1
|
Bossé Y. The airway smooth muscle and the pipe dream of better bronchodilators. Can J Physiol Pharmacol 2024. [PMID: 39361971 DOI: 10.1139/cjpp-2024-0277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2024]
Abstract
Research on airway smooth muscle has traditionally focused on its putative detrimental role in asthma, emphasizing on how its shortening narrows the airway lumen, without much consideration about its potential role in subserving the function of the entire respiratory system. New experimental evidence on mice suggests that not only the smooth muscle is required to sustain life postnatally, but its stiffening effect on the lung tissue also protects against excessive airway narrowing and, most importantly, against small airway narrowing heterogeneity and closure. These results suggest that the smooth muscle plays an vital role in the lung periphery, essentially safeguarding alveolar ventilation by preventing small airway closure. These results also shed light on perplexing clinical observations, such as the long-standing doubts about the safety of bronchodilators. Since there seems to be an optimal level of smooth muscle contraction, at least in small airways, the therapeutic goal of maximizing the relaxation of the smooth muscle in asthma needs to be revisited. A bronchodilator with an excessive potency for inhibiting smooth muscle contraction, and that is still potent at concentrations reaching the lung periphery, may foster airway closure and air trapping, resulting in no net gain or even a decline in lung function.
Collapse
Affiliation(s)
- Ynuk Bossé
- Institut Universitaire de Cardiologie et de Pneumologie de Québec (IUCPQ) - Université Laval, Québec, QC, Canada
| |
Collapse
|
2
|
Dugger KJ, Chrisman T, Sayner SL, Chastain P, Watson K, Estes R. Beta-2 adrenergic receptors increase TREG cell suppression in an OVA-induced allergic asthma mouse model when mice are moderate aerobically exercised. BMC Immunol 2018; 19:9. [PMID: 29452585 PMCID: PMC5816563 DOI: 10.1186/s12865-018-0244-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 01/22/2018] [Indexed: 02/06/2023] Open
Abstract
Background The potency of T regulatory (TREG) cells to inhibit T helper (Th)-driven immune cell responses has been linked to increased intracellular cyclic-AMP (cAMP) levels of TREG cells. In an ovalbumin (OVA)-driven allergic asthma mouse model, moderate aerobic exercise increases TREG cell function in a contact-dependent manner that leads to a significant reduction in chronic inflammation and restoration of lung function. However, the mechanism, whereby exercise increases TREG function, remains unknown and was the focus of these investigations. Exercise can communicate with TREG cells by their expression of β2-adrenergic receptors (β2-AR). Activation of these receptors results in an increase in intracellular levels of cyclic-AMP, potentially creating a potent inhibitor of Th cell responses. Results For the allergic asthma model, female wildtype BALB/c mice were challenged with OVA, and exercised (13.5 m/min for 45 min) 3×/week for 4 weeks. TREG cells were isolated from all mouse asthma/exercise groups, including β2-AR−/− mice, to test suppressive function and intracellular cAMP levels. In these studies, cAMP levels were increased in TREG cells isolated from exercised mice. When β2-AR expression was absent on TREG cells, cAMP levels were significantly decreased. Correlatively, their suppressive function was compromised. Next, TREG cells from all mouse groups were tested for suppressive function after treatment with either a pharmaceutical β2-adrenergic agonist or an effector-specific cAMP analogue. These experiments showed TREG cell function was increased when treated with either a β2-adrenergic agonist or effector-specific cAMP analogue. Finally, female wildtype BALB/c mice were antibody-depleted of CD25+CD4+ TREG cells (anti-CD25). Twenty-four hours after TREG depletion, either β2-AR−/− or wildtype TREG cells were adoptively transferred. Recipient mice underwent the asthma/exercise protocols. β2-AR−/− TREG cells isolated from these mice showed no increase in TREG function in response to moderate aerobic exercise. Conclusion These studies offer a novel role for β2-AR in regulating cAMP intracellular levels that can modify suppressive function in TREG cells.
Collapse
Affiliation(s)
- Kari J Dugger
- Department of Clinical and Diagnostic Sciences, Biomedical Sciences, School of Health Professions, University of Alabama at Birmingham, 1716 9th Ave S, SHPB 472, Birmingham, 35294, AL, USA.
| | - Taylor Chrisman
- Department of Biomedical Sciences, College of Allied Health; University of South Alabama, 5721 USA Dr. N, HAHN 4021, Mobile, 36688, AL, USA
| | - Sarah L Sayner
- Department of Physiology and Cell Biology, Center for Lung Biology, College of Medicine, University of South Alabama, Mobile, 36688, AL, USA
| | - Parker Chastain
- Department of Biomedical Sciences, College of Allied Health; University of South Alabama, 5721 USA Dr. N, HAHN 4021, Mobile, 36688, AL, USA
| | - Kacie Watson
- Department of Biomedical Sciences, College of Allied Health; University of South Alabama, 5721 USA Dr. N, HAHN 4021, Mobile, 36688, AL, USA
| | - Robert Estes
- Department of Clinical and Diagnostic Sciences, Biomedical Sciences, School of Health Professions, University of Alabama at Birmingham, 1716 9th Ave S, SHPB 472, Birmingham, 35294, AL, USA
| |
Collapse
|