Stimulation of oestrogen receptor-expressing endothelial cells with oestrogen reduces proliferation of cocultured vascular smooth muscle cells.

1. Oestrogen reduces vascular smooth muscle cell proliferation in mouse vascular injury models. Data on the antiproliferative effect of oestrogen in cultured vascular smooth muscle cells (VSMC) are less conclusive than those obtained in whole animal studies. 2. In the present study, we investigated the hypothesis that oestrogen-induced attenuation of VSMC proliferation is facilitated by the presence of endothelial cells (EC) using a coculture system of EC and VSMC. 3. Treatment with a physiological concentration of oestrogen (17beta-estradiol (E2); 100 nmol/L) had no effect on fetal calf serum (FCS)-stimulated DNA synthesis in either A7r5 VSMC or bEnd.3 EC. However, stimulation of bEnd. 3 cells with E2 in a coculture system of bEnd.3 and A7r5 cells reduced FCS-induced DNA synthesis in A7r5 cells by approximately 45%. The nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (l-NAME; 100 micromol/L) did not reverse the oestrogen-induced attenuation of DNA synthesis. The antiproliferative effect of E2 may be mediated via either oestrogen receptor (ER) alpha, ERbeta or both because the bEnd.3 cells expressed immunoreactivity for both ER subtypes. 4. These data show that ERalpha- and ERbeta-expressing endothelial cells, which are stimulated with a physiological concentration of oestrogen, release a factor(s) that arrests the proliferation of cocultured VSMC. Oestrogen-induced attenuation of vascular smooth muscle cell proliferation is not prevented by L-NAME, suggesting that a mechanism other than endothelial NO is involved

Polyamine synthesis inhibition induces S phase cell cycle arrest in vascular smooth muscle cells.

Polyamines are important for cell growth and proliferation and they are formed from arginine and ornithine via arginase and ornithine decarboxylase (ODC). Arginine may alternatively be metabolised to NO via NO synthase. Here we study if vascular smooth muscle cell proliferation can be reversed by polyamine synthesis inhibitors and investigate their mechanism of action. Cell proliferation was assessed in cultured vascular smooth muscle A7r5 cells and in endothelium-denuded rat arterial rings by measuring [(3)H]-thymidine incorporation and by cell counting. Cell cycle phase distribution was determined by flow cytometry and polyamines by HPLC. Protein expression was determined by Western blotting. The ODC inhibitor DFMO (1-10 mM) reduced polyamine concentration and attenuated proliferation in A7r5 cells and rat tail artery. DFMO accumulated cells in S phase of the cell cycle and reduced cyclin A expression. DFMO had no effect on cell viability and apoptosis as assessed by fluorescence microscopy. Polyamine concentration and cellular proliferation were not affected by the arginase inhibitor NOHA (100-200 muM) and the NO synthase inhibitor L: -NAME (100 muM). Lack of effect of NOHA was reflected by absence of arginase expression. Polyamine synthesis inhibition attenuates vascular smooth muscle cell proliferation by reducing DNA synthesis and accumulation of cells in S phase, and may be a useful approach to prevent vascular smooth muscle cell proliferation in cardiovascular diseases

Demonstration of mitochondrial oestrogen receptor beta and oestrogen-induced attenuation of cytochrome c oxidase subunit I expression in human periodontal ligament cells.

OBJECTIVE: Periodontal ligament (PDL) cells express oestrogen receptor beta (ERbeta) protein, but cellular functions regulated by ERbeta in these cells have not been identified. In this study we determine if ERbeta is localised to mitochondria and if oestrogen regulates mitochondrial function in human PDL cells obtained from teeth extracted for orthodontic reasons. DESIGN: Subcellular distribution of ERbeta was determined by confocal microscopy of cells co-stained with ERbeta antibody and the mitochondrion-selective probe MitoTracker and by immunogold electron microscopy. Expression of the mitochondrial enzyme cytochrome c oxidase subunit I, involved in oxidative phosphorylation, was determined by Western blotting in cells treated with or without physiological concentrations of the endogenous oestrogen 17beta-oestradiol. RESULTS: ERbeta immunoreactivity was observed both in the nuclei and the cytoplasm. MitoTracker-labelling was observed in the cytoplasm, especially in the perinuclear region, but not in the nuclei. Co-localisation of ERbeta and MitoTracker was observed in cells derived from both male and female subjects. Mitochondrial localisation of ERbeta was confirmed by immunogold electron microscopy. Cells treated with or without 17beta-oestradiol (100 nM) displayed an identical pattern of staining for mitochondria. Treatment with 100 nM 17beta-oestradiol attenuated cytochrome c oxidase subunit I expression by about 30%, while combined treatment with 17beta-oestradiol and the ER blocker ICI 182780 (10 microM) had no effect. CONCLUSION: This study demonstrates mitochondrial localisation of ERbeta and oestrogen-induced decrease in the expression of cytochrome c oxidase subunit I in human PDL cells, suggesting that oestrogen probably via ERbeta influences mitochondrial function and PDL cell energ

Inhibition of Polyamine Formation Antagonizes Vascular Smooth Muscle Cell Proliferation and Preserves the Contractile Phenotype

The polyamines putrescine, spermidine and spermine play essential roles in cell proliferation and migration, two processes involved in the development of vascular disease. Thus, intervention with polyamine formation may represent a way to inhibit unwanted vascular smooth muscle cell (VSMC) proliferation. The aim of the present study was to assess the importance of polyamines for VSMC proliferation and vascular contractility. The rate-limiting step in polyamine biosynthesis is catalyzed by ornithine decarboxylase. Treatment with α-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, reduced DNA synthesis in primary rat VSMCs in a concentration-dependent manner with an IC50 value of 100 μM. Moreover, DFMO reduced VSMC migration assessed in a scratch assay. The DFMO-induced attenuation of VSMC proliferation was associated with lowered cellular amount of polyamines. The anti-proliferative effect of DFMO was specific since supplementation with polyamines reversed the effect of DFMO on proliferation and normalized cellular polyamine levels. Isometric force recordings in cultured rat tail artery rings showed that DFMO counteracts the decrease in contractility caused by culture with foetal bovine serum as growth stimulant. We conclude that inhibition of polyamine synthesis by DFMO may limit the first wave of cell proliferation and migration, which occurs in the acute phase after vascular injury. Besides its anti-proliferative effect, DFMO may prevent loss of the smooth muscle contractile phenotype in vascular injury. This article is protected by copyright. All rights reserved

Inhibition of polyamine uptake potentiates the anti-proliferative effect of polyamine synthesis inhibition and preserves the contractile phenotype of vascular smooth muscle cells.

Increased vascular smooth muscle cell (VSMC) proliferation is a factor in atherosclerosis and injury-induced arterial (re)stenosis. Inhibition of polyamine synthesis by α-difluoro-methylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, attenuates VSMC proliferation with high sensitivity and specificity. However, cells can escape polyamine synthesis blockade by importing polyamines from the environment. To address this issue, polyamine transport inhibitors (PTIs) have been developed. We investigated the effects of the novel trimer44NMe (PTI-1) alone and in combination with DFMO on VSMC polyamine uptake, proliferation and phenotype regulation. PTI-1 efficiently inhibited polyamine uptake in primary mouse aortic and human coronary VSMCs in the absence as well as in the presence of DFMO. Interestingly, culture with DFMO for 2 days substantially (>95%) reduced putrescine (Put) and spermidine (Spd) contents without any effect on proliferation. Culture with PTI-1 alone had no effect on either polyamine levels or proliferation rate, but the combination of both treatments reduced Put and Spd levels below the detection limit and inhibited proliferation. Treatment with DFMO for a longer time period (4 days) reduced Put and Spd below their detection limits and reduced proliferation, showing that only a small pool of polyamines is needed to sustain VSMC proliferation. Inhibited proliferation by polyamine depletion was associated with maintained expression of contractile smooth marker genes. In cultured intact mouse aorta, PTI-1 potentiated the DFMO-induced inhibition of cell proliferation. The combination of endogenous polyamine synthesis inhibition with uptake blockade is thus a viable approach for targeting unwanted vascular cell proliferation in vivo, including vascular restenosis. This article is protected by copyright. All rights reserved

17β-oestradiol acts as a negative modulator of insulin-induced lactotroph cell proliferation through oestrogen receptor alpha, via nitric oxide/guanylyl cyclase/cGMP

Objectives: 17b-oestradiol interacts with growth factors to modulate lactotroph cell population. However, contribution of isoforms of the oestrogen receptor in these activities is not fully understood. In the present study, we have established participation of a and b oestrogen receptors in effects of 17b-oestradiol on lactotroph proliferation induced by insulin and shown involvement of the NO⁄sGC⁄ cGMP pathway. Materials and methods: Cell cultures were prepared from anterior pituitaries of female rats to evaluate lactotroph cell proliferation using bromodeoxyuridine (BrdUrd) detection, protein expression by western blotting and cGMP by enzyme immunoassay. Results: In serum-free conditions, 17b-oestradiol and a and b oestrogen receptor agonists (PPT and DPN) failed to increase numbers of lactotroph cells undergoing mitosis. Co-incubation of 17b-oestradiol⁄insulin and PPT⁄insulin significantly decreased lactotroph mitogenic activity promoted by insulin alone. Both ICI 182780 and NOS inhibitors (L-NMMA and L-NAME) induced reversal of the anti-proliferative effect promoted by 17b-oestradiol⁄ insulin and PPT⁄insulin. Moreover, 17b-oestradiol, PPT and insulin increased sGC a1 protein expression and inhibited b1, whereas co-incubation of 17boestradiol⁄insulin or PPT⁄insulin induced increases of the two isoforms a1 and b1. 17b-oestradiol and insulin reduced cGMP production, while 17b-oestradiol⁄insulin co-incubation increased this cyclic nucleotide. Conclusions: Our results suggest that 17b-oestradiol is capable of arresting lactotroph proliferation induced by insulin through ER a with participation of the signalling NO⁄sGC⁄ cGMP pathwayFil: Gutierrez, Silvina Gabriela. Universidad Nacional de Córdoba. Facultad de Medicina. Centro de Microscopía Electrónica; ArgentinaFil: Petiti, Juan Pablo. Universidad Nacional de Córdoba. Facultad de Medicina. Centro de Microscopía Electrónica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Sosa, Liliana del Valle. Universidad Nacional de Córdoba. Facultad de Medicina. Centro de Microscopía Electrónica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Fozzatti, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; ArgentinaFil: de Paul, Ana Lucia. Universidad Nacional de Córdoba. Facultad de Medicina. Centro de Microscopía Electrónica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Masini, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; ArgentinaFil: Torres, Alicia Ines. Universidad Nacional de Córdoba. Facultad de Medicina. Centro de Microscopía Electrónica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin