Mitochondrial Peptide MOTS-c Shields Lungs From Reperfusion Injury via Novel Nuclear Pathway
MOTS-c enters cell nuclei during oxidative stress to activate antioxidant genes, protecting lungs during cardiac surgery—and predicting ARDS risk.
Summary
Researchers discovered that MOTS-c, a 16-amino acid peptide encoded in mitochondrial DNA, protects lung endothelial cells during ischemia-reperfusion injury by translocating into the nucleus via a MYH9-dependent mechanism. During oxidative stress, reactive oxygen species activate the kinase CK2A, which phosphorylates MYH9 at Ser1943, enabling MOTS-c to bind the MYH9-γ-actin complex and travel to the nucleus. Once there, MOTS-c directly activates antioxidant genes like HMOX1 and NQO1 via antioxidant response elements. In 150 cardiac surgery patients, rising serum MOTS-c levels over 24 hours post-bypass (ΔMOTS-c) predicted ARDS with an AUC of 0.885. Exogenous MOTS-c administration in rat models reduced lung damage, inflammation, and mortality.
Detailed Summary
Cardiopulmonary bypass (CPB) surgery carries a significant risk of acute respiratory distress syndrome (ARDS), complicating up to 20% of procedures with mortality exceeding 80% in severe cases. The underlying driver is lung ischemia-reperfusion injury (LIRI), which unleashes oxidative stress and endothelial barrier breakdown. Despite advances in surgical technique, no targeted therapy exists to bolster pulmonary stress resistance—particularly in elderly, high-risk patients.
This study investigates MOTS-c, a mitochondria-encoded 16-amino acid peptide, as a previously unrecognized endogenous defender against LIRI. Using rat LIRI models, the authors found that pulmonary endothelial cells showed the most pronounced MOTS-c upregulation following injury, correlating with preserved vascular barrier integrity and reduced oxidative damage. This cell-type specificity pointed toward a direct protective role in the endothelium.
Mechanistically, hypoxia-reoxygenation triggers ROS-dependent activation of casein kinase II subunit alpha (CK2A), which phosphorylates the cytoskeletal protein MYH9 at serine residue 1943. This phosphorylation event enables MOTS-c to bind the MYH9-γ-actin complex, which then serves as a molecular shuttle transporting MOTS-c into the nucleus. Combined RNA sequencing and ChIP sequencing revealed that nuclear MOTS-c directly binds to promoters of antioxidant genes—including HMOX1 and NQO1—via antioxidant response elements (AREs), activating a transcriptional antioxidant defense program. This establishes MOTS-c as both a stress sensor and a transcriptional co-activator operating through a ROS-CK2A-MYH9 signaling axis.
Clinically, the team prospectively enrolled 150 patients undergoing CPB cardiac surgery, measuring serum MOTS-c at baseline, immediately post-CPB, and 24 hours postoperatively. The 24-hour increment in MOTS-c (ΔMOTS-c) was significantly lower in patients who developed ARDS (n=38) compared to non-ARDS patients (n=112). Multivariate predictive models incorporating ΔMOTS-c achieved an AUC of 0.885, outperforming traditional biomarkers alone. ΔMOTS-c also correlated inversely with serum MDA (lipid peroxidation marker) and positively with PaO2/FiO2 ratio, linking the biomarker to actual lung function. Finally, exogenous MOTS-c administration in rat LIRI models recapitulated these endogenous protective effects, reducing oxidative damage, pulmonary inflammation, and mortality.
These findings position MOTS-c as a dual-function molecule: a real-time prognostic biomarker for post-CPB ARDS and a therapeutic candidate for lung protection. The identification of MYH9 as its nuclear transport partner opens new mechanistic avenues, and the conservation of this pathway between endogenous upregulation and exogenous supplementation strengthens its translational potential.
Key Findings
- ROS activate CK2A to phosphorylate MYH9 at Ser1943, enabling MOTS-c nuclear transport via MYH9-γ-actin complexes.
- Nuclear MOTS-c directly binds ARE promoters to transcriptionally activate HMOX1 and NQO1 antioxidant genes.
- Pulmonary endothelial cells show the greatest MOTS-c upregulation after LIRI, correlating with barrier preservation.
- Post-CPB ΔMOTS-c (24h increment) predicted ARDS with AUC 0.885, outperforming classical biomarkers.
- Exogenous MOTS-c administration in rats reduced lung oxidative damage, inflammation, and mortality.
Methodology
The study combined prospective clinical enrollment (n=150 CPB patients with serial serum MOTS-c measurements), rat LIRI models with exogenous MOTS-c administration, and mechanistic in vitro hypoxia-reoxygenation experiments in endothelial cells. Transcriptomic targets were identified using integrated RNA-seq and ChIP-seq, with protein interactions validated by co-immunoprecipitation and phosphorylation assays.
Study Limitations
The clinical cohort was single-center and relatively small (n=150), limiting generalizability; ARDS severity was limited to mild and moderate cases with no severe ARDS subgroup. The mechanistic studies rely on in vitro and rat models, and the direct causal role of MYH9 phosphorylation in human LIRI requires confirmation. Long-term outcomes and optimal MOTS-c dosing for therapeutic use were not assessed.
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