Objective: To investigate oxidative stress-mediated damage to the epididymal epithelial tight junction protein ZO-1 and its impact on epididymal function in varicocele rats.
Methods: We randomly divided 45 male adolescent SD rats into three groups of equal number: sham operation (left renal vein exposed and isolated), experimental (left renal vein constricted and collaterals of the left spermatic vein fully ligated), and treatment (60-day intragastric administration of vitamin E at 150 mg/kg/d after modeling). At 60 days after modeling, we observed the histological changes in the left epididymis, detected the expressions of ZO-1 and other tight junction-related proteins by real-time quantitative PCR, immunohistochemistry, immunofluorescence staining and Western blotting, determined sperm motility, and measured the levels of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), methylene dioxyamphetamine (MDA) and α-glucosidase (α-Glu) in the epididymal tissue of the rats.
Results: Compared with the rats of the sham operation group, those of the experimental group showed disorganized epithelial structure and decreased number of epithelial cells in the left epididymis, with some epithelial cells desquamated into the lumen. The expression of ZO-1 was significantly lower in the experimental than in the sham operation group (P < 0.05) but markedly upregulated after VE treatment (P < 0.05). In comparison with the sham operation group, the animals in the experimental group exhibited remarkably increased content of MDA in the epididymal tissue (［0.41 ± 0.05］ vs ［1.21 ± 0.18］ nmol/mg prot, P < 0.05) but decreased levels of SOD (［814.65 ± 73.64］ vs ［298.62 ± 67.84］ U/mg prot, P < 0.05), T-AOC (［0.84 ± 0.07］ vs ［0.24 ± 0.04］ nmol/mg prot, P < 0.05) and α-Glu (［11.72 ± 2.72］ vs ［5.82 ± 1.24］ U/mg prot, P < 0.05). VE treatment, however, remarkably reduced the content of MDA (［0.69 ± 0.12］ nmol/mg prot) and elevated the levels of SOD (［497.73 ± 48.03］ U/mg prot), T-AOC (［0.42 ± 0.06］ nmol/mg prot) and α-Glu (［9.11 ± 1.91］ U/mg prot) as compared with those in the experimental group (all P < 0.05). The percentage of progressively motile sperm was significantly lower in the experimental than in the sham operation group (［31.33 ± 6.32］% vs ［71.21 ± 5.21］%, P < 0.05), but markedly increased after VE treatment (［60.68 ± 5.31］%, P < 0.05).
Conclusions: Varicocele reduces the expression of the EETJ protein ZO-1 and impairs epididymal function via oxidative stress, while vitamin E can effectively upregulate the ZO-1 expression and improve epididymal function by decreasing oxidative stress in the epididymis of varicocele rats.
Keywords: epididymis; oxidative stress; rat; tight junction; zonula occluden 1 (ZO-1); varicocele.