RESUMEN
Damage observed in the hippocampus of the adult spontaneously hypertensive rat (SHR) resembles the neuropathology of mineralocorticoid-induced hypertension, supporting a similar endocrine dysfunction in both entities. In the present study, we tested the hypothesis that increased expression of the hippocampal mineralocorticoid receptor (MR) in SHR animals is associated with a prevalent expression of pro-inflammatory over anti-inflammatory factors. Accordingly, in the hippocampus, we measured mRNA expression and immunoreactivity of the MR and glucocorticoid receptor (GR) using a quantitative polymerase chain reaction and histochemistry. We also measured serum-glucocorticoid-activated kinase 1 (Sgk1 mRNA), the number and phenotype of Iba1+ microglia, as well as mRNA expression levels of the pro-inflammatory factors cyclo-oxygenase 2 (Cox2), Nlrp3 inflammasome and tumour necrosis factor α (Tnfα). Expression of anti-inflammatory transforming growth factor (Tgf)ß mRNA and the NADPH-diaphorase activity of nitric oxide synthase (NOS) were also determined. The results showed that, in the hippocampus of SHR rats, expression of MR and the number of immunoreactive MR/GR co-expressing cells were increased compared to Wistar-Kyoto control animals. Expression of Sgk1, Cox2, Nlrp3 and the number of ramified glia cells positive for Iba1+ were also increased, whereas Tgfß mRNA expression and the NADPH-diaphorase activity of NOS were decreased. We propose that, in the SHR hippocampus, increased MR expression causes a bias towards a pro-inflammatory phenotype characteristic for hypertensive encephalopathy.
Asunto(s)
Hipocampo/metabolismo , Inflamación/metabolismo , Neuronas/metabolismo , Receptores de Mineralocorticoides/metabolismo , Animales , Ciclooxigenasa 2/genética , Ciclooxigenasa 2/metabolismo , Proteínas Inmediatas-Precoces/genética , Proteínas Inmediatas-Precoces/metabolismo , Masculino , Microglía/metabolismo , Óxido Nítrico Sintasa/genética , Óxido Nítrico Sintasa/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKY , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Receptores de Mineralocorticoides/genética , Factor de Crecimiento Transformador beta/genética , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
Spontaneously hypertensive rats (SHR) show pronounced hippocampus alterations, including low brain-derived neurotrophic factor (BDNF) expression, reduced neurogenesis, astrogliosis and increased aromatase expression. These changes are reverted by treatment with 17ß-oestradiol. To determine which oestradiol receptor (ER) type is involved in these neuroprotective effects, we used agonists of the ERα [propylpyrazole triol (PPT)] and the ERß [diarylpropionitrite (DPN)] given over 2 weeks to 4-month-old male SHR. Wistar Kyoto normotensive rats served as controls. Using immunocytochemistry, we determined glial fibrillary protein (GFAP)+ astrocytes in the CA1, CA3 and hilus of the dentate gyrus of the hippocampus, aromatase immunostaining in the hilus, and doublecortin (DCX)+ neuronal progenitors in the inner granular zone of the dentate gyrus. Brain-derived neurotrophic factor mRNA was also measured in the hippocampus by the quantitative polymerase chain reaction. In SHR, PPT had no effect on blood pressure, decreased astrogliosis, slightly increased BDNF mRNA, had no effect on the number of DCX+ progenitors, and increased aromatase staining. Treatment with DPN decreased blood pressure, decreased astrogliosis, increased BDNF mRNA and DCX+ progenitors, and did not modify aromatase staining. We hypothesise that, although both receptor types may participate in the previously reported beneficial effects of 17ß-oestradiol in SHR, receptor activation with DPN may preferentially facilitate BDNF mRNA expression and neurogenesis. The results of the present study may help in the design of ER-based neuroprotection for the encephalopathy of hypertension.
Asunto(s)
Receptor alfa de Estrógeno/agonistas , Receptor beta de Estrógeno/agonistas , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Nitrilos/administración & dosificación , Fenoles/administración & dosificación , Propionatos/administración & dosificación , Pirazoles/administración & dosificación , Animales , Aromatasa/metabolismo , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Presión Sanguínea , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Proteína Doblecortina , Receptor alfa de Estrógeno/fisiología , Receptor beta de Estrógeno/fisiología , Gliosis , Masculino , Células-Madre Neurales/efectos de los fármacos , Células-Madre Neurales/metabolismo , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Tamaño de los Órganos , Hipófisis/anatomía & histología , Hipófisis/efectos de los fármacos , ARN Mensajero/metabolismo , Ratas Endogámicas SHR , Ratas Endogámicas WKY , Testículo/anatomía & histología , Testículo/efectos de los fármacosRESUMEN
Previous work has shown a reduction of apical dendritic length and spine density in neurons from the CA1 hippocampus subfield of spontaneously hypertensive rats (SHRs). These abnormalities are prevented by treatment for 2 weeks with 17ß-estradiol. In view of the fact that diabetes and hypertension are comorbid diseases, we have now studied the effect of Streptozotocin-induced diabetes on the dendritic tree and spines of CA1 hippocampus neurons, and also compared the regulation of these parameters by 17ß-estradiol in diabetic and normoglycemic SHR. Twenty-week-old male SHR received i.v. 40-mg/kg Streptozotocin or vehicle and studied 1 month afterward. A group of normoglycemic and hyperglycemic SHR also received s.c. a single 17ß-estradiol pellet or vehicle for 2weeks. Hippocampus sections were impregnated with silver nitrate following a modified Golgi's method and the arbor of CA1 pyramidal neurons analyzed by Sholl's method. 17ß-Estradiol treatment of normoglycemic SHR reversed the reduced length of apical dendrites, the low spine density and additionally decreased blood pressure (BP). Diabetic SHR showed increased length of apical and basal dendrites but reduced spine density compared to normoglycemic SHR. Diabetes also decreased BP of SHR. Treatment with 17ß-estradiol of diabetic SHR enhanced dendritic length, increased dendritic spine density and further decreased BP. Thus, changes of cytoarchitecture of CA1 neurons due to 17ß-estradiol treatment of normoglycemic SHR persisted after diabetes induction. A decrease of BP may also contribute to the central effects of 17ß-estradiol in SHR diabetic rats.
Asunto(s)
Región CA1 Hipocampal/efectos de los fármacos , Dendritas/efectos de los fármacos , Diabetes Mellitus Experimental/tratamiento farmacológico , Estradiol/farmacología , Fármacos Neuroprotectores/farmacología , Células Piramidales/efectos de los fármacos , Animales , Presión Sanguínea/efectos de los fármacos , Región CA1 Hipocampal/patología , Región CA1 Hipocampal/fisiopatología , Dendritas/patología , Dendritas/fisiología , Diabetes Mellitus Experimental/patología , Diabetes Mellitus Experimental/fisiopatología , Hipertensión/tratamiento farmacológico , Hipertensión/patología , Hipertensión/fisiopatología , Masculino , Fotomicrografía , Células Piramidales/patología , Células Piramidales/fisiopatología , Ratas Endogámicas SHRRESUMEN
17ß-oestradiol is a powerful neuroprotective factor for the brain abnormalities of spontaneously hypertensive rats (SHR). 17α-Oestradiol, a nonfeminising isomer showing low affinity for oestrogen receptors, is also endowed with neuroprotective effects in vivo and in vitro. We therefore investigated whether treatment with 17α-oestradiol prevented pathological changes of the hippocampus and hypothalamus of SHR. We used 20-week-old male SHR with a blood pressure of approximately 170 mmHg receiving s.c. a single 800 µg pellet of 17α-oestradiol dissolved in cholesterol or vehicle only for 2 weeks Normotensive Wistar-Kyoto (WKY) rats were used as controls. 17α-Oestradiol did not modify blood pressure, serum prolactin, 17ß-oestradiol levels or the weight of the testis and pituitary of SHR. In the brain, we analysed steroid effects on hippocampus Ki67+ proliferating cells, doublecortin (DCX) positive neuroblasts, glial fibrillary acidic protein (GFAP)+ astrocyte density, aromatase immunostaining and brain-derived neurotrophic factor (BDNF) mRNA. In the hypothalamus, we determined arginine vasopressin (AVP) mRNA. Treatment of SHR with 17α-oestradiol enhanced the number of Ki67+ in the subgranular zone and DCX+ cells in the inner granule cell layer of the dentate gyrus, increased BDNF mRNA in the CA1 region and gyrus dentatus, decreased GFAP+ astrogliosis in the CA1 subfield, and decreased hypothalamic AVP mRNA. Aromatase expression was unmodified. By contrast to SHR, normotensive WKY rats were unresponsive to 17α-oestradiol. These data indicate a role for 17α-oestradiol as a protective factor for the treatment of hypertensive encephalopathy. Furthermore, 17α-oestradiol is weakly oestrogenic in the periphery and can be used in males.
