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Akkaif MA, Ng ML, Sk Abdul Kader MA, Daud NAA, Sha'aban A, Ibrahim B. A review of the effects of ticagrelor on adenosine concentration and its clinical significance. Pharmacol Rep 2021; 73:1551-1564. [PMID: 34283374 DOI: 10.1007/s43440-021-00309-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/05/2021] [Accepted: 07/06/2021] [Indexed: 12/01/2022]
Abstract
BACKGROUND Ticagrelor is an oral antiplatelet drug that can reversibly bind to the platelet P2Y12 receptor. Ticagrelor is metabolized mainly by CYP3A4 and produces a rapid blood concentration-dependent platelet inhibitory effect. Unlike other P2Y12 receptor antagonists, many clinical features of ticagrelor are not related to P2Y12 receptor antagonism. PURPOSE This review aims to gather existing literature on the clinical effects of ticagrelor after inhibiting adenosine uptake. METHODOLOGY The current study reviewed literature related to the effects of ticagrelor on adenosine metabolism. The review also examined the drug's biological effects and clinical characteristics to see how it could be used in a clinical setting. RESULTS Many studies have shown that ticagrelor can inhibit equilibrative nucleoside transporter 1 (ENT1). This inhibition leads to intracellular adenosine uptake, increased adenosine half-life and plasma concentration levels and an enhanced adenosine-mediated biological effect. CONCLUSIONS Based on the studies reviewed, it was found that ticagrelor essentially inhibits adenosine absorption of adenosine into cells through ENT1, which increases the concentration in the blood and subsequently increases the protection of the heart muscle by adenosine. It also prevents platelet aggregation, and extends the biological effects of coronary arteries. Moreover, it leads to a lower mortality rate in acute coronary syndrome (ACS) patients.
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Affiliation(s)
- Mohammed Ahmed Akkaif
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Gelugor, Penang, Malaysia
| | - Mei Li Ng
- Advanced Medical and Dental Institute, Universiti Sains Malaysia, 13200, Gelugor, Penang, Malaysia
| | | | - Nur Aizati Athirah Daud
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Gelugor, Penang, Malaysia
| | - Abubakar Sha'aban
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Gelugor, Penang, Malaysia
| | - Baharudin Ibrahim
- Faculty of Pharmacy, University of Malaya, 50603, Kuala Lumpur, Malaysia.
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Mazzone SB, Undem BJ. Vagal Afferent Innervation of the Airways in Health and Disease. Physiol Rev 2017; 96:975-1024. [PMID: 27279650 DOI: 10.1152/physrev.00039.2015] [Citation(s) in RCA: 320] [Impact Index Per Article: 45.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Vagal sensory neurons constitute the major afferent supply to the airways and lungs. Subsets of afferents are defined by their embryological origin, molecular profile, neurochemistry, functionality, and anatomical organization, and collectively these nerves are essential for the regulation of respiratory physiology and pulmonary defense through local responses and centrally mediated neural pathways. Mechanical and chemical activation of airway afferents depends on a myriad of ionic and receptor-mediated signaling, much of which has yet to be fully explored. Alterations in the sensitivity and neurochemical phenotype of vagal afferent nerves and/or the neural pathways that they innervate occur in a wide variety of pulmonary diseases, and as such, understanding the mechanisms of vagal sensory function and dysfunction may reveal novel therapeutic targets. In this comprehensive review we discuss historical and state-of-the-art concepts in airway sensory neurobiology and explore mechanisms underlying how vagal sensory pathways become dysfunctional in pathological conditions.
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Affiliation(s)
- Stuart B Mazzone
- School of Biomedical Sciences, The University of Queensland, St Lucia, Brisbane, Australia; and Department of Medicine, Johns Hopkins University Medical School, Asthma & Allergy Center, Baltimore, Maryland
| | - Bradley J Undem
- School of Biomedical Sciences, The University of Queensland, St Lucia, Brisbane, Australia; and Department of Medicine, Johns Hopkins University Medical School, Asthma & Allergy Center, Baltimore, Maryland
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Yang CH, Shen YJ, Lai CJ, Kou YR. Inflammatory Role of ROS-Sensitive AMP-Activated Protein Kinase in the Hypersensitivity of Lung Vagal C Fibers Induced by Intermittent Hypoxia in Rats. Front Physiol 2016; 7:263. [PMID: 27445853 PMCID: PMC4922301 DOI: 10.3389/fphys.2016.00263] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 06/14/2016] [Indexed: 12/18/2022] Open
Abstract
Obstructive sleep apnea (OSA), manifested by airway exposure to intermittent hypoxia (IH), is associated with excess reactive oxygen species (ROS) production in airways, airway inflammation, and hyperreactive airway diseases. The cause-effect relationship for these events remains unclear. We investigated the inflammatory role of ROS-sensitive AMP-activated protein kinase (AMPK) in IH-induced airway hypersensitivity mediated by lung vagal C fibers (LVCFs) in rats. Conscious rats were exposed to room air (RA) or IH with or without treatment with N-acetyl-L-cysteine (NAC, an antioxidant), Compound C (an AMPK inhibitor), ibuprofen (a cyclooxygenase inhibitor), or their vehicles. Immediately after exposure (24 h), we found that intravenous capsaicin, phenylbiguanide, or α,β-methylene-ATP evoked augmented LVCF-mediated apneic responses and LVCF afferent responses in rats subjected to IH exposure in comparison with those in RA rats. The potentiating effect of IH on LVCF responses decreased at 6 h after and vanished at 12 h after the termination of IH exposure. The potentiating effect of IH on LVCF-mediated apneic and LVCF afferent responses was significantly attenuated by treatment with NAC, compound C, or ibuprofen, but not by their vehicles. Further biochemical analysis revealed that rats exposed to IH displayed increased lung levels of lipid peroxidation (an index of oxidative stress), AMPK phosphorylation (an index of AMPK activation), and prostaglandin E2 (a cyclooxygenase metabolite), compared with those exposed to RA. IH-induced increase in lipid peroxidation was considerably suppressed by treatment with NAC but not by compound C or ibuprofen. IH-induced increase in AMPK phosphorylation was totally abolished by NAC or compound C but not by ibuprofen. IH-induced increase in prostaglandin E2 was considerably prevented by any of these three inhibitor treatments. The vehicles of these inhibitors exerted no significant effect on the three IH-induced responses. These results suggest that 24-h IH exposure sensitizes LVCFs, leading to an exaggerated reflex and afferent responses to chemical stimulants in rats. Moreover, this IH-induced LVCF sensitization is mediated through a cascade of inflammatory responses in the airways involving increases in ROS, AMPK activation, and cyclooxygenase metabolite release.
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Affiliation(s)
- Chang-Huan Yang
- Institute of Physiology, School of Medicine, National Yang-Ming University Taipei, Taiwan
| | - Yan-Jhih Shen
- Department of Pharmacology and Toxicology, School of Medicine, Tzu Chi University Hualien, Taiwan
| | - Ching Jung Lai
- Department of Physiology, Tzu Chi University Hualien, Taiwan
| | - Yu Ru Kou
- Institute of Physiology, School of Medicine, National Yang-Ming University Taipei, Taiwan
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Yang CH, Zhuang WL, Shen YJ, Lai CJ, Kou YR. NADPH Oxidase-Derived ROS Induced by Chronic Intermittent Hypoxia Mediates Hypersensitivity of Lung Vagal C Fibers in Rats. Front Physiol 2016; 7:166. [PMID: 27242540 PMCID: PMC4860401 DOI: 10.3389/fphys.2016.00166] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/21/2016] [Indexed: 12/04/2022] Open
Abstract
Obstructive sleep apnea (OSA), manifested by exposure to chronic intermittent hypoxia (CIH) and excess production of reactive oxygen species (ROS) in the airways, is associated with hyperreactive airway diseases. ROS, particularly when created by NADPH oxidase, are known to sensitize lung vagal C fibers (LVCFs), which may contribute to airway hypersensitivity pathogenesis. We investigated whether CIH augments the reflex and afferent responses of LVCFs to chemical stimulants and the roles of ROS and NADPH oxidase in such airway hypersensitivity. Rats were exposed to room air (RA) or CIH with/without daily treatment with MnTMPyP (a superoxide anion scavenger), apocynin (an NADPH oxidase inhibitor), or vehicle. At 16 h after their last exposure, intravenous capsaicin, adenosine, or α,β-methylene-ATP evoked an augmented apneic response in anesthetized rats with 14-days CIH exposure, compared to anesthetized rats with 14-days RA exposure. The augmented apneic responses to these LVCF stimulants were abolished by bilateral vagotomy or perivagal capsaicin treatment, which block LVCFs neural conduction and were significantly suppressed by treatment with MnTMPyP or apocynin, but not vehicle. Electrophysiological studies revealed that 14-days CIH exposure potentiated the responses of LVCFs to these stimulants. This effect was inhibited by treatment with MnTMPyP or apocynin treatment and was not seen in rats who received 7-days of CIH exposure. Biochemical analysis indicated that 14-days CIH exposure increased both lung lipid peroxidation, which is indicative of oxidative stress, and expression of the p47phox subunit in the membrane fraction of lung tissue, which is an index of NADPH oxidase activation. The former was prevented by treatment with either MnTMPyP or apocynin, while the later was prevented by treatment with apocynin only. These results suggest that 14-days CIH exposure sensitizes LVCFs in rats, leading to an exaggerated reflex and afferent responses to stimulants and that this sensitization is mediated via ROS generated by NADPH oxidase.
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Affiliation(s)
- Chang-Huan Yang
- School of Medicine, Institute of Physiology, National Yang-Ming University Taipei, Taiwan
| | - Wei-Ling Zhuang
- Department of Physiology, Tzu Chi University Hualien, Taiwan
| | - Yan-Jhih Shen
- PhD Program in Pharmacology and Toxicology, School of Medicine, Tzu Chi University Hualien, Taiwan
| | - Ching Jung Lai
- Department of Physiology, Tzu Chi University Hualien, Taiwan
| | - Yu Ru Kou
- School of Medicine, Institute of Physiology, National Yang-Ming University Taipei, Taiwan
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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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Ruan T, Lin YJ, Hsu TH, Lu SH, Jow GM, Kou YR. Sensitization by pulmonary reactive oxygen species of rat vagal lung C-fibers: the roles of the TRPV1, TRPA1, and P2X receptors. PLoS One 2014; 9:e91763. [PMID: 24699274 PMCID: PMC3974698 DOI: 10.1371/journal.pone.0091763] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 02/13/2014] [Indexed: 11/18/2022] Open
Abstract
Sensitization of vagal lung C-fibers (VLCFs) induced by mediators contributes to the pathogenesis of airway hypersensitivity, which is characterized by exaggerated sensory and reflex responses to stimulants. Reactive oxygen species (ROS) are mediators produced during airway inflammation. However, the role of ROS in VLCF-mediated airway hypersensitivity has remained elusive. Here, we report that inhalation of aerosolized 0.05% H2O2 for 90 s potentiated apneic responses to intravenous capsaicin (a TRPV1 receptor agonist), α,β-methylene-ATP (a P2X receptor agonist), and phenylbiguanide (a 5-HT3 receptor agonist) in anesthetized rats. The apneic responses to these three stimulants were abolished by vagatomy or by perivagal capsaicin treatment, a procedure that blocks the neural conduction of VLCFs. The potentiating effect of H2O2 on the apneic responses to these VLCF stimulants was prevented by catalase (an enzyme that degrades H2O2) and by dimethylthiourea (a hydroxyl radical scavenger). The potentiating effect of H2O2 on the apneic responses to capsaicin was attenuated by HC-030031 (a TRPA1 receptor antagonist) and by iso-pyridoxalphosphate-6-azophenyl-2',5'-disulphonate (a P2X receptor antagonist). The potentiating effect of H2O2 on the apneic responses to α,β-methylene-ATP was reduced by capsazepine (a TRPV1 receptor antagonist), and by HC-030031. The potentiating effect of H2O2 on the apneic responses to phenylbiguanide was totally abolished when all three antagonists were combined. Consistently, our electrophysiological studies revealed that airway delivery of aerosolized 0.05% H2O2 for 90 s potentiated the VLCF responses to intravenous capsaicin, α,β-methylene-ATP, and phenylbiguanide. The potentiating effect of H2O2 on the VLCF responses to phenylbiguanide was totally prevented when all antagonists were combined. Inhalation of 0.05% H2O2 indeed increased the level of ROS in the lungs. These results suggest that 1) increased lung ROS sensitizes VLCFs, which leads to exaggerated reflex responses in rats and 2) the TRPV1, TRPA1, and P2X receptors are all involved in the development of this airway hypersensitivity.
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Affiliation(s)
- Ting Ruan
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
- Department of Physiology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Yu-Jung Lin
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Tien-Huan Hsu
- Department of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan
| | - Shing-Hwa Lu
- Department of Urology, Taipei City Hospital, Zhong-Xiao Branch, Taipei, Taiwan
| | - Guey-Mei Jow
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Yu Ru Kou
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, 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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8
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Willis DN, Morris JB. Modulation of Sensory Irritation Responsiveness by Adenosine and Malodorants. Chem Senses 2012; 38:91-100. [DOI: 10.1093/chemse/bjs085] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Shen MY, Luo YL, Yang CH, Ruan T, Lai CJ. Hypersensitivity of lung vagal C fibers induced by acute intermittent hypoxia in rats: role of reactive oxygen species and TRPA1. Am J Physiol Regul Integr Comp Physiol 2012; 303:R1175-85. [PMID: 23076873 DOI: 10.1152/ajpregu.00227.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Obstructive sleep apnea, manifested by intermittent hypoxia and excess production of reactive oxygen species (ROS) in airways, is associated with hyperreactive airway diseases, but the mechanism remains unclear. Sensitization of lung vagal C fibers (LVCFs) contributes to the airway hypersensitivity. We investigated the mechanisms underlying the sensitization of LVCFs with acute intermittent hypoxia (AIH), by 10 episodes of exposure to 30 s of hypoxic air (0%, 5%, or 10% O(2)) followed by 30 s of room air in anesthetized, open-chest, and artificially ventilated rats. Reflex apneic response to intravenous capsaicin (an LVCF stimulant), as measured by phrenic nerve activity, was concentration dependently augmented by AIH. Similarly, reflex apneic response to intravenous α,β-methylene-ATP (another LVCF stimulant) was augmented by AIH (0% O(2)). The reflex apnea evoked by these two stimulants was abolished by bilateral vagotomy, which suggests the involvement of lung vagal afferents. The AIH-augmented apneic response to these two stimulants was prevented by pretreatment with dimethylthiourea (a hydroxyl radical scavenger), N-acetyl-l-cysteine (an antioxidant) and HC-030031 [a transient receptor potential ankyrin 1 (TRPA1) receptor antagonist]. Consistently, electrophysiological study revealed the afferent responses of LVCFs to capsaicin or α,β-methylene-ATP were augmented by AIH, and this sensitization of LVCFs was prevented by dimethylthiourea, N-acetyl-l-cysteine, and HC-030031. In contrast, AIH did not alter the afferent response of LVCFs to mechanical stimulation by lung hyperinflation. We concluded that AIH sensitizes LVCFs in rats, thus resulting in exaggerated airway reflexogenic responses to chemical stimulants, possibly by ROS action and activation of TRPA1 receptors.
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Affiliation(s)
- Mei-Ya Shen
- Department of Physiology, Tzu Chi University, Hualien, Taiwan
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Burnstock G, Brouns I, Adriaensen D, Timmermans JP. Purinergic signaling in the airways. Pharmacol Rev 2012; 64:834-68. [PMID: 22885703 DOI: 10.1124/pr.111.005389] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Evidence for a significant role and impact of purinergic signaling in normal and diseased airways is now beyond dispute. The present review intends to provide the current state of knowledge of the involvement of purinergic pathways in the upper and lower airways and lungs, thereby differentiating the involvement of different tissues, such as the epithelial lining, immune cells, airway smooth muscle, vasculature, peripheral and central innervation, and neuroendocrine system. In addition to the vast number of well illustrated functions for purinergic signaling in the healthy respiratory tract, increasing data pointing to enhanced levels of ATP and/or adenosine in airway secretions of patients with airway damage and respiratory diseases corroborates the emerging view that purines act as clinically important mediators resulting in either proinflammatory or protective responses. Purinergic signaling has been implicated in lung injury and in the pathogenesis of a wide range of respiratory disorders and diseases, including asthma, chronic obstructive pulmonary disease, inflammation, cystic fibrosis, lung cancer, and pulmonary hypertension. These ostensibly enigmatic actions are based on widely different mechanisms, which are influenced by the cellular microenvironment, but especially the subtypes of purine receptors involved and the activity of distinct members of the ectonucleotidase family, the latter being potential protein targets for therapeutic implementation.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Royal Free Campus, London, UK.
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Activation of opioid μ-receptors, but not δ- or κ-receptors, switches pulmonary C-fiber-mediated rapid shallow breathing into an apnea in anesthetized rats. Respir Physiol Neurobiol 2012; 183:211-7. [PMID: 22796630 DOI: 10.1016/j.resp.2012.06.032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 06/25/2012] [Accepted: 06/26/2012] [Indexed: 11/21/2022]
Abstract
Rapid shallow breathing (RSB) is mainly mediated by bronchopulmonary C-fibers (PCFs). We asked whether this RSB could be modulated by opioids. In anesthetized rats right atrial bolus injection of phenylbiguanide (PBG) to evoke RSB was repeated after: (1) intravenously giving fentanyl (μ-receptor agonist), DPDPE (δ-receptor agonist), or U-50488H (κ-receptor agonist); (2) fentanyl (iv) following naloxone methiodide, a peripheral opioid receptor antagonist; (3) bilateral microinjection of fentanyl into the nodose ganglia; (4) fentanyl (iv) with pre-blocking histamine H(1) and H(2) receptors by diphenhydramine and ranitidine. Systemic fentanyl challenge, but not DPDPE or U-50488H, switched the PBG-induced RSB to a long lasting apnea. This switch was blocked by naloxone methiodide rather than diphenhydramine and ranitidine. After microinjecting fentanyl into the nodose ganglia, PBG also produced an apnea. Our results suggest that activating μ-receptors is capable of turning the PCF-mediated RSB into an apnea, at least partly, via facilitating PCFs' activity and this switching effect appears independent of the released histamine.
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da Silva VJD, Gnecchi-Ruscone T, Bellina V, Oliveira M, Maciel L, de Carvalho ACC, Salgado HC, Bergamaschi CM, Tobaldini E, Porta A, Montano N. Acute adenosine increases cardiac vagal and reduces sympathetic efferent nerve activities in rats. Exp Physiol 2012; 97:719-29. [PMID: 22366563 DOI: 10.1113/expphysiol.2011.063925] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Adenosine is the first drug of choice in the treatment of supraventricular arrhythmias. While the effects of adenosine on sympathetic nerve activity (SNA) have been investigated, no information is available on the effects on cardiac vagal nerve activity (VNA). We assessed in rats the responses of cardiac VNA, SNA and cardiovascular variables to intravenous bolus administration of adenosine. In 34 urethane-anaesthetized rats, cardiac VNA or cervical preganglionic sympathetic fibres were recorded together with ECG, arterial pressure and ventilation, before and after administration of three doses of adenosine (100, 500 and 1000 μg kg(-1)). The effects of adenosine were also assessed in isolated perfused hearts (n = 5). Adenosine induced marked bradycardia and hypotension, associated with a significant dose-dependent increase in VNA (+204 ± 56%, P < 0.01; +275 ± 120%, P < 0.01; and +372 ± 78%, P < 0.01, for the three doses, respectively; n = 7). Muscarinic blockade by atropine (5 mg kg(-1), i.v.) significantly blunted the adenosine-induced bradycardia (-56.0 ± 4.5%, P < 0.05; -86.2 ± 10.5%, P < 0.01; and -34.3 ± 9.7%, P < 0.01, respectively). Likewise, adenosine-induced bradycardia was markedly less in isolated heart preparations. Previous barodenervation did not modify the effects of adenosine on VNA. On the SNA side, adenosine administration was associated with a dose-dependent biphasic response, including overactivation in the first few seconds followed by a later profound SNA reduction. Earliest sympathetic activation was abolished by barodenervation, while subsequent sympathetic withdrawal was affected neither by baro- nor by chemodenervation. This is the first demonstration that acute adenosine is able to activate cardiac VNA, possibly through a central action. This increase in vagal outflow could make an important contribution to the antiarrhythmic action of this substance.
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Affiliation(s)
- Valdo Jose Dias da Silva
- Department of Clinical Sciences, University of Milan, Internal Medicine II, L. Sacco Hospital, Milan, Italy
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Kan H, Wu Z, Young SH, Chen TH, Cumpston JL, Chen F, Kashon ML, Castranova V. Pulmonary exposure of rats to ultrafine titanium dioxide enhances cardiac protein phosphorylation and substance P synthesis in nodose ganglia. Nanotoxicology 2011; 6:736-45. [PMID: 21877901 DOI: 10.3109/17435390.2011.611915] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The inhalation of engineered nanoparticles stimulates the development of atherosclerosis and impairs vascular function. However, the cardiac effects of inhaled engineered nanoparticles are unknown. Here, we investigate the effects of ultrafine titanium dioxide (UFTiO(2)) on the heart, and we define the possible mechanisms underlying the measured effects. Pulmonary exposure of rats to UFTiO(2) increased the phosphorylation levels of p38 mitogen-activated protein kinase and cardiac troponin I, but not Akt, in the heart and substance P synthesis in nodose ganglia. Circulatory levels of pro-inflammatory cytokines, and blood cell counts and differentials were not significantly changed after pulmonary exposure. Separately, the incubation of cardiac myocytes isolated from naïve adult rat hearts in vitro with UFTiO(2) did not alter the phosphorylation status of the same cardiac proteins. In conclusion, the inhalation of UFTiO(2) enhanced the phosphorylation levels of cardiac proteins. Such responses are likely independent of systemic inflammation, but may involve a lung-neuron-regulated pathway.
