CXCL14 inhibits trophoblast outgrowth via a paracrine/autocrine manner during early pregnancy in mice

CXCL14, a member of chemokine family, was previously known to participate in many pathophysiological events, such as leukocytes recruitment and tumor suppression. However, it remained largely unknown whether CXCL14 is a physiological player during early pregnancy. In this regard, our recent global gene microarray analysis has observed an implantation-specific expression profile of CXCL14 mRNA during early pregnancy in mice, showing its higher levels at implantation sites compared to inter-implantation sites, implicating a potential role of CXCL14 in the periimplantation events. In the present investigation, using Northern blot, in situ hybridization and immunostaining, we further demonstrated that uterine CXCL14 expression was specifically induced at embryo implantation site and expanded with subsequent decidualization process in a spatiotemporal manner. The implanting embryo also showed a highlighted expression of CXCL14 in the blastocyst trophectoderm and its derived ectoplacental cones (EPCs) during postimplantation development. In vitro functional study revealed that CXCL14 could significantly inhibit both primary and secondary trophoblast attachment and outgrowth, correlated with a stage-dependant downregulation of MMP-2 and/or MMP-9 activity. Moreover, it was found that biotinylated CXCL14 could specifically bind to trophoblast cells in vitro and in vivo, suggesting trophoblast cell, perhaps expressing the unidentified CXCL14 receptor, is a bioactive target of CXCL14. Collectively, our findings provide evidences supporting the contention that CXCL14 is an important paracrine/autocrine modulator regulating trophoblast outgrowth at the maternal-fetal interface during the process of pregnancy establishment. This study is clinically related since CXCL14 is also highly expressed in human receptive endometrium and trophoblasts.

Premature ovarian failure, menopause and ovarian cancer, three nodes on the same string: Pten and other potential genes on the go

BACKGROUND

Why do women have menopause? The evolution of menopause has long been the puzzle and interest of sociologists regarding Darwinian fitness. However, in a biological/medical perspective, the underling drive force of menopause has never been provided in a satisfactory form.

HYPOTHESIS AND RATIONALE

It has been well established that the overall reproductive lifespan is reflected in the speed of ovarian primordial follicles depletion. And, every ovarian cycle involves disruption and regeneration of the ovarian epithelium, which is potentially mutagenic. In this regard, menopause could be evolved to protect reproductive organs from over-disruption-reconstruction cycling, as to preclude mutagenic tissue changes. Recent discoveries by tissue/cell specific deletion of one single gene (Pten) within different compartment of ovary have revealed strikingly distinct ovarian phenotypes, ranging from advanced primordial follicle depletion to neoplastic ovarian lesions. To explain the onset of menopause, here we propose a model that the relative amount/activity of Pten between different ovarian compartments (follicular, granulosa and epithelial cells) is spatiotemporally programmed, creating a "menopause tone" fine tuning the speed of follicle depletion and therefore the normal timing of menopause. While imbalanced expression of Pten within the ovary cause either pre-arrived menopause (premature ovarian failure) or over-menstrual cycles which are well recognized as a risk factor for ovarian (and other reproductive) cancer. This hypothesis, if validated, could help us understand ovarian aging and related diseases in a more integrated manner; they are just different nodes on the same string. And Pten could just be the tip of the iceberg involved in the regulation of "menopause tone".

Development of an enzyme-linked immunosorbent assay for the alpha-cyano pyrethroids multiresidue in Tai lake water

A general and broad class selective competitive enzyme-linked immunosorbent assay (ELISA) for the detection of the alpha-cyano pyrethroids was developed. One class specific hapten, the 5-(3-benzylphenyl)-5-cyanopentanoic acid (CPBA-BE), was conjugated with BSA as an immunogen. Polyclonal antibodies, PY-antibodies, were generated. The assay with the most selectivity for the family alpha-cyano pyrethroids such as cyphenothrin was further optimized and tested for tolerance to cosolvent, pH, and ionic strength changes. The IC(50) values of the optimized immunoassay were 4.58 microg L(-1) for cyphenothrin, 5.62 microg L(-1) for fenpropathrin, 7.08 microg L(-1) for deltamethrin, 10.72 microg L(-1) for cypermethrin, 19.95 microg L(-1) for flucythrinate, and 28.18 microg L(-1) for esfenvalerate. The cross-reactivities of cyphenothrin, fenpropathrin, deltamethrin, cypermethrin, flucythrinate, and esfenvalerate were 100%, 81.49%, 64.68%, 42.72%, 22.96%, and 16.25%, respectively. The low detection limit (LDL) of this assay was 0.107 microg L(-1) for cyphenothrin. This method was used for the detection of the alpha-cyano pyrethroids in Tai lake water.

