Objective: To investigate the protective effect of Lycium barbarum polysaccharide (LBP) against testicular spermatogenic injury in mice with oxidative stress (OS) and its mechanism.
Methods: A unique OS model was made in 1.5-month-old mice with mitochondrial inner membrane-like peptide-2 mutation (Immp2l－/－), which were fed with water (the negative control group) or LBP in water at the concentration of 20 mg/kg (the LBP intervention group), and wild-type Immp2l＋/＋ mice used as normal controls and fed with water only. Then all the mice were sacrificed at 13 months old and the testis tissue harvested for observation of pathological changes by HE staining, measurement of routine semen parameters, and detection of the apoptosis of spermatogenic cells by TUNEL and the expression levels of glutathione peroxidase 4 (GPX4) and apoptosis-inducing factor (AIF) by immunohistochemistry and Western blot.
Results: Thinned testicular cortex was observed in the negative controls, with evident vacuolar degeneration and reduced numbers of germ cells and elongated spermatids in the lumen of the seminiferous tubules, but all these pathological changes were improved and the germ cells at different levels orderly arranged in the LBP intervention group. Compared with the normal controls, the mice in the negative control group showed dramatically reduced sperm count (［72.89 ± 8.28］ vs ［20.78 ± 1.45］ ×106, P<0.01) and the percentages of progressively motile sperm (PMS) (［58.62 ± 6.15］% vs ［18.37 ± 2.67］%, P<0.01) and morphologically normal sperm (MNS) (［65.81 ± 7.69］% vs ［20.33 ± 3.17］%, P<0.01) and increased apoptosis of spermatogenic cells (［1.45 ± 0.43］% vs ［7.14 ± 0.78］%, P<0.01). LBP intervention, however, significantly increased the sperm count (［45.25 ± 3.39］ ×106, P<0.05), PMS (［36.34 ± 4.56］%, P<0.05) and MNS (［38.72 ± 3.63］%, P<0.05) and decreased the apoptosis of spermatogenic cells (［2.28 ± 0.07］%, P<0.01). The mice in the LBP intervention group, in comparison with the negative controls, exhibited remarkably up-regulated expression of GPX4 (2.75 ± 0.48 vs 1.43 ± 0.17, P<0.05) and down-regulated expression of AIF (2.43 ± 0.15 vs 1.35 ± 0.51, P<0.05).
Conclusions: Lycium barbarum polysaccharide at 20 mg/kg can reduce testicular spermatogenic injury in Immp2l－/－ mice with oxidative stress through GPX4 and AIF pathways.
Keywords: Immp2l－/－ mouse; glutathione peroxidase 4 and apoptosis-inducing factor pathways; lycium barbarum polysaccharide; testis; oxidative stress.