Triterpenoid saponins and other glycosides from the stems and bark of Jaffrea xerocarpa and their biological activity.

Six previously undescribed triterpenoid saponins and two previously undescribed norlupane triterpenes were isolated with five known saponins, three known lupane derivatives, 17,20-didehydro-20-deoxyjujubogenin, rutin, (±) 3α-O-β-d-glucopyranosyl-lyoniresinol, (±) 4-O-β-d-glucopyranosyl-maesopsin, three phenol glycosides, and uridine from the stems and bark of Jaffrea xerocarpa (Baill.) H. C.

Triterpenoids from the leaves of Alphitonia xerocarpus Baill and their biological activity.

Ten previously undescribed triterpenoid saponins and a previously undescribed norlupane triterpenoid were isolated, with three known saponins, four known flavonoids, two known lupane derivatives, sitosterol and 6'-heptadecanoyl-3-O-β-d-glucopyranosylsitosterol from the leaves of Alphitonia xerocarpus (Rhamnaceae), an endemic tree of New Caledonia. The chemical structures of the purified compounds were identified by nuclear magnetic resonance and mass spectrometry. The isolated compounds were tested for their antioxidant, antityrosinase, antibacterial and cytotoxic activity.

Isolation of flavonoids and triterpenoids from the fruits of Alphitonia neocaledonica and evaluation of their anti-oxidant, anti-tyrosinase and cytotoxic activities.

Introduction: Alphitonia neocaledonica (Rhamnaceae) is an endemic tree of New Caledonia. Although three flavonoids have been identified in the leaves, the secondary metabolite profile of the fruits has never been investigated.

Objective: Phytochemical investigation of A.

Targeted nano analysis of water and ions in the nucleus using cryo-correlative microscopy.

The cell nucleus is a crowded volume in which the concentration of macromolecules is high. These macromolecules sequester most of the water molecules and ions which, together, are very important for stabilization and folding of proteins and nucleic acids. To better understand how the localization and quantity of water and ions vary with nuclear activity, it is necessary to study them simultaneously by using newly developed cell imaging approaches.

The elastin peptide (VGVAPG)3 induces the 3D reorganisation of PML-NBs and SC35 speckles architecture, and accelerates proliferation of fibroblasts and melanoma cells.

During melanoma tumour growth, cancerous cells are exposed to the immediate surrounding the micro- and macro environment, which is largely modified through the degradation of the extracellular matrix by fibroblast-derived metalloproteinases. Among the degradation products, (VGVAPG)3, an elastin peptide is known to stimulate the proliferation of both fibroblasts and cancerous cells by binding to the elastin-binding receptor and activating the MEK/ERK signal transduction pathway. As this process strongly modifies mRNA synthesis, we investigated its effect on the relative three-dimensional organisation of the major partners of the mRNA splicing machinery: promyelocytic nuclear bodies (PML-NBs ) and splicing component 35 speckles (SC35) of normal fibroblasts and melanoma SK-MEL-28 cells.

Changes to cellular water and element content induced by nucleolar stress: investigation by a cryo-correlative nano-imaging approach.

The cell is a crowded volume, with estimated mean mass percentage of macromolecules and of water ranging from 7.5 to 45 and 55 to 92.5 %, respectively.

Targeted nano analysis of water and ions using cryocorrelative light and scanning transmission electron microscopy.

Cryo fluorescence imaging coupled with the cryo-EM technique (cryo-CLEM) avoids chemical fixation and embedding in plastic, and is the gold standard for correlated imaging in a close to native state. This multi-modal approach has not previously included elementary nano analysis or evaluation of water content. We developed a new approach allowing analysis of targeted in situ intracellular ions and water measurements at the nanoscale (EDXS and STEM dark field imaging) within domains identified by examination of specific GFP-tagged proteins.

Triterpene saponins from Antonia ovata leaves.

Six pentacyclic triterpenoid saponins, named antoniosides E-J along with two known alkaloids, were isolated from the leaves of Antonia ovata. Their structures were determined by the extensive use of 1D and 2D-NMR experiments along with HRESIMS analysis and acid hydrolysis. All isolated saponins contained the same pentasaccharide chain: 3-O-[β-D-glucopyranosyl-(1→2)]-[β-D-glucopyranosyl-(1→4)]-[β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl(1→6)]-β-D-glucopyranoside, linked at C-3 of esterified derivatives of polyhydroxyoleanene triterpenoids (theasapogenol A and 15α-hydroxy-theasapogenol A).