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Affiliation(s)
- Hong Kan
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.
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Abstract
The mechanisms and pathways of the sensation of dyspnea are incompletely understood, but recent studies have provided some clarification. Studies of patients with cord transection or polio, induced spinal anesthesia, or induced respiratory muscle paralysis indicate that activation of the respiratory muscles is not essential for the perception of dyspnea. Similarly, reflex chemostimulation by CO₂ causes dyspnea, even in the presence of respiratory muscle paralysis or cord transection, indicating that reflex chemoreceptor stimulation per se is dyspnogenic. Sensory afferents in the vagus nerves have been considered to be closely associated with dyspnea, but the data were conflicting. However, recent studies have provided evidence of pulmonary vagal C-fiber involvement in the genesis of dyspnea, and recent animal data provide a basis to reconcile differences in responses to various C-fiber stimuli, based on the ganglionic origin of the C fibers. Brain imaging studies have provided information on central pathways subserving dyspnea: Dyspnea is associated with activation of the limbic system, especially the insular area. These findings permit a clearer understanding of the mechanisms of dyspnea: Afferent information from reflex stimulation of the peripheral sensors (chemoreceptors and/or vagal C fibers) is processed centrally in the limbic system and sensorimotor cortex and results in increased neural output to the respiratory muscles. A perturbation in the ventilatory response due to weakness, paralysis, or increased mechanical load generates afferent information from vagal receptors in the lungs (and possibly mechanoreceptors in the respiratory muscles) to the sensorimotor cortex and results in the sensation of dyspnea.
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Affiliation(s)
- Nausherwan K Burki
- University of Connecticut Health Center, Pulmonary Medicine-MC 1321, 263 Farmington Ave, Farmington, CT 06030, USA.
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15
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Vagal afferent nerves with the properties of nociceptors. Auton Neurosci 2009; 153:12-20. [PMID: 19751993 DOI: 10.1016/j.autneu.2009.08.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 08/05/2009] [Accepted: 08/10/2009] [Indexed: 12/19/2022]
Abstract
Vagal afferent nerves are essential for optimal neural regulation of visceral organs, but are not often considered important for their defense. However, there are well-defined subsets of vagal afferent nerves that have activation properties indicative of specialization to detect potentially harmful stimuli (nociceptors). This is clearly exemplified by the vagal bronchopulmonary C-fibers that are quiescent in healthy lungs but are readily activated by noxious chemicals and inflammatory molecules. Vagal afferent nerves with similar activation properties have been also identified in the esophagus and probably exist in other visceral tissues. In addition, these putative vagal nociceptors often initiate defensive reflexes, can be sensitized, and have the capacity to induce central sensitization. This set of properties is a characteristic of nociceptors in somatic tissues.
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16
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Lin YS, Lin RL, Bien MY, Ho CY, Kou YR. Sensitization of capsaicin-sensitive lung vagal afferents by anandamide in rats: role of transient receptor potential vanilloid 1 receptors. J Appl Physiol (1985) 2009; 106:1142-52. [DOI: 10.1152/japplphysiol.91229.2008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Anandamide (AEA), an arachidonic acid derivative produced during inflammatory conditions, is an endogenous agonist of both transient receptor potential vanilloid 1 (TRPV1) receptors and cannabinoid CB1 receptors. Sensitization of capsaicin-sensitive lung vagal afferent (CSLVA) fibers by chemical mediators is important in the pathogenesis of hyperreactive airway diseases. We investigated the effect of the intravenous infusion of AEA (2 mg·kg−1·ml−1, 0.5 ml/min for 2 min) on the sensitivity of CSLVA fibers to chemical and mechanical stimulation in anesthetized rats. In artificially ventilated rats, AEA infusion only mildly elevated the baseline activity of CSLVA fibers. However, CSLVA fiber responses to right atrial injection of capsaicin, AEA, or adenosine and to lung inflation (tracheal pressure = 30 cmH2O) were all markedly potentiated during AEA infusion, which reverted 20 min after termination of the infusion. The potentiating effect on the sensitivity of CSLVA fibers to adenosine injection or lung inflation was completely blocked by pretreatment with capsazepine (a TRPV1 receptor antagonist) but was unaffected by pretreatment with AM281 (a CB1 receptor antagonist). In spontaneously breathing rats, right atrial injection of adenosine evoked an apneic response that is presumably mediated through CSLVA fibers. Similarly, the adenosine-evoked apneic response was potentiated during AEA infusion, and this potentiating effect was also completely prevented by pretreatment with capsazepine. These results suggest that AEA infusion at the dose tested produces a mild activation of TRPV1 receptors and this nonspecifically increases CSLVA fiber sensitivity to chemical and mechanical stimulation.
