RESUMO
Hypertension is a risk factor for neurodegenerative disorders involving inflammation and inflammatory cytokine-producing brain cells (microglia and astrocytes) in the hippocampus and medial prefrontal cortex (mPFC). Here we investigated the effect of slow-pressor angiotensin II (AngII) on gliosis in the hippocampus and mPFC of young adult (2-mo-old) male and female mice. In males, AngII induced hypertension, and this resulted in an increase in the density of the astrocyte marker glial fibrillary acidic protein (GFAP) in the subgranular hilus and a decrease in the density of the microglial marker ionized calcium binding adapter molecule (Iba-1) in the CA1 region. Females infused with AngII did not show hypertension but, significantly, showed alterations in hippocampal glial activation. Compared with vehicle, AngII-infused female mice had an increased density of Iba-1 in the dentate gyrus and CA2/3a region. Like males, females infused with AngII exhibited decreased Iba-1 in the CA1 region. Neither male nor female mice showed differences in GFAP or Iba-1 in the mPFC following AngII infusion. These results demonstrate that the hippocampus is particularly vulnerable to AngII in young adulthood. Differences in gonadal hormones or the sensitivity to AngII hypertension may account for divergences in GFAP and Iba-1 in males and females.
Assuntos
Angiotensina II , Hipertensão , Angiotensina II/metabolismo , Angiotensina II/farmacologia , Animais , Astrócitos/metabolismo , Biomarcadores/metabolismo , Cálcio/metabolismo , Proteínas de Ligação ao Cálcio , Citocinas/metabolismo , Feminino , Proteína Glial Fibrilar Ácida/metabolismo , Hipocampo/metabolismo , Masculino , CamundongosRESUMO
There are significant neurogenic and inflammatory influences on blood pressure, yet the role played by each of these processes in the development of hypertension is unclear. Tumor necrosis factor α (TNFα) has emerged as a critical modulator of blood pressure and neural plasticity; however, the mechanism by which TNFα signaling contributes to the development of hypertension is uncertain. We present evidence that following angiotensin II (AngII) infusion the TNFα type 1 receptor (TNFR1) plays a key role in heightened glutamate signaling in the hypothalamic paraventricular nucleus (PVN), a key central coordinator of blood pressure control. Fourteen day administration of a slow-pressor dose of AngII in male mice was associated with transcriptional and post-transcriptional (increased plasma membrane affiliation) regulation of TNFR1 in the PVN. Further, TNFR1 was shown to be critical for elevated NMDA-mediated excitatory currents in sympathoexcitatory PVN neurons following AngII infusion. Finally, silencing PVN TNFR1 prevented the increase in systolic blood pressure induced by AngII. These findings indicate that TNFR1 modulates a cellular pathway involving an increase in NMDA-mediated currents in the PVN following AngII infusion, suggesting a mechanism whereby TNFR1 activation contributes to hypertension via heightened hypothalamic glutamate-dependent signaling.SIGNIFICANCE STATEMENT Inflammation is critical for the emergence of hypertension, yet the mechanisms by which inflammatory mediators contribute to this dysfunction are not clearly defined. We show that tumor necrosis factor α receptor 1 (TNFR1) in the paraventricular hypothalamic nucleus (PVN), a critical neuroregulator of cardiovascular function, plays an important role in the development of hypertension in mice. In the PVN, TNFR1 expression and plasma membrane localization are upregulated during hypertension induced by angiotensin II (AngII). Further, TNFR1 activation was essential for NMDA signaling and the heightening NMDA currents during hypertension. Finally, TNFR1 silencing in the PVN inhibits elevated blood pressure induced by AngII. These results point to a critical role for hypothalamic TNFR1 signaling in hypertension.
Assuntos
Angiotensina II/toxicidade , Ácido Glutâmico/metabolismo , Hipertensão/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Transdução de Sinais/fisiologia , Animais , Hipertensão/induzido quimicamente , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , N-Metilaspartato/metabolismo , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacosRESUMO
Molecular chaperones and co-chaperones, which are part of the protein quality control machinery, have been shown to regulate distinct aspects of Alzheimer's Disease (AD) pathology in multiple ways. Notably, the co-chaperone STI1, which presents increased levels in AD, can protect mammalian neurons from amyloid-ß toxicity in vitro and reduced STI1 levels worsen Aß toxicity in C. elegans. However, whether increased STI1 levels can protect neurons in vivo remains unknown. We determined that overexpression of STI1 and/or Hsp90 protected C. elegans expressing Aß(3-42) against Aß-mediated paralysis. Mammalian neurons were also protected by elevated levels of endogenous STI1 in vitro, and this effect was mainly due to extracellular STI1. Surprisingly, in the 5xFAD mouse model of AD, by overexpressing STI1, we find increased amyloid burden, which amplifies neurotoxicity and worsens spatial memory deficits in these mutants. Increased levels of STI1 disturbed the expression of Aß-regulating enzymes (BACE1 and MMP-2), suggesting potential mechanisms by which amyloid burden is increased in mice. Notably, we observed that STI1 accumulates in dense-core AD plaques in both 5xFAD mice and human brain tissue. Our findings suggest that elevated levels of STI1 contribute to Aß accumulation, and that STI1 is deposited in AD plaques in mice and humans. We conclude that despite the protective effects of STI1 in C. elegans and in mammalian cultured neurons, in vivo, the predominant effect of elevated STI1 is deleterious in AD.
Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Modelos Animais de Doenças , Proteínas de Choque Térmico/metabolismo , Placa Amiloide/metabolismo , Doença de Alzheimer/metabolismo , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/metabolismo , Humanos , Camundongos , Proteínas Nucleares/metabolismoRESUMO
Obstructive sleep apnea (OSA), a chronic sleep disorder characterized by repetitive reduction or cessation of airflow during sleep, is widely prevalent and is associated with adverse neurocognitive sequelae including increased risk of Alzheimer's disease (AD). In humans, OSA is more common in elderly males. OSA is characterized by sleep fragmentation and chronic intermittent hypoxia (CIH), and recent epidemiological studies point to CIH as the best predictor of neurocognitive sequelae associated with OSA. The sex- and age- specific effects of OSA-associated CIH on specific cell populations such as γ-aminobutyric acid (GABA)-ergic neurons in the hippocampus and the medial prefrontal cortex (mPFC), regions important for cognitive function, remain largely unknown. The present study examined the effect of 35 days of either moderate (10% oxygen) or severe (5% oxygen) CIH on GABAergic neurons in the mPFC and hippocampus of young and aged male and female mice as well as post-accelerated ovarian failure (AOF) female mice. In the mPFC and hippocampus, the number of GABA-labeled neurons increased in aged and young severe CIH males compared to controls but not in young moderate CIH males. This change was not representative of the individual GABAergic cell subpopulations, as the number of parvalbumin-labeled neurons decreased while the number of somatostatin-labeled neurons increased in the hippocampus of severe CIH young males only. In all female groups, the number of GABA-labeled cells was not different between CIH and controls. However, in the mPFC, CIH increased the number of parvalbumin-labeled neurons in young females and the number of somatostatin-labeled cells in AOF females but decreased the number of somatostatin-labeled cells in aged females. In the hippocampus, CIH decreased the number of somatostatin-labeled neurons in young females. CIH decreased the density of vesicular GABA transporter in the mPFC of AOF females only. These findings suggest sex-specific changes in GABAergic neurons in the hippocampus and mPFC with males showing an increase of this cell population as compared to their female counterparts following CIH. Age at exposure and severity of CIH also differentially affect the GABAergic cell population in mice.
Assuntos
Neurônios GABAérgicos/patologia , Hipocampo/patologia , Hipóxia Encefálica/patologia , Córtex Pré-Frontal/patologia , Fatores Etários , Animais , Contagem de Células , Feminino , Hipocampo/metabolismo , Hipóxia Encefálica/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Córtex Pré-Frontal/metabolismo , Caracteres SexuaisRESUMO
Sex and ovarian function contribute to hypertension susceptibility, however, the mechanisms are not well understood. Prior studies show that estrogens and neurogenic factors, including hypothalamic glutamatergic NMDA receptor plasticity, play significant roles in rodent hypertension. Here, we investigated the role of sex and ovarian failure on AMPA receptor plasticity in estrogen-sensitive paraventricular nucleus (PVN) neurons in naïve and angiotensin II (AngII) infused male and female mice and female mice at early and late stages of accelerated ovarian failure (AOF). High-resolution electron microscopy was used to assess the subcellular distribution of AMPA GluA1 in age-matched male and female estrogen receptor beta (ERß) enhanced green fluorescent protein (EGFP) reporter mice as well as female ERß-EGFP mice treated with 4-vinylcyclohexene diepoxide. In the absence of AngII, female mice at a late stage of AOF displayed higher levels of GluA1 on the plasma membrane, indicative of functional protein, in ERß-expressing PVN dendrites when compared to male, naïve female and early stage AOF mice. Following slow-pressor AngII infusion, males, as well as early and late stage AOF females had elevated blood pressure. Significantly, only late stage-AOF female mice infused with AngII had an increase in GluA1 near the plasma membrane in dendrites of ERß-expressing PVN neurons. In contrast, prior studies reported that plasmalemmal NMDA GluN1 increased in ERß-expressing PVN dendrites in males and early, but not late stage AOF females. Together, these findings reveal that early and late stage AOF female mice display unique molecular signatures of long-lasting synaptic strength prior to, and following hypertension.
Assuntos
Membrana Celular/metabolismo , Receptor beta de Estrogênio/metabolismo , Hipertensão/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Pós-Menopausa/metabolismo , Receptores de AMPA/metabolismo , Angiotensina II/efeitos adversos , Animais , Cicloexenos/efeitos adversos , Feminino , Hipertensão/induzido quimicamente , Masculino , Camundongos , Neurônios/metabolismo , Insuficiência Ovariana Primária/induzido quimicamente , Insuficiência Ovariana Primária/metabolismo , Compostos de Vinila/efeitos adversosRESUMO
The accumulation of misfolded proteins in the human brain is one of the critical features of many neurodegenerative diseases, including Alzheimer's disease (AD). Assembles of beta-amyloid (Aß) peptide-either soluble (oligomers) or insoluble (plaques) and of tau protein, which form neurofibrillary tangles, are the major hallmarks of AD. Chaperones and co-chaperones regulate protein folding and client maturation, but they also target misfolded or aggregated proteins for refolding or for degradation, mostly by the proteasome. They form an important line of defense against misfolded proteins and are part of the cellular quality control system. The heat shock protein (Hsp) family, particularly Hsp70 and Hsp90, plays a major part in this process and it is well-known to regulate protein misfolding in a variety of diseases, including tau levels and toxicity in AD. However, the role of Hsp90 in regulating protein misfolding is not yet fully understood. For example, knockdown of Hsp90 and its co-chaperones in a Caenorhabditis elegans model of Aß misfolding leads to increased toxicity. On the other hand, the use of Hsp90 inhibitors in AD mouse models reduces Aß toxicity, and normalizes synaptic function. Stress-inducible phosphoprotein 1 (STI1), an intracellular co-chaperone, mediates the transfer of clients from Hsp70 to Hsp90. Importantly, STI1 has been shown to regulate aggregation of amyloid-like proteins in yeast. In addition to its intracellular function, STI1 can be secreted by diverse cell types, including astrocytes and microglia and function as a neurotrophic ligand by triggering signaling via the cellular prion protein (PrPC). Extracellular STI1 can prevent Aß toxic signaling by (i) interfering with Aß binding to PrPC and (ii) triggering pro-survival signaling cascades. Interestingly, decreased levels of STI1 in C. elegans can also increase toxicity in an amyloid model. In this review, we will discuss the role of intracellular and extracellular STI1 and the Hsp70/Hsp90 chaperone network in mechanisms underlying protein misfolding in neurodegenerative diseases, with particular focus on AD.
RESUMO
Hypertension in male and aging female rodents is associated with glutamate-dependent plasticity in the hypothalamus, but existing models have failed to capture distinct transitional menopausal phases that could have a significant impact on the synaptic plasticity and emergent hypertension. In rodents, accelerated ovarian failure (AOF) induced by systemic injection of 4-vinylcyclohexane diepoxide mimics the estrogen fluctuations seen in human menopause including the perimenopause transition (peri-AOF) and postmenopause (post-AOF). Thus, we used the mouse AOF model to determine the impact of slow-pressor angiotensin II (AngII) administration on blood pressure and on the subcellular distribution of obligatory N-methyl-D-aspartate (NMDA) receptor GluN1 subunits in the paraventricular hypothalamic nucleus (PVN), a key estrogen-responsive cardiovascular regulatory area. Estrogen-sensitive neuronal profiles were identified in mice expressing enhanced green fluorescent protein under the promoter for estrogen receptor (ER) ß, a major ER in the PVN. Slow-pressor AngII increased arterial blood pressure in mice at peri- and post-AOF time points. In control oil-injected (nonhypertensive) mice, AngII decreased the total number of GluN1 in ERß-containing PVN dendrites. In contrast, AngII resulted in a reapportionment of GluN1 from the cytoplasm to the plasma membrane of ERß-containing PVN dendrites in peri-AOF mice. Moreover, in post-AOF mice, AngII increased total GluN1, dendritic size and radical production in ERß-containing neurons. These results indicate that unique patterns of hypothalamic glutamate receptor plasticity and dendritic structure accompany the elevated blood pressure in peri- and post-AOF time points. Our findings suggest the possibility that distinct neurobiological processes are associated with the increased blood pressure during perimenopausal and postmenopausal periods.
Assuntos
Hipertensão , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Doenças Ovarianas/etiologia , Núcleo Hipotalâmico Paraventricular/patologia , Receptores de Estrogênio/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Angiotensina II/toxicidade , Animais , Pressão Sanguínea/efeitos dos fármacos , Cicloexenos/toxicidade , Modelos Animais de Doenças , Ciclo Estral/efeitos dos fármacos , Ciclo Estral/genética , Feminino , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Hipertensão/induzido quimicamente , Hipertensão/complicações , Hipertensão/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia Imunoeletrônica , Neurônios/ultraestrutura , Núcleo Hipotalâmico Paraventricular/metabolismo , Núcleo Hipotalâmico Paraventricular/ultraestrutura , Espécies Reativas de Oxigênio/metabolismo , Receptores de Estrogênio/genética , Compostos de Vinila/toxicidadeRESUMO
At younger ages, women have a lower risk for hypertension than men, but this sexual dimorphism declines with the onset of menopause. These differences are paralleled in rodents following "slow-pressor" angiotensin II (AngII) administration: young male and aged female mice, but not young females, develop hypertension. There is also an established sexual dimorphism both in the cardiovascular response to the neurohypophyseal hormone arginine vasopressin (AVP) and in the expression of oxidative stress. We examined the relationship between AngII-mediated hypertension and the cellular distribution of the superoxide generating NADPH oxidase (NOX) in AVP-expressing hypothalamic paraventricular nucleus (PVN) neurons in "menopausal" female mice. Dual-labeling immunoelectron microscopy was used to determine whether the subcellular distribution of the organizer/adapter NOX p47(phox) subunit is altered in PVN dendrites following AngII administered (14 days) during the "postmenopausal" stage of accelerated ovarian failure (AOF) in young female mice treated with 4-vinylcyclohexene diepoxide. Slow-pressor AngII elevated blood pressure in AOF females and induced a significant increase in near plasmalemmal p47(phox) and a decrease in cytoplasmic p47(phox) in PVN AVP dendrites. These changes are the opposite of those observed in AngII-induced hypertensive male mice (Coleman et al. [2013] J. Neurosci. 33:4308-4316) and may be ascribed in part to baseline differences between young females and males in the near plasmalemmal p47(phox) on AVP dendrites seen in the present study. These findings highlight fundamental differences in the neural substrates of oxidative stress in the PVN associated with AngII hypertension in postmenopausal females compared with males. J. Comp. Neurol. 524:2251-2265, 2016. © 2015 Wiley Periodicals, Inc.
Assuntos
Hipertensão/metabolismo , NADPH Oxidases/metabolismo , Núcleo Hipotalâmico Paraventricular/enzimologia , Pós-Menopausa/metabolismo , Caracteres Sexuais , Angiotensina II/toxicidade , Animais , Modelos Animais de Doenças , Feminino , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Imunoeletrônica , Neurônios/enzimologiaRESUMO
Reninangiotensin system overactivity, upregulation of postsynaptic NMDA receptor function, and increased reactive oxygen species (ROS) production in the hypothalamic paraventricular nucleus (PVN) are hallmarks of angiotensin II (AngII)-induced hypertension, which is far more common in young males than in young females. We hypothesize that the sex differences in hypertension are related to differential AngII-induced changes in postsynaptic trafficking of the essential NMDA receptor GluN1 subunit and ROS production in PVN cells expressing angiotensin Type 1a receptor (AT1aR). We tested this hypothesis using slow-pressor (14-day) infusion of AngII (600 ng/kg/min) in mice, which elicits hypertension in males but not in young females. Two-month-old male and female transgenic mice expressing enhanced green fluorescent protein (EGFP) in AT1aR-containing cells were used. In males, but not in females, AngII increased blood pressure and ROS production in AT1aREGFP PVN cells at baseline and following NMDA treatment. Electron microscopy showed that AngII increased cytoplasmic and total GluN1silver-intensified immunogold (SIG) densities and induced a trend toward an increase in near plasmalemmal GluN1SIG density in AT1aREGFP dendrites of males and females. Moreover, AngII decreased dendritic area and diameter in males, but increased dendritic area of small (<1 µm) dendrites and decreased diameter of large (>1 µm) dendrites in females. Fluorescence microscopy revealed that AT1aR and estrogen receptor ß do not colocalize, suggesting that if estrogen is involved, its effect is indirect. These data suggest that the sexual dimorphism in AngII-induced hypertension is associated with sex differences in ROS production in AT1aR-containing PVN cells but not with postsynaptic NMDA receptor trafficking.
Assuntos
Angiotensina II/farmacologia , Dendritos/metabolismo , Hipotálamo/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Receptor Tipo 1 de Angiotensina/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Pressão Sanguínea , Dendritos/ultraestrutura , Receptor beta de Estrogênio/metabolismo , Feminino , Hipotálamo/citologia , Hipotálamo/efeitos dos fármacos , Masculino , Camundongos , Transporte Proteico , Receptor Tipo 1 de Angiotensina/genética , Sistema Renina-Angiotensina , Fatores SexuaisRESUMO
The incidence of hypertension increases after menopause. Similar to humans, "slow-pressor" doses of angiotensin II (AngII) increase blood pressure in young males, but not in young female mice. However, AngII increases blood pressure in aged female mice, paralleling reproductive hormonal changes. These changes could influence receptor trafficking in central cardiovascular circuits and contribute to hypertension. Increased postsynaptic N-methyl-D-aspartate (NMDA) receptor activity in the hypothalamic paraventricular nucleus (PVN) is crucial for the sympathoexcitation driving AngII hypertension. Estrogen receptors ß (ERßs) are present in PVN neurons. We tested the hypothesis that changes in ovarian hormones with age promote susceptibility to AngII hypertension, and influence NMDA receptor NR1 subunit trafficking in ERß-containing PVN neurons. Transgenic mice expressing enhanced green fluorescent protein (EGFP) in ERß-containing cells were implanted with osmotic minipumps delivering AngII (600 ng/kg/min) or saline for 2 weeks. AngII increased blood pressure in 2-month-old males and 18-month-old females, but not in 2-month-old females. By electron microscopy, NR1-silver-intensified immunogold (SIG) was mainly in ERß-EGFP dendrites. At baseline, NR1-SIG density was greater in 2-month-old females than in 2-month-old males or 18-month-old females. After AngII infusion, NR1-SIG density was decreased in 2-month-old females, but increased in 2-month-old males and 18-month-old females. These findings suggest that, in young female mice, NR1 density is decreased in ERß-PVN dendrites thus reducing NMDA receptor activity and preventing hypertension. Conversely, in young males and aged females, NR1 density is upregulated in ERß-PVN dendrites and ultimately leads to the neurohumoral dysfunction driving hypertension.
Assuntos
Envelhecimento/fisiologia , Angiotensina II/administração & dosagem , Dendritos/metabolismo , Receptor beta de Estrogênio/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Núcleo Hipotalâmico Paraventricular/citologia , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Pressão Sanguínea/efeitos dos fármacos , Receptor beta de Estrogênio/genética , Ciclo Estral/metabolismo , Feminino , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Neurônios/ultraestrutura , Fatores Sexuais , Estilbamidinas/metabolismo , Fatores de TempoRESUMO
Adaptive changes in glutamatergic signaling within the hypothalamic paraventricular nucleus (PVN) may play a role in the neurohumoral dysfunction underlying the hypertension induced by "slow-pressor" ANG II infusion. We hypothesized that these adaptive changes alter production of gp91phox NADPH oxidase (NOX)-derived reactive oxygen species (ROS) or nitric oxide (NO), resulting in enhanced glutamatergic signaling in the PVN. Electron microscopic immunolabeling showed colocalization of NOX2 and N-methyl-D-aspartate receptor (NMDAR) NR1 subunits in PVN dendrites, an effect enhanced (+48%, P < 0.05 vs. saline) in mice receiving ANG II (600 ng·kg⻹·min⻹ sc). Isolated PVN cells or spinally projecting PVN neurons from ANG II-infused mice had increased levels of ROS at baseline (+40 ± 5% and +57.6 ± 7.7%, P < 0.01 vs. saline) and after NMDA (+24 ± 7% and +17 ± 5.5%, P < 0.01 and P < 0.05 vs. saline). In contrast, ANG II infusion suppressed NO production in PVN cells at baseline (-29.1 ± 5.2%, P < 0.05 vs. saline) and after NMDA (-18.9 ± 2%, P < 0.01 vs. saline), an effect counteracted by NOX inhibition. In whole cell recording of unlabeled and spinally labeled PVN neurons in slices, NMDA induced a larger inward current in ANG II than in saline groups (+79 ± 24% and +82.9 ± 6.6%, P < 0.01 vs. saline), which was reversed by the ROS scavenger MnTBAP and the NO donor S-nitroso-N-acetylpenicillamine (P > 0.05 vs. control). These findings suggest that slow-pressor ANG II increases the association of NR1 with NOX2 in dendrites of PVN neurons, resulting in enhanced NOX-derived ROS and reduced NO during glutamatergic activity. The resulting enhancement of NMDAR activity may contribute to the neurohumoral dysfunction underlying the development of slow-pressor ANG II hypertension.
Assuntos
Angiotensina II/efeitos adversos , Hipertensão/induzido quimicamente , Hipertensão/metabolismo , Glicoproteínas de Membrana/metabolismo , N-Metilaspartato/metabolismo , NADPH Oxidases/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Superóxidos/metabolismo , Angiotensina II/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Cálcio/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Eletrônica de Transmissão , Modelos Animais , NADPH Oxidase 2 , Neurônios/citologia , Neurônios/metabolismo , Neurônios/ultraestrutura , Óxido Nítrico/metabolismo , Núcleo Hipotalâmico Paraventricular/citologia , Núcleo Hipotalâmico Paraventricular/ultraestrutura , Técnicas de Patch-Clamp , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologiaRESUMO
NADPH oxidase-generated reactive oxygen species (ROS) are highly implicated in the development of angiotensin II (AngII)-dependent hypertension mediated in part through the hypothalamic paraventricular nucleus (PVN). This region contains vasopressin and non-vasopressin neurons that are responsive to cardiovascular dysregulation, but it is not known whether ROS is generated by one or both cell types in response to "slow-pressor" infusion of AngII. We addressed this question using ROS imaging and electron microscopic dual labeling for vasopressin and p47(phox), a cytoplasmic NADPH oxidase subunit requiring mobilization to membranes for the initiation of ROS production. C57BL/6 mice or vasopressin-enhanced green fluorescent protein (VP-eGFP) mice were infused systemically with saline or AngII (600 ng · kg(-1) · min(-1), s.c.) for 2 weeks, during which they slowly developed hypertension. Ultrastructural analysis of the PVN demonstrated p47(phox) immunolabeling in many glial and neuronal profiles, most of which were postsynaptic dendrites. Compared with saline, AngII recipient mice had a significant increase in p47(phox) immunolabeling on endomembranes just beneath the plasmalemmal surface (+42.1 ± 11.3%; p < 0.05) in non-vasopressin dendrites. In contrast, AngII infusion decreased p47(phox) immunolabeling on the plasma membrane (-35.5 ± 16.5%; p < 0.05) in vasopressin dendrites. Isolated non-VP-eGFP neurons from the PVN of AngII-infused mice also showed an increase in baseline ROS production not seen in VP-eGFP neurons. Our results suggest that chronic low-dose AngII may offset the homeostatic control of blood pressure by differentially affecting membrane assembly of NADPH oxidase and ROS production in vasopressin and non-vasopressin neurons located within the PVN.
