Platelet-derived growth factor is a principal inductive factormodulating mannose 6-phosphate/insulin-like growth factor-II receptorgene expression via a distal E-box in activated hepatic stellate cells. Biochem J. 2000;345 Pt 2:225-231. [PMID: 10620498 DOI: 10.1042/bj3450225]

Characterization of oocyte-expressed GDF9 gene in buffalo and mapping of its TSS and putative regulatory elements

Summary In spite of emerging evidence about the vital role of GDF9 in determination of oocyte competence, there is insufficient information about its regulation of oocyte-specific expression, particularly in livestock animals. Because of the distinct prominence of buffalo as a dairy animal, the present study was undertaken to isolate and characterize GDF9 cDNA using orthologous primers based on the bovine GDF9 sequence. GDF9 transcripts were found to be expressed in oocytes irrespective of their follicular origin, and shared a single transcription start site (TSS) at -57 base pairs (bp) upstream of ATG. Assignment of the TSS is consistent with the presence of a TATA element at -23 of the TSS mapped in this study. Localization of a buffalo-specific minimal promoter within 320 bp upstream of ATG was consolidated by identification of an E-box element at -113bp. Presence of putative transcription factor binding sites and other cis regulatory elements were analyzed at ~5 kb upstream of TSS. Various germ cell-specific cis-acting regulatory elements (BNCF, BRNF, NR2F, SORY, Foxh1, OCT1, LHXF etc.) have been identified in the 5' flanking region of the buffalo GDF9 gene, including NOBOX DNA binding elements and consensuses E-boxes (CANNTG). Presence of two conserved E-boxes found on buffalo sequence at -520 and -718 positions deserves attention in view of its sequence deviation from other species. Two NOBOX binding elements (NBE) were detected at the -3471 and -203 positions. The fall of the NBE within the putative minimal promoter territory of buffalo GDF9 and its unique non-core binding sequence could have a possible role in the control of the core promoter activity.

Local inhibition of liver fibrosis by specific delivery of a platelet-derived growth factor kinase inhibitor to hepatic stellate cells

Liver fibrosis is characterized by excessive proliferation and activation of hepatic stellate cells (HSC), a process in which platelet-derived growth factor (PDGF) plays an important role. Inhibition of liver fibrosis via specific delivery of a PDGF kinase inhibitor to HSC might therefore be an attractive strategy. The HSC-selective carrier mannose-6-phosphate modified human serum albumin (M6PHSA) was equipped with a tyrosine kinase inhibitor, 4-chloro-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-benzamide (PAP19) (an imatinib derivative), by means of the platinum-based universal linkage system (ULS). The antifibrotic activity of PAP19-M6PHSA was evaluated in culture-activated rat HSC and precision-cut liver slices from fibrotic rats. After 24-h incubation, both free inhibitor PAP19 and PAP19-M6PHSA showed potent activity, as determined by quantitative reverse transcription-polymerase chain reaction analysis of alpha-smooth muscle actin (alphaSMA) and procollagen 1a1. Next, we examined the organ distribution and antifibrotic activity of PAP19-M6PHSA in bile duct-ligated (BDL) rats. Male Wistar rats at day 10 after BDL were administered a single dose of PAP19-M6PHSA and sacrificed at 2 h, 1 day, or 2 days afterward. The accumulation of PAP19-M6PHSA in the liver was quantified by high-performance liquid chromatography analysis (30% of the injected dose at 2 h) and detected in the liver by staining of the carrier. Liver drug levels were sustained at 24 and 48 h after the single dose. Furthermore, PAP19-M6PHSA reduced collagen deposition (Sirius red staining) and alphaSMA staining of activated HSC at these time points in comparison with saline-treated rats. We therefore conclude that delivery of a PDGF-kinase inhibitor to HSC is a promising technology to attenuate liver fibrogenesis.

Regulation of Growth Differentiation Factor 9 Expression in Oocytes In Vivo: A Key Role of the E-Box1

Growth differentiation factor 9 (GDF9) is preferentially expressed in oocytes and is essential for female fertility. To identify regulatory elements that confer high-level expression of GDF9 in the ovary but repression in other tissues, we generated transgenic mice in which regions of the Gdf9 locus were fused to reporter genes. Two transgenes (-10.7/+5.6mGdf9-GFP) and (-3.3/+5.6mGdf9-GFP) that contained sequences either 10.7 or 3.3 kb upstream and 5.6 kb downstream of the Gdf9 initiation codon demonstrated expression specifically in oocytes, thereby mimicking endogenous Gdf9 expression. In contrast, transgenes -10.7mGdf9-Luc and -3.3mGdf9-Luc, which lacked the downstream 5.6-kb region, demonstrated reporter expression not only in oocytes but also high expression in male germ cells. This suggests that the downstream 5.6-kb sequence contains a testis-specific repressor element and that 3.3 kb of 5'-flanking sequence contains all the cis-acting elements for directing high expression of Gdf9 to female (and male) germ cells. To define sequences responsible for oocyte expression of Gdf9, we analyzed sequences of Gdf9 genes from 16 mammalian species. The approximately 400 proximal base pairs upstream of these Gdf9 genes are highly conserved and contain a perfectly conserved E-box (CAGCTG) sequence. When this 400-bp region was placed upstream of a luciferase reporter (-0.4mGdf9-Luc), oocyte-specific expression was observed. However, a similar transgene construct (-0.4MUT-mGdf9-Luc) with a mutation in the E-box abolished oocyte expression. Likewise, the presence of an E-box mutation in a longer construct (-3.3MUT-mGdf9-Luc) abolished expression in the ovary but not in the testis. These observations indicate that the E-box is a key regulatory sequence for Gdf9 expression in the ovary.

