Specific protein-1 is a universal regulator of UDP-glucose dehydrogenase expression: its positive involvement in transforming growth factor-beta signaling and inhibition in hypoxia

Mechanisms of coordinating hyaluronan and glycosaminoglycan production by nucleotide sugars

Hyaluronan is a versatile macromolecule capable of an exceptional range of functions from cushioning and hydration to dynamic signaling in development and disease. Because of its critical roles, hyaluronan production is regulated at multiple levels including epigenetic, transcriptional, and post-translational control of the three hyaluronan synthase (HAS) enzymes. Precursor availability can dictate the rate and amount of hyaluronan synthesized and shed by the cells producing it. However, the nucleotide-activated sugar substrates for hyaluronan synthesis by HAS also participate in exquisitely fine tuned cross talking pathways that intersect with central carbohydrate metabolism. Multiple UDP-sugars have alternative metabolic fates and exhibit coordinated and reciprocal allosteric control of enzymes within their biosynthetic pathways to preserve appropriate precursor ratios for accurate partitioning among downstream products, while also sensing and maintaining energy homeostasis. Since the dysregulation of nucleotide sugar and hyaluronan synthesis is associated with multiple pathologies, these pathways offer opportunities for therapeutic intervention. Recent structures of several key rate-limiting enzymes in the UDP-sugar synthesis pathways have offered new insights to the overall regulation of hyaluronan production by precursor fate decisions. The details of UDP-sugar control and the structural basis for underlying mechanisms are discussed in this review.

UDP-glucose dehydrogenase expression is upregulated following EMT and differentially affects intracellular glycerophosphocholine and acetylaspartate levels in breast mesenchymal cell lines

Metabolic rewiring is one of the indispensable drivers of epithelial-mesenchymal transition (EMT) involved in breast cancer metastasis. In this study, we explored the metabolic changes during spontaneous EMT in three separately established breast EMT cell models using a proteomics approach supported by metabolomic analysis. We identified common proteomic changes, including in the expression of CDH1, CDH2, VIM, LGALS1, SERPINE1, PKP3, ATP2A2, JUP, MTCH2, RPL26L1 and PLOD2. Consistently altered metabolic enzymes included: FDFT1, SORD, TSTA3 and UDP-glucose dehydrogenase (UGDH). Of these, UGDH was most prominently altered and has previously been associated with breast cancer patient survival. siRNA-mediated knockdown of UGDH resulted in delayed cell proliferation and dampened invasive potential of mesenchymal cells, and downregulated expression of the EMT transcription factor SNAI1. Metabolomic analysis revealed that siRNA-mediated knockdown of UGDH decreased intracellular glycerophosphocholine (GPC), whereas levels of acetylaspartate (NAA) increased. Finally, our data suggested that platelet-derived growth factor receptor beta (PDGFRB) signaling was activated in mesenchymal cells. siRNA-mediated knockdown of PDGFRB downregulated UGDH expression, potentially via NFkB-p65. Our results support an unexplored relationship between UGDH and GPC, both of which have previously been independently associated with breast cancer progression.

GR/Sp3/HDAC1/UGDH signaling participated in the maternal dexamethasone-induced dysplasia of the rat fetal growth plate

Maternal dexamethasone decreases the body length of the newborn. However, whether dexamethasone inhibits the development of the growth plate of the fetal long bone is still unknown. Here, we found that lengths of fetal femur and growth plate were both shorter in the fetuses with maternal dexamethasone (0.2 mg/kg.d from gestation day 9 to 20), with a decreased proteoglycan content of the growth plate in the fetal rat. Notable decreases in both the gene expression and H3K9 acetylation of UDP-glucose dehydrogenase (Ugdh) gene, which codes a key enzyme in the proteoglycan biosynthesis in the chondrocyte, were also observed. Meanwhile, up-regulation of glucocorticoid receptor (GR), specific protein 3 (Sp3), and histone deacetylase 1 (Hdac1) gene expression were detected in the fetal growth plate. Similar changes were also observed in the chondrogenic rat bone marrow stromal cells (BMSCs) with excessive exogenous dexamethasone. However, antagonizing GR with RU486 and silencing Hdac1 or Sp3 with specific siRNAs could all stimulate the H3K9 acetylation and gene expression of Ugdh previously inhibited by dexamethasone. Meanwhile, dexamethasone also induced the nuclear translocation of GR, which further directly bound to the Ugdh promoter and interacted with HDAC1 and Sp3, respectively. Collectively, our study revealed that maternal dexamethasone induced the direct binding of GR to the Ugdh promoter of the chondrocyte in the rat fetal growth plate, which recruited HDAC1 and Sp3, induced deacetylation of the H3K9, and subsequently inhibited Ugdh gene expression. Such changes further led to attenuated proteoglycan synthesis in the developing chondrocyte and therefore disrupted the development of growth plate and fetal long bone.

Integration of Sugar Metabolism and Proteoglycan Synthesis by UDP-glucose Dehydrogenase

Regulation of proteoglycan and glycosaminoglycan synthesis is critical throughout development, and to maintain normal adult functions in wound healing and the immune system, among others. It has become increasingly clear that these processes are also under tight metabolic control and that availability of carbohydrate and amino acid metabolite precursors has a role in the control of proteoglycan and glycosaminoglycan turnover. The enzyme uridine diphosphate (UDP)-glucose dehydrogenase (UGDH) produces UDP-glucuronate, an essential precursor for new glycosaminoglycan synthesis that is tightly controlled at multiple levels. Here, we review the cellular mechanisms that regulate UGDH expression, discuss the structural features of the enzyme, and use the structures to provide a context for recent studies that link post-translational modifications and allosteric modulators of UGDH to its function in downstream pathways.

Clinicopathological and prognostic significance of nuclear UGDH localization in lung adenocarcinoma

This study aimed to clarify relationships among UDP-glucose-6 dehydrogenase (UGDH) expression, clinicopathological factors, and the prognosis of patients, and to determine the role of UGDH in lung adenocarcinoma (AC). Firstly, UGDH expression and localization in 126 lung AC tissues were immunohistochemically studied, and associations with clinicopathological parameters and patients' prognosis were evaluated. Secondly, serum UGDH levels were measured in 267 lung cancer patients and 100 healthy controls. Finally, the effects of UGDH knockdown by siRNA on migration and invasion abilities were analyzed. As a result, nuclear UGDH staining was significantly correlated with poorer differentiation, a larger tumor size, higher p-TNM stage, positive nodal metastasis, positive lymphatic invasion, and positive vascular invasion in lung AC patients. Nuclear UGDH-positive patients showed significantly poorer survival than nuclear UGDH-negative patients. Serum UGDH levels were especially higher in lung AC patients even in stage I than those in healthy controls. In lung AC cell lines, nuclear expression levels of UGDH were higher in LC-2/ad cells than in A549 cells. UGDH siRNA-treated LC-2/ad cells showed significantly decreased migration and invasion abilities, but no significant differences were observed in UGDH siRNA-treated A549 cells. These data indicate that UGDH expression and localization are an early sero-diagnostic marker in addition to a poor prognostic indicator in lung AC patients.

Genetic variants in 5p13.2 and 7q21.1 are associated with treatment for benign prostatic hyperplasia with the α-adrenergic receptor antagonist

BACKGROUND

The etiology of benign prostatic hyperplasia (BPH) has not been well established. The preferred medical treatment for many men with symptomatic benign prostatic hyperplasia is either an α-adrenergic receptor antagonist (α-blocker), or a 5α-reductase inhibitor. Single nucleotide polymorphism (SNP) is a powerful tool for successful implementation of individualized treatment.

METHODS

Eighteen SNPs associated with drug efficacy in a Chinese population were genotyped in 790 BPH cases (330 aggressive and 460 non-aggressive BPH cases) and 1008 controls. All BPH patients were treated with α-adrenergic blockers for at least 9 months. We tested the associations between tagging single nucleotide polymorphism and BPH risk/aggressiveness, clinical characteristics at baseline, including the International Prostate Symptom Score (IPSS) and total prostate volume, and changes in clinical characteristics after treatment.

RESULTS

There were nine SNPs associated with BPH risk, clinical progression and therapeutic effect. (1) There were nine tSNPs been chosen in CYP3A4, CYP3A5 and RANBP3L genes. (2) The SNP, rs16902947 in RANBP3L at 5p13.2 (p = .01), was significantly associated with BPH. (3) We found two SNPs, rs16902947 in RANBP3L at 5p13.2 (p = .0388) and rs4646437 in CYP3A4 at 7q21.1 (p = .0325), associated with drug effect. (4) Allele "G" for rs16902947 was found to be risk alleles for BPH risk (OR= 2.357, 95%CI 1.01-1.48). The "A" allele of rs4646437 was associated with lower IPSS at baseline (β= -0.4232, p= .03255).

CONCLUSIONS

rs16902947, rs16902947 and rs4646437 single nucleotide polymorphisms are significantly associated with the clinical characteristics of benign prostatic hyperplasia and the efficacy of benign prostatic hyperplasia treatment.

Molecular mechanism of monoamine oxidase A gene regulation under inflammation and ischemia-like conditions: key roles of the transcription factors GATA2, Sp1 and TBP

Monoamine oxidase A (MAOA) plays important roles in the pathogenesis of several neurological and cardiovascular disorders. The mechanism of transcriptional regulation of MAOA under basal and pathological conditions, however, remains incompletely understood. Here, we report systematic identification and characterization of cis elements and transcription factors that govern the expression of MAOA gene. Extensive computational analysis of MAOA promoter, followed by 5'-promoter deletion/reporter assays, revealed that the -71/-40 bp domain was sufficient for its basal transcription. Gel-shift and chromatin immunoprecipitation assays provided evidence of interactions of the transcription factors GATA-binding protein 2 (GATA2), Sp1 and TATA-binding protein (TBP) with this proximal promoter region. Consistently, over-expression of GATA2, Sp1 and TBP augmented MAOA promoter activity in a coordinated manner. In corroboration, siRNA-mediated down-regulation of GATA2/Sp1/TBP repressed the endogenous MAOA expression as well as transfected MAOA promoter activity. Tumor necrosis factor-α and forskolin activated MAOA transcription that was reversed by Sp1 siRNA; in support, tumor necrosis factor-α- and forskolin-induced activities were enhanced by ectopic over-expression of Sp1. On the other hand, MAOA transcription was diminished upon exposure of neuroblasts or cardiac myoblasts to ischemia-like conditions because of reduced binding of GATA2/Sp1/TBP with MAOA promoter. In conclusion, this study revealed previously unknown roles of GATA2, Sp1 and TBP in modulating MAOA expression under basal as well as pathophysiological conditions such as inflammation and ischemia, thus providing new insights into the molecular basis of aberrant MAOA expression in neuronal/cardiovascular disease states. Dysregulation of monoamine oxidase A (MAOA) have been implicated in several behavioral and neuronal disease states. Here, we identified three crucial transcription factors (GATA2, Sp1 and TBP) that regulate MAOA gene expression in a coordinated manner. Aberrant MAOA expression under pathophysiological conditions including inflammation and ischemia is mediated by altered binding of GATA2/Sp1/TBP with MAOA proximal promoter. Thus, these findings provide new insights into pathogenesis of several common diseases. GATA2, GATA-binding protein 2; Sp1, specificity protein 1; TBP, TATA-binding protein.

UDP-glucose dehydrogenase modulates proteoglycan synthesis in articular chondrocytes: its possible involvement and regulation in osteoarthritis

Introduction

The objective of this study was to investigate the possible role of UDP-glucose dehydrogenase (UGDH) in osteoarthritis (OA) and uncover whether, furthermore how interleukin-1beta (IL-1β) affects UGDH gene expression.

