Biomedical subjects

H Jarry

Publications and source records attributed to H Jarry.

At least 19 recordsLinked to original sources

PubMed2006

Proliferation and apoptosis of hippocampal granule cells require local oestrogen synthesis.

Ovarian oestrogens have been demonstrated to influence neurogenesis in the dentate gyrus. As considerable amounts of oestrogens are synthesized in hippocampal neurones, we focused on the role of hippocampus-derived estradiol on proliferation and apoptosis of granule cells in vitro. We used hippocampal dispersion cultures, which allowed for cultivation of the cells under steroid- and serum-free conditions and monitoring of oestrogen synthesis. To address the influence of hippocampus-derived estradiol on neurogenesis, we inhibited oestrogen synthesis by treatment of hippocampal cell cultures with letrozole, a specific aromatase inhibitor. Alternatively, we used siRNA against steroidogenic acute regulatory protein (StAR). The number of proliferative cells decreased whereas the number of apoptotic cells increased dose-dependently, in response to reduced estradiol release into the medium after treatment with letrozole. This also held true for siRNA against StAR transfected cell cultures. Application of estradiol to the medium had no effect on proliferation and apoptosis whereas the anti-proliferative and pro-apoptotic effects of StAR knock-down and letrozole treatment were restored by treatment of the cultures with estradiol. Our findings suggest that neurogenesis and apoptosis in the hippocampus require a defined range of estradiol concentrations that is physiologically provided by hippocampal cells but not by gonads.

Animals↗

PubMed2005

Comparison of effects of estradiol (E2) with those of octylmethoxycinnamate (OMC) and 4-methylbenzylidene camphor (4MBC)--2 filters of UV light - on several uterine, vaginal and bone parameters.

OMC and 4MBC are 2 absorbers of ultraviolet light which are used in unknown quantities in sunscreens, cosmetics and plastic products to protect against UV light-induced damage of the skin or of fragrances or plastic material. From there, they were shown to reach surface water and/or by direct contamination or ingestion the human. Under various conditions in mice and rats, both substances were shown to be estrogenic. Therefore, we compared in vitro and in vivo the effects of chronic application of these compounds at 2 doses with those of E2, all administered via food. No signs of toxicity were observed under application of 0.6 mg E2, 57.5 or 275 mg of OMC, 57.5 or 250 mg of 4MBC; these amounts were ingested with 21 g of control food, 17.8 g E2 food, 20.6 g or 22.3 g OMC food and 23.7 or 22.8 g 4MBC food. In the uterus, vagina and bone, E2 exerted the expected stimulatory effects which were minimally shared by OMC and 4MBC in the uterus and vagina as assessed by histology and determination of a variety of estrogen-regulated genes such as insulin-like growth factor-1, progesterone receptor and estrogen receptor beta. In the bone, OMC had no effect, while 4MBC shared the antiosteoporotic effects of E2 as measured by quantitative computer tomography in the metaphysis of the tibia. The mechanism of action of 4MBC, however, appears to be different as E2 reduced serum osteocalcin and the C-terminal breakdown products of collagen-1alpha1 which were both increased by 4MBC. Taken together, these data indicate a very weak estrogenic effect of OMC and 4MBC in the uterus and in the vagina but not in the bone where 4MBC exerted antiosteoporotic effects by a different mechanism than E2.

Animals↗

PubMed2005

Effects of estradiol-17beta, testosterone and a black cohosh preparation on bone and prostate in orchidectomized rats.

Estradiol (E2) and testosterone (T) effectively prevent orchidectomy (orx) induced osteoporosis. T, however, stimulates prostate proliferation which may lead to malignancy. We showed that a Cimicifuga racemosa (CR) preparation had bone-sparing effects without exerting estrogenic effects in the uterus. We studied therefore whether a CR preparation has also antiosteoporotic effects in orx rats substituted with E2, T or CR via pelleted food over a period of 3 months. Average daily intake per animal was: T: 25 mg; E2: 0.325 mg, CR low dose: 33 mg; CR high dose: 133 mg. E2, T and CR at the high dose partially prevented development of osteoporosis as measured by quantitative computer tomography in the metaphysis of the tibia. E2, but not T or CR reduced serum osteocalcin and the metabolic products of collagen-1alpha1. Gene expression of collagen-1alpha1 and tartrate-resistant acid phosphatase was decreased by E2 and the higher dose of the CR extract but increased in the T-treated animals. In the prostate T inhibited androgen receptor, estrogen receptor alpha and insulin-like growth factor-1 gene expression but stimulated the expression of the ERbeta gene. These effects were not shared by E2 or both doses of the CR extract. It is concluded that E2, T and CR exert antiosteoporotic effects in the metaphysis of the tibia of orx rats. T has profound effects in the prostate which were not seen in the E2- and CR-treated animals. Therefore, the Cimicifuga racemosa extract BNO 1055 may be useful to prevent osteoporosis in aged male patients with reduced testosterone production.

Analysis of Variance↗

PubMed2005

Cimicifuga racemosa extract BNO 1055 inhibits proliferation of the human prostate cancer cell line LNCaP.

Extracts from black cohosh (Cimicifuga racemosa, CR) exert an anti-proliferative action in human breast cancer cell cultures, which has been attributed to an anti-estrogenic effect. However, CR constituents do not bind to either of the known estrogen receptors. Thus, the anti-tumor effect of CR me be mediated by mechanisms not involving these receptors. Polycyclic aromatic hydrocarbons are toxic environmental pollutants, which indirectly act as anti-estrogens by activating the aryl hydrocarbon receptor (AhR). The AhR is widely expressed in mammalian tissues and tumors. A recent screening study demonstrated activation of the AhR by a variety of herbal extracts, among others, CR. Since activation of the AhR causes inhibition of growth of prostate cancer cells, we addressed the question, whether CR may not only inhibit growth of breast cancer--but also of prostate cancer cells. In the AhR ligand assay, the CR extract BNO 1055 reduced tracer binding to 71% of the control demonstrating interaction of constituents of this extract with the receptor. Under basal as well as under estradiol- and dihydrotestosterone stimulated conditions, the CR extract dose dependently inhibited proliferation of LNCaP cells. A significant reduction of cell growth was observed at a concentration as low as 50 ng/ml. Thus, it is demonstrated for the first time that CR compounds potently inhibit the growth of human prostate cancer cells in vitro. This anti-proliferative effect may be mediated via the AhR.

Antineoplastic Agents, Phytogenic↗

PubMed2005

Different effects of agonistic vs. antagonistic gnrh-analogues (triptorelin vs. cetrorelix) on bone modeling and remodeling in peripubertal female rats.

Little is known about the effects of antagonistic GnRH analogues vs. agonists on bone strength, specifically in context of treating precocious puberty. Peripubertal female rats were treated from postnatal day 25 - 36 with either the GnRH agonist triptorelin (TRIP) or the antagonist cetrorelix (CET). Using peripherial quantitative computerized tomography (pQCT) we investigated effects on bone parameters. Onset of puberty was retarded by both analogues as measured by prevention of vaginal opening at 36 d of age and reduced uterine weights. In the tibia, cortical content, cortical area related to body weight, and periosteal circumference related to weight were significantly reduced in CET-treated rats - indicating reduced bone modeling and reduced bone strength (cortical circumference related to body weight: CET 0.066 +/- 0.001 vs. TRIP 0.068 +/- 0.001 vs. controls 0.071 +/- 0.001 mm/g, mean +/- SEM, p < 0.05 CET vs. controls; cortical area related to body weight: CET 3.87 +/- 0.46 vs. TRIP 6.80 +/- 0.63 vs. controls 8.07 +/- 1.13, x 10 (-3) mm (2)/g, p < 0.001 CET vs. controls; cortical content: CET 0.316 +/- 0.038 vs. TRIP 0.546 +/- 0.051 vs. controls 0.624 +/- 0.089 mg/mm, p < 0.01 CET vs. controls). In conclusion, although both CET and TRIP inhibit puberty in rats, cortical thinning was only seen in CET-treated rats. This indicates that GnRH antagonist treatment might cause reduced bone strength which is partly comparable to postmenopausal bone loss. When using new GnRH antagonists for treating precocious puberty in humans, parameters for bone strength and mineralization should be monitored.

Animals↗

PubMed2004

Pure estrogenic effect of benzophenone-2 (BP2) but not of bisphenol A (BPA) and dibutylphtalate (DBP) in uterus, vagina and bone.

UNLABELLED: Contradictory results whether the endocrine disrupters (ED) benzophenone-2 (BP2), bisphenol A (BPA) and dibutylphtalate (DBP) exert estrogenic effects have been published. Selective estrogen receptor modulators (SERMs) exert estrogenic effects in some but not in all organs and ED may be SERMs. Therefore, we studied their binding properties to recombinant ERalpha and ERbeta protein and their effects in the uterus, vagina and bone of ovariectomized rats. BP2 bound to both receptor subtypes, while BPA had a relatively high ERbeta selectivity. DBP did not bind to ERalpha but with a low affinity to ERbeta. In the uterus, only E2 and BP2 increased uterine weight and the complement C3 but decreased ERbeta gene expression. Discrete effects of BPA and DBP in the uterus were found upon histological examination. In the vagina, BP2 but not BPA and DBP had clear estrogenic effects. E2 and BP2 had antiosteoporotic effects in the metaphysis of the tibia. The serum surrogate parameters of bone metabolism, i.e. osteocalcin and the cross (rat) laps were significantly reduced by E2, an effect shared with BP2 but not by the two other EDs. THE CONCLUSION: BP2 acts as ERalpha and ERbeta agonist mimicking effects of E2, while the effects of BPA and DBP are not pure estrogenic.

Animals↗

PubMed2004

Belamcanda chinensis and the thereof purified tectorigenin have selective estrogen receptor modulator activities.

Belamcanda chinensis (BC) belongs to the family of iridaceae and the isoflavone tectorigenin has been isolated from the rhizome of this plant. Whether this isoflavone has estrogenic, possibly selective estrogen receptor modulator activities and if so, whether they are mediated via the estrogen receptor alpha or beta is unknown at present. Therefore, we performed binding studies with recombinant human ERalpha and ERbeta to show that tectorigenin binds to both receptor subtypes. In ERalpha-expressing MCF7 and ERbeta-expressing MDA-MB231 reporter gene transfected cells tectorigenin causes transactivation. When given intravenously to ovariectomized (ovx) rats, it inhibits pulsatile pituitary LH secretion. In postmenopausal women estrogen-unopposed LH pulses correlate with hot flushes. Therefore, suppression of pulsatile LH secretion may be beneficial in women suffering from hot flushes. Upon chronic application to ovx rats a BC extract containing 5% Belamcanda at a daily dose of 33 mg or 130 mg of the extract had no effect on uterine weight or on estrogen-regulated uterine gene expression while estrogenic effects in the bone, on bone mineral density of the metaphysis of the tibia could be established. Hence, tectorigenin may have antiosteoporotic effects also in postmenopausal women. Immunohistochemical staining of proliferating cell nuclear antigen--a proliferation marker--in the mammary gland did not indicate a mammotrophic effect of the tectorigenin-containing BC extract at both tested doses. In summary, tectorigenin or the B. chinensis extract containing tectorigenin had a strong hypothalamotropic and osteotropic effect but no effect in the uterus or the mammary gland. Therefore, tectorigenin may be in the future a clinically useful selective estrogen receptor modulator.

Animals↗

PubMed2004

Inhibition of telomerase activity and secretion of prostate specific antigen by silibinin in prostate cancer cells.

PURPOSE: The androgen sensitive prostate cancer cell line LNCaP is strongly positive for dihydrotestosterone (DHT) dependent telomerase activity, which is an important factor in cellular immortality and carcinogenesis. In this study we determined the potential of silibinin as an anticancer drug that down-regulates telomerase activity and prostate specific antigen (PSA) together with the co-activator of the androgen receptor prostate epithelium specific Ets transcription factor. MATERIALS AND METHODS: LNCaP cells were treated with various concentrations of silibinin in the presence or absence of 5alpha-DHT. We used real-time reverse transcriptase-polymerase chain reaction to quantify mRNA expression of PSA, prostate epithelium specific Ets transcription factor and the catalytic subunit of telomerase vs the housekeeping gene porphobilinogen deaminase with gene specific, dual labeled fluorescence probes. PSA secretion from LNCaP cells in conditioned medium was measured with an Elecsys System 2010 (Roche Diagnostics, Mannheim, Germany) and telomerase activity in extracts from LNCaP cells was measured with a TRAP (telomeric repeat amplification protocol) assay. RESULTS: Silibinin down-regulated PSA mRNA expression and PSA secretion in conditioned medium. Simultaneous stimulation with silibinin and 10(-8) M DHT also resulted in PSA down-regulation, whereas DHT alone increased PSA secretion. Telomerase catalytic subunit mRNA decreased significantly after silibinin stimulation. Telomerase activity was down-regulated by silibinin and stimulated by DHT. The 2 agents in combination resulted in telomerase down-regulation. CONCLUSIONS: The down-regulation of PSA by silibinin and its counteraction on DHT effects indicate that this compound can interact with the expression of genes that are regulated through the androgen receptor. Silibinin can also inhibit the telomerase activity that mediates cell immortality and carcinogenesis. The 2 effects underline the possible therapeutic use of silibinin as an antiproliferative agent in intervention for prostate cancer.

Gene Expression Regulation, Neoplastic↗

PubMed2004

Urodynamic effects of estradiol (E2) in ovariectomized (ovx) rats.

Whether estrogens have a beneficial effect in the urinary bladder to prevent or to delay occurrence of urinary bladder incontinence is an open question. Good animal models are missing. Therefore, in ovariectomized (ovx) rats we studied the effects of estradiol (E2) administered with food for 3 mo on urodynamic properties of the urinary bladder and the urethra. A biluminal catheter with one outlet in the bladder and another in the urethra in juxtaposition to the external sphincter was inserted in isoflurane anaesthetized animals. Within 2 x 30 s (1 min apart) 0.5 mL Ringer's solution was infused into the bladder and the inner vesicular and urethral pressure were recorded. In comparison to ovx estradiol-treated rats, ovx animals had significantly (p < 0.05) lower vesicular and urethral pressure. In the sham-treated ovx animals vesicular and urethral pressures were unstable and appeared uncoordinated, whereas estrogens increased vesicular and urethral pressure in a coordinated way, such that in these animals leaked volume was significantly lower than in the sham-treated ovx animals. By means of quantitative RT-PCR we demonstrate that the upper and lower part of the bladder and the urethra express estrogen receptor of the alpha- and beta-subtype (ER alpha and beta) and nerve growth factor, which is associated with painful sensations in inflamed urinary bladders. E2 downregulated both ERs in the bladder but not in the urethra, while NGF gene expression was downregulated in the urethra but unaffected by E2 in the bladder. It is concluded that estrogen deprivation causes uncoordinated function of the detrusor and sphincter muscles and that this effect can be prevented by estradiol.

Animals↗

PubMed2003

Pharmacology of Cimicifuga racemosa extract BNO 1055 in rats: bone, fat and uterus.

OBJECTIVES: Hormone replacement therapy (HRT) has therapeutic effects on climacteric complaints and prevents osteoporosis. Owing to the increased risks of breast cancer and cardiovascular diseases, patients look for alternatives. Cimicifuga racemosa (CR) preparations might be an alternative, because they proved to reduce climacteric complaints as efficiently as conjugated estrogens without exerting estrogenic effects in the uterus. Whether CR has positive effects on bone and in fat tissue is currently unknown. Therefore, osteoprotective effects of the CR extract BNO 1055 and an influence on fat tissue were studied in ovariectomized rats. METHODS: Bone mineral density (BMD) of the tibia of ovariectomized (ovx) rats was determined by computer-assisted tomography (CT). CT scans of fat depots were perimetrically quantified. Bone turnover (osteocalcin, crosslaps) and lipocyte activity (leptin) were also determined. Uterine weights were measured and gene expression of estrogen-regulated uterine genes (IGF-1, ERbeta) was determined by RT-PCR. RESULTS: Treatment of the ovx rats over a period of 3 months with E(2) and the CR extract BNO 1055 showed osteoprotective effects; both significantly reduced the loss of BMD in tibia. Serum osteocalcin levels were significantly reduced by both treatments, whereas only E(2), but not BNO 1055, reduced serum crosslaps. A paratibial fat depot and serum leptin concentration were also significantly reduced. In contrast to E(2), the CR extract showed no effect on uterine weight and gene expression of E(2)-regulated genes. CONCLUSION: The CR extract BNO 1055 exerted estrogenic effects in the bone (particularly in osteoblasts) and in fat tissue, but not in the uterus of ovx rats. The extract appears to contain rat organ-specific selective estrogen receptor modulators (SERMs), and if these findings can be approved in human it may be an alternative to HRT.

Adipose Tissue↗

PubMed2003

Plasma gamma-amino-butyric acid (GABA) levels in cholecystokinine-tetrapeptide (CCK-4) induced anxiety.

INTRODUCTION: Dysregulation of the GABA system is supposed to play an important role in the pathophysiology of panic disorder. Moreover, prior investigations revealed an association between GABA plasma levels and experimental induced panic with lactate. To evaluate a possible relationship between plasma GABA and CCK-4 induced panic plasma GABA levels in healthy volunteers were investigated. METHODS: 12 healthy subjects were challenged with 50 micro g CCK-4. Blood samples for determination of plasma GABA were drawn at baseline, 5 and 10 minutes after CCK-4 injection. RESULTS: Plasma GABA levels did not change significantly during the CCK-4 challenge as revealed by ANOVA for repeated measurements. There was no correlation between baseline GABA levels and anxiogenic response to CCK-4. CONCLUSION: In contrast to previous findings with lactate our study does not suggest a possible relationship between plasma GABA levels and experimental induced panic with CCK-4.

Analysis of Variance↗

PubMed2003

Silymarin is a selective estrogen receptor beta (ERbeta) agonist and has estrogenic effects in the metaphysis of the femur but no or antiestrogenic effects in the uterus of ovariectomized (ovx) rats.

Silymarin is a widely used standardized mixture of flavonolignans and its major component Silybinin binds to cytosolic estrogen receptors. Here, we demonstrate that this binding is exclusive to the estrogen receptor beta (ERbeta). Treatment of ovariectomized (ovx) rats with silymarin or estradiol (E2) may allow differentiation of biological effects mediated by the ERalpha or ERbeta. E2 inhibited serum LH, cholesterol, LDL and HDL concentrations in the blood and increased gene expression of IGF1, HbEGF and C3 in the uterus, while silymarin was totally ineffective or antagonistic in altering these parameters. Both, E2 and silymarin inhibited expression of uterine ERbeta gene. Hence, in the pituitary, liver (where the lipoproteins are synthesized) and uterus E2 acts primarily via the ERalpha. Exclusive estrogenic effects of silymarin were observed in the metaphysis of the femur (MF), on osteoblast parameters (gene expression of IGF1, TGFbeta1, osteoprotegerin, collagen-1alpha1, osteocalcin (OC)) and on the osteoclast activity marker tartrate resistant acid phosphatase (TRAP) gene expression of adult ovx rats. Our RT-PCR method detects ERbeta gene expression in all organs including developing bones but not in the MF of adult ovx rats. We conclude therefore, that the effects of silymarin in this part of the bone cannot be exerted via the ERalpha because it does not bind to this receptor subtype. Despite the failure to detect ERbeta mRNA in the MF of our animals the possibility exists that ERbeta protein is present and may mediate the effects of silymarin. Another possibility may be that the effect of silymarin and therefore possibly also of E2 in the MF may be mediated via other possibly not yet identified receptors or via an ERbeta splice variant which is not detected by our PCR-method.

Animals↗

PubMed2003

Chaste tree (Vitex agnus-castus)--pharmacology and clinical indications.

Extracts of the fruits of chaste tree (Vitex agnus castus = AC) are widely used to treat premenstrual symptoms. Double-blind placebo-controlled studies indicate that one of the most common premenstrual symptoms, i.e. premenstrual mastodynia (mastalgia) is beneficially influenced by an AC extract. In addition, numerous less rigidly controlled studies indicate that AC extracts have also beneficial effects on other psychic and somatic symptoms of the PMS. Premenstrual mastodynia is most likely due to a latent hyperprolactinemia, i.e. patients release more than physiologic amounts of prolactin in response to stressful situations and during deep sleep phases which appear to stimulate the mammary gland. Premenstrually this unphysiological prolactin release is so high that the serum prolactin levels often approach heights which are misinterpreted as prolactinomas. Since AC extracts were shown to have beneficial effects on premenstrual mastodynia serum prolactin levels in such patients were also studied in one double-blind, placebo-controlled clinical study. Serum prolactin levels were indeed reduced in the patients treated with the extract. The search for the prolactin-suppressive principle(s) yielded a number of compounds with dopaminergic properties: they bound to recombinant DA2-receptor protein and suppressed prolactin release from cultivated lactotrophs as well as in animal experiments. The search for the chemical identity of the dopaminergic compounds resulted in isolation of a number of diterpenes of which some clerodadienols were most important for the prolactin-suppressive effects. They were almost identical in their prolactin-suppressive properties than dopamine itself. Hence, it is concluded that dopaminergic compounds present in Vitex agnus castus are clinically the important compounds which improve premenstrual mastodynia and possibly also other symptoms of the premenstrual syndrome.

Animals↗

PubMed2002

Phytoestrogens for hormone replacement therapy?

Due to some severe side effects "classical" hormone replacement therapy (HRT) is currently being challenged by a therapy with phytoestrogens. Particularly soy and red clover derived isoflavones are advertised as selective estrogen receptor modulators (SERMs) with only desired and no undesired estrogenic effects. Evidence that this is the case however is scarce. Most studies investigating climacteric complaints did not find beneficial effects. A proposed beneficial effect on mammary cancer is unproven. The majority of studies however indicate an antiosteoporotic effect of isoflavones, while putative beneficial effects in the cardiovascular system are questionable due to the fact that estradiol which--like isoflavones--increase HDL and decrease LDL concentrations appear not to prevent arteriosclerosis in the human. In the urogenital tract, including the vagina, soy and red clover derived isoflavones are without effects. Cimicifuga racemosa extracts are traditionally used for the treatment of climacteric complaints. Evidence is now available that the yet unknown compounds in Cimicifuga racemosa extracts prevent climacteric complaints and may also have antiosteoporotic effects.

Bone and Bones↗

PubMed2002

[Pharmacologic and clinical studies using Cimicifuga racemosa in climacteric complaints].

Climacteric complaints are caused by a decrease in estrogen production and are characterized by neurovegetative and psychic complaints. Hot flushes represent the leading symptom, in addition excitability, irritability and sleep disturbances are reported. These complaints are usually treated with estrogens, but extracts of Cimicifuga racemosa are used for this indication, too. Clinical studies gave evidence for the efficacy of Cimicifuga extracts in patients with climacteric symptoms. In pharmacological experiments Cimicifuga extracts exhibited organ specific estrogenic effects and were characterised as selective estrogen-receptor-modulators. In addition pronounced effects on the central nervous system were shown. Taking these relevant therapeutic properties into account further experimental and clinical studies seem to be necessary and promising.

Aged↗

PubMed2001

Plasticity of rat central inhibitory synapses through GABA metabolism.