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17
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Kuo YL, Lai CJ. Ovalbumin sensitizes vagal pulmonary C-fiber afferents in Brown Norway rats. J Appl Physiol (1985) 2008; 105:611-20. [PMID: 18535139 DOI: 10.1152/japplphysiol.01099.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sensitization of vagal lung C fibers has been postulated to contribute to the development of asthma, but support for this notion is still lacking. We investigated the characteristics and function of pulmonary C fibers (PCFs) in ovalbumin (OVA)-sensitized Brown Norway rats, an established animal model of asthma. Rats were sensitized with intraperitoneal injection of OVA or were treated with saline (control). In study 1, with the use of open-chest and artificially ventilated rats, inhalation of 5% OVA aerosol evoked an augmented increase in total lung resistance in the OVA-sensitized rats, compared with the control rats. Bilateral vagotomy or subcutaneous pretreatment with a high-dose of capsaicin for blocking of C-fiber function equally attenuated this augmented total lung resistance response, suggesting the involvement of PCFs. In study 2, with the use of anesthetized, spontaneously breathing rats, right atrial injection of capsaicin (1 microg/kg; a PCF stimulant) evoked an augmented apneic response in the OVA-sensitized rats, compared with the control rats. In study 3, with the use of open-chest, paralyzed, and artificially ventilated rats, the afferent PCF responses to right atrial injection of capsaicin (0.5 and 1.0 microg/kg), phenylbiguanide (8 microg/kg; a PCF stimulant), or adenosine (0.2 mg/kg; a PCF stimulant) were enhanced in the OVA-sensitized rats, compared with the control rats. However, the baseline activities of PCFs and their afferent responses to mechanical stimulation by lung hyperinflation in the OVA-sensitized and control rats were comparable. Our results suggested that OVA-sensitized Brown Norway rats possess sensitized vagal PCFs, which may participate in the development of the airway hyperreactivity observed in these animals.
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Affiliation(s)
- Y L Kuo
- Institute of Neuroscience, Department of Physiology, Tzu Chi University, No. 701, Sec. 3, Chung-Yang Rd., Hualien 97004, Taiwan
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18
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Desesa CR, Vaughan RP, Lanosa MJ, Fontaine KG, Morris JB. Sulfur-containing malodorant vapors enhance responsiveness to the sensory irritant capsaicin. Toxicol Sci 2008; 104:198-209. [PMID: 18375943 DOI: 10.1093/toxsci/kfn061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The nose is innervated with both odor responsive olfactory (cranial nerve I) and irritant responsive trigeminal (cranial nerve V) nerves. The nature and extent of any interactions between these two nerves is poorly understood. The aim of the current study was to determine if two sulfur-containing malodorants, ethyl sulfide and t-butyl sulfide, modulated responsiveness to the trigeminal C fiber stimulant capsaicin using female C57Bl/6J mice as an experimental model. Cessation or marked slowing of flow at the onset of each expiration (termed braking) was used as a biomarker for trigeminal nerve stimulation. Aerosolized capsaicin solution (100 microg/ml) increased the time of braking from baseline levels of 8 ms to an average of 69 ms. At an exposure concentration of 100 ppm the malodorants induced only a minimal time of braking response (< 35 ms); the time of braking response in animals exposed to either malodorant plus capsaicin was 2.5-fold greater than in animals exposed to capsaicin alone (p < 0.01). In a subsequent experiment the time of breaking response to capsaicin was doubled (281 vs. 146 ms) by concomitant exposure to a no effect level of ethyl sulfide (11 ppm) and the modulation of capsaicin responsiveness was nearly abolished by inclusion of the adenosine antagonist theophylline in the aerosol formulation (time of braking 184 ms, p > or = 0.05 compared with capsaicin alone). These results suggest trigeminal nerve responsiveness is enhanced by exposure to malodorants through a theophylline-sensitive paracrine signaling pathway between olfactory and trigeminal nerves.
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Affiliation(s)
- Christopher R Desesa
- Toxicology Program, Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, Storrs, Connecticut 06269, USA
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19
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Burki NK, Sheatt M, Lee LY. Effects of airway anesthesia on dyspnea and ventilatory response to intravenous injection of adenosine in healthy human subjects. Pulm Pharmacol Ther 2008; 21:208-13. [DOI: 10.1016/j.pupt.2007.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Revised: 01/25/2007] [Accepted: 02/18/2007] [Indexed: 10/23/2022]
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20
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Hazari MS, Rowan WH, Winsett DW, Ledbetter AD, Haykal-Coates N, Watkinson WP, Costa DL. Potentiation of pulmonary reflex response to capsaicin 24h following whole-body acrolein exposure is mediated by TRPV1. Respir Physiol Neurobiol 2007; 160:160-71. [PMID: 17950047 DOI: 10.1016/j.resp.2007.09.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 09/06/2007] [Accepted: 09/11/2007] [Indexed: 11/26/2022]
Abstract
Pulmonary C-fibers are stimulated by irritant air pollutants producing apnea, bronchospasm, and decrease in HR. Chemoreflex responses resulting from C-fiber activation are sometimes mediated by TRPV1 and release of substance P. While acrolein has been shown to stimulate C-fibers, the persistence of acrolein effects and the role of C-fibers in these responses are unknown. These experiments were designed to determine the effects of whole-body acrolein exposure and pulmonary chemoreflex response post-acrolein. Rats were exposed to either air or 3 ppm acrolein for 3 h while ventilatory function and HR were measured; 1-day later response to capsaicin challenge was measured in anesthetized rats. Rats experienced apnea and decrease in HR upon exposure to acrolein, which was not affected by either TRPV1 antagonist or NK(1)R antagonist pretreatment. Twenty-four hours later, capsaicin caused apnea and bronchoconstriction in control rats, which was potentiated in rats exposed to acrolein. Pretreatment with TRPV1 antagonist or NK(1)R antagonist prevented potentiation of apneic response and bronchoconstriction 24h post-exposure. These data suggest that although potentiation of pulmonary chemoreflex response 24h post-acrolein is mediated by TRPV1 and release of substance P, cardiopulmonary inhibition during whole-body acrolein exposure is mediated through other mechanisms.
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Affiliation(s)
- Mehdi S Hazari
- Curriculum in Toxicology, University of North Carolina, Chapel Hill, NC 27599-7270, United States.
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21
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Hua X, Erikson CJ, Chason KD, Rosebrock CN, Deshpande DA, Penn RB, Tilley SL. Involvement of A1 adenosine receptors and neural pathways in adenosine-induced bronchoconstriction in mice. Am J Physiol Lung Cell Mol Physiol 2007; 293:L25-32. [PMID: 17468137 DOI: 10.1152/ajplung.00058.2007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High levels of adenosine can be measured from the lungs of asthmatics, and it is well recognized that aerosolized 5'AMP, the precursor of adenosine, elicits robust bronchoconstriction in patients with this disease. Characterization of mice with elevated adenosine levels secondary to the loss of adenosine deaminase (ADA) expression, the primary metabolic enzyme for adenosine, further support a role for this ubiquitous mediator in the pathogenesis of asthma. To begin to identify pathways by which adenosine can alter airway tone, we examined adenosine-induced bronchoconstriction in four mouse lines, each lacking one of the receptors for this nucleoside. We show, using direct measures of airway mechanics, that adenosine can increase airway resistance and that this increase in resistance is mediated by binding the A(1) receptor. Further examination of this response using pharmacologically, surgically, and genetically manipulated mice supports a model in which adenosine-induced bronchoconstriction occurs indirectly through the activation of sensory neurons.
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Affiliation(s)
- Xiaoyang Hua
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7219, USA
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22
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Fredholm BB. Adenosine, an endogenous distress signal, modulates tissue damage and repair. Cell Death Differ 2007; 14:1315-23. [PMID: 17396131 DOI: 10.1038/sj.cdd.4402132] [Citation(s) in RCA: 510] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Adenosine is formed inside cells or on their surface, mostly by breakdown of adenine nucleotides. The formation of adenosine increases in different conditions of stress and distress. Adenosine acts on four G-protein coupled receptors: two of them, A(1) and A(3), are primarily coupled to G(i) family G proteins; and two of them, A(2A) and A(2B), are mostly coupled to G(s) like G proteins. These receptors are antagonized by xanthines including caffeine. Via these receptors it affects many cells and organs, usually having a cytoprotective function. Joel Linden recently grouped these protective effects into four general modes of action: increased oxygen supply/demand ratio, preconditioning, anti-inflammatory effects and stimulation of angiogenesis. This review will briefly summarize what is known and what is not in this regard. It is argued that drugs targeting adenosine receptors might be useful adjuncts in many therapeutic approaches.
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Affiliation(s)
- B B Fredholm
- Department of Physiology and Pharmacology, Karolinska Insitutet, Stockholm, Sweden.
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23
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McGowan SE. Vitamin A deficiency increases airway resistance following C-fiber stimulation. Respir Physiol Neurobiol 2007; 157:281-9. [PMID: 17321224 PMCID: PMC5325692 DOI: 10.1016/j.resp.2007.01.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 01/13/2007] [Accepted: 01/22/2007] [Indexed: 11/26/2022]
Abstract
Vitamin A deficiency (VAD) remains an important problem in the developing world where environmental air pollution is increasing. Because the coincidence of these factors could increase the prevalence of asthma in these regions, airway reactivity to methacholine (MCh), capsaicin, and sulfur dioxide was studied in VAD rats. The impedance to a small volume oscillation was analyzed to determine airway resistance (R(aw)) and lung elastance (H). VAD rats demonstrated larger increases in R(aw) and H after the administration of methacholine, and in R(aw) after administration of capsaicin or sulfur dioxide. The muscarinic receptor-2 (M2R) selective antagonist AFDX-116 enhanced the effect of capsaicin in vitamin A sufficient (VAS) but not VAD rats and retinoic acid-administration partially restored this enhancement. These data indicate that diminished auto-inhibitory muscarinic receptor-2 function contributed to this increased airway responsiveness to pulmonary C-fiber stimulation in VAD rats. If children with VAD also have diminished M2R function, they may be more prone to develop asthma, particularly in the presence of environmental co-factors such as sulfur dioxide.
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Affiliation(s)
- S E McGowan
- Department of Veterans Affairs Research Service, University of Iowa Carver College of Medicine, IA 52242, USA.
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24
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Vaughan RP, Szewczyk MT, Lanosa MJ, Desesa CR, Gianutsos G, Morris JB. Adenosine sensory transduction pathways contribute to activation of the sensory irritation response to inspired irritant vapors. Toxicol Sci 2006; 93:411-21. [PMID: 16840565 DOI: 10.1093/toxsci/kfl061] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The molecular mechanisms through which sensory irritants stimulate nasal trigeminal nerves are poorly understood. The current study was aimed at evaluating the potential contribution of purinergic sensory transduction pathways in this process. Aerosols of 4-36 mM adenosine 5'-triphosphate (ATP) and adenosine both acted as sensory irritants. Large dose capsaicin pretreatment to induce degeneration of transient receptor potential vanilloid type-1 (TRPV1)-expressing C fibers greatly reduced, but did not abolish, the sensory irritation response to ATP aerosol and was without effect on the response to adenosine aerosol, indicating that ATP acts largely on capsaicin-sensitive (primarily C fibers) and adenosine acts on capsaicin-insensitive (primarily Adelta fibers) nerves. The response to adenosine was diminished by pretreatment with the broad-based adenosine receptor antagonist theophylline (20 mg/kg) and A1-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (0.1 mg/kg), providing evidence that adenosine stimulates capsaicin-insensitive nerves via the A1 receptor. The sensory irritation responses to 275 ppm styrene and 110 ppm acetic acid vapors were significantly reduced by theophylline pretreatment suggesting a role for adenosine signaling pathways in activation of the sensory irritant response by these vapors. If sensory nerves are activated by mediators that are released from injured airway mucosal cells, then nasal sensory nerve activation may be a reflection of irritant-induced alterations in airway cell integrity.
