1
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Verzele NAJ, Chua BY, Law CW, Zhang A, Ritchie ME, Wightman O, Edwards IN, Hulme KD, Bloxham CJ, Bielefeldt-Ohmann H, Trewella MW, Moe AAK, Chew KY, Mazzone SB, Short KR, McGovern AE. The impact of influenza pulmonary infection and inflammation on vagal bronchopulmonary sensory neurons. FASEB J 2021; 35:e21320. [PMID: 33660333 DOI: 10.1096/fj.202001509r] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 11/20/2020] [Accepted: 12/14/2020] [Indexed: 12/13/2022]
Abstract
Influenza A virus (IAV) is rapidly detected in the airways by the immune system, with resident parenchymal cells and leukocytes orchestrating viral sensing and the induction of antiviral inflammatory responses. The airways are innervated by heterogeneous populations of vagal sensory neurons which also play an important role in pulmonary defense. How these neurons respond to IAV respiratory infection remains unclear. Here, we use a murine model to provide the first evidence that vagal sensory neurons undergo significant transcriptional changes following a respiratory IAV infection. RNA sequencing on vagal sensory ganglia showed that IAV infection induced the expression of many genes associated with an antiviral and pro-inflammatory response and this was accompanied by a significant increase in inflammatory cell recruitment into the vagal ganglia. Assessment of gene expression in single-vagal sensory neurons confirmed that IAV infection induced a neuronal inflammatory phenotype, which was most prominent in bronchopulmonary neurons, and also evident in some neurons innervating other organs. The altered transcriptome could be mimicked by intranasal treatment with cytokines and the lung homogenates of infected mice, in the absence of infectious virus. These data argue that IAV pulmonary infection and subsequent inflammation induces vagal sensory ganglia neuroinflammation and this may have important implications for IAV-induced morbidity.
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Affiliation(s)
- Nathalie A J Verzele
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia
| | - Brendon Y Chua
- The Peter Doherty Institute for Infection and Immunity, Department of Microbiology and Immunology, University of Melbourne, Melbourne, VIC, Australia
| | - Charity W Law
- Epigenetics and Development Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Albert Zhang
- Epigenetics and Development Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Matthew E Ritchie
- Epigenetics and Development Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Oliver Wightman
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia
| | - Isaac N Edwards
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia
| | - Katina D Hulme
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia
| | - Conor J Bloxham
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia
| | - Helle Bielefeldt-Ohmann
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia.,Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, QLD, Australia
| | - Matthew W Trewella
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, VIC, Australia
| | - Aung Aung Kywe Moe
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, VIC, Australia
| | - Keng Yih Chew
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia
| | - Stuart B Mazzone
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, VIC, Australia
| | - Kirsty R Short
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia.,Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, QLD, Australia
| | - Alice E McGovern
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, VIC, Australia
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2
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Huang YC, Yuan ZF, Yang CH, Shen YJ, Lin JY, Lai CJ. Estrogen Modulates the Sensitivity of Lung Vagal C Fibers in Female Rats Exposed to Intermittent Hypoxia. Front Physiol 2018; 9:847. [PMID: 30026705 PMCID: PMC6041459 DOI: 10.3389/fphys.2018.00847] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 06/14/2018] [Indexed: 01/03/2023] Open
Abstract
Obstructive sleep apnea is mainly characterized by intermittent hypoxia (IH), which is associated with hyperreactive airway diseases and lung inflammation. Sensitization of lung vagal C fibers (LVCFs) induced by inflammatory mediators may play a central role in the pathogenesis of airway hypersensitivity. In females, estrogen interferes with inflammatory signaling pathways that may modulate airway hyperreactivity. In this study, we investigated the effects of IH on the reflex and afferent responses of LVCFs to chemical stimulants and lung inflammation in adult female rats, as well as the role of estrogen in these responses. Intact and ovariectomized (OVX) female rats were exposed to room air (RA) or IH for 14 consecutive days. On day 15, IH enhanced apneic responses to right atrial injection of chemical stimulants of LVCFs (e.g., capsaicin, phenylbiguanide, and α,β-methylene-ATP) in intact anesthetized females. Rats subjected to OVX prior to IH exposure exhibited an augmented apneic response to the same dose of stimulants compared with rats subjected to other treatments. Apneic responses to the stimulants were completely abrogated by bilateral vagotomy or perivagal capsaicin treatment, which blocked the neural conduction of LVCFs. Electrophysiological experiments revealed that in IH-exposed rats, OVX potentiated the excitability of LVCFs to stimulants. Moreover, LVCF hypersensitivity in rats subjected to OVX prior to IH exposure was accompanied by enhanced lung inflammation, which was reflected by elevated inflammatory cell infiltration in bronchoalveolar lavage fluid, lung lipid peroxidation, and protein expression of inflammatory cytokines. Supplementation with 17β-estradiol (E2) at a low concentration (30 μg/ml) but not at high concentrations (50 and 150 μg/ml) prevented the augmenting effects of OVX on LVCF sensitivity and lung inflammation caused by IH. These results suggest that ovarian hormones prevent the enhancement of LVCF sensitivity and lung inflammation by IH in female rats, which are related to the effect of low-dose estrogen.
