The importance of monochromatic lights in the production of phenolic acids and flavonoids in shoot cultures of Aronia melanocarpa, Aronia arbutifolia and Aronia × prunifolia

Shoot cultures of Aronia melanocarpa, A. arbutifolia and A. × prunifolia were maintained on Murashige and Skoog medium with 1 mg/l each of BA and NAA under monochromatic lights (far-red, red, blue lights, UV-A-irradiation), in darkness, and under white light (control). HPLC-DAD analyses of 19 phenolic acids and 11 flavonoids in methanolic extracts from the shoots revealed in all of them the presence of three depsides (chlorogenic, neochlorogenic and rosmarinic acids), protocatechuic acid, four flavonoid glycosides (cynaroside, quercitrin, hyperoside and rutoside), and additionally, in A. arbutifolia, 3,4-dihydroxyphenylacetic acid. Depending on light quality, the total amounts of these metabolites increased 1.8-5.9 times, reaching maximum values under blue light: 527.40 and 144.61 mg 100 g-1 DW (A. melanocarpa), 543.27 and 85.82 mg 100 g-1 DW (A. arbutifolia) and 1615.18 and 220.65 mg 100 g-1 DW (A. × prunifolia), respectively. The maximum total amounts were 1.3-3.6 times higher than under white light. The quantities of individual metabolites changed from 1.2 to 11.0 times, with high amounts of neochlorogenic acid and quercitrin in A. melanocarpa (243.35 and 75.64 mg 100 g-1 DW), and of chlorogenic and rosmarinic acids and quercitrin in A. arbutifolia (236.52, 219.35 and 51.01 mg 100 g-1 DW). Extremely high amounts of depsides (418.83, 644.68, 548.86 mg 100 g-1 DW) and quercitrin (165.88 mg 100 g-1 DW) were produced in cultures of the hybrid - A. × prunifolia. The results are potentially useful for practical applications. This is the first report documented the importance of light quality on the production of phenolic acids and flavonoids in three aronia in vitro cultures.

New prospects in the roles of the C-terminal domains of VEGF-A and their cooperation for ligand binding, cellular signaling and vessels formation

VEGF-A is a crucial growth factor for blood vessel homeostasis and pathological angiogenesis. Due to alternative splicing of its pre-mRNA, VEGF-A is produced under several isoforms characterized by the combination of their C-terminal domains, which determines their respective structure, availability and affinity for co-receptors. As controversies still exist about the specific roles of these exon-encoded domains, we systematically compared the properties of eight natural and artificial variants containing the domains encoded by exons 1-4 and various combinations of the domains encoded by exons 5, 7 and 8a or 8b. All the variants (VEGF111a, VEGF111b, VEGF121a, VEGF121b, VEGF155a, VEGF155b, VEGF165a, VEGF165b) have a similar affinity for VEGF-R2, as determined by Surface plasmon resonance analyses. They strongly differ however in terms of binding to neuropilin-1 and heparin/heparan sulfate proteoglycans. Data indicate that the 6 amino acids encoded by exon 8a must be present and cooperate with those of exons 5 or 7 for efficient binding, which was confirmed in cell culture models. We further showed that VEGF165b has inhibitory effects in vitro, as previously reported, but that the shortest VEGF variant possessing also the 6 amino acids encoded by exon 8b (VEGF111b) is remarkably proangiogenic, demonstrating the critical importance of domain interactions for defining the VEGF properties. The number, size and localization of newly formed blood vessels in a model of tumour angiogenesis strongly depend also on the C-terminal domain composition, suggesting that association of several VEGF isoforms may be more efficient for treating ischemic diseases than the use of any single variant.

Invading basement membrane matrix is sufficient for MDA-MB-231 breast cancer cells to develop a stable in vivo metastatic phenotype

INTRODUCTION

The poor efficacy of various anti-cancer treatments against metastatic cells has focused attention on the role of tumor microenvironment in cancer progression. To understand the contribution of the extracellular matrix (ECM) environment to this phenomenon, we isolated ECM surrogate invading cell populations from MDA-MB-231 breast cancer cells and studied their genotype and malignant phenotype.

METHODS

We isolated invasive subpopulations (INV) from non invasive populations (REF) using a 2D-Matrigel assay, a surrogate of basal membrane passage. INV and REF populations were investigated by microarray assay and for their capacities to adhere, invade and transmigrate in vitro, and to form metastases in nude mice.

RESULTS

REF and INV subpopulations were stable in culture and present different transcriptome profiles. INV cells were characterized by reduced expression of cell adhesion and cell-cell junction genes (44% of down regulated genes) and by a gain in expression of anti-apoptotic and pro-angiogenic gene sets. In line with this observation, in vitro INV cells showed reduced adhesion and increased motility through endothelial monolayers and fibronectin. When injected into the circulation, INV cells induced metastases formation, and reduced injected mice survival by up to 80% as compared to REF cells. In nude mice, INV xenografts grew rapidly inducing vessel formation and displaying resistance to apoptosis.

CONCLUSION

Our findings reveal that the in vitro ECM microenvironment per se was sufficient to select for tumor cells with a stable metastatic phenotype in vivo characterized by loss of adhesion molecules expression and induction of pro-angiogenic and survival factors.

Metabolomic profiling with NMR discriminates between biphosphonate and doxorubicin effects on B16 melanoma cells

The metabolomic profiles of B16 melanoma cells were investigated in vitro with high resolution-magic angle spinning proton magnetic resonance spectroscopy and OPLS multivariate statistical analyse. We compared the profiles for untreated melanoma B16-F10 cells and Ca(2+) chelating EGTA, doxorubicin or BP7033 bisphosphonate treated cells. The two last molecules are known to induce anti-proliferative effects by different mechanisms of action in cells. Untreated and EGTA treated cells had similar profiles and were considered together as control cells. Several spectral regions could discriminate control from doxorubicin as well as BP7033 treated cells. Doxorubicin and BP7033 displayed distinct metabolic profiles. Important changes in neutral lipids and inositol were related to doxorubicin activity whereas BP7033 affected essentially phospholipids and alanine/lactate metabolism. These results provide new putative targets for both drugs. Metabolomics by NMR is shown here to be a good tool for the investigation of the mechanisms of action of drugs in pre-clinical studies.

Caveolin-1 and doxorubicin-induced P-glycoprotein modulate plasma cholesterol membrane accessibility in erythrolymphoblastic cell line

AIM/ BACKGROUND: Various interactions between Caveolae membrane domains, multidrug resistance transporter P-glycoprotein (P-gp) and cholesterol have been suggested. We tested the assumption that anthracycline-induced P-gp and Caveolin-1 have correlated effects on cholesterol distribution in plasma membrane.

MATERIALS AND METHODS

The present study was performed in four lymphoblastic K562 cell lines expressing none (KS), one (Cav and KR cells) or both P-gp and caveolin-1 proteins (CavKR cells).

RESULTS

The CavKR cell line exhibits a significantly higher free cholesterol content than the other cell lines. Cholesterol distribution at the outer leaflet was distinct from the total cellular cholesterol by its accessibility to cholesterol oxidase (COase). When cells were ATP-deprived, cholesterol accessibility to oxidation was significantly delayed in CavKR cells. Caveolin-1 or P-gp expression did not induce detectable changes in membrane cholesterol accessibility to COase.

CONCLUSION

Combination of functional P-gp, caveolae presence and lasting effect of anthracycline treatment appear determinant in free membrane cholesterol homeostasis and likely modulate cholesterol membrane order.

Lipopeptide-based liposomes for DNA delivery into cells expressing neuropilin-1

In this paper, liposomes containing a lipopeptide bearing a ligand specifically recognized by neuropilin-1 (NRP-1) have been used to target a human breast cancer cell line overexpressing this receptor. The synthesis of this lipopeptide, C16-A7R, formed by the sequence of 7 amino acids ATWLPPR, linked to a palmitoyl fatty chain by an amide bond was described. After the characterisation of cationic liposomes formulated with the lipopeptide, the results obtained using various techniques showed that the lipopeptide-based liposomes were well accumulated in cells of the human breast cancer line MDA-MB-231 overexpressing NRP-1. Delivery of reporter genes expressing either beta-galactosidase (beta-gal) or green fluorescent protein (GFP) was selectively enhanced in these cells when compared with NRP-1-negative cells. In MDA-MB-231 cells, an increase by 250% in beta-gal activity was observed when delivered by lipopeptide-based liposomes compared to cationic liposomes alone.

Structure-function analysis of the antiangiogenic ATWLPPR peptide inhibiting VEGF(165) binding to neuropilin-1 and molecular dynamics simulations of the ATWLPPR/neuropilin-1 complex

Heptapeptide ATWLPPR (A7R), identified in our laboratory by screening a mutated phage library, was shown to bind specifically to neuropilin-1 (NRP-1) and then to selectively inhibit VEGF(165) binding to this receptor. In vivo, treatment with A7R resulted in decreasing breast cancer angiogenesis and growth. The present work is focused on structural characterization of A7R. Analogs of the peptide, obtained by substitution of each amino acid with alanine (alanine-scanning) or by amino acid deletion, have been systematically assayed to determine the relative importance of the side chains of each residue with respect to the inhibitory effect of A7R on VEGF(165) binding to NRP-1. We show here the importance of the C-terminal sequence LPPR and particularly the key role of C-terminal arginine. In solution, A7R displays significant secondary structure of the backbone adopting an extended conformation. However, the functional groups of arginine are very flexible in the absence of NRP-1 pointing to an induced fit upon binding to the receptor. A MD trajectory of the A7R/NRP-1 complex in explicit water, based on the recent tuftsin/NRP-1 crystal structure, has revealed the hydrogen-bonding network that contributes to A7R's binding activity.

Antiangiogenic and antitumor activities of peptide inhibiting the vascular endothelial growth factor binding to neuropilin-1

Neuropilin-1 (NRP-1), a non-tyrosine kinase receptor of vascular endothelial growth factor-165 (VEGF165), was found expressed on endothelial and some tumor cells. Since its overexpression is correlated with tumor angiogenesis and progression, the targeting of NRP-1 could be a potential anti-cancer strategy. To explore this hypothesis, we identified a peptide inhibiting the VEGF165 binding to NRP-1 and we tested whether it was able to inhibit tumor growth and angiogenesis. To prove the target of peptide action, we assessed its effects on binding of radiolabeled VEGF165 to recombinant receptors and to cultured cells expressing only VEGFR-2 (KDR) or NRP-1. Antiangiogenic activity of the peptide was tested in vitro in tubulogenesis assays and in vivo in nude mice xenotransplanted in fat-pad with breast cancer MDA-MB-231 cells. Tumor volumes, vascularity and proliferation indices were determined. The selected peptide, ATWLPPR, inhibited the VEGF165 binding to NRP-1 but not to tyrosine kinase receptors, VEGFR-1 (flt-1) and KDR; nor did it bind to heparin. It diminished the VEGF-induced human umbilical vein endothelial cell proliferation and tubular formation on Matrigel and in co-culture with fibroblasts. Administration of ATWLPPR to nude mice inhibited the growth of MDA-MB-231 xenografts, and reduced blood vessel density and endothelial cell area but did not alter the proliferation indices of the tumor. In conclusion, ATWLPPR, a previously identified KDR-interacting peptide, was shown to inhibit the VEGF165 interactions with NRP-1 but not with KDR and to decrease the tumor angiogenesis and growth, thus validating, in vivo, NRP-1 as a possible target for antiangiogenic and antitumor agents.

Effects of maternal deprivation on the adrenocorticotrophic and gonadotrophic axes in the hypothalamo-pituitary unit of preweanling female sheep: the histomorphometric approach

This study was designed to investigate the histochemical effects of maternal deprivation on the adrenocorticotrophic and gonadotrophic axes in the hypothalamo-pituitary unit of preweanling lambs. Twelve-week-old female lambs were divided into either the control (lambs reared under undisturbed maternal conditions; n=3) or the maternally deprived group (lambs separated for three days from their dams; n=3). The corticotrophin-releasing hormone (CRH) and gonadotrophin-releasing hormone (GnRH) in the median eminence and the adenohypophyseal adrenocorticotrophin (ACTH), gonadotrophins (LH and FSH) and mRNAs for their beta-subunits were investigated using the immunohistochemistry or hybridohistochemistry. In maternally deprived lambs, the percentage of the area occupied by immunoreactive (ir)-CRH nerve terminals was lower (P<0.05) and the percentage of the adenohypophyseal area (PAA) occupied by ir-ACTH cells was higher (P<0.05) compared with the control lambs. In the hypothalamo-gonadotrophic axis of maternally deprived lambs the percentage of area occupied by ir-GnRH nerve terminals was higher (P<0.05) and the PAA occupied by ir-FSHbeta cells was lower (P<0.05) in comparison with controls. The PAA occupied by gonadotrophs detected using hybridohistochemistry was higher (P<0.05) for LHbeta-mRNA in contrast to a lower (P<0.05) percentage for FSHbeta-mRNA in maternally deprived lambs compared with those staying with dams. In conclusion, maternal deprivation affected the accumulation of CRH and ACTH. The different and more striking alterations in FSH synthesis and storage in comparison with those concerning LH were observed in maternally deprived lambs. Thus, rupture of the preweanling young-mother social contact can affect the gonadotroph population activity, especially that relating to FSH-producing cells in the infantile female sheep.

Integrative analysis of gene expression patterns predicts specific modulations of defined cell functions by estrogen and tamoxifen in MCF7 breast cancer cells

To explore the mechanisms whereby estrogen and antiestrogen (tamoxifen (TAM)) can regulate breast cancer cell growth, we investigated gene expression changes in MCF7 cells treated with 17beta-estradiol (E2) and/or with 4-OH-TAM. The patterns of differential expression were determined by the ValiGen Gene IDentification (VGID) process, a subtractive hybridization approach combined with microarray validation screening. Their possible biologic consequences were evaluated by integrative data analysis. Over 1000 cDNA inserts were isolated and subsequently cloned, sequenced and analyzed against nucleotide and protein databases (NT/NR/EST) with BLAST software. We revealed that E2 induced differential expression of 279 known and 28 unknown sequences, whereas TAM affected the expression of 286 known and 14 unknown sequences. Integrative data analysis singled out a set of 32 differentially expressed genes apparently involved in broad cellular mechanisms. The presence of E2 modulated the expression patterns of 23 genes involved in anchors and junction remodeling; extracellular matrix (ECM) degradation; cell cycle progression, including G1/S check point and S-phase regulation; and synthesis of genotoxic metabolites. In tumor cells, these four mechanisms are associated with the acquisition of a motile and invasive phenotype. TAM partly reversed the E2-induced differential expression patterns and consequently restored most of the biologic functions deregulated by E2, except the mechanisms associated with cell cycle progression. Furthermore, we found that TAM affects the expression of nine additional genes associated with cytoskeletal remodeling, DNA repair, active estrogen receptor formation and growth factor synthesis, and mitogenic pathways. These modulatory effects of E2 and TAM upon the gene expression patterns identified here could explain some of the mechanisms associated with the acquisition of a more aggressive phenotype by breast cancer cells, such as E2-independent growth and TAM resistance.

In vitro evaluation and biodistribution of a 99mTc-labeled anti-VEGF peptide targeting neuropilin-1

Neuropilins (NRP) are receptors of angiogenic vascular endothelial growth factor (VEGF). Their overexpression was correlated with tumor angiogenesis and growth suggesting that their specific targeting could provide a new marker of tumor progression. Here, we observed in vitro that new (99m)Tc-labeled derivative of anti-VEGF heptapeptide, ATWLPPR, binds to NRP1 but not to NRP2. Our radiotracer is stable up to 24 h in human serum and in cysteine challenge. But, its too low affinity and too fast extraction indicate further improvement to give a successful imaging of tumor in vivo.

A syndecan-4/CXCR4 complex expressed on human primary lymphocytes and macrophages and HeLa cell line binds the CXC chemokine stromal cell-derived factor-1 (SDF-1)

The stromal cell-derived factor-1 (SDF-1) is a CXC chemokine, which plays critical roles in migration, proliferation, and differentiation of leukocytes. SDF-1 is the only known ligand of CXCR4, the coreceptor of X4 HIV strains. We show that SDF-1 binds to high- and low-affinity sites on HeLa cells. Coimmunoprecipitation studies demonstrate that glycanated and oligomerized syndecan-4 but neither syndecan-1, syndecan-2, betaglycan, nor CD44 forms complexes with SDF-1 and CXCR4 on these cells as well as on primary lymphocytes or macrophages. Moreover, biotinylated SDF-1 directly binds in a glycosaminoglycans (GAGs)-dependent manner to electroblotted syndecan-4, and colocalization of SDF-1 with syndecan-4 was visualized by confocal microscopy. Glycosaminidases pretreatment of the HeLa cells or the macrophages decreases the binding of syndecan-4 to the complex formed by it and SDF-1. In addition, this treatment also decreases the binding of the chemokine to CXCR4 on the primary macrophages but not on the HeLa cells. Therefore GAGs-dependent binding of SDF-1 to the cells facilitates SDF-1 binding to CXCR4 on primary macrophages but not on HeLa cell line. Finally, an SDF-1-independent heteromeric complex between syndecan-4 and CXCR4 was visualized on HeLa cells by confocal microscopy as well as by electron microscopy. Moreover, syndecan-4 from lymphocytes, monocyte derived-macrophages, and HeLa cells coimmunoprecipitated with CXCR4. This syndecan-4/CXCR4 complex is likely a functional unit involved in SDF-1 binding. The role of these interactions in the pathophysiology of SDF-1 deserves further study.

Carboxymethyl benzylamide dextran inhibits angiogenesis and growth of VEGF-overexpressing human epidermoid carcinoma xenograft in nude mice

Vascular endothelial growth factor (VEGF) expression is elevated in a wide variety of solid tumours. Inhibition of VEGF activities is able to reduce angiogenesis and tumour growth. We have recently shown in vitro that carboxymethyl dextran benzylamide (CMDB7) prevents the binding of VEGF(165) to its cell surface receptors and thus inhibits VEGF activities on endothelial cells. In the present study, we explored the effects of CMDB7 on highly aggressive human epidermoid carcinoma A431 cells known to overexpress epidermal growth factor receptors (EGFRs) and produce a high amount of VEGF and a minor quantity of bFGF. In vitro, CMDB7 blocked the mitogenic activity of A431-conditioned medium on endothelial cells. Concerning A431 cells, CMDB7 inhibited their proliferation and the VEGF(165) binding to them. In vivo, administration of CMDB7 (10 mg kg(-1)) three times per week for 2 weeks inhibited the growth of A431 xenografts in nude mice by 73% as compared to the control group. Immunostaining of endothelial cells with mouse-specific GSL-1 lectin in tumour sections revealed that CMDB7 also inhibited the density of intratumour endothelial cells by 66%. These findings demonstrate that CMDB7 has an efficient antiangiogenic and antitumour action in vivo even when tumour cells produce a high level of VEGF and EGFRs.

Spatial organization of three-dimensional cocultures of adriamycin-sensitive and -resistant human breast cancer MCF-7 cells

Genetic and cellular heterogeneity is one of mechanisms involved in increasing tumour aggressiveness during neoplastic progression. Development of drug-resistant tumour cell subpopulations is a major problem in clinical oncology. Multi-drug resistant tumour cells survive when exposed to cytotoxic agents. Here, we studied in a three-dimensional (3D) coculture system, called "ex vivo nodules", how drug-resistant and sensitive tumour cells settle down in a 3D space. For this, we cocultured adriamycin-sensitive (MCF-7S) and -resistant (MCF-7R) human breast cancer cells in long term nodules. We showed that both types of cells are able to grow separately or in coculture until five weeks in spheroidal forms. MCF-7R cells did not loose their multi-drug resistance when cultured in nodules as measured by RT-PCR. Curiously, the exterior aspects of mixed (MCF-7S/ MCF-7R) nodules and MCF-7R nodules were similar whereas MCF-7S nodules were completely different. Nevertheless, morphologically these three nodule types were distinct, in particular in their density. Immunostaining showed that in mixed nodules, MCF-7R cells were arranged at the periphery, whereas the MCF-7S cells are in the central part of the nodules. Even if the mechanism of this arrangement remained unclear, this work shows that three-dimensional cell culture is well adapted to the study of the relationships between adhesion mechanisms and drug-resistance.

Inhibition of epidermoid carcinoma A431 cell growth and angiogenesis in nude mice by early and late treatment with a novel dextran derivative

We investigated the effect of a new dextran derivative, phenylacetate carboxymethyl benzylamide dextran (NaPaC), on epidermoid carcinoma A431 cells secreting a large quantity of angiogenic factor, vascular endothelial growth factor (VEGF). In vitro, NaPaC inhibited the proliferation of A431 cells (IC(50)=5 micro M). Also, NaPaC decreased the binding of radiolabelled VEGF(165) to endothelial cells (IC(50)=0.2 micro M). In vivo, we explored the effects of NaPaC (15 mg kg(-1)) on A431 xenograft growth starting the drug administration at the time of tumour cell inoculation (early treatment) and 1 week later, when tumours were well established (late treatment). Early treatment was more efficient on tumour inhibition (70% vs control) than late treatment (50% vs control). Early and late NaPaC-treatment increased the aponecrosis in tumour by 70 and 30%, respectively. Whatever treatment, NaPaC inhibited the intratumour endothelial cell density in the same manner. In contrast, vessel area was decreased only when NaPaC was injected early (35%). These results show that NaPaC has a potent inhibitory effect, dependent on treatment outset, on epidermoid carcinoma growth associated with an intratumour microvascular network diminution and an aponecrosis increase. As this drug is nontoxic at efficient dose, it offers interesting perspectives for the therapy of malignant lesions.

The effect of dietary protein restriction on the secretion of LH and FSH in pre-pubertal female lambs

The effect of restricted dietary protein on the synthesis, storage and release of LH and FSH was studied in pre-pubertal female lambs. The experiment started when the lambs were aged 12 weeks and weighed 26.0+/-1.6 kg. It was conducted for 25 weeks. The lambs were fed isocaloric diets containing either a restricted level of crude protein (8% CP; n=6; treatment R) or an elevated one (18% CP; n=4; treatment E). At 37 weeks of age and before the first oestrous cycle, blood samples were collected over 6 h at 10 min intervals for LH assay. The lambs were slaughtered and their brains recovered and fixed in situ. Immuno-reactive (IR) LH and FSH cells were localised by immunohistochemistry techniques. Messenger RNA analyses used by non-isotope in situ hybridisation with sense and anti-sense riboprobes from beta subunits of LH and FSH cDNA clones. Data were generated using computer analysis to measure the proportion of IR and/or hybridising cells and their optical density for immuno-staining and hybridisation signal. Plasma LH was measured by RIA. The daily live-weight gains were 56.5+/-13.1 g and 97.8+/-14.3 g for R and E lambs, respectively (P<0.05), so that final weights at slaughter were 36.1+/-1.97 kg and 39.1+/-3.44 kg, respectively (P<0.05). The number of cells expressing LH beta mRNA and the optical density of this hybridisation signal was significantly (P<0.001) lower in the R lambs but the number of IR LH positive cells was higher (P<0.001) than for the E lambs. The concentration of LH in the plasma of R sheep was lower (P<0.05) than the E group and this response was associated with a decrease (P<0.05) in LH pulse frequency and amplitude. Dietary protein concentration appeared to have no effect on the IR in FSH cells or on the expression of FSH beta mRNA. In summary, the low protein diet influenced the body weight and weight gain of growing lambs and exerted an inhibitory effect on the synthesis and the release of LH in the pituitary gonadotrophs. No such effect was observed for FSH. It was concluded that the protein concentration of the diet consumed during the growth of female lambs may be an important modulator of processes leading to the pre-pubertal rise in LH.

Aponecrotic, antiangiogenic and antiproliferative effects of a novel dextran derivative on breast cancer growth in vitro and in vivo

1. Since the sodium phenylacetate (NaPa) was reported to enhance the inhibitory effect of carboxymethyl benzylamide dextran (CMDB) on the breast cancer growth, we performed the esterification of CMDB with NaPa to obtain a new drug carrying the characteristics of these two components. A new molecule, phenylacetate carboxymethyl benzylamide dextran, was named NaPaC. 2. We investigated in vitro and in vivo the effects of NaPaC on MCF-7ras cell growth as well as its apoptotic and antiangiogenic effects in comparison to NaPa and CMDB. In addition, we assessed in vitro the antiproliferative effects of these drugs on other breast cancer cells, including MDA-MB-231, MDA-MB-435 and MCF-7. 3. In vitro, NaPaC inhibited MCF-7ras cell proliferation by 40% at concentration lower than that of CMDB and NaPa (12 microM vs 73 microM and 10 mM). IC(50)s were 6 and 28 microM for NaPaC and CMDB, respectively. The similar results were obtained for three other breast cancer cell lines. NaPaC reduced the DNA replication and induced cell recruitment in G(0)/G(1) phase more efficiently than its components. Moreover, it induced a cell death at concentration 1000-fold lower than NaPa. 4. In vivo, CMDB (150 mg kg(-1)) and NaPa (40 mg kg(-1)) inhibited the MCF-7ras tumour growth by 37 and 57%, respectively, whereas NaPaC (15 mg kg(-1)) decreased tumour growth by 66% without toxicity. 5. NaPa or CMDB reduced the microvessel number in tumour by 50% after 7 weeks of treatment. NaPaC had the same effect after only 2 weeks. After 7 weeks, it generated a large necrosis area without detectable microvessels. In vitro, NaPaC inhibited human endothelial cell proliferation more efficiently than CMDB or NaPa. NaPaC interacts with vascular endothelial growth factor as observed by affinity electrophoresis. 6. NaPaC acts like NaPa and CMDB but in more potent manner than components used separately. Its antiproliferative, aponecrotic and anti-angiogenic actions make it a good candidate for a new anti-cancer drug.

Intracerebroventricular infusion of neuropeptide Y up-regulates synthesis and accumulation of luteinizing hormone but not follicle stimulating hormone in the pituitary cells of prepubertal female lambs

Neuropeptide Y (NPY) is a putative neuroregulator of the reproductive axis in the central nervous system. In this study we evaluated the effects of central infusion of exogenous NPY on the secretory activity of pituitary gonadotrophic cells in prepubertal lambs. Immature female Merino sheep (n=12) were infused of Ringer solution (control) or 50 microg of NPY to the third ventricle for 5 min and then slaughtered 3 h later. Immunoreactive luteinizing hormone (LH) and follicle stimulating hormone (FSH) cells were localised by immunohistochemistry using antibody raised against LHbeta and FSHbeta. Messenger RNA analyses were performed by in situ hybridisation using sense and antisense riboprobes produced from beta subunits of LH and FSH cDNA clones. The results were generated by computer image analysis to determine the area fraction occupied by immunoreactive and/or hybridising cells and optical density for immunostaining and hybridisation signal. LH in the blood plasma was determined by radioimmunoassay. It was found, that in the lambs infused with NPY the area fraction and optical density for immunoreactive LH cells and mRNA LHbeta-expressing cells increased significantly (P<0.001), compared to the vehicle-infused animals. The concentration of LH in the blood plasma did not differ between control and treated groups. The NPY infusions had no effect on the immunoreactivity of FSH cells or on expression of mRNA for FSHbeta. In conclusion we suggest that NPY may be an important component of mechanisms stimulating the synthesis and storage but not the release of LH in the pituitary gonadotrophs from prepubertal female sheep. In addition, this effect is specific for LH, no such effect was apparent on FSH.

Vascular endothelial growth factor 165 (VEGF(165)) activities are inhibited by carboxymethyl benzylamide dextran that competes for heparin binding to VEGF(165) and VEGF(165).KDR Complexes

We have previously shown that carboxymethyl dextran benzylamide (CMDB7), a heparin-like molecule, inhibits the growth of tumors xenografted in nude mice, angiogenesis, and metastasis by altering the binding of angiogenic growth factors, including platelet-derived growth factor, transforming growth factor beta, and fibroblast growth factor 2, to their specific receptors. In this study, we explore the effect of CMDB7 on the most specific angiogenic growth factor, vascular endothelial growth factor 165 (VEGF(165)). We demonstrate here that CMDB7 inhibits the mitogenic effect of VEGF(165) on human umbilical vein endothelial cells (HUV-ECs) by preventing the VEGF(165)-induced VEGF receptor-2 (KDR) autophosphorylation and consequently a specific intracellular signaling. In competition experiments, the binding of (125)I-VEGF(165) to HUV-ECs is inhibited by CMDB7 with an IC(50) of 2 microm. Accordingly, CMDB7 inhibits the cross-linking of (125)I-VEGF(165) to the surface of HUV-ECs, causing the disappearance of both labeled complexes, 170-180 and 240-250 kDa. We show that CMDB7 increases the electrophoretic mobility of VEGF(165), thus evidencing formation of a stable complex with this factor. Moreover, CMDB7 reduces the (125)I-VEGF(165) binding to coated heparin-albumin and prevents a heparin-induced increase in iodinated VEGF(165) binding to soluble (125)I-KDR-Fc chimera. Concerning KDR, CMDB7 has no effect on (125)I-KDR-Fc electrophoretic migration and does not affect labeled KDR-Fc binding to coated heparin-albumin. In the presence of VEGF(165), (125)I-KDR-Fc binding to heparin is enhanced, and under these conditions, CMDB7 interferes with KDR binding. These data indicate that CMDB7 effectively inhibits the VEGF(165) activities by interfering with heparin binding to VEGF(165) and VEGF(165).KDR complexes but not by direct interactions with KDR.

Sodium phenylacetate enhances the inhibitory effect of dextran derivative on breast cancer cell growth in vitro and in nude mice

Sodium phenylacetate (NaPa) and carboxymethyl benzylamide dextran derivative (CMDB(LS4)) are able to inhibit growth of breast tumour cells. In this study, we explored whether the combination of NaPa and CMDB(LS4)may enhance their respective inhibitory effects on the MCF-7ras cell growth in vitro and in vivo. NaPa inhibited MCF-7ras cell proliferation by reducing the DNA replication concomitantly with a recruitment of cells in G0/G1 phase and by inducing apoptosis in a dose- and time-dependent manner. The addition of CMDB(LS4)potentiated the NaPa antiproliferative effect in the manner dependent on the ratio of CMDB(LS4)and NaPa concentrations. In nude mice, CMDB(LS4)(150 mg kg(-1)) or NaPa (40 mg kg(-1)) administrated twice a week, for 7 weeks inhibited MCF-7ras xenograft growth by 40% and 60%, respectively. The treatment by both, CMDB(LS4)and NaPa, decreased tumour growth by 83% without any toxicity. To better understand the mechanism of NaPa and CMDB(LS4)action we assessed their effect on mitogenic activity of MCF-7ras conditioned medium (CM) on BALBC/3T3 fibroblasts. CMDB(LS4)added to the CM, inhibited its mitogenic activity whereas NaPa had an anti-mitogenic effect when CM was prepared from MCF-7ras cells pretreated with NaPa. Thus, the antiproliferative effects of NaPa and CMDB(LS4)involve 2 different mechanisms explaining, at least in part, the possible synergism between them. Overall, this study points to the potential use of a combination of dextran derivatives with NaPa to inhibit the breast tumour growth.

Amiodarone has exclusively non-genomic action on cardiac beta-adrenoceptor regulation

The antiarrhythmic drug amiodarone down-regulates the density of cardiac beta-adrenoceptors behaving as a triiodothyronine (T(3)) antagonist. It is still unclear if amiodarone acts at the nuclear (genomic) and/or the non-genomic levels. Using Northern blot analysis, we showed that the amiodarone had no effect on the increase of beta(1)-adrenoceptor mRNA level induced by the T(3)-administration in the heart of thyroidectomised rats. Thus, our results suggest that amiodarone has no genomic effect. Consequently, we investigated whether amiodarone down-regulation of beta-adrenoceptor number in T(3)-stimulated cardiomyocytes could be explained by changes in the rate of cell surface receptor protein turnover. Indeed, the binding studies of cyclohexidemide-treated cells showed that amiodarone suppressed the T(3)-induced decrease in the rate of the cell surface receptor disappearance. In conclusion, our findings indicate that the modulation of cardiac beta-adrenoceptor density by amiodarone involves only non-genomic targets required in T(3)-dependent regulation of the cell surface beta-adrenoceptor turnover.

