Fabien Beaufils1, Pauline Esteves2, Raphael Enaud1, Ophélie Germande2, Alexis Celle2, Roger Marthan1, Thomas Trian2, Michael Fayon1, Patrick Berger3. 1. Univ-Bordeaux, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, CIC 1401, F-33000 Bordeaux, France; INSERM, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, CIC 1401, F-33000 Bordeaux, France; CHU de Bordeaux, Service d'exploration fonctionnelle respiratoire, Service de Pédiatrie médicale, Bordeaux, France. 2. Univ-Bordeaux, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, CIC 1401, F-33000 Bordeaux, France; INSERM, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, CIC 1401, F-33000 Bordeaux, France. 3. Univ-Bordeaux, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, CIC 1401, F-33000 Bordeaux, France; INSERM, Centre de Recherche Cardio-thoracique de Bordeaux, U1045, CIC 1401, F-33000 Bordeaux, France; CHU de Bordeaux, Service d'exploration fonctionnelle respiratoire, Service de Pédiatrie médicale, Bordeaux, France. Electronic address: patrick.berger@u-bordeaux.fr.
Abstract
BACKGROUND: Bronchial remodeling is a key feature of asthma already present in preschool wheezers. Moreover, bronchial smooth muscle (BSM) remodeling at preschool age is predictive of asthma at school age. However, the mechanism responsible for BSM remodeling in preschool wheezers remains totally unknown. By contrast, in adult asthma, BSM remodeling has been associated to an increase in BSM cell proliferation related to increased mitochondrial mass and biogenesis triggered by an altered calcium homeostasis. Indeed, BSM cell proliferation was decreased in vitro by the calcium channel blocker gallopamil. OBJECTIVE: To investigate the mechanisms involved in BSM cell proliferation in severe preschool wheezers, with special attention to the role of mitochondria and calcium signaling. METHODS: Bronchial tissue obtained from 12 non-wheezing preschool controls and 10 severe preschool wheezers, was used to measure BSM mass and establish primary BSM cell cultures. BSM cell proliferation was assessed by manual counting and flow cytometry, ATP content by bioluminescence, mitochondrial respiration either by Seahorse and Oroboros, mitochondrial mass and biogenesis by immunoblotting, and calcium response to carbachol by confocal microscopy. The effect of gallopamil was also evaluated. RESULTS: BSM mass, cell proliferation, ATP content, mitochondrial respiration, mass and biogenesis, and calcium response were all increased in severe preschool wheezers compared to those of controls. Gallopamil significantly decreased BSM mitochondrial biogenesis and mass, and cell proliferation. CONCLUSION: Mitochondria are a key player in BSM cell proliferation in severe preschool wheezers and could represent a potential target to treat BSM remodeling at an early stage of the disease.
BACKGROUND: Bronchial remodeling is a key feature of asthma already present in preschool wheezers. Moreover, bronchial smooth muscle (BSM) remodeling at preschool age is predictive of asthma at school age. However, the mechanism responsible for BSM remodeling in preschool wheezers remains totally unknown. By contrast, in adult asthma, BSM remodeling has been associated to an increase in BSM cell proliferation related to increased mitochondrial mass and biogenesis triggered by an altered calcium homeostasis. Indeed, BSM cell proliferation was decreased in vitro by the calcium channel blocker gallopamil. OBJECTIVE: To investigate the mechanisms involved in BSM cell proliferation in severe preschool wheezers, with special attention to the role of mitochondria and calcium signaling. METHODS: Bronchial tissue obtained from 12 non-wheezing preschool controls and 10 severe preschool wheezers, was used to measure BSM mass and establish primary BSM cell cultures. BSM cell proliferation was assessed by manual counting and flow cytometry, ATP content by bioluminescence, mitochondrial respiration either by Seahorse and Oroboros, mitochondrial mass and biogenesis by immunoblotting, and calcium response to carbachol by confocal microscopy. The effect of gallopamil was also evaluated. RESULTS: BSM mass, cell proliferation, ATP content, mitochondrial respiration, mass and biogenesis, and calcium response were all increased in severe preschool wheezers compared to those of controls. Gallopamil significantly decreased BSM mitochondrial biogenesis and mass, and cell proliferation. CONCLUSION: Mitochondria are a key player in BSM cell proliferation in severe preschool wheezers and could represent a potential target to treat BSM remodeling at an early stage of the disease.