Elastin peptides signaling relies on neuraminidase-1-dependent lactosylceramide generation.

The sialidase activity of neuraminidase-1 (Neu-1) is responsible for ERK 1/2 pathway activation following binding of elastin peptide on the elastin receptor complex. In this work, we demonstrate that the receptor and lipid rafts colocalize at the plasma membrane. We also show that the disruption of these microdomains as well as their depletion in glycolipids blocks the receptor signaling.

Lumican inhibits cell migration through α2β1 integrin.

Lumican, an extracellular matrix protein of the small leucine-rich proteoglycan family, has been shown to impede melanoma progression by inhibiting cell migration. In the present study, we show that lumican targets α2β1 integrin thereby inhibiting cell migration. A375 melanoma cells were transfected with siRNA directed against the α2 integrin subunit.

Cytotoxic triterpenoid saponins from the stem bark of Antonia ovata.

Phytochemical investigation of the MeOH extract of the stem bark of Antonia ovata led to the isolation of four triterpenoid saponins, along with eleven known compounds. Their structures were established by extensive 1D and 2D NMR, as well as HR-MS analysis and acid hydrolysis. All isolated saponins contained the same tetrasaccharide chain O-beta-d-xylopyranosyl-(1-->2)-O-beta-d-glucopyranosyl-(1-->3)-O-[beta-d-glucopyranosyl-(1-->2)]-beta-d-glucuropyranoside linked to C-3 of esterified derivatives of R(1)-barrigenol, A(1)-barrigenol, barringtogenol C, or camelliagenin.

Lumican core protein inhibits melanoma cell migration via alterations of focal adhesion complexes.

Lumican is a small leucine-rich proteoglycan (SLRP) of the extracellular matrix (ECM) with anti-tumor activity. We recently demonstrated that lumican inhibits the migration of melanoma cells and identified beta1 integrin as mediator of this effect [M.F.

A protocol for studying the kinetics of RNA within cultured cells: application to ribosomal RNA.

This protocol describes a nonisotopic method for high-resolution investigation of the kinetics of RNA within the cell. This involves the incorporation of bromouridine-5'-triphosphate into RNA of living cells by lipofection followed by immunocytological detection of BrRNAs. The use of the same antibody identified either with fluorescence or with gold particles revealed the three-dimensional organization of sites containing labeled RNAs or their precise localization by using confocal and ultrastructural microscopy, respectively.

Three-dimensional reconstruction of nucleolar components by electron microscope tomography.

The nucleus is a complex volume constituted of numerous subcompartments in which specific functions take place due to a specific spatial organization of their molecular components. To understand how these molecules are spatially organized within these machineries, it is necessary to investigate their three-dimensional organization at high resolution. To reach this goal, electron tomography appears to be a method of choice; it can generate tomograms with a resolution of a few nanometers by using multiple projections of a tilted section several hundred to several thousand nanometers in thickness imaged by transmission electron microscopy (TEM).

Tomography of the cell nucleus using confocal microscopy and medium voltage electron microscopy.

Changes in nuclear structures are widely used by pathologists as diagnostic and prognostic indicators in cancer cells. Recent studies have demonstrated that the cell nucleus is probably the most complex organelle in the cell. It contains the genome and is the site of all related activities such as DNA repair, DNA duplication, RNA synthesis, RNA processing and RNA transport.

Structure-activity relationships of some hederagenin diglycosides: haemolysis, cytotoxicity and apoptosis induction.

Hederagenin saponins are largely represented in nature and possess many biological activities such as haemolytic, antiviral, fungicidal, molluscicidal or cytotoxic, partially due to their interaction with the cell membrane. The lysis of erythrocytes (haemolysis) is a simple test to evaluate this adsorption, and this activity has been linked to the structure of the aglycone and also depends on the sugar moiety of the saponin. To further complete our study of the structure-activity relationships of triterpenoid saponins, alpha-hederin and related hederagenin diglycosides were synthesized to better understand the influence of the second sugar (alpha-L-rhamnose, beta-D-xylose or beta-D-glucose) and the substitution of this sugar on alpha-L-arabinose (position 2, 3 or 4).

UVA-mediated down-regulation of MMP-2 and MT1-MMP coincides with impaired angiogenic phenotype of human dermal endothelial cells.

