Estetrol is a weak estrogen antagonizing estradiol-dependent mammary gland proliferation.

Estetrol (E4) is a natural estrogen produced exclusively by the human fetal liver during pregnancy. Its physiological activity remains unknown. In contrast to ethinyl estradiol and estradiol (E2), E4 has a minimal impact on liver cell activity and could provide a better safety profile in contraception or hormone therapy. The aim of this study was to delineate if E4 exhibits an activity profile distinct from that of E2 on mammary gland. Compared with E2, E4 acted as a low-affinity estrogen in both human in vitro and murine in vivo models. E4 was 100 times less potent than E2 to stimulate the proliferation of human breast epithelial (HBE) cells and murine mammary gland in vitro and in vivo respectively. This effect was prevented by fulvestrant and tamoxifen, supporting the notion that ERα (ESR1) is the main mediator of the estrogenic effect of E4 on the breast. Interestingly, when E4 was administered along with E2, it significantly antagonized the strong stimulatory effect of E2 on HBE cell proliferation and on the growth of mammary ducts. This study characterizes for the first time the impact of E4 on mammary gland. Our results highlight that E4 is less potent than E2 and exhibits antagonistic properties toward the proliferative effect of E2 on breast epithelial cells. These data support E4 as a potential new estrogen for clinical use with a reduced impact on breast proliferation.

MT1-MMP protects breast carcinoma cells against type I collagen-induced apoptosis.

As invading breast carcinoma cells breach their underlying basement membrane, they become confronted with a dense three-dimensional reactive stroma dominated by type I collagen. To develop metastatic capabilities, invading tumor cells must acquire the capacity to negotiate this novel microenvironment. Collagen influences the fate of epithelial cells by inducing apoptosis. However, the mechanisms used by invading tumor cells to evade collagen-induced apoptosis remain to be defined. We demonstrate that membrane type-1 matrix metalloproteinase (MT1-MMP/MMP-14) confers breast cancer cells with the ability to escape apoptosis when embedded in a collagen gel and after orthotopic implantation in vivo. In the absence of MMP-14-dependent proteolysis, type I collagen triggers apoptosis by inducing the expression of the pro-apoptotic Bcl-2-interacting killer in luminal-like breast cancer cells. These findings reveal a new mechanism whereby MMP-14 activity promotes tumor progression by circumventing apoptosis.

Aetiology and physiopathology of preeclampsia and related forms.

Preeclampsia, a pregnancy-specific syndrome characterized by hypertension, proteinuria and oedema, resolves on placental delivery. Its pathogenesis is thought to be associated to a hypoxic placenta. Placental hypoxia is responsible for the maternal vascular dysfunction via the increased placental release of anti-angiogenic factors such as soluble flt1 and endoglin. These soluble receptors bind VEGF, PLGF and TGFbeta1 and 3 in the maternal circulation, causing endothelial dysfunction in many maternal tissues. Despite these recent and important new molecular findings, it is important to consider that normal pregnancy is also characterized by systemic inflammation, oxidative stress and alterations in levels of angiogenic factors and vascular reactivity. Both the placenta and maternal vasculatures are major sources of reactive oxygen and nitrogen species which can produce powerful pro-oxidants that covalently modify proteins and alter vascular function in preeclampsia. Finally, the recent demonstration of activating auto-antibodies to the Angiotensin 1 receptor that experimentally play a major pathogenic role in preeclampsia further indicates the pleiotropism of aetiologies of this condition.

Plasma oxytocin levels and anxiety in patients with major depression.

Cerebrospinal fluid and plasmatic levels of oxytocin (OT) have been found to change in mood disorders. In post-mortem studies, the numbers of OT-expressing neurons in the paraventricular nucleus have been reported to be increased. Moreover, OT is considered as an endogenous antistress hormone. It has also revealed antidepressive effects. OT may contribute to the dysregulation of the HPA system in major depression. The aim of the study was to assess a possible relationship between anxiety and plasma oxytocin (OT) levels in depressive patients. Severity of depression was estimated with the Hamilton Depression Rating Scale and anxiety by using the Spielberger State-Anxiety Inventory. Results showed a significant negative correlation between oxytocin and the scored symptoms depression (r=-0.58, p=0.003) and anxiety (r=-0.61, p=0.005).

