Growth arrest and induction of apoptosis in breast cancer cells by antisense depletion of protein kinase A-RI alpha subunit: p53-independent mechanism of action

The enhanced expression of the RI alpha subunit of cyclic AMP-dependent protein kinase type 1 (PKA-1) has been correlated with cancer cell growth. We have investigated the effects of sequence-specific inhibition of RI alpha gene expression on the growth of MCF-7 human breast cancer cells. We report that RI alpha antisense treatment results in a reduction in RI alpha expression at both mRNA and protein levels and inhibition of cell growth. The growth inhibition was accompanied by changes in cell morphology, cleavage of poly(ADP-ribose) polymerase (PARP) and appearance of apoptotic nuclei. In addition, bcl-2 protein level was reduced and p53 expression increased in growth arrested cells. Interestingly, RI alpha antisense inhibited cell viability and induced apoptosis in the absence of p53, suggesting that these actions of RI alpha antisense are exerted independent of p53. In contrast, two- and four-base mismatched control oligonucleotides had no effect on either cell growth or morphology. These results demonstrate that the RI alpha antisense, which efficiently depletes the growth stimulatory molecule RI alpha, induces cell differentiation and apoptosis, providing a new approach to combat breast cancer cell growth.

Deletion of the loop region of Bcl-2 completely blocks paclitaxel-induced apoptosis

At high concentrations, the tubule poison paclitaxel is able to kill cancer cells that express Bcl-2; it inhibits the antiapoptotic activity of Bcl-2 by inducing its phosphorylation. To localize the site on Bcl-2 regulated by phosphorylation, mutant forms of Bcl-2 were constructed. Mutant forms of Bcl-2 with an alteration in serine at amino acid 70 (S70A) or with deletion of a 60-aa loop region between the alpha1 and alpha2 helices (Deltaloop Bcl-2, which also deletes amino acid 70) were unable to be phosphorylated by paclitaxel treatment of MDA-MB-231 cells into which the genes for the mutant proteins were transfected. The Deltaloop mutant completely inhibited paclitaxel-induced apoptosis. In cells expressing the S70A mutant, paclitaxel induced about one-third the level of apoptosis seen with wild-type Bcl-2. To evaluate the role of mitogen-activated protein kinases (MAPKs) in Bcl-2 phosphorylation, the activation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 was examined. Paclitaxel-induced apoptosis was associated with phosphorylation of Bcl-2 and activation of ERK and JNK MAPKs. If JNK activation was blocked by transfections with either a stress-activated protein kinase kinase dominant-negative (K-->R) gene (which prevents the activation of a kinase upstream of JNK) or MAPK phosphatase-1 gene (which dephosphorylates and inactivates JNK), Bcl-2 phosphorylation did not occur, and the cells were not killed by paclitaxel. By contrast, neither an ERK inhibitor (PD098059) nor p38 inhibitors (SB203580 and SB202190) had an effect on Bcl-2 phosphorylation. Thus, our data show that the antiapoptotic effects of Bcl-2 can be overcome by phosphorylation of Ser-70; forms of Bcl-2 lacking the loop region are much more effective at preventing apoptosis than wild-type Bcl-2 because they cannot be phosphorylated. JNK, but not ERK or p38 MAPK, appear to be involved in the phosphorylation of Bcl-2 induced by paclitaxel.

Synergistic effects of retinoic acid and 8-Cl-cAMP on apoptosis require caspase-3 activation in human ovarian cancer cells

We investigated the intracellular mechanisms of retinoic acid (9-cis-RA, 13-cis-RA or all-trans-RA) and a cyclic AMP analog 8-Cl-cAMP on growth-inhibition and apoptosis in human ovarian cancer NIH: OVCAR-3 and OVCAR-8 cells. The cyclic AMP analog, 8-Cl-cAMP, acted synergistically with RA in inducing and activating retinoic acid receptor beta (RARbeta) which correlated with the growth inhibition, cell cycle arrest, and apoptosis in both cell types. In addition, combined treatment of cells with RA plus 8-Cl-cAMP resulted in the release of cytochrome c, loss in mitochondrial membrane potential and activation of caspase-3 followed by cleavage of anti-poly(ADP-ribose)polymerase and DNA-dependent protein kinase (catalytic subunit). Interestingly, inhibition of caspase-3 activation blocked RA plus 8-Cl-cAMP induced apoptosis. Furthermore, mutations in a CRE-related motif within the RARbeta promoter resulted in loss of both transcriptional activation of RARbeta and synergy between RA and 8-Cl-cAMP. Thus, RARbeta can mediate RA and/or cyclic AMP action in ovarian cancer cells by promoting apoptosis. Loss of RARbeta expression, therefore, may contribute to the tumorigenicity of human ovarian cancer cells. These findings suggest that RA and 8-Cl-cAMP act in a synergistic fashion in inducing apoptosis via caspase-3 activation, and may have potential for combination biotherapy for the treatment of malignant disease such as ovarian cancer.

