Cigarette smoke, an indoor environmental pollutant, poses a major threat to male reproductive health worldwide, yet its complex composition has hindered the identification of the important toxic components responsible for this damage. We previously identified 5-hydroxymethylfurfural (5-HMF) as an abundant toxic component of cigarette smoke extract (CSE), but its role and mechanism in spermatogenesis remain unclear. In this study, we first identified a positive correlation between serum levels of 5-HMF and those of nicotine and cotinine in a community-based cross-sectional study in Jiangsu province, China. We then exposed male C57BL/6 mice to aerosolized CSE, 5-HMF-enriched fraction of CSE (CSE-HMF), or pure 5-HMF for 60 days. The results showed that 5-HMF appeared in blood and testis of mice. Both CSE-HMF and pure 5-HMF recapitulated the reproductive damage observed with CSE, significantly impairing testicular morphology and spermatogenesis without altering sex hormone levels. Furthermore, 5-HMF penetrated the testis and disrupted the blood-testis barrier (BTB), compromising its function and reducing transepithelial electrical resistance (TER) in Sertoli cells. These impairments were driven by increased autophagic flux and subsequent downregulation of tight junction (TJ) proteins, which was prevented by autophagy inhibitors. Mechanistically, 5-HMF decreased p-mTOR and up-regulated Atg12 to stimulate autophagic flux in testis and Sertoli cells. Heterozygous deficiency of Atg12 (atg12+/-) significantly attenuated 5-HMF-induced autophagy activation, BTB disruption, and spermatogenic impairment. Our work identifies 5-HMF as one of the important toxic components of cigarette smoke that impairs spermatogenesis by triggering mTOR/Atg12-dependent autophagy, which disrupts TJs between Sertoli cells and consequently compromises the BTB.
Yu et al. (Thu,) studied this question.