Transcriptome sequencing and experiments reveal the effect of formyl peptide receptor 2 on liver homeostasis

ARTICLE HIGHLIGHTS

Research background

Formyl peptide receptor 2 (Fpr2) plays an important role in host’s defense and inflammatory response, as it can help the body control bacterial infections. Studies have found that in Fpr2^-/- mice, the liver is the most severely damaged target organ in bloodstream infections. However, the reason for this is unclear.

Research motivation

To verify the role of Fpr2 in liver homeostasis, to provide new clues for the decreased ability of the liver to clear bacteria after Fpr2 deficiency, and to provide new ideas for future drug research and development.

Research objectives

To investigate the role of Fpr2 in liver homeostasis.

Research methods

The differentially expressed genes (DEGs) in Fpr2^-/- and wild-type (WT) mice were determined by transcriptome sequencing, and the biological functions of DEGs were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Quantitative real-time polymerase chain reaction (qRT PCR) and western blot (WB) were used to further validate the expression levels of differential genes. The Cell Counting Kit-8 assay was used to study cell proliferation. A cell cycle detection kit was used to measure the distribution of cell cycles. Luminex assay was used to analyze cytokine levels in the liver. A fully automated biochemical analyzer was used to detect the levels of serum biochemical indicators and C-reactive protein in WT and Fpr2^-/- mice. The number of neutrophils in the liver was detected by flow cytometry. The histopathology of the liver was analyzed by hematoxylin-eosin staining.

Research results

Transcriptome sequencing showed that, compared with WT group, 445 genes in the liver of Fpr2^-/- mice had significant changes in the expression level, including 325 upregulated genes and 120 downregulated genes. The functional enrichment analysis of GO and KEGG indicated that these DEGs were mainly related to cell cycle. qRT-PCR validated that after Fpr2 deletion, the expression levels of CycA, CycB1, Cdc20, and Cdc25c genes were upregulated. Both qRT-PCR and WB confirmed a decrease in the expression of CDK1. WRW4 (an antagonist of Fpr2) could inhibit the proliferation of HepG2 cells in a concentration dependent manner. The levels of serum alanine aminotransferase levels increased in Fpr2^-/- mice with statistical significance. Luminex assay measurements showed that the expression levels of interleukin (IL)-10, IL-18, and CXCL-1 were significantly reduced in the liver of Fpr2^-/- mice.

Research conclusions

Fpr2 may exert a protective effect on the liver by participating in the regulation of cell cycle and proliferation, as well as affecting the expression of IL-10 and CXCL-1.

Research perspectives

Fpr2 plays an important role in maintaining liver homeostasis, and its agonist may be a potential drug against bacterial infection.