins is a robust strategy for the implications in lung cancer treatment and TA can serve as a therapeutic agent for this devastating disease.

Zinc protoporphyrin regulates cyclin D1 expression independent of heme oxygenase inhibition

Zinc protoporphyrin IX (ZnPP), an endogenous heme analogue that inhibits heme oxygenase (HO) activity, represses tumor growth. It can also translocate into the nucleus and up-regulate heme oxygenase 1 (HMOX1) gene expression. Here, we demonstrate that tumor cell proliferation was inhibited by ZnPP, whereas tin protoporphyrin (SnPP), another equally potent HO-1 inhibitor, had no effect. Microarray analysis on 128 tumorigenesis related genes showed that ZnPP suppressed genes involved in cell proliferation and angiogenesis. Among these genes, CYCLIN D1 (CCND1) was specifically inhibited as were its mRNA and protein levels. Additionally, ZnPP inhibited CCND1 promoter activity through an Sp1 and Egr1 overlapping binding site (S/E). We confirmed that ZnPP modulated the S/E site, at least partially by associating with Sp1 and Egr1 proteins rather than direct binding to DNA targets. Furthermore, administration of ZnPP significantly inhibited cyclin D1 expression and progression of a B-cell leukemia/lymphoma 1 tumor in mice by preferentially targeting tumor cells. These observations show HO independent effects of ZnPP on cyclin D1 expression and tumorigenesis.

Changes in the proteome after neuronal zif268 overexpression

Long-lasting forms of brain plasticity are a cellular basis for long-term memory, and their disturbance underlies pathological conditions such as dementia and cognitive impairment. Neuronal plasticity is a complex process that utilizes molecular cascades in the cytoplasm and the nucleus and involves numerous transcription factors, in particular, immediate early genes (IEGs). The signaling cascades that control IEGs are fairly well described, but the downstream transcriptional response is poorly understood, especially its late components. Here, we investigated the response induced by the IEG Zif268 in the adult brain in relation to long-term memory. Using a mouse model with increased neuronal expression of Zif268 that leads to improved memory, we identified an ensemble of proteins regulated by Zif268 expression and differentiated between direct and indirect targets based on the presence of a consensus binding motif in their promoter. We show that Zif268 regulates numerous substrates with diverse biological functions including protein modification and degradation (proteasome-core complex), phosphorylation, cell division, sensory perception, metabolism, and metal ion transport. The results provide a comprehensive and quantitative data set characterizing the Zif268-dependent proteome in the adult mouse brain and offers biologically important new insight into activity-dependent pathways downstream of IEGs.

PAX6 is expressed in pancreatic cancer and actively participates in cancer progression through activation of the MET tyrosine kinase receptor gene

Tumors of the exocrine pancreas have a poor prognosis. Several proteins are overexpressed in this cancer type, including the MET tyrosine kinase receptor and the transcription factor PAX6. In this report, we find that PAX6(5a), an alternately spliced variant form of PAX6, is expressed in pancreatic carcinoma cell lines at higher levels than the canonical PAX6 protein. Both protein forms of PAX6 bind directly to an enhancer element in the MET promoter and activate the expression of the MET gene. In addition, inhibition of PAX6 transcripts leads to a decline in cell growth and survival, differentiation, and a concurrent reduction of MET protein expression. These data support a model for a neoplastic pathway, where expression of a transcription factor from development activates the MET receptor, a protein that has been directly linked to protumorigenic processes of resisting apoptosis, tumor growth, invasion, and metastasis.

Hypertension in mice lacking the CXCR3 chemokine receptor

The CXC chemokine receptor 3 (CXCR3) has been linked to autoimmune and inflammatory disease, allograft rejection, and ischemic nephropathy. CXCR3 is expressed on endothelial and smooth muscle cells. Although a recent study posited that antagonizing of CXCR3 function may reduce atherosclerosis, the role of CXCR3 in controlling physiological vascular functions remains unclear. This study demonstrates that disruption of CXCR3 leads to elevated mean arterial pressures in anesthetized and conscious mice, respectively. Stimulation of isolated resistance vessels with various vasoconstrictors showed increased contractibility in CXCR3-/- mice in response to angiotensin II (ANG II) and a decreased vasodilatation in response to acetylcholine (ACh). The increased contractibility was related to higher ANG II type 1 receptor (AT1R) expression, whereas the decreased vasodilatation was related to lower M3-ACh receptor expression in the mesenteric arteries of CXCR3-/- mice compared with wild-type mice. The vasodilatatory response to ACh could be antagonized by the nonselective ACh receptor antagonist atropine and the selective M3 receptor antagonist 4-DAMP, but not by M1, M2, and M4 receptor antagonists. Additionally, EMSA studies revealed that transcription factors SP-1 and EGR-1 interact as a complex with the murine AT1R promoter region. Furthermore, we could show increased expression of SP-1 in CXCR3-/- mice indicating an imbalanced SP-1 and EGR-1 complex formation which causes increased AT1R expression and hypertension. The data indicate that CXCR3 receptor is important in vascular contractility and hypertension, possibly through upregulated AT1R expression.

Transcriptional regulation of human protease-activated receptor 1: a role for the early growth response-1 protein in prostate cancer

Transcriptional regulation plays a central role in the molecular pathways underlying preferential cancer growth and metastasis. In the present study, we investigated the regulation of human protease-activated receptor 1 (hPar1) gene overexpression in the malignant androgen hormone-resistant phase. We found increased hPar1 RNA chain elongation and no change in message stability in cells with high levels of PAR1 expression, indicating that increased transcription is largely responsible for the overexpression of hPar1 in prostate tumor progression. Enforced expression of early growth response-1 (Egr-1) plasmid markedly enhanced luciferase activity driven by the hPar1 promoter. The neuroendocrine peptide bombesin significantly induced hPar1 expression and increased the ability of the cells to invade Matrigel, an effect abolished by expression of hPar1 small interfering RNA, showing the importance of hPAR1 in invasion. Bombesin also markedly enhanced Egr-1 binding to the hPar1 promoter in vivo and in vitro. These data suggest that bombesin enhances Egr-1 expression leading to increased hPar1 transcription, thereby increasing PAR1 expression and function. Immunohistostaining of prostate tissue biopsy specimens revealed a direct correlation between the degree of prostate cancer malignancy, PAR1 expression, and EGR-1 expression. Altogether, we show that transcriptional regulation of hPar1 in the aggressive hormone-resistant prostate cancer stage is controlled in part by the transcription factor Egr-1 and may play a central role in invasiveness, an important indicator of malignancy.

Regulation of rat dopamine beta-hydroxylase gene transcription by early growth response gene 1 (Egr1)

Egr1, a transcription factor rapidly induced by various stimuli including stress, can elevate transcription of genes for the catecholamine biosynthetic enzymes TH and PNMT. To examine if Egr1 also regulates dopamine beta-hydroxylase (DBH) gene expression, PC12 cells were transfected with expression vector for full length or truncated inactive Egr1 and various DBH promoter-driven luciferase constructs. While Egr1 elevated TH promoter activity, DBH promoter activity was reduced. The reduction occurred as early as 4 h and reached maximal inhibition 16-40 h after transfection. Egr1 also reduced the expression of endogenous DBH mRNA and the induction of DBH promoter activity by cAMP. These effects were not observed with truncated Egr1 lacking the DNA binding domain. The first 247, but not 200, nucleotides of DBH promoter are sufficient for this suppression. Several putative Egr1 motifs were identified, and mutagenesis showed that the motif at -227/-224 is required. Binding of Egr1 to this region of the DBH promoter was verified by chromatin immunoprecipitation and electrophoretic mobility shift assays. This study demonstrates that DBH promoter contains at least one functional Egr1 motif; and indicates, for the first time, that Egr1 can play an inhibitory role in regulation of DBH gene transcription.

