Humanin-G protects against septic ARDS by restoring mitochondrial function in lung endothelial cells

Mitochondrial impairment is a critical driver of endothelial damage in septic acute respiratory distress syndrome (ARDS), a severe inflammatory lung condition with high mortality. Current treatments often fall short in addressing the underlying cellular dysfunction. Humanin (HN) and its derivative, Humanin-G (HNG), are mitochondrial polypeptides known for their anti-apoptotic and neuroprotective properties against oxidative stress. This study investigates HNG's potential to mitigate pulmonary vascular endothelial damage in the context of septic ARDS, targeting the mitochondrial dysfunction implicated in disease progression.

Researchers established a murine model of septic ARDS via intraperitoneal injection of lipopolysaccharide (LPS). The study evaluated the effects of HNG pretreatment on inflammatory responses and lung injury. In vivo and in vitro experiments assessed inflammatory factor expression using qPCR and Western blot. Lung injury was evaluated by H&E staining, while mitochondrial morphology was examined via transmission electron microscopy. Mitochondrial respiratory function was analyzed using Seahorse analysis, and membrane potential was assessed with JC-1 staining. Protein-peptide interaction analysis and immunoprecipitation identified HNG's binding partners, with WB analysis confirming downstream signaling effects.

In septic ARDS patients, serum Humanin concentrations initially increased on Day 1, then progressively decreased from Day 3 to Day 7. In the murine septic ARDS model, HNG pretreatment significantly reduced inflammatory factor expression in both in vivo and in vitro settings. This protective effect extended to lung injury, where HNG treatment conferred substantial protection. Critically, HNG restored normal mitochondrial morphology, improved mitochondrial respiratory function, and corrected impaired mitochondrial membrane potential. Protein-peptide interaction analysis indicated that HNG binds to the interleukin-6 receptor alpha (IL-6Rα). Immunoprecipitation further confirmed that HNG competitively interacts with the IL-6 receptor family compared to IL-6.