Fluorochloridone induces autophagy in TM4 Sertoli cells: involvement of ROS-mediated AKT-mTOR signaling pathway

Background Fluorochloridone (FLC), a selective pyrrolidone herbicide, has been recognized as a potential endocrine disruptor and reported to induce male reproductive toxicity, but the underlying mechanism is unclear. The aim of this study was to investigate the mechanism of FLC-induced reproductive toxicity on male mice with particular emphasis on the role of autophagy in mice' TM4 Sertoli cells. Methods Adult C57BL/6 mice were divided into one control group (0.5% sodium carboxymethyl cellulose), and four FLC-treated groups (3,15,75,375 mg/kg). The animals (ten mice per group) received gavage for 28 days. After treatment, histological analysis, sperm parameters, the microstructure of autophagy and the expression of autophagy-associated proteins in testis were evaluated. Furthermore, to explore the autophagy mechanism, TM4 Sertoli cells were treated with FLC (0,40,80,160 mu M) in vitro for 24 h. Cell activity and cytoskeletal changes were measured by MTT assay and F-actin immunofluorescence staining. The formation of autophagosome, accumulation of reactive oxygen species (ROS), expression of autophagy marker proteins (LC3, Beclin-1 and P62) and AKT-related pathway proteins (AKT, mTOR) were observed. The ROS scavenger N-acetylcysteine (NAC) and AKT agonist (SC79) were used to treat TM4 cells to observe the changes of AKT-mTOR pathway and autophagy. Results In vivo, it showed that FLC exposure caused testicular injuries, abnormality in epididymal sperm. Moreover, FLC increased the formation of autophagosomes, the accumulation of LC3II/LC3I, Beclin-1 and P62 protein, which is related to the degradation of autophagy. In vitro, FLC triggered TM4 cell autophagy by increasing the formation of autophagosomes and upregulating of LC3II/LC3I, Beclin-1 and P62 levels. In addition, FLC induced ROS production and inhibited the activities of AKT and mTOR kinases. The Inhibition of AKT/mTOR signaling pathways and the activation of autophagy induced by FLC could be efficiently reversed by pretreatment of NAC. Additionally, decreased autophagy and increased cell viability were observed in TM4 cells treated with SC79 and FLC, compared with FLC alone, indicating that FLC-induced autophagy may be pro-death. Conclusion Taken together, our study provided the evidence that FLC promoted autophagy in TM4 Sertoli cells and that this process may involve ROS-mediated AKT/mTOR signaling pathways.

Automated summary

This study investigated the mechanism of FLC-induced reproductive toxicity in male mice, focusing on the role of autophagy in TM4 Sertoli cells. FLC exposure caused testicular injuries and increased autophagosome formation, ROS accumulation, and autophagy marker protein expression. In vitro, FLC triggered autophagy in TM4 cells by upregulating autophagosome formation and marker protein levels, while inhibiting AKT/mTOR signaling pathways. NAC and SC79 treatments reversed the effects of FLC-induced autophagy and increased cell viability in TM4 cells.