Involvement of IGF-I signaling pathway in the regulation of steroidogenesis in mouse Leydig cells treated with fenvalerate

DEHP-induced testicular injury through gene methylation pathway and the protective effect of soybean isoflavones in Sprague-Dawley rats

As one of the most important members of Phthalate esters (PAEs), di-(2-ethylhexyl) phthalate (DEHP) is widely used in plastics and known as a male reproductive toxicant. Many studies have shown that soybean isoflavones (SI) can rescue the testicular injury caused by DEHP, but the underlying mechanism is unknown. Because methylation is one of the most important mechanisms for maintaining normal biological functions, we studied whether methylation is involved in testicular injury induced by DEHP and whether SI could counter testicular impairment in peripubertal male Sprague Dawley rats. Compared with the control group, we found that the mRNA levels of testicular Sod2, Gpx1, and Igf-1 significantly decreased in the 900 mg/kg DEHP group (DEHP' group) (P < 0.01); however, in the DEHP + SI group, the mRNA levels of the genes obviously increased compared with the DEHP' group (P < 0.01). Simultaneously, the methylation level changes of testicular Sod2, Gpx1, and Igf-1 were similar to the mRNA levels (P < 0.01). Therefore, DEHP may affect testis and leydig cells via inducing methylation of Sod2, Gpx1, and Igf-1, and SI may rescue the impairments at the methylation level. In summary, SI is supposed to be used in DEHP-induced testicular injury treatment.

Effects of pyrethroid insecticides on hypothalamic-pituitary-gonadal axis: A reproductive health perspective

Pyrethroids, a class of ubiquitous insecticides, have been recognized as endocrine-disrupting chemicals (EDCs). A lot of studies have implied the endocrine-disrupting effects of pyrethroids on the hypothalamic-pituitary-gonadal (HPG) axis. However, there are few review articles regarding the effects of pyrethroids on the HPG axis of mammal and human, especially new research progress made in this area. The present review sums up the effects of pyrethroids on the HPG axis-related reproductive outcomes, including epidemiological investigations based on human biomonitoring, animal studies and in vitro tests. Mechanisms have described that the endocrine-disrupting effects of pyrethroids on mammal can be mediated via the interaction with steroid receptors, the direct action on ion channels and signaling molecules. Finally, we summarize the current research gaps and suggest future directions in this topic.

Sequential testicular atrophy involves changes in cellular proliferation and apoptosis associated with variations in aromatase P450 expression levels in Irs-2-deficient mice

Insulin receptor substrate 2 (Irs-2) is an intracellular protein susceptible to phosphorylation after activation of the insulin receptor. Its suppression affects testis development and its absence induces peripheral resistance to insulin. The aim of this study was to identify changes induced by the deletion of Irs-2 in the testicular structure and by the altered expression of cytochrome P450 aromatase, a protein necessary for the development and maturation of germ cells. Adult knockout (KO) mice (Irs-2^-/- , 6 and 12 weeks old) and age-matched wild-type (WT) mice were used in this study. Immunohistochemistry and Western blot analyses were performed to study proliferation (PCNA), apoptosis (active caspase-3) and P450 aromatase expression in testicular histological sections. Deletion of Irs-2 decreased the number of epithelial cells in the seminiferous tubule and rete testis. Aberrant cells were frequently detected in the epithelia of Irs-2^-/- mice, accompanied by variations in spermatogonia, which were shown to exhibit small hyperchromatic nuclei as well as polynuclear and anuclear structures. The amount of cell proliferation was significantly lower in Irs-2^-/- mice than in WT mice, whereas apoptotic processes were more common in Irs-2^-/- mice. Aromatase P450 reactivity was higher in 6-week-old KO mice than in WT mice of the same age and was even higher at 12 weeks. Our results suggest that Irs-2 is a key element in spermatogenesis because silencing Irs-2 induces the sequential development of testicular atrophy. The effects are observed mainly in germ cells present in the seminiferous tubule, which may be due to changes in cytochrome P450 aromatase expression.

Differentiation of human umbilical cord mesenchymal stem cells into steroidogenic cells in vitro

Although previous studies have shown that stem cells can be differentiated into Leydig cells by gene transfection, a simple, safe and effective induction method has not yet been reported. Therefore, the present study investigated novel methods for the induction of human umbilical cord mesenchymal stem cell (HUMSC) differentiation into Leydig-like, steroidogenic cells. HUMSCs were acquired using the tissue block culture attachment method, and the expression of MSC surface markers was evaluated by flow cytometry. Leydig cells were obtained by enzymatic digestion and identified by lineage-specific markers via immunofluorescence. Third-passage HUMSCs were cultured with differentiation-inducing medium (DIM) or Leydig cell-conditioned medium (LC-CM), and HUMSCs before induction were used as the control group. Following the induction of HUMSCs, Leydig cell lineage-specific markers (CYP11A1, CYP17A1 and 3β-HSD) were positively identified using immunofluorescence analysis. Additionally, reverse transcription-quantitative polymerase chain reaction and western blot analysis were performed to evaluate the expression levels of these genes and enzymes. In contrast, the control group cells did not show the characteristics of Leydig cells. Collectively, these results indicate that, under in vitro conditions, LC-CM can achieve a comparable effect to that of DIM on inducing HUMSCs differentiation into steroidogenic cells.

Allethrin induced toxicity in the male reproductive tract of rats contributes to disruption in the transcription of genes involved in germ cell production

Pyrethroids are known to be neurotoxic. However, their toxic effects including that of allethrin on the male reproductive tract are not elucidated. Adult male rats were treated orally with 25, 50, 100, and 150 mg/kg body weight allethrin every day for 60 days. Lipid peroxidation was increased (p < 0.001) in the caput, cauda, and testes. Nitric oxide production was increased (p < 0.001) in the caput, but unaltered in the cauda and testes. The activities of catalase, glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase were decreased in the caput and cauda where as a decrease was observed in the testis obtained from allethrin treated rats. In the epididymides and testes, damage to tubular architecture, congestion, degeneration of epithelial cell lining, intestinal edema, and presence of dead or degenerating spermatids were observed in a dose dependent manner. The expression profile of genes involved in spermatogenesis (Tgf-beta1), sperm maturation (Spag11e), and sperm function (Defb22) were reduced (p < 0.001) in allethrin rats. The expression of p53 gene was decreased and increased phosphorylation of MAPK (p42/p44) expression was observed the male reproductive tract tissues of allethrin treated rats. Although earlier studies have reported the effects of allethrin inhalation because of the use of mosquito coils and vaporizers, our results for the first time prove that oral exposure to allethrin could affect fertility and may contribute to deregulation of cell cycle in the male reproductive tract.