Human recombinant FSH induces chemoresistance in human breast cancer cells via HIF-1α activation†.

Breast cancer patients under 40 years of age who are candidate to chemotherapy with alkylating drugs may undergo controlled ovarian stimulation (COS) with recombinant human follicle-stimulating hormone (rhFSH) in order to get fertility preservation by mature oocyte cryostorage. The direct effect(s) of exogenous rhFSH on the chemosensitivity of breast cancer is currently unknown. To clarify this issue, we incubated four different breast cancer cell lines with rhFSH (10 IU/L, 24 h) and then we exposed them to doxorubicin (DOX) or cyclophosphamide (CPA). The effect(s) of rhFSH on human breast cancer cells treated with DOX or CPA was measured in terms of (1) cell viability, (2) cytotoxicity, (3) multidrug resistance (MDR) genes and proteins expression and activities, and (4) hypoxia-inducible factor 1-alpha (HIF-1α) activation. Pretreatment with rhFSH significantly increased the viability of breast cancer cells after treatment with DOX or CPA, and reduced the lactate dehydrogenase leakage and reactive oxygen species production. Moreover, after preincubation with rhFSH, the MDR proteins (Pgp, MPR1, and BCRP) expression and activity resulted upregulated and the HIF-1α pathway activated. In addition, the use of a widely used HIF-1α inhibitor, the 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1), prevented the rhFSH effect on the onset of MDR. Taken together, these observations suggest that a short exposure to rhFSH induces chemoresistance to DOX and CPA in human breast cancer cells via HIF-1α activation.

Platelet vitamin D receptor is reduced in osteoporotic patients.

AIM: It is well known that vitamin D plays an important role in maintaining bone homeostasis and in regulating calcium absorption. The active form of vitamin D interacts with its receptor the VDR that is expressed in multiple tissues and it is involved in platelets (PLTs) function. In the present study we evaluate PLTs' VDR expression in osteoporotic as opposed to healthy subjects. METHODS: We enrolled in the study 77 women with postmenopausal osteoporosis, 33 healthy women of childbearing age, 49 healthy men, and 11 healthy women matched with patients for age and postmenopausal period. Thirty-nine patients had had one femoral fracture occurred after the age of fifty and attributable to primary osteoporosis. Bone mineral density, markers of bone metabolism and VDR levels were measured in all the subjects. RESULTS: Our data show that VDR level is lower in patients as respect to controls and is positively correlated with bone density, but not with markers of bone metabolism. We also found a decrease in the phosphorus levels in patients without differences in vitamin D levels and in the dietary calcium intake. CONCLUSION: The lower VDR expression in osteoporotic could indicate a lower ability to respond to vitamin D, and could be the explanation of the increase in the PTH and decrease in the phosphorus levels in patients with respect to controls.

Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells.

OBJECTIVE: In cultured human vascular smooth muscle cells, insulin increases cyclic GMP production by inducing nitric oxide (NO) synthesis. The aim of the present study was to determine whether in these cells the insulin-stimulated NO/cyclic GMP pathway plays a role in the regulation of glucose uptake. METHODS AND RESULTS: Glucose transport in human vascular smooth muscle cells was measured as uptake of 2-deoxy-d-[3H]glucose, cyclic GMP synthesis was checked by radioimmunoassay, and GLUT4 recruitment into the plasma membrane was determined by immunofluorescence. Insulin-stimulated glucose transport and GLUT4 recruitment were blocked by an inhibitor of NO synthesis and mimicked by NO-releasing drugs. Insulin- and NO-elicited glucose uptake were blocked by inhibitors of soluble guanylate cyclase and cyclic GMP-dependent protein kinase; furthermore, glucose transport was stimulated by an analog of cyclic GMP. CONCLUSIONS: Our results suggest that insulin-elicited glucose transport (and the corresponding GLUT4 recruitment into the plasma membrane) in human vascular smooth muscle cells is mediated by an increased synthesis of NO, which stimulates the production of cyclic GMP and the subsequent activation of a cyclic GMP-dependent protein kinase.

Muscular dystrophy in mdx mice despite lack of neuronal nitric oxide synthase.

Neuronal nitric oxide synthase (nNOS) is a component of the dystrophin complex in skeletal muscle. The absence of dystrophin protein in Duchenne muscular dystrophy and in mdx mouse causes a redistribution of nNOS from the plasma membrane to the cytosol in muscle cells. Aberrant nNOS activity in the cytosol can induce free radical oxidation, which is toxic to myofibers. To test the hypothesis that derangements in nNOS disposition mediate muscle damage in Duchenne dystrophy, we bred dystrophin-deficient mdx male mice and female mdx heterozygote mice that lack nNOS. We found that genetic deletion of nNOS does not itself cause detectable pathology and that removal of nNOS does not influence the extent of increased sarcolemmal permeability in dystrophin-deficient mice. Thus, histological analyses of nNOS-dystrophin double mutants show pathological changes similar to the dystrophin mutation alone. Taken together, nNOS defects alone do not produce muscular dystrophy in the mdx model.

Nitric oxide synthase and cyclic GMP-dependent protein kinase concentrated at the neuromuscular endplate.

Nitric oxide mediates diverse functions in development and physiology of vertebrate skeletal muscle. Neuronal type nitric oxide synthase-mu is enriched in fast-twitch fibers and binds to syntrophin, a component of the sarcolemmal dystrophin glycoprotein complex. Here, we show that cyclic GMP-dependent protein kinase type I, a primary effector for nitric oxide, occurs selectively at the neuromuscular junction, in mice and rats, and both neuronal type nitric oxide synthase-mu and cyclic GMP-dependent protein kinase type I remain at skeletal muscle endplates at least two weeks following muscle denervation. Expression of neuronal type nitric oxide synthase-mu and cyclic GMP-dependent protein kinase type I are up-regulated following fusion of cultured primary myotubes. Interestingly, the highest levels of neuronal type nitric oxide synthase-mu in muscle are found complexed with dystrophin at the sarcolemma of intrafusal fibers in muscle spindles. Localization of neuronal type nitric oxide synthase-mu and cyclic GMP-dependent protein kinase type I at the neuromuscular junction suggests functions for nitric oxide and cyclic GMP in the regulation of synaptic actions of intra- and extrafusal muscle fibers.

Neuronal nitric-oxide synthase-mu, an alternatively spliced isoform expressed in differentiated skeletal muscle.

Nitric oxide (NO) functions as a molecular mediator in numerous processes in cellular development and physiology. Differential expression and regulation of a family of three NO synthase (NOS) gene products help achieve this diversity of action. Previous studies identify post-translational modification and interaction of NOS with specific protein targets as tissue-specific modes of regulation. Here, we show that alternative splicing specifically regulates neuronal NOS (nNOS, type I) in striated muscle. nNOS in skeletal muscle is slightly more massive than nNOS from brain owing to a 102-base pair (34-amino acid) alternatively spliced segment between exons 16 and 17. Following purification, this novel nNOS mu isoform has similar catalytic activity to that of nNOS expressed in cerebellum. nNOS mu appears to function exclusively in differentiated muscle as its expression occurs coincidentally with myotube fusion in culture. An isoform-specific antibody detects nNOS mu protein only in skeletal muscle and heart. This study identifies alternative splicing as a means for tissue-specific regulation of nNOS and reports the first additional protein sequence for a mammalian NOS since the original cloning of the gene family.

Purification and kinetic characterization of gamma-aminobutyraldehyde dehydrogenase from rat liver.

