Marco Cerbón

Progesterone receptor isoforms are differentially regulated by sex steroids in the rat forebrain.

WE studied the effects of estradiol (E2) and progesterone (P4) on expression of genes coding for PR isoforms in the forebrain of ovariectomized rats by RT-PCR analysis. In the hypothalamus the expression of both PR isoforms was induced by E2 and down-regulated by P4. In the preoptic area these changes were only observed in the PR-B isoform. In contrast, in the hippocampus PR induction by E2 was only observed for PR-A. In this region P4 did not modify the expression of any PR isoform. These results indicate that PR isoforms expression is differentially regulated by sex steroid hormones in distinct forebrain regions and suggest that the tissue-specific regulation of either PR-A or PR-B may be involved in the physiological actions of P4 upon the rat brain.

Progesterone receptor isoforms expression pattern in the rat brain during the estrotts cycle

Progesterone receptor (PR) isoforms expression was determined in the hypothalamus, the preoptic area, the hippocampus and the frontal cerebral cortex of the rat at 12:00 h on each day of the estrous cycle by using reverse transcription coupled to polymerase chain reaction. Rats under a 14:10 h light-dark cycle, with lights on at 06:00 h were used. We found that PR-B isoform was predominant in the hypothalamus, the preoptic area and the frontal cerebral cortex. Both PR isoforms were similarly expressed in the hippocampus. The highest PR-B expression was found on proestrus day in the hypothalamus; on metestrus in the preoptic area; and on diestrus in the frontal cortex. We observed no changes in PR isoforms expression in the hippocampus during the estrous cycle. These results indicate that PR isoforms expression is differentially regulated during the estrous cycle in distinct brain regions and that PR-B may be involved in progesterone actions upon the hypothalamus, the preoptic area and the frontal cortex of the rat.

Progesterone receptor isoforms expression in the prepuberal and adult male rat brain

Progesterone receptor (PR) isoforms expression was determined in several regions of the prepuberal and adult male rat brain by using reverse transcription coupled to polymerase chain reaction. Rats under a 14:10-h light-dark cycle, with lights on at 0600 h were used. We found that in the hypothalamus of prepuberal animals the expression of both PR isoforms was similar, whereas PR-A expression was higher than that of PR-B in adults. In the cerebellum PR-B expression was predominant in both prepuberal and adult rats. In both ages PR-A and PR-B exhibited a non-significant tendency to be predominant in the hippocampus and the preoptic area respectively. In the frontal cortex and the olfactory bulb PR isoforms were expressed at a similar level. These results indicate a differential expression pattern of PR isoforms in the male rat brain and suggest that the tissue-specific expression of PR-A and PR-B is important for the appropriate response of each cerebral region to progesterone.

MOLECULAR MECHANISMS INVOLVED IN THE DIFFERENTIAL EFFECTS OF SEX STEROIDS ON THE REPRODUCTION AND INFECTIVITY OF TAENIA CRASSICEPS

The in vitro exposure of Taenia crassiceps cysticerci to 17-β estradiol (E2) and progesterone (P4) stimulated their reproduction and infectivity. Testosterone (T4) and dihydrotestosterone (DHT) inhibited their reproduction and reduced their motility and infectivity. E2 and P4 increased, whereas T4 and DHT reduced, the expression of parasite c-fos and c-jun and DNA synthesis. In vitro exposure of cysticerci to sex steroids before their inoculation into recipient noninfected mice resulted in large parasite loads when pretreated with E2 and P4 and in smaller loads when pretreated with T4 and DHT. To determine the possible molecular mechanisms by which sex steroids affect T. crassiceps, sex steroid receptors were amplified. Taenia crassiceps expressed estrogen receptors (both α and β isoforms) and androgen receptors but no P4 receptors. These results demonstrate that sex steroids act directly on parasite reproduction by binding to a classic and specific sex steroid receptor on the parasite. The differential response of cysticerci to sex steroids may also be involved in their ability to grow faster in the murine female or feminized male host. This is the first report of direct sex steroid effects on the parasite possibly through sex steroid receptors in the cysticerci.

Progesterone receptor isoforms expression pattern in human astrocytomas

Progesterone receptors (PR) have been detected in human astrocytomas; however, the expression pattern of PR isoforms in these brain tumors is unknown. Progesterone receptor isoforms expression was studied in 13 biopsies of astrocytomas (6 grade III, and 7 grade IV) from adult Mexican patients by using reverse transcription-polymerase chain reaction and immunohistochemistry. Progesterone receptor expression was observed at mRNA and at protein levels in 66% and 83% of astrocytomas grade III, respectively, whereas 100% of astrocytomas grade IV expressed PR. Almost all PR mRNA content in astrocytomas grades III and IV corresponded to PR-B. The number of immunoreactive cells expressing PR-B was higher than that expressing PR-A in 73% of the cases. Estrogen receptor-alpha protein was only observed in 33% of astrocytomas grade III, whereas no astrocytomas grade IV expressed it. These data suggest that PR-B is the predominant isoform expressed in human astrocytomas grades III and IV, and that estrogen receptor-alpha is not expressed in astrocytomas grade IV.

Intracellular progesterone receptors are differentially regulated by sex steroid hormones in the hypothalamus and the cerebral cortex of the rabbit

The aim of this study was to examine the role of sex steroid hormones in the regulation of intracellular progesterone receptors (PR) in the rabbit central nervous system. We determined PR concentration in cytosol preparations from the hypothalamus, the frontal, tempo-parietal and occipital cortex, by using the specific binding of the synthetic progestin [3H]ORG 2058. PR concentration was higher in the hypothalamus of intact adult females than in that of adult males and prepubertal females, whereas no significant differences were observed in the cerebral cortex of these animals. PR concentration was similar in the three cortical regions analyzed, indicating a homogeneous distribution of PR in the cerebral cortex. The administration of estradiol to ovariectomized animals increased PR concentration in the hypothalamus but not in the cortex. The administration of progesterone to ovariectomized rabbits did not modify PR concentration in any region, however when progesterone was administered after estradiol, it induced a significant diminution in hypothalamic PR concentration without effects in the cortex. These findings suggest that in the rabbit, PR are estrogen regulated in the hypothalamus but not in the cerebral cortex. In the latter, PR are not regulated by progesterone, whereas in the former the estrogen-induced PR are down-regulated by progesterone. Interestingly, hypothalamic PR constitutively expressed in ovariectomized animals are progesterone-insensitive.

Regulation of progesterone receptor gene expression by sex steroid hormones in the hypothalamus and the cerebral cortex of the rabbit

The effects of estradiol benzoate (EB) and progesterone (P4) upon progesterone receptor (PR) gene expression in the cerebral cortex and the hypothalamus of the rabbit were studied. Ovariectomized adult rabbits were subcutaneously treated with EB (25 micrograms/kg) for 2 days, and with EB (25 micrograms/kg) + a single dose of P4 (5 mg/kg) on day 3. Twenty-four hours after the last dose, the frontal cortex, the hypothalamus and the uterus were excised, total RNA was extracted and processed for reverse transcription-polymerase chain reaction. PR gene expression was induced by EB and down-regulated by P4 both in the frontal cortex and the hypothalamus in a manner similar to that observed in the uterus. The finding that PR gene transcription is regulated by steroid hormones in the cerebral cortex suggests that post-transcriptional processes are involved in the insensitivity of cortical PR protein to steroids regulation previously reported with binding techniques.

Nerve Growth Factor Increases in Pancreatic β Cells After Streptozotocin-Induced Damage in Rats

We investigated short-term in vivo and in vitro effects of streptozotocin (STZ) on pancreatic β cells. Male Wistar rats were treated with 75 mg/kg STZ, and, after 4 hrs blood glucose and insulin were measured and islet cells were isolated, cultured for 16 hrs, and challenged with 5.6 and 15.6 mM glucose. Treated rats showed hyperglycemia (14 mM) and a 70% decrease in serum insulin levels as compared with controls. Although insulin secretion by isolated β cells from STZ-treated rats was reduced by more than 80%, in both glucose concentrations, nerve growth factor (NGF) secretion by the same cells increased 10-fold. Moreover, NGF messenger RNA (mRNA) expression increased by 30% as compared with controls. Similar results were obtained in an in vitro model of islet cells, in which cells were exposed directly to STZ for 1, 2, and 4 hrs and then challenged for 3 hrs with the same glucose concentrations. Our data strongly suggest that an early increase in NGF production and secretion by β cells could be an endogenous protective response to maintain cell survival and that diabetes mellitus may occur when this mechanism is surpassed.

The Protective Effect of Testosterone on Streptozotocin-induced Apoptosis in β Cells Is Sex Specific

Objectives: To investigate the protective role of steroid hormones on streptozotocin (STZ)-induced apoptosis in rat pancreatic &bgr; cells. Methods: Two sets of experiments were performed. In the first, male rats were orchidectomized and substituted 72 hours later with testosterone, estradiol, or progesterone, and 24 hours later, administered with STZ. Subjects were killed 6 hours later, and apoptosis was determined in sections of the pancreas. In the second experiment, male or female rats were gonadectomized, were further substituted with testosterone, and then administered STZ. Six hours later, the animals were killed, and apoptosis, as well as immunoreactive expression of insulin, catalase, or Cu/Zn superoxide dismutase, was determined in sections of the pancreas. In addition, gonadectomized male or female subjects were substituted with testosterone and administered STZ, and 24 hours later, serum glucose and insulin were measured. Results: It was found that the cytoprotective effect was only shown in testosterone-treated male rats but not progesterone- or estradiol-treated male rats. In addition, the effect was seen in male rats but not in female rats, and there was an inverse correlation between apoptotic index and antioxidant enzyme immunoreactivity. Conclusions: The cytoprotective effect of testosterone is sex specific and is related to the induction of antioxidant enzyme activities in pancreatic &bgr; cells.

Administration of bisphenol A to dams during perinatal period modifies molecular and morphological reproductive parameters of the offspring.

Bisphenol A (BPA) is an estrogenic agonist compound that induces changes in diverse reproductive parameters in rats. The aim of the present study was to determine the effects of BPA given in drinking water containing 10mg/L (approximate dose 1.2mg/kg BW/day), administered chronically to rats during pregnancy and lactation, on reproductive tract parameters of the offspring. 79.2% of the female offspring from BPA-treated mothers presented irregular estrous cycles. As compared to the control group, a significant increase in the thickness of the uterine epithelia and stroma was observed in the BPA group. Additionally, 60% of the female offspring from BPA mothers did not undergo abundant uterine epithelial apoptosis during the estrus phase of the cycle while control animals did. In addition, a down regulation of ERα expression was observed in epithelial cells on estrus day. The results indicate that BPA, when administered chronically in water beverages to dams, modifies the reproductive cycle of the offspring during young adulthood.