Developmental expression and regulation of basic fibroblast growth factor and vascular endothelial growth factor in rat decidua and in a decidual cell line

During pregnancy, the decidua is comprised of two separate tissues located either mesometrially or antimesometrially in the uterus. Trophoblast invasion takes place only in the mesometrial decidua, where extensive angiogenesis, essential for successful implantation, occurs. Both basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) have been implicated in this phenomenon. The aim of this study was to determine whether the expression of both growth factors is intrinsic to decidua and occurs in the absence of conceptuses, whether their genes are expressed specifically in the mesometrial decidua, the site of angiogenesis, and whether both growth factors are developmentally and hormonally regulated. Decidual tissue was dissected from pseudopregnant rats and levels of both bFGF and VEGF mRNA were examined in mesometrial and antimesometrial decidua by semi-quantitative RT-PCR at different stages of pseudopregnancy. Although induction of decidualization triggered the mRNA expression of bFGF, VEGF mRNA expression remained unchanged. VEGF mRNA level was similar in both antimesometrial and mesometrial decidua, and remained constant throughout pseudopregnancy. In sharp contrast, bFGF mRNA was highly expressed in the mesometrial decidua at a time when extensive angiogenesis takes place in this tissue. Very little signal was observed in the antimesometrial decidua. To examine the regulation of these growth factors, we used a temperature-sensitive decidual cell line developed by transforming antimesometrial decidual cells with SV-40 tsA 209 mutant virus. These cells express both bFGF and VEGF mRNA. Because progesterone is necessary for decidualization and decidua secretes prolactin (PRL)-related hormones, we examined the role of these hormones on VEGF and bFGF mRNA expressions. Neither progesterone nor PRL had any effect on VEGF mRNA levels. However, bFGF mRNA expression was greatly stimulated by PRL. In conclusion, results of this investigation have revealed that bFGF, but not VEGF, mRNA becomes highly expressed in the mesometrial decidua, where angiogenesis occurs, and where trophoblasts, by invading decidual cells, may promote the release of bFGF. In addition, these results indicate that the locally secreted PRL-like hormone up-regulates the mRNA expression of bFGF.

Expression of Wilms' tumor suppressor gene (WT1) in term human trophoblast: regulation by cyclic adenosine 3',5'-monophosphate

The Wilms' tumor suppressor gene (WT1), which is deleted in some Wilms' tumors, encodes a zinc finger transcription factor. We studied WT1 messenger ribonucleic acid (mRNA) in human term placenta and cytotrophoblasts differentiating into syncytiotrophoblasts in vitro by RT-PCR. The results suggest that WT1 mRNA is expressed in the trophoblasts in a cell-specific fashion. WT1 mRNA expression has been observed to decline remarkably in trophoblast cells after 72 h, when these cells are morphologically differentiated into multinucleated syncytiotrophoblasts. As it is well known that cAMP as a second messenger plays a significant role in cellular proliferation and differentiation of placental cells, we examined the effect of 8-bromo-cAMP on WT1 mRNA expression in undifferentiated cytotrophoblasts and differentiated syncytiotrophoblasts. We observed that cAMP enhanced WT1 mRNA expression in cytotrophoblasts, but remained ineffective in altering WT1 mRNA in syncytiotrophoblasts. In summary, the results of this investigation demonstrate that the WT1 gene is developmentally regulated during trophoblast differentiation. An involvement of the cAMP-mediated system in regulating the WT1 gene in the trophoblast is suggested.

The RIIbeta regulatory subunit of protein kinase A binds to cAMP response element: an alternative cAMP signaling pathway

cAMP, through the activation of cAMP-dependent protein kinase (PKA), is involved in transcriptional regulation. In eukaryotic cells, cAMP is not considered to alter the binding affinity of CREB/ATF to cAMP-responsive element (CRE) but to induce serine phosphorylation and consequent increase in transcriptional activity. In contrast, in prokaryotic cells, cAMP enhances the DNA binding of the catabolite repressor protein to regulate the transcription of several operons. The structural similarity of the cAMP binding sites in catabolite repressor protein and regulatory subunit of PKA type II (RII) suggested the possibility of a similar role for RII in eukaryotic gene regulation. Herein we report that RIIbeta subunit of PKA is a transcription factor capable of interacting physically and functionally with a CRE. In contrast to CREB/ATF, the binding of RIIbeta to a CRE was enhanced by cAMP, and in addition, RIIbeta exhibited transcriptional activity as a Gal4-RIIbeta fusion protein. These experiments identify RIIbeta as a component of an alternative pathway for regulation of CRE-directed transcription in eukaryotic cells.

Involvement of microtubules in the regulation of Bcl2 phosphorylation and apoptosis through cyclic AMP-dependent protein kinase

The Bcl2 family of proteins plays a significant role in regulation of apoptosis. In this study, the microtubule-damaging drugs paclitaxel, vincristine, and vinblastine induced Bcl2 hyperphosphorylation and apoptosis in MCF-7 and MDA-MB-231 cells and reduced Bcl2-Bax dimerization. Paclitaxel or vincristine induced increased expression of Bax, while overexpression of Bcl2 in these cell lines counteracted the effects of low doses of these drugs. In addition, paclitaxel- and vincristine-induced activation of cyclic AMP (cAMP)-dependent protein kinase (protein kinase A [PKA]) induced Bcl2 hyperphosphorylation and apoptosis, which were blocked by the PKA inhibitor Rp diastereomers of cAMP (Rp-cAMP). This finding suggests that activation of PKA due to microtubule damage is an important event in Bcl2 hyperphosphorylation and induction of apoptosis. These microtubule-damaging drugs caused growth arrest in G2-M phase of the cell cycle and had no effect on p53 induction, suggesting that hyperphosphorylation mediated inactivation of Bcl2 and apoptosis without the involvement of p53. By comparison, the DNA-damaging drugs methotrexate and doxorubicin had no effect on Bcl2 hyperphosphorylation but induced p53 expression. Interestingly, paclitaxel or vincristine induced activation of caspase 3 and cleavage of poly(ADP-ribose) polymerase downstream of Bcl2 hyperphosphorylation. These data suggest that there may be a signaling cascade induced by agents that disrupt or damage the cytoskeleton that is distinct from (i.e., p53 independent), but perhaps related to (i.e., involves kinase activation and leads to apoptosis), the cellular response to DNA damage.

Antisense depletion of RIalpha subunit of protein kinase A induces apoptosis and growth arrest in human breast cancer cells

In recent years, several laboratories have explored the possibility of using antisense oligodeoxynucleotides for specific manipulation of gene expression leading to cancer treatment. The enhanced expression of the RIalpha subunit of cyclic AMP-dependent protein kinase type I (PKA-I) has been correlated with cancer cell growth. In the present study, the effects of an antisense oligodeoxynucleotide targeted against RIalpha subunit of PKA-I on growth inhibition and apoptosis in MDA-MB-231 human breast cancer cells were investigated. The growth inhibitory effects of RIalpha antisense oligodeoxynucleotide correlated with a decrease in the RIalpha mRNA and protein levels. The growth inhibition was accompanied by changes in the cell cycle phase distribution, cell morphology, cleavage of poly (ADP-ribose) polymerase (PARP), and appearance of apoptotic nuclei. By comparison, mismatched control oligodeoxynucleotide had no effect. On the basis of these results, it can be suggested that the RIalpha antisense oligodeoxynucleotide, which efficiently depletes the growth stimulatory RIalpha and induces apoptosis/differentiation, could be used as a therapeutic agent for breast cancer treatment.

Differential expression of the estrogen receptors alpha and beta in the rat corpus luteum of pregnancy: regulation by prolactin and placental lactogens

Estradiol, together with PRL and placental lactogens, regulates steroidogenesis and cell hypertrophy in the rat corpus luteum of pregnancy. Although binding experiments have demonstrated the presence of estrogen-binding sites, no evidence exists as to whether the rat corpus luteum of pregnancy expresses the estrogen receptor (ER) genes. In this investigation, we have analyzed the expression of the two ER genes (ER alpha and ER beta) (by RT-PCR and in situ hybridization) in the rat corpus luteum, studied their developmental changes throughout pregnancy, and investigated the regulation of ER alpha and ER beta messenger RNA (mRNA) expression by PRL and placental lactogens. The RT-PCR studies showed that both ER mRNA species (ER alpha and ER beta) are coexpressed in the rat corpus luteum during pregnancy. Whereas ER alpha mRNA increased from early pregnancy, reached a maximum at midpregnancy, and had a remarkable decline before parturition; ER beta mRNA remained constant throughout pregnancy, with a significant decline at parturition. Examination of ER alpha and ER beta mRNA expression at the cellular level, by in situ hybridization, showed ER alpha expressed in both follicles and corpus luteum, with maximal expression at midpregnancy. In parallel with the RT-PCR studies, ER beta mRNA was similarly expressed throughout pregnancy in the corpus luteum, but it was less abundant when compared with small and growing follicles. Western blot analysis revealed two ER immunoreactive proteins in the nuclear fraction obtained from pregnant rat corpus luteum: a 67-kDa moiety, highly expressed at midpregnancy but barely detectable in early and late gestation; and a 61-kDa form that remained developmentally unchanged. Hypophysectomy, performed early in pregnancy, induced a sharp decline in ER alpha mRNA expression but a less-marked reduction in ER beta mRNA levels. PRL treatment reverted the inhibition induced by hypophysectomy in both receptor subtypes. When primary luteinized cells were used to test the effect of PRL, rat placental lactogen I, and rat placental lactogen II on the expression of ER alpha and ER beta mRNA, all these lactogenic hormones stimulated both ER mRNA species in a dose-dependent manner. The regulation of ER mRNA expression was further evaluated in a luteal cell line, termed GG-CL, which apparently expresses only the ER beta mRNA species. Culture of the GG-CL cells, in the presence of PRL, resulted in a dose-related up-regulation of ER beta mRNA expression. In addition, PRL treatment enhanced the binding activity of GG-CL cell nuclear proteins to a classical estrogen response element. Furthermore, in these cells, estradiol treatment induced a dose-dependent up-regulation of the mRNA encoding protein kinase C delta isoform, a well-known estrogen target gene in the corpus luteum of the pregnant rat.

Establishment and characterization of a simian virus 40-transformed temperature-sensitive rat luteal cell line

The primary culture of rat luteal cells and their long-term maintenance have been difficult. Low cellular yields have limited the possibility for the study of gene regulation in luteal cells. The goal of this study was to develop a cell line to serve as a model by which to study the expression and regulation of various genes specific to luteal cells. We attempted to develop a luteal cell line by transformation of large luteal cells through infection with a temperature-sensitive simian virus (SV-40 tsA209) mutant that has a temperature-sensitive mutation required for the maintenance of cell transformation. We report here the successful establishment of such a cell line, designated GG-CL cells. Large luteal cells were purified to homogeneity by flow cytometry from corpora lutea of day 14 pregnant rats, cultured for 24 h, and then infected with the SV-40 tsA209 mutant virus. Transformed cells were maintained at the permissive temperature (33 C) until colonies were identified. Several colonies of transformed cells were isolated and passaged. They multiplied at 33 C and formed multilayers. At the nonpermissive temperature (40 C), cells reverted to the normal differentiated phenotype similar to the primary luteal cells in culture. To determine whether GG-CL cells express the genes found in normal luteal cells, messenger RNA (mRNA) expression was examined by either Northern analysis or RT-PCR with primers specific to each mRNA. GG-CL cells were found to express receptors for interleukin-6 and glucocorticoid, as well as the newly discovered estrogen receptor-beta (ER-beta) and the orphan nuclear receptor nur 77. No receptors for ER-alpha, progesterone, LH, or PRL could be detected. This cell line also expressed 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD), but not cholesterol side-chain cleavage cytochrome P450 (P450scc), 3beta-hydroxysteroid dehydrogenase, or aromatase cytochrome P450 (P450arom). Although the cells did not express the PRL receptor, they did express Janus kinase (JAK2) and signal transducers and activators of transcription (Stat5b), and, when transfected with the PRL receptor, they responded to PRL with a marked inhibition in 20alpha-HSD mRNA expression. In addition, estradiol enhanced ER-beta expression in a dose-dependent manner whereas cAMP stimulation caused a marked and rapid increase in the expression of the orphan receptor nur 77. In summary, a temperature-sensitive cell line was successfully established from the large luteal cells of rat corpora lutea. These cells express key genes encoding enzymes and receptors inherent to this defined luteal cell population and respond to stimulation by PRL, estradiol, and cAMP.

Synergistic effects of 8-chlorocyclic-AMP and retinoic acid on induction of apoptosis in Ewing's sarcoma CHP-100 cells

The enhanced expression of the regulatory subunit of cyclic AMP (cAMP)-dependent protein kinase type I, RIalpha, has been correlated with cancer cell growth. Retinoic acid (RA) has been shown to play an important role in the regulation of proliferation and differentiation in neoplastic cells. In the present study, the effects of cAMP analogue 8-chlorocyclic-AMP (8-Cl-cAMP) and RA (both singly and combined) on growth inhibition and apoptosis in Ewing's sarcoma CHP-100 cells were evaluated. The inhibitory effects of 8-Cl-cAMP and RA (9-cis-RA, 13-cis-RA, and all-trans-RA) on cell viability were time and dose related. The degree of growth inhibition induced by 9-cis-RA was the greatest among all of the RA analogues (13-cis-RA and all-trans-RA) examined. The combined effects of 8-Cl-cAMP and RA on the induction of growth arrest at the G0-G1 stage of the cell cycle, apoptosis, down-regulation of RIalpha, and cleavage of poly(ADP-ribose) polymerase were synergistic. In conclusion, it is clear that RA and 8-Cl-cAMP act in a synergistic fashion and have potential for combination chemotherapy for the treatment of malignant disease.

The decidual prolactin receptor and its regulation by decidua-derived factors

Decidualization of the endometrial stroma in the rat gives rise to two different cell populations, located either mesometrially or antimesometrially in the uterus. We have previously shown that the rat decidua is the site of production and action of a PRL-like hormone. In this investigation we examined, using reverse transcription-PCR, whether and which type of PRL receptor (PRL-R) messenger RNA (mRNA) is expressed in the decidua, whether the receptor is confined only to one cell population, and whether the PRL-R expression is regulated by decidua-derived factors. The results indicate that the uterus of pseudopregnant rats does not express the PRL-R and that decidualization does not trigger a rapid appearance of PRL-R mRNA. It is only 3 days after the induction of decidualization that the long form of the PRL-R was first expressed. Thereafter, mRNAs for both the short (PRL-RS) and the long (PRL-RL) form became detectable in both antimesometrial and mesometrial decidua, although PRL-RL mRNA was much more abundant than PRL-RS. As development proceeded, PRL-R mRNA decreased and disappeared specifically from the antimesometrial decidua, whereas the mesometrial decidua continued to express this receptor mRNA. Concomitant with down-regulation of the PRL-R in the antimesometrial tissue was a rather abrupt expression of activin A. In contrast, the mesometrial tissue that maintained high levels of PRL-R mRNA expressed little activin A, but produced an activin-binding protein, alpha(2)-macroglobulin (alpha(2)MG). To determine whether activin A and alpha(2)MG regulate PRL-R expression, antimesometrial and mesometrial cells were separated by elutriation and maintained in culture in the presence or absence of activin A, alpha(2)MG, or follistatin. Just after cell separation, both cell populations expressed PRL-R, but not activin A. Within 6 h, activin A mRNA and protein became highly expressed in the mesometrial cells, whereas PRL-RL mRNA became undetectable. In contrast, activin A mRNA was at very low levels in the antimesometrial cells, and no activin A protein could be detected in the medium for at least 12 h. In these cells PRL-RL mRNA remained elevated. Addition of activin A to antimesometrial cells caused a marked down-regulation of PRL-RL mRNA expression, whereas addition of alpha(2)MG and follistatin to mesometrial cells prevented the disappearance of PRL-R. In summary, the results of this investigation 1) indicate that decidualization of the endometrial stroma induces the appearance of both forms of the PRL-R mRNAs; 2) show differential expression of the PRL-R mRNA in the two-cell population forming the decidua; 3) establish that this differential expression is due to two key decidual molecules, activin A and alpha(2) macroglobulin; and 4) demonstrate that activin A can cause the decidual cells to lose the PRL-R and that the disappearance of the decidual PRL-R can be prevented by addition to the culture of two activin binding proteins, follistatin and alpha(2) MG.

