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Iturriaga R. Carotid body contribution to the physio-pathological consequences of intermittent hypoxia: role of nitro-oxidative stress and inflammation. J Physiol 2023; 601:5495-5507. [PMID: 37119020 DOI: 10.1113/jp284112] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 04/24/2023] [Indexed: 04/30/2023] Open
Abstract
Obstructive sleep apnoea (OSA), characterized by chronic intermittent hypoxia (CIH), is considered to be an independent risk for hypertension. The pathological cardiorespiratory consequences of OSA have been attributed to systemic oxidative stress, inflammation and sympathetic overflow induced by CIH, but an emerging body of evidence indicates that a nitro-oxidative and pro-inflammatory milieu within the carotid body (CB) is involved in the potentiation of CB chemosensory responses to hypoxia, which contribute to enhance the sympathetic activity. Accordingly, autonomic and cardiovascular alterations induced by CIH are critically dependent on an abnormally heightened CB chemosensory input to the nucleus of tractus solitarius (NTS), where second-order neurons project onto the rostral ventrolateral medulla (RVLM), activating pre-sympathetic neurons that control pre-ganglionic sympathetic neurons. CIH produces oxidative stress and neuroinflammation in the NTS and RVLM, which may contribute to the long-term irreversibility of the CIH-induced alterations. This brief review is mainly focused on the contribution of nitro-oxidative stress and pro-inflammatory molecules on the hyperactivation of the hypoxic chemoreflex pathway including the CB and the brainstem centres, and whether the persistence of autonomic and cardiorespiratory alterations may depend on the glial-related neuroinflammation induced by the enhanced CB chemosensory afferent input.
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Affiliation(s)
- Rodrigo Iturriaga
- Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Investigación en Fisiología y Medicina de Altura, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
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Wang L, Liu T, Wang X, Tong L, Chen G, Zhou S, Zhang H, Liu H, Lu W, Wang G, Zhang S, Du D. Microglia-derived TNF-α contributes to RVLM neuronal mitochondrial dysfunction via blocking the AMPK-Sirt3 pathway in stress-induced hypertension. J Neuroinflammation 2023; 20:137. [PMID: 37264405 DOI: 10.1186/s12974-023-02818-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 05/26/2023] [Indexed: 06/03/2023] Open
Abstract
BACKGROUND Neuroinflammation in the rostral ventrolateral medulla (RVLM) has been associated with the pathogenesis of stress-induced hypertension (SIH). Neuronal mitochondrial dysfunction is involved in many pathological and physiological processes. However, the impact of neuroinflammation on neuronal mitochondrial homeostasis and the involved signaling pathway in the RVLM during SIH are largely unknown. METHODS The morphology and phenotype of microglia and the neuronal mitochondrial injury in vivo were analyzed by immunofluorescence, Western blot, RT-qPCR, transmission electron microscopy, and kit detection. The underlying mechanisms of microglia-derived tumor necrosis factor-α (TNF-α) on neuronal mitochondrial function were investigated through in vitro and in vivo experiments such as immunofluorescence and Western blot. The effect of TNF-α on blood pressure (BP) regulation was determined in vivo via intra-RVLM microinjection of TNF-α receptor antagonist R7050. RESULTS The results demonstrated that BP, heart rate (HR), renal sympathetic nerve activity (RSNA), plasma norepinephrine (NE), and electroencephalogram (EEG) power increased in SIH rats. Furthermore, the branching complexity of microglia in the RVLM of SIH rats decreased and polarized into M1 phenotype, accompanied by upregulation of TNF-α. Increased neuronal mitochondria injury was observed in the RVLM of SIH rats. Mechanistically, Sirtuin 3 (Sirt3) and p-AMPK expression were markedly downregulated in both SIH rats and TNF-α-treated N2a cells. AMPK activator A769662 upregulated AMPK-Sirt3 signaling pathway and consequently reversed TNF-α-induced mitochondrial dysfunction. Microinjection of TNF-α receptor antagonist R7050 into the RVLM of SIH rats significantly inhibited the biological activities of TNF-α, increased p-AMPK and Sirt3 levels, and alleviated neuronal mitochondrial injury, thereby reducing c-FOS expression, RSNA, plasma NE, and BP. CONCLUSIONS This study revealed that microglia-derived TNF-α in the RVLM impairs neuronal mitochondrial function in SIH possibly through inhibiting the AMPK-Sirt3 pathway. Therefore, microglia-derived TNF-α in the RVLM may be a possible therapeutic target for the intervention of SIH.
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Affiliation(s)
- Linping Wang
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, China
- College of Life Sciences, Shanghai University, Shanghai, China
| | - Tianfeng Liu
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, China
- College of Life Sciences, Shanghai University, Shanghai, China
| | - Xueping Wang
- College of Life Sciences, Shanghai University, Shanghai, China
| | - Lei Tong
- College of Life Sciences, Shanghai University, Shanghai, China
| | - Gaojun Chen
- College of Life Sciences, Shanghai University, Shanghai, China
| | - Shumin Zhou
- College of Life Sciences, Shanghai University, Shanghai, China
| | - Haili Zhang
- College of Agriculture and Bioengineering, Heze University, Heze, Shandong, China
| | - Haisheng Liu
- College of Agriculture and Bioengineering, Heze University, Heze, Shandong, China
| | - Wen Lu
- College of Agriculture and Bioengineering, Heze University, Heze, Shandong, China
| | - Guohua Wang
- Department of Neurophysiology and Neuropharmacology, Institute of Special Environmental Medicine and Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, 226019, Jiangsu, China
| | - Shuai Zhang
- International Cooperation Laboratory of Molecular Medicine, Academy of Chinese Medical Sciences, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China.
| | - Dongshu Du
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, China.
- College of Life Sciences, Shanghai University, Shanghai, China.
- College of Agriculture and Bioengineering, Heze University, Heze, Shandong, China.
- Shaoxing Institute of Shanghai University, Shaoxing, Zhejiang, China.
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Yoshizawa M, Fukushi I, Takeda K, Kono Y, Hasebe Y, Koizumi K, Ikeda K, Pokorski M, Toda T, Okada Y. Role of microglia in blood pressure and respiratory responses to acute hypoxic exposure in rats. J Physiol Sci 2022; 72:26. [PMID: 36229778 DOI: 10.1186/s12576-022-00848-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 09/02/2022] [Indexed: 11/10/2022]
Abstract
Microglia modulate cardiorespiratory activities during chronic hypoxia. It has not been clarified whether microglia are involved in the cardiorespiratory responses to acute hypoxia. Here we investigated this issue by comparing cardiorespiratory responses to two levels of acute hypoxia (13% O2 for 4 min and 7% O2 for 5 min) in conscious unrestrained rats before and after systemic injection of minocycline (MINO), an inhibitor of microglia activation. MINO increased blood pressure but not lung ventilation in the control normoxic condition. Acute hypoxia stimulated cardiorespiratory responses in MINO-untreated rats. MINO failed to significantly affect the magnitude of hypoxia-induced blood pressure elevation. In contrast, MINO tended to suppress the ventilatory responses to hypoxia. We conclude that microglia differentially affect cardiorespiratory regulation depending on the level of blood oxygenation. Microglia suppressively contribute to blood pressure regulation in normoxia but help maintain ventilatory augmentation in hypoxia, which underscores the dichotomy of central regulatory pathways for both systems.
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Affiliation(s)
- Masashi Yoshizawa
- Department of Pediatrics, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan.,Clinical Research Center, Murayama Medical Center, Tokyo, Japan
| | - Isato Fukushi
- Clinical Research Center, Murayama Medical Center, Tokyo, Japan.,Faculty of Health Sciences, Aomori University of Health and Welfare, Aomori, Japan
| | - Kotaro Takeda
- Clinical Research Center, Murayama Medical Center, Tokyo, Japan.,Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Yosuke Kono
- Department of Pediatrics, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan.,Clinical Research Center, Murayama Medical Center, Tokyo, Japan
| | - Yohei Hasebe
- Department of Pediatrics, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan.,Clinical Research Center, Murayama Medical Center, Tokyo, Japan
| | - Keiichi Koizumi
- Department of Pediatrics, Fujiyoshida Municipal Hospital, Yamanashi, Japan
| | - Keiko Ikeda
- Institute of Innovative Research, Homeostatic Mechanism Research Unit, Tokyo Institute of Technology, Yokohama, Japan
| | | | - Takako Toda
- Department of Pediatrics, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Yasumasa Okada
- Clinical Research Center, Murayama Medical Center, Tokyo, Japan.