Membrane type-1 matrix metalloproteinase is induced following cyclic compression of in vitro grown bovine chondrocytes

OBJECTIVE

To determine if membrane type-1 matrix metalloproteinase (MT1-MMP) will respond to cyclic compression of chondrocytes grown in vitro and the regulatory mechanisms underlying this response.

METHODS

Cyclic compression (30min, 1kPa, 1Hz) was applied to bovine chondrocytes (6-9-month-old animals) grown on top of a biodegradable substrate within 3 days of initiating culture. Luciferase assays using bovine articular chondrocytes were undertaken to demonstrate the mechanosensitivity of MT1-MMP. Semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) and western blot analysis were used to establish the time course of gene and protein upregulation in response to cyclic compression. The regulation of MT1-MMP was assessed by electrophoretic mobility shift assays, RT-PCR and western blot analysis. As well, an MT1-MMP decoy oligonucleotide and an extracellular signal-regulated kinase 1/2 (ERK1/2) pharmacological inhibitor were utilized to further characterize MT1-MMP regulation.

RESULTS

After cyclic compression, MT1-MMP showed a rapid and transient increase in gene expression. Elevated protein levels were detected within 2h of stimulation which returned to baseline by 6h. During cyclic compression, phosphorylation of the mitogen activated protein kinase ERK1/2 increased significantly. This was followed by increased gene and protein expression of the transcription factor; early growth factor-1 (Egr-1) and Egr-1 binding to the MT1-MMP promoter. Blocking Egr-1 DNA binding with a decoy MT1-MMP oligonucleotide, downregulated MT1-MMP gene expression. The ERK1/2 inhibitor U0126 also reduced Egr-1 DNA binding activity to MT1-MMP promoter sequences and subsequent transcription of MT1-MMP.

CONCLUSIONS

These data suggest that cyclic compression of chondrocytes in vitro upregulates MT1-MMP via ERK1/2 dependent activation of Egr-1 binding. Delineation of the regulatory pathways activated by mechanical stimulation will further our understating of the mechanisms influencing tissue remodeling.

Regulation of c-met expression by transcription repressor Daxx

The protooncogene c-met encodes the tyrosine kinase receptor for the hepatocyte growth factor/scatter factor (HGF/SF). While overexpression of c-met is documented in many types of tumors, the mechanism of c-met regulation remains elusive. Here, we demonstrate Daxx as a repressor of c-met transcription. The expression of c-met is elevated in Daxx knockout mouse cells and is reversed by Daxx reconstitution. C-met promoter analysis of Daxx-/- cells reveled changes in chromatin acetylation, but not in DNA methylation. Daxx binds to the mouse c-met promoter and Daxx-binding region is sufficient for transcription repression, while HDAC2 is associated with c-met promoter mostly in Daxx+/+ cells, pointing to Daxx-dependent HDAC2 recruitment as a potential mechanism of c-met repression. HGF-induced cell mobility and invasion confirmed augmented activity of c-Met/HGF pathway in Daxx-/- cells. Finally, inverse correlation between Daxx and c-Met in cancer cell lines and in metastatic breast cancer specimens suggests potential function of Daxx as a c-met repressor during cancer progression.

Molecular basis for the cell type specific induction of SnoN expression by hepatocyte growth factor

