[Mechanism of miR-221-3p inhibiting cadmium-induced apoptosis of TM3 cells through DDIT4].

OBJECTIVE: To investigate the mechanism of DNA-damage-inducible transcript 4(DDIT4)targeting miR-221-3p in microRNA(miRNA) on cadmium-induced apoptosis of mouse testicular stromal cells. METHODS: The activity of mouse testicular interstitial cells(TM3) was detected by CCK-8 after exposure to different concentrations of cadmium(0, 10, 20, 30, 40 µmol/L). Total RNA was extracted from cadmium-treated TM3 cells, and the significantly differentially expressed miRNA was screened with fold change(FC)>1.2 and P<0.05 as the criterion. TM3 cells were divided into blank control group, negative control group, cadmium exposure group(CdCl_2, 20 µmol/L), and cadmium+miR-221-3p mimic group. miR-221-3p mimic group was transfected into TM3 cells first, combined with cadmium exposure for 24 hours. The cell morphology was detected by Hoechst staining, and the apoptosis rate was analyzed by flow cytometry. Quantitative real-time PCR(qRT-PCR) and Western blot were used to detect DDIT4 expression. Dual luciferase reporter gene assay verified the binding of miR-221-3p to DDIT4. The function of DDIT4 and its relationship with apoptosis were analyzed by bioinformatics. The expression levels of B-cell lymphoma-2(Bcl-2) and Bcl-2 associated X protein(BAX) were observed after overexpression of miR-221-3p. RESULTS: Cadmium treatment of TM3 cells could reduce cell activity and there was a dose-effect relationship. The cell morphology showed that compared with the control group, the cells were wrinkled and the nuclei were heavily stained, and the apoptosis rate increased to 19.66%±0.45%(P<0.01). Compared with the cadmium exposure group, the normal morphologic cells increased in the cadmium exposure +miR-221-3p mimic group, and the apoptosis rate decreased to 13.76%±0.37%(P<0.05). The expression level of miR-221-3p was down-regulated(P<0.01), and the expression level of DDIT4 was up-regulated(P<0.05). Bioinformatics analysis and dual luciferase report analysis showed that DDIT4 was one of the target genes of miR-221-3p. Compared with the cadmium exposure group, the expression level of DDIT4 in the cadmium+miR-221-3p mimic group was down-regulated(P<0.05), and the ratio of Bcl-2/BAX was increased from 0.54±0.03 to 0.71±0.04. CONCLUSION: miR-221-3p inhibits cadmium-induced apoptosis of TM3 cells by targeting DDIT4.

[Analysis the mechanism of cadmium-induced cytotoxicity in mouse testicular mesenchymal cells with miRNA transcriptomic].

OBJECTIVE: To analyze the mechanism of cadmium-induced cytotoxicity in mouse testicular mesenchymal cells(TM3) with transcriptome sequencing and bioinformatics techniques. METHODS: TM3 cells were selected as the cell model and divided into control group(no cadmium treatment) and cadmium-treated group(20 µmol/L CdCl_2). After 24 hours of administration, cells were harvested to extract total RNA, and then miRNA expression profiles were obtained by sequencing program after RNA quality detection. The fold change(FC) >2, P<0.05 was used as the standard to screen for differentially expressed miRNAs. The quantitative real-time polymerase chain reaction(qRT-PCR) was used to verify the differentially expressed miRNAs. Then, their target genes were predicted by miRanda software to construct miRNA-target gene interaction network, and their target genes were enriched by gene ontology(GO) and Kyoto encyclopedia of genes and genomes(KEGG) pathway function. RESULTS: A total of 26 differentially expressed miRNAs were identified which may be related to cadmium-induced TM3 cytotoxicity, including 19 up-regulated and 7 down-regulated miRNAs. The result of qRT-PCR were consistent with the miRNA sequencing result. Meanwhile, bioinformatics analysis result showed that the 26 differentially expressed miRNAs predicted 657 target genes. GO enrichment was mainly classified into biological regulation, metabolic process, protein binding and catalytic activity. KEGG pathway analysis showed that target genes were significantly involved in mitogen-activated protein kinase(MAPK) and tumor necrosis factor(TNF) signal pathways closely related to inflammatory response and apoptosis. CONCLUSION: Cadmium can lead to the differential expression of miRNAs in TM3 cells, and its target genes may be involved in Cd-induced TM3 cytotoxicity through signaling pathways such as MAPK and TNF.

[N-acetylcysteine alleviates cadmium-induced testicular interstitial cell apoptosis by activating protein kinase B pathway].

OBJECTIVE: To investigate the regulation mechanism of N-acetylcysteine(NAC) on cadmium-induced apoptosis of mouse testicular interstitial cells based on protein kinase B pathway(AKT pathway). METHODS: Mouse testicular mesenchymal cells(TM3) were divided into fourgroups according to different treatment, control group, cadmium group(Cd, 5, 10, 20, 30, 40 and 50 µmol/L), NAC group(NAC, 500 µmol/L) and NAC+Cd group(500 µmol/L NAC+20 µmol/L Cd). Cells of NAC+Cd group were pretreated with NAC for 30 min, and then combined with cadmium for 24 h. Cell viability was determined by CCK8. Hoechst staining was used to determine cell morphology. Cell apoptosis rate was analyzed by flow cytometry. Malondialdehyde(MDA) and glutathione(GSH) were measured simultaneously. Western blot was used to detect the expression levels of AKT protein, B-cell lymphoma-2(Bcl-2) and Bcl-2 associated X protein(Bax). RESULTS: Cadmium inhibited the proliferation of TM3 cells in a dose-effect relationship. Cell morphology observation showed that with the increase of cadmium concentration, the cells shrank, became round and even fell off, and appeared dense nuclear staining. The MDA level in Cd group was(1.56±0.11) µmol/mg prot, which was significantly higher than that in control group(P<0.01). Compared to the control group, the level of GSH was significantly decreased to(1.28±0.25) µmol/mg prot(P<0.01). NAC pretreatment could reduce the MDA content and increase the GSH level, and the difference was statistically significant compared with the Cd group(P<0.01). Western blot result showed that NAC pretreatment significantly increased levels of phosphorylated AKT and Bcl-2, the levels were 0.65±0.05 and 0.45±0.03, respectively(P<0.01). The Bax/Bcl-2 ratio was 1.54±0.15, which was significantly lower than that of the Cd group(P<0.01). CONCLUSION: NAC can inhibit cadmium-mediated TM3 cell damage and apoptosis, which may be related to the improvement of oxidative stress state, activation of TM3 AKT pathway and reduction of Bax/Bcl-2 ratio.

Nano-selenium Alleviates Cadmium-Induced Mouse Leydig Cell Injury, via the Inhibition of Reactive Oxygen Species and the Restoration of Autophagic Flux.

Cadmium (Cd) is a well-known environmental pollutant that can contribute to male reproductive toxicity through oxidative stress. Nano-selenium (Nano-se) is an active single body of selenium with strong antioxidant properties and low toxicity. Some studies have addressed the potential ameliorative effect of Nano-se against Cd-induced testicular toxicity; however, the underlying mechanisms remain to be investigated. This study aimed to explore the protective effect of Nano-se on Cd-induced mouse testicular TM3 cell toxicity by regulating autophagy process. We showed that cadmium exposure to TM3 cells inhibited cell viability and elevated the level of reactive oxygen species (ROS) generation. Morphology observation by transmission electron microscope and the presence of mRFP-GFP-LC3 fluorescence puncta demonstrated that cadmium increased autophagosome formation and accumulation in TM3 cells, resulting in blocking the autophagic flux of TM3 cells. Meanwhile, cadmium remarkably increased the ratio of LC3-II to LC3-I protein expression (2.07 ± 0.31) and the Beclin-1 protein expression (1.97 ± 0.40) in TM3 cells (P < 0.01). Pretreatment with Nano-se significantly reduced Cd-induced TM3 cell toxicity (P < 0.01). Furthermore, Nano-se treatment reversed Cd-induced ROS production and autophagosome accumulation, and autophagy as evidenced by the ratio of LC3-II to LC3-I and Beclin-1 expression. In addition, ROS scavenger, N-acetyl-L-cysteine (NAC) or autophagy inhibitor, 3-methyladenine (3-MA) reversed cadmium-induced ROS generation, autophagosome accumulation, and autophagy-related protein expression levels, which confirmed that cadmium induced TM3 cell injury via ROS signal pathway and blockage of autophagic flux. Collectively, our results reveal that Nano-se attenuates Cd-induced TM3 cell toxicity through the inhibition of ROS production and the amelioration of autophagy disruption.