N-Homocysteinylation of HMGB1/2 Promotes Corpus Cavernosum Endothelial Senescence in Erectile Dysfunction

Homocysteine (Hcy) is an age-related risk factor for erectile dysfunction (ED), with enhanced vascular toxicity in middle-aged and elderly individuals. However, folate-based Hcy-lowering therapies have shown limited efficacy, necessitating a reevaluation of its age-dependent pathogenic mechanism. Here, we demonstrate that senescent endothelial cells exhibit heightened responsiveness of methionyl-tRNA synthetase 1 (MARS1) to Hcy, promoting the production of homocysteine thiolactone (HTL) and widespread N-homocysteinylation (K-Hcy) of proteins. K-Hcy, rather than acetylation, drives cytoplasmic translocation and extracellular release of high mobility group box proteins 1 and 2 (HMGB1/2), amplifying the senescence-associated secretory phenotype (SASP). Competitive inhibition of MARS1 with N-acetylcysteine (NAC) attenuates endothelial senescence and improves erectile function in middle-aged individuals with hyperhomocysteinemia by reducing HTL, rather than Hcy itself, while synergizing with tadalafil. Collectively, our findings highlight the pivotal role of the age-dependent MARS1-HTL axis in the pathogenesis of homocysteine-induced ED, offering a promising therapeutic strategy for ED in the aging population.