Cyclophilin A is present in rat germ cells and is associated with spermatocyte apoptosis. Reproductive Toxicology Group

Novel regulators of spermatogenesis

Spermatogenesis is a multistep process that supports the production of millions of sperm daily. Understanding of the molecular mechanisms that regulate spermatogenesis has been a major focus for decades. Yet, the regulators involved in different cellular processes of spermatogenesis remain largely unknown. Human diseases that result in defective spermatogenesis have provided hints on the molecular mechanisms regulating this process. In this review, we have summarized recent findings on the function and signaling mechanisms of several genes that are known to be associated with disease or pathological processes, including CFTR, CD147, YWK-II and CT genes, and discuss their potential roles in regulating different processes of spermatogenesis.

Evaluation of potential protein biomarkers in patients with high sperm DNA damage

The laboratory evaluation of male infertility remains an essential area of research as 40-60% of infertility cases are attributable to male-related factors. Current sperm analysis methods add only partial information on sperm quality and fertility outcomes. The specific underlying cause of infertility in most cases is unknown, while a proportion of male infertility could be caused by molecular factors such as the absence or abnormal expression of some essential sperm proteins. The objective of this study was to screen for associations between sperm protein profiles and sperm concentration, motility, and DNA fragmentation index in patients undergoing fertility evaluation in a clinical setting. Based on those parameters, semen samples were categorized as either normal or abnormal. We screened 34 semen samples with various abnormal parameters and compared them to 24 normal control samples by using one dimensional (1-D) gel electrophoresis and mass-spectrometry. In this study, we anticipated to establish a normal sperm parameter profile which would be compared to abnormal sperm samples and reveal candidate proteins. Our preliminary results indicate that no normal uniform profile could be established, which affirms the complexity of male fertility and confirms the limitations of standard semen analysis. Four main protein groups were identified in correlation with abnormal DNA fragmentation and/or motility. The first group included sperm nuclear proteins such as the SPANX (sperm protein associated with the nucleus on the X chromosome) isoforms and several types of histones. The second group contained mitochondria-related functions and oxidative stress proteins including Mitochondrial Ferritin, Mitochondrial Single-Stranded DNA Binding Protein, and several isoforms of Peroxiredoxins. Two other protein groups were related to sperm motility such as microtubule-based flagellum and spindle microtubule as well as proteins related to the ubiquitin-proteasome pathway. Further research is required in order to characterize these potential biomarkers of male fertility potential.

Toona sinensis Leaf Aqueous Extract Improves the Functions of Sperm and Testes via Regulating Testicular Proteins in Rats under Oxidative Stress

Toona sinensis leaf (TSL) is commonly used as a vegetable and in spice in Asia. In this study, feeding with aqueous extract of TSL (TSL-A) alleviated oxidative stress and recovered the motility and functions of sperm in rats under oxidative stress. Protein expressions in testes identified by proteomic analysis and verified by Western blot demonstrated that TSL-A not only downregulated the level of glutathione transferase mu6 (antioxidant system), heat shock protein 90 kDa-β (protein misfolding repairing system), cofilin 2 (spermatogenesis), and cyclophilin A (apoptosis) but also upregulated crease3-hydroxy-3-methylglutaryl-coenzyme A synthase 2 (steroidogenesis), heat shock glycoprotein 96, and pancreatic trypsin 1 (sperm-oocyte interaction). These results indicate that TSL-A promotes the functions of sperm and testes via regulating multiple testicular proteins in rats under oxidative stress, suggesting that TSL-A is a valuable functional food supplement to improve functions of sperm and testes for males under oxidative stress.

Proliferation and apoptosis in aged and photoregressed mammalian seminiferous epithelium, with particular attention to rodents and humans

Imbalances in the proliferation and apoptosis processes are involved in numerous epithelial alterations. In the seminiferous epithelium, normal spermatogenesis is regulated by spermatogonia proliferation and germ cell apoptosis, and both processes are involved in diverse pathological alterations of the seminiferous epithelium. Other physiological phenomena including aging and short photoperiod, in which apoptosis and proliferation seem to play important roles, cause testicular changes. Aging is accompanied by diminished proliferation and increased apoptosis, the latter occurring in specific states of the seminiferous cycle and considered the cause of epithelium involution. However, there is no clear evidence concerning whether proliferation decreases in the spermatogonia themselves or is due to an alteration in the cell microenvironment that surrounds them. As regards the factors that regulate the process, the data are scant, but it is considered that the diminution of c-kit expression in the spermatagonia, together with the diminution in antiapoptotic factors (Bcl-x(L))) of the intrinsic molecular pathway of apoptosis play a part in epithelial regression. A short photoperiod, especially in rodents, produces a gradual involution of the seminiferous epithelium, which is related with increased apoptosis during the regression phase and a diminution of apoptosis during recrudescence. Proliferative activity varies, especially during the total regression phase, when it usually increases in the undifferentiated spermatogonia. In other species showing seasonal reproduction, however, decreased proliferation is considered the main factor in the regression of the seminiferous epithelium. Little is known about how both phenomena are regulated, although data in rodents suggest that both the intrinsic and extrinsic pathways of apoptosis contribute to the increase in this process. In conclusion, regression of the seminiferous epithelium in physiological situations, as in many pathological situations, is a result of alterations in equilibrium between the proliferation and apoptosis of germinal cell types. However, both physiological phenomena showed important differences as regard proliferation/apoptosis and their regulation pathways, probably as a result of their irreversible or reversible character.

Millions of years of evolution preserved: a comprehensive catalog of the processed pseudogenes in the human genome

Processed pseudogenes were created by reverse-transcription of mRNAs; they provide snapshots of ancient genes existing millions of years ago in the genome. To find them in the present-day human, we developed a pipeline using features such as intron-absence, frame-disruption, polyadenylation, and truncation. This has enabled us to identify in recent genome drafts approximately 8000 processed pseudogenes (distributed from http://pseudogene.org). Overall, processed pseudogenes are very similar to their closest corresponding human gene, being 94% complete in coding regions, with sequence similarity of 75% for amino acids and 86% for nucleotides. Their chromosomal distribution appears random and dispersed, with the numbers on chromosomes proportional to length, suggesting sustained "bombardment" over evolution. However, it does vary with GC-content: Processed pseudogenes occur mostly in intermediate GC-content regions. This is similar to Alus but contrasts with functional genes and L1-repeats. Pseudogenes, moreover, have age profiles similar to Alus. The number of pseudogenes associated with a given gene follows a power-law relationship, with a few genes giving rise to many pseudogenes and most giving rise to few. The prevalence of processed pseudogenes agrees well with germ-line gene expression. Highly expressed ribosomal proteins account for approximately 20% of the total. Other notables include cyclophilin-A, keratin, GAPDH, and cytochrome c.

Expression, action, and regulation of transforming growth factor alpha and epidermal growth factor receptor during embryonic and perinatal rat testis development

The objective of the current study was to extend previous observations and examine the expression pattern and effects of transforming growth factor alpha (TGFalpha) and epidermal growth factor receptor (EGFR) on embryonic testis morphogenesis and growth. The expression of TGFalpha was determined after morphological sex determination (seminiferous cord formation at embryonic day 13 [ED13]) through perinatal testis development (postnatal day 5 [PD5]) with a quantitative reverse transcription-polymerase chain reaction procedure. Expression of messenger RNA (mRNA) for TGFalpha appeared to be more dynamic during testis development when compared with the expression of mRNA for EGFR. Message for TGFalpha was reduced at ED16 and PD4, and was elevated at PD0 during testis development. In contrast, EGFR mRNA levels were negligible at ED15 and were elevated constitutively from ED16 through PD5. Immunohistochemistry was conducted at ED14, ED16, ED19, PD0, PD3, and PD5 to localize cellular expression of both TGFalpha and EGFR. At ED16, positive staining for EGFR was localized to the cords, and by ED19, was mainly in the cords with slight expression in the interstitium. From PD0 to PD5, positive staining for EGFR was detected in the germ, Sertoli, and interstitial cells. Immunohistochemistry for TGFalpha detected localization at ED14 and ED16 to the Sertoli cells and to specific cells in the interstitium. From ED19 through PD5, TGFalpha was detected in the Sertoli, germ, and interstitial cells, and in endothelial cells within the interstitium. To determine the effects of TGFalpha on embryonic testis growth and seminiferous cord formation, ED13 testis organ cultures were treated with sense and antisense TGFalpha oligonucleotides. Antisense TGFalpha inhibited testis growth by 25%-30% in ED13 testis organ cultures when compared with sense oligonucleotide control pairs. To examine the effects of TGFalpha on perinatal testis growth, PD0 testis cultures were treated with different doses of TGFalpha. TGFalpha increased thymidine incorporation into DNA in PD0 testis cultures. Therefore, TGFalpha appears to have actions on both embryonic and perinatal testis growth. The regulation of TGFalpha and EGFR mRNA levels were examined using PD0 testis cultures treated with hormones that stimulate testis growth. Follicle-stimulating hormone (FSH) stimulated (P < .05) and testosterone tended to stimulate (P < .07) mRNA expression of EGFR. Epidermal growth factor stimulation of PD0 testis cultures did not affect levels of mRNA expression for EGFR, but did suppress expression of mRNA for TGFalpha. These results taken together demonstrate that TGFalpha can act to regulate early embryonic and perinatal testis growth. Furthermore, TGFalpha and EGFR expression can be regulated through growth stimulatory hormones such as FSH and testosterone.

Brain ischemia and reperfusion: molecular mechanisms of neuronal injury

Brain ischemia and reperfusion engage multiple independently-fatal terminal pathways involving loss of membrane integrity in partitioning ions, progressive proteolysis, and inability to check these processes because of loss of general translation competence and reduced survival signal-transduction. Ischemia results in rapid loss of high-energy phosphate compounds and generalized depolarization, which induces release of glutamate and, in selectively vulnerable neurons (SVNs), opening of both voltage-dependent and glutamate-regulated calcium channels. This allows a large increase in cytosolic Ca(2+) associated with activation of mu-calpain, calcineurin, and phospholipases with consequent proteolysis of calpain substrates (including spectrin and eIF4G), activation of NOS and potentially of Bad, and accumulation of free arachidonic acid, which can induce depletion of Ca(2+) from the ER lumen. A kinase that shuts off translation initiation by phosphorylating the alpha-subunit of eukaryotic initiation factor-2 (eIF2alpha) is activated either by adenosine degradation products or depletion of ER lumenal Ca(2+). Early during reperfusion, oxidative metabolism of arachidonate causes a burst of excess oxygen radicals, iron is released from storage proteins by superoxide-mediated reduction, and NO is generated. These events result in peroxynitrite generation, inappropriate protein nitrosylation, and lipid peroxidation, which ultrastructurally appears to principally damage the plasmalemma of SVNs. The initial recovery of ATP supports very rapid eIF2alpha phosphorylation that in SVNs is prolonged and associated with a major reduction in protein synthesis. High catecholamine levels induced by the ischemic episode itself and/or drug administration down-regulate insulin secretion and induce inhibition of growth-factor receptor tyrosine kinase activity, effects associated with down-regulation of survival signal-transduction through the Ras pathway. Caspase activation occurs during the early hours of reperfusion following mitochondrial release of caspase 9 and cytochrome c. The SVNs find themselves with substantial membrane damage, calpain-mediated proteolytic degradation of eIF4G and cytoskeletal proteins, altered translation initiation mechanisms that substantially reduce total protein synthesis and impose major alterations in message selection, down-regulated survival signal-transduction, and caspase activation. This picture argues powerfully that, for therapy of brain ischemia and reperfusion, the concept of single drug intervention (which has characterized the approaches of basic research, the pharmaceutical industry, and clinical trials) cannot be effective. Although rigorous study of multi-drug protocols is very demanding, effective therapy is likely to require (1) peptide growth factors for early activation of survival-signaling pathways and recovery of translation competence, (2) inhibition of lipid peroxidation, (3) inhibition of calpain, and (4) caspase inhibition. Examination of such protocols will require not only characterization of functional and histopathologic outcome, but also study of biochemical markers of the injury processes to establish the role of each drug.

Expression and action of transforming growth factor beta (TGFbeta1, TGFbeta2, and TGFbeta3) during embryonic rat testis development