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Affiliation(s)
- Ryan P Vaughan
- Toxicology Program, Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, Storrs, Connecticut 06269-3092, USA
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25
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Chuaychoo B, Lee MG, Kollarik M, Pullmann R, Undem BJ. Evidence for both adenosine A1 and A2A receptors activating single vagal sensory C-fibres in guinea pig lungs. J Physiol 2006; 575:481-90. [PMID: 16793905 PMCID: PMC1819455 DOI: 10.1113/jphysiol.2006.109371] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We addressed the hypothesis that single vagal afferent C-fibres can be stimulated via either the adenosine A1 or A2A receptor subtypes. The effect of adenosine on the nerve terminals of vagal sensory nerve subtypes was evaluated in an ex vivo perfused guinea pig lung preparation using extracellular recording techniques. Adenosine (10 microm) consistently evoked action potential discharge in lung C-fibre terminals arising from the nodose ganglia, but failed to evoke action potential discharge in most jugular ganglion C-fibres. Adenosine also failed to activate stretch-sensitive nodose A-fibres in the lungs. The selective A1 antagonist DPCPX (0.1 microm) or the selective A2A antagonist SCH 58261 (0.1 microm) partially inhibited the nodose C-fibre activation by adenosine, and the combination of both antagonists almost completely inhibited the response. The adenosine-induced action potential discharge in nodose C-fibres was mimicked by either the selective A1 agonist CCPA (1 microm) or the selective A2A agonist CGS 21680 (1 microm). Single cell PCR techniques revealed that adenosine A1 and A2A receptor mRNA was expressed in individual nodose neurons retrogradely labelled from the lungs. The gramicidin-perforated patch clamp technique on neurons retrogradely labelled from the lungs was employed to study the functional consequence of adenosine receptor agonists directly on neuronal membrane properties. Both the selective A1 agonist CCPA (1 microm) and the selective A2A agonist CGS 21680 (1 microm) depolarized the airway-specific, capsaicin-sensitive, nodose neurons to action potential threshold. The data support the hypothesis that adenosine selectively depolarizes vagal nodose C-fibre terminals in the lungs to action potential threshold, by stimulation of both adenosine A1 and A2A receptor subtypes located in the neuronal membrane.
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Affiliation(s)
- Benjamas Chuaychoo
- Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
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26
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Lee LY, Lin RL, Ho CY, Gu Q, Hong JL. Are there "CO2 sensors" in the lung? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 580:281-92; discussion 351-9. [PMID: 16683733 DOI: 10.1007/0-387-31311-7_44] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Affiliation(s)
- L Y Lee
- Department of Physiology, University of Kentucky, Lexington, Kentucky 40536, USA
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27
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Lin RL, Gu Q, Lin YS, Lee LY. Stimulatory effect of CO2 on vagal bronchopulmonary C-fiber afferents during airway inflammation. J Appl Physiol (1985) 2005; 99:1704-11. [PMID: 15994240 PMCID: PMC1533319 DOI: 10.1152/japplphysiol.00532.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study investigated 1) whether pulmonary C fibers are activated by a transient increase in the CO2 concentration of alveolar gas; and 2) if the CO2 sensitivity of these afferents is altered during airway inflammation. Single-unit pulmonary C-fiber activity was recorded in anesthetized, open-chest rats. Transient alveolar hypercapnia (HPC) was induced by administering a CO2-enriched gas mixture (25-30% CO2, 21% O2, balance N2) for five to eight breaths, which increased alveolar CO2 concentration progressively to near or above 13% for 3-5 s and lowered the arterial pH transiently to 7.10 +/- 0.05. Our results showed the following. 1) HPC evoked only a mild stimulation in a small fraction (4/47) of pulmonary C fibers, and there was no significant change in fiber activity (change in fiber activity = 0.22 +/- 0.16 imp/s; P > 0.1, n = 47). 2) In sharp contrast, after airway exposure to poly-L-lysine, a cationic protein known to induce mucosal injury, the same challenge of transient HPC activated 87.5% of the pulmonary C fibers tested and evoked a distinct stimulatory effect on these afferents (change in fiber activity = 6.59 +/- 1.78 imp/s; P < 0. 01, n = 8). 3) Similar potentiation of the C-fiber response to HPC was also observed after acute exposure to ozone (n = 6) and during a constant infusion of inflammatory mediators such as adenosine (n = 15) or prostaglandin E2 (n = 12). 4) The enhanced C-fiber sensitivity to CO2 after poly-L-lysine was completely abrogated by infusion of NaHCO3 (1.82 mmol.kg(-1).min(-1)) that prevented the reduction in pH during HPC (n = 6). In conclusion, only a small percentage (<10%) of the bronchopulmonary C fibers exhibit CO2 sensitivity under control conditions, but alveolar HPC exerts a consistent and pronounced stimulatory effect on the C-fiber endings during airway inflammation. This effect of CO2 is probably mediated through the action of hydrogen ions.
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Affiliation(s)
| | | | | | - Lu-Yuan Lee
- Address for correspondence: Lu-Yuan Lee, Ph.D., Department of Physiology, University of Kentucky Medical Center, 800 Rose Street Lexington, KY 40536-0298, U.S.A. Telephone: (859) 323-6339, Fax: (859) 323-1070, E-mail:
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