Is thioredoxin reductase involved in the defense against DNA fragmentation in varicocele?

Abstract

We aimed to investigate the role of thioredoxin reductase (TR) and inducible heat shock protein 70 (iHsp70) and their relationship with sperm quality in varicocele (VAR) patients. Semen samples were obtained from 16 subfertile men diagnosed as VAR and 10 fertile men who applied to the Andrology Laboratory of Istanbul Medical Faculty of Istanbul University. The sperm TR and iHsp 70 expression levels were determined using Western blot analysis. The TR activity of the sperm was assayed spectrophometrically. The sperm quality was evaluated both by conventional sperm analysis and by a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) technique that assayed DNA-fragmented spermatozoa in semen samples. The percentage of TUNEL-positive spermatozoa in the VAR group (16.3%± 5.6%) was higher than that in the fertile group (5.5%± 1.9%). Significant inverse correlations were detected between the percentage of TUNEL-positive cells and both the concentration (r=-0.609; P=0.001) and motility (r=-0.550; P=0.004) of spermatozoa. Both the TR expression and activity were increased significantly in the VAR group (U=22.0; P=0.001 and U=33.5; P=0.012, respectively) as analyzed using the Mann-Whitney U Wilcoxon rank sum W test. Furthermore, significant positive correlations were found between TR expression and activity (r=0.406; P=0.040) and between TR expression and the percentage of TUNEL-positive cells (r=0.665; P=0.001). Sperm iHsp70 expression did not differ between the VAR and fertile groups. In conclusion, increased sperm TR expression might be a defense mechanism against apoptosis in the spermatozoa of men with VAR.

Figure 1

Examples of the expression profiles of TR, iHsp70 and α-tubulin of the spermatozoa from the fertile (a) and VAR (b) groups. The band intensities on the Western blots (TR and iHsp70) were normalized to α-tubulin as an internal standard. The values were expressed arbitrarily by comparison with a fertile sample (as a control) which was run in the first lane for each assay performed. iHsp70, inducible heat shock protein 70; TR, thioredoxin reductase; VAR, varicocele.

Figure 2

Positive correlation between TR activity and TR expression. TR, thioredoxin reductase.

Figure 3

Positive correlation between the TUNEL results and TR expression. TR, thioredoxin reductase; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling.

Figure 4

Examples of TUNEL microphotographs from the fertile (a) and VAR (b) groups. TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling; VAR, varicocele.