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Biomedical subjects

Margaret C P Rees

Publications and source records attributed to Margaret C P Rees.

15 recordsLinked to original sources
PubMed2006

Expression of terminally glycosylated calcitonin receptor-like receptor in uterine leiomyoma: endothelial phenotype and association with microvascular density.

PURPOSE: The role for the hypoxia-inducible angiogenic factor adrenomedullin (AM) in tumor growth and progression has been suggested. Calcitonin receptor-like receptor (CL) is a G protein-coupled receptor (GPCR) that mediates effects of AM, but little information is available on its expression and functional state in human tumors. The present study attempted to determine CL potential for antiangiogenic therapy of uterine leiomyoma. EXPERIMENTAL DESIGN AND RESULTS: GPCR CL is transported to the cell surface and recognized by AM only when terminally/mature glycosylated. The presence and localization of this form of the receptor in tumor and surrounding myometrial tissues obtained from leiomyoma-bearing uteri were examined using deglycosylation, immunoblotting, and immunofluorescence analysis. The mature CL glycoprotein was expressed in both tissues and localized exclusively in normal and tumor endothelium within leiomyoma-bearing uteri. The functionality of the receptor expressed in myometrial microvascular endothelial cells (MMVEC) was examined in vitro using receptor internalization and angiogenic assays. The mature CL glycoprotein expressed by primary MMVECs was functional because AM interacted with this GPCR and induced its internalization as well as angiogenic effects (proliferation and migration) in MMVECs in vitro. Finally, the levels of tissue-expressed mature CL glycoprotein as a functional form of this GPCR were analyzed by immunoblotting. The expression of this functional form of the receptor in vivo was significantly decreased (P = 0.01) in leiomyoma tissue, and this was concurrent with the decrease in microvascular density (measured by Chalkley counting) in tumor compared with surrounding myometrium (P = 0.031). CONCLUSIONS: Our findings suggest that GPCR CL mediates angiogenic effects of AM in myometrium and that further evaluation of the properties of the CL expressed in both normal and tumor endothelium in vivo may be essential before targeting this endothelial GPCR for antiangiogenic therapies.

Adrenomedullin↗
PubMed2006

Adrenomedullin and CGRP interact with endogenous calcitonin-receptor-like receptor in endothelial cells and induce its desensitisation by different mechanisms.

Adrenomedullin (AM) and calcitonin gene-related peptide (CGRP) are related peptides with distinct pharmacological profiles. Calcitonin-receptor-like receptor (CRLR, now known as CL) can function as either an AM receptor or a CGRP receptor, when cotransfected with receptor-activity-modifying proteins (RAMPs) that define ligand-binding specificity. The aim of the present study was to determine the role of endogenously expressed CL (EndoCL) in generating endogenous AM and CGRP receptors. We raised anti-human CL antibody and identified microvascular endothelial cells (MVECs) as a major CL-expressing cell type in tissues by immunohistochemistry. Cultured MVECs continue to express EndoCL as well as fully active endogenous AM- and CGRP-sensitive receptors in vitro, as demonstrated by the ability of both peptides to induce migration and Akt phosphorylation. We therefore tested the hypothesis that endothelial EndoCL can interact with both AM and CGRP by examining receptor internalisation and desensitisation (loss of the ability to induce Akt phosphorylation). We found that agonist-mediated internalisation of EndoCL occurs in response to AM but not CGRP in MVECs. However, AM-induced EndoCL internalisation was blocked by antagonists of both AM and CGRP receptors: AM(22-52) and CGRP(8-37), respectively. Furthermore, AM-induced EndoCL internalisation resulted in desensitisation not only of AM but also of CGRP receptors. Finally, CGRP also induced desensitisation of both endogenous AM and CGRP receptors, but did not mediate EndoCL internalisation despite interaction with this receptor. Thus, EndoCL interacts with both AM and CGRP, and simultaneously acts as a receptor for both peptides (i.e acting as an endogenous AM/CGRP receptor) in endothelial cells. Interaction with either ligand is sufficient to induce EndoCL desensitisation to both AM and CGRP, but differential mechanisms are involved since only AM induces EndoCL internalisation. These novel findings regarding regulation of EndoCL function in endothelial cells are likely to be of importance in conditions where AM or CGRP levels are elevated, such as cardiovascular disease, diabetes and inflammation.

Adrenomedullin↗
PubMed2005

Managing the menopause: British Menopause Society Council consensus statement on hormone replacement therapy.

The British Menopause Society Council aims to help health professionals inform and advise women about the menopause. This guidance regarding estrogen-based hormone replacement therapy (HRT), including tibolone, which is classified in the British National Formulary as HRT, responds to the results and analysis of the randomized Women's Health Initiative studies and the observational Million Women Study. Treatment choice should be based on up-to-date information and targeted to individual women's needs. HRT still offers the potential for benefit to outweigh harm, providing the appropriate regimen has been instigated in terms of dose, route and combination.

Estrogen Replacement Therapy↗
PubMed2004

Adrenomedullin: multiple functions in human pregnancy.