Hepatocyte growth factor (HGF) is a potent antifibrotic cytokine that antagonizes the TGF-beta1/Smad signaling in diverse types of kidney cells by different mechanisms. HGF is shown to induce Smad co-repressor Sloan-Kettering Institute proto-oncogene-related novel gene, non-Alu-containing (SnoN) expression in proximal tubular epithelial cells (HKC-8) but not in glomerular mesangial cells and interstitial fibroblasts. This study investigated the molecular mechanisms underlying the cell type-specific induction of SnoN by HGF. Treatment of HKC-8 cells with actinomycin D completely abolished HGF-mediated SnoN induction, suggesting its dependence on gene transcription. Although HGF activated several signal pathways in HKC-8 cells, blockade of extracellular signal-regulated kinase-1 and -2 (Erk-1/2) activation but not Akt and p38 mitogen-activated protein kinase abolished SnoN induction. HGF rapidly activated both upstream and downstream signaling of Erk-1/2, which led to the activation of the cAMP response element-binding protein (CREB). In the promoter region of human SnoN gene, two cAMP response elements were located in close proximity to Sp1 sites. Chromatin immunoprecipitation assay revealed that activated CREB and Sp1 bound to their cognate cis-acting elements in SnoN promoter in response to HGF stimulation. Ectopic expression of wild-type CREB promoted SnoN expression, whereas dominant negative mutant CREB abrogated SnoN induction by HGF. Likewise, chemical blockade of Sp1 binding abolished HGF-mediated SnoN induction. Furthermore, HGF selectively induced CREB phosphorylation in HKC-8 cells but not in mesangial cells and fibroblasts. In vivo, administration of HGF gene induced renal Erk-1/2 phosphorylation, CREB activation, and SnoN expression in obstructive nephropathy. Collectively, these results suggest that CREB activation, in concert with Sp1, constitutes a molecular switch that confers the cell type-specific induction of SnoN in response to HGF stimulation.

Regulation of neuronal cdc20 (p55cdc) expression by the plasticity-related transcription factor zif268

Most forms of neuronal plasticity are associated with induction of the transcription factor zif268 (egr1). Down-regulation of cdc20 (p55(cdc))--a regulatory protein for the anaphase-promoting complex, which controls access of specific substrates to the proteasome--was observed after transfection of a neuronal cell line with zif268. Treatment of cultured hippocampal neurones with NMDA, which elevates endogenous zif268 levels, also decreased cdc20 levels. Conversely, the levels of cdc20 were found to be increased in the cerebral cortex of mice with targeted deletion of the zif268 gene, when compared with wild-type controls. Our findings indicate that expression of the cdc20 gene is down-regulated by zif268 in neuronal cells, and provide new evidence that altered expression of proteasome-regulatory genes following zif268 induction may be a key component of long-lasting CNS plasticity.

Structure of the human 5-HT7 receptor gene and characterization of its promoter region

The molecular mechanism regulating serotonin 5-HT(7) receptor expression is still unclear. In this study we provide evidence that transcription of the 5-HT(7) gene is at least partly regulated by Sp1 and Sp3. We isolated and sequenced >3000 bp of the upstream sequences and identified by RACE a number of transcriptional initiation sites over a region of 300 bp upstream of the coding region. This region has a high GC content, but contains no obvious TATA or a CAAT box. Besides a Sp1/Sp3 consensus motif, regulatory elements for AP2, Egr-1 and MAZ are also present. Transient transfection assays using deletion variants indicated that the GC-rich region is essential for full promoter activity. The role of Sp1 in this was confirmed by transient overexpression of both wild type Sp1 or dominant-negative forms. By gel shift and supershift analyses, targeting the Sp1 consensus sequence and the GC-rich region just upstream of the transcription initiation sites, binding of Sp1 and Sp3 was demonstrated. Both in vitro as well as in vivo experiments, using a cell line which endogenously expresses the 5-HT(7) receptor, indicated that mithramycin A, an inhibitor of Sp1/3 transcription factor binding, was able to inhibit 5-HT(7) promoter activity. Taken together these results support the essential role of Sp factors in regulating 5-HT(7) promoter activity.

