Wanzhu Jin

Adverse effects of environmental toxicants, octylphenol and bisphenol A, on male reproductive functions in pubertal rats

It has been proposed that a global decline in sperm counts, semen quality, and several male reproductive disorders are associated with exposure to environmental chemicals. Thus, the present study examined the effects of two estrogenic chemicals, octylphenol (OP) and bisphenol A (BPA), on epididymal sperm counts and sperm motility, luteinizing hormone (LH)-releasing hormone (LHRH)-stimulated plasma LH and steroid hormones, insulin-like growth factor I (IGF-I), and accessory reproductive organs in pubertal male Wistar rats. Fifty-day-old rats in the OP group (n=11) and BPA group (n=11) received daily sc injections of the respective chemical at a dose of 3 mg/kg bw dissolved in 0.2 mL DMSO. Rats in the control group (DMSO group; n=10) received 0.2 mL DMSO alone. After 2 wk of treatment, a jugular blood sample was taken, and, on the next day, a second blood sample was taken 1 h after an sc injection of LHRH (250 ng). After 5 wk of treatment, rats were deeply anesthetized and heart blood was collected. Epididymal sperm motility and sperm head counts were determined. LHRH increased plasma LH to higher levels in all groups, but the increases were significant (p<0.01) in the BPA and OP groups. However, despite higher LH levels after LHRH injection, the incremental responses of testosterone and progesterone in the OP and BPA groups were small compared to those in the DMSO group, which showed a small LH response. After 5 wk of treatment, plasma testosterone levels were significantly (p<0.01) reduced in the OP and BPA groups and this was accompanied by reduced (p<0.05) epididymal sperm counts. However, the chemical-treated groups had high basal progesterone levels. No significant effects of chemicals on sperm motility parameters were noted. The chemical-induced increases (p<0.05) of the weight of ventral prostate gland were coincided with elevated plasma IGF-I levels in the BPA (p<0.05) and OP (p<0.01) groups. The present results demonstrated that OP and BPA can reduce sperm counts resulting from lowered plasma testosterone in male rats just after puberty. The enlarged ventral prostate gland may possibly be associated with increased plasma IGF-I, raising the possibility of a link between these chemicals and prostate diseases because IGF-I has been implicated in the pathogenesis of human prostate cancers.

The Role of ATF-2 Family Transcription Factors in Adipocyte Differentiation: Antiobesity Effects of p38 Inhibitors

ABSTRACT ATF-2 is a member of the ATF/CREB family of transcription factors and is activated by stress-activated protein kinases, such as p38. To analyze the physiological role of ATF-2 family transcription factors, we have generated mice with mutations in Atf-2 and Cre-bpa, an Atf-2-related gene. The trans-heterozygotes of both mutants were lean and had reduced white adipose tissue (WAT). ATF-2 and CRE-BPa were required for bone morphogenetic protein 2 (BMP-2)-and p38-dependent induction of peroxisome proliferator-activated receptor γ2 (PPARγ2), a key transcription factor mediating adipocyte differentiation. Since stored fat supplies have been recognized as a possible target for antiobesity treatments, we tested whether inhibition of the p38-ATF-2 pathway suppresses adipocyte differentiation and leads to reduced WAT by treating mice with a p38 inhibitor for long periods of time. High-fat diet (HFD)-induced obesity was significantly reduced in mice fed the p38 inhibitor. Furthermore, the p38 inhibitor alleviated HFD-induced insulin resistance. In p38 inhibitor-treated mice, macrophage infiltration into WAT was reduced and the tumor necrosis factor alpha (TNF-α) levels were lower than control mice. Thus, p38 inhibitors may provide a novel antiobesity treatment.

Expression of Nerve Growth Factor and Its Receptors NTRK1 and TNFRSF1B Is Regulated by Estrogen and Progesterone in the Uteri of Golden Hamsters

Abstract Experiments were conducted using female golden hamsters to identify the presence of nerve growth factor (NGF) and its receptors NTRK1 and TNFRSF1B in the uteri of female animals and regulation on their expression by estrogen and progesterone. NGF and its receptor NTRK1 were immunolocalized to luminal epithelial cells, glandular cells, and stromal cells. TNFRSF1B was immunolocalized in luminal epithelial and glandular cells, with no staining found in stromal cells of the uterine horns of normal cyclic golden hamsters. Strong immunostaining of NGF and its receptors NTRK1 and TNFRSF1B was observed in uteri on the day of proestrus as compared to the other stages of the estrous cycle. Results of immunoblot analysis of NGF revealed that there was a positive correlation between uterine NGF expression and plasma concentrations of estradiol-17β. To clarify the effects of estrogen and progesterone on NGF, NTRK1, and TNFRSF1B expression, adult female golden hamsters were ovariectomized and treated with estradiol-17β and/or progesterone. Immunoblot analysis and immunohistochemistry indicated that estradiol-17β stimulated expression of NGF and its two receptors in the uterus. Treatment with progesterone also increased NGF and NTRK1 expression in the uterus. However, no additive effect of these steroids on expression of NGF and its receptors was observed. Changes in uterine weights induced by estradiol-17β and/or progesterone showed the same profile with that of NGF, suggesting that a proliferative act of NGF may be involved in uterine growth. These results suggest that NGF may play important roles in action of steroids on uterine function.