UVA irradiation, dose-dependently (5-20 J/cm2), was shown to impair the morphogenic differentiation of human microvascular endothelial cells (HMECs) on Matrigel. Parallely, UVA down-regulated the expression of MMP-2 and MT1-MMP, both at the protein and the mRNA levels. On the contrary, the production of MMP-1 and TIMP-1 by HMECs increased following UVA treatment.

Induction of apoptosis by bleomycin in p53-null HL-60 leukemia cells.

The role of p53 in apoptosis and the contrasting p53 status in tumors prompted us to investigate the bleomycin-induced apoptosis in p53-null human leukemia HL-60 cells (bleomycin at 160 microM for 7.5 h). Cells with apoptotic phenotype increased from 0.

Cell-cycle-dependent three-dimensional redistribution of nuclear proteins, P 120, pKi-67, and SC 35 splicing factor, in the presence of the topoisomerase I inhibitor camptothecin.

Topoisomerase I (Topo I) is mostly known for its role in DNA relaxation, which is required for duplication and transcription. Topo I acts as a protein kinase mainly directed to the mRNA splicing factor SC35. Camptothecin is one of the specific Topo I inhibitors and is effective on the two functions of the enzyme.

Nuclear transcription factor GATA-1 is activated during aclacinomycin-induced erythroid differentiation.

Anthracycline antitumor drugs induce erythroid differentiation of the K562 erythroleukemic cell line at subtoxic concentrations. Aclacinomycin (ACM) stimulates this process by activating the erythroid transcription factor GATA-1, that controls genes involved in hemoglobin biosynthesis. To investigate the implication of GATA-1 in this process, we used a specific anti-GATA-1 polyclonal antibody that we produced in our laboratory.

Evidence for crucial electrostatic interactions between Bcl-2 homology domains BH3 and BH4 in the anti-apoptotic Nr-13 protein.

Nr-13 is an anti-apoptotic member of the Bcl-2 family previously shown to interact with Bax. The biological significance of this interaction was explored both in yeast and vertebrate cells and revealed that Nr-13 is able to counteract the pro-apoptotic activity of Bax. The Bax-interacting domain has been identified and corresponds to alpha-helices 5 and 6 in Nr-13.

Distinctive alterations of invasiveness, drug resistance and cell-cell organization in 3D-cultures of MCF-7, a human breast cancer cell line, and its multidrug resistant variant.

Growth of human tumor cells as three-dimensional (3D) multicellular spheroids modifies their invasive properties. Here we study the differences in the biological features of MCF-7, a human breast cancer cell line, and its multidrug resistant variant (MDR-MCF-7) cultured as spheroids or as monolayers. Three-dimensional culture decreased the proliferative rate of both cell lines, reduced the drug sensitivity of MCF-7 cells and did not affect the resistance of MDR-MCF-7 cells.

Nuclear transport as an ultimate step of multidrug resistance.

Adriamycin (ADM) incorporation into nuclei of whole multidrug resistant (MDR) CEM cells is lower than into sensitive ones (S), that is mostly thought to be the consequence of a decrease of drug related to the activity of the multidrug resistance plasma membrane protein P 170. Isolated nuclei of the lymphoblastic tumor cell line CEM, which structures were controlled by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal microscopy, where incubated with 10(-6) mole/l of ADM. Incorporation into DNA was quantified by spectrofluorimetry.

Involvement of the 92-kDa gelatinase (matrix metalloproteinase-9) in the ceramide-mediated inhibition of human keratinocyte growth.

Triggering the ceramide pathway by exogenous treatment with neutral sphingomyelinase (Smase) inhibited human keratinocyte growth rate, while having no influence on cell apoptosis. Increasing the ceramide content of keratinocytes with Smase (100 U/ml) or C6-ceramide (1 microM) enhanced matrix metalloproteinase (MMP)-9 production. On the contrary, levels of MMP-2 secretion were unchanged.

Enhancement of all-trans-retinoic acid efficiency in granulocytic differentiation of HL-60 cells by incorporation into low density lipoprotein.

All-trans-retinoic acid (ATRA) has been proven to lead to complete remission of acute promyelocytic leukemia by inducing differentiation into granulocytes except when an acquired resistance occurred. High levels of low density lipoprotein (LDL) receptor in cancer cells suggested the use of ATRA incorporated into LDL. 50% of HL-60 cell differentiation were obtained with 5 nmoles/l of ATRA-LDL compared to 150 moles/l of ATRA.