Transcriptional signatures of cellular plasticity in mice lacking the alpha1 subunit of GABAA receptors

GABAA receptors mediate the majority of inhibitory neurotransmission in the CNS. Genetic deletion of the alpha1 subunit of GABAA receptors results in a loss of alpha1-mediated fast inhibitory currents and a marked reduction in density of GABAA receptors. A grossly normal phenotype of alpha1-deficient mice suggests the presence of neuronal adaptation to these drastic changes at the GABA synapse. We used cDNA microarrays to identify transcriptional fingerprints of cellular plasticity in response to altered GABAergic inhibition in the cerebral cortex and cerebellum of alpha1 mutants. In silico analysis of 982 mutation-regulated transcripts highlighted genes and functional groups involved in regulation of neuronal excitability and synaptic transmission, suggesting an adaptive response of the brain to an altered inhibitory tone. Public gene expression databases permitted identification of subsets of transcripts enriched in excitatory and inhibitory neurons as well as some glial cells, providing evidence for cellular plasticity in individual cell types. Additional analysis linked some transcriptional changes to cellular phenotypes observed in the knock-out mice and suggested several genes, such as the early growth response 1 (Egr1), small GTP binding protein Rac1 (Rac1), neurogranin (Nrgn), sodium channel beta4 subunit (Scn4b), and potassium voltage-gated Kv4.2 channel (Kcnd2) as cell type-specific markers of neuronal plasticity. Furthermore, transcriptional activation of genes enriched in Bergman glia suggests an active role of these astrocytes in synaptic plasticity. Overall, our results suggest that the loss of alpha1-mediated fast inhibition produces diverse transcriptional responses that act to regulate neuronal excitability of individual neurons and stabilize neuronal networks, which may account for the lack of severe abnormalities in alpha1 null mutants.

Regulation of the neuronal proteasome by Zif268 (Egr1)

Most forms of neuronal plasticity are associated with induction of the transcription factor Zif268 (Egr1/Krox24/NGF-IA). In a genome-wide scan, we obtained evidence for potential modulation of proteasome subunit and regulatory genes by Zif268 in neurons, a finding of significance considering emerging evidence that the proteasome modulates synaptic function. Bioinformatic analysis indicated that the candidate proteasome Zif268 target genes had a rich concentration of putative Zif268 binding sites immediately upstream of the transcriptional start sites. Regulation of the mRNAs encoding the psmb9 (Lmp2) and psme2 (PA28beta) proteasome subunits, along with the proteasome-regulatory kinase serum/glucocorticoid-regulated kinase (SGK) and the proteasome-associated antigen peptide transporter subunit 1 (Tap1), was confirmed after transfection of a neuronal cell line with Zif268. Conversely, these mRNAs were upregulated in cerebral cortex tissue from Zif268 knock-out mice relative to controls, confirming that Zif268 suppresses their expression in the CNS. Transfected Zif268 reduced the activity of psmb9, SGK, and Tap1 promoter-reporter constructs. Altered psmb9, SGK, and Tap1 mRNA levels were also observed in an in vivo model of neuronal plasticity involving Zif268 induction: the effect of haloperidol administration on striatal gene expression. Consistent with these effects on proteasome gene expression, increased Zif268 expression suppressed proteasome activity, whereas Zif268 knock-out mice exhibited elevated cortical proteasome activity. Our findings reveal that Zif268 regulates the expression of proteasome and related genes in neuronal cells and provide new evidence that altered expression of proteasome activity after Zif268 induction may be a key component of long-lasting CNS plasticity.

Early growth response-1 in cardiovascular pathobiology

The immediate-early gene product and zinc finger transcription factor early growth response (Egr)-1 plays a key master regulatory role in multiple cardiovascular pathological processes. This article reviews the amazing recent evidence implicating Egr-1 in atherosclerosis, intimal thickening after acute vascular injury, ischemic pathology, angiogenesis, allograft rejection, and cardiac hypertrophy.

Catalase deficiency renders remnant kidneys more susceptible to oxidant tissue injury and renal fibrosis in mice

BACKGROUND

Catalase is one of the important antioxidant enzymes regulating the levels of intracellular hydrogen peroxide and hydroxyl radical. The effect of catalase deficiency on progressive renal fibrosis has not been fully elucidated.