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Patodia S, Paradiso B, Ellis M, Somani A, Sisodiya SM, Devinsky O, Thom M. Characterisation of medullary astrocytic populations in respiratory nuclei and alterations in sudden unexpected death in epilepsy. Epilepsy Res 2019; 157:106213. [PMID: 31610338 DOI: 10.1016/j.eplepsyres.2019.106213] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 09/20/2019] [Accepted: 09/30/2019] [Indexed: 12/29/2022]
Abstract
Central failure of respiration during a seizure is one possible mechanism for sudden unexpected death in epilepsy (SUDEP). Neuroimaging studies indicate volume loss in the medulla in SUDEP and a post mortem study has shown reduction in neuromodulatory neuropeptidergic and monoaminergic neurones in medullary respiratory nuclear groups. Specialised glial cells identified in the medulla are considered essential for normal respiratory regulation including astrocytes with pacemaker properties in the pre-Botzinger complex and populations of subpial and perivascular astrocytes, sensitive to increased pCO2, that excite respiratory neurones. Our aim was to explore niches of medullary astrocytes in SUDEP cases compared to controls. In 48 brainstems from three groups, SUDEP (20), epilepsy controls (10) and non-epilepsy controls (18), sections through the medulla were labelled for GFAP, vimentin and functional markers, astrocytic gap junction protein connexin43 (Cx43) and adenosine A1 receptor (A1R). Regions including the ventro-lateral medulla (VLM; for the pre-Bötzinger complex), Median Raphe (MR) and lateral medullary subpial layer (MSPL) were quantified using image analysis for glial cell populations and compared between groups. Findings included morphologically and regionally distinct vimentin/Cx34-positive glial cells in the VLM and MR in close proximity to neurones. We noted a reduction of vimentin-positive glia in the VLM and MSPL and Cx43 glia in the MR in SUDEP cases compared to control groups (p < 0.05-0.005). In addition, we identified vimentin, Cx43 and A1R positive glial cells in the MSPL region which likely correspond to chemosensory glia identified experimentally. In conclusion, altered medullary glial cell populations could contribute to impaired respiratory regulatory capacity and vulnerability to SUDEP and warrant further investigation.
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Affiliation(s)
- Smriti Patodia
- Departments of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom
| | - Beatrice Paradiso
- Departments of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom; Cardiovascular Pathology Unit, Department of Cardiac, Thoracic and Vascular Sciences, University of Padua Medical School, Padua, Italy
| | - Matthew Ellis
- Departments of Neuropathology, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom
| | - Alyma Somani
- Departments of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom
| | - Sanjay M Sisodiya
- Departments of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom
| | - Orrin Devinsky
- New York University School of Medicine, Comprehensive Epilepsy Center, New York, United States
| | - Maria Thom
- Departments of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom; Departments of Neuropathology, UCL Queen Square Institute of Neurology, London, WC1N 3BG, United Kingdom.
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Lima-Silveira L, Accorsi-Mendonça D, Bonagamba LGH, Almado CEL, da Silva MP, Nedoboy PE, Pilowsky PM, Machado BH. Enhancement of excitatory transmission in NTS neurons projecting to ventral medulla of rats exposed to sustained hypoxia is blunted by minocycline. J Physiol 2019; 597:2903-2923. [PMID: 30993693 DOI: 10.1113/jp277532] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 04/16/2019] [Indexed: 01/13/2023] Open
Abstract
KEY POINTS Rats subjected to sustained hypoxia (SH) present increases in arterial pressure (AP) and in glutamatergic transmission in the nucleus tractus solitarius (NTS) neurons sending projections to ventrolateral medulla (VLM). Treatment with minocycline, a microglial inhibitor, attenuated the increase in AP in response to SH. The increase in the amplitude of glutamatergic postsynaptic currents in the NTS-VLM neurons, induced by postsynaptic mechanisms, was blunted by minocycline treatment. The number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS of minocycline-treated rats. The data show that microglial recruitment/proliferation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the observed increase in AP. ABSTRACT Short-term sustained hypoxia (SH) produces significant autonomic and respiratory adjustments and triggers activation of microglia, the resident immune cells in the brain. SH also enhances glutamatergic neurotransmission in the NTS. Here we evaluated the role of microglial activation induced by SH on the cardiovascular changes and mainly on glutamatergic neurotransmission in NTS neurons sending projections to the ventrolateral medulla (NTS-VLM), using a microglia inhibitor (minocycline). Direct measurement of arterial pressure (AP) in freely moving rats showed that SH (24 h, fraction of inspired oxygen ( F I , O 2 ) 0.1) in vehicle and minocycline (30 mg/kg i.p. for 3 days)-treated groups produced a significant increase in AP in relation to control groups under normoxic conditions, but this increase was significantly lower in minocycline-treated rats. Whole-cell patch-clamp recordings revealed that the active properties of the membrane were comparable among the groups. Nevertheless, the amplitudes of glutamatergic postsynaptic currents, evoked by tractus solitarius stimulation, were increased in NTS-VLM neurons of SH rats. Changes in asynchronous glutamatergic currents indicated that the observed increase in amplitude was due to postsynaptic mechanisms. These changes were blunted in the SH group previously treated with minocycline. Using immunofluorescence, we found that the number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS neurons of minocycline-treated rats. Our data support the concept that microglial activation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the increase in AP observed in this experimental model.
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Affiliation(s)
- Ludmila Lima-Silveira
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Leni G H Bonagamba
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Carlos Eduardo L Almado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Melina P da Silva
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Polina E Nedoboy
- The Heart Research Institute, Sydney, New South Wales, 2042, Australia
| | - Paul M Pilowsky
- The Heart Research Institute, Sydney, New South Wales, 2042, Australia
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
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Importance of the commissural nucleus of the solitary tract in renovascular hypertension. Hypertens Res 2019; 42:587-597. [PMID: 30622315 DOI: 10.1038/s41440-018-0190-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 10/05/2018] [Accepted: 10/09/2018] [Indexed: 12/12/2022]
Abstract
The rodent renovascular hypertension model has been used to investigate the mechanisms promoting hypertension. The importance of the carotid body for renovascular hypertension has been demonstrated. As the commissural NTS (cNTS) is the first synaptic site in the central nervous system that receives information from carotid body chemoreceptors, we evaluated the contribution of cNTS to renovascular hypertension in the present study. Normotensive male Holtzman rats were implanted with a silver clip around the left renal artery to induce two-kidney, one-clip (2K1C) hypertension. Six weeks later, isoguvacine (a GABAA agonist) or losartan (an AT1 antagonist) was injected into the cNTS, and the effects were compared with carotid body removal. Immunohistochemistry for Iba-1 and GFAP to label microglia and astrocytes, respectively, and RT-PCR for components of the renin-angiotensin system and cytokines in the NTS were also performed 6 weeks after renal surgery. The inhibition of cNTS with isoguvacine or the blockade of AT1 receptors with losartan in the cNTS decreased the blood pressure and heart rate of 2K1C rats even more than carotid body removal did. The mRNA expression of NOX2, TNF-α and IL-6, microglia, and astrocytes also increased in the cNTS of 2K1C rats compared to that of normotensive rats. These results indicate that tonically active neurons within the cNTS are essential for the maintenance of hypertension in 2K1C rats. In addition to signals from the carotid body, the present results suggest that angiotensin II directly activates the cNTS and may also induce microgliosis and astrogliosis within the NTS, which, in turn, cause oxidative stress and neuroinflammation.
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