Regulation of beta 1- and beta 3-adrenergic agonist-stimulated lipolytic response in hyperthyroid and hypothyroid rat white adipocytes

1. This study examined the effects of thyroid status on the lipolytic responses of rat white adipocytes to beta-adrenoceptor (beta-AR) stimulation. The beta 1- and beta 3-AR mRNAs and proteins were measured by Northern and saturation analyses, respectively. Glycerol production and adenyl cyclase (AC) activity induced by various non-selective and selective beta 1/beta 3-AR agonists and drugs which act distal to the receptor in the signalling cascade were measured in cells from untreated, triiodothyronine (T3)-treated and thyroidectomized rats. 2. The beta 3-AR density was enhanced (72%) by T3-treatment and reduced (50%) by introduction of a hypothyroid state while beta 1-AR number remained unaffected. The beta 1- and beta 3-AR density was correlated with the specific mRNA level in all thyroid status. 3. The lipolytic responses to isoprenaline, noradrenaline (beta 1/beta 3/beta 3-AR agonists) and BRL 37344 (beta 3-AR agonist) were potentiated by 48, 58 and 48%, respectively in hyperthyroidism and reduced by about 80% in hypothyroidism. 4. T3-treatment increased the maximal lipolytic response to the partial beta 3-AR (CGP 12177) and beta 1-AR (xamoterol) agonists by 234 and 260%, respectively, increasing their efficacy (intrinsic activity: 0.95 versus 0.43 and 1.02 versus 0.42). The maximal AC response to these agonists was increased by 84 and 58%, respectively, without changing their efficacy. 5. In the hypothyroid state, the maximal lipolytic and AC responses were decreased with CGP (0.17 +/- 0.03 versus 0.41 +/- 0.08 mumol glycerol/10(6) adipocytes; 0.048 +/- 0.005 versus 0.114 +/- 0.006 pmol cyclic AMP min-1 mg-1) but not changed with xamoterol. 6. The changes in lipolytic responses to postreceptor-acting agents (forskolin, enprofylline and dibutenyl cyclic AMP, (Bu)2cAMP) suggest the modifications on receptor coupling and phosphodiesterase levels in both thyroid states. 7. Thyroid status affects lipolysis by modifying beta 3-AR density and postreceptor events without changes in the beta 1-AR functionality.

Tissue-specific pattern of variant transcripts of the human gonadotropin-releasing hormone receptor gene

The expression pattern of the GnRH receptor was investigated in a variety of normal and neoplastic human tissues by RT-PCR-Southern blotting. In addition to the full-length cDNA (sb1), we identified two other transcripts: the first (sb2) was characterized by a 128 bp deletion as previously described; the second was an unexpected finding composed of a shorter cDNA (sb3), the sequence of which revealed a 220 bp deletion corresponding in size to exon 2. These three transcripts were found in normal pituitary and pituitary adenomas, and in granulosa tumors, but not in testis, where sb2 was lacking. Only sb1 was expressed in normal, fibrocystic and malignant breast tissue. No transcript with a full-length region was found in endometrium, intestine or lymphocytes. This is the first report that shows that splicing of the gonadotropin-releasing hormone receptor gene is tissue dependent. We also determined the intron-exon nucleotide sequence of the gene and identified an MaeIII polymorphic site in exon 1 created by a silent C453T transition found in 10% of unrelated French whites.

Uptake of liposome-encapsulated 99Tcm-MIBI by sensitive and multidrug-resistant tumour cell lines

It is well established that accumulation of 99Tcm-sestamibi (99Tcm-MIBI) is much higher in sensitive than multidrug-resistant tumour cells expressing the permeability glycoprotein 170 (Pgp 170) as well as a multidrug-resistance related protein (MRP). Thus 99Tcm-MIBI is a good candidate for diagnosing the multidrug-resistance phenotype by in vivo imaging. However, the blood clearance of 99Tcm-MIBI is too rapid to achieve optimal accumulation in tumours and uptake in the liver, spleen, heart and muscle is too high for it to be an excellent in vivo tumour tracer. One way of prolonging the bioavailability of 99Tcm-MIBI is to use liposomes which do not affect its accumulation in tumour cells. We explored this possibility in vitro using two sensitive and five resistant cell lines, two of them expressing Pgp 170 and three others over-expressing MRP. 99Tcm-MIBI was incorporated into liposomes prepared by thin film hydration with phosphate-buffered saline using distearoyl phosphatidyl choline, distearoyl phosphatidyl ethanolamine and cholesterol in a ratio of 1.85:0.15:1.00. Liposome diameter was 97.9 +/- 4.5 nm as determined by dynamic light scattering. 99Tcm-MIBI uptake was quantified by measuring radioactivity retained in the cells incubated at 37 degrees C with liposome-encapsulated 99Tcm-MIBI or with free radiotracer in the presence of empty liposomes. In both experimental cases, 99Tcm-MIBI accumulation was similar to that obtained in the presence of free 99Tcm-MIBI only: it was much higher in sensitive than in resistant Pgp 170-positive and MRP-positive cells. Encapsulation in liposomes does not alter the potency of 99Tcm-MIBI to distinguish the sensitive and resistant tumour cells. Our results suggest that future studies should assess the usefulness of the encapsulated form of 99Tcm-MIBI for in vivo imaging of tumours.

Involvement of glutathione in loss of technetium-99m-MIBI accumulation related to membrane MDR protein expression in tumor cells

It was reported recently that 99mTc-hexakis-2-methoxyisobutyl isonitrile (MIBI) uptake is drastically reduced in cancer cells that express the multidrug resistance (MDR) product, Pgp 170 kDa (Pgp), suggesting that 99mTc-MIBI is a transport substrate for this transmembrane glycoprotein. In our study, we explored if another pump, a multidrug resistance-associated protein (MRP), could affect 99mTc-MIBI uptake. In addition, we studied the involvement of intracellular glutathione (GSH) as a modulator of 99mTc-MIBI uptake by both Pgp and MRP proteins.

METHODS

MDR1 and MRP gene expression in seven human tumor cell lines was determined on a transcriptional level by reverse transcriptase polymerase chain reaction and on a protein level using immunocytochemistry. Technetium-99m-MIBI uptake was quantified by measuring radioactivity retained in the cells incubated at 37 degrees C in the presence or absence of buthionine sulfoximine (BSO), which depletes cellular GSH. The cellular GSH content was determined with Ellman's reagent.

RESULTS

Cell lines were classified according to their phenotypic characteristics: 1/MRP-/Pgp-: breast cancer cells (MCF7), lung carcinoma cells (H69S) and mouth epidermoid tumor cells (KB 3.1), 2/MRP-/Pgp+: MCF7 mdr+, KBA.1; and 3/MRP+/Pgp-: small-cell lung carcinoma (H69 AR and A 549). Technetium-99m-MIBI uptake was significantly lower in cells expressing MRP as well as Pgp compared to MRP/Pgp cells. Depletion of GSH by BSO resulted in an increase of 99mTc-MIBI uptake in multidrug resistant cells overexpressing MRP but not expressing Pgp.

CONCLUSION

Technetium-99m-MIBI is extruded by both Pgp and MRP efflux pumps. However, MRP action is indirect and involves intracellular GSH for a presumed interaction with the 99mTc-MIBI before its effLux. Technetium-99m-MIBI seems to be a good candidate for a noninvasive marker to diagnose MDR1 related to Pgp and MRP expression in tumors of different origin.

The genes for gonadotropin-releasing hormone and its receptor are expressed in human breast with fibrocystic disease and cancer

While gonadotropin-releasing hormone (GnRH) or GnRH receptor (GnRHR) have been reported to exist in tissues other than brain and pituitary, there is no report concerning co-expression of GnRH and GnRHR in human breast tissues. To address this question, we have examined whether mRNA for GnRH as well as GnRHR was present in different human breast samples, by employing the reverse transcription-polymerase chain reaction (RT-PCR) protocol followed by Southern blotting of the PCR products. Coexpression of GnRH and GnRHR genes was further confirmed by dot blot hybridization using appropriate [32P]-labeled probes. We thus tested fibrocystic breast (4 cases), invasive ductal carcinomas (6 cases) and 1 adjacent non-neoplastic tissue. GnRHR and GnRH mRNAs were found in all actin-positive samples including malignant as well as nonmalignant tissues. Quantitative determinations of mRNA did not reveal significant differences between malignant and non-malignant breast samples for either GnRH or GnRHR gene expression. Our data show that neither gene was overexpressed in the breast cancer samples compared with normal breast tissue. Since GnRH agonists inhibit breast epithelial cell growth, the presence of GnRHR mRNA suggests that GnRH may specifically affect breast cell growth. Our data thus raise the possibility of an autocrine/paracrine role for GnRH in human mammary gland.

