Immunohistochemical Localization of Peroxisomal Enzymes During Rat Embryonic Development

Peroxisomes during postnatal development of mouse endocrine and exocrine pancreas display cell-type- and stage-specific protein composition

Peroxisomal dysfunction unhinges cellular metabolism by causing the accumulation of toxic metabolic intermediates (e.g. reactive oxygen species, very -chain fatty acids, phytanic acid or eicosanoids) and the depletion of important lipid products (e.g. plasmalogens, polyunsaturated fatty acids), leading to various proinflammatory and devastating pathophysiological conditions like metabolic syndrome and age-related diseases including diabetes. Because the peroxisomal antioxidative marker enzyme catalase is low abundant in Langerhans islet cells, peroxisomes were considered scarcely present in the endocrine pancreas. Recently, studies demonstrated that the peroxisomal metabolism is relevant for pancreatic cell functionality. During the postnatal period, significant changes occur in the cell structure and the metabolism to trigger the final maturation of the pancreas, including cell proliferation, regulation of energy metabolism, and activation of signalling pathways. Our aim in this study was to (i) morphometrically analyse the density of peroxisomes in mouse endocrine versus exocrine pancreas and (ii) investigate how the distribution and the abundance of peroxisomal proteins involved in biogenesis, antioxidative defence and fatty acid metabolism change during pancreatic maturation in the postnatal period. Our results prove that endocrine and exocrine pancreatic cells contain high amounts of peroxisomes with heterogeneous protein content indicating that distinct endocrine and exocrine cell types require a specific set of peroxisomal proteins depending on their individual physiological functions. We further show that significant postnatal changes occur in the peroxisomal compartment of different pancreatic cells that are most probably relevant for the metabolic maturation and differentiation of the pancreas during the development from birth to adulthood.

Direct Effects of Mifepristone on Mice Embryogenesis: An In Vitro Evaluation by Single-Embryo RNA Sequencing Analysis

The clinical use of mifepristone for medical abortions has been established in 1987 in France and since 2000 in the United States. Mifepristone has a limited medical period that lasts <9 weeks of gestation, and the incidence of mifepristone treatment failure increases with gestation time. Mifepristone functions as an antagonist for progesterone and glucocorticoid receptors. Studies have confirmed that mifepristone treatments can directly contribute to endometrium disability by interfering with the endometrial receptivity of the embryo, thus causing decidual endometrial degeneration. However, whether mifepristone efficacy directly affects embryo survival and growth is still an open question. Some women choose to continue their pregnancy after mifepristone treatment fails, and some women express regret and seek medically unapproved mifepristone antagonization with high doses of progesterone. These unapproved treatments raise the potential risk of embryonic fatality and developmental anomalies. Accordingly, in the present study, we collected mouse blastocysts ex vivo and treated implanted blastocysts with mifepristone for 24 h. The embryos were further cultured to day 8 in vitro to finish their growth in the early somite stage, and the embryos were then collected for RNA sequencing (control n = 3, mifepristone n = 3). When we performed a gene set enrichment analysis, our data indicated that mifepristone treatment considerably altered the cellular pathways of embryos in terms of viability, proliferation, and development. The data indicated that mifepristone was involved in hallmark gene sets of protein secretion, mTORC1, fatty acid metabolism, IL-2-STAT5 signaling, adipogenesis, peroxisome, glycolysis, E2F targets, and heme metabolism. The data further revealed that mifepristone interfered with normal embryonic development. In sum, our data suggest that continuing a pregnancy after mifepristone treatment fails is inappropriate and infeasible. The results of our study reveal a high risk of fetus fatality and developmental problems when pregnancies are continued after mifepristone treatment fails.

Lipidomics of human umbilical cord serum: identification of unique sterol sulfates

Aim:

There are currently limited lipidomics data for human umbilical cord blood. Therefore, the lipidomes of cord sera from six newborns and sera from six nonpregnant females were compared.

