title: Benzodiazepine augmented γ-amino-butyric acid signaling increases mortality from pneumonia in mice.
abstract: OBJECTIVE
  Benzodiazepines are used for treating anxiety, epilepsy, muscle spasm, alcohol withdrawal, palliation, insomnia, and sedation as they allosterically modulate γ-amino-butyric acid type A (GABAA) receptors. Despite widespread use, the importance and mechanism of their immune side-effects are poorly understood. Herein we sought to elucidate the impact and mechanism of benzodiazepine-induced susceptibility to infection at anxiolytic doses in mice.
  
  
  METHODS
  Animal randomized controlled trial.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Adult female C57BL/6 and BALB/c mice.
  
  
  METHODS
  The effect of a subsedative, anxiolytic dose of diazepam (2 mg kg intraperitoneal) was investigated in a murine Streptococcus pneumoniae pneumonia model.
  
  
  RESULTS
  Mortality, bacterial and cytokine load, cell recruitment, and intracellular pH were measured. Diazepam treatment did not affect immune homeostasis in the lung. However, diazepam increased mortality and bacterial load from S. pneumoniae pneumonia. The increases in mortality and bacterial load were reversed by a GABAA antagonist, bicuculline, indicating dependence on GABAA receptor signaling. While cell recruitment was unaltered by diazepam, the cytokine response to infection was affected, suggesting that local responses to the pathogen were perturbed. Macrophage and monocytes expressed benzodiazepine sensitive (α1-γ2) GABAA receptors. Interestingly macrophage GABAA receptor expression was regulated by bacterial toll-like receptor agonists and cytokines indicating an endogenous role in the immune response. Functionally diazepam appeared to counteract the endogenous down-regulation of GABAA signaling during infection. Consistent with augmented GABAA signaling, diazepam provoked intracellular acidosis in macrophage, leading to impaired cytokine production, bacterial phagocytosis and killing. In contrast, selective benzodiazepines that do not target the α1 GABAA subunit did not affect macrophage function ex vivo or increase susceptibility to pneumonia in vivo.
  
  
  CONCLUSIONS
  Our data highlight the regulation of macrophage function by GABAA receptor signaling and the potential harm of benzodiazepine exposure during pneumonia. Therapeutically, selective drugs may improve the safety profile of benzodiazepines.
authors.affiliation: Department of Leukocyte Biology, Imperial College, London, UK. robert.sanders@imperial.ac.uk
authors.forename: Robert D
authors.initials: RD
authors.lastname: Sanders
authors.forename: Alexandra
authors.initials: A
authors.lastname: Godlee
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Fujimori
authors.forename: John
authors.initials: J
authors.lastname: Goulding
authors.forename: Gang
authors.initials: G
authors.lastname: Xin
authors.forename: Samira
authors.initials: S
authors.lastname: Salek-Ardakani
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Snelgrove
authors.forename: Daqing
authors.initials: D
authors.lastname: Ma
authors.forename: Mervyn
authors.initials: M
authors.lastname: Maze
authors.forename: Tracy
authors.initials: T
authors.lastname: Hussell
mesh_terms: D000818:Animals; D001569:Benzodiazepines / Q000494:pharmacology*; D001640:Bicuculline / Q000494:pharmacology; D016207:Cytokines / Q000187:drug effects / Q000378:metabolism; D005260:Female; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018410:Pneumonia, Bacterial / Q000401:mortality / Q000503:physiopathology*; D011897:Random Allocation; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D016207:Cytokines; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline