FMO2 (Flavin Containing Monooxygenase 2) Prevents Cardiac Fibrosis via CYP2J3-SMURF2 Axis

Abstract

BACKGROUND: Cardiac fibrosis is a common pathological feature associated with adverse clinical outcome in postinjury remodeling and has no effective therapy. Using an unbiased transcriptome analysis, we identified FMO2 (flavin-containing monooxygenase 2) as a top-ranked gene dynamically expressed following myocardial infarction (MI) in hearts across different species including rodents, nonhuman primates, and human. However, the functional role of FMO2 in cardiac remodeling is largely unknown. METHODS: Single-nuclei transcriptome analysis was performed to identify FMO2 after MI; FMO2 ablation rats were generated both in genetic level using the CRISPR-cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat–associated 9) technology and lentivirus-mediated manner. Gain-of-function experiments were conducted using postn -promoter FMO2, miR1a/miR133a-FMO2 lentivirus, and enzymatic activity mutant FMO2 lentivirus after MI. RESULTS: A significant downregulation of FMO2 was consistently observed in hearts after MI in rodents, nonhuman primates, and patients. Single-nuclei transcriptome analysis showed cardiac expression of FMO2 was enriched in fibroblasts rather than myocytes. Elevated spontaneous tissue fibrosis was observed in the FMO2-null animals without external stress. In contrast, fibroblast-specific expression of FMO2 markedly reduced cardiac fibrosis following MI in rodents and nonhuman primates associated with diminished SMAD2/3 phosphorylation. Unexpectedly, the FMO2-mediated regulation in fibrosis and SMAD2/3 signaling was independent of its enzymatic activity. Rather, FMO2 was detected to interact with CYP2J3 (cytochrome p450 superfamily 2J3). Binding of FMO2 to CYP2J3 disrupted CYP2J3 interaction with SMURF2 (SMAD-specific E3 ubiquitin ligase 2) in cytosol, leading to increased cytoplasm to nuclear translocation of SMURF2 and consequent inhibition of SMAD2/3 signaling. CONCLUSIONS: Loss of FMO2 is a conserved molecular signature in postinjury hearts. FMO2 possesses a previously uncharacterized enzyme-independent antifibrosis activity via the CYP2J3-SMURF2 axis. Restoring FMO2 expression exerts potent ameliorative effect against fibrotic remodeling in postinjury hearts from rodents to nonhuman primates. Therefore, FMO2 is a potential therapeutic target for treating cardiac fibrosis following injury.

Flavin containing monooxygenase 2 regulates renal tubular cell fibrosis and paracrine secretion via SMURF2 in AKI‑CKD transformation

“…By using analysis of transcriptomic data following renal IRI, it was discovered that the expression of one member of the FMO gene family, FMO2, was highly enriched in tubular cells and dynamically associated with renal injury and fibrotic remodeling. However, previous studies have shown that FMO2-mediated inhibition of TGF-β activity is independent of its enzymatic activity ( 18 ). Although non-enzymatic isoforms of FMO2 have been reported in humans and rats ( 30 - 32 ) and have been shown to influence the lifespan of the nematode Caenorhabditis elegans ( 33 ), their biological roles remain unclear.…”

“…The data indicated dynamic changes in the expression of the flavin-containing monooxygenase (FMO) family between 2 h and 14 days post-ischemia reperfusion. A recent study has identified that FMO2 possesses a previously uncharacterized enzyme-independent antifibrotic activity via the cytochrome P450 2J3-SMAD ubiquitination regulatory factor 2 (SMURF2) axis ( 18 ). Particularly, FMO1 and FMO2, which are abundantly expressed in the kidney, are of significant interest.…”

Effect of three oral pathogens on the TMA-TMAO metabolic pathway

“…Figure 4B further support that under the background of normal mice, the process of Pg -induced elevated plasma TMAO levels depends more on the oxidation of TMA in the liver rather than the generation of TMA in the intestine. Pg , Fn , and Sm groups exhibited a downregulation in FMO2 gene expression compared to the control group, which potentially indicates a general stress response of the liver to oral pathogenic bacterial infection ( Ni et al., 2022 ). In vitro TMAO exacerbates lipid accumulation, inflammation, and fibrosis in the liver ( Vallianou et al., 2019 ; Carpino et al., 2020 ).…”

Comparative Analysis of Heart Regeneration: Searching for the Key to Heal the Heart—Part II: Molecular Mechanisms of Cardiac Regeneration

“…FMO2 is implicated in the recruitment of cytochrome p450 superfamily 2J3 (CYP2J3), blocking the CYP2J3/SMURF2 interaction and promoting the nuclear translocation of Smad2 (switching to its inactive form). For this reason, FMO2 has an anti-fibrotic role after cardiac injury, being a possible therapeutic target [ 204 ]. Li et al (2021) [ 205 ] also described a member of the TGF-β family, Left-right determination factor (Lefty1), with an anti-fibrotic function, since both in vitro and in vivo assays in mice show that Lefty1 reduces CFs proliferation and differentiation through the inhibition of phosphorylation of Smad2 and ERK1/2 after MI [ 205 ] ( Figure 4 B).…”