Effects of short-term treatment of a gonadotropin-releasing hormone agonist on the follicular development and gonadotropin secretion in the rat

The gonadotropin-releasing hormone (GnRH) controls pituitary gonadotropin biosynthesis and secretion and therefore it is indispensable in regulating reproductive function. We have studied the effects of a short term treatment (7-days) of a GnRH-agonist (GnRH-Ag) in vivo (a) on reproductive cyclicity and follicular development and (b) on peripheral gonadotropin secretion of normal cycling rat. GnRH-Ag (0.2, 1 or 5 micrograms/day), administered continuously through an osmotic minipump for 7-days, had a varied effect on ovarian cyclicity as is evident by vaginal cytology and it also decreased ovarian weight. A dose of 1 as well as 5 micrograms/day for 7-days of GnRH-Ag caused the complete demise of early and late antral follicles, whereas a dose of 0.2 microgram/day of GnRH-Ag for 7-days caused a significant decrease in the number of late antral follicles. There was a remarkable increase in the number of atretic follicles in the ovary of rats that were treated with 5 micrograms/day of GnRH-Ag for 7-days. Ovarian histology showed the predominance of corpora lutea in rats treated with 1 or 5 micrograms/day of GnRH-Ag and the interstitial cells in general appeared pycnotic. GnRH-Ag treatment significantly enhanced the serum LH secretion but FSH secretion remained unaffected. Serum PRL concentration diminished in rats that were treated with the highest dose (5 micrograms/day) of GnRH-Ag. Results from this study clearly demonstrate that GnRH-Ag treatment interferes with normal cyclicity of rats and it profoundly affects the follicular development. Therefore, it acts as an atretognic factor in the ovary.

Evaluation of haloperidol, a dopamine antagonist, on intraocular pressure in experimental glaucoma

Haloperidol, a dopaminergic antagonist, was found to be very effective in lowering intraocular pressure in normal and glaucomatous eyes. The potential ocular hypotensive effect of haloperidol can be utilized for the treatment of glaucoma.

Cell-specific expression of activin and its two binding proteins in the rat decidua: role of alpha 2-macroglobulin and follistatin

Rat decidual tissue is formed by two distinct decidual cell populations located either antimesometrially or mesometrially in the uterus. They differ in morphology, the genes they express, the proteins they secrete, and the role they play during pregnancy. Recently, we have shown that rat decidua expresses follistatin and alpha 2-macroglobulin (alpha 2-MG), two binding proteins to activin. In the present study, we determined whether the decidua of pregnant and pseudopregnant rats also expresses activin, whether activin messenger RNA (mRNA) is confined to a particular cell population, and whether it is regulated by its binding proteins. Decidual and placental tissues were collected at different stages of pseudopregnancy or pregnancy. mRNA expression was examined by in situ hybridization, reverse transcription-polymerase chain reaction, and Northern analysis. Developmental studies revealed that activin A became highly expressed in the antimesometrial decidua only from day 11 at a time when this tissue was undergoing extensive degeneration. Very little activin A mRNA could be detected in the mesometrial decidua. However, late in pregnancy, significant expression of activin A mRNA was detected in the mesometrial decidua undergoing extensive cell death at this stage. Developmental study revealed that activin A mRNA became expressed in the antimesometrial decidua only when follistatin mRNA disappeared from this tissue. Furthermore, mesometrial decidua expressing the most alpha 2-MG mRNA had reduced levels of activin A mRNA. These data suggest that follistatin and alpha 2-MG may, by binding to activin, prevent activin A from stimulating the expression of its own gene. To examine this possibility we first established that the rat decidua expresses activin receptor II at a constant level between days 11-15. Then we examined whether follistatin and alpha 2-MG down-regulate activin expression in a simian virus 40-transformed decidual cell line (GG-AD). These cells express activin A mRNA in abundance, very little follistatin, and no alpha 2-MG. Follistatin and alpha 2-MG caused a dose-related decrease in activin A mRNA levels in these cells. The same inhibitory effect was observed with activin A-blocking antibody. In summary, the results of this investigation demonstrate that rat decidual tissue expresses mRNAs for activin A and its two binding proteins; follistatin and alpha 2-MG. The expression of each mRNA is cell specific and developmentally regulated. The finding that both activin-binding proteins and antibody inhibit the expression of activin A in cultured decidual cells suggests that activin regulates its own gene expression in the decidua.(ABSTRACT TRUNCATED AT 400 WORDS)

Follicular development, steroidogenesis and gonadotrophin secretion in response to long-term treatment with a gonadotrophin-releasing hormone agonist in the rat

Gonadotrophin-releasing hormone (GnRH) and its agonists are implicated in the local control of rat ovarian function. We have evaluated the effects of long-term administration of different doses of GnRH agonist (GnRH-Ag) in vivo (a) on reproductive cyclicity and follicular development, (b) on peripheral gonadotrophin and steroid concentrations and (c) on in vitro cAMP and progesterone production by the follicles in response to stimulatory doses of FSH or LH (1 microgram/ml). GnRH-Ag (0.2, 1 or 5 micrograms/day) administration for 28 days had a profound impact on the oestrous cycle of rats as revealed by vaginal cytology. GnRH-Ag treatment caused a decrease in ovarian and uterine weights, which correlated very well with the decrease in the number of follicles present in the ovary. GnRH-Ag (5 micrograms/day) reduced the number of early preantral follicles and there was complete disappearance of early as well as late antral follicles. However, a dose of 1 microgram GnRH-Ag/day was effective in the complete demise of only late antral follicles with a significant attenuation in the number of early antral follicles. There was an enhancement in serum LH concentrations in response to the highest dose of GnRH-Ag administration with serum FSH concentrations declining in rats treated with the two higher doses. However, serum prolactin concentrations were attenuated only in rats treated with the highest dose of GnRH-Ag. GnRH-Ag treatment decreased serum progesterone and oestradiol concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of morphine-induced antinociception by L-glutamic acid at the spinal site in rats

The present experimental study was planned to evaluate the effect of intrathecal administration of L-glutamic acid upon antinociception produced by intrathecal morphine in a prospective-controlled manner in conscious freely mobile Sprague-Dawley albino rats. After chronic catheterization of the spinal subarachnoid space, rats were randomly allocated into 12 treatment groups of ten each and the same number of rats served as saline control for the comparison. L-glutamic acid (100 mmol), morphine (1.2 mmol), ketamine (50 mmol) and saline (150 mmol) were injected intrathecally in 5 microliters volumes. Naloxone was injected in a dose of 1 mg.kg-1 im. Immediately before and 15, 30 min, 1, 2 and 3 hr after injection, rats were subjected to a thermal noxious stimulus, using a tail-flick technoanalgesiometer and tail-flick latencies (TFL) were recorded. Intrathecal administration of L-glutamic acid attenuated the antinociceptive effect of intrathecal morphine with a decrease in TFL (1.4 +/- 0.3 sec; P < 0.0001) from 6.6 +/- 0.3 sec. Ketamine led to abolition of this effect (P < 0.01). In rats, pretreated with naloxone, there was restoration as well as augmentation of morphine-induced antinociception in the presence of L-glutamic acid with an increase in TFL (9.0 +/- 0.4 sec; P < 0.0001). We conclude that there is modulation of opioid receptors by L-glutamic acid at the spinal site in rats.

Effect of nitrendipine, nimodipine and nisoldipine on experimentally induced myocardial infarction in rats

Cardiac necrosis was produced in rats by administering isoproterenol sulphate (85 mg/kg, sc for 4 days). The myocardial damage was proved by observing the elevated levels of serum aspartate aminotransferase, ++alanine aminotransferase and lactate dehydrogenase and the changes were confirmed by his topathology. Nitrendipine, nimodipine and nisoldipine (10 mg/kg, ip) significantly reduced the elevated levels of these enzymes. The average degree of cardiac necrosis in these rats when observed microscopically and histologically was also found to be significantly reduced on pretreatment with these drugs. Nisoldipine was more effective in preventing cardiac necrosis as compared to nitrendipine and nimodipine.

Development and characterization of a simian virus 40-transformed, temperature-sensitive rat antimesometrial decidual cell line

The rat decidual tissue is formed by two cell populations, which express different genes and play diverse roles in pregnancy. Cells that decidualize in the antimesometrial region secrete several hormones and serve as a true endocrine gland. Isolation and maintenance of these decidual cells in primary culture is difficult. The goal of these experiments was to develop a cell line to serve as a model to study the expression and regulation of various genes specific to the antimesometrial decidual cells. Decidualization was induced in pseudopregnant rats. The antimesometrial decidua was dissected out, and cells were enzymatically dissociated and were cultured for 18 h at 37 C in RPMI-1640 medium containing 10% fetal bovine serum. Cells were washed repeatedly and then infected with a temperature-sensitive mutant of the simian virus. Transformed cells were maintained at the permissive temperature (33 C) until colonies were identified and harvested. Whereas primary cells in culture did not divide, the cloned decidual cell lines demonstrated transformed features; they multiplied at 33 C and formed multilayers. At the nonpermissive temperature (39 C), cell replication decreased, and after 4 days of culture the cells lost their transformed phenotype and continued to grow as a monolayer similar to primary cells. Cells under these conditions also assumed morphological characteristics similar to antimesometrial cells: polynucleated, large, and having cytoplasm filled with lipid droplets. Interestingly, cells cultured at 39 C that were shifted back to 33 C resumed rapid growth. To determine whether these cells also express messenger RNAs (mRNAs) found in normal antimesometrial decidual cells, the presence of activin beta A mRNA was investigated by Northern analysis and reverse transcription polymerase chain reaction. A single 6.8-kilobase activin beta A transcript was expressed abundantly at both 33 and 39 C, indicating that even when cells are rapidly dividing they express activin beta A. Activin beta B mRNA was also expressed in these cells, although in lower abundance, as were two binding proteins for activin, activin receptor II and follistatin. The activin beta A and beta B genes were responsive to cAMP stimulation in these cells. Since the hallmark of the antimesometrial decidual cells is the secretion of PRL-related hormones, the expression of decidual PRL-related protein and PRL-like protein B was examined. Northern analysis revealed a major 1.2-kilobase transcript of PRL-like protein B expressed equally at both temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute immobilization stress alters LH and ACTH release in response to administration of N-methyl-D,L-aspartic acid in peripubertal and adult male rats

We have evaluated the effects of stress on the pituitary hormone response to N-methyl-D,L aspartic acid (NMA) in peripubertal (43 day old) and adult (80 day old) male rats. Animals were stressed by immobilization for 3 h. Fifteen min prior to the end of the stress period, animals were injected sc with either vehicle or increasing doses of NMA (10, 30 or 60 mg/kg BW). Animals were sacrificed 15 minutes later. A significant rise in plasma LH in response to NMA occurred at a lower dose (10 versus 60 mg/kg BW), and the magnitude of the response was greater overall in peripubertal than in adult unstressed rats. Stress altered the LH response to NMA in both age groups. In peripubertal stressed rats, NMA did not induce a rise in plasma LH levels. In adult rats exposed to stress, the magnitude of the LH response to 60 mg/kg BW of NMA was lower than in unstressed animals. NMA administration triggered a rise in plasma ACTH levels in unstressed rats of both age groups, but the magnitude of the rise was greater in adults than in peripubertal animals. Stress reduced the ACTH response to NMA administration in both age groups. Plasma FSH concentrations were higher in peripubertal animals than in adults. NMA and stress were without major effect on plasma FSH levels in either age group. These data suggest that excitatory amino acids (EAA) form an important component in the regulatory processes governing the release of LH and ACTH, and that the maturational stage of the central nervous system and exposure to stress alter the LH and ACTH response to EAA.

Inhibition of luteal steroidogenesis by two LHRH antagonists (Nal-Glu and Nal-Arg antagonists) in the pregnant rat

We have examined the effect of two LHRH antagonists (Nal-Glu and Nal-Arg antagonists) on the basal progesterone (P4), pregnenolone (P5) and 20 alpha-dihydroprogesterone (20 alpha-DHP) production by luteal cells obtained from day 8 pregnant rats. A dose of 0.1 mmol/l of Nal-Glu or Nal-Arg attenuated basal P4 production by luteal cells after 12, 24 or 48 h of incubation. P5, a precursor for P4 synthesis was also reduced by both doses of Nal-Glu or Nal-Arg (0.1 mmol or 0.1 mumol/l) after 24 h of incubation. A period of 12 h was not sufficient to inhibit P5 production by luteal cells incubated with both doses of Nal-Glu or with the lower dose of Nal-Arg. The higher dose of Nal-Glu and Nal-Arg remained effective in attenuating P5 production by luteal cells after 48 h of incubation. We measured the production of a metabolite of P4, i.e., 20 alpha-DHP to assess whether this suppression in P4 production is due to an enhancement in the P4 metabolism by increasing the activity of 20 alpha-hydroxydehydrogenase. However, instead, we observed (i) a decrease in the production of 20 alpha-DHP by the higher dose of Nal-Glu and Nal-Arg after 12, 24 or 48 h of incubation and (ii) a decrease or no change in the production of 20 alpha-DHP by the lower dose of Nal-Glu or Nal-Arg at all time periods of incubation. Based on these observations we conclude that LHRH antagonists exert a direct effect on the corpus luteum and suppress luteal steroidogenesis. This suppression in luteal steroidogenesis could be due to a decrease in the activity of any one of these enzymes of the steroidogenic pathway, viz., cholesterol side chain cleavage (P450scc), a rate limiting enzyme involved in the synthesis of P5 from cholesterol, or 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), which catalyzes the oxidation of P5 to P4 or due to a decrease in activity of both enzymes.

Expression of decidual prolactin-related protein in the rat decidua

It is well established that rat decidual tissue produces a PRL-like hormone(s) that binds to the PRL receptor on both the corpus luteum and the decidual cells and initiates profound changes in the endocrine milieu required for the establishment of pregnancy. The recent cloning of a decidual PRL-related protein (dPRP) prompted us 1) to determine whether the expression of this gene is triggered by decidualization of the endometrial stromal cells, 2) to examine the temporal and cell-specific pattern of its expression, and 3) to examine the role of both decidual signals and PRL on levels of its messenger RNA (mRNA). Total RNA was isolated from uteri of either nonpseudopregnant rats or pseudopregnant rats with or without decidual tissue. A 1-kilobase mRNA species hybridizing strongly with the dPRP probe was present in decidualized uteri. No dPRP mRNA could be detected in uteri not subjected to decidualization. Developmental studies indicated a constant high level of dPRP mRNA in the decidual tissue until day 12 of pseudopregnancy, followed by a marked decline at a time when extensive cell death occurs in the decidua, suggesting that dPRP is constitutively expressed in this tissue. To examine the cell-specific expression of dPRP, antimesometrial decidua was separated from mesometrial decidua, and the large antimesometrial cell population was separated from the small mesometrial cells by elutriation. The results of Northern analysis revealed clearly that dPRP is abundantly and solely expressed in the large antimesometrial cells. No dPRP mRNA could be detected in the mesometrial cells and in numerous other endocrine and nonendocrine tissues. A faint signal was observed, however, in the trophoblast. Despite the very strong paracrine regulation between the antimesometrial and mesometrial cells and the high levels of PRL receptor expression in these cells, both in vivo and coculture experiments revealed no regulation of dPRP gene expression by either PRL or mesometrial cell signal, adding further support to the possibility that once induced, dPRP remains constitutively expressed. In summary, the results of this investigation revealed that the expression of dPRP in endometrial stromal cells is triggered by the induction of decidualization and that this gene is selectively and abundantly expressed in a defined cell population located in the anti-mesometrial region of the uterus. Thus, dPRP is not only a useful indicator of decidualization, but is also an excellent marker for the differentiated antimesometrial cells.

Suppression of luteal steroidogenesis by an LHRH antagonist (Nal-Lys antagonist: antide) in vitro during early pregnancy in the rat

LHRH and its analogues are known to exert direct effects on the ovary. Herein we have described a direct inhibitory effect of an LHRH antagonist (Nal-Lys antagonist: antide) on the basal progesterone (P4) and pregnenolone (P5) production by luteal cells obtained from the day-8 pregnant rat. Luteal cells incubated with two doses of antide (10(-4) and 10(-7) M) for 24 or 48 h showed suppression of P4 production. P5 production was suppressed by both doses of antide within 12 h of incubation. Neither dose of antide interfered with P5 production when the duration of incubation was extended beyond 12 h. The 20 alpha-dihydroprogesterone yield from the luteal cells treated with these doses of antide remained unaffected. We estimated the activities of the cholesterol side-chain cleavage (P450scc) enzyme (which is a key enzyme involved in the conversion of cholesterol to P5) and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) (which catalyses the conversion of P5 to P4) in the luteal cells treated with different doses of antide. Both doses of antide suppressed the activity of the P450scc enzyme after 12 h of incubation and the 3 beta-HSD content of the luteal cells after 48 h of incubation. These observations indicate that antide exerts a direct inhibitory effect at the level of the corpus luteum, that differential suppression of P5 and P4 during different periods of incubation with antide is due to a defect in either the P450scc or the 3 beta-HSD enzyme system, or both.

Insulin as an amplifier of gonadotropin action on steroid production: mechanisms and sites of action in goldfish prematurational full-grown ovarian follicles

The present study examines the effects of mammalian insulin and insulin-like growth factor-I (IGF-I) on steroid production by goldfish vitellogenic and prematurational full-grown ovarian follicles in vitro. Insulin (0.4-40 micrograms/ml) had no effect on its own, but potentiated human chorionic gonadotropin (hCG) and 25-hydroxycholesterol-stimulated testosterone production by prematurational full-grown follicles in both a dose- and time-dependent manner. By comparison, in vitellogenic follicles insulin (4 micrograms/ml) had no effect on hCG- or 25-hydroxycholesterol-stimulated testosterone and 17 beta-estradiol production. IGF-I (11-100 ng/ml) neither affected basal nor hCG- and 25-hydroxycholesterol-stimulated testosterone production by vitellogenic or prematurational full-grown follicles. Studies to determine the site(s) of action of insulin showed that insulin had no effect on basal cyclic adenosine 3',5'-monophosphate (cAMP) generation, but it enhanced hCG-stimulated cAMP and testosterone production by prematurational full-grown follicles. Insulin also enhanced conversion of 25-hydroxycholesterol to testosterone, but had no effect on the metabolism of pregnenolone, suggesting that insulin either enhances mobilization of cholesterol to the mitochondria or increases the activity of the cytochrome P450 side-chain cleavage enzyme. The ability of insulin to enhance hCG and/or 25-hydroxycholesterol-stimulated testosterone production was blocked by the addition of the protein kinase A (PKA) inhibitor H89, which confirmed that these actions of insulin are exerted, at least in part, by the cAMP/PKA pathway. These findings suggest that insulin, but not IGF-I, is capable of participating in the regulation of ovarian steroid biosynthesis through effects at multiple steps within the steroid cascade and that ovarian responsiveness to insulin changes during the course of follicular development in the goldfish. Together, these results provide new insights into the biological action of insulin in the fish ovary.