Oxidative deamination of putrescine, the precursor of polyamines, gives rise to gamma-aminobutyraldehyde (ABAL). In this study an aldehyde dehydrogenase, active on ABAL, has been purified to electrophoretic homogeneity from rat liver cytoplasm and its kinetic behaviour investigated. The enzyme is a dimer with a subunit molecular weight of 51,000. It is NAD(+)-dependent, active only in the presence of sulphhydryl compounds and has a pH optimum in the range 7.3-8.4. Temperatures higher than 28 degrees C promote slow activation and the process is favoured by the presence of at least one substrate. Km for aliphatic aldehydes decreases from 110 microM for ABAL and acetaldehyde to 2-3 microM for capronaldehyde. The highest relative V-values have been observed with ABAL (100) and isobutyraldehyde (64), and the lowest with acetaldehyde (14). Affinity for NAD+ is affected by the aldehyde present at the active site: Km for NAD+ is approximately 70 microM with ABAL, approximately 200 microM with isobutyraldehyde and capronaldehyde, and > 800 microM with acetaldehyde. The kinetic behaviour at 37 degrees C is quite complex; according to enzymatic models, NAD+ activates the enzyme (Kact approximately 500 microM) while NADH competes for the regulatory site (Kin approximately 70 microM). In the presence of high NAD+ concentrations (4 mM), ABAL promotes further activation by binding to a low-affinity regulatory site (Kact approximately 10 mM). The data show that the enzyme is probably an E3 aldehyde dehydrogenase, and suggest that it can effectively metabolize aldehydes arising from biogenic amines.

In vivo activation of met tyrosine kinase by heterodimeric hepatocyte growth factor molecule promotes angiogenesis.

Hepatocyte growth factor (HGF) is a powerful motogen and mitogen for epithelial cells. The factor is a 90-kD heterodimer composed of an alpha chain containing four kringle motifs and a beta chain showing structural homologies with serine proteases. It is, however, devoid of enzymatic activity. Recently, it has been reported that HGF activates migration and proliferation of endothelial cells and is angiogenic. In this article we discuss (1) the molecular domains of HGF required to activate in vitro and in vivo endothelial cells, studied by use of molecular mutants, and (2) the characteristics of the angiogenic response to HGF in an experimental model system of implanted reconstituted basement membrane (Matrigel). Two groups of mutants were made and used in vitro and in vivo: one with deletions of kringle domains and one with substitution at the cleavage site of the HGF precursor. In vitro, HGF variants containing only the first two (HGF-NK2) or the first three kringles (HGF-NK3) of the alpha chain did not induce proliferation of endothelial cells even if used at concentration 160-fold higher than that optimal for HGF (0.05 nmol/L). High concentrations of these mutants (4 to 8 nmol/L) activated a little endothelial cell motogenic response that was 60% lower than that elicited by HGF. Substitution of Arg 489 with Gln 489 in the HGF precursor generated an uncleavable single-chain factor, unable to induce either endothelial cell migration or proliferation. In vivo, HGF induced a dose-dependent angiogenic response, which was enhanced by heparin.

Middle T antigen-transformed endothelial cells exhibit an increased activity of nitric oxide synthase.

Endothelioma cell lines transformed by polyoma virus middle T antigen (mTa) cause cavernous hemangiomas in syngeneic mice by recruitment of host cells. The production of nitric oxide (NO), as measured by nitrite and citrulline production, was significantly higher in mTa-transformed endothelial cells in comparison with nontransformed control cells. The maximal activity of NO synthase (NOS) was about 200-fold higher in cell lysates from the tEnd.1 endothelioma cell line than in lysates from nontransformed controls, whereas the affinity for arginine did not differ. The biochemical characterization of NOS and the study of mRNA transcripts indicate that tEnd.1 cells express both the inducible and the constitutive isoforms. NOS hyperactivity is not a simple consequence of cell transformation but needs a tissue-specific mTa expression. Since tEnd.1-conditioned medium induces NOS activity in normal endothelial cells, most likely NOS hyperactivity in endothelioma cells is attributable to the release of a soluble factor. This NOS-activating factor, which seems to be an anionic protein, could stimulate tEnd.1 cells to express NOS by an autocrine way. By the same mechanism, tEnd.1 cells could induce NOS in the neighboring endothelial cells, and NO release could play a role in the hemangioma development. Such hypothesis is confirmed by our in vivo experiments, showing that the administration of the NOS inhibitor L-canavanine to endothelioma-bearing mice significantly reduced both the volume and the relapse time of the tumor.

Actions of molecules which regulate hemopoiesis on endothelial cells: memoirs of common ancestors?

