Jialiu Wei

Silica nanoparticles induce reversible damage of spermatogenic cells via RIPK1 signal pathways in C57 mice.

The reproductive toxicity of silica nanoparticles (SiNPs) is well known, but the underlying mechanism is still not clear. To investigate the toxic mechanism of SiNPs on spermatogenic cells, 60 C57 male mice were randomly and equally divided into three groups (the control group, the saline control group, and the SiNPs group) with two observed time points (45 days and 75 days). The mice in the SiNPs group were administered with SiNPs 2 mg/kg diluted in normal saline, and the mice of the saline control group were given equivoluminal normal saline by tracheal perfusion every 3 days for 45 days (in total 15 times). The control group mice were bred without treatment. In each group, a half number of the mice were sacrificed on the 45th day after the first dose, and the remaining half were sacrificed on the 75th day. The results showed that SiNPs increased the malformation of sperms and decreased the motility and concentration of sperms in epididymis on the 45th day after the first dose. SiNPs induced oxidative stress in testis and led to apoptosis and necroptosis of the spermatogenic cells. Furthermore, SiNPs increased the expression of Fas/FasL/RIPK1/FADD/caspase-8/caspase-3 and RIPK3/MLKL on the 45th day after the first dose. However, compared with the saline control group, the index of sperms and the expression of Fas/FasL/RIPK1/FADD/caspase-8/caspase-3/RIPK3/MLKL showed no significant changes in the SiNPs group on the 75th day after the first dose. These data suggested that SiNPs could induce apoptosis and necroptosis in the spermatogenic cells by activating the RIPK1 pathway resulting from oxidative stress in male mice. SiNPs-induced damage recovered on the 75th day after the first dose, which suggested that SiNPs-induced toxicity is reversible.

Endosulfan induced the arrest of the cell cycle through inhibiting the signal pathway mediated by PKC-α and damaging the cytoskeleton in spermatogonial cells of mice in vitro

Previous studies have shown that endosulfan has adverse effects on the male reproductive system and the oxidative stress induced by endosulfan is related to its toxicity. However, the molecular mechanism of endosulfan reproductive toxicity is still unknown. To investigate its mechanism of toxicity, GC-1spg cells were exposed to 0, 6, 12 and 24 μg mL−1 endosulfan for 24 h, respectively. The results showed that endosulfan resulted in a dose-dependent reduction in cell viability and increases in the LDH release, apoptosis rate, malondialdehyde (MDA) level, reactive oxygen species (ROS) production and degree of DNA damage including the percentage of tail DNA, tail length, tail moment (TM) and Olive tail moment (OTM). Endosulfan induced the arrest of both S and G2/M phases and proliferation inhibition. The expression of PKC-α, CDK2, cyclin E, RAF-1, MEK1/2, p-MEK1/2, ERK1/2 and p-ERK1/2 in GC-1spg cells declined remarkably after treatment with endosulfan. Endosulfan also damaged the microfilaments, microtubules and cell nuclei, and blocked the mitosis process. The results suggested that endosulfan could induce the cell cycle arrest and proliferation inhibition by inhibiting the protein expression of the cellular signaling pathway mediated by PKC-α because of DNA damage resulting from oxidative stress; meanwhile, endosulfan could also lead to mitotic arrest through direct damage to the cytoskeleton and cell nuclei resulting from oxidative stress, which therefore induced cytotoxicity of GC-1spg cells.

Endosulfan inducing blood hypercoagulability and endothelial cells apoptosis via the death receptor pathway in Wistar rats

To investigate the effects of endosulfan on coagulation status and its mechanism, 32 male Wistar rats were randomly divided into four groups, including a control solution and three concentrations of endosulfan groups (1, 5, 10 mg kg−1 per day). The results showed that endosulfan significantly promoted platelet aggregation, prolonged the thrombin time and increased the D-dimer level, and decreased antithrombin III activity and the fibrinogen level. It also significantly enhanced the plasma levels of ROS and vWF, increased the expressions of 8-OHdG and apoptosis positive cells in the endothelial cells and promoted the expressions of Fas, FasL, caspase-8, and caspase-3 in vascular endothelial cells. The results suggested that endosulfan could cause the hypercoagulability of blood by promoting both platelet aggregation and the transformation of fibrinogen into fibrin, as well as depressing antithrombin III activity. Furthermore, endosulfan could induce the dysfunction of endothelial cells by causing apoptosis via a death receptor pathway, resulting from oxidative stress, which could be one of the key mechanisms behind hypercoagulability induced by endosulfan.

Endosulfan induces cell dysfunction through cycle arrest resulting from DNA damage and DNA damage response signaling pathways

Our previous study showed that endosulfan increases the risk of cardiovascular disease. To identify toxic mechanism of endosulfan, we conducted an animal study for which 32 male Wistar rats were randomly and equally divided into four groups: Control group (corn oil only) and three treatment groups (1, 5 and 10mgkg-1·d-1). The results showed that exposure to endosulfan resulted in injury of cardiac tissue with impaired mitochondria integrity and elevated 8-OHdG expression in myocardial cells. Moreover, endosulfan increased the expressions of Fas, FasL, Caspase-8, Cleaved Caspase-8, Caspase-3 and Cleaved Caspase-3 in cardiac tissue. In vitro, human umbilical vein endothelial cells (HUVECs) were treated with different concentrations of endosulfan (1, 6 and 12μgmL-1) for 24h. An inhibitor for Ataxia Telangiectasia Mutated Protein (ATM) (Ku-55933, 10μM) was added in 12μgmL-1 group for 2h before exposure to endosulfan. Results showed that endosulfan induced DNA damage and activated DNA damage response signaling pathway (ATM/Chk2 and ATR/Chk1) and consequent cell cycle checkpoint. Furthermore, endosulfan promoted the cell apoptosis through death receptor pathway resulting from oxidative stress. The results provide a new insight for mechanism of endosulfan-induced cardiovascular toxicity which will be helpful in future prevention of cardiovascular diseases induced by endosulfan.

