The role of retinoic acid in embryonic and post-embryonic development

Keratin 8/18a.1 Expression Influences Embryonic Neural Crest Cell Dynamics and Contributes to Postnatal Corneal Regeneration in Zebrafish

A complete understanding of neural crest cell mechanodynamics during ocular development will provide insight into postnatal neural crest cell contributions to ophthalmic abnormalities in adult tissues and inform regenerative strategies toward injury repair. Herein, single-cell RNA sequencing in zebrafish during early eye development revealed keratin intermediate filament genes krt8 and krt18a.1 as additional factors expressed during anterior segment development. In situ hybridization and immunofluorescence microscopy confirmed krt8 and krt18a.1 expression in the early neural plate border and migrating cranial neural crest cells. Morpholino oligonucleotide (MO)-mediated knockdown of K8 and K18a.1 markedly disrupted the migration of neural crest cell subpopulations and decreased neural crest cell marker gene expression in the craniofacial region and eye at 48 h postfertilization (hpf), resulting in severe phenotypic defects reminiscent of neurocristopathies. Interestingly, the expression of K18a.1, but not K8, is regulated by retinoic acid (RA) during early-stage development. Further, both keratin proteins were detected during postnatal corneal regeneration in adult zebrafish. Altogether, we demonstrated that both K8 and K18a.1 contribute to the early development and postnatal repair of neural crest cell-derived ocular tissues.

Urine Excretion, Organ Distribution, and Placental Transfer of 6PPD and 6PPD-Quinone in Mice and Potential Developmental Toxicity through Nuclear Receptor Pathways

The rubber antioxidant 6PPD has gained significant attention due to its highly toxic transformation product, 6PPD-quinone (6PPDQ). Despite their detection in urines of pregnant women, the placental transfer and developmental toxicity of 6PPD and 6PPDQ are unknown. Here, we treated C57Bl/6 mice with 4 mg/kg 6PPD or 6PPDQ to investigate their urine excretion and placental transfer. Female and male mice exhibited sex difference in excretion profiles of 6PPD and 6PPDQ. Urine concentrations of 6PPDQ were one order of magnitude lower than those of 6PPD, suggesting lower excretion and higher bioaccumulation of 6PPDQ. In pregnant mice treated with 6PPD or 6PPDQ from embryonic day 11.5 to 15.5, 6PPDQ showed ∼1.5-8 times higher concentrations than 6PPD in placenta, embryo body, and embryo brain, suggesting higher placental transfer of 6PPDQ. Using in vitro dual-luciferase reporter assays, we revealed that 6PPDQ activated the human retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) at concentrations as low as 0.3 μM, which was ∼10-fold higher than the concentrations detected in human urines. 6PPD activated the RXRα at concentrations as low as 1.2 μM. These results demonstrate the exposure risks of 6PPD and 6PPDQ during pregnancy and emphasize the need for further toxicological and epidemiological investigations.

Integration failure of regenerated limb tissue is associated with incongruencies in positional information in the Mexican axolotl

Introduction: Little is known about how the newly regenerated limb tissues in the Mexican axolotl seamlessly integrate with the remaining stump tissues to form a functional structure, and why this doesn't occur in some regenerative scenarios. In this study, we evaluate the phenomenological and transcriptional characteristics associated with integration failure in ectopic limb structures generated by treating anterior-located ectopic blastemas with Retinoic Acid (RA) and focusing on the "bulbus mass" tissue that forms between the ectopic limb and the host site. We additionally test the hypothesis that the posterior portion of the limb base contains anterior positional identities. Methods: The positional identity of the bulbus mass was evaluated by assaying regenerative competency, the ability to induce new pattern in the Accessory Limb Model (ALM) assay, and by using qRTPCR to quantify the relative expression of patterning genes as the bulbus mass deintegrates from the host site. We additionally use the ALM and qRTPCR to analyze the distribution of anterior and posterior positional identities along the proximal/distal limb axis of uninjured and regenerating limbs. Results: The bulbus mass regenerates limb structures with decreased complexity when amputated and is able to induce complex ectopic limb structure only when grafted into posterior-located ALMs. Expressional analysis shows significant differences in FGF8, BMP2, TBX5, Chrdl1, HoxA9, and HoxA11 expression between the bulbus mass and the host site when deintegration is occuring. Grafts of posterior skin from the distal limb regions into posterior ALMs at the base of the limb induce ectopic limb structures. Proximally-located blastemas express significantly less HoxA13 and Ptch1, and significantly more Alx4 and Grem1 than distally located blastemas. Discussion: These findings show that the bulbus mass has an anterior-limb identity and that the expression of limb patterning genes is mismatched between the bulbus mass and the host limb. Our findings additionally show that anterior positional information is more abundant at the limb base, and that anterior patterning genes are more abundantly expressed in proximally located blastemas compared to blastemas in the more distal regions of the limb. These experiments provide valuable insight into the underlying causes of integration failure and further map the distribution of positional identities in the mature limb.

Effects of all-trans and 9-cis retinoic acid on differentiating human neural stem cells in vitro

Cyanobacterial blooms are known sources of environmentally-occurring retinoid compounds, including all-trans and 9-cis retinoic acids (RAs). The developmental hazard for aquatic organisms has been described, while the implications for human health hazard assessment are not yet sufficiently characterized. Here, we employ a human neural stem cell model that can differentiate in vitro into a mixed culture of neurons and glia. Cells were exposed to non-cytotoxic 8-1000 nM all-trans or 9-cis RA for 9-18 days (DIV13 and DIV22, respectively). Impact on biomarkers was analyzed on gene expression (RT-qPCR) and protein level (western blot and proteomics) at both time points; network patterning (immunofluorescence) on DIV22. RA exposure significantly concentration-dependently increased gene expression of retinoic acid receptors and the metabolizing enzyme CYP26A1, confirming the chemical-specific response of the model. Expression of thyroid hormone signaling-related genes remained mostly unchanged. Markers of neural progenitors/stem cells (PAX6, SOX1, SOX2, NESTIN) were decreased with increasing RA concentrations, though a basal population remained. Neural markers (DCX, TUJ1, MAP2, NeuN, SYP) remained unchanged or were decreased at high concentrations (200-1000 nM). Conversely, (astro-)glial marker S100β was increased concentration-dependently on DIV22. Together, the biomarker analysis indicates an RA-dependent promotion of glial cell fates over neural differentiation, despite the increased abundance of neural protein biomarkers during differentiation. Interestingly, RA exposure induced substantial changes to the cell culture morphology: while low concentrations resulted in a network-like differentiation pattern, high concentrations (200-1000 nM RA) almost completely prevented such network patterning. After functional confirmation for implications in network function, such morphological features could present a proxy for network formation assessment, an apical key event in (neuro-)developmental Adverse Outcome Pathways. The described application of a human in vitro model for (developmental) neurotoxicity to emerging environmentally-relevant retinoids contributes to the evidence-base for the use of differentiating human in vitro models for human health hazard and risk assessment.

