Koji Y. Arai

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.

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.

Novel factors in regulation of activin signaling.

Activin type II receptors (ActRIIs) are the primary receptors that transmit the activin signal to intracellular signaling pathways. Binding of activins to ActRIIs recruits the activin type I receptor and initiates downstream signaling. We have found that PDZ proteins, named activin receptor-interacting proteins (ARIPs), specifically associate with ActRIIs. We have studied the mechanism that ARIPs regulate cell surface expression and cellular localization of ActRIIs. ARIP2 interacts with both ActRIIs and RalBP1 (Ral binding protein 1) through different domains to dramatically change the localization of ActRIIs. Overexpression of ARIP2 enhances endocytosis of ActRIIs. These data indicate that ARIP2 is a novel factor regulating cell surface ActRII expression and activin function. A novel activin binding protein, follistatin-related gene (FLRG) was identified. FLRG protein binds activin and myostatin with a high affinity. The biological activity of FLRG is similar to those of follistatin, however, the regulation and expression patterns of follistatin and FLRG differ. Immunohistochemical analysis shows that FLRG is distributed in spermatogenic cells of the testis, renal tubules, epithelial cells of the lung, and myocardium. Thus, although structurally and functionally similar, follistatin and FLRG likely play distinct roles as activin/GDF binding proteins in vivo.

A New Alternative Method for Superovulation Using Passive Immunization Against Inhibin in Adult Rats

Abstract The present study was undertaken to investigate the effects of passive immunoneutralization of endogenous inhibin on ovulation rate and embryo development in vivo and in vitro to establish a new alternative superovulation method in the adult rat. Female adult rats of Wistar strain were superovulated with a single injection of inhibin antiserum (inhibin-AS; 100 or 400 μl) or an injection of 20 IU eCG followed by an injection of 10 IU hCG. Untreated animals served as controls. Embryos were collected from oviducts or uteri on Days 1–5 of pregnancy, and the number of embryos and implantation sites were observed. On Day 1 of pregnancy, the two-cell-stage embryos were cultured and embryos from the 100-μl inhibin-AS group and the control group were transferred to recipient females to determine developmental competence. There were no significant differences between groups in fertilization rate. The numbers of normal embryos in the inhibin-AS-treated groups were significantly higher than the control and the eCG-hCG-treated groups throughout Days 1–4 of pregnancy. The number of implantation sites observed on Day 5 of pregnancy in the inhibin-AS-treated groups was significantly higher than both the control and the eCG-hCG-treated groups. Furthermore, the rate of blastocyst development in vitro in the inhibin-AS-treated groups and posttransfer viability in the 100-μl-inhibin-AS group were comparable with those of the control group. These results indicate that immunoneutralization of endogenous inhibin is a new practical alternative for induction of superovulation as a substitution for eCG-hCG method in the adult rat.

Dynamics of Messenger RNAs Encoding Inhibin/Activin Subunits and Follistatin in the Ovary During the Rat Estrous Cycle

Abstract Quantitative changes in ovarian inhibin/activin subunit and follistatin mRNAs during the rat estrous cycle were examined by ribonuclease protection assay using digoxygenin-labeled RNA probes. Levels of ovarian inhibin α subunit mRNA remained low throughout estrus, metestrus, and diestrus; abruptly increased on the morning of proestrus; then rapidly decreased when the primary gonadotropin surge occurred. A similar changing pattern was observed in inhibin/activin βA subunit mRNA. On the other hand, inhibin/activin βB subunit mRNA showed a different changing pattern. Levels of βB subunit mRNA remained constant during metestrus and diestrus, abruptly decreased on the afternoon of proestrus, then quickly recovered from the nadir by 1100 h on estrus. Throughout the rat estrous cycle, especially during the periovulatory period, α subunit mRNA levels were considerably higher than βA and βB subunit mRNA levels. In addition, changes in plasma concentrations of inhibin A and inhibin B were very similar to that in ovarian βA and βB subunit mRNA levels, respectively, with several-hour delays. These results suggest that levels of β subunit mRNAs restrict secretion of dimeric inhibins. Levels of follistatin mRNA remained low from the midnight of metestrus to the midnight of diestrus, then increased until initiation of the primary gonadotropin surge. Thereafter, follistatin mRNA decreased, reached the nadir at 0200 h on estrus, then increased abruptly at 1100 h on estrus. Afterward, follistatin mRNA levels remained high until the morning of metestrus. The changing pattern of ovarian follistatin mRNA was similar to, and preceded, the changes in plasma concentrations of progesterone, suggesting that ovarian follistatin may modulate progesterone secretion during the rat estrous cycle.

Effects of vitamin C deficiency on the skin of the senescence marker protein-30 (SMP30) knockout mouse

Senescence marker protein-30 (SMP30) is a gluconolactonase required for vitamin C (VC) synthesis. We examined effects of VC deficiency on the mouse skin using SMP30 knockout (KO) mice. SMP30 KO or wild type male mice were weaned around day 30 of age, and fed VC-deficient diet. They were given either VC water or control water. VC deficiency for 36 days did not affect skin hydroxyproline contents, while VC deficiency for 60 days decreased the hydroxyproline levels. Levels of some collagen mRNAs were different among the groups, but did not correlate with skin VC levels. The epidermis was morphologically abnormal in VC-deficient SMP30 KO mouse at 60 days after the weaning. Interestingly, the hair cycle was not synchronized among the groups. These data suggest low susceptibility of the mouse skin to VC deficiency and involvement of VC in the regulation of keratinocyte function and hair cycle in vivo.

Characterization of Rat Follistatin-Related Gene: Effects of Estrous Cycle Stage and Pregnancy on Its Messenger RNA Expression in Rat Reproductive Tissues

Abstract Follistatin-related gene (FLRG) was first identified as a target of a chromosomal translocation in a human B-cell leukemia. Because FLRG protein binds to activins and bone morphogenetic proteins, FLRG is postulated to be a regulator of these growth factors. However, physiological aspects of FLRG are unclear. To elucidate the physiology of FLRG, we examined expression of FLRG in reproductive tissues of the rat. FLRG mRNA was abundantly expressed in the placenta. FLRG mRNA was also expressed in the ovary, uterus, testis, lung, adrenal gland, pituitary, kidney, small intestine, and heart. During the second half of pregnancy, expression of FLRG in the placenta continuously increased, whereas follistatin mRNA levels decreased from Day 12 to Day 14 and remained low thereafter. FLRG was also expressed in decidua. Levels of decidual FLRG mRNA remained low from Day 12 to Day 16 and then noticeably increased until Day 20. In contrast, follistatin mRNA was highly expressed in the decidua on Day 12, continuously decreased until Day 16, and then remained at relatively low levels thereafter. During the rat estrous cycle, levels of ovarian FLRG mRNA fluctuated diurnally, with highest levels during daytime, and did not change relative to the day of the estrous cycle. The present results suggest that FLRG may play a role in the regulation of reproductive events.

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.

Developmental Changes in Extracellular Matrix Messenger RNAs in the Mouse Placenta During the Second Half of Pregnancy: Possible Factors Involved in the Regulation of Placental Extracellular Matrix Expression

Abstract Expression of procollagens (Col1a1/2, Col3a1, Col4a1/2, Col5a1/2) and fibronectin 1 (Fn1) in the mouse fetal placental tissue was examined during the second half of pregnancy. Ribonuclease protection assays (RPAs) revealed that levels of these mRNAs noticeably increased between Days 10 and 14 of pregnancy, and they remained at relatively constant levels thereafter. In situ hyridization showed that Col1a1 and Col4a1 mainly localized in the labyrinth, whereas Fn1 was expressed mainly in the spongiotrophoblast. Since members of the transforming growth factor-beta (TGFB) superfamily are involved in the regulation of extracellular matrix (ECM) expression in various tissues, mRNA levels of TGFB family members and their binding proteins were also examined by RPAs. Transforming growth factor-beta1–3 (Tgfb1–3), activin subunits (Inhba, Inhbb), follistatin (Fst), and follistatin-like 3 (Fstl3) were expressed in the placenta, whereas significant expression of myostatin (Mstn) was not detected. Although the expression patterns of Tgfb1–3 and Inhba in the placenta suggest possible involvement of TGFBs and activin A in the regulation of placental ECM expression, neither TGFBs nor activin A affected ECM mRNA levels in vitro. On the other hand, hypoxia significantly decreased Col1a1/2 and Col4a1/2 mRNAs in cultured placental cells, and a high-glucose condition significantly increased Col1a1 and Col3a1 mRNAs. Fn1 expression was increased under the high-glucose condition, although hypoxia also increased Fn1 expression to a lesser degree. These data suggest that an increase in oxygen tension and nutrient supply during placentation rather than TGFB family members may be responsible for the increase in the placental ECM mRNA expression.

Changes in Expression of Inhibin Subunits in the Cyclic Golden Hamster (Mesocricetus auratus) and the Regulation of Inhibin α Subunit Production by Luteinizing Hormone

In the present study, changes in localization of each inhibin subunit in the ovary were investigated during the estrous cycle of the golden hamster. The effect of LH surge on changes in localization in inhibin α subunit in the ovary was also investigated. Inhibin α subunit was localized in granulosa cells of various stages of follicles throughout the estrous cycle. Inhibin α subunit was also present in numerous interstitial cells on days 1 and 2 (day 1 = day of ovulation), but the number of positive interstitial cells was fewer on days 3 and almost disappeared on day 4 of the estrous cycle. Newly formed luteal cells were also positive for inhibin α subunit on days 1 and 2. On the other hand, positive reactions for inhibin βA and βB subunits were only present in the granulosa cells of healthy antral follicles. However, a positive reaction for inhibin βB subunit in peripheral mural granulosa cells disappeared on days 3 and 4 of the estrous cycle. Treatment with LHRH-AS at 1100 h on day 4 completely blocked the luteinizing hormone (LH) surge and ovulation, although relatively high concentrations of plasma follicle-stimulating hormone (FSH) were maintained throughout the experiment. There were few positive reactions for inhibin α subunit in theca and interstitial cells 24 hr after LHRH-AS injection. The effect of LHRH-AS treatment was blocked by a single injection of 10 IU human chorionic gonadotropin. These results suggest that the major source of dimeric inhibin in the cyclic hamster was granulosa cells of healthy antral follicles. Different distribution pattern of inhibin βA from βB subunits in large antral follicles on days 3 and 4 of the estrous cycle suggests different secretion patterns of inhibin A from B on these days. Furthermore, the LH surge may be an important factor to induce production of inhibin α subunit in interstitial cells of the cyclic hamster.