title: The α7 nicotinic acetylcholine receptor agonist GTS-21 improves bacterial clearance in mice by restoring hyperoxia-compromised macrophage function.
abstract: Mechanical ventilation with supraphysiological concentrations of oxygen (hyperoxia) is routinely used to treat patients with respiratory distress. However, prolonged exposure to hyperoxia compromises the ability of the macrophage to phagocytose and clear bacteria. Previously, we showed that the exposure of mice to hyperoxia elicits the release of the nuclear protein high mobility group box-1 (HMGB1) into the airways. Extracellular HMGB1 impairs macrophage phagocytosis and increases the mortality of mice infected with Pseudomonas aeruginosa (PA). The aim of this study was to determine whether GTS-21 [3-(2,4 dimethoxybenzylidene)-anabaseine dihydrochloride], an α7 nicotinic acetylcholine receptor (α7nAChR) agonist, could inhibit hyperoxia-induced HMGB1 release into the airways, enhance macrophage function and improve bacterial clearance from the lungs in a mouse model of ventilator-associated pneumonia. GTS-21 (0.04, 0.4 and 4 mg/kg) or saline was systemically administered via intraperitoneal injection to mice that were exposed to hyperoxia (≥99% O2) and subsequently challenged with PA. We found that systemic administration of 4 mg/kg GTS-21 significantly increased bacterial clearance, decreased acute lung injury and decreased accumulation of airway HMGB1. To investigate the cellular mechanism of these observations, RAW 264.7 cells, a macrophagelike cell line, were incubated with different concentrations of GTS-21 in the presence of 95% O2. The phagocytic activity of macrophages was significantly increased by GTS-21 in a dose-dependent manner. In addition, hyperoxia-induced hyperacetylation of HMGB1 was significantly reduced in macrophages incubated with GTS-21. Furthermore, GTS-21 significantly inhibited the cytoplasmic translocation and release of HMGB1 from these macrophages. Our results indicate that GTS-21 is effective in improving bacterial clearance and reducing acute lung injury by enhancing macrophage function via inhibiting the release of nuclear HMGB1. Therefore, the α7nAChR represents a possible pharmacological target to improve the clinical outcome of patients on ventilators by augmenting host defense against bacterial infections.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America.
authors.forename: Ravikumar A
authors.initials: RA
authors.lastname: Sitapara
authors.affiliation: Medical Research Council Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Antoine
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America.
authors.forename: Lokesh
authors.initials: L
authors.lastname: Sharma
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America.
authors.forename: Vivek S
authors.initials: VS
authors.lastname: Patel
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Ashby
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America.
authors.forename: Samir
authors.initials: S
authors.lastname: Gorasiya
authors.affiliation: Laboratory of Biomedical Science, Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, New York, United States of America.
authors.forename: Huan
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America.
authors.forename: Michelle
authors.initials: M
authors.lastname: Zur
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, New York, United States of America Center for Inflammation and Immunology, Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, New York, United States of America Center for Heart and Lung Research, Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, New York, United States of America.
authors.forename: Lin L
authors.initials: LL
authors.lastname: Mantell
mesh_terms: D000818:Animals; D058491:Bacterial Load; D001597:Benzylidene Compounds / Q000494:pharmacology*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002460:Cell Line; D024243:HMGB1 Protein / Q000378:metabolism; D018496:Hyperoxia / Q000378:metabolism*; D008168:Lung / Q000378:metabolism / Q000382:microbiology; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D008297:Male; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D018722:Nicotinic Agonists / Q000494:pharmacology*; D010587:Phagocytosis / Q000187:drug effects; D053717:Pneumonia, Ventilator-Associated / Q000378:metabolism* / Q000382:microbiology; D011552:Pseudomonas Infections / Q000378:metabolism / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification; D011725:Pyridines / Q000494:pharmacology*; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000819:agonists* / Q000378:metabolism
chemical_list: D001597:Benzylidene Compounds; D024243:HMGB1 Protein; C582808:HMGB1 protein, mouse; D016328:NF-kappa B; D018722:Nicotinic Agonists; D011725:Pyridines; D064569:alpha7 Nicotinic Acetylcholine Receptor; C088936:3-(2,4-dimethoxybenzylidene)anabaseine