Toxicological and Teratogenic Effect of Various Food Additives: An Updated Review

Scientific evidence is mounting that synthetic chemicals used as food additives may have harmful impacts on health. Food additives are chemicals that are added to food to keep it from spoiling, as well as to improve its colour and taste. Some are linked to negative health impacts, while others are healthy and can be ingested with little danger. According to several studies, health issues such as asthma, attention deficit hyperactivity disorder (ADHD), heart difficulties, cancer, obesity, and others are caused by harmful additives and preservatives. Some food additives may interfere with hormones and influences growth and development. It is one of the reasons why so many children are overweight. Children are more likely than adults to be exposed to these types of dietary intakes. Several food additives are used by women during pregnancy and breast feeding that are not fully safe. We must take specific precaution to avoid consuming dangerous compounds before they begin to wreak havoc on our health. This study is intended to understand how the preservatives induce different health problem in the body once it is consumed. This review focuses on some specific food additives such as sodium benzoate, aspartame, tartrazine, carrageenan, and potassium benzoate, as well as vitamin A. Long-term use of food treated with the above-mentioned food preservatives resulted in teratogenicity and other allergens, according to the study. Other health issues can be avoided in the future by using natural food additives derived from plants and other natural sources.

Reduced Retinoic Acid Signaling During Gastrulation Induces Developmental Microcephaly

Retinoic acid (RA) is a central signaling molecule regulating multiple developmental decisions during embryogenesis. Excess RA induces head malformations, primarily by expansion of posterior brain structures at the expense of anterior head regions, i.e., hindbrain expansion. Despite this extensively studied RA teratogenic effect, a number of syndromes exhibiting microcephaly, such as DiGeorge, Vitamin A Deficiency, Fetal Alcohol Syndrome, and others, have been attributed to reduced RA signaling. This causative link suggests a requirement for RA signaling during normal head development in all these syndromes. To characterize this novel RA function, we studied the involvement of RA in the early events leading to head formation in Xenopus embryos. This effect was mapped to the earliest RA biosynthesis in the embryo within the gastrula Spemann-Mangold organizer. Head malformations were observed when reduced RA signaling was induced in the endogenous Spemann-Mangold organizer and in the ectopic organizer of twinned embryos. Two embryonic retinaldehyde dehydrogenases, ALDH1A2 (RALDH2) and ALDH1A3 (RALDH3) are initially expressed in the organizer and subsequently mark the trunk and the migrating leading edge mesendoderm, respectively. Gene-specific knockdowns and CRISPR/Cas9 targeting show that RALDH3 is a key enzyme involved in RA production required for head formation. These observations indicate that in addition to the teratogenic effect of excess RA on head development, RA signaling also has a positive and required regulatory role in the early formation of the head during gastrula stages. These results identify a novel RA activity that concurs with its proposed reduction in syndromes exhibiting microcephaly.

Revisiting APP secretases: an overview on the holistic effects of retinoic acid receptor stimulation in APP processing

Alzheimer's disease (AD) is the leading cause of dementia worldwide and is characterized by the accumulation of the β-amyloid peptide (Aβ) in the brain, along with profound alterations in phosphorylation-related events and regulatory pathways. The production of the neurotoxic Aβ peptide via amyloid precursor protein (APP) proteolysis is a crucial step in AD development. APP is highly expressed in the brain and is complexly metabolized by a series of sequential secretases, commonly denoted the α-, β-, and γ-cleavages. The toxicity of resulting fragments is a direct consequence of the first cleaving event. β-secretase (BACE1) induces amyloidogenic cleavages, while α-secretases (ADAM10 and ADAM17) result in less pathological peptides. Hence this first cleavage event is a prime therapeutic target for preventing or reverting initial biochemical events involved in AD. The subsequent cleavage by γ-secretase has a reduced impact on Aβ formation but affects the peptides' aggregating capacity. An array of therapeutic strategies are being explored, among them targeting Retinoic Acid (RA) signalling, which has long been associated with neuronal health. Additionally, several studies have described altered RA levels in AD patients, reinforcing RA Receptor (RAR) signalling as a promising therapeutic strategy. In this review we provide a holistic approach focussing on the effects of isoform-specific RAR modulation with respect to APP secretases and discuss its advantages and drawbacks in subcellular AD related events.

Isotretinoin and neuropsychiatric side effects: Continued vigilance is needed

Background

Isotretinoin (13-cis-retinoic acid, marketed under the names Accutane, Roaccutane, and others) is an effective treatment for acne that has been on the market for over 30 years, although reports of neuropsychiatric side effects continue to be reported. Isotretinoin is an isomer of the active form of Vitamin A, 13-trans-retinoic acid, which has known psychiatric side effects when given in excessive doses, and is part of the family of compounds called retinoids, which have multiple functions in the central nervous system.

Methods

The literature was reviewed in pubmed and psychinfo for research related to isotretinoin and neuropsychiatric side effects including depression, suicidal thoughts, suicide, mania, anxiety, impulsivity, emotional lability, violence, aggression, and psychosis.

Results

Multiple case series have shown that successful treatment of acne with isotretinoin results in improvements in measures of quality of life and self esteem However, studies show individual cases of clinically significant depression and other neuropsychiatric events that, although not common, are persistent in the literature. Since the original cases of depression were reported to the United States Food and Drug Administration, numerous cases have been reported to regulatory agencies in the United Kingdom, France, Ireland, Denmark, Australia, Canada, and other countries, making isotretinoin one of the top five medications in the world associated with depression and other neuropsychiatric side effects. Clinicians are advised to warn patients of the risks of neuropsychiatric side effects with isotretinoin which may arise from the medication itself, and not just as a side effect of acne or youth.

Maternal Transfer of 2-Ethylhexyl Diphenyl Phosphate Leads to Developmental Toxicity Possibly by Blocking the Retinoic Acid Receptor and Retinoic X Receptor in Japanese Medaka (Oryzias latipes)

2-Ethylhexyl diphenyl phosphate (EHDPP) has been detected in wild fish with high concentrations, which may pose a risk in the embryo development considering its potential maternal transfer. In this study, EHDPP was demonstrated to elicit antagonistic activity to medaka retinoic acid receptor (mRAR) and retinoic X receptor (mRXR) with 50% inhibitory concentration of 18 and 36 μM, respectively. After adult female medaka were exposed to EHDPP at 156, 405, and 1161 ng/L for 35 days, the embryonic EHDPP concentrations (364-4824 ng/g lipid weight (lw)) were higher than those in the maternal tissues (15.0-4166 ng/g lw), showing notable maternal transfer. The embryonic concentration of EHDPP decreased limitedly during 1-2 day post-fertilization (dpf, the main developmental window of eye) but then decreased sharply after 2 dpf. The transcript abundance of cyp26a1 was inhibited and subsequent increasing embryonic all-trans RA level was observed in embryos, showing RAR/RXR antagonistic activity. These results may specifically contribute to the increased eye deformity incidences in all exposure groups (up to 8.0%; 51/637) relative to the control (1.0%, 7/733). The response behavior of the larvae to light stimulation was impaired in a dose-dependent manner, demonstrating a vision disorder. Because such developmental toxicities were observed at the environmental level, EHDPP may pose a threat to the survival of wild larvae and therefore a population risk for wild fish.