The proliferation and differentiation of hematopoietic stem cells (hematopoiesis) takes place in close contact with stromal cells and matrix in bone marrow. Hematopoiesis requires cytokines, collectively termed colony stimulating factors (CSFs), which act on progenitor cell populations and induce their commitment to a specific lineage. For instance, leukemia, inhibitor factor and stem cell factor act on pluripotent cells and immature progenitors, granulocyte-macrophage colony stimulating factor (GM-CSF) acts at early stages of the development of myelomonocytic lineage, whereas granulocyte-colony stimulating factor (G-CSF) and macrophage-colony stimulating factor (M-CSF) act on more mature cells of the same lineage and are only required later during the differentiation of this cell lineage. A second important element for the hematopoietic process is the presence of extracellular matrix proteins, which bind CSFs and correctly present the molecules to specific receptors present on the surface of the progenitor cells. Finally, stromal cells (i.e. fibroblasts, endothelial cells and adipocytes) which support the growth of hematopoietic stem cells in vitro, are crucial for the production of CSFs and protein matrix and regulate the passage of mature cells from bone marrow to bloodstream. Idiopathic myelofibrosis is an example of the relevance of microenvironment in hematopoiesis. This disease is characterized by fibroblast and basement membrane accumulation, appearance of myofibroblasts and modification of the capillary network and provokes a bone marrow aplasia. In this article we review recent studies on the role of hemopoietic cytokines on stromal cells, in particular on endothelial cells, and propose a double role for CSFs in hematopoiesis: to induce the commitment of progenitor cells and to maintain the behavior of bone marrow endothelial cells.

Human endothelial cells are targets for platelet-activating factor (PAF). Activation of alpha and beta protein kinase C isozymes in endothelial cells stimulated by PAF.

We evaluated the role of the protein kinase C (PKC) and its isozymes in the activation of human endothelial cells (EC) stimulated by platelet-activating factor (PAF). Exposure of confluent EC to PAF resulted in a rapid and concentration-dependent redistribution of PKC from cytosol to plasma-membrane, rearrangement of cytoskeleton (i.e. decrease in F-actin content and redistribution of vinculin), and finally increase in the transendothelial flux of 125I-albumin. Stimulation of EC with oleylacetylglycerol or phorbol 12-myristate 13-acetate induced the modification of the cytoskeletal structures and the increase of 125I-albumin clearance. Inhibitors of PKC prevented the effects induced by PAF on the cytoskeleton and on the barrier function of the EC monolayer. Confluent EC expressed only alpha, beta, and epsilon PKC isoforms. Biochemical and immunochemical analysis showed that the time course of the PKC isozymes translocation from cytosol to the membrane fraction of EC stimulated by PAF was different: beta isoform was redistributed more quickly than alpha isoform. PAF did not induce translocation of PKC epsilon. These results suggest that activation of PKC alpha and beta is an important signal transduction pathway by which PAF activates endothelial monolayer and modify its function of barrier to macromolecules.

Proliferative and migratory responses of murine microvascular endothelial cells to granulocyte-colony-stimulating factor.

Microvascular murine endothelial cells lines transformed by middle T oncogene of polyoma virus maintain the biological characteristics of nontransformed microvascular endothelial cells (EC). By using cell lines originated from different anatomical districts (thymus, brain, heart, and skin), we demonstrated that murine granulocyte-colony-stimulating factor (G-CSF) induces proliferation of murine microvascular endothelial cells at nanomolar concentrations without any cooperation with fetal calf serum. The proliferative effect on murine cells is less than that elicited by epidermal growth factor (EGF), used as standard for this function. G-CSF also promotes the migration of tEnd.1 endothelial cell line assayed by Boyden chamber technique. The analysis of transcript for G-CSF receptor (G-CSFR) by Northern blot hybridization and by reverse-transcriptase polymerase chain reaction (RT-PCR) shows that these cell lines have specific mRNA, with the size of that present in myeloid cells. These results indicate that G-CSF operates in the microvascular endothelial cells by a mechanism related to the presence of a specific receptor.