Zinc Deficiency Promotes Testicular Cell Apoptosis in Mice

Zinc (Zn) plays an important role in spermatogenesis, and carbon tetrachloride (CCl4) induces testicular oxidative damage and cell death. The objective of the present study was to define the effects of Zn deficiency in combination with CCl4 treatment on testicular apoptosis and the associated mechanisms. Mice were fed the following diets with three different Zn levels for 6 weeks: normal zinc (ZN) diet (30 mg Zn/kg), zinc-deficient (ZD) diet (2 mg Zn/kg), and adequate zinc (ZA) diet (100 mg Zn/kg). Beginning in the third week, CCl4 was intraperitoneally injected into half of the mice in each diet group six times over 3 weeks. We found that Zn was distributed in various tissues and organs in normal mice and that the zinc content in the testis of normal mice was high. The Zn-deficient diet reduced the zinc concentration in the testis tissue, and the testicular/body weight ratio significantly decreased. Moreover, the TUNEL results proved that CCl4 stimulation of mice fed with a zinc-deficient diet caused marked apoptosis of testicular cells. Furthermore, the ROS levels in the testes obviously increased after Zn-deficient mice were stimulated with CCl4, whereas reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) showed reduced activities. In addition, proteins associated with the apoptosis signaling pathway were detected with ELISA kits. P-p53, cleaved caspase-3, cleaved PRAP, p-Bad, p-JNK, p-ERK, and p-NF-κB p65 increased by varying degrees under zinc deficiency or CCl4 stimulation. All the data indicated that Zn deficiency significantly enhanced the harm to the testis induced by oxidative stress and damage, while CCl4 stimulation exacerbated the oxidative damage in testicular cells, leading to apoptosis through the activation of p53, MAPK, and NF-κB.