title: Inhibition of Alveolar Macrophage Pyroptosis Reduces Lipopolysaccharide-induced Acute Lung Injury in Mice.
abstract: BACKGROUND
  Pyroptosis is the term for caspase-1-dependent cell death associated with pro-inflammatory cytokines. The role of alveolar macrophage (AM) pyroptosis in the pathogenesis of the acute lung injury and acute respiratory distress syndrome (ALI/ARDS) remains unclear.
  
  
  METHODS
  C57BL/6 wild-type mice were assigned to sham, lipopolysaccharide (LPS) + vehicle, LPS + acetyl-tyrosyl-valyl- alanyl-aspartyl-chloromethylketone (Ac-YVAD-CMK) and LPS + Z-Asp-Glu-Val-Asp-fluoromethylketone groups. Mice were given intraperitoneal (IP) injections of LPS. Drugs were IP injected 1 h before LPS administration. Mice were sacrificed 16 h after LPS administration, and AMs were isolated. Western blot analysis for active caspase-1 and cleaved caspase-3, evaluation of lung injury and a cytokine release analysis were performed. AMs were treated with LPS and adenosine triphosphate (ATP); caspase-1-dependent cell death was evaluated using flow cytometry; the apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) pyroptosomes were examined by immunofluorescence.
  
  
  RESULTS
  The expression of activated caspase-1 in AMs was enhanced following LPS challenge compared with the sham group. In the ex vivo study, the caspase-1/propidium iodide-positive cells, caspase-1 specks and ASC pyroptosomes were up-regulated in AMs following LPS/ATP stimulation. The specific caspase-1 inhibitor Ac-YVAD-CMK inhibited the activation of caspase-1 and pyroptotic cell death. Ac-YVAD-CMK also reduced the lung injury, pulmonary edema and total protein in bronchoalveolar lavage fluid (BALF). In addition, Ac-YVAD-CMK significantly inhibited interleukin-α2 (IL-1α2) release both in serum and BALF and reduced the levels of IL-18, tumor necrosis factor-α± (TNF-α±), High Mobility Group Box 1 (HMGB1) in BALF during LPS-induced ALI/ARDS.
  
  
  CONCLUSIONS
  This study reported AM pyroptosis during LPS-induced ALI/ARDS in mice and has demonstrated that Ac-YVAD-CMK can prevent AM-induced pyroptosis and lung injury. These preliminary findings may form the basis for further studies to evaluate this pathway as a target for prevention or reduction of ALI/ARDS.
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Wu
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.
authors.forename: Pin-Hua
authors.initials: PH
authors.lastname: Pan
authors.forename: Ben
authors.initials: B
authors.lastname: Liu
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Su
authors.forename: Le-Meng
authors.initials: LM
authors.lastname: Zhang
authors.forename: Hong-Yi
authors.initials: HY
authors.lastname: Tan
authors.forename: Zu
authors.initials: Z
authors.lastname: Cao
authors.forename: Zuo-Ren
authors.initials: ZR
authors.lastname: Zhou
authors.forename: Hai-Tao
authors.initials: HT
authors.lastname: Li
authors.forename: Hao-Si
authors.initials: HS
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Huang
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Li
mesh_terms: D055371:Acute Lung Injury / Q000139:chemically induced* / Q000517:prevention & control*; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D008070:Lipopolysaccharides / Q000633:toxicity*; D016676:Macrophages, Alveolar / Q000187:drug effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000494:pharmacology; D000069292:Pyroptosis / Q000187:drug effects*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D008070:Lipopolysaccharides; C098738:N-acetyl-tyrosyl-valyl-alanyl-aspartyl chloromethyl ketone; D009842:Oligopeptides; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone