Intestinal fibrosis, a hallmark complication of Crohn’s disease (CD), frequently progresses to stricture formation and surgical intervention. Fibroblast metabolic reprogramming is important in organ fibrosis. However, its role in intestinal fibrogenesis of CD remains elusive.
We aim to explore the metabolic reprogramming of fibroblasts and its upstream regulators during intestinal fibrosis of CD.
We performed metabolome, single-cell RNA sequencing and spatial transcriptome on paired mucosal and submucosal tissue from the strictured and adjacent non-strictured intestinal segments. The candidate metabolite and metabolic enzymes were verified in primary human intestinal myofibroblasts (HIMFs) and dextran sulfate sodium-induced intestinal fibrotic mice. Next, we identified fibrosis-associated circPLCE1 to regulate the pentose phosphate pathway (PPP) using the circRNA transcriptome. Finally, we studied the functions and mechanisms of circPLCE1 using metabolome, transcriptome, metabolic flux, seahorse assay and RNA pull-down assay in HIMFs and fibroblast-specific circPLCE1 knockdown mice.
Multilayer integrated analysis identified activation of PPP in fibroblasts during intestinal fibrosis of CD. Specifically, xylulokinase (XYLB)-generated xylulose-5-phosphate (Xu5P) promoted extracellular matrix synthesis by epigenetic upregulation of collagen transcription. Moreover, downregulation of circPLCE1 in fibroblasts activated PPP, resulting in increased glycolysis, nicotinamide adenine dinucleotide phosphate production and aggravated intestinal fibrosis in vitro and in vivo. Mechanistically, circPLCE1 directly bound the domain-I of XYLB and competitively inhibited its enzymatic activity. Decreased circPLCE1 restored XYLB activity and accumulation of Xu5P in intestinal fibrosis.
Our findings delineate a circPLCE1/XYLB/Xu5P axis in fibroblasts which orchestrates PPP and fibrogenesis, unveiling a novel therapeutic target for intestinal fibrosis of CD.
Parasutterella excrementihominis (P. excrementihominis), a Betaproteobacteria species enriched in ulcerative colitis (UC) patients, is implicated in chronic inflammation. However, its mechanistic role in UC progression and colitis-associated colorectal cancer (CAC) remains unclear.
This study investigates the pathogenic role of P. excrementihominis in UC and CAC, focusing on its induction of neutrophil extracellular traps (NETs) and underlying mechanisms.
Clinical stool samples from UC patients and healthy controls were analysed for P. excrementihominis abundance. Murine models of dextran sulphate sodium (DSS)-induced colitis and azoxymethane/DSS-induced CAC were used to evaluate bacterial pathogenicity. RNA sequencing and metabolomic analyses were conducted on germ-free mice with monocolonisation, and in vitro cell experiments were carried out to elucidate the role of bacterial metabolites in NETosis.
P. excrementihominis was significantly enriched in UC patients and exacerbated colitis and CAC in mice by expanding colonic neutrophils and NETs formation. Metabolomic profiling revealed that P. excrementihominis enhances the host’s carbohydrate metabolic capacity, leading to increased production of succinic acid (Suc) and 6-hydroxyhexanoic acid (6-HHA). These metabolites activated gasdermin D (GSDMD)-dependent NETosis in lipopolysaccharide-primed neutrophils through the succinate receptor 1/G protein-coupled receptor 84 signalling pathway. Conversely, neutrophil-specific GSDMD deletion attenuated metabolite-driven tumourigenesis.
Our findings identify P. excrementihominis as a critical microbial driver of UC and CAC pathogenesis. This bacterium significantly accelerates disease progression by producing specific metabolites (Suc and 6-HHA) that induce pathogenic NETosis. Targeting this bacterium or its metabolic axis offers novel therapeutic strategies for inflammation-driven colorectal carcinogenesis.