Ubiquitination-deubiquitination by the TRIM27-USP7 complex regulates tumor necrosis factor alpha-induced apoptosis.

ABSTRACT Tumor necrosis factor alpha (TNF-α) plays a role in apoptosis and proliferation in multiple types of cells, and defects in TNF-α-induced apoptosis are associated with various autoimmune diseases. Here, we show that TRIM27, a tripartite motif (TRIM) protein containing RING finger, B-box, and coiled-coil domains, positively regulates TNF-α-induced apoptosis. Trim27-deficient mice are resistant to TNF-α–d-galactosamine-induced hepatocyte apoptosis. Trim27-deficient mouse embryonic fibroblasts (MEFs) are also resistant to TNF-α–cycloheximide-induced apoptosis. TRIM27 forms a complex with and ubiquitinates the ubiquitin-specific protease USP7, which deubiquitinates receptor-interacting protein 1 (RIP1), resulting in the positive regulation of TNF-α-induced apoptosis. Our findings indicate that the ubiquitination-deubiquitination cascade mediated by the TRIM27-USP7 complex plays an important role in TNF-α-induced apoptosis.

Regulation of Follicle-Stimulating Hormone Secretion by Estradiol and Dimeric Inhibins in the Infantile Female Rat

Abstract Plasma and ovarian levels of the dimeric forms of inhibin and plasma estradiol-17β were investigated and compared with changes in plasma gonadotropins from Postnatal Day (PND) 5 to PND 30 in the female rat. The inhibin subunit proteins were localized in follicular granulosa cells of the ovary. Plasma immunoreactive inhibin levels were low until PND 15 and increased thereafter. Plasma levels of inhibin B (α and βB subunits) remained very low until PND 15 and then increased by approximately 24-fold. In contrast, plasma levels of inhibin A (α and βA subunits) were relatively low and steady until PND 20, then increased by approximately 3-fold at PND 25. Changes in ovarian inhibin A and B levels closely resembled those in plasma levels. Plasma FSH levels were low at PND 10 but started to peak from PND 15 and remained high until PND 20, followed by a remarkable reduction at PNDs 25 and 30. This dramatic fall in FSH coincided with the rise of inhibin A. A significant inverse correlation was observed between plasma FSH and plasma inhibin A (r = −0.67, P < 0.0002), ovarian inhibin A (r = −0.48, P < 0.01), plasma inhibin B (r = −0.48, P < 0.05), and ovarian inhibin B (r = −0.54, P < 0.01). Plasma estradiol-17β levels were elevated from PND 5 through PND 15 , then fell sharply through PND 30. Plasma estradiol-17β was significantly and positively (r = 0.75, P < 0.0002) correlated with plasma FSH. Plasma LH rose to higher levels at PND 15 and tended to be lower thereafter. The inhibin α, βA, and βB subunits were localized to primary, secondary, and antral and large antral follicles, but the types of these immunopositive follicles varied with age. It appeared that, at PND 25 and afterward, all three subunits were mainly confined to large antral follicles in the ovary. We conclude that estradiol-17β likely is the major candidate in stimulation of FSH secretion in the infantile female rat. We also conclude that inhibin regulation of pituitary FSH secretion through its negative feedback in the infantile female rat begins to operate after PND 20. We suggest that this negative feedback is achieved by increases in plasma levels of the two dimeric forms, and that inhibin A appears to be the major physiological regulator of FSH secretion at the initiation of this mechanism. We also conclude that large antral follicles in the ovary are the primary source of these bioactive inhibins that are secreted in large amounts into the circulation after PND 20.