METHODS

Homozygous acatalasemic mutant mice (C3H/AnLCs(b)Cs(b)) and control wild-type mice (C3H/AnLCs(a)Cs(a)) were subjected to 5/6 nephrectomy. The functional and morphological alterations of the remnant kidneys, including tubulointerstitial fibrosis, epithelial to mesenchymal transition (EMT), peroxidation, antioxidant enzyme activity, and gene expression of EMT-related molecules were compared between the two groups at 6, 12, and 18 weeks after 5/6 nephrectomy.

RESULTS

The 5/6 nephrectomy resulted in albuminuria, decreased renal function, and tubulointerstitial fibrosis with accumulation of type I and type IV collagens in the remnant kidneys of both mouse groups. However, the degree of these changes was significantly higher in acatalasemic mice after 5/6 nephrectomy as compared with wild-type mice until week 18. EMT, a crucial phenotypic alteration of tubular epithelial cells, was observed in acatalasemic mice by electron microscopy and was associated with upregulation of EMT-related alpha-smooth muscle actin (alpha-SMA), transforming growth factor-beta1 (TGF-beta1), connective tissue growth factor (CTGF), and fibroblast specific protein-1 (FSP-1) gene expression. Significant increases in the tubulointerstitial deposition of lipid peroxidation products, including 4-hydroxy-2-nonenal and urinary excretion of 8-hydroxy-2'- deoxyguanosine were observed in the acatalasemic mice after 5/6 nephrectomy as compared with the wild-type mice. Glomerular sclerosis developed after tubulointerstitial injury in acatalasemic mice. The level of catalase activity remained low in the remnant kidneys of acatalasemic mice until week 18 without compensatory up-regulation of glutathione peroxidase or superoxide dismutase (SOD) activity. Finally, supplementation of a SOD mimetic tempol did not prevent peroxidation and tubulointerstitial fibrosis in the acatalasemic remnant kidneys.

CONCLUSION

These findings indicate that acatalasemia exacerbates renal oxidant tissue injury and sensitizes remnant kidneys to EMT and progressive renal fibrosis. This study suggests a central role for catalase in the defense against oxidant-mediated renal fibrosis.

Bombesin regulates cyclin D1 expression through the early growth response protein Egr-1 in prostate cancer cells

Our previous studies indicate that the activation of mitogen-activated protein kinase (MAPK) pathway is involved in bombesin-induced cell proliferation in prostate cancer cells. Cyclin D1 is a critical regulator involved in cell cycle progression through the G1 phase into the S phase, thereby contributing to cell proliferation. Mostly, mitogen-stimulated expression of cyclin D1 is attributed to the extracellular signal-regulated kinase (ERK) activation. Here, we found that bombesin induced human cyclin D1 expression on both mRNA and protein levels in DU-145 prostate cancer cells. Mutational analyses showed that bombesin-enhanced cyclin D1 transcription required the binding of nuclear proteins to the -143 to -105 region of the human cyclin D1 promoter, which contains binding sites for transcription factors Sp-1 and early growth response protein (Egr-1). Do novo protein synthesis was requisite for bombesin-induced cyclin D1 expression. Further studies showed Egr-1 was induced upon bombesin stimulation. The induction of Egr-1 expression and its binding to the cyclin D1 promoter were essential for bombesin-enhanced cyclin D1 transcription. Inhibition of MAPK pathway with either the MEK1 inhibitor PD98059 or a dominant-negative Ras mutant, RasN17, abolished bombesin-induced cyclin D1 activation. Taken together, bombesin-induced cyclin D1 expression in prostate cancer cells is mediated by Egr-1 activation and the interaction of Egr-1 with the Egr-1/Sp1 motif of the cyclin D1 promoter through the activation of MAPK pathway. These findings represent a novel mechanism of bombesin-dependent stimulation of mitogenesis by regulating directly the cell cycle in prostate cancer.