Adrenomedullin is a 52 amino acid peptide originally isolated from human phaeochromocytoma in 1993. It was initially demonstrated to have profound effects on the vasculature including vasodilatation and subsequently promotion of angiogenesis. Since then it has become apparent that it has a wide range of other biological actions including regulation of cell growth and differentiation. Successful pregnancy outcome relies on establishing and maintaining throughout gestation an efficient blood supply to the fetus. This allows the exchange of nutrients, oxygenation of fetal blood and removal of cytotoxins from the fetus, such as carbon dioxide. One of the most important local adaptations to pregnancy is the change in maternal blood flow to the implantation site. Evidence now points towards a vital role for adrenomedullin in the regulation of placentation. It appears that adrenomedullin may play important roles in the regulation of fetal perfusion both in normal and in compromised pregnancies. However, most studies have focused on measuring adrenomedullin levels and studying its expression as well as that of its receptors. More functional studies are now required to elucidate the underlying mechanisms involved.

Adrenomedullin↗
PubMed2004

Managing the menopause: BMS Council Consensus statement on HRT.

The British Menopause Society Council aims to help health professionals to inform and advise women about the menopause. The oestrogen plus progestogen arm of the Women's Health Initiative was stopped in July 2002. This guidance regarding hormone replacement therapy (HRT) use responds to the results and analysis that have been published since then, as well as the Million Women Study published in August 2003. Because there are few effective alternatives to HRT for vasomotor and urogenital symptoms, oestrogen-based treatments still have a major role. HRT is also most effective for the prevention of osteoporosis. Unopposed oestrogens are contraindicated in women with an intact uterus, and hence a range of oestrogen and progestogen combinations, with differing routes of delivery, now exists under the title of "HRT". Treatment choice should be based on up to date information and targeted to individual women's needs. Hormone replacement still offers the potential for benefit to outweigh harm, providing the appropriate regimen has been instigated in terms of dose, route and combination.

Estrogen Replacement Therapy↗
PubMed2004

Shared decision-making, health choices and the menopause.

The growing influence of the mass media on public understanding of health care matters has increased both information and misinformation in patients seeking help with menopausal symptoms. The use of shared decision-making strategies provides the opportunity to engage the patient in taking some responsibility for their own treatment. It also allows the identification and correction of any distortions in the perceived balance of evidence for and against any particular treatment. Shared decision-making balances the need to respect patients' values and autonomy with the drive towards evidence-based medicine and clinical cost-effectiveness. Although ways of achieving such a balance are much discussed, the current need is for research which can identify effective strategies that allow the principles of "shared decision-making" and "evidence-based patient choice" to be validated and applied in clinical practice. Previous research focused on hormone replacement therapy indicates that the patient's decision is the outcome of the way they balance the pros and cons of taking (or not taking) it, and that their satisfaction with the decision is strongly associated with the perception that they have been given information about the full range of treatment available. It therefore seems likely that patients will respond more positively to consultations which include discussion of hormone replacement therapy alongside alternative strategies such as natural remedies and dietary/lifestyle changes. Psychological factors influencing treatment choice and the decision making process are discussed, and clinical and research implications for clinical practice in the menopause clinic examined.

Decision Making↗
PubMed2003

Transcriptional regulation of the CRLR gene in human microvascular endothelial cells by hypoxia.

Adrenomedullin is a 52 amino acid peptide that shows a remarkable range of effects on the vasculature that include inter alia, vasodilatation, regulation of permeability, inhibition of endothelial cell apoptosis, and promotion of angiogenesis. Recently the G-protein coupled receptor (GPCR) calcitonin receptor-like receptor (CRLR), and receptor activity modifying proteins (RAMPs) have become recognized as integral components of the adrenomedullin signaling system. However, mechanisms of regulation of CRLR expression are still largely unknown. This is in part due to lack of information on the gene promoter. In this study we have determined the transcriptional start of human CRLR cDNA by 5'-RACE and cloned the proximal 5'-flanking region of the gene by PCR. The 2318 bp genomic fragment contains the basal promoter of human CRLR, including potential TATA-boxes and several GC boxes. Regulatory elements binding known transcription factors, such as Sp-1, Pit-1, glucocorticoid receptor, and hypoxia-inducible factor-1 alpha (HIF-1alpha) were also identified. When cloned into reporter gene vectors, the genomic fragment showed significant promoter activity, indicating that the 5'-flanking region isolated by PCR contains the gene promoter of human CRLR. Of significance is that the cloned promoter fragments were activated by hypoxia when transfected in primary microvascular endothelial cells. Site-directed mutagenesis of the consensus hypoxia-response element (HRE) in the 5'-flanking region abolished such a response. We also demonstrated by semi-quantitative RT-PCR that transcription of the gene is activated by hypoxia in microvascular endothelial cells. In contrast, expression of RAMPs 1, 2, and 3 was unaffected by low oxygen tension. We conclude that simultaneous transcriptional up-regulation of CRLR and its ligand adrenomedullin in endothelial cells could lead to a potent survival loop and therefore might play a significant role in vascular responses to hypoxia and ischemia.

