Over-expression of IL-10 in testicular tissues of immature as compared to adult mice; induction by lipopolysaccharide

Abstract

To evaluate the expression levels and the cellular origin of IL-10 in testicular tissue of sexually immature and adult mice, under physiological and pathological conditions. In vivo and in vitro study Eight weeks or two-weeks old Balb/c mice were intraperitonealy (i.p) injected with saline (control) or LPS (2, 20, 100 mg/100 ml/mouse). Three hours or 16 hours after the injection, testes were collected, tunica albugina was removed, and testes were formalin-fixed and paraffin-embedded for immunohistochemical staining (IHC) or homogenized for homogenates preparing or for RNA extraction. Leydig cells (LC) were separated from testes of 8 week old mice by Percoll gradient. LC cultures (2.5 × 104 cells/0.5ml/well) were incubated in the absence or presence of LPS (0.1, 1 or 5 mg/ml) or LH (0.1, 1 or 5 IU/ml) for 3 and 16 hours. The levels of IL-10 were examined in testicular homogenates and Leydig cell supernatants by specific ELISA. The levels of IL-10 were significantly higher in testicular tissue of sexually immature than mature mice (as examined by ELISA and RNA expression). Immunohistochemical staining of testicular tissues of sexually immature and adult mice show that the main producing cells are interstitial cells (Leydig cells and macrophages) and germ cells. Interstitial cells express higher levels of IL-10 than germ cells. Peritubular cells of sexually immature and adult mice did not express IL-10. Intraperitoneal injection of LPS (2,20 or 100 mg/ml/mouse) for 3 hours or 24 hours were significantly (p< 0.05) increased the levels of IL-10 in the homogenates, IHC and RNA expression of both adult and sexually immature mice. This increase was dose- and time-course dependent manner. Leydig cell cultures constitutively produced IL-10, however stimulation with LH or LPS did not affect this capacity. Our results demonstrate for the first time the expression of IL-10 in Leydig and germ cells of testicular tissues from adult and sexually immature mice. The over-expression of IL-10 in immature mice as compared to adults may indicate the involvement of IL-10 in spermatogenesis and the possibility of its regulation by gonadotropins and testosterone. In addition, up-regulation of IL-10 levels following systemic infection/inflammation (LPS) may suggest its involvement in the regulation of immune response in the testis (regulation Fas/Fas ligand system and/or cytokine expression). Thus, testicular IL-10 should be considered in male fertility.