[Role of autophagy in cadmium-induced damage to the blood-testis barrier in mice].

OBJECTIVE: To investigate the role of autophagy in cadmium chloride (CdCl2)-induced damage to the blood-testis barrier (BTB) in mice. METHODS: Twenty four-week-old male C57BL/6 mice were randomly divided into four groups and intraperitoneally injected with CdCl2 at 0 mg/kg/d (the control), 0.5 mg/kg/d (low-dose), 1.0 mg/kg/d (medium-dose) and 2.0 mg/kg/d (high-dose) respectively for 28 consecutive days. Then the morphological changes of the testis tissue was observed by HE staining, the integrity of BTB measured with the biotracer, and the expressions of the BTB components ZO-1 and N-Cadherin proteins detected by Western blot. The TM4 Sertoli cells were treated with CdCl2at 0, 2.5, 5 and 10 µmol/L respectively for 24 hours, followed by determination of the expression levels of ZO-1 and N-Cadherin as well as the autophagy-related proteins LC3II and p62. Then the cells were again treated with CdCl2 in the presence of the autophagy inhibitor chloroquine (CQ) at 5 µmol/L or the autophagy inducer rapamycin (Rap) at 50 nmol/L for 24 hours, followed by measurement of the expressions of LC3II, p62, ZO-1 and N-Cadherin by Western blot. RESULTS: Compared with the control group, the cadmium-exposed mice showed increased interstitial space in the seminiferous tubules, formation of intracellular cavitation in the germ cells with decreased layers and disordered arrangement, and damaged integrity of the BTB. The expressions of the ZO-1 and N-Cadherin proteins were significantly down-regulated in the testis tissue of the mice in the medium- and high-dose CdCl2 groups (P < 0.05), and even more significantly in the CdCl2-exposed cells in comparison with those in the control mice (P < 0.01), while the expressions of the LC3II and p62 proteins were remarkably up-regulated (P < 0.05). The expressions of ZO-1, N-Cadherin, LC3II and p62 were also up-regulated in the cells co-treated with CQ and CdCl2 (P < 0.01), those of ZO-1, N-Cadherin and p62 down-regulated (P< 0.05) and that of LC3II up-regulated (P < 0.05) in the cells co-treated with Rap and CdCl2. CONCLUSION: CdCl2 can damage the integrity of the mouse BTB, which may be attributed to its ability to enhance the autophagy in Sertoli cells and regulate the expressions of BTB proteins.

[HFD-induced obesity triggers testicular cell senescence and endoplasmic reticulum stress in male mice].

OBJECTIVE: To investigate high-fat diet-induced obesity-triggered testicular cell senescence and endoplasmic reticulum stress. METHODS: We randomly and equally divided 10 four-week-old male C57BL/6J mice into a control and a high-fat group, the former fed with a diet of 10% fat content while the latter with a diet of 60% fat content to establish an obesity model. After eight weeks of feeding, we observed the pathological changes in the testis tissue of the mice by HE staining, detected the serum T content by ELISA, measured the telomere length in the testis cells by RT-PCR, and examined the activity of senescence-associated ß-galactosidase (SA-ß-gal) by histochemical staining. Using RT-qPCR and Western blot, we determined the protein and mRNA expressions of the cell senescence markers p16 and p21 as well as the protein expressions of the endoplasmic reticulum stress markers GRP78 and CHOP in the testis tissue. RESULTS: Compared with the controls, the animals of the high-fat group showed a 45% increase in the body weight, disordered structure of the spermatogenic cells, reduced level of serum T and shortened telomere length of the testis cells (P < 0.01). The mRNA and protein expressions of p16 and p21 were dramatically higher in the high-fat than in the control group (P<0.01), so were the intracellular SA-ß-gal activity and the protein expressions of CHOP and GRP78 (P<0.01). CONCLUSION: High-fat diet-induced obesity triggers testicular cell senescence and endoplasmic reticulum stress in male mice.

[Effects of down-regulating Spag6L expression on the proliferation and apoptosis of mouse spermatocytes].

OBJECTIVE: To explore the expression of the Spag6L gene during spermatogenesis and the effects of Spag6L silencing on the proliferation and apoptosis of mouse GC-2 spd cells. METHODS: Using reverse-transcription PCR and real-time qPCR, we detected the expression of the Spag6L gene in the testis tissue collected from the mice at 8, 16, 20, 28 and 42 postnatal days. We prepared lentiviral particles inhibiting the expression of Spag6L and transfected them into the GC-2 spd cells. Then we screened the stably transfected cell lines with the Spag6L expression effectively down-regulated by real-time qPCR, analyzed the effects of Spag6L silencing on the proliferation, activity, cell cycle and apoptosis of the GC-2 spd cells by cell counting and flow cytometry, and on the expression levels of pro-apoptotic Bax and anti-apoptotic Bcl-2 by Western blot. RESULTS: The Spag6L gene was slightly expressed in the testis tissue of the mice at 8 postnatal days and gradually up-regulated with the development of the testis. Inhibition of the Spag6Lexpression significantly decreased the activity of the GC-2 spd cells (P < 0.01), leading to cell arrest in the G1 phase. The expression of the Bax protein was dramatically up-regulated (P < 0.01) while that of Bcl-2 remarkably down-regulated (P < 0.01) in the Spag6L shRNA- transfected cells, inducing the apoptosis of the cells. CONCLUSIONS: The Spag6L gene is involved in the spermatogenesis of mice by regulating the cell cycle, proliferation and apoptosis of spermatocytes.

[The role of SPAG6/SPINK2 protein complex in the formation of sperm acrosome in mice].

OBJECTIVE: To explore the expression and regulatory function of sperm-associated antigen 6 (SPAG6) in the formation of the sperm acrosome in mice. METHODS: The expression of SPAG6 during the first wave of spermatogenesis on postnatal days (PN) 8, 12, 16, 20, 24, 28, 30 and 35 was examined by Western blot and the localization of SPAG6 in the testicular germ cells was determined by immunofluorescence. The expression plasmids of SPAG6 and serine protease inhibitor Kazal-type 2 (SPINK2) were constructed, the interaction between SPAG6 and SPINK2 in the AH109 and CHO cells examined by yeast two-hybrid and co-localization assays, and the expression and localization of SPINK2 in the testicular germ cells of the SPAG6-knockout (SPAG6 KO) mice detected by immunofluorescence. RESULTS: SPAG6 was highly expressed between PN 16 and 28 and localized in the acrosome of the round spermatids. Yeast two-hybrid assay showed the growth of SPAG6 and SPINK2 in the selective culture medium SD/-Leu/-Trp/-His, and the transfection of the CHO cells revealed the co-localization of SPAG6 and SPINK2 around the nuclei. The expression and acrosomal localization of SPINK2 were not found in the testicular germ cells of the SPAG6-KO mice. CONCLUSIONS: SPAG6 interacts with SPINK2 and probably participates in the formation of the sperm acrosome by stabilizing the expression of SPINK2 during spermatogenesis.

[Interaction between SPAG6 and TAC1 proteins].

OBJECTIVE: To construct eukaryotic expression plasmids of the Tac1 gene and explore the interaction between TAC1 and sperm-associated antigen 6 (SPAG6). METHODS: RNA was extracted from the heart, liver, spleen, lung, kidney, brain, muscle, and testis of 10 Kunming male mice and, after reverse transcription into cDNA, the expression of Tac1 in the above tissues was observed by RT-PCR. Tac1/pEGFP-N2 and Tac1/pGADT7 recombinant plasmids were constructed and Tac1/pEGFP-N2 was transfected into CHO and COS-1 cells, followed by localization and detection of the protein expression of TAC1 by immunofluorescence staining and Western blot. The interaction between TAC1 and SPAG6 was determined by yeast two-hybrid experiment and Western blot. RESULTS: Tac1 was expressed mainly in the testis, brain and heart. The results of restriction enzyme digestion and sequencing indicated successful construction of the recombinant plasmids, with the restriction fragment length of 390 bp. TAC1 was localized in the whole body of the CHO cells when transfected alone, but expressed in the microtubule of the cells when cotransfected with SPAG6, with the molecular weight of 40 000. Yeast two-hybrid experiment showed the colonies of TAC1 and SPAG6 on the culture plate without Leu, Trp and His, both contained in the yeast fusion protein. CONCLUSIONS: The Tac1 recombinant plasmid was constructed successfully and the interaction between TAC1 and SPAG6 was confirmed with the plasmid.

CbrAB-dependent regulation of pcnB, a poly(A) polymerase gene involved in polyadenylation of RNA in Pseudomonas fluorescens.

CbrB is a global sigma(54)-dependent regulator required for nutrient acquisition in Pseudomonas. Located downstream of cbrB on the Pseudomonas fluorescens SBW25 chromosome is pcnB, a putative poly(A) polymerase gene. Presence of a sigma(54) promoter in the intergenic region of cbrB and pcnB led to the hypothesis that CbrB regulates pcnB expression in a sigma(54)-dependent manner. Here we show that transcription of pcnB is CbrB dependent. However, 5'-RACE analysis of the pcnB transcript using primers located in the pcnB coding region shows that transcription starts immediately upstream of the putative ATG site at a sigma(70)-like promoter. Deletion of pcnB caused approximately 80% decrease of ployadenylated 23S rRNA; growth of the pcnB mutant was compromised in a range of laboratory media and on sugar beet seedlings. Further 5'-RACE analysis confirmed the existence of the predicted sigma(54) promoter. Genetic analysis showed that the sigma(54) promoter drives expression of crcZ, a homologue of the recently described small RNA from Pseudomonas aeruginosa, in a CbrB-dependent manner. Taken together, our data show that both pcnB and crcZ are part of the CbrB regulon. Moreover, the data draw further attention to the central regulatory role of CbrB and provides a link between mRNA degradation and cellular catabolism.