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Affiliation(s)
- Ya-Chen Huang
- Department of Chest Section, Buddhist Tzu Chi General Hospital, Hualien City, Taiwan.,Master Program in Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien City, Taiwan
| | - Zung Fan Yuan
- Master Program in Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien City, Taiwan.,Department of Physiology, Tzu Chi University, Hualien City, Taiwan
| | - Chang-Huan Yang
- Institute of Physiology, National Yang-Ming University, Taipei, Taiwan
| | - Yan-Jhih Shen
- Ph.D. Program in Pharmacology and Toxicology, School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Jyun-Yi Lin
- Department of Chest Section, Buddhist Tzu Chi General Hospital, Hualien City, Taiwan.,Master Program in Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien City, Taiwan
| | - Ching Jung Lai
- Master Program in Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien City, Taiwan.,Department of Physiology, Tzu Chi University, Hualien City, Taiwan
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3
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Lin RL, Gu Q, Lee LY. Hypersensitivity of Vagal Pulmonary Afferents Induced by Tumor Necrosis Factor Alpha in Mice. Front Physiol 2017; 8:411. [PMID: 28659824 PMCID: PMC5470033 DOI: 10.3389/fphys.2017.00411] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 05/30/2017] [Indexed: 12/31/2022] Open
Abstract
Tumor necrosis factor alpha (TNFα), a pro-inflammatory cytokine, plays a significant role in the pathogenesis of allergic asthma. Inhalation of TNFα also induces airway hyperresponsiveness in healthy human subjects, and the underlying mechanism is not fully understood. A recent study reported that TNFα caused airway inflammation and a sustained elevation of pulmonary chemoreflex responses in mice, suggesting a possible involvement of heightened sensitivity of vagal pulmonary C-fibers. To investigate this possibility, the present study aimed to investigate the effect of a pretreatment with TNFα on the sensitivity of vagal pulmonary afferents in anesthetized mice. After TNFα (10 μg/ml, 0.03 ml) and vehicle (Veh; phosphate buffered saline (PBS), 0.03 ml) were administered by intra-tracheal instillation in each mouse of treated (TNF) and control (Veh) groups, respectively, the peak activity of pulmonary C-fibers in response to an intravenous bolus injection of a low dose of capsaicin (Cap; 0.5 μg/kg) was significantly elevated in TNF group (6.5 ± 1.3 impulses/s, n = 12) 24–48 h later, compared to that in Veh group (2.2 ± 0.5 impulses/s, n = 11; P < 0.05). Interestingly, the same low dose of Cap injection also evoked a distinct burst of discharge (2.4 ± 0.7 impulses/s) in 75% of the silent rapidly adapting receptors (RARs), a subtype of RARs exhibiting no phasic activity, in TNF group, but did not stimulate any of the silent RARs in Veh group. To further determine if this sensitizing effect involves a direct action of TNFα on these sensory nerves, the change in intracellular Ca2+ concentration in response to Cap challenge was measured in isolated mouse vagal pulmonary sensory neurons. The Cap-evoked Ca2+ influx was markedly enhanced in the neurons incubated with TNFα (50 ng/ml) for ~24 h, and this sensitizing effect was attenuated in the neurons isolated from the TNF-receptor double homozygous mutant mice. In conclusion, the TNFα pretreatment enhanced the Cap sensitivity in both pulmonary C-fibers and silent RARs, and the action was mediated through TNF receptors. These sensitizing effects of TNFα may contribute, at least in part, to the pathogenesis of airway hyperresponsiveness induced by this cytokine.
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Affiliation(s)
- Ruei-Lung Lin
- Department of Physiology, University of Kentucky, Lexington, KY, United States
| | - Qihai Gu
- Department of Biomedical Sciences, Mercer University, Macon, GA, United States
| | - Lu-Yuan Lee
- Department of Physiology, University of Kentucky, Lexington, KY, United States
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4
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Lin RL, Gu Q, Khosravi M, Lee LY. Sustained sensitizing effects of tumor necrosis factor alpha on sensory nerves in lung and airways. Pulm Pharmacol Ther 2017; 47:29-37. [PMID: 28587842 DOI: 10.1016/j.pupt.2017.06.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 05/30/2017] [Accepted: 06/03/2017] [Indexed: 01/07/2023]
Abstract
Tumor necrosis factor alpha (TNFα) plays a significant role in the pathogenesis of airway inflammatory diseases. Inhalation of aerosolized TNFα induced airway hyperresponsiveness accompanied by airway inflammation in healthy human subjects, but the underlying mechanism is not fully understood. We recently reported a series of studies aimed to investigate if TNFα elevates the sensitivity of vagal bronchopulmonary sensory nerves in a mouse model; these studies are summarized in this mini-review. Our results showed that intratracheal instillation of TNFα induced pronounced airway inflammation 24 h later, as illustrated by infiltration of eosinophils and neutrophils and the release of inflammatory mediators and cytokines in the lung and airways. Accompanying these inflammatory reactions, the sensitivity of vagal pulmonary C-fibers and silent rapidly adapting receptors to capsaicin, a selective agonist of transient receptor potential vanilloid type 1 receptor, was markedly elevated after the TNFα treatment. A distinct increase in the sensitivity to capsaicin induced by TNFα was also observed in isolated pulmonary sensory neurons, suggesting that the sensitizing effect is mediated primarily through a direct action of TNFα on these neurons. Furthermore, the same TNFα treatment also induced a lingering (>7days) cough hyperresponsiveness to inhalation challenge of NH3 in awake mice. Both the airway inflammation and the sensitizing effect on pulmonary sensory neurons caused by the TNFα treatment were abolished in the TNF-receptor double homozygous mutant mice, indicating the involvement of TNF-receptor activation. These findings suggest that the TNFα-induced hypersensitivity of vagal bronchopulmonary afferents may be responsible for, at least in part, the airway hyperresponsiveness caused by inhaled TNFα in healthy individuals.
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Affiliation(s)
- Ruei-Lung Lin
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Qihai Gu
- Department of Biomedical Sciences, Mercer University, Macon, GA, USA
| | - Mehdi Khosravi
- Department of Medicine, University of Kentucky, Lexington, KY, USA
| | - Lu-Yuan Lee
- Department of Physiology, University of Kentucky, Lexington, KY, USA.
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5
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Hsu CC, Lin YS, Lin RL, Lee LY. Immediate and delayed potentiating effects of tumor necrosis factor-α on TRPV1 sensitivity of rat vagal pulmonary sensory neurons. Am J Physiol Lung Cell Mol Physiol 2017; 313:L293-L304. [PMID: 28522561 DOI: 10.1152/ajplung.00235.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 05/05/2017] [Accepted: 05/06/2017] [Indexed: 01/19/2023] Open
Abstract
We studied acute effects of tumor necrosis factor-α (TNFα) on the sensitivity of isolated rat vagal pulmonary sensory neurons. Our results showed the following. First, a brief pretreatment with a low dose of TNFα (1.44 nM, 9 min) enhanced the sensitivity of transient receptor potential vanilloid type 1 (TRPV1) receptors in these neurons in two distinct phases: the inward current evoked by capsaicin was amplified (Δ = 247%) immediately following the TNFα pretreatment, which gradually declined toward control and then increased again reaching another peak (Δ = 384%) after 60-90 min. Second, the immediate phase of this potentiating effect of TNFα was completely abolished by a pretreatment with a selective cyclooxygenase-2 (COX-2) inhibitor, NS-398, whereas the delayed potentiation was only partially attenuated. Third, in sharp contrast, TNFα did not generate any potentiating effect on the responses to non-TRPV1 chemical activators of these neurons. Fourth, the selectivity of the TNFα action on TRPV1 was further illustrated by the responses to acid (pH 6.0); TNFα did not affect the rapid transient current mediated by acid-sensing ion channels but significantly augmented the slow sustained current mediated by TRPV1 in the same neurons. Fifth, in anesthetized rats, a similar pattern of acute sensitizing effects of TNFα on pulmonary C-fiber afferents and the involvement of COX-2 were also clearly shown. In conclusion, a brief pretreatment with TNFα induced both immediate and delayed potentiating effects on the TRPV1 sensitivity in pulmonary sensory neurons, and the production of COX-2 arachidonic acid metabolites plays a major role in the immediate sensitizing effect of TNFα.
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Affiliation(s)
- Chun-Chun Hsu
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky.,School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.,Division of Pulmonary Medicine, Department of Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan; and
| | - You Shuei Lin
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky.,Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Ruei-Lung Lin
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky
| | - Lu-Yuan Lee
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky;
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6
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Wagh AD, Sharma M, Mahapatra J, Chatterjee A, Jain M, Addepalli V. Investigation into the Role of PI3K and JAK3 Kinase Inhibitors in Murine Models of Asthma. Front Pharmacol 2017; 8:82. [PMID: 28293189 PMCID: PMC5328984 DOI: 10.3389/fphar.2017.00082] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 02/08/2017] [Indexed: 02/06/2023] Open
Abstract
Asthma is a clinical disorder commonly characterized by chronic eosinophilic inflammation, remodeling and hyper responsiveness of the airways. However, the kinases like Phosphoinositide 3 kinase (PI3K) and Janus kinase 3 (JAK3) are involved in mast cell proliferation, activation, recruitment, migration, and prolonged survival of inflammatory cells. The present study was designed to evaluate the in-vivo comparative effects of two kinase inhibitors on airway inflammation and airway remodeling in acute and chronic models of asthma. Mice were sensitized twice intra-peritoneally and then challenged by inhalation with ovalbumin (OVA). They developed an extensive inflammatory response, goblet cell hyperplasia, collagen deposition, airway smooth muscle thickening similar to pathologies observed in human asthma. The effects of PI3K inhibitor (30 mg/kg, p.o), JAK3 inhibitor (30 mg/kg, p.o) and Dexamethasone (0.3 mg/kg) on airway inflammation and remodeling in OVA sensitized/challenged BALB/c mice were evaluated. Twenty-four hours after the final antigen challenge, bronchoalveolar lavage (BAL) and histological examinations were carried out. It was observed that kinase inhibitors significantly reduced airway inflammation as evidenced by the decrease in pro inflammatory cytokines in BALF and lung homogenate and inflammatory cell count in sensitized mice after allergen challenge. Lung histological analysis showed increased infiltration of inflammatory cells, hyperplasia of goblet cells and the collagen deposition, which were significantly reduced with kinase inhibitor. In conclusion, our data suggest that PI3K and JAK3 inhibitors showed promising alternative therapeutic activity in asthma, which might significantly counteract the airway inflammation in patients with allergic asthma.
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Affiliation(s)
- Akshaya D Wagh
- Department of Pharmacology, SPP SPTM, SVKM's NMIMSMumbai, India; Department of Pharmacology, Zydus Research CentreAhmedabad, India
| | | | | | | | - Mukul Jain
- Department of Pharmacology, Zydus Research Centre Ahmedabad, India
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7
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Zhang C, Lin RL, Hong J, Khosravi M, Lee LY. Cough and expiration reflexes elicited by inhaled irritant gases are intensified in ovalbumin-sensitized mice. Am J Physiol Regul Integr Comp Physiol 2017; 312:R718-R726. [PMID: 28228416 DOI: 10.1152/ajpregu.00444.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 02/16/2017] [Accepted: 02/16/2017] [Indexed: 01/09/2023]
Abstract
This study was designed to determine the effect of active sensitization with ovalbumin (Ova) on cough responses to inhaled irritant gases in mice. Conscious mice moved freely in a recording chamber, while the pressure change in the chamber and audio and video signals of the mouse movements were recorded simultaneously to measure the frequencies of cough reflex (CR) and expiration reflex (ER). To further verify the accuracy of cough analysis, the intrapleural pressure was also recorded by a telemetry sensor surgically implanted in the intrapleural space in a subgroup of mice. During the irritant gas inhalation challenge, sulfur dioxide (SO2; 200 and 400 ppm) or ammonia (NH3; 0.1% and 0.2%) was drawn into the chamber at a constant flow rate for 8 min. Ova sensitization and sham sensitization with vehicle (Veh) were performed over a 25-day period in separate groups of mice. Our results showed that 1) both SO2 and NH3 inhalation challenges increased CR and ER frequencies in a concentration-dependent manner before Ova sensitization; 2) the baseline CR frequency was significantly elevated after Ova sensitization, accompanied by pronounced airway inflammation; and 3) Ova sensitization also markedly augmented the responses of CR and ER to both SO2 and NH3 inhalation challenges; in sharp contrast, the cough responses did not change after sham sensitization in the Veh group. In conclusion, Ova sensitization caused distinct and lingering increases in baseline cough frequency, and also intensified both CR and ER responses to inhaled irritant gases, which probably resulted from an allergic inflammation-induced hypersensitivity of airway sensory nerves.
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Affiliation(s)
- Cheng Zhang
- Department of Physiology, University of Kentucky, Lexington, Kentucky.,Department of Respiratory Medicine, Guizhou Provincial People's Hospital, Guiyang, Guizhou, China
| | - Ruei-Lung Lin
- Department of Physiology, University of Kentucky, Lexington, Kentucky
| | - Jeff Hong
- Department of Physiology, University of Kentucky, Lexington, Kentucky
| | - Mehdi Khosravi
- Department of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Lu-Yuan Lee
- Department of Physiology, University of Kentucky, Lexington, Kentucky;
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8
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Lee KZ. Phrenic motor outputs in response to bronchopulmonary C-fibre activation following chronic cervical spinal cord injury. J Physiol 2016; 594:6009-6024. [PMID: 27106483 DOI: 10.1113/jp272287] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/19/2016] [Indexed: 01/20/2023] Open
Abstract
KEY POINTS Activation of bronchopulmonary C-fibres, the main chemosensitive afferents in the lung, can induce pulmonary chemoreflexes to modulate respiratory activity. Following chronic cervical spinal cord injury, bronchopulmonary C-fibre activation-induced inhibition of phrenic activity was exaggerated. Supersensitivity of phrenic motor outputs to the inhibitory effect of bronchopulmonary C-fibre activation is due to a shift of phrenic motoneuron types and slow recovery of phrenic motoneuron discharge in cervical spinal cord-injured animals. These data suggest that activation of bronchopulmonary C-fibres may retard phrenic output recovery following cervical spinal cord injury. The alteration of phenotype and discharge pattern of phrenic motoneuron enables us to understand the impact of spinal cord injury on spinal respiratory activity. ABSTRACT Cervical spinal injury interrupts bulbospinal pathways and results in cessation of phrenic bursting ipsilateral to the lesion. The ipsilateral phrenic activity can partially recover over weeks to months following injury due to the activation of latent crossed spinal pathways and exhibits a greater capacity to increase activity during respiratory challenges than the contralateral phrenic nerve. However, whether the bilateral phrenic nerves demonstrate differential responses to respiratory inhibitory inputs is unclear. Accordingly, the present study examined bilateral phrenic bursting in response to capsaicin-induced pulmonary chemoreflexes, a robust respiratory inhibitory stimulus. Bilateral phrenic nerve activity was recorded in anaesthetized and mechanically ventilated adult rats at 8-9 weeks after C2 hemisection (C2Hx) or C2 laminectomy. Intra-jugular capsaicin (1.5 μg kg-1 ) injection was performed to activate the bronchopulmonary C-fibres to evoke pulmonary chemoreflexes. The present results indicate that capsaicin-induced prolongation of expiratory duration was significantly attenuated in C2Hx animals. However, ipsilateral phrenic activity was robustly reduced after capsaicin treatment compared to uninjured animals. Single phrenic fibre recording experiments demonstrated that C2Hx animals had a higher proportion of late-inspiratory phrenic motoneurons that were relatively sensitive to capsaicin treatment compared to early-inspiratory phrenic motoneurons. Moreover, late-inspiratory phrenic motoneurons in C2Hx animals had a weaker discharge frequency and slower recovery time than uninjured animals. These results suggest bilateral phrenic nerves differentially respond to bronchopulmonary C-fibre activation following unilateral cervical hemisection, and the severe inhibition of phrenic bursting is due to a shift in the discharge pattern of phrenic motoneurons.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan. .,Centre for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan. .,Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University and Academia Sinica, Taiwan. .,Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan. .,Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
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9
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Lin YJ, Lin RL, Khosravi M, Lee LY. Hypersensitivity of vagal pulmonary C-fibers induced by increasing airway temperature in ovalbumin-sensitized rats. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1285-91. [PMID: 26333786 DOI: 10.1152/ajpregu.00298.2015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 08/26/2015] [Indexed: 11/22/2022]
Abstract
Our recent study has shown that hyperventilation of humidified warm air (HWA) triggered cough and reflex bronchoconstriction in patients with mild asthma. We suggested that a sensitizing effect on bronchopulmonary C-fibers by increasing airway temperature was involved, but direct evidence was lacking. This study was carried out to test the hypothesis that HWA enhances the pulmonary C-fiber sensitivity in Brown-Norway rats sensitized with ovalbumin (Ova). In anesthetized rats, isocapnic hyperventilation of HWA for 3 min rapidly elevated airway temperature to a steady state of 41.7°C. Immediately after the HWA challenge, the baseline fiber activity (FA) of pulmonary C-fibers was markedly elevated in sensitized rats, but not in control rats. Furthermore, the response of pulmonary C-fibers to right atrial injection of capsaicin in sensitized rats was significantly higher than control rats before the HWA challenge, and the response to capsaicin was further amplified after HWA in sensitized rats (ΔFA = 4.51 ± 1.02 imp/s before, and 9.26 ± 1.74 imp/s after the HWA challenge). A similar pattern of the HWA-induced potentiation of the FA response to phenylbiguanide, another chemical stimulant of C-fibers, was also found in sensitized rats. These results clearly demonstrated that increasing airway temperature significantly elevated both the baseline activity and responses to chemical stimuli of pulmonary C-fibers in Ova-sensitized rats. In conclusion, this study supports the hypothesis that the increased excitability of these afferents may have contributed to the cough and reflex bronchoconstriction evoked by hyperventilation of HWA in patients with asthma.
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Affiliation(s)
| | | | - Mehdi Khosravi
- Internal Medicine, University of Kentucky Medical Center, Lexington, Kentucky
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10
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Lin RL, Lin YJ, Xu F, Lee LY. Hemorrhagic hypotension-induced hypersensitivity of vagal pulmonary C-fibers to chemical stimulation and lung inflation in anesthetized rats. Am J Physiol Regul Integr Comp Physiol 2015; 308:R605-13. [PMID: 25589016 DOI: 10.1152/ajpregu.00424.2014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 01/06/2015] [Indexed: 11/22/2022]
Abstract
This study was carried out to investigate whether hemorrhagic hypotension (HH) altered the sensitivity of vagal pulmonary C-fibers. The fiber activity (FA) of single vagal pulmonary C-fiber was continuously recorded in anesthetized rats before, during, and after HH was induced by bleeding from the femoral arterial catheter into a blood reservoir and lowering the mean systemic arterial pressure (MSAP) to ∼40 mmHg for 20 min. Our results showed the following. First, after MSAP reached a steady state of HH, the peak FA response to intravenous injection of capsaicin was elevated by approximately fivefold. The enhanced C-fiber sensitivity continued to increase during HH and sustained even after MSAP returned to baseline during the recovery, but slowly returned to control ∼20 min later. Second, responses of FA to intravenous injections of other chemical stimulants of pulmonary C-fibers (phenylbiguanide, lactic acid, and adenosine) and a constant-pressure lung hyperinflation were all significantly potentiated by HH. Third, infusion of sodium bicarbonate alleviated the systemic acidosis during HH, and it also attenuated, but did not completely prevent, the HH-induced C-fiber hypersensitivity. In conclusion, the pulmonary C-fiber sensitivity was elevated during HH, probably caused by the endogenous release of chemical substances (e.g., lactic acid) that were produced by tissue ischemia during HH. This enhanced C-fiber sensitivity may heighten the pulmonary protective reflexes mediated through these afferents (e.g., cough, J reflex) during hemorrhage when the body is more susceptible to other hazardous insults and pathophysiological stresses.