Modulation of retinoid signaling: therapeutic opportunities in organ fibrosis and repair

The vitamin A metabolite, retinoic acid, is an important signaling molecule during embryonic development serving critical roles in morphogenesis, organ patterning and skeletal and neural development. Retinoic acid is also important in postnatal life in the maintenance of tissue homeostasis, while retinoid-based therapies have long been used in the treatment of a variety of cancers and skin disorders. As the number of people living with chronic disorders continues to increase, there is great interest in extending the use of retinoid therapies in promoting the maintenance and repair of adult tissues. However, there are still many conflicting results as we struggle to understand the role of retinoic acid in the multitude of processes that contribute to tissue injury and repair. This review will assess our current knowledge of the role retinoic acid signaling in the development of fibroblasts, and their transformation to myofibroblasts, and of the potential use of retinoid therapies in the treatment of organ fibrosis.

A Fragment of Adhesion Molecule L1 Binds to Nuclear Receptors to Regulate Synaptic Plasticity and Motor Coordination

Proteolytic cleavage of the neuronal isoform of the murine cell adhesion molecule L1, triggered by stimulation of the cognate L1-dependent signaling pathways, results in the generation and nuclear import of an L1 fragment that contains the intracellular domain, the transmembrane domain, and part of the extracellular domain. Here, we show that the LXXLL and FXXLF motifs in the extracellular and transmembrane domain of this L1 fragment mediate the interaction with the nuclear estrogen receptors α (ERα) and β (ERβ), peroxisome proliferator-activated receptor γ (PPARγ), and retinoid X receptor β (RXRβ). Mutations of the LXXLL motif in the transmembrane domain and of the FXXLF motif in the extracellular domain disturb the interaction of the L1 fragment with these nuclear receptors and, when introduced by viral transduction into mouse embryos in utero, result in impaired motor coordination, learning and memory, as well as synaptic connectivity in the cerebellum, in adulthood. These impairments are similar to those observed in the L1-deficient mouse. Our findings suggest that the interplay of nuclear L1 and distinct nuclear receptors is associated with synaptic contact formation and plasticity.

Effect of Fetal Mouse Lung Tissue Co-Culture on In Vitro Maturation of Mouse Immature Oocytes

OBJECTIVES

The aim of this study was to evaluate the fetal mouse lung tissue co-culture on in vitro maturation (IVM) of mouse immature oocytes.

MATERIALS AND METHODS

In this experimental study, germinal vesicle (GV) oocytes from ovaries of a group of 25 female mice, 6-8 weeks of age, were dissected after being stimulated by 7.5 IU pregnant mare serum gonadotropin (PMSG) through an intraperitoneal (IP) injection. The fetal lung tissues were then prepared and cultured individually. A total number of 300 oocytes were cultured in the following three groups for 24 hours: control group (n=100) containing only base medium, group I (n=100) containing base medium co-cultured with 11.5- to 12.5-day old fetal mouse lung tissues, and group II (n=100) containing base medium co-cultured with 12.5- to 13.5-day old fetal mouse lung tissues. The proportion of GV and metaphase І (MI) oocytes matured into MІІ oocytes were compared among the three groups using analysis of variance (ANOVA). Correlation test were also used to evaluate the successful rate of IVM oocytes.

RESULTS

The proportions of GV oocytes reaching MІІ stage were 46, 65, and 56%, in control, I and II groups, respectively (P<0.05). The percentage of the oocytes remaining at the GV stage were higher in control group as compared with two treatment groups (P<0.05).

CONCLUSIONS

This study indicated that fetal mouse lung tissue co-culture method increased the percentage of GV oocytes reaching MII stage.

Separate development of the maxilla and mandible is controlled by regional signaling of the maxillomandibular junction during avian development

BACKGROUND

Syngnathia is a congenital craniofacial disorder characterized by bony or soft tissue fusion of upper and lower jaws. Previous studies suggested some causative signals, such as Foxc1 or Bmp4, cause the disruption of maxillomandibular identity, but their location and the interactive signals involved remain unexplored. We wanted to examine the embryonic origin of syngnathia based on the assumption that it may be located at the separation between the maxillary and mandibular processes. This region, known as the maxillomandibular junction (MMJ), is involved in segregation of cranial neural crest-derived mesenchyme into the presumptive upper and lower jaws.

RESULTS

Here we investigated the role of Fgf, Bmp, and retinoid signaling during development of MMJ in chicken embryos. By changing the levels of these signals with bead implants, we induced syngnathia with microstomia on the treated side, which showed increased Barx1 and neural cell adhesion molecule (NCAM) expression. Redistribution of proliferating cells was also observed at the proximal region to maxillary and mandibular arch around MMJ.

CONCLUSIONS

We propose that interactive molecular signaling by Fgfs, Bmps, and retinoids around MMJ is required for normal separation of the maxilla and mandible, as well as the proper positioning of beak commissure during early facial morphogenesis. Developmental Dynamics 246:28-40, 2017. © 2016 Wiley Periodicals, Inc.

Anti-oxidant profiles and markers of oxidative stress in preterm neonates

BACKGROUND

Preterm birth is associated with an increased oxidant burden which places these infants at a higher risk of injury.

AIMS

This prospective study aimed to assess levels of antioxidants and a marker of oxidative stress in preterm neonates.

OBJECTIVES

(i) To compare levels of anti-oxidants [vitamin A, vitamin E, catalase, total anti-oxidant status (TAS)] as well as malondialdehyde level (MDA) (a marker of lipid peroxidation) between preterm and full-term neonates; (ii) to determine changes in the values of measured vitamins at birth and at discharge among preterm neonates; and (iii) to compare levels of anti-oxidants with MDA levels in relation to complications of prematurity and outcome.

METHODS

The study was undertaken in 100 preterm neonates and 100 full-term neonates as a control group. MDA was estimated by a thiobarbituric acid-reactive technique; TAS was determined using a Randox assay kit; catalase activity was measured spectrophotometrically and vitamin A and E levels were estimated by high performance liquid chromatography.

RESULTS

The plasma levels of vitamin A, vitamin E, TAS and catalase were significantly lower in the preterm than in the full-term group (P < 0.01), and the plasma level of MDA was significantly higher in preterm than full-term neonates (P < 0.01). Vitamin A and E levels in preterm neonates were significantly higher at discharge than at birth (P < 0.01). Vitamin A, vitamin E and catalase levels at birth were significantly lower in patients who developed necrotizing enterocolitis or bronchopulmonary dysplasia than in those who did not.

CONCLUSION

Preterm neonates are exposed to increased oxidant stress at birth and are susceptible to anti-oxidant deficiencies. A higher dose of enteral vitamin A supplementation in preterm neonates might reduce morbidity and improve outcome. Further studies are warranted to evaluate the appropriate dose of oral vitamin E supplementation for preterm neonates.

Altered microRNA expression profiles in a rat model of spina bifida

MicroRNAs (miRNAs) are dynamically regulated during neurodevelopment, yet few reports have examined their role in spina bifida. In this study, we used an established fetal rat model of spina bifida induced by intragastrically administering olive oil-containing all-trans retinoic acid to dams on day 10 of pregnancy. Dams that received intragastric administration of all-trans retinoic acid-free olive oil served as controls. The miRNA expression profile in the amniotic fluid of rats at 20 days of pregnancy was analyzed using an miRNA microarray assay. Compared with that in control fetuses, the expression of miRNA-9, miRNA-124a, and miRNA-138 was significantly decreased (> 2-fold), whereas the expression of miRNA-134 was significantly increased (> 4-fold) in the amniotic fluid of rats with fetuses modeling spina bifida. These results were validated using real-time quantitative reverse-transcription polymerase chain reaction. Hierarchical clustering analysis of the microarray data showed that these differentially expressed miRNAs could distinguish fetuses modeling spina bifida from control fetuses. Our bioinformatics analysis suggested that these differentially expressed miRNAs were associated with many cytological pathways, including a nervous system development signaling pathway. These findings indicate that further studies are warranted examining the role of miRNAs through their regulation of a variety of cell functional pathways in the pathogenesis of spina bifida. Such studies may provide novel targets for the early diagnosis and treatment of spina bifida.

Effect of vitamin A supplementation on the urinary retinol excretion in very low birth weight infants

Despite high-dose vitamin A supplementation of very low birth weight infants (VLBW, <1500 g), their vitamin A status does not improve substantially. Unknown is the impact of urinary retinol excretion on the serum retinol concentration in these infants. Therefore, the effect of high-dose vitamin A supplementation on the urinary vitamin A excretion in VLBW infants was investigated. Sixty-three VLBW infants were treated with vitamin A (5000 IU intramuscular, 3 times/week for 4 weeks); 38 untreated infants were classified as control group. On days 3 and 28 of life, retinol, retinol-binding protein 4 (RBP4), glomerular filtration rate, proteinuria, and Tamm-Horsfall protein were quantified in urine. On day 3 of life, substantial retinol and RBP4 losses were found in both groups, which significantly decreased until day 28. Notwithstanding, the retinol excretion was higher (P < 0.01) under vitamin A supplementation as compared to infants of the control group. On day 28 of life, the urinary retinol concentrations were predictive for serum retinol concentrations in the vitamin A treated (P < 0.01), but not in the control group (P = 0.570).

CONCLUSION

High urinary retinol excretion may limit the vitamin A supplementation efficacy in VLBW infants. Advanced age and thus postnatal kidney maturation seems to be an important contributor in the prevention of urinary retinol losses.

A newly established culture method highlights regulatory roles of retinoic acid on morphogenesis and calcification of mammalian limb cartilage

During mammalian embryogenesis, sclerotome-derived chondrocytes in the limb bud are arranged into a complicated bone shape with specific areas undergoing hypertrophy and calcification, creating a region-specific mineralized pattern in the cartilage. To follow chondrogenesis progression in vitro, we isolated limb cartilage from mice on embryonic day 13 (E13) and cultured it at the air-liquid interface after microsurgical removal of the ectoderm/epidermis. Explants underwent proper morphogenesis, giving rise to complete templates for limb bones in vitro. We found that region-specific calcification patterns resembling limbs of prepartum mature embryos could be induced in explants using culture medium containing high concentrations of CaCl2 (Ca), ascorbic acid (AA), and β-glycerophosphoric acid (BGP). In this culture system, excess amounts of all-trans retinoic acid (RA) severely disrupted morphogenesis and calcification patterns in limb cartilage. These effects were more pronounced in forearms than in phalanges. Although dissociated, the nascent chondrocytes in culture did not give rise to cartilage units even though augmented calcification was induced in these cell aggregates in the presence of RA. Taken together, our newly established culture system revealed that RA independently regulates three-dimensional morphogenesis and calcification.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

Dietary sugar in healthy female primates perturbs oocyte maturation and in vitro preimplantation embryo development

The consumption of refined sugars continues to pose a significant health risk. However, nearly nothing is known about the effects of sugar intake by healthy women on the oocyte or embryo. Using rhesus monkeys, we show that low-dose sucrose intake over a 6-month period has an impact on the oocyte with subsequent effects on the early embryo. The ability of oocytes to resume meiosis was significantly impaired, although the differentiation of the somatic component of the ovarian follicle into progesterone-producing cells was not altered. Although the small subset of oocytes that did mature were able to be fertilized in vitro and develop into preimplantation blastocysts, there were >1100 changes in blastocyst gene expression. Because sucrose treatment ended before fertilization, the effects of sugar intake by healthy primates are concluded to be epigenetic modifications to the immature oocyte that are manifest in the preimplantation embryo.

A new approach to highly sensitive determination of retinoic acid isomers by preconcentration with CdSe quantum dots

Unusual amounts of retinoic acid (RA) isomers play an important role in abnormal morphological development of mammals; such as rat embryos. Each isomer of RA has a unique function in first steps of embryonic life. In the current study, a new method for preconcentration and simultaneous determination of all-trans retinoic acid, 13-cis retinoic acid, 9-cis retinoic acid and 9,13-di-cis retinoic acid in rat whole rudimentary embryo culture (RWEC) has been developed. RA isomers were extracted from samples by conjugation to appropriate amount of surface modified CdSe quantum dots (QDs) prior to HPLC/UV determination. In order to quickly release of the analytes with unchanged form, separated RA-QD conjugation were irradiated by intensive near infrared wavelength (NIR). Low energy NIR irradiation results in maintaining the primary forms of RA isomers during the release. The conjugation and release mechanisms were described and experimental parameters were investigated in detail. Under optimized conditions, the method was linear in the range of 0.040-34.600 pmol g(-1) for all-trans RA (R(2)=0.9996), 0.070-34.200 pmol g(-1) for 13-cis RA (R(2)=0.9992), 0.050-35.300 pmol g(-1) for 9,13-di-cis RA (R(2)=0.9998) and 0.050-32.900 pmol g(-1) for 9-cis RA (R(2)=0.9990). The present method can be useful for retinoic acid monitoring in clinical studies.

Identification and quantitation of biomarkers for radiation-induced injury via mass spectrometry

Biomarker identification and validation for radiation exposure is a rapidly expanding field encompassing the need for well defined animal models and advanced analytical techniques. The resources within the consortium, Medical Countermeasures Against Radiological Threats (MCART), provide a unique opportunity for accessing well defined animal models that simulate the key sequelae of the acute radiation syndrome and the delayed effects of acute radiation exposure. Likewise, the use of mass spectrometry-based analytical techniques for biomarker discovery and validation enables a robust analytical platform that is amenable to a variety of sample matrices and considered the benchmark for biomolecular identification and quantitation. Herein, the authors demonstrate the use of two targeted mass spectrometry approaches to link established MCART animal models to identified metabolite biomarkers. Circulating citrulline concentration was correlated to gross histological gastrointestinal tissue damage, and retinoic acid production in lung tissue was established to be reduced at early and late time points post high dose irradiation. Going forward, the use of mass spectrometry-based metabolomics coupled to well defined animal models provides the unique opportunity for comprehensive biomarker discovery.

Dietary intake of natural antioxidants: vitamins and polyphenols

Oxidative stress is a condition in which oxidant metabolites exert their toxic effect because of an increased production or an altered cellular mechanism of protection; oxidative stress is rapidly gaining recognition as a key phenomenon in chronic diseases. Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions by being oxidized themselves. Endogenous defence mechanisms are inadequate for the complete prevention of oxidative damage, and different sources of dietary antioxidants may be especially important. This article calls attention to the dietary antioxidants, such as vitamins A, C, and E and polyphenols. Compelling evidence has led to the conclusion that diet is a key environmental factor and a potential tool for the control of chronic diseases. More specifically, fruits and vegetables have been shown to exert a protective effect. The high content of minerals and natural antioxidant as vitamins A, C, and E and polyphenols in fruits and vegetables may be a main factor responsible for these effects.

Retinoic acid is involved in the metamorphosis of the anal fin into an intromittent organ, the gonopodium, in the green swordtail (Xiphophorus hellerii)

In poeciliid fish the male anal fin has been transformed into a gonopodium, an intromittent organ required for internal fertilization. Elevated testosterone levels induce metamorphosis of a subset of anal fin rays to grow and form the specialized terminal structures of the gonopodium. The molecular mechanisms underlying these processes are largely unknown. Here, we investigated whether retinoic acid (RA) signaling is involved in gonopodium development in the swordtail Xiphophorus hellerii. We showed that aldh1a2, a RA synthesizing enzyme, and the RA receptors, rar-ga and rar-gb, are expressed in anal fins during metamorphosis. aldh1a2 expression is regulated by testosterone in a concentration-dependent manner and is up-regulated in both hormone-induced and naturally developing gonopodia. Androgen receptor (ar), a putative regulator of gonopodial development, is co-expressed with aldh1a2 and the RA receptors in gonopodial rays. Importantly, experimental increase of RA signaling promoted growth of the gonopodium and increased the number of new segments. Based on gene expression analyses and pharmacological manipulation of gonopodium development, we show that the RA signaling pathway is activated in response to androgen signaling and promotes fin ray growth and development during the metamorphosis of the anal fin into the gonopodium.

Low maternal retinol as a risk factor for schizophrenia in adult offspring

BACKGROUND

Prenatal micronutrient deficiency has been linked to later development of schizophrenia among offspring; however, no study has specifically investigated the association between vitamin A and this disorder. Vitamin A is an essential nutrient which is required by the early embryo and fetus for gene expression and regulation, cell differentiation, proliferation and migration. Previous work suggests that vitamin A deficiency in the second trimester may be particularly relevant to the etiopathogenesis of neurobehavioral phenotypes some of which are observed in schizophrenia.

METHODS

We examined whether low maternal vitamin A levels in the second trimester are associated with the risk of schizophrenia and other schizophrenia spectrum disorders (SSD) in the Prenatal Determinants of Schizophrenia study; third trimester vitamin A levels were also examined in relation to SSD. The cases were derived from a population-based birth cohort; all cohort members belonged to a prepaid health plan. Archived maternal serum samples were assayed for vitamin A in cases (N=55) and up to 2 controls per case (N=106) matched on length of membership in the health plan, date of birth (±28 days), sex, and gestational timing and availability of archived maternal sera.

RESULTS

For the second trimester, low maternal vitamin A, defined as values in the lowest tertile of the distribution among controls, was associated with a greater than threefold increased risk of SSD, adjusting for maternal education and age (OR=3.04, 95% CI=1.06, 8.79, p=.039). No association between third trimester maternal vitamin A and SSD was observed.

CONCLUSIONS

Although further investigations are warranted, this is the first birth cohort study to our knowledge to report an association between low maternal vitamin A levels and SSD among offspring.

Morphological defects in a novel Rdh10 mutant that has reduced retinoic acid biosynthesis and signaling

Retinoic acid (RA) signaling is necessary for proper patterning and morphogenesis during embryonic development. Tissue-specific RA signaling requires precise spatial and temporal synthesis of RA from retinal by retinaldehyde dehydrogenases (Raldh) and the conversion of retinol to retinal by retinol dehydrogenases (Rdh) of the short-chain dehydrogenase/reducatase gene family (SDR). The SDR, retinol dehydrogenase 10 (RDH10), is a major contributor to retinal biosynthesis during mid-gestation. We have identified a missense mutation in the Rdh10 gene (Rdh10(m366Asp) ) using an N-ethyl-N-nitrosourea-induced forward genetic screen that result in reduced RA levels and signaling during embryonic development. Rdh10(m366Asp) mutant embryos have unique phenotypes, such as edema, a massive midline facial cleft, and neurogenesis defects in the forebrain, that will allow the identification of novel RA functions.

Retinoic acid and affective disorders: the evidence for an association

OBJECTIVE

Isotretinoin (13-cis-retinoic acid), approved by the US Food and Drug Administration for the treatment of acne, carries a black box warning related to the risk of depression, suicide, and psychosis. Retinoic acid, the active form of vitamin A, regulates gene expression in the brain, and isotretinoin is its 13-cis isomer. Retinoids represent a group of compounds derived from vitamin A that perform a large variety of functions in many systems, in particular the central nervous system, and abnormal retinoid levels can have neurologic effects. Although infrequent, proper recognition and treatment of psychiatric side effects in acne patients is critical given the risk of death and disability. This article reviews the evidence for isotretinoin's relationships with depression and suicidality.

DATA SOURCES

The PsycINFO, MEDLINE, and PubMed searchable database indexes were searched for articles published in the English language from 1960 to June 2010 using the key words isotretinoin, retinoids, retinoic acid, depression, depressive disorders, and vitamin A. Evidence examined includes (1) case reports; (2) temporal association between onset of depression and exposure to the drug; (3) challenge-rechallenge cases; (4) class effect (other compounds in the same class, like vitamin A, having similar neuropsychiatric effects); (5) dose response; and (6) biologically plausible mechanisms.

STUDY SELECTION

All articles in the literature related to isotretinoin, depression, and suicide were reviewed, as well as articles related to class effect, dose response, and biologic plausibility.

DATA EXTRACTION

Information from individual articles in the literature was extracted, including number of episodes of depression, suicidality, suicide, psychosis, violence and aggression, past psychiatric history, time of onset in relation to isotretinoin usage, medication dosage, duration of treatment, and dechallenge and challenge history.

RESULTS

The literature reviewed is consistent with associations of isotretinoin administration with depression and with suicide in a subgroup of vulnerable individuals.

CONCLUSIONS

The relationship between isotretinoin and depression may have implications for a greater understanding of the neurobiology of affective disorders.

The expression pattern of aldehyde dehydrogenase 1 (ALDH1) is an independent prognostic marker for low survival in colorectal tumors

BACKGROUND

Aldehyde dehydrogenase-1 (ALDH1) is involved in the regulation of cell proliferation and differentiation. Moreover, it is a marker for cancer stem cells (CSC). As CSCs were shown to be the driving force of tumor progression and metastases we suspected that the expression of ALDH1 correlated with the prognostic 5 year survival of colorectal cancer.

