LAT1-mediated delivery of engineered R13A-MOTS-c attenuates radiation-induced lung injury via Nrf2 activation and mitochondrial protection.
This study investigated an engineered variant of the mitochondria-derived peptide MOTS-c, called R13A-MOTS-c, designed to overcome the poor cellular permeability of the wild-type peptide. The researchers substituted arginine at position 13 with alanine to increase hydrophobicity, then characterized the modified peptide's uptake mechanism, showing through competition assays and knockdown experiments that it enters cells via the LAT1 amino acid transporter. In vitro, R13A-MOTS-c was reported to reduce inflammatory markers, oxidative damage, and mitochondrial dysfunction in mouse lung epithelial (MLE-12) cells exposed to radiation. In vivo, C57BL/6 mice receiving thoracic irradiation (20 Gy) and treated with intraperitoneal R13A-MOTS-c showed attenuated pulmonary inflammation, oxidative stress, and mitochondrial impairment compared to controls. The proposed mechanism centers on Nrf2 pathway activation, supported by evidence of increased nuclear Nrf2 translocation and upregulation of downstream target genes; protective effects were lost when LAT1 or Nrf2 was inhibited or knocked out. Key limitations include exclusive use of animal and cell models with no human data, a single radiation dose and treatment regimen tested, and the need for further pharmacokinetic and safety characterization before clinical translation.
Why this grade: All mechanistic and efficacy data derive from mouse (C57BL/6) in vivo experiments and murine cell-line (MLE-12) in vitro work, with no human subjects or clinical data included.
MOTS-c exhibits substantial antioxidant and anti-inflammatory properties, yet its therapeutic potential is constrained by poor membrane permeability due to its high polarity. To overcome this limitation, we engineered R13A-MOTS-c by substituting the polar arginine at position 13 with alanine in the wild-type peptide (Met-Arg-Trp-Gln-Glu-Met-Gly-Tyr-Ile-Phe-Tyr-Pro-Arg-Lys-Leu-Arg). This modification increased the peptide's hydrophobicity index from -0.938 to -0.544, measurably improving its cellular uptake. Functional uptake assays, including competition with canonical LAT1 substrates (leucine, BCH) and LAT1 knockdown experiments, further confirmed that R13A-MOTS-c enters cells via LAT1-mediated transport. In vitro experiments revealed that R13A-MOTS-c suppressed inflammatory responses, oxidative damage, and mitochondrial impairment in MLE-12 cells. In vivo studies demonstrated that daily intraperitoneal administration of R13A-MOTS-c (5 mg/kg for 2 weeks) effectively mitigated radiation-induced pulmonary inflammation, oxidative stress, and mitochondrial dysfunction in C57BL/6 mice exposed to 20 Gy thoracic irradiation. Mechanistically, R13A-MOTS-c activated the Nrf2 signaling pathway, as evidenced by increased nuclear translocation of Nrf2 and upregulation of its downstream targets gene. These effects were abolished upon LAT1 inhibition, Nrf2 inhibition, or in Nrf2-knockout conditions. Collectively, these findings indicate that LAT1-mediated uptake of R13A-MOTS-c alleviates radiation-induced lung injury through Nrf2 pathway activation and mitochondrial function restoration, offering a promising therapeutic strategy for clinical applications.
Educational summary of published research — not medical advice. License: cc by. Full text is shown only where licensing permits.