Inhibition of Alveolar Macrophage Pyroptosis Reduces Lipopolysaccharide-induced Acute Lung Injury in Mice

Background：Pyroptosis is the term for caspase-l-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-l-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-β （IL-lβ） 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.

Expert consensus on clinical standardized application of high-flow nasal cannula oxygen therapy in adults

High-flow nasal cannula oxygen therapy(HFNC)is a novel respiratory support technology and has been extensively applied in clinics in recent years.This therapeutic equipment mainly includes an air-oxygen blender,an active humidifier,a high-flow nasal cannula,and a connecting inspiratory circuit.It provides patients a humidified high-flow gas(8-80 L/min)with relatively stable oxygen concentration(21-100%),temperature(31-37℃)and performs oxygen therapy via a nasal cannula,which is very comfortable.