1. The production of the central inhibitory transmitter GABA (gamma-aminobutyric acid) varies in response to different patterns of activity. It therefore seems possible that GABA metabolism can determine inhibitory synaptic strength and that presynaptic GABA content is a regulated parameter for synaptic plasticity. 2. We altered presynaptic GABA metabolism in cultured rat hippocampal slices using pharmacological tools. Degradation of GABA by GABA-transaminase (GABA-T) was blocked by gamma-vinyl-GABA (GVG) and synthesis of GABA through glutamate decarboxylase (GAD) was suppressed with 3-mercaptopropionic acid (MPA). We measured miniature GABAergic postsynaptic currents (mIPSCs) in CA3 pyramidal cells using the whole-cell patch clamp technique. 3. Elevated intra-synaptic GABA levels after block of GABA-T resulted in increased mIPSC amplitude and frequency. In addition, tonic GABAergic background noise was enhanced by GVG. Electron micrographs from inhibitory synapses identified by immunogold staining for GABA confirmed the enhanced GABA content but revealed no further morphological alterations. 4. The suppression of GABA synthesis by MPA had opposite functional consequences: mIPSC amplitude and frequency decreased and current noise was reduced compared with control. However, we were unable to demonstrate the decreased GABA content in biochemical analyses of whole slices or in electron micrographs. 5. We conclude that the transmitter content of GABAergic vesicles is variable and that postsynaptic receptors are usually not saturated, leaving room for up-regulation of inhibitory synaptic strength. Our data reveal a new mechanism of plasticity at central inhibitory synapses and provide a rationale for the activity-dependent regulation of GABA synthesis in mammals.

3-Mercaptopropionic Acid↗

PubMed2001

Analysis of exonic splicing enhancers in the mouse gonadotropin-releasing hormone (GnRH) gene.

We have previously reported that efficient removal of the first intron (intron A) of gonadotropin-releasing hormone (GnRH) pre-mRNA is the prerequisite event for post-transcriptional regulation. In the present study, using an in vitro HeLa splicing system, we examined the enhancing activities of exonic elements for GnRH pre-mRNA splicing. While not excised by exon 2 alone, intron A was efficiently excised when exon 3 and/or exon 4 was combined with exon 2, suggesting the presence of exonic splicing enhancers (ESEs) in exons 3 and 4. Purine-rich sequences located in the border of exons 2 and 3 (denoted ESE3) and in exon 4 (ESE4) revealed strong splicing enhancing activities. Mutation in ESE3 decreased pre-mRNA splicing, while mutation in purine-rich sequences in exon 2 did not. We further analyzed the functional activity of ESE4 by mutations or deletions of the ESE4 sequence that consists of three purine-repeats separated by two spacers and a putative hairpin constructing sequence. An UV cross-linking assay using the RNA sequence of ESE4 examined the presence of ESE4-specific binding proteins in the nuclear extracts from GT1 hypothalamic GnRH neurons. Collectively, this study indicates that a sequence context of ESE4 and its binding proteins may be crucially involved in enhanced GnRH pre-mRNA splicing. However, it should be further clarified as to which splicing factor(s) is responsible for ESE4-dependent GnRH pre-mRNA splicing.

Animals↗

PubMed2001

Reduction of gamma-aminobutyric acid-ergic neurotransmission as a putative mechanism of radiation induced activation of the gonadotropin releasing-hormone-pulse generator leading to precocious puberty in female rats.

Brain irradiation in prepubertal children with malignomas can cause precocious puberty. A selective cranial cobalt (Co(60))-irradiation technique has been developed in rats. In two experiments early juvenile (13-15 days old) female rats received a single dose of 5 Gy or sham irradiation. At pubertal age (post-natal days 33-34) irradiated rats had higher serum estradiol and luteinizing hormone levels. In experiment 1 irradiated rats had higher gonadotropin releasing-hormone (GnRH) mRNA levels in the preoptic area compared to controls (P<0.05). In experiment 2 the release rates of gamma-aminobutyric acid (GABA) in vitro from preoptic mediobasal hypothalamic areas of irradiated rats were significantly reduced after stimulation with the GABA(A) receptor agonist muscimol (maximum values 4607+/-804 vs. 7399+/-1048 pM in controls, mean+/-SEM, P<0.05). Radiation induced central precocious puberty might be caused by damage to inhibitory GABAergic neurons leading to premature activation of the GnRH-pulse generator.

Animals↗