# Gut microbiota dysbiosis aggravates sepsis-induced lung injury by promoting neutrophil extracellular traps and suppressing host integrin defense

## TL;DR

Gut microbiota imbalance worsens sepsis-related lung damage by increasing neutrophil traps and weakening lung cell barriers, but fecal transplants and integrin support can help.

## Contribution

Identifies a new gut microbiota-NET-integrin pathway in sepsis-induced lung injury and validates FMT and integrin modulation as therapeutic strategies.

## Key findings

- Fecal microbiota transplantation reduced neutrophil extracellular traps by 58% and restored lung endothelial barrier integrity.
- Integrin ITGAM/ITGB2 overexpression reversed endothelial permeability and inflammation caused by neutrophil extracellular traps.
- Microbial dysbiosis promotes NET-mediated suppression of integrins, leading to pulmonary endothelial barrier failure in sepsis.

## Abstract

The gut-lung axis is central to systemic inflammatory regulation, but the mechanisms by which gut microbiota dysbiosis aggravates sepsis-induced acute lung injury (ALI), particularly through neutrophil extracellular traps (NETs) and integrin signaling, remain unclear. Given the critical need for microbiota-based therapeutic strategies, this study investigates the mechanistic link between gut microbiota, NET formation, and pulmonary endothelial barrier dysfunction.

Using a cecal ligation and puncture (CLP) sepsis model, control, sepsis, and fecal microbiota transplantation (FMT) groups were compared. Lung injury was assessed via histopathology, wet/dry weight ratios, and bronchoalveolar lavage fluid (BALF) analysis. High-throughput RNA sequencing (GO/KEGG/PPI) identified key targets, validated by lentiviral knockdown/overexpression of ITGAM and ITGB2 in vivo and in vitro [mouse pulmonary microvascular endothelial cells (MPMECs) and neutrophil co-cultures]. NETs were quantified by MPO-DNA ELISA and immunofluorescence.

CLP-induced sepsis triggered severe pulmonary edema, neutrophil infiltration, and NET accumulation, alongside downregulation of ITGAM/ITGB2 and tight junction proteins (β-catenin/ZO-1/VE-cadherin). FMT reduced NETs by 58% (p < 0.001) and restored endothelial barrier integrity. Transcriptomics revealed ITGAM/ITGB2 as central nodes in neutrophil activation and integrin pathways. In vitro, NET exposure increased endothelial permeability (3.1-fold FITC-dextran flux, p < 0.01) and IL-6/TNF-α secretion, while ITGAM/ITGB2 overexpression reversed these effects. Conversely, integrin silencing abolished FMT’s protection, exacerbating ALI.

We unveil a novel gut microbiota-NET-integrin axis in sepsis-induced ALI, where microbial dysbiosis promotes NET-mediated suppression of ITGAM/ITGB2, leading to endothelial barrier failure. Our findings position FMT and integrin modulation as promising strategies to mitigate pulmonary vascular dysfunction, advancing the therapeutic potential of microbiota-targeted interventions in critical care.

Schematic representation of the molecular mechanism by which gut microbiota dysbiosis triggers the formation of NETs, leading to the downregulation of ITGAM and ITGB2, disruption of pulmonary endothelial barrier integrity, and exacerbation of sepsis-induced ALI.Diagram illustrating the process of sepsis-associated acute lung injury. A mouse represents the condition, linked to intestinal dysbacteriosis, shown with gut bacteria. This leads to neutrophil extracellular traps (NETs). Vascular permeability and disruption of the pulmonary endothelial barrier occur, with endothelial cell loss depicted. Integrins ITGAM and ITGB2 on pulmonary microvascular endothelial cells are shown in relation to this process.

Schematic representation of the molecular mechanism by which gut microbiota dysbiosis triggers the formation of NETs, leading to the downregulation of ITGAM and ITGB2, disruption of pulmonary endothelial barrier integrity, and exacerbation of sepsis-induced ALI.