Introduction

Helicobacter pylori（H.pylori） is a major risk factor for gastric cancer. Our previous study found that activin A receptor type I (ACVR1) plays an important role in the pathogenesis of gastric mucosal lesions caused by Helicobacter pylori. Meanwhile, transcriptome data showed that ACVR1 was negatively correlated with POLD1, the gene encoding the catalytic subunit of EUkaryotic DNA polymerase (Pol δ) P125. However, the specific roles of ACVR1 and ACVR1 in H.pylori carcinogenesis remain unclear. This study investigated the molecular mechanism and potential association between H.pylori, ACVR1 and POLD1 in gastric cancer.

Aims & Methods

Gastric cancer cells, human tissue and mouse model were used in this study. We used helicobacter pylori infection models in vitro and in vivo, and Western blot, QRT-PCR, immunofluorescence, COIP, CCK8, Transwell and other tests for molecular, mechanism and function studies.To explore the role of Helicobacter pylori in DNA damage repair through ACVR1.

Results

Transcriptome data showed a negative correlation between ACVR1 and POLD1 expression. In vitro results showed that Hp infection could up-regulate the expression of ACVR1 and γ-H2AX, and decrease the expression of POLD1. After the deletion of ACVR1, the expression of POLD1 was increased. The expression of POLD1 decreased when ACVR1 was overexpressed. By predicting transcription factors, it was found that IRF3 could regulate the transcription of POLD1, and Hp infection could down-regulate the expression of IRF3, which was related to the virulence factor CagA. In addition, interference with the expression of POLD1 can up-regulate the expression of γ-H2AX, and inhibit cell proliferation, invasion and migration.

Conclusion

In summary, our study found that the ACVR1-IRF3-POLD1 signaling axis plays an important role in the process of Helicobacter pylori infection causing gastric cancer, and the ACVR1-IRF3-POLD1 axis can promote the occurrence of DNA damage while inhibiting the biobehavioral function of tumor cells.

Introduction

The gut microbiome exerts a significant influence on the host's cellular energy metabolism during homeostasis and disease, notably due to the production of metabolites (1), such as polyamines (2). Gut dysbiosis and bioenergetic alterations leading to metabolic shifts have been associated with altered cellular responses and are involved in intestinal disorders, such as inflammatory bowel disease (IBD) (3,4). Cadaverine, a gut polyamine derived from L-lysine decarboxylation, has been previously proposed to be transported into mitochondrial inner compartments in basal and induced conditions (5). On the other hand, it seems to be positively regulated in the gut of IBD patients (6). However, the biological significance in both contexts remains still unexplored.

Aims & Methods

This study uncovers the potential immunometabolic role of cadaverine in vitro and during intestinal inflammation. For that, single-cell energetic metabolism by profiling translation inhibition (SCENITH), luminescence and flow cytometry-based assays, Seahorse real-time cell metabolic analysis, metabolomics, RNAseq, and proteomics were applied to explore the role of cadaverine on energy metabolism in purified cells. Antibiotic-induced gut microbiota perturbations and dextran sodium sulfate (DSS)-induced colitis were carried out to further investigate its effect in vivo.

Results

Here we demonstrate that cadaverine enhances adenosine triphosphate (ATP) levels in THP-1 monocytic cell line as well as in human monocytes and macrophages obtained from healthy donors. Those results were associated with increased glucose uptake and utilization as a metabolic fuel and with higher mitochondrial dependence as a metabolic pathway, particularly elevating basal and maximal oxidative phosphorylation (OXPHOS) rates. The effects of cadaverine on mitochondrial functions persisted even in the presence of lipopolysaccharide (LPS) that triggers aerobic glycolysis in monocytes/macrophages. Interestingly, cadaverine presented immunomodulatory activity by increasing interleukin (IL)-10 levels and decreasing tumor necrosis factor (TNF)-α production in classical monocytes while triggering the polarization of macrophages to the M2 anti-inflammatory phenotype. Such immunomodulatory potential appears intricately dependent on mitochondrial respiration since this effect was blocked when OXPHOS was pharmacologically inhibited. Omics analysis reveals that itaconate metabolism and Krebs cycle modulation may be associated with cadaverine immunometabolic activity. Oral administration of cadaverine in antibiotics-induced gut microbiota-depleted mice rescued from both small intestine and colon macrophage energy deficiency. Furthermore, cadaverine also sustained OXPHOS and mitochondrial health features in those cells. As L-lysine decarboxylase genes are mostly expressed by gut Enterobacteriaceae, which in turn are augmented and suggested to be related to IBD, we specifically depleted this bacterial family with colistin in mice and induced colitis with DSS. In this setting cadaverine administration ameliorates disease severity by polarizing colon macrophages towards the M2 phenotype and preserving the overall mitochondrial features, such as mass, mitochondrial membrane potential, and reactive oxygen species, to sustain ATP production by OXPHOS.

Conclusion

Such discoveries at the metabolic level hold promise for identifying novel therapeutic strategies that target cellular energy metabolism and the gut microbiota to modulate monocyte and macrophage responses in IBD.

References

1. Michaudel C, Sokol H. The Gut Microbiota at the Service of Immunometabolism. Cell Metab. 2020 Oct 6;32(4):514-523.
2. Puleston DJ et al. Polyamines and eIF5A Hypusination Modulate Mitochondrial Respiration and Macrophage Activation. Cell Metab. 2019 Aug 6;30(2):352-363.e8.
3. Zeng Z et al. Glycolytic Activation of CD14+ Intestinal Macrophages Contributes to the Inflammatory Responses via Exosomal Membrane Tumor Necrosis Factor in Crohn's Disease. Inflamm Bowel Dis. 2024 Jan 5;30(1):90-102.
4. Lloyd-Price et al. Multi-omics of the gut microbial ecosystem in inflammatory bowel diseases. Nature. 2019 May;569(7758):655-662.
5. Toninello A, Dalla Via L, Testa S, Siliprandi D. Electrophoretic polyamine transport in rat liver mitochondria. Amino Acids. 1992 Feb;2(1-2):69-76.
6. Li M, Yang L, Mu C, Sun Y, Gu Y, Chen D, Liu T, Cao H. Gut microbial metabolome in inflammatory bowel disease: From association to therapeutic perspectives. Comput Struct Biotechnol J. 2022 Apr 4;20:2402-2414.

Disclosure

Harry Sokol reports lecture fees, board membership, or consultancy from Carenity, AbbVie, Astellas, Danone, Ferring, Mayoly Spindler, MSD, Novartis, Roche, Tillots, Enterome, BiomX, Biose, Novartis, Takeda, Biocodex and is cofounder of Exeliom Biosciences.