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Affiliation(s)
- Ruei-Lung Lin
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky; and
| | - Yu-Jung Lin
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky; and
| | - Fadi Xu
- Lovelace Respiratory Research Institute, Albuquerque, New Mexico
| | - Lu-Yuan Lee
- Department of Physiology, University of Kentucky Medical Center, Lexington, Kentucky; and
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11
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Lee KZ, Chang YS. Recovery of the pulmonary chemoreflex and functional role of bronchopulmonary C-fibers following chronic cervical spinal cord injury. J Appl Physiol (1985) 2014; 117:1188-98. [PMID: 25257870 DOI: 10.1152/japplphysiol.00723.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Persistent impairment of pulmonary defense reflexes is a critical factor contributing to pulmonary complications in patients with spinal cord injuries. The pulmonary chemoreflex evoked by activation of bronchopulmonary C-fibers has been reported to be abolished in animals with acute cervical hemisection (C2Hx). The present study examined whether the pulmonary chemoreflex can recover during the chronic injury phase and investigated the role of bronchopulmonary C-fibers on the altered breathing pattern after C2Hx. In the first protocol, bronchopulmonary C-fibers were excited by intrajugular capsaicin administration in uninjured and complete C2Hx animals 8 wk postsurgery. Capsaicin evoked pulmonary chemoreflexes in both groups, but the reflex intensity was significantly weaker in C2Hx animals. To examine whether spared spinal white matter tissue contributes to pulmonary chemoreflex recovery, the reflex was evaluated in animals with different extents of lateral injury. Linear regression analyses revealed that tidal volume significantly correlated with the extent of spared tissue; however, capsaicin-induced apnea was not related to injury severity when the ipsilateral-to-contralateral white matter ratio was <50%. In the second protocol, the influence of background bronchopulmonary C-fiber activity on respiration was investigated by blocking C-fiber conduction via perivagal capsaicin treatment. The rapid shallow breathing of C2Hx animals persisted after perivagal capsaicin treatment despite attenuation of pulmonary chemoreflexes. These results indicate that the pulmonary chemoreflex can recover to some extent following spinal injury, but remains attenuated even when there is moderate spinal tissue sparing, and that altered breathing pattern of C2Hx animals cannot be attributed to endogenous activation of bronchopulmonary C-fibers.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan; Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan; Center for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan; and Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yu-Shuo Chang
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
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Tsai IL, Lee KZ. Attenuation of the pulmonary chemoreflex following acute cervical spinal cord injury. J Appl Physiol (1985) 2014; 116:757-66. [DOI: 10.1152/japplphysiol.01370.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bronchopulmonary C fibers are the primary chemosensitive afferents in the lung. The activation of bronchopulmonary C fibers evokes the pulmonary chemoreflex, which is characterized by apnea, hypotension, and bradycardia and is a critical reflex that modulates cardiorespiratory responses under physiological and pathological conditions. The present study was designed to investigate whether the pulmonary chemoreflex is altered following acute cervical spinal injury. A unilateral hemisection (Hx) or laminectomy (uninjured) in the second cervical spinal cord was performed in adult male Sprague-Dawley rats. The pulmonary chemoreflex induced by intrajugular capsaicin administration was evaluated by measuring respiratory airflow in spontaneously breathing rats and phrenic nerve activity in mechanically ventilated rats. Capsaicin treatment evoked a cessation of respiratory airflow and phrenic bursting in uninjured animals, but not in C2Hx animals. To clarify whether the attenuation of the pulmonary chemoreflex in C2Hx animals is restricted to capsaicin-induced stimuli, or generally applied to other stimuli that excite bronchopulmonary C fibers, another bronchopulmonary C-fiber stimulant (phenylbiguanide) was used to evoke the pulmonary chemoreflex in spontaneously breathing rats. We observed that phenylbiguanide-induced apnea was also blunted in C2Hx animals, suggesting that the respiratory response induced by bronchopulmonary C-fiber activation was attenuated following acute cervical spinal Hx. The blunted inhibitory respiratory response may represent a compensatory respiratory plasticity to preserve the breathing capacity and may also reduce the capability of preventing inhaled irritants in this injured condition.
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Affiliation(s)
- I-Lun Tsai
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan; and
- Center for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
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