Asunto(s)
Encéfalo/efectos de los fármacos , Estradiol/farmacología , Fármacos Neuroprotectores/farmacología , Animales , Arginina Vasopresina/metabolismo , Presión Sanguínea/efectos de los fármacos , Química Encefálica/efectos de los fármacos , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Proteína Doblecortina , Gliosis/patología , Masculino , Neurogénesis/efectos de los fármacos , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKYRESUMEN
In mice with experimental autoimmune encephalomyelitis (EAE) pretreatment with progesterone improves clinical signs and decreases the loss of myelin basic protein (MBP) and proteolipid protein (PLP) measured by immunohistochemistry and in situ hybridization. Presently, we analyzed if progesterone effects in the spinal cord of EAE mice involved the decreased transcription of local inflammatory mediators and the increased transcription of myelin proteins and myelin transcription factors. C57Bl/6 female mice were divided into controls, EAE and EAE receiving progesterone (100mg implant) 7 days before EAE induction. Tissues were collected on day 17 post-immunization. Real time PCR technology demonstrated that progesterone blocked the EAE-induced increase of the proinflammatory mediators tumor necrosis factor alpha (TNFα) and its receptor TNFR1, the microglial marker CD11b and toll-like receptor 4 (TLR4) mRNAs, and increased mRNA expression of PLP and MBP, the myelin transcription factors NKx2.2 and Olig1 and enhanced CC1+oligodendrocyte density respect of untreated EAE mice. Immunocytochemistry demonstrated decreased Iba1+microglial cells. Confocal microscopy demonstrated that TNFα colocalized with glial-fibrillary acidic protein+astrocytes and OX-42+microglial cells. Therefore, progesterone treatment improved the clinical signs of EAE, decreased inflammatory glial reactivity and increased myelination. Data suggest that progesterone neuroprotection involves the modulation of transcriptional events in the spinal cord of EAE mice.
Asunto(s)
Encefalomielitis Autoinmune Experimental/tratamiento farmacológico , Encefalomielitis Autoinmune Experimental/metabolismo , Mediadores de Inflamación/metabolismo , Vaina de Mielina/efectos de los fármacos , Progesterona/farmacología , Médula Espinal/metabolismo , Animales , Proteínas de Unión al Calcio/biosíntesis , Proteínas de Unión al Calcio/genética , Regulación hacia Abajo/efectos de los fármacos , Encefalomielitis Autoinmune Experimental/patología , Femenino , Proteína Homeobox Nkx-2.2 , Inmunohistoquímica , Ratones , Ratones Endogámicos C57BL , Proteínas de Microfilamentos/biosíntesis , Proteínas de Microfilamentos/genética , Microglía/metabolismo , Microscopía Confocal , Proteínas de la Mielina/biosíntesis , Vaina de Mielina/patología , Oligodendroglía/efectos de los fármacos , Oligodendroglía/metabolismo , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Médula Espinal/efectos de los fármacos , Factores de Transcripción/biosíntesis , Factores de Transcripción/genéticaRESUMEN
Besides their effects on reproduction, estrogens exert neuroprotective effects for brain diseases. Thus, estrogens ameliorate the negative aspects of aging and age-associated diseases in the nervous system, including hypertension. Within the brain, the hippocampus is sensitive to the effects of hypertension, as exemplified in a genetic model, the spontaneously hypertensive rat (SHR). In the dentate gyrus of the hippocampus, SHR present decreased neurogenesis, astrogliosis, low expression of brain derived neurotrophic factor (BDNF), decreased number of neurons in the hilus and increased basal levels of the estrogen-synthesizing enzyme aromatase, with respect to the Wistar Kyoto (WKY) normotensive strain. In the hypothalamus, SHR show increased expression of the hypertensinogenic peptide arginine vasopressin (AVP) and its V1b receptor. From the therapeutic point of view, it was highly rewarding that estradiol treatment decreased blood pressure and attenuated brain abnormalities of SHR, rendering hypertension a suitable model to test estrogen neuroprotection. When estradiol treatment was given for 2 weeks, SHR normalized their faulty brain parameters. This was shown by the enhancement of neurogenesis in the dentate gyrus, according to increased bromodeoxyuridine incorporation and doublecortin labeling, decreased reactive astrogliosis, increased BDNF mRNA and protein expression in the dentate gyrus, increased neuronal number in the hilus of the dentate gyrus and a further hyperexpression of aromatase. The presence of estradiol receptors in hippocampus and hypothalamus suggests the possibility of direct effects of estradiol on brain cells. Successful neuroprotection produced by estradiol in hypertensive rats should encourage the treatment with non-feminizing estrogens and estrogen receptor modulators for age-associated diseases.
Asunto(s)
Estradiol/metabolismo , Estradiol/uso terapéutico , Encefalopatía Hipertensiva/tratamiento farmacológico , Encefalopatía Hipertensiva/metabolismo , Fármacos Neuroprotectores/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Animales , Presión Sanguínea/efectos de los fármacos , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Encéfalo/patología , Encéfalo/fisiopatología , Proteína Doblecortina , Estradiol/farmacología , Humanos , Encefalopatía Hipertensiva/patología , Encefalopatía Hipertensiva/fisiopatología , Fármacos Neuroprotectores/farmacologíaRESUMEN
The mineralocorticoid receptor (MR) has been considered as both neuroprotective and damaging to the function of the central nervous system. MR may be also involved in central regulation of blood pressure. In the present study, we compared the expression of MR and the glucocorticoid receptor (GR) in the hippocampus and hypothalamus of 16-week-old spontaneously hypertensive rats (SHR) and normotensive control Wistar Kyoto (WKY) rats. In the hippocampus, MR expression was studied by in situ hybridization (ISH), quantitative polymerase chain reaction (PCR) and immunohistochemistry, whereas GR expression was analysed using the latter two procedures. Hypertensive animals showed an increased expression of MR mRNA in the whole hippocampus according to qPCR data and also in CA3 by ISH. Immunocytochemical staining for MR of the dorsal hippocampus, however, did not reveal differences between SHR and WKY rats. SHR showed elevated hypothalamic MR mRNA by qPCR, as well as an increased number of MR immunopositive cells in the magnocellular paraventricular region, compared to WKY rats. By contrast, expression levels of GR mRNA or protein in the hippocampus and hypothalamus of SHR were similar to those of WKY rats. Furthermore, we investigated the role of MR in the hypertensive rats by i.c.v. injection of the MR antagonist RU-2831. This compound produced a significant drop in blood pressure for SHR. In conclusion, MR expression is increased in the hippocampus and hypothalamus of SHR. We suggest that pathological MR overdrive may take responsibility for up-regulation of blood pressure and the encephalopathy of hypertension.
Asunto(s)
Hipocampo/metabolismo , Hipotálamo/metabolismo , Ratas Endogámicas SHR/metabolismo , Receptores de Mineralocorticoides/biosíntesis , Animales , Presión Sanguínea/efectos de los fármacos , Antagonistas de Receptores de Mineralocorticoides/farmacología , Ratas , Ratas Endogámicas WKY , Receptores de Glucocorticoides/biosíntesis , Espironolactona/análogos & derivados , Espironolactona/farmacologíaRESUMEN
There is high incidence of hippocampal abnormalities in spontaneously hypertensive rats (SHR), including decreased neurogenesis in the dentate gyrus, astrogliosis, low expression of brain derived neurotrophic factor and decreased neuronal density in the hilar region, respect of normotensive Wistar Kyoto rats (WKY). Estradiol treatment given for 2 weeks normalized the faulty hippocampal parameters of SHR, without having effects on WKY rats. The present work studied the potential role of local estrogen biosynthesis in the hippocampus of SHR and WKY, by measuring the expression of aromatase, the key enzyme responsible for estrogen biosynthesis and involved in neuroprotection. We used 4 month old male SHR and WKY, half of which received a single sc pellet of 12 mg estradiol benzoate and the remaining half a cholesterol implant. Hippocampi were dissected and processed for aromatase mRNA expression using real time PCR. A second batch of animals was processed for aromatase and glial fibrillary acidic protein (GFAP) immunocytochemistry. Basal level of aromatase mRNA was higher in SHR respect of WKY. Following estradiol treatment, aromatase mRNA was further increased in the SHR group only. In the hilus of the dentate gyrus of cholesterol-implanted SHR, we found aromatase immunoreactive cell processes and fibers more strongly stained respect of WKY rats. Estradiol treatment of SHR further increased the length of immunoreactive processes and fibers in the hilar region and also increased aromatase immunoreactivity in the CA1 but not the CA3 pyramidal cell region. WKY rats were spared from the estradiol effect. Double-labelling experiments showed that aromatase+ processes and fibers of the hilus of SHR-treated rats did no colocalize with GFAP+ astrocyte cell bodies or processes. In conclusion, basal and estradiol-stimulated aromatase expression was enhanced in hypertensive rat hippocampus. A combination of exogenous estrogens and those locally synthesized may better alleviate hypertensive encephalopathy.