Expression and regulation of Dickkopf2 during periimplantation in mice

Successful implantation depends on active dialogue between the maternal endometrium and the implanting blastocysts that is well controlled by groups of regulators at the molecular level. Dickkopf2 (Dkk2) is a member of Dickkopf family normally acting as an antagonist of canonical Wnt/beta-catenin signaling, which has been proven to participate in tumorigenesis and early embryo development. In order to explore the potential function of Dkk2 in embryo implantation, the present study investigated the uterine expression and regulation profiles of Dkk2 during periimplantation in mice. Using reverse transcription-polymerase chain reaction, immunohistochemistry and Western blotting, we showed that the mRNA and protein levels of Dkk2 began to increase in the glandular epithelium on day 4, continued to increase on day 5 and then decreased from day 6 of pregnancy. Moreover, on days 5-8 of pregnancy, Dkk2 was increasingly expressed in the deciduum of the uterus, especially around the implanting embryos. In addition, upregulation of Dkk2 was also observed in uteri treated with estrogen (estradiol-17beta) as well as in oil-induced artificial decidualization, indicating that the expression of Dkk2 could be induced by both steroid hormone (estrogen) and the process of decidualization. Furthermore, in the postimplantation uterus, the Dkk2 protein showed an inversed expression with active beta-catenin from day 6 onward, supporting the notion that Dkk2 plays an inhibitory role against canonical Wnt signaling in the context of the decidualizing stroma. Collectively, our data suggests that Dkk2 expression is associated with uterine receptivity changes as well as the process of decidualization and that it might play important roles through inhibition of canonical Wnt signaling in the periimplantation uterus.

Synthesis of a cationic pyridoxamine conjugation reagent and application to the mechanistic analysis of an artificial transaminase

An N-methylated, cationic pyridoxamine conjugation reagent was synthesized and tethered via a disulfide bond to a cysteine residue inside the cavity of intestinal fatty acid binding protein. The conjugate was characterized and the kinetic parameters compared to its nonmethylated pyridoxamine analogue. Kinetic isotope effects were used for further mechanistic analysis. Taken together, these experiments suggest that a step distinct from deprotonation of the ketimine in the pyridoxamine to pyridoxal reaction is what limits the rate of the artificial transaminase IFABP-Px. However, the internal energetics of reactions catalyzed by the conjugate containing the N-methylated cofactor appear to be different suggesting that the MPx reagent will be useful in future experiments designed to alter the catalytic properties of semisynthetic transaminases.

Artificial metalloenzymes based on protein cavities: exploring the effect of altering the metal ligand attachment position by site directed mutagenesis

In an effort to construct catalysts with enzyme-like properties, we are employing a small, cavity-containing protein as a scaffold for the attachment of catalytic groups. In earlier work we demonstrated that a phenanthroline ligand could be introduced into the cavity of the protein ALBP and used to catalyze ester hydrolysis. To examine the effect of positioning the phenanthroline catalyst at different locations within the protein cavity, three new constructs--Phen60, Phen72 and Phen104--were prepared. Each new conjugate was characterized by UV/vis spectroscopy, fluorescence spectroscopy, guanidine hydrochloride denaturation, gel filtration chromatography, and CD spectroscopy to confirm the preparation of the desired construct. Analysis of reactions containing Ala-OiPr showed that Phen60 catalyzed ester hydrolysis with less selectivity than ALBP-Phen while Phen72 promoted this same reaction with higher selectivity. Reactions with Tyr-OMe were catalyzed with higher selectivity by Phen60 and more rapidly by Phen104. These results demonstrate that both the rates and selectivities of hydrolysis reactions catalyzed by these constructs are dependent on the precise site of attachment of the metal ligand within the protein cavity.

The design of protein-based catalysts using semisynthetic methods

The combination of site-directed mutagenesis and chemical modification has resulted in the preparation of protein conjugates with new and useful properties. Proteins modified with metal-chelating groups are proving useful for mapping tertiary and quaternary interactions using the technique of affinity cleavage. The attachment of cofactors, including pyridoxal and pyridoxamine, has resulted in the preparation of semisynthetic transaminases that display enzyme-like properties, including enantioselectivity, substrate specificity and reaction-rate acceleration.

Effects of metal ions on the rates and enantioselectivities of reactions catalyzed by a series of semisynthetic transaminases created by site directed mutagenesis

Fatty acid binding proteins are a class of small 15 kDa proteins with a simple architecture that forms a large solvent sequestered cavity. In previous work, we demonstrated that reductive amination reactions could be performed in this cavity by covalent attachment of a pyridoxamine cofactor and that the rate, enantioselectivity and substrate specificity of these reactions could be altered by site directed mutagenesis. Herein, we show that the chemistry performed by these conjugates can be extended to include catalytic transamination and describe the effects of added metal ions on reaction rate and enantioselectivity. We conclude that metal ions can be used to increase the rate of reactions catalyzed by semisynthetic transaminases; however, the addition of metal ions can also retard the reaction rate. Furthermore, it appears that the presence of metal ions almost always results in an erosion of reaction enantioselectivity. This limits their utility as a practical means of increasing reaction rate. The results reported here, for four independent systems, should be considered in future designs of artificial transaminases.

Structural characterization of two synthetic catalysts based on adipocyte lipid-binding protein

Adipocyte lipid-binding protein (ALBP) is a small (14.5 kDa) 10-stranded beta-barrel protein found in mammalian fat cells. The crystal structures of various holo-forms of ALBP have been solved and show the fatty acid ligand bound in a large (approximately 400 A3) cavity isolated from bulk solvent. Examination of the cavity suggests that it would be a good site for the creation of an artificial catalyst, as numerous well defined crystal structures of ALBP are available and past studies have shown the conformation to be reasonably tolerant to modification and mutagenesis. Previous work has shown ALBP to be a good protein scaffold for exploring enantio- and stereoselective reactions; two constructs, ALBP attached to either a pyridoxamine or a phenanthroline group at C117, have been chemically characterized. Both modified proteins have been crystallized and their structures solved and refined. The X-ray models have been used to examine the origin of the chiral selectivity seen in the products. It is apparent that these covalent adducts reduce the internal cavity volume, sterically limiting substrate interactions with the reactive groups, as well as solvent access to potential intermediates in the reaction pathway.