Genomic profiling of the neuronal target genes of the plasticity-related transcription factor -- Zif268

The later phases of neuronal plasticity are invariably dependent on gene transcription. Induction of the transcription factor Zif268 (Egr-1) in neurones is closely associated with many forms of functional plasticity, yet the neuronal target genes modulated by Zif268 have not been characterized. After transfection of a neuronal cell line with Zif268 we identified genes that show altered expression using high density microarrays. Although some of the genes identified have previously been associated with forms of neuronal plasticity, the majority have not been linked with neuronal plasticity or Zif268 action. Altered expression of a representative sample of the novel target genes was confirmed in Zif268-transfected PC12 neurones, and in in vitro and in vivo models of Zif268-associated neuronal plasticity. In particular, altered expression of the protease inhibitor Cystatin C and the chemokine Cxcl10 was observed in striatal tissue after haloperidol administration. Surprisingly, the group of identified genes is enriched for components of the proteasome and the major histocompatibility complex. Our findings suggest that altered expression of these genes following Zif268 induction may be a key component of long lasting plasticity in the CNS.

Role of receptor for advanced glycation end-products and signalling events in advanced glycation end-product-induced monocyte chemoattractant protein-1 expression in differentiated mouse podocytes

BACKGROUND

Upregulation of local monocyte chemoattractant protein-1 (MCP-1) production is involved in glomerular damage through macrophage recruitment and activation in diabetic nephropathy. Treatment of db/db mice with soluble receptor for advanced glycation end-products (RAGE) prevented recruitment of macrophages to the glomeruli and reduced albuminuria, suggesting that binding of ligands and RAGE may be involved in MCP-1 expression. Therefore, we investigated the role of advanced glycation end-products (AGEs) in MCP-1 production by podocytes and signalling events after RAGE activation.

METHODS

MCP-1 gene and protein expression were examined by using reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay in differentiated mouse podocytes. Dichlorofluorescein-sensitive intracellular reactive oxygen species (ROS) generation was measured by confocal microscopy. RAGE, phosphorylation of mitogen-activated protein kinases, nuclear factor (NF)-kappaB, c-Jun and Sp1 were studied using western blotting and immunocytochemistry.

RESULTS

Both differentiated and undifferentiated podocytes expressed RAGE. MCP-1 was induced by AGEs and carboxymethyllysine (CML) in a time-dependent and dose-dependent manner in differentiated podocytes. Neutralizing antibody for RAGE suppressed AGE- and CML-induced MCP-1 production. AGEs and CML rapidly generated intracellular ROS in podocytes. Blocking of ROS by using N-acetyl-l-cysteine abolished CML and H(2)O(2)-induced MCP-1 expression. Phosphorylated extracellular signal-regulated kinase (ERK) was found in podocytes incubated with CML and was prevented by N-acetyl-l-cysteine or 7'-amino 4 [trifluoromethyl]. PD98059, an inhibitor of ERK, partially prevented CML-induced MCP-1 gene expression. NF-kappaB and Sp1 were translocated into the nucleus after podocytes were incubated with CML for 60 min. Parthenolide and mithramycin A, inhibitors of NF-kappaB and Sp1, respectively, abolished CML-induced MCP-1 gene expression in a dose-dependent manner.

CONCLUSIONS

These results suggest that AGEs and CML induce MCP-1 expression in podocytes through activation of RAGE and generation of intracellular ROS. NF-kappaB and Sp1 regulate MCP-1 gene transcription.