Ontogenesis and functional aspects of oxytocin and vasopressin gene expression in the thymus network.

Ontogenesis of oxytocin (OT) and vasopressin (VP) gene expression and function were investigated in murine thymus. OT and VP transcripts were detected in the thymus on embryonic days 13 and 15, respectively. Corresponding messenger RNAs were evidenced in thymic epithelial cells by in situ hybridization with a neurophysin probe. From all OT and VP receptors, only OTR was expressed by all T-cell subsets, while V1bR was found in double positive and single positive CD8 cells. In fetal thymic organ cultures, OTR antagonist d[D-Tyr(Et)2, Thr4]OVT increased early apoptosis of CD8 cells, while V1bR antagonist (Sanofi SSR149415) inhibited T-cell differentiation, and favored CD8 T-cell commitment.

Oxytocin- and vasopressin-induced growth of human small-cell lung cancer is mediated by the mitogen-activated protein kinase pathway.

Malignant growth of small-cell lung carcinoma is promoted by various neuroendocrine autocrine/paracrine loops. Therefore, to interfere with this mitogenic process, it is crucial to elucidate the mechanisms involved. It is known that the oxytocin (OT) and vasopressin (VP) genes, normally transcriptionally restricted in their expression, are activated in small-cell lung cancer (SCLC), concomitantly with expression of their receptors (OTR, V1aR, V1bR/V3R and V2R). The aim of the present study was to characterize, in concentrations close to physiological and pharmacological conditions, intracellular signalling events triggered by OT and VP binding to their specific receptors in SCLC cells and to identify factors mediating OT- and VP-induced mitogenic effects on SCLC. Known agonists for OTR ([Thr4,Gly7]OT) and V1aR (F180), in addition to OT and VP, were able to elicit increases in cytosolic Ca2+ levels and this effect could be blocked using an OTR antagonist (OVTA) or a V1aR antagonist (SR49059) respectively. There was no activation of the cAMP pathway detected after VP, dDAVP (a V2R agonist), or OT treatment. Stimulation of SCLC cells with OT and VP led to an increase of extracellular signal-regulated kinase (ERK) 1/2 phosphorylation, maximal at 5 min, and the subsequent phosphorylation of its downstream target p90 ribosomal S6 kinase (p90RSK). Pre-incubation with OVTA and SR49059, and with inhibitors of phospholipase C (PLC), protein kinase C (PKC), mitogen-activated protein kinase/ERK kinase (MEK) 1/2 and a Ca2+ chelator significantly reduced OT- and VP-induced ERK1/2 phosphorylations. OVTA, SR49059 as well as MEK1/2 and PKC inhibitors also downregulated OT- and VP-induced p90RSK phosphorylation. In [3H]thymidine-uptake experiments, we subsequently observed that PLC, Ca2+, PKC and ERK1/2 are absolutely required for the OT- and VP-stimulated SCLC cellular growth process. In conclusion, the results presented here indicate that OT- and VP-induced mitogenic effects on SCLC are respectively mediated by OTR and V1aR signalling and that this mitogenic signalling passes through the phosphorylation of ERK1/2 and p90RSK in a PLC-, Ca2+-, PKC- and MEK1/2-dependent pathway.

Daytime 50 Hz magnetic field exposure and plasma melatonin and urinary 6-sulfatoxymelatonin concentration profiles in humans.