Methods

UGDH specific siRNAs were applied to determine the role of UGDH in proteoglycan (PG) synthesis in human articular chondrocytes. Protein levels of UGDH and Sp1 in human and rat OA cartilage were detected. Then, human primary chondrocytes were treated with IL-1β to find out whether and how IL-1β could regulate the gene expression of UGDH and its trans-regulators, that is Sp1, Sp3 and c-Krox. Finally, p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 and stress-activated protein kinase/c-Jun N-terminal kinase (SAP/JNK) inhibitor SP600125 were used to pick out the pathway that mediated the IL-1β-modulated PGs synthesis and gene expression of UGDH, Sp1, Sp3 and c-Krox.

Results

UGDH specific siRNAs markedly inhibited UGDH mRNA and protein expression, and thus led to an obvious suppression of PGs synthesis in human articular chondrocytes. UGDH protein level in human and rat OA cartilage were much lower than the corresponding controls and negatively correlated to the degree of OA. Decrease in Sp1 protein level was also observed in human and rat OA cartilage respectively. Meanwhile, IL-1β suppressed UGDH gene expression in human articular chondrocytes in the late phase, which also modulated gene expression of Sp1, Sp3 and c-Krox and increased both Sp3/Sp1 and c-Krox/Sp1 ratio. Moreover, the inhibition of SAP/JNK and p38 MAPK pathways both resulted in an obvious attenuation of the IL-1β-induced suppression on the UGDH gene expression.

Conclusions

UGDH is essential in the PGs synthesis of articular chondrocytes, while the suppressed expression of UGDH might probably be involved in advanced OA, partly due to the modulation of p38 MAPK and SAP/JNK pathways and its trans-regulators by IL-1β.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0484-2) contains supplementary material, which is available to authorized users.

Cancer may be a pathway to cell survival under persistent hypoxia and elevated ROS: a model for solid-cancer initiation and early development

A number of proposals have been made in the past century regarding what may drive sporadic cancers to initiate and develop. Yet the problem remains largely unsolved as none of the proposals have been widely accepted as cancer-initiation drivers. We propose here a driver model for the initiation and early development of solid cancers associated with inflammation-induced chronic hypoxia and reactive oxygen species (ROS) accumulation. The model consists of five key elements: (i)human cells tend to have a substantial gap between ATP demand and supply during chronic hypoxia, which would inevitably lead to increased uptake of glucose and accumulation of its metabolites; (ii) the accumulation of these metabolites will cast mounting pressure on the cells and ultimately result in the production and export of hyaluronic acid; (iii) the exported hyaluronic acid will be degraded into fragments of various sizes, serving as tissue-repair signals, including signals for cell proliferation, cell survival and angiogenesis, which lead to the initial proliferation of the underlying cells; (iv) cell division provides an exit for the accumulated glucose metabolites using them towards macromolecular synthesis for the new cell, and hence alleviate the pressure from the metabolite accumulation; and (v) this process continues as long as the hypoxic condition persists. In tandem, genetic mutations may be selected to make cell divisions and hence survival more sustainable and efficient, also increasingly more uncontrollable. This model also applies to some hereditary cancers as their key mutations, such as BRCA for breast cancer, generally lead to increased ROS and ultimately to repression of mitochondrial activities and up-regulation of glycolysis, as well as hypoxia; hence the energy gap, glucose-metabolite accumulation, hyaluronic acid production and continuous cell division for survival.

First identification and functional analysis of the human xylosyltransferase II promoter

Recently, we demonstrated that the human xylosyltransferase II (XT-II) has enzymatic activity and is able to catalyze the initial and rate-limiting step in the biosynthesis of glycosaminoglycans (GAGs) like chondroitin and dermatan sulfate, as well as heparan sulfate and heparin. Therefore, this enzyme also very likely assumes a crucial regulatory role in the biosynthesis of proteoglycans (PGs). In this study, we identified and characterized for the first time the XYLT2 gene promoter region and transcription factors involved in its regulation. Several binding sites for members of the Sp1 family of transcription factors were identified as being necessary for transcriptional regulation of the XYLT2 gene. This was determined by mithramycin A treatment, electrophoretic mobility shift and supershift assays, as well as numerous site-directed mutagenesis experiments. Different 5' and 3' deletion constructs of the predicted GC rich promoter region, which lacks a canonical TATA and CAAT box, revealed that a 177 nts proximal promoter element is sufficient and indispensable to drive the constitutive transcription in full strength in HepG2 hepatoma cells. In addition, we also detected the transcriptional start site using 5'-RACE (rapid amplification of cDNA ends). Our results provide an insight into transcriptional regulation of the XYLT2 gene and may contribute to understanding the manifold GAG-involving processes in health and disease.

Regulation of xylosyltransferase I gene expression by interleukin 1β in human primary chondrocyte cells: mechanism and impact on proteoglycan synthesis

Xylosyltransferase I (XT-I) is an essential enzyme of proteoglycan (PG) biosynthesis pathway catalyzing the initial and rate-limiting step in glycosaminoglycan chain assembly. It plays a critical role in the regulation of PG synthesis in cartilage; however, little is known about underlying mechanism. Here, we provide evidence that, in human primary chondrocytes, IL-1β regulates XT-I gene expression into an early phase of induction and a late phase of down-regulation. Based on promoter deletions, the region up to -850 bp was defined as a major element of XT-I gene displaying both constitutive and IL-1β-regulated promoter activity. Point mutation and signaling analyses revealed that IL-1β-induced promoter activity is achieved through AP-1 response elements and mediated by SAP/JNK and p38 signaling pathways. Transactivation and chromatin immunoprecipitation assays indicated that AP-1 is a potent transactivator of XT-I promoter and that IL-1β-induced activity is mediated through increased recruitment of AP-1 to the promoter. Finally, we show that Sp3 is a repressor of XT-I promoter and bring evidence that the repressive effect of IL-1β during the late phase is mediated through Sp3 recruitment to the promoter. This suggests that modulation of Sp3 in cartilage could prevent IL-1β inhibition of PG synthesis and limit tissue degradation.