Carvedilol effectively blocks oxidative stress-mediated downregulation of sarcoplasmic reticulum Ca2+-ATPase 2 gene transcription through modification of Sp1 binding

Carvedilol is a beta-adrenoceptor blocker and a potent antioxidant that improves cardiac function in patients with heart failure. The restoration of sarcoplasmic reticulum Ca2+-ATPase (SERCA2) gene expression may be an underlying mechanism of its beneficial effects on cardiac function. In primary cultured neonatal rat cardiac myocytes, treatment with either carvedilol or its beta-receptor inactive metabolite, BM910228, attenuated the hydrogen peroxide-mediated decrease in SERCA2 mRNA and protein levels, while metoprolol, a pure beta-blocker, had no effect. Moreover, carvedilol itself significantly enhanced SERCA2 gene transcription, suggesting that carvedilol specifically restores SERCA2 gene transcription. Site-directed mutagenesis revealed that two Sp1 sites in the SERCA2 gene promoter region mediated the response to carvedilol under oxidative stress. Further, electrophoretic mobility shift assays revealed that Sp1 and Sp3 transcription factors correlated with carvedilol-mediated changes in the promoter assays. These studies may provide a mechanistic explanation for the beneficial effects of carvedilol in heart failure.

Both Sp1 and Smad participate in mediating TGF-β1-induced HGF receptor expression in renal epithelial cells

Hepatocyte growth factor (HGF) receptor is a transmembrane receptor tyrosine kinase encoded by the c-met protooncogene. In this study, we demonstrated that c-met expression was upregulated in the kidney after obstructive injury in mice. Because the pattern of c-met induction was closely correlated with transforming growth factor-β1 (TGF-β1) expression in vivo, we further investigated the regulation of c-met expression in renal tubular epithelial (HKC) cells by TGF-β1 in vitro. Real-time RT-PCR and Northern and Western blot analyses revealed that TGF-β1 significantly induced c-met expression in HKC cells, which primarily took place at the gene transcriptional level. Overexpression of inhibitory Smad7 completely abolished c-met induction, indicating its dependence on Smad signaling. Interestingly, TGF-β1-induced c-met expression was also contingent on a functional Sp1, as ablation of Sp1 binding with mithramycin A abrogated c-met induction in HKC cells. Transfection and sequence analysis identified a cis-acting TGF-β1-responsive region in the c-met promoter, in which resided a putative Smad-binding element (SBE) and an adjacent Sp1 site. TGF-β1 not only induced Smad binding to the SBE/Sp1 sites in the c-met promoter, but also enhanced the binding of Sp proteins. Furthermore, Sp1 could form a complex with Smads in a TGF-β1-dependent fashion. These results suggest a novel regulatory mechanism controlling c-met expression by TGF-β1 in renal epithelial cells, in which both Smad and Sp proteins participate and cooperate in activating c-met gene transcription.

Hepatocyte growth factor in kidney fibrosis: therapeutic potential and mechanisms of action

Hepatocyte growth factor (HGF) is a pleiotropic factor that plays an imperative role in tubular repair and regeneration after acute renal injury. Growing evidence indicates that HGF is also an endogenous renoprotective factor that possesses a potent antifibrotic ability. HGF prevents the initiation and progression of chronic renal fibrosis and inhibits transforming growth factor (TGF)-beta(1) expression in a wide variety of animal models. In vitro, HGF counteracts the action of TGF-beta(1) in different types of kidney cells, resulting in blockade of the myofibroblastic activation from interstitial fibroblasts and glomerular mesangial cells, as well as inhibition of the mesenchymal transition from tubular epithelial cells. Recent studies reveal that HGF antagonizes the profibrotic actions of TGF-beta(1) by intercepting Smad signal transduction through diverse mechanisms. In interstitial fibroblasts, HGF blocks activated Smad-2/3 nuclear translocation, whereas it specifically upregulates the expression of the Smad transcriptional corepressor SnoN in tubular epithelial cells. In glomerular mesangial cells, HGF stabilizes another Smad corepressor, TGIF, by preventing it from degradation. Smad corepressors bind to activated Smad-2/3 and sequester their ability to transcriptionally activate TGF-beta target genes. This article reviews recent advances in our understanding of the cellular and molecular mechanisms underlying HGF inhibition of renal fibrosis.