Creatine kinase activity as an indicator of unopposed estrogen action in the mouse uterus associated with anti-progesterone treatment

Estrogen: The necessary evil for human health, and ways to tame it

Estrogen is a pivotal enzyme for survival and health in both genders, though their quantum, tropism, tissue-specific distribution, and receptor affinity varies with different phases of life. Converted from androgen via aromatase enzyme, this hormone is indispensable to glucose homeostasis, immune robustness, bone health, cardiovascular health, fertility, and neural functions. However, estrogen is at the center of almost all human pathologies as well-infectious, autoimmune, metabolic to degenerative. Both hypo and hyper level of estrogen has been linked to chronic and acute diseases. While normal aging is supposed to lower its level, leading to tissue degeneration (bone, muscle, neural etc.), and metabolite imbalance (glucose, lipid etc.), the increment in inflammatory agents in day-to-day life are enhancing the estrogen (or estrogen mimic) level, fueling 'estrogen dominance'. The resultant excess estrogen is inducing an overexpression of estrogen receptors (ERα and ERβ), harming tissues, leading to autoimmune diseases, and neoplasms. The unprecedented escalation in the polycystic ovary syndrome, infertility, breast cancer, ovary cancer, and gynecomastia cases are indicating that this sensitive hormone is getting exacerbated. This critical review is an effort to analyze the dual, and opposing facets of estrogen, via understanding its crosstalk with other hormones, enzymes, metabolites, and drugs. Why estrogen level correction is no trivial task, and how it can be restored to normalcy by a disciplined lifestyle with wise dietary and selective chemical usage choices has been discussed. Overall, our current state of knowledge does not disclose the full picture of estrogen's pleiotropic importance. Hence, this review should be a resource for general public as well as researchers to work in that direction.

Label-free proteomics uncovers energy metabolism and focal adhesion regulations responsive for endometrium receptivity

The menstrual cycle of the female uterus leads to periodic changes of the endometrium. These changes are important for developing the endometrial receptivity and for achieving competency of embryo implantation. However, the molecular events underlying the endometrial receptivity process remain poorly understood. Here we applied an LC-MS-based label-free quantitative proteomic approach to compare the endometrial tissues in the midsecretory (receptive) phase with the endometrial tissues in the proliferative phase from age-matched woman (n = 6/group). The proteomes of endometrial tissues were extracted using an SDS-based detergent, digested by the filter-aided sample preparation procedures, and subsequently analyzed by nano-LC-MS/MS (Orbitrap XL) with a 4 h gradient. Reliable protein expression profiles were reproducibly obtained from the endometrial tissues in the receptive and proliferative phases. A total of 2138 protein groups were quantified under highly stringent criteria with a false discovery rate of <1% for peptide and protein groups. Among these proteins, 317 proteins had differences in expression that were statistically significant between the receptive and proliferative phases. Direct protein-protein interaction network analyses of these significantly changed proteins showed that the up-regulation of creatine kinase B-type (CKB) in the receptive phase may be related to endometrium receptivity. The interaction network also showed that proteins related to cell-cell adhesion were down-regulated. Moreover, the results from KEGG pathway analyses are consistent with the protein-protein interaction results. The proteins, including alpha-actinin (ACTN), extracellular matrix proteins, integrin alpha-V, and so on, that are involved in the focal adhesion pathway were down-regulated in the receptive phase compared with the proliferative phase, which may facilitate the implantation of the fertilized ovum. Selected proteins were validated by Western blot analysis and indirect immunofluorescence, including the up-regulation of CKB and down-regulation ACTN in the receptive phase. In summary, our proteomic analysis study shows potential for predicting the endometrial remodeling from the proliferative to the receptivity phase in women, and these results also reveal the key biological mechanisms (such as energy metabolism and focal adhesion) underlying human endometrial receptivity.

Proteome analysis and genome-wide regulatory motif prediction identify novel potentially sex-hormone regulated proteins in rat efferent ducts

The efferent ducts are a series of tubules that conduct sperm from the rete testis to the epididymis. They absorb most fluid and proteins originating from the rete testis during concentration of spermatozoa prior to their entry into the epididymis. Proteome analysis of micro-dissected efferent duct samples from adult rats was combined with genome-wide computational prediction of conserved hormone response elements to identify factors likely regulated by oestrogens and androgens. We identified 165 proteins and found subsets of the promoters controlling their corresponding genes to contain androgen- and oestrogen response elements (ARE/EREs) at similar frequencies. Moreover, EREs were significantly enriched among the loci identified compared with their genome-wide occurrence. The expression and localization of Anxa6, Ckb, Krt19, Park7, Pdzk1 and Tpt1 in the efferent ducts and other related hormone controlled tissues was further validated at the RNA or protein level. This study identifies many novel proteins predicted to play roles in sperm maturation and male fertility and provides significant computational evidence that the efferent ducts express genes transcriptionally controlled by sex hormones.

RANKL up-regulates brain-type creatine kinase via poly(ADP-ribose) polymerase-1 during osteoclastogenesis

Receptor activator of nuclear factor κB ligand (RANKL) is the key regulator for osteoclast formation and function. During osteoclastogenesis, RANKL-stimulated signals differentially modulate expression of a large number of proteins. Using proteomics approaches, we identified that brain-type cytoplasmic creatine kinase (Ckb) was greatly induced in mature osteoclasts. Ckb has been shown to contribute to osteoclast function. However, the mechanisms of Ckb regulation and the contribution of other isoforms of creatine kinase during RANKL-induced osteoclastogenesis are unknown. We found that Ckb was the predominant isoform of creatine kinase during osteoclastogenesis. Real-time PCR confirmed that RANKL induced ckb mRNA expression by over 40-fold in primary mouse bone marrow macrophages and Raw 264.7 cells. The RANKL-responsive region was identified within the -0.4- to -0.2-kb 5'-flanking region of the ckb gene. Affinity binding purification followed by mass spectrometry analysis revealed that poly(ADP-ribose) polymerase-1 (PARP-1) bound to the -0.4/-0.2-kb fragment that negatively regulated expression of ckb in response to RANKL stimulation. Electrophoretic mobility shift assays with PARP-1-specific antibody located the binding site of PARP-1 to the TTCCCA consensus sequence. The expression of PARP-1 was reduced during RANKL-induced osteoclastogenesis, concurrently with increased expression of Ckb. Consistently, knockdown of PARP-1 by lentivirus-delivered shRNA enhanced ckb mRNA expression. The activity of PARP-1 was determined to be required for its inhibitory effect on the ckb expression. In summary, we have demonstrated that PARP-1 is a negative regulator of the ckb expression. Down-regulation of PARP-1 is responsible for the up-regulation of ckb during RANKL-induced osteoclastogenesis.

Transcriptional activation of rat creatine kinase B by 17beta-estradiol in MCF-7 cells involves an estrogen responsive element and GC-rich sites

The rat creatine kinase B (CKB) gene is induced by estrogen in the uterus, and constructs containing rat CKB gene promoter inserts are highly estrogen-responsive in cell culture. Analysis of the upstream -568 to -523 region of the promoter in HeLa cells has identified an imperfect palindromic estrogen response element (ERE) that is required for hormone inducibility. Analysis of the CKB gene promoter in MCF-7 breast cancer cells confirmed that pCKB7 (containing the -568 to -523 promoter insert) was estrogen-responsive in transient transfection studies. However, mutation and deletion analysis of this region of the promoter showed that two GC-rich sites and the concensus ERE were functional cis-elements that bound estrogen receptor alpha (ERalpha)/Sp1 and ERalpha proteins, respectively. The role of these elements was confirmed in gel mobility shift and chromatin immunoprecipitation assays and transfection studies in MDA-MB-231 and Schneider Drosophila SL-2 cells. These results show that transcriptional activation of CKB by estrogen is dependent, in part, on ERalpha/Sp1 action which is cell context-dependent.

Differential uterine expression of estrogen and progesterone receptors correlates with uterine preparation for implantation and decidualization in the mouse

The present investigation examined the spatiotemporal expression of estrogen receptors (ER-alpha and ER-beta) and progesterone receptor (PR) in the periimplantation mouse uterus (days 1-8). ER-alpha messenger RNA (mRNA) was detected at much higher levels in the periimplantation uterus compared with that of ER-beta mRNA, the levels of which were very low in all uterine cells during this period. Results of in situ hybridization demonstrated expression of ER-alpha mRNA primarily in the luminal and glandular epithelia on days 1 and 2 of pregnancy. On days 3 and 4, the accumulation was localized primarily in stromal cells in addition to its presence in the epithelium. Following implantation on day 5, the accumulation of this mRNA was more condensed in the luminal and glandular epithelia, but declined in the subluminal epithelial stroma at the sites of implanting embryos. On days 6-8, the accumulation of ER-alpha mRNA was primarily localized in the secondary decidual zone (SDZ) with more intense localization in the subepithelial cells at the mesometrial pole. In contrast, signals were very low to undetectable in the primary decidual zone (PDZ), and no signals were detected in implanting embryos. The undifferentiated stroma underneath the myometrium also showed positive signals. The immunolocalization of ER-alpha protein correlated with the mRNA localization. Western blot analysis showed down-regulation of ER-alpha in day 8 decidual cell extracts consistent with the down-regulation of ER-alpha mRNA in decidual cells immediately surrounding the embryo on this day. The expression pattern of PR was also dynamic in the periimplantation uterus. On day 1, the accumulation of PR mRNA was very low to undetectable, whereas only a modest level of accumulation in the epithelium was noted on day 2. On days 3 and 4, the accumulation of this mRNA was detected in both the epithelium and stroma. In contrast, the expression was restricted only to the stroma with increased signals at the sites of implantation on day 5. On days 6-8, PR mRNA accumulation increased dramatically throughout the deciduum. The localization of immunoreactive PR correlated with the mRNA distribution in the periimplantation uterus. Taken together, the results demonstrate that the expression of ER-alpha, ER-beta, and PR is differentially regulated in the periimplantation mouse uterus. This compartmentalized expression of ER and PR provides information regarding the sites of coordinated effects ofestrogen and progesterone in the preparation of the uterus for implantation and decidualization during early pregnancy.

Uterine decidual response occurs in estrogen receptor-alpha-deficient mice

Embryo-uterine interactions leading to the attachment reaction is followed by stromal cell proliferation and differentiation into decidual cells (decidualization) at the sites of blastocyst apposition. In rodents, decidualization is also induced by application of an artificial stimulus (intraluminal oil infusion) in a pseudopregnant uterus, or to one that has been appropriately prepared by exogenous progesterone (P4) and estrogen. The process of decidualization is under the control of these steroids in the presence of blastocysts or deciduogenic stimuli. Although it is well known that estrogen is required for the induction of progesterone receptors in the uterus, the functional importance of estrogen in the process of decidualization is poorly understood. To better understand the role of estrogenic actions in decidualization, we used wild-type and estrogen receptor-alpha knock-out (ERKO) mice for induction of decidualization employing a defined steroid hormonal treatment schedule. Our results demonstrate that P4 alone induces decidualization in ovariectomized wild-type or ERKO mice in response to intraluminal oil infusion in the absence of estrogen. A combined treatment of either estradiol-17beta (E2) or its catecholmetabolite 4-hydroxyestradiol-17beta(4-OH-E2) with P4 does not potentiate the decidual response produced by P4 treatment alone in either ovariectomized wild-type or ERKO mice. The induction of decidual response was associated with up-regulation of decidual cell marker genes, such as progesterone receptor, metallothionein-1, and cyclooxygenase-2. The results suggest that the stromal cell sensitivity to decidualization is critically dependent on P4-regulated events, and estrogenic induction of progesterone receptor via classical nuclear ER-alpha is not critical for this process.