Impact of four loci on serum tamsulosin hydrochloride concentration

Tamsulosin hydrochloride is one of the most potent drugs for treatment of benign prostatic hyperplasia (BPH), however, the efficacy of tamsulosin hydrochloride varies among individuals. In this study, we measured the maximum serum concentration (Cmax) of tamsulosin hydrochloride in 182 of BPH patients and found remarkable individual variability. To investigate the genetic factors that regulate pharmacokinetics of tamsulosin hydrochloride, we conducted a genome-wide association study in these 182 BPH patients. As a result, rs16902947 on chromosome 5p13.2, rs7779057 on 7q22.3, rs35681285 on 7p21.2 and rs2122469 on 8p21.3 indicated possible associations with Cmax of tamsulosin hydrochloride (P=1.29 × 10(-7), 2.15 × 10(-7), 4.35 × 10(-7) and 7.03 × 10(-7), respectively), although these single-nucleotide polymorphisms (SNPs) did not reach the genome-wide significance threshold after Bonferroni correction. As these associated SNPs showed additive effects on serum tamsulosin hydrochloride concentration, we defined the 'Cmax prediction index' based on genotypes of these SNPs. This index clearly associated with Cmax values (P=4.5 × 10(-6)), indicating the possible roles of these four variants in tamsulosin hydrochloride pharmacokinetics. Our findings would partially explain the variability of the response to the tamsulosin hydrochloride treatment.

Proteomics analyses of human optic nerve head astrocytes following biomechanical strain

We investigate the role of glial cell activation in the human optic nerve caused by raised intraocular pressure, and their potential role in the development of glaucomatous optic neuropathy. To do this we present a proteomics study of the response of cultured, optic nerve head astrocytes to biomechanical strain, the magnitude and mode of strain based on previously published quantitative models. In this case, astrocytes were subjected to 3 and 12% stretches for either 2 h or 24 h. Proteomic methods included nano-liquid chromatography, tandem mass spectrometry, and iTRAQ labeling. Using controls for both stretch and time, a six-plex iTRAQ liquid chromatography- tandem MS (LC/MS/MS) experiment yielded 573 proteins discovered at a 95% confidence limit. The pathways included transforming growth factor β1, tumor necrosis factor, caspase 3, and tumor protein p53, which have all been implicated in the activation of astrocytes and are believed to play a role in the development of glaucomatous optic neuropathy. Confirmation of the iTRAQ analysis was performed by Western blotting of various proteins of interest including ANXA 4, GOLGA2, and αB-Crystallin.

Divergent Sp1 protein levels may underlie differential expression of UDP-glucose dehydrogenase by fibroblasts: role in susceptibility to orbital Graves disease

UDP-glucose dehydrogenase (UGDH) catalyzes the formation of UDP-glucuronate. Glucuronate represents an integral component of the glycosaminoglycan, hyaluronan, which accumulates in orbital Graves disease. Here we report that orbital fibroblasts express higher levels of UGDH than do those from skin. This is a consequence of greater UGDH gene promoter activity and more abundant steady-state UGDH mRNA. Six Sp1 sites located in the proximal 550 bp of the UGDH gene promoter appear to determine basal promoter activity, as does a previously unrecognized 49-bp sequence spanning -1436 nucleotides (nt) and -1388 nt that negatively affects activity. Nuclear Sp1 protein is more abundant in orbital fibroblasts, and its binding to specific sites on DNA is greater than that in dermal fibroblasts. Mutating each of these Sp1 sites in a UGDH gene promoter fragment, extending from -1387 to +71 nt and fused to a luciferase reporter, results in divergent activities when transfected in orbital and dermal fibroblasts. Reducing Sp1 attenuated UGDH gene promoter activity, lowered steady-state UGDH mRNA levels, and reduced UGDH enzyme activity. Targeting Sp1 and UGDH with specific siRNAs also lowered hyaluronan synthase-1 (HAS-1) and HAS-2 levels and reduced hyaluronan accumulation in orbital fibroblasts. These findings suggest that orbital fibroblasts express high levels of UGDH in an anatomic-specific manner, apparently the result of greater constitutive Sp1. These high UGDH levels may underlie susceptibility of the orbit to localized overproduction of hyaluronan in Graves disease.

Regulation of UDP-glucose dehydrogenase is sufficient to modulate hyaluronan production and release, control sulfated GAG synthesis, and promote chondrogenesis

Glycosaminoglycans (GAGs) are critical for extracellular matrix (ECM) integrity in cartilage but mechanisms regulating their synthesis are not defined. UDP-glucose dehydrogenase (UGDH) catalyses UDP-glucose oxidation to UDP-glucuronic acid, an essential monosaccharide in many GAGs. Our previous studies in articular surface (AS) cells from embryonic joints have established pivotal roles for mitogen-activated protein kinases (MAPK) in synthesis of the unsulfated GAG, hyaluronan (HA). We investigated the functional significance of UGDH in GAG production and chondrogenesis, and determined roles for MEK-ERK and p38MAPK pathways in regulating UGDH expression and function. Inhibitors of MEK and p38MAPK reduced UGDH protein in AS cells. Treatment with TGF-β (archetypal growth factor) increased UGDH expression, sulfated (s)-GAG/HA release and pericellular matrix formation in a p38MAPK-dependent manner. Retroviral overexpression of UGDH augmented HA/sGAG release and pericellular matrix elaboration, which were blocked by inhibiting MEK but not p38MAPK. UGDH overexpression increased cartilage nodule size in bone marrow culture, promoted chondrogenesis in limb bud micromass culture and selectively suppressed medium HA levels and modified GAG sulfation, as assessed by FACE analysis. Our data provide evidence that: (i) TGF-β regulates UGDH expression via p38MAPK to modulate sGAG/HA secretion, (ii) MEK-ERK, but not p38MAPK facilitates UGDH-induced HA and sGAG release, and (iii) increased UGDH expression promotes chondrogenesis directly and differential modifies GAG levels and sulfation. These results indicate a more diverse role for UGDH in the support of selective GAG production than previously described. Factors regulating UGDH may provide novel candidates for restoring ECM integrity in degenerative cartilage diseases, such as osteoarthritis.Arthritis Research Campaign.