Diagnostic value of platelet derived growth factor-BB, transforming growth factor-β1, matrix metalloproteinase-1, and tissue inhibitor of matrix metalloproteinase-1 in serum and peripheral blood mononuclear cells for hepatic fibrosis

AIM: Noninvasive diagnosis of hepatic fibrosis has become the focus because of the limited biopsy, especially in the surveillance of treatment and in screening hepatic fibrosis. Recently, regulatory elements involved in liver fibrosis, such as platelet derived growth factor-BB (PDGF-BB), transforming growth factor-β₁ (TGF-β₁), matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), have been studied extensively. To determine whether these factors or enzymes could be used as the indices for the diagnosis of hepatic fibrosis, we investigated them by means of receiver operating characteristic (ROC) curve.

METHODS: Serum samples from sixty patients with chronic viral hepatitis B and twenty healthy blood donors were assayed to determine the level of PDGF-BB, TGF-β₁, MMP-1, and TIMP-1 with ELISA, and HA, PCIII, C-IV, and LN level with RIA. The message RNA (mRNA) expression of TIMP-1 and MMP-1 in peripheral blood mononuclear cells (PBMCs) was detected by RT-PCR and Northern blot hybridization. Liver biopsy was performed in all patients. The biopsy samples were histopathologically examined. The trial was double-blind controlled.

RESULTS: The serum level of PDGF-BB, TIMP-1, the ratio of TIMP-1 and MMP-1 (TIMP-1/MMP-1), mRNA expression of TIMP-1 (TIMP-1mRNA), and the ratio of TIMP-1mRNA and MMP-1mRNA (TIMP-1mRNA/MMP-1mRNA) in patients was significantly higher than those in the healthy blood donors (t = 2.514-11.435, P = 0.000-0.016). The serum level of PDGF-BB, TIMP-1, TIMP-1/MMP-1, and TIMP-1mRNA was positively correlated with fibrosis stage and inflammation grade (r = 0.239-0.565, P = 0.000-0.033), while the serum level of MMP-1 was negatively correlated with fibrosis stage and inflammation grade, and TIMP-1mRNA/MMP-1mRNA was positively correlated with inflammation grade. Through the analysis by ROC curve, serum PDGF-BB was the most valuable marker, and its sensitivity was the highest among the nine indices. The markers with the highest specificity were TIMP-1mRNA and TIMP-1mRNA/MMP-1mRNA in PBMCs. The area under the curve (AUC) of PDGF-BB, TIMP-1mRNA, TIMP-1mRNA/MMP-1mRNA, TIMP-1/MMP-1, HA, PCIII, TIMP-1, C-IV, and LN was 0.985, 0.876, 0.792, 0.748, 0.728, 0.727, 0.726, 0.583, and 0.463, respectively. The sensitivity and the specificity in the parallel test was 99.0% and 95.0% when serum PDGF-BB, TIMP-1mRNA and TIMP-1mRNA/MMP-1mRNA was detected simultaneously.

CONCLUSION: Serum level of PDGF-BB, TIMP-1mRNA, TIMP-1mRNA/MMP-1mRNA in PBMCs, and serum level of TIMP-1 and TIMP-1/MMP-1 can be used as the indices for the diagnosis of hepatic fibrosis, but the former three are more useful. The combination of serum PDGF-BB, TIMP-1mRNA and TIMP-1mRNA/MMP-1mRNA in PBMCs is even more efficient in screening liver fibrosis.

Transforming growth factor-beta 1 signaling contributes to Caco-2 cell growth inhibition induced by 1,25(OH)(2)D(3)

Growth of Caco-2 and many cancer cells is inhibited by 1,25(OH)(2)D(3). Whereas TGF-beta 1 inhibits normal colonic epithelial cell growth, most human colon cancer-derived cells, including Caco-2 and SW480 cells, are resistant to it. The mechanisms underlying these antiproliferative actions and resistance to TGF-beta growth inhibition are largely unknown. We observed that 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] sensitized Caco-2 and SW480 cells to TGF-beta 1 growth inhibitory effects. Versus 1,25(OH)(2)D(3) alone, the combination of 1,25(OH)(2)D(3) and TGF-beta 1 significantly reduced cell numbers. Also, the amount of active TGF-beta 1 was increased (~4-fold) by this secosteroid in conditioned media from Caco-2 cells. The 1,25(OH)(2)D(3) increased the expression of IGF-II receptors (IGF-IIR), which facilitated activation of latent TGF-beta 1, and was found to activate TGF-beta signaling in Caco-2 cells. By using neutralizing antibodies to human TGF-beta 1, we showed that this cytokine contributes to secosteroid-induced inhibition of Caco-2 cell growth. Also, 1,25(OH)(2)D(3) was found to enhance the type I TGF-beta receptor mRNA and protein abundance in Caco-2 cells. Whereas the 1,25(OH)(2)D(3)-induced sensitization of Caco-2 cells to TGF-beta 1 was IGF-IIR independent, the type I TGF-beta 1 receptor was required for this sensitization. Thus 1,25(OH)(2)D(3) treatment of Caco-2 cells results in activation of latent TGF-beta 1, facilitated by the enhanced expression of IGF-IIR by this secosteroid. Also, 1,25(OH)(2)D(3) sensitized Caco-2 cells to growth inhibitory effects of TGF-beta 1, contributing to the inhibition of Caco-2 cell growth by this secosteroid.