Placental claudin expression and its regulation by endogenous sex steroid hormones

Quantitative trait loci exploration and characterization of gestation length in Holstein cattle

Gestation length (GL) is a moderately heritable trait in cattle with economic and management implications. This study aimed to characterize the gestation length of an Argentinian Holstein cattle population, understand contributing factors, and explore the GL effect on production performance. Further objectives were to estimate direct and maternal heritabilities for this trait and to identify genomic regions affecting it. Data consisted of GL records from 45,738 births corresponding to 17,004 Holstein cows and heifers. The effects of age and calving season over GL were analyzed using a Student's t-test for homoscedastic samples. The effects of the GL category (GL shorter than 1.5 SD, within ±1.5 SD, and longer than 1.5 SD from the mean) on production performance were studied by analysis of variance. A single-step genome-wide association study was performed using the BLUPF90 suite of programs with genotypes from 654 Holstein animals on 40,339 SNP. The results showed that the younger the age at calving, the shorter the GL. Moreover, gestations ending in warmer seasons were, in general, statistically shorter than those ending in colder seasons for both heifers and cows. Regarding the effect of GL on production performance, cows with gestation periods within ±1.5 SD from the population mean exhibited the highest 305-day cumulative milk, fat, and protein productions. Direct and maternal heritabilities for GL were 0.42 and 0.03, respectively. We detected a SNP suggestively associated with direct gestation length at 57.7 Mb on Bos taurus autosome 18, a locus included in a region described in the literature as associated with the trait. The information obtained on the environmental and genetic factors affecting GL in Argentinian Holstein cows contributes to characterizing the population in pursuit of improving the performance of national dairy cattle breeding systems.

Claudin-23 reshapes epithelial tight junction architecture to regulate barrier function

Claudin family tight junction proteins form charge- and size-selective paracellular channels that regulate epithelial barrier function. In the gastrointestinal tract, barrier heterogeneity is attributed to differential claudin expression. Here, we show that claudin-23 (CLDN23) is enriched in luminal intestinal epithelial cells where it strengthens the epithelial barrier. Complementary approaches reveal that CLDN23 regulates paracellular ion and macromolecule permeability by associating with CLDN3 and CLDN4 and regulating their distribution in tight junctions. Computational modeling suggests that CLDN23 forms heteromeric and heterotypic complexes with CLDN3 and CLDN4 that have unique pore architecture and overall net charge. These computational simulation analyses further suggest that pore properties are interaction-dependent, since differently organized complexes with the same claudin stoichiometry form pores with unique architecture. Our findings provide insight into tight junction organization and propose a model whereby different claudins combine to form multiple distinct complexes that modify epithelial barrier function by altering tight junction structure.

Angiotensin-(1-7) ameliorates intestinal barrier dysfunction by activating the Keap1/Nrf2/HO-1 signaling pathway in acute pancreatitis

BACKGROUND

Intestinal barrier dysfunction is a serious complication associated with acute pancreatitis (AP). Angiotensin (Ang)-(1-7) plays a protective role in the intestinal barrier, but the underlying mechanism remains clear. This study investigated the impact of Ang-(1-7) on AP-induced intestinal dysfunction and its involvement in the Keap1/Nrf2/HO-1 pathway.

METHODS AND RESULTS

We studied caerulein- and lipopolysaccharide (LPS)-induced AP in mice and an epithelial cell line (IEC-6) from the small intestinal crypt of rats. Ang-(1-7) was administered orally or via the tail vein. IEC-6 cells were divided into five groups: control; LPS; LPS + Ang-(1-7); LPS + Ang-(1-7) + ML385 (an Nrf2 inhibitor); and LPS + ML385. Pancreatic and intestinal histopathology scores were analyzed using the Schmidt and Chiu scores. The expression of intestinal barrier-associated proteins and Keap1/Nrf2/HO-1 pathway constituents was assessed by RT-PCR and western blotting. The peroxide and antioxidant activities in the IEC-6 cells were measured. Compared to those in AP mice, Ang-(1-7) diminished the intestinal levels of proinflammatory factors (interleukin-1β and tumor necrosis factor α) and serum levels of intestine permeability (D-lactate). Ang-(1-7) increased the expression of barrier-associated proteins (aquaporin-1, claudin-1, and occludin) compared to those in the AP and LPS group. Moreover, Ang-(1-7) promoted the Keap/Nrf2/HO-1 pathway, which resulted in significantly reduced malondialdehyde and increased superoxide dismutase levels.. However, ML385 abolished the effects of Ang-(1-7) on barrier-associated proteins and reversed the Keap1/Nrf2/HO-1 pathway.

