1alpha, 25-dihydroxy-vitamin D3 alters Syk activation through FcgammaRII in monocytic THP-1 cells

In monocytes and macrophages, activation of the tyrosine kinase Syk is an essential step in the biochemical cascade linking aggregation of receptors for immunoglobulin G (FcgammaR) to initiation of effector functions. An increase in Syk activation during differentiation of myeloid cells by different agents has been reported. We studied the activation state of Syk in response to FcgammaRII crosslinking in monocytic cells before and after in vitro differentiation with 1alpha, 25-dihydroxy-vitamin D3. We show here that while in undifferentiated THP-1 cells clustering of FcgammaRII induces significant phosphorylation and activation of Syk, in THP-1 cells differentiated in vitro by 1alpha, 25-dihydroxy-vitamin D3, FcgammaRII crosslinking induced a decrease in Syk activity. In vitro differentiation did not induce changes in the expression of FcgammaRII isoforms. The observed effect on Syk activation though FcgammaRII could be mediated by differentiation-induced changes in the expression and basal activation level of Syk, as well as changes in the association of Syk with the tyrosine phosphatase SHP-1. These results suggest that the biochemical signaling pathways induced by FcgammaRII could be dependent on the differentiation state of the cell.     

Expression of p53 in luminal and glandular epithelium during the growth and regression of rat uterus during the estrous cycle

It has been well recognized that epithelial cells of the rat endometrium cyclically proliferate and die during the estrous cycle. The aim of the present study was to determine p53 expression pattern and correlate it with the the apoptotic pattern of epithelial cells of the rat uterus during the estrous cycle. The p53 mRNA and protein expression pattern was assessed by in situ hybridization and immunohistochemistry. The apoptotic index was determined by using terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) and electron microscopy. The highest p53 mRNA content, detected by in situ hybridization, was observed on the metestrus day both in the luminal and the glandular epithelia. During this period both epithelia presented high proliferation. The content of p53 mRNA markedly decreased in the following days, presenting its minimal values on the estrus day. The highest number of p53 immunopositive nuclei, in both the luminal and the glandular epithelia, was also detected on the metestrus day, while the lowest one was found on estrus day. On the proestrus day, p53 protein was predominantly detected in the glandular epithelium. However, on the estrus day, p53 protein was detected both in the nuclei and in the cytoplasm of luminal epithelial cells, predominantly in the cytoplasm. The highest apoptotic index in both the luminal and the glandular epithelia was observed on the estrus day whereas the lowest one was observed on the proestrus day. The apoptotic index values were higher in the luminal than in the glandular epithelia. The overall results indicate that p53 expression at both mRNA and protein levels is higher on the metestrus day when the apoptotic index is low. This suggests that p53 should play an important physiological role during proliferative phases of the estrous cycle in the rat uterus.     

Progesterone receptor isoforms in ovary of newly-hatched chick after gonadotropin treatment during embryonic development

We evaluated by immunohistochemistry the expression of progesterone receptor (PR) isoforms in different cell subpopulations of the ovary of newly-hatched chicks after a treatment with Follicle-stimulating hormone (FSH) or Luteinizing hormone (LH) administered on days 13, 15 and 17 of embryonic development. Two monoclonal antibodies that recognize either both PR isoforms or only PR-B, were used. The results indicate that FSH increased both the total number of cells and the number of PR-immunoreactive ones in all cell subpopulations of the ovary. In all cases, PR-B was the isoform regulated by FSH. In contrast, LH did not modify the number of total cells in any cell subpopulations of the ovary. Besides, LH decreased the number of PR-B immunoreactive interstitial cells, without modifying PR expression in any other cell subpopulations of the ovary. These results reveal differential effects of FSH and LH on PR-expression in cell subpopulations of the ovary of newly hatched chicks treated during embryonic development. We conclude that gonadotropins regulate PR-B isoform in the prefollicular ovary of the chick.     

Sexual dimorphism in the content of progesterone and estrogen receptors, and their cofactors in the lung of adult rats

Progesterone and estradiol play an important role in the regulation of lung functions such as ventilation and vasoconstriction. The genomic actions of progesterone and estradiol are mediated by their nuclear receptors: progesterone receptors (PR) and estrogen receptors (ER). These actions are linked to interactions between steroid receptors and some cofactors that function as coactivators or corepressors. In this work we determined the content of PR isoforms, ER-beta, one coactivator (SRC-1), and one corepressor (SMRT) in the lung of both female rats during the estrous cycle and intact males by Western blot. The rat lung presented a higher content of PR-A than that of PR-B during the estrous cycle. The highest content of both PR isoforms was observed on the day of proestrus whereas the lowest one was found on the day of estrus. In contrast, the content of ER-beta was the lowest on the day of proestrus and it increased at estrus. The content of SRC-1 and SMRT increased on the day of diestrus. SRC-1 content decreased at proestrus and estrus, while SMRT content decreased at proestrus and increased again at estrus. In the lung of adult male rats the content of PR isoforms, ER-beta and SMRT was lower than in that of females, whereas the content of SRC-1 was similar in both sexes. Our results suggest a sexual dimorphism in the content of PR, ER-beta, and SMRT in the rat lung as well as a relation of their content to the physiological levels of progesterone and estradiol.     

Biotin deficiency and biotin excess: Effects on the female reproductive system

Biotin deficiency and biotin excess have both been found to affect reproduction and cause teratogenic effects. In the reproductive tract, however, the effects of biotin have not been well established yet. We investigated the effects of varying biotin content diets on the oestrus cycle, ovarian morphology, estradiol and progesterone serum levels, and the uterine mRNA abundance of their nuclear receptors, as well as on the activity of the estradiol-degrading group of enzymes cytochrome P450 (CYP) in the liver. Three-week-old female BALB/cAnN Hsd mice were fed a biotin-deficient, a biotin-control, or a biotin-supplemented diet (0, 7.2 or 400 μmol of free biotin/kg diet, respectively) over a period of nine weeks. Striking effects were observed in the biotin-deficient group: mice showed arrested estrous cycle on the day of diestrus and changes in ovary morphology. Estradiol serum concentration increased 49.2% in biotin-deficient mice compared to the control group, while the enzymatic activities of CYP1A2 and CYP2B2 increased (P < 0.05). The mRNA abundance of nuclear estrogen and progesterone receptors decreased in the biotin-deficient mice. In the biotin-supplemented group we found that, in spite of a significant (P < 0.05) decrease in the number of primary and Graafian follicles and in CYP1A2 activities, mice exhibited 105.4% higher serum estradiol concentration than the control group. No changes in the expression of the nuclear receptors were observed. No significant differences were observed in serum progesterone among the groups. Our results indicate that both the deficiency and the excess of biotin have significant effects on the female mouse reproductive system.     

Immunocytochemical detection of estrogen and progesterone receptors in the rabbit submandibular gland.

Rabbit submandibular glands produce secretions involved in olfactory communication. The histology of these glands and their secretory activity are: sexually dimorphic; vary across the female reproductive cycle; and are modified by gonadectomy. This suggests that gonadal steroids regulate the structure and function of such glands. To further support this idea we assessed by immunocytochemistry the presence of estrogen and progesterone receptors in male and female rabbit submandibular glands. Immunoreactivity was detected only in the nucleus of acini cells. The number of estrogen receptor-immunoreactive cells/field varied among estrus (26 +/- 6; mean +/- S.E.), ovariectomized (19 +/- 2), and ovariectomized-estrogen-treated animals (13 +/- 3). Intact males showed a significantly smaller number of estrogen receptor-immunoreactive cells/field (12 +/- 1) than estrous females. Interestingly, progesterone receptor-immunoreactive cells were more abundant in estrous (32 +/- 7) than in ovariectomized animals (7 +/- 1). Estradiol benzoate (5 micrograms daily for 5 days) increased the number of progesterone receptor-immunoreactive cells/field in ovariectomized females (17 +/- 1). Intact males showed fewer progesterone receptor-immunoreactive cells/field (16 +/- 2) than estrous females. Results show that the rabbit submandibular gland is a target for estrogen and progesterone and support the idea that these hormones participate in regulating the physiology of this gland.     

Molecular mechanisms of the antihormonal and antiimplantation effects of norethisterone and its a-ring reduced metabolites

Norethisterone (NET) has been used as a contragestational postcoital agent. It is biotrans-formed to 5α dihydro-NET (5α-NET) and 3β,5α tetrahydro-NET (3β,5α-NET) in target tissues. The participation of these metabolites in NET effects is unknown. We have examined the antiimplantation and antiprogestational effects of NET and its metabolites, in adult mated female rabbits, by assessing the number of implantation sites and the expression products of the uteroglobin (UTG) gene in the uterus, and by comparing them with those of RU-486 and estradiol. Steroids were daily administered s.c. at several doses for 7 consecutive days, starting 24 hr after coitus. To assure that fertilization occurred in all animals, the presence of early pregnancy factor was determined. The results demonstrated that high doses (5 mg/kg) of NET reduced both implantation and the expression of the UTG gene. On the other hand, lower doses (1.5 mg/kg) of 5α-NET produced an antiimplantation effect and suppressed UTG synthesis and its mRNA. These effects were similar to those of RU-486. At lower doses (1 mg/kg), both estradiol and the estrogenic metabolite 3β,5α-NET were also effective in inhibiting implantation and UTG gene expression. The overall results suggest that NET metabolites exert antiimplantation and antiprogestational effects through their interaction with progesterone and estrogen receptors, and provide an explanation for the molecular mechanisms involved in the postcoital contraceptive action of NET. © 1995 Wiley-Liss, Inc.