Expression of Nerve Growth Factor (NGF), and Its Receptors TrkA and p75 in the Reproductive Organs of the Adult Male Rats

Abstract Immunolocalization of nerve growth factor (NGF) and its receptors, TrkA and p75 in the reproductive organs of adult male rats was investigated. Sections of the testis, efferent duct, epididymis, deferent duct, seminal vesicle, coagulating gland and prostate of adult male rats were immunostained by the avidin-biotin-peroxidase complex methods (ABC). NGF was expressed in Leydig cells, primary spermatocytes and pachytene spermatocytes in the testis. TrkA only immunoreacted to elongate spermatids and p75 showed positive immunostaining in the Sertoli cells, Leydig cells, the pachytene spermatocytes and elongate spermatids. Immunoreactions for NGF and its two receptors were detected in epithelial cells of efferent duct, deferent duct and epididymis. In addition, immunoreactions for NGF and its two receptors were also observed in columnar secretory epithelium lines of the seminal vesicles, prostate and coagulating gland. These results suggest that NGF is an important growth factor in gonadal function of adult male rats.

Schnurri-2 mutant mice are hypersensitive to stress and hyperactive

The bone morphogenetic protein (BMP)/transforming growth factor-beta (TGF-beta)/activin superfamily regulates development of the nervous system during embryogenesis and is also suggested to be involved in adult brain function. However, how BMP/TGF-beta/activin signals modulate neuronal function remains unknown. Schnurri is a transcription factor that contains two metal finger regions. Mammalian Shn-2 enters the nucleus from the cytoplasm in response to BMP-2 stimulation and plays an important role in BMP-dependent adipogenesis. To investigate whether mammalian Shn plays a role in adult brain function, we examined the behaviors of mutant mice lacking Shn-2 (Shn-2(-/-)). Shn-2(-/-) mice exhibited hypersensitivity to stress accompanied by anxiety-like behavior. Consistent with this, stress-induced corticosterone levels were significantly higher in Shn-2(-/-) mice compared to wild-type controls. Interestingly, Shn-2(-/-) mice were more active than wild-type mice in a familiar environment. The basal and stress-induced expression levels of the immediate early genes, including c-Fos, were decreased in Shn-2(-/-) mice compared to wild-type mice. Thus, Shn-2 plays a critical role in locomotion and anxiety-like behavior.

Cellular localization of NGF and its receptors trkA and p75LNGFR in male reproductive organs of the Japanese monkey, Macaca fuscata fuscata

The actions of neurotropins are not restricted to the nervous system. Immunohistochemical methods were used in the present study to clarify distribution of nerve growth factor (NGF) and its receptors TrkA and p75LNGFR in excurrent ducts of the adult male Japanese monkey (Macaca fuscata fuscata). NGF was found in the seminal vesicle, epididymis, and testis, and has been thought to affect male reproductive functions. Leydig cells, Sertoli cells, and spermatogonia at various stages were positively stained for NGF, as well as for TrkA and p75LNGFR. Signals for these proteins were also found in epithelial cells and stromal tissues of the caudal epididymidis, as well as in the seminal vesicle. In the prostate, smooth muscle cells and basal cells were positively stained for NGF, TrkA, and p75LNGFR. The results were comparatively discussed.

p53 Suppresses c-Myb-induced trans-Activation and Transformation by Recruiting the Corepressor mSin3A

p53 is known to repress transcription of a number of genes, but the mechanism of p53 recruitment to these target genes is unknown. The c-myb proto-oncogene product (c-Myb) positively regulates proliferation of immature hematopoietic cells, whereas p53 blocks cell cycle progression. Here, we demonstrate that p53 inhibits c-Myb-induced transcription and transformation by directly binding to c-Myb. The ability of c-Myb to maintain the undifferentiated state of M1 cells was also suppressed by p53. p53 did not affect the ability of c-Myb to bind to DNA but formed a ternary complex with the corepressor mSin3A and c-Myb. Thus, p53 antagonizes c-Myb by recruiting mSin3A to down-regulate specific Myb target genes.

Inhibin B is the major form of inhibin secreted from testes in male Japanese macaques (Macaca fuscata)

In order to clarify the cellular source and forms of bioactive inhibin in male Japanese macaques (Macaca fuscata), circulating concentrations of inhibin A and B, and immunohistochemical localization of inhibin subunits in testis were studied. Plasma concentrations of testosterone were also measured. The present study showed that inhibin B was clearly detected in the plasma of male Japanese macaques. Moreover, concentrations of both inhibin B and testosterone during the breeding (mating) season were significantly higher than those of the non-breeding season. On the other hand, plasma inhibin A was detected neither during the breeding seasons nor during the non-breeding seasons. Positive stainings with α and βB subunit antibodies were observed in the Sertoli cells, however staining with βA subunit antibody was not observed in the testicular samples. These results indicate that inhibin B is the major circulating inhibin and probably secreting from Sertoli cells in male Japanese macaques.