Cadmium is an endocrine disruptor, impairing male reproduction. The objective of this study is to investigate whether cadmium affects rat Leydig cell regeneration and to dissect the underlying mechanism. Adult male Sprague-Dawley rats received a single intraperitoneal injection (i.p.) of 0, 0.5 or 1.0 mg/kg of cadmium chloride, followed by ethane dimethane sulfonate (EDS) treatment to eliminate adult Leydig cells 20 days later. Compared to control (0 dose), cadmium treatment reduced serum testosterone levels by days 21, 35, and 56 after EDS treatment. Serum luteinizing hormone (LH) levels were also affected by day 56, the only time point examined. There were fewer regenerated Leydig cells in the cadmium-treated testis on days 35 and 56 after EDS treatment. Further studies demonstrated that the mRNA or protein levels of Leydig (Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, and Hsd11b1), non-Leydig (Fshr and Dhh), and gonadotroph (Lhb) cells were also significantly lower in cadmium-treated animals. Since LH and desert hedgehog (DHH) are critical factors for Leydig cell differentiation, our result demonstrated that the lower doses of cadmium exposure, even briefly, may permanently damage Leydig cell regeneration.
Background: Tributyltin (TBT) is widely used as an antifouling agent that may cause reproductive toxicity. The mechanism of TBT on Leydig cell development is still unknown. The objective of the present study was to investigate whether a brief exposure to low doses of TBT permanently affects Leydig cell development and to clarify the underlying mechanism.Methods: Adult male Sprague Dawley rats were randomly assigned into four groups and gavaged normal saline (control), 0.1, 1.0, or 10.0 mg/kg/day TBT for a consecutive 10 days, respectively. At the end of TBT treatment, all rats received a single intraperitoneal injection of 75 mg/kg ethane dimethane sulfonate (EDS) to eliminate all of adult Leydig cells. Leydig cells began a developmental regeneration process on post-EDS day 35. The Leydig cell regeneration was evaluated by measuring serum testosterone, luteinizing hormone, and follicle-stimulating hormone levels on post-EDS day 7, 35, and 56, the expression levels of Leydig cell genes, Leydig cell morphology and number and proliferation on post-EDS day 56.Results: TBT significantly reduced serum testosterone levels on post-EDS day 35 and 56 and increased serum luteinizing hormone and follicle-stimulating hormone levels on post-EDS day 56 at ≥1 mg/kg/day. Immunohistochemical staining showed that there were fewer regenerated Leydig cells in the TBT-treated testis on post-EDS day 56. Further study demonstrated that the mRNA or protein levels of Leydig (Lhcgr, Cyp11a1, Hsd3b1, Cyp17a1, and Hsd17b3) and Sertoli cells (Fshr, Dhh, and Sox9) were significantly down-regulated in the TBT-treated testes when compared to the control. Immunofluorescent staining showed that TBT inhibited Leydig cell proliferation as judged by the reduced number of proliferating cyclin nuclear antigen-positive Leydig cells on post-EDS day 35.Conclusion: The present study demonstrated that a short-term TBT exposure blocked Leydig cell developmental regeneration process via down-regulating steroidogenesis-related proteins and inhibiting the proliferation of Leydig cells.
In plants, many small interfering RNAs (siRNAs) direct de novo methylation by DNA methyltransferase. DNA methylation typically occurs by RNA-directed DNA methylation (RdDM), which directs transcriptional gene silencing of transposons and endogenous transgenes. RdDM is driven by non-coding RNAs (ncRNAs) produced by DNA-dependent RNA polymerases IV and V (PolIV and PolV). The production of siRNAs is initiated by PolIV and ncRNAs produced by PolIV are precursors of 24-nucleotide siRNAs. In contrast, ncRNAs produced by PolV are involved in scaffolding RNAs. In this review, we summarize recent studies of RdDM. In particular, we focus on the mechanisms involved in chromatin remodeling by PolIV and PolV.
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