# Gut microbiota dysbiosis exacerbates acute pancreatitis via Escherichia coli-driven neutrophil heterogeneity and NETosis

## TL;DR

Gut bacteria imbalance worsens acute pancreatitis by increasing harmful E. coli and changing immune cells, leading to more severe inflammation.

## Contribution

Identifies Escherichia coli as a key driver of acute pancreatitis severity through neutrophil heterogeneity and NETosis.

## Key findings

- Germ-free mice showed reduced pancreatic injury and NET formation compared to SPF mice.
- E. coli promotes pro-inflammatory neutrophil subpopulations and activates NETosis-related pathways.
- Fecal E. coli levels in AP patients correlate with increased cell-free DNA, a marker of NETosis.

## Abstract

Gut microbiota dysbiosis contributes to acute pancreatitis (AP) severity, but the specific microbes and mechanisms remain unclear. In this study, we employed both germ-free (GF) and specific-pathogen-free (SPF) murine models of AP to investigate the role of the intestinal microbiota. Our findings demonstrate that GF mice exhibited markedly attenuated pancreatic injury, inflammatory cell infiltration, and neutrophil extracellular traps (NETs) formation. Through fecal microbiota transplantation (FMT) from AP patients, differential antibiotic modulation, and single-bacterial colonization experiments, we identified Gram-negative bacteria, particularly Escherichia coli (E. coli), as critical microbial drivers of disease exacerbation. Single-cell RNA sequencing revealed that microbiota dysbiosis profoundly reprogrammed both local pancreatic and systemic immune landscapes. Specifically, dysbiosis promoted emergency granulopoiesis in the bone marrow, enhanced neutrophil mobilization and activation, and facilitated the expansion of pro-inflammatory neutrophil subpopulations (Neutrophils_2 and Neutrophils_3). These subsets exhibited upregulated signaling through NETosis-associated pathways, including TLR, NF-κB, and IL-17 axes. Conversely, in GF conditions, we observed a predominance of an anti-inflammatory neutrophil subset (Neutrophils_4), characterized by the expression of tissue repair-associated genes such as Reg1 and Reg2. Shotgun metagenomic profiling of fecal samples from patients with AP revealed an enrichment of E. coli during the acute phase, positively correlating with circulating cell-free DNA, a marker of NETosis. Together, these insights suggest that gut microbiota dysbiosis, notably increased E. coli abundance, may aggravate AP by reshaping immunity and promoting aberrant NETs formation, supporting microbiota or NETs targeted therapies.

Summary diagram of gut microbiota dysbiosis–driven E. coli expansion reprograms systemic and pancreatic immunity to promote aberrant NETosis and aggravate acute pancreatitis.