Assuntos
Hipertensão/patologia , NADPH Oxidases/metabolismo , Neurônios/metabolismo , Núcleo Hipotalâmico Paraventricular/patologia , Espécies Reativas de Oxigênio/metabolismo , Angiotensina II/administração & dosagem , Angiotensina II/efeitos adversos , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Dendritos/metabolismo , Dendritos/ultraestrutura , Esquema de Medicação , Sistemas de Liberação de Medicamentos , Agonistas de Aminoácidos Excitatórios/farmacologia , Proteínas de Fluorescência Verde/genética , Células HEK293 , Humanos , Hipertensão/induzido quimicamente , Técnicas In Vitro , Membranas Intracelulares/metabolismo , Membranas Intracelulares/ultraestrutura , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia Imunoeletrônica , N-Metilaspartato/farmacologia , Neuroglia/metabolismo , Neuroglia/ultraestrutura , Neurônios/efeitos dos fármacos , Neurônios/ultraestrutura , Transporte Proteico/efeitos dos fármacos , Transfecção , Vasoconstritores/administração & dosagem , Vasoconstritores/efeitos adversos , Vasopressinas/genética , Vasopressinas/metabolismoRESUMO
UNLABELLED: Hypertension-associated hypoalgesia is widely recognized in acute pain conditions. In chronic pain states, however, the relationship between blood pressure and pain sensitivity is still ill-defined, with different authors reporting negative, positive, or even no relationship at all. This work addresses this issue, using complete Freund's adjuvant (CFA)-induced monoarthritis in different models of hypertension: Spontaneous (spontaneously hypertensive rats, SHR), induced by infusion of angiotensin II (ANG) or 1,3-dipropyl-8-sulfophenylxanthine (DPSPX, an adenosine receptors' antagonist), and renal artery ligation (RAL). Nociceptive responses associated with monoarthritis were evaluated by different behavioral tests (von Frey, ankle-bend and CatWalk) and by quantification of Fos expression at the dorsal horn upon noxious stimulation. In all hypertension models, higher von Frey thresholds and lower Fos expression were detected in hypertensive rats with chronic inflammatory pain, as compared to normotensive monoarthritic rats. In SHR and DPSPX, but not ANG or RAL models, hypertensive animals displayed lower inflammation than normotensives. Ankle-bend and CatWalk results indicated lower pain sensitivity in hypertensive rats only in SHR and DPSPX models. The present study shows the importance of using multiple models of hypertension, and evaluating pain responses by various methods, to better understand the complexity of the interactions between pain and cardiovascular regulatory systems. PERSPECTIVE: This study used different models of hypertension to investigate whether chronic pain alters the normal integration of cardiovascular and pain regulatory systems. A complete understanding of the mechanisms underlying the complex interactions between these systems may disclose future therapeutic approaches to treat hypertension/chronic pain comorbidity states.
