NAT10 Enzyme Drives Sepsis Heart Damage — Blocking It May Save Lives
A newly identified RNA modification pathway in macrophages fuels deadly cardiac dysfunction during sepsis, and blocking it with a drug reverses the damage.
Summary
Researchers discovered that the enzyme NAT10 is dramatically upregulated in macrophages exposed to bacterial endotoxin (LPS). This upregulation is driven by the deubiquitinase USP39, which prevents NAT10 protein from being degraded. NAT10 then adds ac4C chemical tags to mRNA of the transcription factor ETS2, boosting its stability and translation and amplifying a pro-inflammatory cytokine storm. In mice with endotoxemia, deleting NAT10 specifically in myeloid cells — or pharmacologically inhibiting it with the drug remodelin — significantly reduced inflammation and preserved heart function. The findings identify a novel post-transcriptional regulatory axis and suggest NAT10 as a druggable target for sepsis-induced cardiac dysfunction.
Detailed Summary
Sepsis kills roughly 40–50% of affected patients partly because the overwhelming inflammatory response cripples the heart. Macrophages are central culprits: once activated by bacterial lipopolysaccharide (LPS), they flood the body with cytokines that impair cardiomyocyte contractility and trigger cell death. Current treatments do little to specifically modulate this immune overactivation, leaving a critical therapeutic gap.
This study focused on N-acetyltransferase 10 (NAT10), the sole known enzyme that catalyzes the ac4C (N4-acetylcytidine) RNA modification. Using bone marrow-derived macrophages (BMDMs) and RAW264.7 cells, the researchers showed that LPS causes a dose- and time-dependent rise in NAT10 protein — peaking at 24 hours — without changing NAT10 mRNA, indicating post-translational control. A cycloheximide chase assay revealed that LPS extends NAT10 protein half-life by suppressing its K48-linked ubiquitination and proteasomal degradation. IP/mass spectrometry pinpointed USP39 as the deubiquitinase responsible: USP39 physically binds NAT10 in the nucleus, removes K48-linked ubiquitin chains at key lysine residues (K195, K426), and stabilizes the protein. A catalytically inactive USP39 mutant (C306A) failed to rescue NAT10, confirming enzymatic deubiquitination is required.
To map which mRNAs NAT10 regulates, the team performed ac4C RNA sequencing, ribosome profiling, and transcriptome analysis of Nat10-knockout versus wild-type BMDMs after LPS challenge. These multi-omics approaches converged on ETS2, a transcription factor known to drive inflammatory gene programs, as the primary NAT10 target. NAT10-mediated ac4C modification stabilized ETS2 mRNA and enhanced its translation. Consequently, Nat10-deficient macrophages showed markedly lower ETS2 protein, reduced iNOS expression, and diminished secretion of IL-6, TNF-α, and IFN-γ, as well as lower surface expression of the M1 activation markers CD80 and CD86. Conversely, NAT10 overexpression amplified these pro-inflammatory outputs.
The physiological relevance was confirmed in a murine endotoxemia model. Myeloid-specific Nat10 knockout mice exhibited substantially improved cardiac function compared to floxed controls, with reduced inflammatory infiltration and cytokine burden. Importantly, pharmacological inhibition of NAT10 with remodelin phenocopied the genetic knockout, protecting cardiac function without requiring gene editing — a finding with direct translational value.
The work establishes a previously unrecognized USP39→NAT10→ac4C→ETS2 axis that amplifies macrophage-driven inflammation and cardiac injury during endotoxemia. Because remodelin is already a known small molecule, this pathway may be actionable in clinical settings, though significant development work remains before human application.
Key Findings
- NAT10 protein rises sharply in LPS-activated macrophages due to USP39-mediated deubiquitination, not increased transcription.
- NAT10 deposits ac4C marks on ETS2 mRNA, stabilizing it and boosting translation to amplify pro-inflammatory cytokine production.
- Myeloid-specific Nat10 knockout mice are protected from endotoxemia-induced cardiac dysfunction and show reduced systemic inflammation.
- The NAT10 inhibitor remodelin mimics genetic knockout, reducing cytokine storm and preserving heart function in mice.
- USP39's catalytically inactive mutant (C306A) cannot stabilize NAT10, confirming enzymatic deubiquitination drives the pathway.
Methodology
The study combined in vitro experiments in BMDMs and RAW264.7 cells with myeloid-specific Nat10 knockout mice and an LPS-induced endotoxemia model. Multi-omics approaches — ac4C-seq, ribosome profiling, RNA-seq, and IP/mass spectrometry — were used to identify molecular targets and mechanisms.
Study Limitations
All in vivo data come from mouse endotoxemia models, which incompletely recapitulate human sepsis physiology. The study does not evaluate long-term safety or off-target effects of remodelin, and the causal role of ETS2 downstream of NAT10 warrants further validation in human macrophages and clinical samples.
Enjoyed this summary?
Get the latest longevity research delivered to your inbox every week.
Enter your email to subscribe: