RESUMO
The carotid body (CB) plays an important role in the alteration of cardiorespiratory activity in chronic intermittent hypoxia (IH) associated with sleep-disordered breathing, which may be mediated by local expression of the renin-angiotensin system (RAS). We hypothesized a pathogenic role for IH-induced RAS expression in the CB. The CB expression of RAS components was examined in rats exposed to IH resembling a severe sleep-apnoeic condition for 7 days. In situ hybridization showed an elevated expression of angiotensinogen in the CB glomus cells in the hypoxic group when compared with the normoxic control group. Immunohistochemical studies and Western blot analysis revealed increases in the protein level of both angiotensinogen and angiotensin II type 1 (AT1) receptors in the hypoxic group, which were localized to the glomic clusters containing tyrosine hydroxylase. RT-PCR studies confirmed that levels of the mRNA expression of angiotensinogen, angiotensin-converting enzyme, AT1a and AT2 receptors were significantly increased in the CBs of the hypoxic rats. Functionally, the [Ca(2+)]i response to exogenous angiotensin II was enhanced in fura-2-loaded glomus cells dissociated from hypoxic rats when compared with those of the normoxic control animals. Pretreatment with losartan, but not PD123319, abolished the angiotensin II-induced [Ca(2+)]i response, suggesting an involvement of AT1 receptors. Moreover, daily treatment of the IH group of rats with losartan attenuated the levels of oxidative stress, gp91(phox) expression and macrophage infiltration in the CB. Collectively, the upregulated local RAS expression could play a pathogenic role in the augmented CB activity and local inflammation via AT1 receptor activation during IH conditions in patients with sleep-disordered breathing.
Assuntos
Corpo Carotídeo/metabolismo , Hipóxia/genética , Hipóxia/metabolismo , Sistema Renina-Angiotensina/genética , Regulação para Cima/genética , Angiotensina II/genética , Angiotensina II/metabolismo , Angiotensinogênio/genética , Angiotensinogênio/metabolismo , Animais , Cálcio/metabolismo , Fura-2/metabolismo , Masculino , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , NADPH Oxidase 2 , NADPH Oxidases/genética , NADPH Oxidases/metabolismo , Estresse Oxidativo/genética , Peptidil Dipeptidase A/genética , Peptidil Dipeptidase A/metabolismo , Ratos , Ratos Sprague-Dawley , Receptor Tipo 1 de Angiotensina/genética , Receptor Tipo 1 de Angiotensina/metabolismo , Síndromes da Apneia do Sono/genética , Síndromes da Apneia do Sono/metabolismo , Tirosina 3-Mono-Oxigenase/genética , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Maladaptive changes in the carotid body (CB) induced by chronic intermittent hypoxia (IH) account for the pathogenesis of cardiovascular morbidity in patients with sleep-disordered breathing. We postulated that the proinflammatory cytokines, namely interleukin (IL)-1ß, IL-6 and tumor necrosis factor (TNF)-α, and cytokine receptors (IL-1r1, gp130 and TNFr1) locally expressed in the rat CB play a pathophysiological role in IH-induced CB inflammation. Results showed increased levels of oxidative stress (serum 8-isoprostane and nitrotyrosine in the CB) in rats with 7-day IH treatment resembling recurrent apneic conditions when compared with the normoxic control. Local inflammation shown by the amount of ED1-containing cells (macrophage infiltration) and the gene transcripts of NADPH oxidase subunits (gp91(phox) and p22(phox)) and chemokines (MCP-1, CCR2, MIP-1α, MIP-1ß and ICAM-1) in the CB were significantly more in the hypoxic group than in the control. In addition, the cytokines and receptors were expressed in the lobules of chemosensitive glomus cells containing tyrosine hydroxylase and the levels of expressions were significantly increased in the hypoxic group. Exogenous cytokines elevated the intracellular calcium ([Ca(2+)](i)) response to acute hypoxia in the dissociated glomus cells. The effect of cytokines on the [Ca(2+)](i) response was significantly greater in the hypoxic than in the normoxic group. Moreover, daily treatment of IH rats with anti-inflammatory drugs (dexamethasone or ibuprofen) attenuated the levels of oxidative stress, gp91(phox) expression and macrophage infiltration in the CB. Collectively, these results suggest that the upregulated expression of proinflammatory cytokine pathways could mediate the local inflammation and functional alteration of the CB under chronic IH conditions.
Assuntos
Corpo Carotídeo/imunologia , Citocinas/imunologia , Hipóxia/imunologia , Transdução de Sinais/imunologia , Síndromes da Apneia do Sono/imunologia , Vasculite/imunologia , Animais , Anti-Inflamatórios/farmacologia , Anti-Inflamatórios não Esteroides/farmacologia , Cálcio/metabolismo , Artéria Carótida Interna/imunologia , Artéria Carótida Interna/metabolismo , Corpo Carotídeo/metabolismo , Doença Crônica , Citocinas/genética , Citocinas/metabolismo , Dexametasona/farmacologia , Modelos Animais de Doenças , Expressão Gênica/efeitos dos fármacos , Expressão Gênica/imunologia , Hipóxia/tratamento farmacológico , Hipóxia/metabolismo , Ibuprofeno/farmacologia , Masculino , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/imunologia , Ratos , Ratos Sprague-Dawley , Receptores de Citocinas/genética , Receptores de Citocinas/imunologia , Receptores de Citocinas/metabolismo , Transdução de Sinais/efeitos dos fármacos , Síndromes da Apneia do Sono/metabolismo , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/imunologia , Vasculite/tratamento farmacológico , Vasculite/metabolismoRESUMO
The structure and function of the carotid body are greatly altered during chronic hypoxia. Recent studies showed the expression of interleukin (IL)-1 receptor and IL-6 receptor in the carotid body, suggesting a role of proinflammatory cytokines in the chemoreceptor function. The present study aimed to examine the hypothesis that the expression of pro-inflammatory cytokines, namely IL-1beta, IL-6 and tumor necrosis factor (TNF)alpha, plays a role in the rat carotid body in chronic hypoxia. Levels of the mRNA expression of the cytokines and their receptors IL-1r1, gp130 and TNFr1, were significantly increased in the carotid body of hypoxic rats when compared with the normoxic control. Immunohistochemistry showed that the expressions of cytokines and receptors were localized in the lobules of chemosensitive glomus cells containing tyrosine hydroxylase. There were significantly more positive-staining cells in the hypoxic groups with treatment for 3, 7 and 28 days than those of the normoxic controls. Application of exogenous cytokines (0.1 nM) elevated intracellular calcium ([Ca(2+)](i)) responses to acute hypoxia in the dissociated fura-2-loaded glomus cells. The increased [Ca(2+)](i) response in the hypoxic group was significantly greater than that of the normoxic group. Moreover, the gene transcripts of inflammatory mediator inducible nitric oxide synthase and chemokines (MCP-1, CCR2, MIP-1alpha, and ICAM-1) were increased in the carotid body of hypoxic rats. Collectively, results suggest that the increased expressions of proinflammatory cytokines play a functional role in the carotid body with local inflammation during chronic hypoxia.
Assuntos
Corpo Carotídeo/metabolismo , Citocinas/metabolismo , Hipóxia/metabolismo , Animais , Cálcio/metabolismo , Doença Crônica , Citocinas/genética , Hipóxia/genética , Masculino , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , RNA Mensageiro/genética , Ratos , Ratos Sprague-Dawley , Receptores de Citocinas/genética , Receptores de Citocinas/metabolismo , Regulação para CimaRESUMO
The HIF-1alpha expression in the carotid body (CB) is central to the transcriptional regulation of the CB structural and functional changes in chronic hypoxia (CH). The CB plays pathogenic roles in cardiovascular morbidity in patients with sleep-disordered breathing; yet, the expression and role of HIF-alpha subtypes in intermittent hypoxia (IH), resembling recurrent episodic apnea, are unclear. We hypothesized a divergent role of HIF-alpha subtypes, regulated by differential expression in the CB response to IH. A time-course analysis of the CB volume, and expression profiles of the HIF-1alpha, -2alpha, -3alpha and HIF-regulated gene products, including vascular endothelial growth factor (VEGF), endothelin-1 (ET-1), and tyrosine hydroxylase (TH), showed a significant difference in the lack of increase in the rat CB volume, HIF-1alpha and VEGF expression during IH, despite an increase in the mRNA level of HIF-1alpha and the prominent increase of volume and expression in the CH group. In contrast, there were increased CB expressions of HIF-2alpha and -3alpha, and also ET-1 and TH in both IH and CH groups. Results demonstrated a significant role played by HIF-2alpha and -3alpha in the CB response to IH, which could be complementary to the expression and role of HIF-1alpha under hypoxic conditions. This differential regulation of the HIF-alpha subtypes and pathways could account for the morphological and neurochemical discrepancy in the CB responses to IH and CH.