Combined Noise and CO Exposure Compromises Blood-Testis Barrier Integrity through Epigenetic Dysregulation of Tight Junction Proteins: Protection by Pterostilbene.

Combined exposure to environmental noise and carbon monoxide (CO) poses a growing threat to male reproductive health, yet the mechanisms underlying their combined toxicity remain incompletely understood. This study investigated the effects of combined noise and CO exposure on Sertoli cells and the blood-testis barrier (BTB), explored the potential epigenetic mechanisms involved, and evaluated the protective efficacy of pterostilbene (PTE) in male rats. Animals were exposed to noise (85 dB), CO (410 ppm), or both for 2 h/day over 60 days, with a subset receiving PTE (80 mg/kg/day). Combined exposure, but neither stressor alone, induced significant Sertoli cell loss, suppressed inhibin-B(INH-B) secretion, and disrupted BTB ultrastructure, accompanied by the coordinated downregulation of multiple junctional proteins including ZO-1, N-cadherin, and Claudin family members. Integrative transcriptomic and methylomic analyses suggested that this multi-target junctional impairment was associated with promoter hypermethylation-mediated transcriptional silencing, with Cldn5, Cldn9, Cldn18, and Cldn22 identified as representative targets. PTE co-treatment attenuated the aberrant methylation, restored junctional protein expression, and preserved BTB structural integrity. These findings suggest that promoter hypermethylation of BTB junctional genes may represent an important epigenetic mechanism underlying co-exposure-induced reproductive toxicity, and that PTE may serve as a promising protective intervention for populations at risk of combined environmental exposure.