Fine particle matter disrupts the blood-testis barrier by activating TGF-β3/p38 MAPK pathway and decreasing testosterone secretion in rat

Fine particle matter (PM) is correlated with male reproductive dysfunction in animals and humans, but the underlying mechanisms remain unknown. To investigate the toxic mechanism of PM, 32 male Sprague‐Dawley (SD) rats were exposed to saline or PM2.5 with the doses of 1.8, 5.4, and 16.2 mg/kg.b.w. via intratracheal instillation, respectively, one time every 3 days, in total times for 30 days. Sperm concentration, hormone level, the expressions of BTB‐associated protein and the mitogen‐activated protein kinase (MAPK) pathway, tumor necrosis factor α and transforming growth factor β3 levels were detected. The results showed a decrease in sperm number, testosterone and luteinizing hormone levels and altered ultrastructure of BTB in testis of rat after exposure to PM2.5. The protein levels of N‐Cadherin, Occludin, Claudin‐11, and Connexin‐43 were significantly decreased in the testes. TGF‐β3 content in testes showed increase, with the p‐p38/p38 MAPK ratio also increasing after PM2.5 exposure. These results demonstrate that PM2.5 restrained the expressions of BTB‐associated proteins through activating TGF‐β3/p38 MAPK pathway and decreasing testosterone secretion, and therefore lead to the damage of BTB resulting in the decrease of sperm quality, which might be the potential reasons for its negative effects on spermatogenesis and male reproduction.

PM2.5 induces male reproductive toxicity via mitochondrial dysfunction, DNA damage and RIPK1 mediated apoptotic signaling pathway.

Recent years, air pollution has been a serious problem, and PM2.5 is the main air particulate pollutant. Studies have investigated that PM2.5 is a risky factor to the deterioration of semen quality in males. But, the related mechanism is still unclear. To explore the effect of PM2.5, Sprague Dawley (SD) rats were exposed to PM2.5 (0, 1.8, 5.4 and 16.2mg/kg.bw.) through intratracheal instillation. The exposure was performed once every 3days and continued for 30days. In vitro, GC-2spd cells were treated using 0, 50, 100, 200μg/mL PM2.5 for 24h. The data showed that sperm relative motility rates and density were remarkably decreased, while sperm malformation rates were significantly increased with exposure to the PM2.5. The expression of Fas/FasL/RIPK1/FADD/Caspase-8/Caspase-3 and the level of 8-OHdG expression in testes were significantly increased after exposure to PM2.5. Additionally, in vitro the results showed that PM2.5 inhibited cell viability, increased the release of lactate dehydrogenase (LDH) by increasing reactive oxygen species (ROS) level. And ROS induced-DNA damage led to cell cycle arrest at G0/G1 phases and proliferation inhibition. Similar to the vivo study, the expressions of Fas/FasL/RIPK1/FADD/Caspase-8/Caspase-3 in GC-2spd cells were significantly increased after exposure to PM2.5 for 24-h. In addition, PM2.5 decreased the levels of ATP by impairing mitochondria structures, which led to energy metabolism obstruction resulted in the decrease of sperm motility. The above three aspects together resulted in the decrease in sperm quantity and quality.

Silica nanoparticles induce abnormal mitosis and apoptosis via PKC-δ mediated negative signaling pathway in GC-2 cells of mice

The potential health hazards of silica nanoparticles (SiNPs) have attracted more and more attentions. Researches had shown that SiNPs could damage seminiferous epithelium and reduce the quantity and quality of sperms, however the specific mechanism of male reproductive toxicity induced by SiNPs still unclear. So we designed to investigate the mechanism of SiNPs on male mice using spermatocyte lines (GC-2spd cells) after exposure to SiNPs (6.25, 12.5, 25 and 50 μg/mL) for 24 h. The present study showed that SiNPs entered GC-2 cells and mainly localized in the cytoplasm and lysosome. And internalized SiNPs damaged mitochondria structures. As a result, SiNPs not only induced a dose-dependent reduction in cell viability, but also increased the LDH release and apoptosis rate in GC-2 cells. Furthermore, SiNPs induced DNA strand breaks and abnormal mitosis, and arrested GC-2 cells at the G0/G1 phase. Besides, SiNPs could simultaneously activate both PKC-mediated negative signaling pathway (PKC-δ/p53/p21cip1) and positive signaling pathway (PKC-α/MAPK). However, the lower expressions of cyclin E and cyclin-dependent kinases 2 (CDK2) indicated that PKC-δ signaling pathway played a major role in cell cycle process. These results suggested internalized SiNPs in GC-2 cells induced DNA strand breaks and activated PKC-mediated signaling pathway. While the activation of PKC-δ signaling pathway led to cell cycle arrest and apoptosis, thereby resulting in abnormal mitosis. The present study may provide a new evidence to elucidate the toxic mechanisms of male reproductive system, and will be beneficial for safety assessment of SiNPs products.