Dietary oleic acid as a control fatty acid for polyunsaturated fatty acid intervention studies: a transcriptomics and proteomics investigation using interleukin-10 gene-deficient mice

Oleic acid (OA) has been used as a control fatty acid in dietary polyunsaturated fatty acid (PUFA) intervention studies due to its lack of effect on eiconasoid biosynthesis. Since the effect of OA as a control fatty acid has not yet been investigated for transcriptomics and proteomics studies, this study aimed to test whether colonic transcriptome and proteome profiles associated with colitis development in mice fed a linoleic acid-rich corn oil-AIN-76A diet (Il10(-/-) compared to C57 mice) where similar to those of OA-fed Il10(-/-) compared to C57 mice (genotype comparison). A close clustering of colonic gene and protein expression profiles between the mice fed the AIN-76A or OA diet was observed. Inflammation-induced regulatory processes associated with cellular and humoral immune responses, cellular stress response and metabolic processes related to energy utilization were identified in Il10(-/-) compared to C57 mice fed either diet. Thus OA was considered as a suitable control unsaturated fatty acid for use in multi-omics PUFA studies. The second aim of this study was to test the effect of an OA-enriched AIN-76A diet compared to a linoleic acid-rich corn oil-AIN-76A diet on colonic transcriptome and proteome changes within Il10(-/-) or C57 mice (diet comparison). Overall, there was a limited concordance observed between measureable transcriptomics and proteomics profiles for genotype and diet comparisons. This underlines the importance and validity of a systems biology approach to understand the effects of diet on gene expression as a function of the genotype.

Udp-glucose dehydrogenase as a novel field-specific candidate biomarker of prostate cancer

Uridine diphosphate (UDP)-glucose dehydrogenase (UGDH) catalyzes the oxidation of UDP-glucose to yield UDP-glucuronic acid, a precursor for synthesis of glycosaminoglycans and proteoglycans that promote aggressive prostate cancer (PC) progression. The purpose of our study was to determine if the UGDH expression in normal appearing acini (NAA) from cancerous glands is a candidate biomarker for PC field disease/effect assayed by quantitative fluorescence imaging analysis (QFIA). A polyclonal antibody to UGDH was titrated to saturation binding and fluorescent microscopic images acquired from fixed, paraffin-embedded tissue slices were quantitatively analyzed. Specificity of the assay was confirmed by Western blot analysis and competitive inhibition of tissue labeling with the recombinant UGDH. Reproducibility of the UGDH measurements was high within and across analytical runs. Quantification of UGDH by QFIA and Reverse-Phase Protein Array analysis were strongly correlated (r = 0.97), validating the QFIA measurements. Analysis of cancerous acini (CA) and NAA from PC patients vs. normal acini (NA) from noncancerous controls (32 matched pairs) revealed significant (p < 0.01) differences, with CA (increased) vs. NA, NAA (decreased) vs. NA and CA (increased) vs. NAA. Areas under the Receiver Operating Characteristic curves were 0.68 (95% CI: 0.59-0.83) for NAA and 0.71 (95% CI: 0.59-0.83) for CA (both vs. NA). These results support the UGDH content in prostatic acini as a novel candidate biomarker that may complement the development of a multi-biomarker panel for detecting PC within the tumor adjacent field on a histologically normal biopsy specimen.

Identification and characterization of the human xylosyltransferase I gene promoter region

Human xylosyltransferase I catalyzes the initial and rate-limiting step in the biosynthesis of glycosaminoglycans and proteoglycans. Furthermore, this enzyme has been shown to play a major role in the physiological development of bone and cartilage as well as in pathophysiological processes such as systemic sclerosis, dilated cardiomyopathy, or fibrosis. Here, we report for the first time the identification and characterization of the XYLT1 gene promoter region and important transcription factors involved in its regulation. Members of the activator protein 1 (AP-1) and specificity protein 1 (Sp1) family of transcription factors are necessary for the transcriptional regulation of the XYLT1 gene, which was proven by curcumin, tanshinone IIA, mithramycin A, and short interference RNA treatment. A stepwise 5' and 3' deletion of the predicted GC-rich promoter region, which lacks a TATA and/or CAAT box, revealed that a 531-bp core promoter element is able to drive the transcription on a basal level. A binding site for transcription factors of the AP-1 family, which is essential for full promoter activity, was identified by site-directed mutagenesis located 730 bp 5' of the translation initiation site. The ability of this site to bind members of the AP-1 family was further verified by electrophoretic mobility shift assays. A promoter element containing this binding site was able to drive the transcription to about 79-fold above control in SW1353 chondrosarcoma cells. Our findings provide a first insight into the regulation of the XYLT1 gene and may contribute to understanding the processes taking place during extracellular matrix formation and remodeling in health and disease.

Androgen-stimulated UDP-glucose dehydrogenase expression limits prostate androgen availability without impacting hyaluronan levels

UDP-glucose dehydrogenase (UGDH) oxidizes UDP-glucose to UDP-glucuronate, an essential precursor for production of hyaluronan (HA), proteoglycans, and xenobiotic glucuronides. High levels of HA turnover in prostate cancer are correlated with aggressive progression. UGDH expression is high in the normal prostate, although HA accumulation is virtually undetectable. Thus, its normal role in the prostate may be to provide precursors for glucuronosyltransferase enzymes, which inactivate and solubilize androgens by glucuronidation. In this report, we quantified androgen dependence of UGDH, glucuronosyltransferase, and HA synthase expression. Androgen-dependent and androgen-independent human prostate cancer cell lines were used to test the effects of UGDH manipulation on tumor cell growth, HA production, and androgen glucuronidation. Dihydrotestosterone (DHT) increased UGDH expression approximately 2.5-fold in androgen-dependent cells. However, up-regulation of UGDH did not affect HA synthase expression or enhance HA production. Mass spectrometric analysis showed that DHT was converted to a glucuronide, DHT-G, at a 6-fold higher level in androgen-dependent cells relative to androgen-independent cells. The increased solubilization and elimination of DHT corresponded to slower cellular growth kinetics, which could be reversed in androgen-dependent cells by treatment with a UDP-glucuronate scavenger. Collectively, these results suggest that dysregulated expression of UGDH could promote the development of androgen-independent tumor cell growth by increasing available levels of intracellular androgen.

Farnesoid X receptor antagonizes nuclear factor kappaB in hepatic inflammatory response

The farnesoid X receptor (FXR) is a nuclear receptor that plays key roles in hepatoprotection by maintaining the homeostasis of liver metabolism. FXR null mice display strong hepatic inflammation and develop spontaneous liver tumors. In this report, we demonstrate that FXR is a negative modulator of nuclear factor kappaB (NF-kappaB)-mediated hepatic inflammation. Activation of FXR by its agonist ligands inhibited the expression of inflammatory mediators in response to NF-kappaB activation in both HepG2 cells and primary hepatocytes cultured in vitro. In vivo, compared with wild-type controls, FXR(-/-) mice displayed elevated messenger RNA (mRNA) levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interferon-inducible protein 10, and interferon-gamma in response to lipopolysaccharide (LPS). Examination of FXR(-/-) livers showed massive necroses and inflammation after treatment with LPS at a dose that does not induce significant liver damage or inflammation in wild-type mice. Moreover, transfection of a constitutively active FXR expression construct repressed the iNOS, COX-2, interferon-inducible protein 10 and interferon-gamma mRNA levels induced by LPS administration. FXR activation had no negative effects on NF-kappaB-activated antiapoptotic genes, suggesting that FXR selectively inhibits the NF-kappaB-mediated hepatic inflammatory response but maintains or even enhances the cell survival response. On the other hand, NF-kappaB activation suppressed FXR-mediated gene expression both in vitro and in vivo, indicating a negative crosstalk between the FXR and NF-kappaB signaling pathways. Our findings reveal that FXR is a negative mediator of hepatic inflammation, which may contribute to the critical roles of FXR in hepatoprotection and suppression of hepatocarcinogenesis.

Hyperglycemia suppresses hepatic scavenger receptor class B type I expression

Hyperglycemia is a major risk factor for atherosclerotic disease. Hepatic scavenger receptor class B type I (SR-BI) binds HDL particles that mediate reverse cholesterol transport and thus lowers the risk of atherosclerosis. Here we examined glucose regulation of SR-BI gene expression in both HepG2 cells and whole animals. Results showed that hepatic SR-BI mRNA, protein, and uptake of cholesterol from HDL were halved following 48 h of exposure to 22.4 vs. 5.6 mM glucose. As in the case of the cell culture model, hepatic expression of SR-BI was lower in diabetic rats than in euglycemic rats. Transcriptional activity of the human SR-BI promoter paralleled endogenous expression of the gene, and this activity was dependent upon the dose of glucose. Next, we used inhibitors of select signal transduction pathways to demonstrate that glucose suppression of SR-BI was sensitive to the p38 MAPK inhibitor. Expression of a constitutively active p38 MAPK inhibited SR-BI promoter activity in the presence or absence of glucose. A dominant-negative p38 MAPK abolished the inhibitory effect of glucose on promoter activity. Deletional analysis located a 50-bp fragment of the promoter that mediated the effects of glucose. Within this DNA fragment there were several specificity protein-1 (Sp1) binding sites, and cellular knockdown of Sp1 abrogated its suppression by glucose. Together, these results indicate that the glucose suppression of SR-B1 expression is partially mediated by the activation of the p38 MAPK-Sp1 pathway and raise the possibility that the inhibition of hepatic SR-BI expression under high-glucose conditions provides a mechanism for accelerated atherosclerosis in diabetics.

Regulation of human LZIP expression by NF-kappaB and its involvement in monocyte cell migration induced by Lkn-1

Human LZIP is a transcription factor that is involved in leukocyte cell mobility. Expression of LZIP is known to differentially regulate monocyte cell migration induced by CCR1-dependent chemokines. However, its transcriptional regulation has not been characterized. Our results indicate that Lkn-1 induces LZIP expression in a time- and dose-dependent manner, and the induction of LZIP shows an immediate early response to Lkn-1. We identified and cloned approximately 1.4 kb of the LZIP promoter from a human genomic DNA. To identify regulatory elements controlling restricted expression of LZIP, deletion mutants were constructed from the 1469-bp LZIP promoter region (-1219/+251) linked to the luciferase reporter gene. Maximal promoter activity was contained within 613 bp from the tentative transcription initiation site and was sharply reduced in a truncated construct (-338/+251). This promoter sequence contained consensus NF-kappaB- and Sp-1-binding sites. Results from an inhibitor assay showed that NF-kappaB is involved in Lkn-1-induced LZIP expression, but Sp-1 is not. We also demonstrated that NF-kappaB binds to the LZIP promoter and that the binding is specific, as revealed by an electrophoretic mobility shift assay and a mutation analysis. Chemotaxis analysis showed that LZIP expression because of the NF-kappaB subfamily is specifically involved in Lkn-1-induced chemotaxis. Our findings suggest that transcription factor NF-kappaB plays an important role in regulation of LZIP expression, and LZIP expression regulates the monocyte cell migration induced by Lkn-1.