5' Flanking Region↗
PubMed2003

Managing the menopause - British Menopause Society Council consensus statement on hormone replacement therapy.

The British Menopause Society Council aims to aid health professionals to inform and advise women about the menopause. The oestrogen plus progestogen arm of the Women's Health Initiative was stopped in July 2002. This guidance regarding hormone replacement therapy (HRT) use responds to the results and analysis that have been published since then. Because there are few effective alternatives to HRT for vasomotor and urogenital symptoms, oestrogen-based treatments still have a major role. HRT is also most effective for prevention of osteoporosis. Unopposed oestrogens are contraindicated in women with an intact uterus, and hence a range of oestrogen and progestogen combinations, with differing routes of delivery, now exists under the title of "HRT". Treatment choice should be based on up to date information and targeted to individual women's needs. Hormone replacement still offers the potential for benefit to outweigh harm, providing the appropriate regimen has been instigated in terms of dose, route and combination.

Estrogen Replacement Therapy↗
PubMed2003

Assessment of abnormal bleeding in menopausal women: an update.

Peri and postmenopausal bleeding, with or without the use of hormone replacement therapy, is a common clinical problem. The exclusion of endometrial hyperplasia and carcinoma is the key issue in the evaluation of patients with abnormal uterine bleeding. Transvaginal ultrasound measurement of endometrial thickness has become a routine procedure and an initial investigation in patients with abnormal uterine bleeding. There is debate as to whether a cut-off of 5 or 4 mm endometrial thickness should be employed. If the endometrial thickness is above these values, polyps have been diagnosed or the patient is presenting with recurrent bleeding, endometrial disease has to be excluded by histological assessment. Outpatient aspiration curettage has superseded dilatation and curettage, which was previously considered to be the gold standard for obtaining endometrial tissue, and provides the same sensitivity in detecting endometrial disease. Hysteroscopy allows visualisation of the uterine cavity and the opportunity for targeted biopsy and removal of endometrial polyps.

Biopsy↗
PubMed2002

Adrenomedullin promotes formation of xenografted endometrial tumors by stimulation of autocrine growth and angiogenesis.

The angiogenic peptide adrenomedullin (ADM) has been implicated as a mediator of the increased risk of endometrial hyperplasia and cancer resulting from the use of tamoxifen for the treatment and prevention of breast cancer. ADM has been shown to be induced by tamoxifen in the endometrium and to be a growth factor for endometrial endothelial cells in vitro. We have now shown ADM to be strongly angiogenic in the mouse subcutaneous sponge angiogenesis assay. To examine the role of ADM in tumor growth, the ADM cDNA was transfected into endometrial carcinoma cells followed by xenografting into athymic mice. Two endometrial cancer cell lines were employed, those in which transfection and expression of ADM resulted in no effect on growthin vitro (Ishikawa cells) and those in which expressionof exogenous ADM stimulated in vitro growth (RL95.2 cells). A clear enhancement of tumor growth was seen with both cell lines but the effect was far greater with the RL95.2 cells. We conclude that ADM is pro-tumorigenic by stimulating either angiogenesis alone or by stimulating angiogenesis and carcinoma cell growth directly. The combined activities lead to a striking increase in tumor growth. These results provide the first direct evidence of tumorigenic activity of ADM and provide further support for ADMs involvement in tamoxifen induced endometrial neoplasia.

Adrenomedullin↗
PubMed2002

In-vivo angiogenesis and progestogens.

BACKGROUND: Progestogens are used clinically for contraception, to control excessive menstrual bleeding, and to prevent estrogen-induced endometrial hyperplasia. A significant problem with progestogen-only methods of contraception is the induction of breakthrough bleeding. METHODS: The effects of different progestogens on angiogenesis were examined using two approaches. The mouse sponge angiogenesis assay employed direct delivery of the dose ranges achieved therapeutically. The angiogenic response to long-term intrauterine levonorgestrel exposure, compared with unexposed premenopausal endometrium, was also studied. RESULTS: In the mouse sponge assay, norethisterone and medroxyprogesterone acetate stimulated angiogenesis at all doses, but was dose-dependent for levonorgestrel and nomegestrol. Levonorgestrel stimulated angiogenesis in the dose range 100 pmol/l to 10 nmol/l, but not at higher doses. In contrast, nomegestrol acetate stimulated angiogenesis at high, but not low, doses. Expression of acidic and basic fibroblast growth factors, thymidine phosphorylase, vascular endothelial growth factor and adrenomedullin were unaltered in levonorgestrel-exposed endometrium compared with premenopausal controls. Vascular density was increased but endothelial proliferation reduced in levonorgestrel-exposed endometrium. CONCLUSIONS: This is the first report of the direct effects of a wide range of doses of different progestogens on angiogenesis; results suggest that vascular targeting may be an effective strategy to deal with progestogen-induced abnormal bleeding.

Administration, Intravaginal↗