Mechanical Ventilation Exacerbates Poly (I:C) Induced Acute Lung Injury: Central Role for Caspase-11 and Gut-Lung Axis.

Shuqing Jin,Timothy R Billiar,Li-Ming Zhang,Bruce R Pitt,Wenbo Li,Xin Lv,Quan Li,Meihong Deng,Chenxuan Yang,Hong Liao,Xibing Ding

doi:10.3389/fimmu.2021.693874

Abstract

BackgroundThe mechanisms by which moderate tidal volume ventilation (MTV) exacerbates preexisting lung injury are unclear. We hypothesized that systemic endotoxemia via the gut-lung axis would lead to non-canonical and canonical inflammasome activation and pyroptosis in a two-hit model involving polyinosinic-polycytidylic acid (Poly(I:C)), a synthetic analog of dsRNA and MTV and that this would associate with acute lung injury (ALI).MethodsAnesthetized mice were administered Poly(I:C) intratracheally and then 6 h later, they were mechanically ventilated for 4 h with otherwise non-injurious MTV (10ml/kg). Changes in intestinal and alveolar capillary permeability were measured. Further documentation of ALI was assessed by evans blue albumin permeability, protein and IL-1 family concentration in bronchoalveolar lavage fluid (BALF) or plasma, and histopathology in cohorts of wildtype (WT), whole body genetically ablated caspase-11 (caspase-11-/-), caspase-1/caspase-11 double knockout (caspase-1/11-/-), gasdermin D (GSDMD)-/-, nucleotide-binding domain leucine-rich repeat-containing protein 3 (NLRP3)-/- and advanced glycosylation end product-specific receptor (RAGE) -/- mice.ResultsNon-injurious MTV exacerbated the mild lung injury associated with Poly(I:C) administration. This included the disruption of alveolar-capillary barrier and increased levels of interleukin (IL)-6, high mobility group proteins 1 (HMGB-1), IL-1β in BALF and IL-18 in plasma. Combined (Poly(I:C)-MTV) injury was associated with increase in gastrointestinal permeability and endotoxin in plasma and BALF. Poly(I:C)-MTV injury was sensitive to caspase-11 deletion with no further contribution of caspase-1 except for maturation and release of IL-18 (that itself was sensitive to deletion of NLRP3). Combined injury led to large increases in caspase-1 and caspase-11. Genetic ablation of GSDMD attenuated alveolar-capillary disruption and release of cytokines in combined injury model.ConclusionsThe previously noted exacerbation of mild Poly(I:C)-induced ALI by otherwise non-injurious MTV is associated with an increase in gut permeability resulting in systemic endotoxemia. The gut-lung axis resulted in activation of pulmonary non-canonical (cytosolic mediated caspase-11 activation) and canonical (caspase-1) inflammasome (NLRP3) mediated ALI in this two-hit model resulting in GSDMD sensitive alveolar capillary barrier disruption, pyroptosis (alveolar macrophages) and cytokine maturation and release (IL-1β; IL-18). Pharmacologic strategies aimed at disrupting communication between gut and lung, inhibition of inflammasomes or GSDMD in pyroptosis may be useful in ALI.

Highlights

Sepsis is the major underlying cause (~75%) of acute respiratory distress syndrome (ARDS) and this often follows the onset of pneumonia [1]
Caspase-1/11-/- mice, caspase-11-/- mice, toll like receptor-4 (TLR4)-/- mice, nucleotide-binding domain leucinerich repeat-containing protein 3 (NLRP3)-/- mice, gasdermin D (GSDMD)-/- mice, advanced glycosylation end product-specific receptor (RAGE)-/- mice were bred and maintained in the University of Pittsburgh animal facility according to NIH animal care guidelines and all procedures were performed according to University of Pittsburgh Animal Research Protocols
Disruption of the alveolar-capillary barrier (Figures 1 and 2) in this two-hit model, as previously reported by Chun et al [21] and us [20], is a central feature of acute lung injury (ALI) and provides a useful preclinical framework in identifying pathways that underscore the major contribution of sepsis to ARDS

Summary

Introduction

Sepsis is the major underlying cause (~75%) of acute respiratory distress syndrome (ARDS) and this often follows the onset of pneumonia [1]. ARDS occurs in a large number of patients from infections outside the lung and the mechanisms underlying the development of lung injury from remote sources are multifactorial and poorly understood [2]. Both direct (e.g. pneumonia) and indirect (extrapulmonary) sepsis routinely require mechanical ventilation and it is well known that such lifesaving therapy can exacerbate underlying lung injury in an iatrogenic pathology of ventilator induced lung injury [VILI; [3]]. We hypothesized that systemic endotoxemia via the gut-lung axis would lead to non-canonical and canonical inflammasome activation and pyroptosis in a two-hit model involving polyinosinicpolycytidylic acid (Poly(I:C)), a synthetic analog of dsRNA and MTV and that this would associate with acute lung injury (ALI)

Methods

Results

Conclusion