The objective of the current study was to determine the role of transforming growth factor beta (TGFbeta) during seminiferous cord formation and embryonic testis development. The expression pattern of mRNA for TGFbeta isoforms was evaluated during testis development through a quantitative reverse transcription-polymerase chain reaction (QRT-PCR) procedure. Expression of mRNA for TGFbeta1 was highest at postnatal day 0 (P0) and P10. In contrast, TGFbeta2 was high at embryonic day 15 (E15), declined at E16, and showed a transient increase at P0 through P3 of testis development. Interestingly, expression of mRNA for TGFbeta3 was high during embryonic development and then declined after P3. Immunohistochemical localization of TGFbeta1 and TGFbeta2 demonstrated expression in Sertoli cells at E14 and in the seminiferous cords at P0. Selective interstitial cells expressed high concentrations of TGFbeta1 and TGFbeta2 in P0 testis. TGFbeta3 was expressed in selective cells at the junction of the E14 testis and mesonephros. The cells expressing TGFbeta3 in the testis appeared to be preperitubular cells that resided around the seminiferous cords. TGFbeta3 was localized to gonocytes in P0 testis. TGFbeta1 was found to have no influence on seminiferous cord formation in embryonic organ cultures of E13 testis. In contrast, growth of both E13 and E14 embryonic organ cultures was inhibited by TGFbeta1 and resulted in reduced testis size (40% of controls) with fewer cords present. A P0 testis cell culture and thymidine incorporation assay were used to directly examine the effects of recombinant TGFbeta1. TGFbeta1 alone had no influence on thymidine incorporation in P0 testis cell cultures when compared to controls. Interestingly, TGFbeta1 inhibited epidermal growth factor (EGF), and 10% calf serum stimulated P0 testis cell growth but not FSH-stimulated growth. Therefore, TGFbeta1 appears to inhibit testis growth in both the embryonic and early postnatal periods. The hormonal regulation of TGFbeta expression was measured using P0 testis cell cultures and a QRT-PCR procedure for each TGFbeta isoform. High concentrations of EGF stimulated expression of mRNA for TGFbeta1 after 24 h but suppressed expression of TGFbeta3. In contrast, there was no effect of FSH on TGFbeta isoform expression. In summary, TGFbeta regulates embryonic and P0 testis growth through inhibiting the actions of positive growth factors such as EGF. In addition, EGF but not FSH appears to regulate TGFbeta isoform expression. Combined observations from the present study demonstrate that TGFbeta isoforms are differentially expressed and appear to be regulators of testis growth during the embryonic and early postnatal periods.

DEFT, a novel death effector domain-containing molecule predominantly expressed in testicular germ cells

Apoptosis is a physiological process by which multicellular organisms eliminate unwanted cells. Death factors such as Fas ligand induce apoptosis by triggering a series of intracellular protein-protein interactions mediated by defined motifs found in the signaling molecules. One of these motifs is the death effector domain (DED), a stretch of about 80 amino acids that is shared by adaptors, regulators, and executors of the death factor pathway. We have identified the human and rat complementary DNAs encoding a novel protein termed DEFT (Death EFfector domain-containing Testicular molecule). The N-terminus of DEFT shows a high degree of homology to the DEDs found in FADD (an adaptor molecule) as well as procaspase-8/FLICE and procaspase-10/Mch4 (executors of the death program). Northern blot hybridization experiments have shown that the DEFT messenger RNA (mRNA) is expressed in a variety of human and rat tissues, with particularly abundant expression in the testis. In situ hybridization analysis further indicated the expression of DEFT mRNA in meiotic male germ cells. In a model of germ cell apoptosis induction, an increase in testis DEFT mRNA was found in immature rats after 2 days of treatment with a GnRH antagonist. Unlike FADD and procaspase-8/FLICE, overexpression of DEFT did not induce apoptosis in Chinese hamster ovary cells. Although cotransfection studies indicated that DEFT is incapable of modulating apoptosis effected by FADD and procaspase-8/FLICE, interactions between DEFT and uncharacterized DED-containing molecules in the testis remain to be studied in the future. In conclusion, we have identified a novel DED-containing protein with high expression in testis germ cells. This protein may be important in the regulation of death factor-induced apoptosis in the testis and other tissues.

Biphasic c-Myc protein expression during gossypol-induced apoptosis in rat spermatocytes

The presence of protooncogene products such as c-Myc proteins in rat spermatocytes has been quantitatively detected by Western immunoblot and a computer-controlled Spotdenso-program with an IS-1000 digital imaging system. Cellular levels of c-Myc proteins in response to gossypol were measured in spermatocytes during the process of gossypol-induced apoptosis. Within 0.5 to 2 h of the addition of gossypol, levels of c-Myc proteins fall dramatically and remain at a low level for the next several hours. The reduction in c-Myc proteins occurs 4.5-6 h before the apoptosis of spermatocytes in the presence of gossypol. Between 3 and 5 h after exposure to gossypol, the c-Myc protein content returns to preexposure (or higher) levels. In addition, the increase in c-Myc proteins occurs 1.5-4 h before the apoptotic death of spermatocytes. An identical pattern of c-Myc protein response to gossypol was also found in total testicular tissue in vitro. These results suggest that spermatocyte apoptosis induced by gossypol is correlated with biphasic c-Myc protein expression. This article present some hypothetical models with which to explain c-Myc protein-mediated apoptosis.