Technetium-99m-sestamibi uptake by human benign and malignant breast tumor cells: correlation with mdr gene expression

Early diagnosis of multidrug-resistance (MDR) development is extremely important for the judicious choice of treatment protocols in breast cancer chemotherapy. In this study, the mechanism of 99mTc-sestamibi uptake by nine human breast tumor cell lines was analyzed as a function of P-glycoprotein (PgP) expression.

METHODS

Technetium-99m-sestamibi radioactivity incorporation into the cells was determined after different times of incubation at 37 degrees C. We analyzed the mechanism of 99mTc-sestamibi uptake as follows: (a) effect of temperature (4 degrees C); (b) influence of extracellular 99mTc-sestamibi concentration; and (c) competitive inhibition of cell uptake with cold 99mTc-sestamibi. Technetium-99m-sestamibi uptake was compared to the level of PgP determined by Western blotting. The PgP reversing effect of verapamil was evaluated at different drug concentrations (50, 200, 500 microM).

RESULTS

Technetium-99m-sestamibi uptake plateaued at 60 min, which was 14 times lower at 4 degrees C than at 37 degrees C and was directly proportional to the extracellular concentration between 0.3 and 10 nM. Technetium-99m-sestamibi percentage uptake by cells expressing nonimmunodetectable levels of PgP was significantly higher (7.3% +/- 0.6% (s.d.) to 14.9% +/- 1.9%) than that by cells expressing high PgP levels (0.7% +/- 0.4%, p < 0.001). In the presence of verapamil, a known reverser of PgP functions, 99mTc-sestamibi uptake was increased by a factor of 2 in cells expressing no detectable levels of PgP and by a factor of 12 in cells with high PgP levels.

CONCLUSION

Technetium-99m-sestamibi uptake by these breast tumor cells is energy-dependent but not specific. These data suggest that 99mTc-sestamibi imaging may be used as a noninvasive technique to diagnose the presence of MDR in breast tumors in vivo.

Evidence for a growth effect of epidermal growth factor on MDA-MB-231 breast cancer cells

MDA-MB-231 is a breast epithelial cell line which possesses large amounts of epidermal growth factor (EGF) receptor on its cell surface but does not respond to EGF under standard culture conditions. 8-bromo-cyclic AMP (8Br-cAMP) and cholera-toxin treatments inhibit its growth by increasing its intracellular cAMP level. However, when inhibited in this way, MDA-MB-231 remains unresponsive to EGF. Similar effects--cAMP accumulation and inhibition of cell growth--are produced by forskolin. In addition, this substance specifically blocks MDA-MB-231 cells in G1 phase of the cell cycle. EGF is able to reverse the effect of forskolin on cell proliferation and prevents accumulation of cells in G1 phase without any change of cAMP level. Thus, only when inhibiting cell growth with forskolin does a mitogenic effect of EGF become evident. As cAMP is increased to a similar degree by all three compounds, yet only the effect of forskolin is antagonised by EGF, we suggest that a non-cAMP-mediated effect of forskolin must be considered to explain this effect. In contrast, the mitogenic effect of EGF on the NPM14T4/9 breast epithelial cell line does not change in the presence of forskolin.

Selection of a highly tumorigenic breast cancer cell line sensitive to estradiol to evidence in vivo the tumor-inhibitory effect of butyrate derivative Monobut-3

To increase butyric acid mean residence time in vivo, we have produced a stable butyric acid derivative. Monobut-3. Recently, we have described that Monobut-3 is able to induce phenotypic changes in human mammary tumor cells in vitro. In this study, we explore the in vivo effect of Monobut-3. Human breast tumor cell-lines did not easily produce in vivo xenografts, thus, MCF-7 cells required exogenous 17 beta-estradiol to grow and to form in vivo xenografts. To evaluate in vivo and anti-tumor effects of monobut-3 without exogenous 17 beta-estradiol addition, we have established MCF-7 variant cells, highly tumorigenic MCF-7vht, in which transfection of ras oncogene induced a bypass of estrogen requirement but did not delete the presence of functional estrogen receptor (ER). Monobut-3 inhibited growth of this variant by about 90% at 4 mM and reduced 17 beta-estradiol cell growth stimulation. In vivo, in absence of 17 beta-estradiol, 2 mg per mouse monobut-3 decreased tumor take by about 25% and tumor growth by about 50% in nude mice. This is the first experimental demonstration of an in vivo antitumoral effect of a butyric acid derivative alone on a solid human tumor. These data suggest that this compound does not only act by reducing of 17 beta-estradiol stimulation but it also has an 17 beta-estradiol-independent effect. Absence of toxicity and its antiproliferative effects could suggest its use in clinical treatment of well differentiated carcinoma.

[Recent data on the gonadoliberin receptor and the neuropeptide control mechanisms for gene expression of gonadotropin hormones]

GNRH plays a pivotal role in the neurohormonal control of reproduction by promoting hte secretion of pituitary gonadotrophins, LH and FSH. GnRH also stimulates the synthesis of constitutive gonadotrophin subunits alpha and beta and its own receptor number. Gonadotrophin synthesis appears to be regulated by GnRH through various molecular mechanisms that include, in a complementary and in some cases differential manner, enhanced transcriptional activity of subunit genes and polyadenylation of transcripts. The latter is known to result in increased stability and/or translational activity of mRNAs. These effects of GnRH are mimicked by the direct activation of protein kinases A and C, two different but possibly interconnected signalling pathways that may account for the pleiotropic and concerted alterations of both synthesis and release of gonadotrophins. GnRH operates on the gonadotropic cell level via a transmembrane, G-protein coupled receptor, the structure of which has recently been determined by molecular cloning. This receptor differs from the other members of hte super-family essentially by a rather short length (only 327-328 amino acids) and a truncated carboxyterminus. Recent experiments suggest a genomic control of the GnRH receptor synthesis, especially by GnRH itself, the importance, and role of which remains to be established for the pituitary gonadotropic function.

Molecular heterogeneity of somatostatin analogue BIM-23014C receptors in human breast carcinoma cells using the chemical cross-linking assay

Distinct proteins complexed with somatostatin and the somatostatin analogue BIM-23014C were revealed in human breast cancer cells using the cross-linking assay. One BIM-23014C-specific complex (Mr 57,000) was observed in MCF-7 (monolayer, nodule, and tumor) and T47D. Growth inhibition of MCF-7 tumor xenografts by BIM-23014C was dose related in the 6-day subrenal capsule assay. Three complexes (Mr 27,000, 42,000, and 57,000) were detected in MDA-MB-231, and no complex was visible in HBL-100. No correlation was found between receptors for BIM-23014C and epidermal growth factor in these lines. Twenty-seven of 30 human breast tumors (90%) had at least one BIM-23014C receptor. Sixteen had three complexes (Mr 27,000, 42,000, and 57,000). Six had the two complexes (Mr 27,000 and 57,000), two had Mr 42,000 and 57,000 complexes, two had just the Mr 27,000 complex, and one had just the Mr 42,000 complex. The presence of the three BIM-23014C receptors was positively correlated (P less than 0.05) to the low amount of sex steroid receptors (less than 20 fmol/mg) [seven of eight (estrogen receptor negative, progesterone receptor negative) versus four of 14 (estrogen receptor positive, progesterone receptor positive)]. Another positive correlation was established between the absence of progesterone receptors and the presence of these three complexes [12 of 16 (progesterone receptor negative) versus four of 14 (progesterone receptor positive)]. This high percentage of BIM-23014C receptor-positive biopsies and its inhibitory activity would support its clinical potential for the treatment of breast cancer.