CONCLUSIONS

Ang-(1-7) reduces AP-induced intestinal inflammation and oxidative injuries by activating the Keap1/Nrf2/HO-1 pathway.

Autophagy was activated against the damages of placentas caused by nano-copper oral exposure

Nano-copper (nano-Cu) is widely used in the pharmaceutical field as well as a feed additive for animals owing to its unique physicochemical characteristics and bioactivities. In our previous study, nano-Cu was found to hamper fetal development; however, the toxicity of nano-Cu and its effects in placental function have not been elucidated. Therefore, we investigated the toxic effects of nano-Cu using rat placenta. Pregnant Sprague-Dawley rats were orally exposed to different copper sources from the third day of gestation (GD 3) to GD 18. We found that nano-Cu (180 mg/kg) and CuCl₂.2 H₂O increased the accumulation of copper. Besides, nano-Cu and CuCl₂.2 H₂O disrupted the placental morphology and induced oxidative stress. Micro-copper (micro-Cu) caused similar toxicity in the placenta, but its effects were weaker than that of nano-Cu and CuCl₂.2 H₂O. In addition, exposure to nano-Cu (180 mg/kg) and CuCl₂.2 H₂O induced inflammation in the rat placenta. Furthermore, nano-Cu, micro-Cu, and CuCl₂.2 H₂O upregulated the expression of the autophagy-related proteins, Beclin-1 and LC3 II/ LC3 I, and downregulated that of p62. Moreover, nano-Cu, micro-Cu, and CuCl₂.2 H₂O downregulated the protein expression of PI3K, p-AKT/AKT, and p-mTOR/mTOR in rat placentas, whereas the protein expression of p-AMPK/AMPK was upregulated. Taken together, our data indicated that prenatal exposure to nano-Cu induced autophagy via the PI3K/AKT/mTOR and AMPK/mTOR pathways, which associated with oxidative stress and inflammation in rat placenta.

Inflammation-related downregulation of zonula Occludens-1 in fetal membrane contributes to development of prelabor rupture of membranes

INTRODUCTION

The aim of this research was to study the alteration of three key tight junction proteins, to explore whether they were involved in the occurrence of prelabor rupture of the membrane (PROM) and to determine the correlation with intrauterine infection.

METHODS

A total of 208 women were enrolled between January 2015 to December 2018, including those with preterm and term PROM (PROM group) and normal pregnancies with intact fetal membrane (control group). We investigated the expressions of three key TJ molecules (Zonula occludens-1, Occludin and Claudin-5) in fetal membranes. The localization and expression of Zonula occludens-1 (ZO-1) in the amnion and chorion were studied by immunohistochemistry assay. The associations between ZO-1 expression levels and extent of inflammatory reactions as well as other obstetric characteristics were further studied using Spearman's rank correlation test and Mann-Whitney U test.

RESULTS

ZO-1 was significantly downregulated in PROM group compared with control group (P < 0.001), whereas no significant changes were found for Occludin and Claudin-5. ZO-1 expression was reduced in the chorion and amnion layers in PROM group compared with that in control group, which showed a significant difference (P < 0.01), but no significant differences were observed between the preterm PROM and term PROM groups (P > 0.05). The expression levels of ZO-1 in the chorion were negatively correlated with the stage/grade of acute chorioamnionitis (P < 0.05).

DISCUSSION

Our study suggests that inflammation-related downregulation of ZO-1 might be a pivotal event in the occurrence of PROM, which helps to clarify the mechanism of membrane rupture caused by infection.

Claudins: New Players in Human Fertility and Reproductive System Cancers

Claudins are major integral proteins of tight junctions (TJs), the apical cell-cell adhesions that enable maintaining polarity of epithelial cells, their differentiation, and cell signaling. A number of studies have indicated that claudins might play a crucial role in both physiology and pathogenesis. Their tissue-specific expression was originally linked to the development of different types of cancer and triggered a hope to use them as diagnostic or prognostic markers. However, it seems that their expression is more complex than that, and undoubtedly, claudins participate in one of the most important molecular events in cells. This review summarizes the recent research evaluating the role of claudins in fertility and the most common endocrine-dependent cancers in the reproductive system and highlights the crucial role of claudins both in human fertility and the most common cancers.

Abundances and localizations of Claudin-1 and Claudin-5 in the domestic cat (Felis catus) ovary during the estrous cycle

Claudins (CLDNs) are major Ca²⁺-independent cell adhesion molecules functioning at tight junctions (TJ). The presence and localization of cell adhesion molecules are important for understanding the mechanisms associated with follicular and luteal development in the ovary. In this study, there was an examination of whether CLDN-1 and CLDN-5 are present in a cell- and stage-specific manner during follicular and luteal development in the domestic cat ovary using immunohistochemistry and Western blot analysis. While results from immunoblot analyses revealed there were relatively similar abundances of CLDN-5 protein in three phases of the ovarian cycle, the abundance of CLDN-1 in the luteal phase was greater than those measured in the follicular and anestrous phases (P < 0.01). Results with immunohistochemistry indicate CLDN-1 and -5 are mainly localized in the cell nuclei and cytoplasm of all tissues of the cat ovary. In follicles, throughout the development from primordial to large antral follicles, CLDN-1 and -5 were present in oocytes, and the granulosa and theca cell layers. In follicles at all stages of atresia, there were cell-type and stage-specific protein distributions with immunostaining present in granulosa, thecal interstitial, and fibroblast-like cells. In corpora lutea, both small and large luteal cells stained positively for both claudins. In conclusion, the specific presence and localization patterns of CLDN-1 and -5 in the cat ovary is suggestive that these TJ proteins could have local functions in the regulation of most ovarian functions such as follicle development and atresia, ovulation, and corpus luteum formation and regression.

Fusarium Mycotoxins Disrupt the Barrier and Induce IL-6 Release in a Human Placental Epithelium Cell Line

Deoxynivalenol, T-2 toxin, and zearalenone, major Fusarium mycotoxins, contaminate human food on a global level. Exposure to these mycotoxins during pregnancy can lead to abnormalities in neonatal development. Therefore, the aim of this study was to investigate the effects of Fusarium mycotoxins on human placental epithelial cells. As an in vitro model of placental barrier, BeWo cells were exposed to different concentrations of deoxynivalenol, zearalenone or T-2 toxin. Cytotoxicity, effects on barrier integrity, paracellular permeability along with mRNA and protein expression and localization of junctional proteins after exposure were evaluated. Induction of proinflammatory responses was determined by measuring cytokine production. Increasing mycotoxin concentrations affect BeWo cell viability, and T-2 toxin was more toxic compared to other mycotoxins. Deoxynivalenol and T-2 toxin caused significant barrier disruption, altered protein and mRNA expression of junctional proteins, and induced irregular cellular distribution. Although the effects of zearalenone on barrier integrity were less prominent, all tested mycotoxins were able to induce inflammation as measured by IL-6 release. Overall, Fusarium mycotoxins disrupt the barrier of BeWo cells by altering the expression and structure of junctional proteins and trigger proinflammatory responses. These changes in placental barrier may disturb the maternal–fetal interaction and adversely affect fetal development.

Syncytiotrophoblast of Placentae from Women with Zika Virus Infection Has Altered Tight Junction Protein Expression and Increased Paracellular Permeability

The cytotrophoblast of human placenta transitions into an outer multinucleated syncytiotrophoblast (STB) layer that covers chorionic villi which are in contact with maternal blood in the intervillous space. During pregnancy, the Zika virus (ZIKV) poses a serious prenatal threat. STB cells are resistant to ZIKV infections, yet placental cells within the mesenchyme of chorionic villi are targets of ZIKV infection. We seek to determine whether ZIKV can open the paracellular pathway of STB cells. This route is regulated by tight junctions (TJs) which are present in the uppermost portion of the lateral membranes of STB cells. We analyzed the paracellular permeability and expression of E-cadherin, occludin, JAMs -B and -C, claudins -1, -3, -4, -5 and -7, and ZO-1, and ZO-2 in the STB of placentae from ZIKV-infected and non-infected women. In ZIKV-infected placentae, the pattern of expression of TJ proteins was preserved, but the amount of claudin-4 diminished. Placentae from ZIKV-infected women were permeable to ruthenium red, and had chorionic villi with a higher mean diameter and Hofbauer hyperplasia. Finally, ZIKV added to the basolateral surface of a trophoblast cell line reduced the transepithelial electrical resistance. These results suggest that ZIKV can open the paracellular pathway of STB cells.

The genome of the live-bearing fish Heterandria formosa implicates a role of conserved vertebrate genes in the evolution of placental fish

Background

The evolution of complex organs is thought to occur via a stepwise process, each subsequent step increasing the organ’s complexity by a tiny amount. This evolutionary process can be studied by comparing closely related species that vary in the presence or absence of their organs. This is the case for the placenta in the live-bearing fish family Poeciliidae, as members of this family vary markedly in their ability to supply nutrients to their offspring via a placenta. Here, we investigate the genomic basis underlying this phenotypic variation in Heterandria formosa, a poeciliid fish with a highly complex placenta. We compare this genome to three published reference genomes of non-placental poeciliid fish to gain insight in which genes may have played a role in the evolution of the placenta in the Poeciliidae.

Results

We sequenced the genome of H. formosa, providing the first whole genome sequence for a placental poeciliid. We looked for signatures of adaptive evolution by comparing its gene sequences to those of three non-placental live-bearing relatives. Using comparative evolutionary analyses, we found 17 genes that were positively selected exclusively in H. formosa, as well as five gene duplications exclusive to H. formosa. Eight of the genes evolving under positive selection in H. formosa have a placental function in mammals, most notably endometrial tissue remodelling or endometrial cell proliferation.

Conclusions

Our results show that a substantial portion of positively selected genes have a function that correlates well with the morphological changes that form the placenta of H. formosa, compared to the corresponding tissue in non-placental poeciliids. These functions are mainly endometrial tissue remodelling and endometrial cell proliferation. Therefore, we hypothesize that natural selection acting on genes involved in these functions plays a key role in the evolution of the placenta in H. formosa.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1484-2) contains supplementary material, which is available to authorized users.

Polygenic and sex specific architecture for two maturation traits in farmed Atlantic salmon

BACKGROUND

A key developmental transformation in the life of all vertebrates is the transition to sexual maturity, whereby individuals are capable of reproducing for the first time. In the farming of Atlantic salmon, early maturation prior to harvest size has serious negative production impacts.

RESULTS

We report genome wide association studies (GWAS) using fish measured for sexual maturation in freshwater or the marine environment. Genotypic data from a custom 50 K single nucleotide polymorphism (SNP) array was used to identify 13 significantly associated SNP for freshwater maturation with the most strongly associated on chromosomes 10 and 11. A higher number of associations (48) were detected for marine maturation, and the two peak loci were found to be the same for both traits. The number and broad distribution of GWAS hits confirmed a highly polygenetic nature, and GWAS performed separately within males and females revealed sex specific genetic behaviour for loci co-located with positional candidate genes phosphatidylinositol-binding clathrin assembly protein-like (picalm) and membrane-associated guanylate kinase, WW and PDZ domain-containing protein 2 (magi2).

CONCLUSIONS

The results extend earlier work and have implications for future applied breeding strategies to delay maturation in this important aquaculture species.

Bicellular Tight Junctions and Wound Healing

Bicellular tight junctions (TJs) are intercellular junctions comprised of a variety of transmembrane proteins including occludin, claudins, and junctional adhesion molecules (JAMs) as well as intracellular scaffold proteins such as zonula occludens (ZOs). TJs are functional, intercellular structures that form a barrier between adjacent cells, which constantly seals and unseals to control the paracellular passage of molecules. They are primarily present in the epithelial and endothelial cells of all tissues and organs. In addition to their well-recognized roles in maintaining cell polarity and barrier functions, TJs are important regulators of signal transduction, which modulates cell proliferation, migration, and differentiation, as well as some components of the immune response and homeostasis. A vast breadth of research data is available on TJs, but little has been done to decipher their specific roles in wound healing, despite their primary distribution in epithelial and endothelial cells, which are essential contributors to the wound healing process. Some data exists to indicate that a better understanding of the functions and significance of TJs in healing wounds may prove crucial for future improvements in wound healing research and therapy. Specifically, recent studies demonstrate that occludin and claudin-1, which are two TJ component proteins, are present in migrating epithelial cells at the wound edge but are absent in chronic wounds. This indicates that functional TJs may be critical for effective wound healing. A tremendous amount of work is needed to investigate their roles in barrier function, re-epithelialization, angiogenesis, scar formation, and in the interactions between epithelial cells, endothelial cells, and immune cells both in the acute wound healing process and in non-healing wounds. A more thorough understanding of TJs in wound healing may shed new light on potential research targets and reveal novel strategies to enhance tissue regeneration and improve wound repair.

Drug Transport at the Brain and Endothelial Dysfunction in Preeclampsia: Implications and Perspectives

Transport of drugs across biological barriers has been a subject of study for decades. The discovery and characterization of proteins that confer the barrier properties of endothelia and epithelia, including tight junction proteins and membrane transporters belonging to the ATP-binding cassette (ABC) and Solute Carrier (SLC) families, represented a significant step forward into understanding the mechanisms that govern drug disposition. Subsequently, numerous studies, including both pre-clinical approaches and clinical investigations, have been carried out to determine the influence of physiological and pathological states on drug disposition. Importantly, there has been increasing interest in gaining a better understanding of drug disposition during pregnancy, since epidemiological and clinical studies have demonstrated that the use of medications by pregnant women is significant and this condition embodies a series of significant anatomical and physiological modifications, particularly at excretory organs and barrier sites (e.g., placenta, breast) expressing transporter proteins which influence pharmacokinetics. Currently, most of the research in this field has focused on the expression profiling of transporter proteins in trophoblasts and endothelial cells of the placenta, regulation of drug-resistance mechanisms in disease states and pharmacokinetic studies. However, little attention has been placed on the influence that the cerebrovascular dysfunction present in pregnancy-related disorders, such as preeclampsia, might exert on drug disposition in the mother’s brain. This issue is particularly important since recent findings have demonstrated that preeclamptic women suffer from long-term alterations in the integrity of the blood-brain barrier (BBB). In this review we aim to analyze the available evidence regarding the influence of pregnancy on the expression of transporters and TJ proteins in brain endothelial cells, as well the mechanisms that govern the pathophysiological alterations in the BBB of women who experience preeclampsia. Future research efforts should be focused not only on achieving a better understanding of the influence of preeclampsia-associated endothelial dysfunction on drug disposition, but also in optimizing the pharmacological treatments of women suffering pregnancy-related disorders, its comorbidities and to develop new therapies aiming to restore the integrity of the BBB.

Hypoxia-induced and HIF1α-VEGF-mediated tight junction dysfunction in choriocarcinoma cells: Implications for preeclampsia

INTRODUCTION

Accumulated data indicate that placental hypoxia is implicated in the pathogenesis of preeclampsia (PE). Tight junction (TJ) is important structure that sustains normal placental barrier function, its dysregulation under hypoxia has been observed. This study was designed to explore hypoxia-induced TJ dysfunction in trophoblast cells and its possible involvement in PE pathophysiology.

METHODS

Choriocarcinoma cells were grown in a monolayer and treated with cobalt chloride (CoCl₂) to induce hypoxia. TJ architecture was assessed using transmission electron microscopy, and locations of TJ proteins were determined by immunofluorescence. TJ functions were assessed by transepithelial electrical resistance (TER) and increased cell paracellular permeability (CPP), and the expression of TJ-related proteins, HIF-1α and VEGF was measured.

RESULTS

The TJ functions of trophoblast cells were significantly altered by hypoxia; TER decreased and CPP increased in a time- and concentration-dependent manner. Significant alterations in TJ protein expression and increases in HIF1α and VEGF expression were observed in hypoxic cells, and these effects were attenuated by pretreatment with YC-1. Moreover, corresponding changes in TJ protein expression were also detected in preeclamptic placentas.

CONCLUSION

These data demonstrate that trophoblast cells undergo significant changes in TJ protein expression under hypoxic conditions and highlight the potential significance of the HIF1α-VEGF axis in the regulation of TJ structure and function in the preeclamptic placenta.

Effects of Octylphenol and Bisphenol A on the Metal Cation Transporter Channels of Mouse Placentas

Octylphenol (OP) and bisphenol A (BPA) are known as endocrine-disrupting chemicals (EDCs). During pregnancy, the expression of steroid hormone receptors is controlled by maternal and fetal nutrition. To evaluate the impact of EDCs during pregnancy, ethinyl estradiol (EE, 0.2 mg/kg/day), OP (50 mg/kg/day), and BPA (50 mg/kg/day) were administered to pregnant mice. The mRNA levels of TRPV6 (transient receptor potential cation channels in subfamily V, member 6) decreased significantly by EE and OP. The PMCA1 (ATPase, Ca⁺⁺ transporting, plasma membrane 1) mRNA and protein levels decreased significantly by EE, OP, and BPA. CTR1 (solute carrier family 31, member 1) and ATP7A (ATPase, Cu⁺⁺ transporting, alpha polypeptide) expression decreased significantly by EE, OP, and BPA. The mRNA levels of IREG1 (iron-regulated transporter, member 1) decreased significantly by EE. Hephaestin (HEPH) mRNA levels decreased significantly by EE, OP, and BPA, and protein levels decreased significantly by BPA. As a result of immunohistochemistry analysis, all cation transporter proteins were found in labyrinth of placenta. To confirm the cytosolic level of cations, levels of cation level in fetal serum were measured. EE, OP, and BPA significantly reduced serum calcium and copper levels, and iron levels were reduced by BPA. Taken together, some EDCs, such as OP and BPA, could modulate the calcium, copper, and iron ion-transporting channels during pregnancy. The fetus relies on the mother for ionic transportation, and, therefore, pregnant women should avoid exposure to cation-channel-disrupting chemicals.

Tight junction between endothelial cells: the interaction between nanoparticles and blood vessels

Since nanoparticles are now widely applied as food additives, in cosmetics and other industries, especially in medical therapy and diagnosis, we ask here whether nanoparticles can cause several adverse effects to human health. In this review, based on research on nanotoxicity, we mainly discuss the negative influence of nanoparticles on blood vessels in several aspects and the potential mechanism for nanoparticles to penetrate endothelial layers of blood vessels, which are the sites of phosphorylation of tight junction proteins (claudins, occludins, and ZO (Zonula occludens)) proteins, oxidative stress and shear stress. We propose a connection between the presence of nanoparticles and the regulation of the tight junction, which might be the key approach for nanoparticles to penetrate endothelial layers and then have an impact on other tissues and organs.