Concern about the health effects of extremely low frequency (ELF) magnetic fields (MF) has been raised by epidemiological studies indicating an association between certain cancers and living near power lines or working in high electric field environments. Alterations in pineal function have been proposed as a mechanism through which power-frequency MFs may interact with living organisms. A double blind laboratory study was performed to evaluate daytime exposure effects of 100 microT root mean square (rms) 50 Hz MF. Three head exposure sessions of 30 min each were performed: sham, continuous, and intermittent (15 s on/off cycles) MFs were presented to each subject in early or late afternoon (13:30 or 16:30 hr). Twenty-one healthy male volunteers (20-27 yr old) participated in these 3-weekly experimental conditions. Blood samples were drawn for serum melatonin measurement, hourly at night (from 20:00 to 07:00 hr) under controlled environmental conditions. Urinary excretion of 6-sulfatoxymelatonin (aMT6s), the main melatonin metabolite, was measured for a 17 hr period, by means of urine samples taken at 19:00 hr (14:00-19:00 hr "afternoon period"), 23:00 hr (19:00-23:00 hr "evening period"), and 07:00 hr, day 2 (23:00-07:00 hr day 2 "night-time period"). There were no significant differences in either plasma melatonin or in aMT6s excretion profiles in the three experimental conditions. However, a tendency for a smaller increase of night-time urinary aMT6s after continuous MF exposure was found (P=0.08) particularly in men with the lower excretion rate of aMT6s ("Low Group") (P=0.07). We conclude that this study does not indicate that daytime acute MF exposure influences either melatonin secretion or aMT6s excretion. Inter-individual differences in pineal production of melatonin, however, have to be taken into account in further studies.

Novel plasma extraction procedure and development of a specific enzyme-immunoassay of oxytocin: application to clinical and biological investigations of small cell carcinoma of the lung.

Paraneoplastic secretion of the lactation-inducing hormone oxytocin (OT) has been reported in about 30% of cases of small cell carcinoma of the lung (SCCL). In order to investigate the role of OT in the biology of SCCL tumours, a specific enzyme-immunoassay (EIA) for OT, which can be applied to both human plasma and culture medium, has been developed. OT EIA is performed on 96-well microtiter plates coated with a rabbit polyclonal antibody (Ab) anti-OT (04). This antibody does not exhibit any significant cross-reactivity either with vasopressin (VP) or with vasotocin (VT). The immunological reaction involving Ab anti-OT is a competition between the tracer (biotinylated OT) and synthetic OT (standard curve) or OT present in biological samples. In order to limit interference induced by plasma proteins, plasma samples are filtrated by a one-step centrifugation on centricon YM-3 (cut-off 3000 Da). After plasma filtration, 90.7 +/- 5.1 (SD) % (n = 22) immunoreactive (IR) OT is recovered. The sensitivity of OT EIA is 1 pmol/L, while intra- and inter-assay coefficients of variation (CV) are around 3.41% and 2.84%, respectively. In healthy volunteers, plasma IR OT is 7.28 +/- 4.49 (SD) pmol/L (n = 32) with no gender difference. As shown by the data both from plasma of SCCL patients and from supernatants and cell contents of SCCL cell lines, this EIA procedure offers a novel, reproducible, specific and sensitive method for the measurement of IR OT.

[New players in the physiopathology of water metabolism: the aquaporins]. / De nouveaux acteurs dans la physiopathologie du métabolisme de l'eau: les aquaporines.

Aquaporins are transmembrane proteins mediating water transport across plasma membrane of animal, vegetal or bacterial cells. Among the ten aquaporins known in mammals, six are located in kidney and take part in urine concentration. AQP2 is vasopressin regulated, it is the only family member to be implicated in human pathology, such as nephrogenic diabetes insipidus, congestive heart failure, hepatic cirrhosis, nephrotic syndrome or SIADH. Aquaporins are expressed in a wide variety of tissues, such as brain or gastrointestinal tractus, and suggest a role in water tissue exchange, but their real function is still not define. To know the physiological impact of aquaporins, AQP1, AQP3, AQP4 and AQP5 knockout mice have been created and their phenotype analysed.