Growth of human breast cancer cell lines is inhibited by the somatostatin analog BIM23014

Somatostatin has been shown to lower plasma levels of various hormones and growth factors involved in regulation of the growth of human breast cells. In the present study we examined the ability of the somatostatin octapeptide analog BIM23014 to modulate the in vitro growth of five human breast cell lines: HBL100, Hs578T, MDAMB231, T47D, and MCF7. BIM23014 inhibited the growth of the two steroid-dependent cell lines, MCF7 and T47D, in a dose-related manner. This inhibitory effect was only observed when MCF7 and T47D cells were cultivated in medium containing steroid-depleted serum. The growth of a MCF7 variant capable of growth in serum-free medium was also inhibited by BIM23014, indicating that serum factors are not required for this inhibition. In the serum-free medium, the addition of estradiol before or during treatment with BIM23014 abolished its inhibitory effects on cell growth. The studies including time course, competitive inhibition, and cross-linking of iodinated BIM23014 to its receptor revealed a specific binding on MCF7 cells and showed a single 57,000 mol wt protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results support the hypothesis that BIM23014 inhibits the growth of steroid-receptor positive cells of human breast cancers through its own receptor in estradiol-free conditions.

[Cyclic AMP: role in the synthesis and release of luteinizing hormone]

GnRH is capable of inducing an increase in cyclic AMP (AMPc) production in the anterior pituitary gland. However, this intracellular messenger is not involved in the mechanisms leading to acute release of gonadotropins. Using anterior pituitary cells in culture, we recently found that AMPc, like GnRH, stimulated the expression of genes encoding for LH and consequently increased the synthesis of LH subunits. To reevaluate the role of AMPc in the secretion of pituitary gonadotropins, we first studied the effects of 8-Br-AMPc, a permeant AMPc analog, on LH release during a 48-hour period. Direct activation of protein kinases A by 8-Br-AMPc substantially stimulated LH release, to values as high as those seen with GnRH under the optimal conditions used in this experiment. However, kinetics were different, with GnRH inducing a rapid rise in LH and 8-Br-AMPc causing a gradual increase after a five-hour lag. We also studied the effects of 8-Br-AMPc on the release of neosynthesized subunits. Pituitary cells were incubated with 35S-Met, and labeled alpha and LH beta polypeptides were recovered in parallel from the cells and medium. We observed that 8-Br-AMPc stimulated not only LH synthesis but also release of newly synthesized LH subunits, in this respect 8-Br-AMPc was more effective than GnRH. After five hours incubation with 1.5 mM 8-Br-AMPc, 95% of the alpha subunit and 40% of the LH beta subunit that had been newly synthesized were released into the medium, whereas the corresponding figures with exposure to 10 nM GnRH were 80% and 15% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[Focus on the biogenesis of hypophyseal gonadotropins]

We have studied the regulation of the biosynthesis of pituitary gonadotropins in the rat by gonadal steroids and a hypothalamic hormone, GnRH. The methodology used for studying the action of steroids, was either cell-free translation of pituitary messenger RNAs, or hybridization (Northern blot) with synthetic oligodeoxynucleotides (ODN), and for studying the effect of GnRH, primary anterior pituitary cell culture. Our results show that gonadectomy increases and injection of gonadal steroids into gonadectomized rats diminishes the rate of synthesis of the gonadotropin subunit precursors. Progesterone acts only after induction of its pituitary receptors in ovariectomized rats with estradiol benzoate. Thyroxine modulates the action of steroids. Hybridization experiments suggest that gonadal steroids act on the expression of genes encoding the precursors of gonadotropin subunits. GnRH significantly increases incorporation of the labeled amino acids into polypeptide chains of both alpha and LH beta subunits. Intracellular mediators of hormone action, such as cyclic AMP and diacylglycerols, mimic the stimulatory action of GnRH on the synthesis of LH subunits. However, we have no evidence that these products intervene in the effect of GnRH on the LH subunit synthesis. In conclusion, the synthesis of LH and FSH subunits is regulated, with opposite effects, by gonadal steroids which exert their negative control at the genomic level and by GnRH which proceeds via different, yet unknown mechanisms.

[Stimulation of LH gene expression by GnRH. Role of protein kinases A and C]

Using anterior pituitary cells in culture, incubated in the presence of [35S] Met, we have previously demonstrated that GnRH stimulates the synthesis of LH polypeptide chains, an effect which was reproduced in a non additive manner by direct activation of protein kinases A and C (by cyclic AMP or diacylglycerol analogues, respectively), and abolished by actinomycin D. The respective roles of GnRH and protein kinases A and C in the stimulation of LH subunit gene expression was examined in the present study by evaluating the effects on the cellular levels of alpha and LH beta mRNAs of optimal concentrations of Buserelin (0.1 nM) an undegradable GnRH analogue, cholera toxin (6 nM) a cyclic AMP (AMPc) generator and 12-O-tetradecanoyl phorbol 13-acetate (TPA) a diacylglycerol analogue. The specific mRNAs were quantified by densitometry analysis of Northern blot hybridization using 32P-labeled single strand cDNAs. We observed TPA, like Buserelin, increased LH mRNA levels in a very similar manner, the alpha mRNA increasing 1.8 - 2.5 fold and the LH beta mRNA 1.4 - 1.7 fold after 5 h culture and 3.0 - 3.5 fold and 2.2 - 2.4 fold respectively, after 24 h. In the presence of cholera toxin, the changes were more rapid, the highest values being reached at 5 h (8.6 fold increase for alpha and 4.0 fold for LH beta mRNA). LH, radioimmunoassayed in parallel in the cell medium, increased 5.9 fold after 5 h and 7.1 fold after 24 h culture in the presence of Buserelin, and 2.9 fold and 5.4 fold, respectively, in the presence of TPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic adenosine monophosphate and phorbol ester, like gonadotropin-releasing hormone, stimulate the biosynthesis of luteinizing hormone polypeptide chains in a nonadditive manner

We have previously reported that GnRH stimulates the synthesis of both the alpha- and beta-polypeptide chains of LH. In the present study, in order to investigate the mechanisms involved in the GnRH regulation of LH subunit synthesis, we have explored the effects of cAMP and a phorbol ester [12-O-tetradecanoyl phorbol 13-acetate (TPA)] using anterior pituitary cells in primary culture incubated in the presence of [35S]methionine. The radioactivity incorporated into alpha and LH beta immunologically related polypeptides was measured after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the labeled material immunoextracted from cells and media with specific antisera. The cAMP analog 8-Br-cAMP (at concentrations 0.25-2 mM), the cholera toxin (6-60 nM), and forskolin (10-100 microM) induced, like GnRH, an increase in the [35S]methionine incorporation into alpha- and LH beta-subunits. On the other hand, TPA (50-100 nM) also enhanced the synthesis of LH subunits. After a 5-h incubation in the presence of GnRH, 8-Br-cAMP, and TPA in different combinations, no cumulative effect was observed. These results demonstrate that intracellular cAMP and TPA are potent activators of both alpha- and LH beta-polypeptide chain synthesis, suggesting that cAMP as well as diacylglycerols may act as intracellular mediators of the GnRH effect on LH subunit synthesis.

Detection of a lag phase in gonadotropin-releasing hormone stimulated synthesis of lutropin peptide chains in cultured rat anterior pituitary cells

We have studied the time course (0-5h) of the stimulatory effect of the hypothalamic gonadotropin-releasing hormone (GnRH) on the biosynthesis of lutropin (LH) polypeptide chains, as measured by the incorporation of [35S] methionine into proteins synthesized in cultured rat anterior pituitary cells in the absence or presence of 10nM GnRH. Labeled polypeptides, immunologically related to LH subunits alpha and beta, were isolated by specific immunoprecipitation, analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, then revealed by fluorography and quantified by counting the excised bands. This methodology allowed us to detect the radioactivity incorporated into LH subunits after less than 15 min of incubation. During first 1h of the time-course the quantity of [35S]Met incorporated into both alpha and LH beta subunits was not increased by the presence of GnRH in the incubation medium. A significant increase in the incorporation of radioactivity into LH subunits was observed after 2h of GnRH treatment. However, the increase in LH release into the medium in response to GnRH, as measured by RIA, was immediate. These data demonstrate that GnRH-stimulated synthesis of LH polypeptide chains occurs after a lag of approximately 1h and involves mechanisms different from those governing the stimulation of LH release.

Several intermediate forms in the processing of rat lutropin subunits as shown by sodium dodecyl sulphate polyacrylamide gel electrophoresis

To study the biosynthesis in situ of lutropin (LH) subunits, anterior pituitary cells in culture were employed. The cells were incubated in the presence of [35S]methionine. Labelled polypeptides, immunologically related to alpha and LH beta subunits, were isolated by specific immunoprecipitation, then analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and revealed by fluorography. Electrophoretic analysis of immunoprecipitates is a crucial step in this methodology. It permits simultaneous purification, characterization and accurate quantitation of the radioactivity specifically incorporated into LH subunits. Also, using SDS-PAGE, it is possible to isolate and identify the different processed forms of LH subunits.

Synthesis of gonadotrophins and its regulation in the pituitary gland

Regulation of the synthesis of pituitary gonadotrophins LH and FSH has been studied in the rat using either cell-free translation of pituitary mRNAs, or hybridization techniques with synthetic oligodeoxynucleotides or cloned complementary DNAs. Gonadectomy greatly increases and supplementing gonadectomized rats with gonadal steroids diminishes the rate of synthesis of the gonadotrophin subunits. Hybridization experiments suggest that gonadal steroids regulate the expression of the genes coding for pituitary gonadotrophin subunit precursors. Using the incorporation of labelled methionine by pituitary cells in culture, followed by specific immunoprecipitation of LH-related subunits and SDS-polyacrylamide gel analysis of immunoprecipitated peptides, there was evidence that gonadotrophin releasing hormone (GnRH) significantly enhances the radioactivity incorporated into both alpha- and LH beta-subunits. This effect is specific, it is not a secondary effect due to the release of LH. A cyclic AMP (cAMP) analogue, 8-Br-cAMP, as well as forskolin and choleragen, which are cAMP generators and a diacylglycerol analogue, tetradecanoylphorbol acetate (TPA), mimic the stimulatory action of GnRH on the synthesis of the polypeptide chains of LH. However, no evidence has been obtained that either cAMP or diacylglycerols mediate this GnRH effect. These results suggest that the synthesis of pituitary gonadotrophins is under a double control of gonadal steroids and GnRH which exert opposite effects, inhibitory for steroids and stimulatory for GnRH. The negative control by steroids occurs at the genomic level, while the positive effect of GnRH proceeds via different mechanisms which remain to be elucidated.

Multimodal control of pituitary gonadotropin biosynthesis. Effects of gonadal steroids, GnRH, cyclic AMP and diacylglycerols

We and others have previously shown that in the rat and the sheep gonadectomy increases the translational capacity of mRNAs encoding gonadotropin subunits alpha, LH beta and FSH beta. Injection of estradiol or of testosterone or dihydrotestosterone depresses the translational capacity of the mRNAs. After using estradiol to induce progesterone receptors in the pituitary of castrated animals, it was determined that progesterone does enhance the inhibitory effect of estradiol. We have also observed this inhibitory effect of gonadal steroids in vitro, suggesting that at least part of the steroid action is exerted at the pituitary level. Hybridization assay (Northern blot) using oligodeoxynucleotide probes complementary to a short portion in the cDNA strand of each subunit, showed gonadal steroids to act by decreasing the number of copies of mRNAs encoding LH and FSH subunits. Using anterior pituitary cells in culture, incubated in the presence of labeled methionine, we have confirmed our previous observation that GnRH stimulates the biosynthesis of the polypeptide chains of LH. This effect is not secondary due to LH release. It is not inhibited when incubation is performed in the presence of tunicamycin, an inhibitor of glycosylation. SDS-polyacrylamide gel electrophoresis of specific immunoprecipitates of polypeptides immunologically related to alpha allowed us to identify 3 forms of alpha-polypeptide differing in their apparent Mr:21K (partially glycosylated), 23K (authentic) and 25K (hyperglycosylated). Besides its stimulatory effect on the release and synthesis of LH, GnRH also stimulated the release of the 23K and 25K forms of alpha. In the presence of tunicamycin an additional 16K form of apoprotein-alpha was detected which accumulated within the cells. A cAMP analogue (8-Br-cAMP), intracellular cAMP generators (choleragen, forskolin), as well as an analogue of diacylglycerols (TPA) mimic the stimulatory action of GnRH. However, although no evidence has been obtained at present that either cAMP or diacylglycerols mediate the GnRH effect on the biosynthesis of the polypeptide chains of LH, our data suggest that phosphorylation of intracellular phosphoproteins plays a major role in this process.

[In situ biosynthesis of LH in cultured anterior pituitary cells: effects of GnRH]

In order to investigate the biosynthetic pathway of LH subunits, anterior pituitary cells were cultured in the presence of [35S]Met and polypeptides immunologically-related (i.r.) to the alpha and LH beta subunits were isolated from cells and media using specific antisera. SDS-polyacrylamide gel electrophoresis allowed us to identify 3 forms of alpha polypeptide differing in their apparent Mr: 21 K, 23 K and 25 K. Pulse-chase experiments showed the 21 K peptide (partially glycosylated) being successively converted into 23 K (authentic alpha) and 25 K ("hyperglycosylated") peptides, with spontaneous release of the 2 larger forms into the medium. With regard to LH beta, a single polypeptide of Mr 19 K was resolved by electrophoresis from material immuno-precipitated with antiserum to LH beta. This LH beta-related polypeptide was primarily present in cells, and only in trace amounts in the medium. When the incubation of cells was performed in the presence of tunicamycin (an inhibitor of glycosylation), a 16 K i.r.-form of alpha was observed, corresponding to the apopeptide alpha. The use of hydroxynorvaline, which substitutes for threonine thereby blocking glycosylation sites, induced accumulation of the 21 K-form. In the presence of GnRH (10-40 nM), the rate of synthesis of the polypeptide chains of the LH subunits increased, whether or not glycosylation was blocked, suggesting that GnRH has no direct effect on glycosylation. GnRH also readily induced the release of the newly synthesized LH subunits. This stimulatory effect of GnRH was more pronounced for the highly glycosylated forms of alpha (23 and 25 K) compared to the 16 and 21 K forms.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadotropin-releasing hormone stimulates the synthesis of the polypeptide chains of luteinizing hormone

The effect of GnRH on the synthesis of the polypeptide chains of LH was reevaluated using the incorporation of labeled methionine by pituitary cells in culture, followed by specific immunoprecipitation of LH-related subunits and sodium dodecyl sulfate-polyacrylamide gel analysis of immuno-precipitated peptides. Fluorography and counting of labeled subunits separated on the gels demonstrated that the presence of GnRH in the medium significantly enhanced the radioactivity incorporated into both alpha- and LH beta-subunits after a 5-h incubation period. Cycloheximide completely inhibited [35S]Met incorporation in the absence or presence of GnRH, whereas actinomycin D only prevented the stimulatory effect of GnRH on this incorporation. The increase of potassium ion concentration in the medium to 59 mM was without any effect on the synthesis of LH subunits. These data demonstrate that GnRH specifically stimulates synthesis of the polypeptide chains of LH and suggest that GnRH action is mediated by RNA synthesis. Whether the expression of specific messenger RNAs encoding the LH subunits is affected by GnRH is now under investigation.

Effect of gonadectomy on pituitary levels of mRNA encoding gonadotropin subunits and secretion of luteinizing hormone

Using cell-free translation of pituitary mRNAs we have investigated how, following gonadectomy in rats, the translational capacity of the specific messages encoding precursors to gonadotropin subunits alpha, LH-beta and FSH-beta increases with time. In parallel, serum LH was assayed in order to compare release and synthesis patterns. We observed a rapid rise in the rate of synthesis of all three precursors, with a significant increase already detectable 4 days after gonadectomy, and a plateau reached after 21 days. The kinetics were similar in both males and females, but maximal translational values for alpha-subunit were slightly higher in males. During the same time period, serum LH rapidly increased in the males, while in the females the rise of circulating LH was somewhat delayed. Although no direct correlation seems to exist between synthesis and release processes of gonadotropins, it is evident from our previous findings and the present data that both phenomena are dependent on gonadal steroids. In this respect, estradiol has been shown to regulate negatively, via different routes, the synthesis as well as the secretion of pituitary gonadotropins.