Identification of a cis-acting element responsible for negative regulation of the human UDP-glucose dehydrogenase gene expression

The enzyme UDP-glucose dehydrogenase (UGDH) catalyzes the conversion of UDP-glucose to UDP-glucuronic acid, which is essential for the biosynthesis of complex carbohydrates such as hyaluronan in many cell types, and is required for detoxification of toxic compounds in the liver. We previously defined the 714 bp 5'-flanking region of the UGDH gene as the core promoter, with putative negative regulatory elements residing in the region upstream of it. In the present study, we delineated the region from nucleotide positions -1057 to -957 on the UGDH promoter to be responsible for the repression of promoter activity. A mutation at nucleotide -1003, which is contained within a motif predicted to be the response element for peroxisome proliferator receptor alpha (PPARalpha), abolished the suppression effect. DNA-protein interaction was observed at this motif by electrophoretic mobility shift assay. The proteins interacting with the PPRE-like repressor motif were purified by biotin-labeled DNA affinity chromatography. Subsequently, MALDI-TOF identified the purified proteins as a 62-kDa zinc finger and a 42-kDa beta-actin protein. Hence in this study we report the presence of an inhibitory cis-element in the distal region of the UGDH promoter that interacts with putative transcriptional repressors for the negative regulation of the UGDH gene.

Evidence of calcium‐dependent pathway in the regulation of human β1,3‐glucuronosyltransferase‐1 (GlcAT‐I) gene expression: a key enzyme in proteoglycan synthesis

The importance of heparan- and chondroitin-sulfate proteoglycans in physiological and pathological processes led to the investigation of the regulation of beta1,3-glucuronosyltransferase I (GlcAT-I), responsible for the completion of glycosaminoglycan-protein linkage tetrasaccharide, a key step prior to polymerization of chondroitin- and heparan-sulfate chains. We have cloned and functionally characterized GlcAT-I 5'-flanking regulatory region. Mutation analysis and electrophoretic mobility shift assays demonstrated the importance of Sp1 motif located at -65/-56 position in promoter activity. Furthermore, we found that elevation of intracellular calcium concentration by the calcium ionophore ionomycin stimulated GlcAT-I gene expression as well as glycosaminoglycan chain synthesis in HeLa cells. Bisanthracycline, an anti-Sp1 compound, inhibited GlcAT-I basal promoter activity and suppressed ionomycin induction, suggesting the importance of Sp1 in calcium induction of GlcAT-I gene expression. Nuclear protein extracts from ionomycin-induced cells exhibited an increased DNA binding of Sp1 factor to the consensus sequence at position -65/-56. Signaling pathway analysis and MEK inhibition studies revealed the important role of p42/p44 MAPK in the stimulation of GlcAT-I promoter activity by ionomycin. The present study identifies, for the first time, GlcAT-I as a target of calcium-dependent signaling pathway and evidences the critical role of Sp1 transcription factor in the activation of GlcAT-I expression.

Effects of xenobiotics and peroxisome proliferator-activated receptor-alpha on the human UDPglucose dehydrogenase gene expression

During drug metabolism, UDPglucuronate, a product of the reaction catalyzed by the enzyme UDPglucose dehydrogenase (UGDH), is conjugated with the metabolites to facilitate their elimination. So far, it is not known whether xenobiotics can modulate the UGDH gene expression. This question was tested by treating the human hepatoma cells HepG2 with several medicinal compounds and the UGDH gene expression analyzed by using real-time PCR. Both eugenol and rifampicin showed activation of the gene expression. Piperine showed slight down-regulation of the UGDH gene expression, whereas no effect was observed with acetaminophen treatment. Through promoter-reporter gene assays, we found that rifampicin showed multiple-folds activation of a 1.23-kb UGDH promoter construct, the region likely to respond to rifampicin treatment is located within the range -632 to -1,050. A bioinformatics search for xenobiotic response element in this region has predicted a binding motif for the peroxisome proliferator-activated receptor-alpha(PPARalpha) at position -1,003. A mutation at the predicted PPAR recognizing motif eliminated normal suppression as well as the rifampicin activation effect on the UGDH promoter activity. Cotransfection with the PPARalpha and retinoid X receptor-alpha expression vectors and subsequent treatment with the PPARalpha agonist led to the suppression of the UGDH promoter activity either in the presence or absence of rifampicin. Our study, for the first time, shows the UGDH gene to be under xenobiotic regulation and delineates a motif responsible for rifampicin response and transcriptional repression of the UGDH gene.

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.

Analysis of human UDP-glucose dehydrogenase gene promoter: identification of an Sp1 binding site crucial for the expression of the large transcript

UDP-glucose dehydrogenase (UGDH) catalyzes the conversion of UDP-glucose to UDP-glucuronic acid, which is required in liver for the excretion of toxic compounds, and for the biosynthesis of complex carbohydrates, such as hyaluronan, in many cell types. Analysis of a human EST database, as well as the results of a 5'-RACE experiment, have revealed the presence of two transcription start sites approximately 160 bp apart in the human UGDH gene confirming previous Northern hybridization results. To delineate the regions in the UGDH promoter required for regulating the expression of the gene, in particular the synthesis of the large transcript, serial deletions of the 2.1-kb UGDH promoter region were constructed and their activities determined by the firefly luciferase reporter gene assay. Our results indicate that the region from nucleotide position -486 to -632 relative to the start of the small transcript contains positive regulatory elements that contribute to gene expression. Mithramycin A, an inhibitor of transcription factor Sp1, abrogates the promoter activity, suggesting the involvement of this specific protein in UGDH expression. By using site-directed mutagenesis, we analyzed the functional contribution of three putative Sp1 binding elements within this region. A mutation at position -564 demonstrated that this site serves as an enhancing element in both HepG2 and HeLa cells. The complex formation pattern revealed by an electrophoretic mobility shift assay as well as an anti-Sp1 antibody-mediated supershift assay confirmed the identity of this GC box as an Sp1 binding motif. Our results thus identify an alternative transcription start site on the UGDH promoter, and locate the cis-element that greatly enhances the basal transcriptional activity of UGDH gene.

c-Krox down-regulates the expression of UDP–glucose dehydrogenase in chondrocytes

Chondrocyte glycosaminoglycan (GAG) synthesis is regulated by the availability of UDP-glucuronate, the substrate of glucuronosyl transferases which form the GAG chains in proteoglycans and hyaluronan. UDP-glucose dehydrogenase (UDPGD) is therefore a key enzyme in the synthesis of UDP-glucuronate from glucose. However, the mechanisms regulating its expression in chondrocytes are not fully understood. We investigated the effect of c-Krox, a zinc-finger transcription factor previously shown to modulate several matrix genes, on the synthesis of GAG and transcriptional activity of several UDPGD gene promoter constructs, using transient transfection and decoy experiments in rabbit articular chondrocytes (RACs). We show that overexpression of c-Krox inhibits radiosulfate incorporation into neosynthesized GAG and that the effect was mediated by a cis-sequence located between +18 and +39bp of the UDPGD gene. Since that sequence can also bind Sp1/Sp3 factors, it is likely that c-Krox acts in concert with these proteins to modulate the UDPGD gene expression in articular chondrocytes.

Hypoxia-responsive transcription factors

Hypoxia is a common pathophysiological occurrence with a profound impact on the cellular transcriptome. The consequences of hypoxia-induced or hypoxia-repressed gene expression have important implications in disease processes as diverse as tumour development and chronic inflammation. While the hypoxia-inducible factor (HIF-1) plays a major role in controlling the ubiquitous transcriptional response to hypoxia, it is clear that a number of other transcription factors are also activated either directly or indirectly. In this review, we comprehensively discuss the transcription factors that have been reported to be hypoxia-responsive and the signalling mechanisms leading to their activation. Understanding such events will enhance our understanding of cellular oxygen sensing.

Class III β-Tubulin Overexpression Is a Prominent Mechanism of Paclitaxel Resistance in Ovarian Cancer Patients

The vast majority of women with advanced ovarian cancer will ultimately relapse and develop a drug-resistant disease with an overall 5-year survival of &lt;50%. Unfortunately, the mechanisms of drug resistance actually operating in patients are still unknown. To address this issue, in 41 patients affected by advanced ovarian cancer the three main mechanisms of paclitaxel resistance were investigated: overexpression of MDR-1 gene, point mutations at prominently expressed α-tubulin and β-tubulin genes and selective alterations in the expression of β-tubulin isotypes. MDR-1 and the β-tubulin isotypes expression were evaluated by semiquantitative and real-time PCR. On the same specimens, quantitative immunohistochemistry was also done in the tumor area. No statistically significant changes of MDR-1 expression were noticed between the sensitive and resistant patients either at the mRNA or protein level. The tubulin mutations for the ubiquitous α-tubulin and β-tubulin genes were evaluated by automated DNA sequencing, and in all patients, no mutations were detected in both resistant and sensitive cases. With regard to the expression of tubulin isoforms, a statistically significant up-regulation of class III β-tubulin was found in the resistant subset. It is worth noting that this statistically significant increase of the expression of class III β-tubulin was detectable at the mRNA and protein level. By a direct comparison of the three main known mechanisms of paclitaxel resistance, this study indicates that overexpression of class III β-tubulin is the most prominent mechanism of paclitaxel resistance in ovarian cancer.

Sp1-targeted inhibition of gene transcription by WP631 in transfected lymphocytes

The binding of Sp1 transcription factor to DNA is considered a potential target for small ligands designed to interfere with gene transcription. We attempted to distinguish the direct inhibition of the Sp1-binding to DNA in vivo (cell culture) from more indirect effects due to the network of pathways that modulate cell cycle progression, which may decrease transcription without direct interference with Sp1-DNA interactions. We tested whether the Sp3 protein, whose putative binding sequence overlaps the Sp1 site, can inhibit Sp1-activated transcription and interfere with drug-DNA interactions. A well-characterized model system consisting of a wtGLUT1 (wild-type glucose transporter 1) gene promoter, or a mutated mut2GLUT1 promoter, linked to a CAT (chloramphenicol acetyltransferase) reporter gene, was used to analyze the effects of overexpressed Sp1 and Sp3 transcription factors in transiently transfected Jurkat T lymphocytes. Bisanthracycline WP631, a potent inhibitor of Sp1-activated transcription in vitro, was assayed for its ability to specifically inhibit transcription in transfected Jurkat T lymphocytes. The mut2GLUT1 promoter was used to further discriminate between the WP631 interference with Sp1-DNA complexes and Sp3-induced inhibition, since the Sp3-binding site is canceled in this promoter and replaced by a high-affinity binding site for WP631.

Hypoxia-inducible factor-1-independent regulation of vascular endothelial growth factor by hypoxia in colon cancer

The induction of vascular endothelial growth factor (VEGF) is an essential feature of tumor angiogenesis, and the hypoxia-inducible factor-1 (HIF-1) transcription factor is known to be a key mediator of this process. In colon cancer, the frequently mutated K-ras oncogene also can regulate VEGF expression, but the role that K-ras may play in hypoxia is unknown. Hypoxia induced VEGF promoter activity, mRNA, and protein levels in colon cancer cells. Although HIF-1alpha was induced by hypoxia, VEGF reporter constructs with selectively mutated hypoxia-response elements remained responsive to hypoxia. In addition, "knockdown" of HIF-1alpha by RNA interference only minimally inhibited the hypoxic induction of VEGF. A region of the VEGF promoter between -420 and -90 bp mediated this HIF-independent induction by hypoxia. The introduction of K-ras(Val12) augmented the hypoxic induction of VEGF, and this was observed in wild-type and HIF-1alpha knockdown colon cancer cells. Thus, VEGF may be induced by hypoxia through HIF-dependent and HIF-independent pathways, and K-ras also can induce VEGF in hypoxia independent of HIF-1. These findings suggest the existence of multiple mechanisms regulating the hypoxic induction of VEGF in colon cancer.