Assuntos
Artrite/fisiopatologia , Pressão Sanguínea/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Hipertensão/fisiopatologia , Dor Intratável/fisiopatologia , Animais , Artrite/complicações , Modelos Animais de Doenças , Hipertensão/etiologia , Masculino , Dor Intratável/complicações , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY , Ratos Sprague-Dawley , Ratos WistarRESUMO
The caudal ventrolateral medulla (CVLM) is a key component of the supraspinal pain modulatory system. Pain modulation from the CVLM is partially relayed by spinally projecting noradrenergic neurons of the pontine A(5) cell group, which leave collateral fibres at the CVLM. The injection of angiotensin II (Ang II) into the CVLM was recently shown to induce hyperalgesia mediated by angiotensin type 1 (AT(1)) receptors, expressed by CVLM neurons that do not project to the spinal cord. The present study evaluates the effects of lesioning the noradrenergic pontine A(5) cell group by the retrograde transport of the selective toxin anti-dopamine beta-hydroxylase-saporin (anti-DBH-SAP) from the CVLM in pain behavioural responses elicited by Ang II injection into the CVLM. The injection of anti-DBH-SAP induced neurodegeneration, identified by the marker Fluoro-Jade B, restricted to the A(5) noradrenergic cell group. These results were confirmed by the decrease in the number of noradrenergic neurons only in the A(5) group. Pain behavioural evaluation using the formalin test showed that Ang II injection into the CVLM induced hyperalgesia, which was partially prevented by lesion of the A(5) noradrenergic cell group with anti-DBH-SAP. Immunostaining of AT(1) receptors in CVLM neurons retrogradely labelled from the A(5) noradrenergic cell group showed that CVLM neurons that project to the A(5) express AT(1) receptors, indicating that Ang II can modulate directly the CVLM-A(5) connection. The results show that Ang II-induced hyperalgesia elicited from the CVLM is mediated by an indirect pathway relayed at the pontine noradrenergic A(5) group.
Assuntos
Angiotensina II/farmacologia , Fármacos do Sistema Nervoso Central/farmacologia , Hiperalgesia/induzido quimicamente , Bulbo/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Ponte/efeitos dos fármacos , Animais , Hiperalgesia/fisiopatologia , Masculino , Bulbo/fisiopatologia , Vias Neurais/efeitos dos fármacos , Vias Neurais/fisiopatologia , Neurônios/fisiologia , Norepinefrina/metabolismo , Dor/induzido quimicamente , Dor/fisiopatologia , Ponte/fisiopatologia , Ratos , Ratos Wistar , Receptor Tipo 1 de Angiotensina/metabolismoRESUMO
Treatment of Wistar rats for 7 days with 1,3-dipropyl-8-sulfophenylxanthine (DPSPX), an antagonist of adenosine receptors, induces long-lasting hypertension associated with marked changes in vascular structure and reactivity and renin-angiotensin system activation. This study aimed at evaluating the role of oxidative stress in the development of DPSPX-induced hypertension and also at identifying the relative contribution of superoxide radical (O2.-) vs hydrogen peroxide (H2O2). Vascular and systemic prooxidant/antioxidant status was evaluated in sham (saline, i.p., 7 days) and DPSPX (90 microg/kg/h, i.p., 7 days)-treated rats. Systolic blood pressure was determined by invasive and non-invasive methods. The activity of vascular NADPH oxidase, superoxide dismutase (SOD), catalase and glutathione peroxidase was assayed by fluorometric/spectrophotometric methods. H2O2 levels were measured using an Amplex Red Hydrogen Peroxide kit. Plasma thiobarbituric acid reactive substances and plasma antioxidant capacity were also measured. In addition we tested the effects of antioxidants or inhibitors of reactive oxygen species generation on blood pressure, vascular hyperplasia and oxidative stress parameters. DPSPX-hypertensive rats showed increased activity of vascular NADPH oxidase, SOD, catalase and glutathione peroxidase, as well as increased H2O2 generation. DPSPX-hypertensive rats also had increased plasma lipid peroxidation and decreased plasma antioxidant capacity. Treatment with apocynin (1.5 mmol/l, per os, 14 days), or with polyethylene glycol (PEG)-catalase (10,000 U/kg/day, i.p., 8 days), prevented the DPSPX-induced effects on blood pressure, vascular structure and H2O2 levels. Tempol (3 mmol/l, per os, 14 days) failed to inhibit these changes, unless PEG-catalase was co-administered. It is concluded that O2.- generation with subsequent formation of H2O2 plays a major role in the development of DPSPX-induced hypertension.