METHODS

ALDH1 expression was analyzed in a highly stratified collective of 186 T3 N0 M0 G2 primary colorectal cancer specimens applying immunohistochemistry. For the analysis a scoring system for the expression of ALDH1 was developed that was aided by the pattern of the subcellular expression of beta-catenin which is a well known indicator for colorectal CSCs.

RESULTS

First, ALDH1 expression could be assigned to two groups which correlated with the absence or presence of nuclear beta-catenin expression. Second, ALDH1 group 2 expression patterning correlated highly significantly with low long term survival (p=0.010) of patients with T3 N0 M0 G2 colorectal cancer. This correlation was found univariately and when applying the multivariate Cox-model.

CONCLUSION

ALDH1 expression pattern is an independent prognostic marker for survival of T3 N0 M0 G2 colorectal cancer patients.

Analysis, occurrence, and function of 9-cis-retinoic acid

Metabolic conversion of vitamin A (retinol) into retinoic acid (RA) controls numerous physiological processes. 9-cis-retinoic acid (9cRA), an active metabolite of vitamin A, is a high affinity ligand for retinoid X receptor (RXR) and also activates retinoic acid receptor (RAR). Despite the identification of candidate enzymes that produce 9cRA and the importance of RXRs as established by knockout experiments, in vivo detection of 9cRA in tissue was elusive until recently when 9cRA was identified as an endogenous pancreas retinoid by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology. This review will discuss the current status of the analysis, occurrence, and function of 9cRA. Understanding both the nuclear receptor-mediated and non-genomic mechanisms of 9cRA will aid in the elucidation of disease physiology and possibly lead to the development of new retinoid-based therapeutics. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.

Effects of retinoids on the in vitro development of Capra hircus embryos to blastocysts in two different culture systems

The objective of this study was to evaluate the effect of retinol (RT) and retinoic acid (RA) on the in vitro development of pre-implantation goat embryos cultured in potassium simplex optimized medium or synthetic oviduct fluid or cocultured in oviductal cells monolayer either in potassium simplex optimized medium or synthetic oviduct fluid. A total of 2407 cumulus-oocyte complexes were aspirated from 2 to 6 mm ovarian follicles from slaughtered animals. Selected cumulus-oocyte complexes were subjected to in vitro maturation in TCM 199 for 24 h at 39 °C in an atmosphere of 5% (v/v) CO(2) in humidified air. In vitro fertilization was performed in modified defined medium. Eighteen hours after in vitro fertilization, cumulus cells were removed and presumptive zygotes were randomly distributed into experimental groups. In Experiment 1, presumptive zygotes were cultured in potassium simplex optimized medium, potassium simplex optimized medium + RT, potassium simplex optimized medium + retinoic acid, synthetic oviduct fluid, synthetic oviduct fluid + RT and synthetic oviduct fluid + RA at 39 °C in a humidified atmosphere of 5% (v/v) CO(2), 5% (v/v) O(2) and 90% (v/v) N(2). In Experiment 2, presumptive zygotes were cocultured in potassium simplex optimized medium + oviductal cells monolayer, potassium simplex optimized medium + RT + oviductal cells monolayer, potassium simplex optimized medium + RA + oviductal cells monolayer, synthetic oviduct fluid + oviductal cells monolayer, synthetic oviduct fluid + RT + oviductal cells monolayer and synthetic oviduct fluid + RA + oviductal cells monolayer in an atmosphere of 5% (v/v) CO(2) in humidified air. In both experiments, media were partially changed on day 2 after in vitro fertilization and unfertilized oocytes were excluded from the experiment. Embryos were cultured or cocultured for 8 days. In Experiment 1, there was no effect of RT or RA supplementation on the proportion of oocytes that reached the morula or blastocyst stages. By contrast, Experiment 2 demonstrated that the addition of 0.28 μg/ml RT and 0.5 μm RA to the embryo culture media stimulated (p < 0.05) development to the morula and blastocyst stages under the coculture conditions tested. In conclusion, retinoids play an important role in pre-implantation development of goat embryos and can be used to enhance in vitro embryo production.

Role of PPARs and Retinoid X Receptors in the Regulation of Lung Maturation and Development

Understanding lung development has significant importance to public health because of the fact that interruptions in the normal developmental processes can have prominent effects on childhood and adult lung health. It is widely appreciated that the retinoic acid (RA) pathway plays an important role in lung development. Additionally, PPARs are believed to partner with receptors of this pathway and therefore could be considered extensions of retinoic acid function, including during lung development. This review will begin by introducing the relationship between the retinoic acid pathway and PPARs followed by an overview of lung development stages and regulation to conclude with details on PPARs and the retinoic acid pathway as they may relate to lung development.

Glyphosate-based herbicides produce teratogenic effects on vertebrates by impairing retinoic acid signaling

The broad spectrum herbicide glyphosate is widely used in agriculture worldwide. There has been ongoing controversy regarding the possible adverse effects of glyphosate on the environment and on human health. Reports of neural defects and craniofacial malformations from regions where glyphosate-based herbicides (GBH) are used led us to undertake an embryological approach to explore the effects of low doses of glyphosate in development. Xenopus laevis embryos were incubated with 1/5000 dilutions of a commercial GBH. The treated embryos were highly abnormal with marked alterations in cephalic and neural crest development and shortening of the anterior-posterior (A-P) axis. Alterations on neural crest markers were later correlated with deformities in the cranial cartilages at tadpole stages. Embryos injected with pure glyphosate showed very similar phenotypes. Moreover, GBH produced similar effects in chicken embryos, showing a gradual loss of rhombomere domains, reduction of the optic vesicles, and microcephaly. This suggests that glyphosate itself was responsible for the phenotypes observed, rather than a surfactant or other component of the commercial formulation. A reporter gene assay revealed that GBH treatment increased endogenous retinoic acid (RA) activity in Xenopus embryos and cotreatment with a RA antagonist rescued the teratogenic effects of the GBH. Therefore, we conclude that the phenotypes produced by GBH are mainly a consequence of the increase of endogenous retinoid activity. This is consistent with the decrease of Sonic hedgehog (Shh) signaling from the embryonic dorsal midline, with the inhibition of otx2 expression and with the disruption of cephalic neural crest development. The direct effect of glyphosate on early mechanisms of morphogenesis in vertebrate embryos opens concerns about the clinical findings from human offspring in populations exposed to GBH in agricultural fields.

Ethanol impairs activation of retinoic acid receptors in cerebellar granule cells in a rodent model of fetal alcohol spectrum disorders

BACKGROUND

Ethanol is the main addictive and neurotoxic constituent of alcohol. Ethanol exposure during embryonic development causes dysfunction of the central nervous system (CNS) and leads to fetal alcohol spectrum disorders. The cerebellum is one of the CNS regions that are particularly vulnerable to ethanol toxic effects. Retinoic acid (RA) is a physiologically active metabolite of vitamin A that is locally synthesized in the cerebellum. Studies have shown that RA is required for neuronal development, but it remains unknown if ethanol impairs RA signaling and thus induces neuronal malformations. In this study, we tested the hypothesis that ethanol impairs the expression and activation of RA receptors in cerebellum and in cerebellar granule cells.

METHODS

The cerebellum of ethanol unexposed and exposed pups was used to study the expression of retinoic acid receptors (RARs or RXRs) by immunohistochemistry and by Western blot analysis. We also studied the effect of ethanol on expression of RA receptors in the cerebellar granule cells. Activation of RA receptors (DNA-binding activities) in response to high-dose ethanol was determined by electrophoretic mobility shift and supershift assays.

RESULTS

Findings from these studies demonstrated that ethanol exposure reduced the expression of RARalpha/gamma while it increased the expression of RXRalpha/gamma in the cerebellum and in cerebellar granule neurons. Immuno-histological studies further strengthened the expression pattern of RA receptors in response to ethanol. The DNA-binding activity of RARs was reduced, while DNA-binding activity of RXRs was increased in response to ethanol exposure.

CONCLUSION

For the first time, our studies have demonstrated that high-dose ethanol affects the expression and activation of RA receptors, which could impair the signaling events and induce harmful effects on the survival and differentiation of cerebellar granule cells. Taken together, these findings could provide insight into the treatment options for brain defects caused by excessive ethanol exposure, such as in Fetal Alcohol Spectrum Disorders.

Epigenetic remodeling of chromatin architecture: exploring tumor differentiation therapies in mesenchymal stem cells and sarcomas

Sarcomas are the mesenchymal-derived malignant tumors of connective tissues (e.g., fat, bone, and cartilage) presumed to arise from aberrant development or differentiation of mesenchymal stem cells (MSCs). Appropriate control of stem cell maintenance versus differentiation allows for normal connective tissue development. Current theories suggest that loss of this control--through accumulation of genetic lesions in MSCs at various points in the differentiation process--leads to development of sarcomas, including undifferentiated, high grade sarcoma tumors. The initiation of stem cell differentiation is highly associated with alteration of gene expression, which depends on chromatin remodeling. Epigenetic chromatin modifying agents have been shown to induce cancer cell differentiation and are currently being used clinically to treat cancer. This review will focus on the importance of epigenetic chromatin remodeling in the context of mesenchymal stem cells, sarcoma tumorigenesis and differentiation therapy.

Signalling with retinoids in the human lung: validation of new tools for the expression study of retinoid receptors

Background

Retinoid Receptors are involved in development and cell homeostasis. Alterations of their expressions have been observed in lung cancer. However, retinoid chemoprevention trials in populations at risk to develop such tumors have failed. Therefore, the pertinence of new clinical trials using second generation retinoid requires prior better understanding of retinoid signalling. This is our aim when validating extensively research tools, focused on Retinoic Acid Receptor beta, whose major role in lung cancer is documented.

Methods

Biocomputing was used to assess the genomic organization of RAR beta. Its putative RAR-beta1' promoter features were investigated experimentally. Specific measures realized, with qRT-PCR Syber Green assays and a triplex of Taqman probes, were extensively validated to establish Retinoid Receptors mRNAs reference values for in vivo normal human bronchial cells, lung tumors and cell lines. Finally, a pan-RAR-beta antibody was generated and extensively validated by western-blot and immunoprecipitation.

Results

No promoter-like activity was found for RAR-beta1'. RAR-beta2 mRNAs increase signs the normal differentiation of the human bronchial epithelium while a decrease is observed in most lung cancer cell lines. Accordingly, it is also, along with RXR beta, down-regulated in lung tumors. When using nuclear extracts of BEAS-2B and normal lung cells, only the RAR-beta2 long protein isoform was recognized by our antibody.

Conclusion

Rigorous samples processing and extensive biocomputing, were the key factors for this study. mRNA reference values and validated tools can now be used to advance researches on retinoid signalling in the lung.

Induction of Wnt5a-expressing mesenchymal cells adjacent to the cloacal plate is an essential process for its proximodistal elongation and subsequent anorectal development

Anorectal malformations encompass a broad spectrum of congenital defects and are related to the development of the genital tubercle, including the cloacal plate and urorectal septum. To explore the cellular and molecular basis of anorectal malformations, we analyzed the pathogenetic process using two mouse models: Danforth's short tail (Sd) and all-trans retinoic acid (ATRA)-treated mice. Embryologically, the cloacal plate may be divided into distal and proximal parts, with the distal part subdivided into ventral and dorsal parts. In the two mouse models, anorectal malformations occur due to improper development of the proximal part of the cloacal plate. At 10.5 days postcoitus (dpc), in Sd homozygotes, there was a lack of Shh expression only in the cloacal plate and the endoderm around the cloacal plate. In addition, Wnt5a was not expressed in the mesoderm adjacent to the cloacal plate in the two mouse models, and Axin2, which is regulated by Wnt signaling, was not expressed in the dorsal part of the cloacal plate at 12.5 dpc. Based on these results, we suggest that Wnt5a, which is downstream of Shh signaling, and Axin2 affect the development of the proximal part of the cloacal plate.

Concentrations of antioxidant vitamins in maternal and cord serum and their effect on birth outcomes

BACKGROUND

Emerging evidence indicates that maternal oxidative stress during pregnancy could impair fetal growth and that antioxidant vitamins (e.g. vitamins A, E and C) have a significant role in maintaining physiological processes of pregnancy and growth.

AIMS

To determine the concentrations of vitamins A, E, and C in pair-matched maternal and cord serum samples of neonate, and thus to investigate the relationship between maternal serum levels of these vitamins at delivery and birth outcomes.

METHODS

A total of 143 mother-neonate pairs were recruited into the cross-sectional descriptive study. Demographic information was investigated by questionnaire. After delivery, both cord and maternal blood were collected for quantification of serum levels of vitamins A, E and C by HPLC.

RESULTS

Maternal serum levels of vitamins A and E were significantly higher than those in cord serum. In contrast, vitamin C level in cord serum was significantly higher than that in maternal serum. Further, we found that maternal vitamin A status was significantly correlated to both birth weight (r=0.19, p=0.0419) and birth height (r=0.21, p=0.0311), and these were manifested by these findings: (i) per 250.2 g reduction in birth weight concomitant with 1 micromol/L increase in maternal serum vitamin A level (p<0.01; 95% CI: 56.9-451.5); and (ii) per 1% increase in the ratio of serum vitamin A level of neonate to mother concomitant with 0.8 cm increase in birth height (p=0.049; 95% CI: 0.004-1.639).

CONCLUSION

Maternal vitamin A, but not vitamins E and C, during pregnancy had a significant effect on birth outcomes. Further studies are necessary to investigate the role of these antioxidant vitamins in fetal growth at various gestation stages.

Cholesterol metabolism: the main pathway acting downstream of cytochrome P450 oxidoreductase in skeletal development of the limb

Cytochrome P450 oxidoreductase (POR) is the obligate electron donor for all microsomal cytochrome P450 enzymes, which catalyze the metabolism of a wide spectrum of xenobiotic and endobiotic compounds. Point mutations in POR have been found recently in patients with Antley-Bixler-like syndrome, which includes limb skeletal defects. In order to study P450 function during limb and skeletal development, we deleted POR specifically in mouse limb bud mesenchyme. Forelimbs and hind limbs in conditional knockout (CKO) mice were short with thin skeletal elements and fused joints. POR deletion occurred earlier in forelimbs than in hind limbs, leading additionally to soft tissue syndactyly and loss of wrist elements and phalanges due to changes in growth, cell death, and skeletal segmentation. Transcriptional analysis of E12.5 mouse forelimb buds demonstrated the expression of P450s involved in retinoic acid, cholesterol, and arachidonic acid metabolism. Biochemical analysis of CKO limbs confirmed retinoic acid excess. In CKO limbs, expression of genes throughout the whole cholesterol biosynthetic pathway was upregulated, and cholesterol deficiency can explain most aspects of the phenotype. Thus, cellular POR-dependent cholesterol synthesis is essential during limb and skeletal development. Modulation of P450 activity could contribute to susceptibility of the embryo and developing organs to teratogenesis.

Prospective tests on biological models of acupuncture

The biological effects of acupuncture include the regulation of a variety of neurohumoral factors and growth control factors. In science, models or hypotheses with confirmed predictions are considered more convincing than models solely based on retrospective explanations. Literature review showed that two biological models of acupuncture have been prospectively tested with independently confirmed predictions: The neurophysiology model on the long-term effects of acupuncture emphasizes the trophic and anti-inflammatory effects of acupuncture. Its prediction on the peripheral effect of endorphin in acupuncture has been confirmed. The growth control model encompasses the neurophysiology model and suggests that a macroscopic growth control system originates from a network of organizers in embryogenesis. The activity of the growth control system is important in the formation, maintenance and regulation of all the physiological systems. Several phenomena of acupuncture such as the distribution of auricular acupuncture points, the long-term effects of acupuncture and the effect of multimodal non-specific stimulation at acupuncture points are consistent with the growth control model. The following predictions of the growth control model have been independently confirmed by research results in both acupuncture and conventional biomedical sciences: (i) Acupuncture has extensive growth control effects. (ii) Singular point and separatrix exist in morphogenesis. (iii) Organizers have high electric conductance, high current density and high density of gap junctions. (iv) A high density of gap junctions is distributed as separatrices or boundaries at body surface after early embryogenesis. (v) Many acupuncture points are located at transition points or boundaries between different body domains or muscles, coinciding with the connective tissue planes. (vi) Some morphogens and organizers continue to function after embryogenesis. Current acupuncture research suggests a convergence of the neurophysiology model, the connective tissue model and the growth control model. The growth control model of acupuncture set the first example of a biological model in integrative medicine with significant prediction power.

Retinoic acid induces prostatic bud formation

Formation of prostatic buds from the urogenital sinus (UGS) to initiate prostate development requires localized action of several morphogenetic factors. This report reveals all-trans-retinoic acid (RA) to be a powerful inducer of mouse prostatic budding that is associated with reciprocal changes in expression of two regulators of budding: sonic hedgehog (Shh) and bone morphogenetic protein 4 (Bmp4). Localization of retinoid signaling and expression of RA synthesis, metabolism, and receptor genes in the UGS on embryonic days 14.5-17.5 implicate RA in the mechanism of bud initiation. In UGS organ culture, RA increased prostatic budding, increased Shh expression, and decreased Bmp4. Prostatic budding was stimulated in the absence of RA by recombinant SHH, by blocking BMP4 signaling with NOGGIN, or by combined treatment with SHH and NOGGIN in UGS organ culture media. These observations suggest that reciprocal changes in hedgehog and BMP signaling by RA may regulate bud initiation.

Quantitative profiling of endogenous retinoic acid in vivo and in vitro by tandem mass spectrometry

We report an improved tandem mass spectrometric assay for retinoic acid (RA) applicable to in vitro and in vivo biological samples. This liquid chromatography tandem mass spectrometric (LC/MS/MS) assay for direct RA quantification is the most sensitive to date, with a 62.5 attomol lower limit of detection and a linear range spanning greater than 4 orders of magnitude (from 250 attomol to 10 pmol). This assay resolves all-trans-RA (atRA) from its endogenous geometric isomers, is applicable to samples of limited size (10-20 mg of tissue), and functions with complex biological matrixes. Coefficients of variation are as follows: instrumental, < or =2.6%; intraday, 5.2% +/- 0.7%; interday, 6.7% +/- 0.9%. In vitro capabilities are demonstrated by quantification of endogenous RA and RA production (from retinol) in primary cultured astrocytes. Quantification of endogenous atRA and its geometric isomers in 129SV mouse serum and tissues (liver, kidney, adipose, muscle, spleen, testis, and brain) reveals in vivo utility of the assay. The ability to discriminate spatial concentrations of RA in vivo is illustrated with C57BL/6 mouse brain loci (hippocampus, cortex, olfactory bulb, thalamus, cerebellum, and striatum), as well as with Lewis rat proximal/distal mammary gland regions during various morphological stages: virgin, early pregnancy (e7), late pregnancy (e20), lactating (day 4), involuting day 1, and involuting day 11. This assay provides the sensitivity necessary for direct, endogenous RA quantification necessary to elucidate RA function, e.g., in neurogenesis, morphogenesis, and the contribution of altered RA homeostasis to diseases, such as Alzheimer's disease, type 2 diabetes, obesity, and cancer.

Localized rbp4 expression in the yolk syncytial layer plays a role in yolk cell extension and early liver development

BACKGROUND

The number of genes characterized in liver development is steadily increasing, but the origin of liver precursor cells and the molecular control of liver formation remain poorly understood. Existing theories about formation of zebrafish visceral organs emphasize either their budding from the endodermal rod or formation of independent anlage followed by their later fusion, but none of these is completely satisfactory in explaining liver organogenesis in zebrafish.

RESULTS

Expression of a gene encoding the retinol binding protein 4 (Rbp4) was analyzed in zebrafish. rbp4, which is expressed mainly in the liver in adults, was shown to be expressed in the yolk syncytial layer (YSL) during early embryogenesis. At 12-16 hpf rbp4 expression was restricted to the ventro-lateral YSL and later expanded to cover the posterior YSL. We demonstrated that rbp4 expression was negatively regulated by Nodal and Hedgehog (Hh) signalling and positively controlled by retinoic acid (RA). Knockdown of Rbp4 in the YSL resulted in shortened yolk extension as well as the formation of two liver buds, which could be due to impaired migration of liver progenitor cells. rbp4 appears also to regulate the extracellular matrix protein Fibronectin1 (Fn1) specifically in the ventro-lateral yolk, indicating a role of Fn1 in liver progenitor migration. Since exocrine pancreas, endocrine pancreas, intestine and heart developed normally in Rbp4 morphants, we suggest that rbp4 expression in the YSL is required only for liver development.

CONCLUSION

The characteristic expression pattern of rbp4 suggests that the YSL is patterned despite its syncytial nature. YSL-expressed Rbp4 plays a role in formation of both yolk extension and liver bud, the latter may also require migration of liver progenitor cells.