Materials & methods:

Sera lipidomics analyses were conducted using a high-resolution mass spectrometry analytical platform.

Results:

Cord serum contained a diverse array of glycerophospholipids, albeit generally at lower concentrations than monitored in adult serum. The unexpected observations were that cord serum contained several neurosteroid sulfates and bile acid sulfates that were not detectable in adult serum.

Conclusion:

Our data are the first to demonstrate that cord serum contains bile acid sulfates that are synthesized early in the hydroxylase, neutral and acidic pathways of primary bile acid biosynthesis and support previous publications of cord blood perfluoralkyl toxins in newborns.

Umbilical cord blood offers the potential to increase our understanding of fetal development during pregnancy and during development after delivery. Our studies of complex sterols in umbilical cord blood (bile acid sulfates) suggest that with further studies these may be useful biomarkers of abnormal fetal liver development.

Peroxisomes in Different Skeletal Cell Types during Intramembranous and Endochondral Ossification and Their Regulation during Osteoblast Differentiation by Distinct Peroxisome Proliferator-Activated Receptors

Ossification defects leading to craniofacial dysmorphism or rhizomelia are typical phenotypes in patients and corresponding knockout mouse models with distinct peroxisomal disorders. Despite these obvious skeletal pathologies, to date no careful analysis exists on the distribution and function of peroxisomes in skeletal tissues and their alterations during ossification. Therefore, we analyzed the peroxisomal compartment in different cell types of mouse cartilage and bone as well as in primary cultures of calvarial osteoblasts. The peroxisome number and metabolism strongly increased in chondrocytes during endochondral ossification from the reserve to the hypertrophic zone, whereas in bone, metabolically active osteoblasts contained a higher numerical abundance of this organelle than osteocytes. The high abundance of peroxisomes in these skeletal cell types is reflected by high levels of Pex11β gene expression. During culture, calvarial pre-osteoblasts differentiated into secretory osteoblasts accompanied by peroxisome proliferation and increased levels of peroxisomal genes and proteins. Since many peroxisomal genes contain a PPAR-responsive element, we analyzed the gene expression of PPARɑ/ß/ɣ in calvarial osteoblasts and MC3T3-E1 cells, revealing higher levels for PPARß than for PPARɑ and PPARɣ. Treatment with different PPAR agonists and antagonists not only changed the peroxisomal compartment and associated gene expression, but also induced complex alterations of the gene expression patterns of the other PPAR family members. Studies in M3CT3-E1 cells showed that the PPARß agonist GW0742 activated the PPRE-mediated luciferase expression and up-regulated peroxisomal gene transcription (Pex11, Pex13, Pex14, Acox1 and Cat), whereas the PPARß antagonist GSK0660 led to repression of the PPRE and a decrease of the corresponding mRNA levels. In the same way, treatment of calvarial osteoblasts with GW0742 increased in peroxisome number and related gene expression and accelerated osteoblast differentiation. Taken together, our results suggest that PPARß regulates the numerical abundance and metabolic function of peroxisomes via Pex11ß in parallel to osteoblast differentiation.

Lithium modulates the production of peripheral and cerebral cytokines in an animal model of mania induced by dextroamphetamine

OBJECTIVES

Several recent studies have suggested that the physiopathology of bipolar disorder (BD) is related to immune system alterations and inflammation. Lithium (Li) is a mood stabilizer that is considered the first-line treatment for this mood disorder. The goal of the present study was to investigate the effects of Li administration on behavior and cytokine levels [interleukin (IL)-1β, IL-4, IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α)] in the periphery and brains of rats subjected to an animal model of mania induced by amphetamine (d-AMPH).

METHODS

Male Wistar rats were treated with d-AMPH or saline (Sal) for 14 days; on Day 8 of treatment, the rats were administered Li or Sal for the final seven days. Cytokine (IL-1β, IL-4, IL-6, IL-10, and TNF-α) levels were evaluated in the cerebrospinal fluid (CSF), serum, frontal cortex, striatum, and hippocampus.

RESULTS

The present study showed that d-AMPH induced hyperactivity in rats (p < 0.001), and Li treatment reversed this behavioral alteration (p < 0.001). In addition, d-AMPH increased the levels of IL-4, IL-6, IL-10, and TNF-α in the frontal cortex (p < 0.001), striatum (p < 0.001), and serum (p < 0.001), and treatment with Li reversed these cytokine alterations (p < 0.001).

CONCLUSIONS

Li modulates peripheral and cerebral cytokine production in an animal model of mania induced by d-AMPH, suggesting that its action on the inflammatory system may contribute to its therapeutic efficacy.

Expression of peroxiredoxins and thioredoxins in the mouse spinal cord during embryonic development

Reactive oxygen and nitrogen species (ROS/RNS) are natural byproducts of cellular metabolism. Although these molecules are deleterious at high concentrations, moderate levels of ROS/RNS are essential for normal cell function and take part in numerous cellular processes. The regulation of ROS/RNS is largely attended by peroxiredoxins (Prdxs) and their main reductants, thioredoxins (Trxs). Through their oxidoreductase activities, the members of the Trx/Prdx system can also affect certain cellular processes, notably many implicated in central nervous system (CNS) development. Although several studies have investigated the expression of Prdxs and Trxs in mouse, rat, and human adult CNS, few data are available concerning embryonic stages. In this work, we use immunofluorescence analyses to study the distribution of these enzymes during prenatal mouse spinal cord development. Our results highlight several patterns that contrast with available data for the adult. Indeed, Prdx1, Prdx4, and Prdx6, which are expressed in glial cells in the adult CNS, present clear neuronal localization in mouse spinal cord during embryonic development. Additionally, Prdx1, Prdx2, and to a lesser extent Prdx4, Prdx6, and Trx1 are localized mainly in the nucleus of neural cells. Finally, we identified a consistent, intense expression of all Prdxs and Trxs in groups of cells located in ventral regions of the spinal cord that express motor neuronal markers. These striking expression patterns suggest novel functions of these enzymes at these stages and offer clues to the role of the Trx/Prdx system during embryonic development of the spinal cord.

Developmental changes in the transcriptome of the rat choroid plexus in relation to neuroprotection

Background

The choroid plexuses are the interface between the blood and the cerebrospinal fluid (CSF) contained within the ventricular spaces of the central nervous system. The tight junctions linking adjacent cells of the choroidal epithelium create a physical barrier to paracellular movement of molecules. Multispecific efflux transporters as well as drug-metabolizing and antioxidant enzymes functioning in these cells contribute to a metabolic barrier. These barrier properties reflect a neuroprotective function of the choroid plexus. The choroid plexuses develop early during embryogenesis and provide pivotal control of the internal environment throughout development when the brain is especially vulnerable to toxic insults. Perinatal injuries like hypoxia and trauma, and exposure to drugs or toxic xenobiotics can have serious consequences on neurogenesis and long-term development. The present study describes the developmental expression pattern of genes involved in the neuroprotective functions of the blood–CSF barrier.

Methods

The transcriptome of rat lateral ventricular choroid plexuses isolated from fifteen-day-old embryos, nineteen-day old fetuses, two-day old pups, and adults was analyzed by a combination of Affymetrix microarrays, Illumina RNA-Sequencing, and quantitative RT-PCR.

Results

Genes coding for proteins involved in junction formation are expressed early during development. Overall perinatal expression levels of genes involved in drug metabolism and antioxidant mechanisms are similar to, or higher than levels measured in adults. A similar developmental pattern was observed for multispecific efflux transporter genes of the Abc and Slc superfamilies. Expression of all these genes was more variable in choroid plexus from fifteen-day-old embryos. A large panel of transcription factors involved in the xenobiotic- or cell stress-mediated induction of detoxifying enzymes and transporters is also expressed throughout development.

Conclusions

This transcriptomic analysis suggests relatively well–established neuroprotective mechanisms at the blood-CSF barrier throughout development of the rat. The expression of many transcription factors early in development raises the possibility of additional protection for the vulnerable developing brain, should the fetus or newborn be exposed to drugs or other xenobiotics.

Tight junctions in brain barriers during central nervous system inflammation

Homeostasis within the central nervous system (CNS) is a prerequisite to elicit proper neuronal function. The CNS is tightly sealed from the changeable milieu of the blood stream by the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier (BCSFB). Whereas the BBB is established by specialized endothelial cells of CNS microvessels, the BCSFB is formed by the epithelial cells of the choroid plexus. Both constitute physical barriers by a complex network of tight junctions (TJs) between adjacent cells. During many CNS inflammatory disorders, such as multiple sclerosis, human immunodeficiency virus infection, or Alzheimer's disease, production of pro-inflammatory cytokines, matrix metalloproteases, and reactive oxygen species are responsible for alterations of CNS barriers. Barrier dysfunction can contribute to neurological disorders in a passive way by vascular leakage of blood-borne molecules into the CNS and in an active way by guiding the migration of inflammatory cells into the CNS. Both ways may directly be linked to alterations in molecular composition, function, and dynamics of the TJ proteins. This review summarizes current knowledge on the cellular and molecular aspects of the functional and dysfunctional TJ complexes at the BBB and the BCSFB, with a particular emphasis on CNS inflammation and the role of reactive oxygen species.

PEX13 deficiency in mouse brain as a model of Zellweger syndrome: abnormal cerebellum formation, reactive gliosis and oxidative stress

Delayed cerebellar development is a hallmark of Zellweger syndrome (ZS), a severe neonatal neurodegenerative disorder. ZS is caused by mutations in PEX genes, such as PEX13, which encodes a protein required for import of proteins into the peroxisome. The molecular basis of ZS pathogenesis is not known. We have created a conditional mouse mutant with brain-restricted deficiency of PEX13 that exhibits cerebellar morphological defects. PEX13 brain mutants survive into the postnatal period, with the majority dying by 35 days, and with survival inversely related to litter size and weaning body weight. The impact on peroxisomal metabolism in the mutant brain is mixed: plasmalogen content is reduced, but very-long-chain fatty acids are normal. PEX13 brain mutants exhibit defects in reflex and motor development that correlate with impaired cerebellar fissure and cortical layer formation, granule cell migration and Purkinje cell layer development. Astrogliosis and microgliosis are prominent features of the mutant cerebellum. At the molecular level, cultured cerebellar neurons from E19 PEX13-null mice exhibit elevated levels of reactive oxygen species and mitochondrial superoxide dismutase-2 (MnSOD), and show enhanced apoptosis together with mitochondrial dysfunction. PEX13 brain mutants show increased levels of MnSOD in cerebellum. Our findings suggest that PEX13 deficiency leads to mitochondria-mediated oxidative stress, neuronal cell death and impairment of cerebellar development. Thus, PEX13-deficient mice provide a valuable animal model for investigating the molecular basis and treatment of ZS cerebellar pathology.

Characterization and regulation of monocarboxylate cotransporters Slc16a7 and Slc16a3 in preimplantation mouse embryos

Concurrent with compaction, preimplantation mouse embryos switch from the high pyruvate consumption that prevailed during cleavage stages to glucose consumption against a constant background of pyruvate uptake. However, zygotes exposed to and subsequently deprived of glucose can form blastocysts by increasing pyruvate uptake. This metabolic switch requires cleavage-stage exposure to glucose and is one aspect of metabolic differentiation that normally occurs in vivo. Monocarboxylates, such as pyruvate and lactate, are transported across membranes via the SLC16 family of H(+)-monocarboxylate cotransporter (MCT) proteins. Thus, the increase in pyruvate uptake in embryos developing without glucose must involve changes in activity and localization of MCT. In mouse embryos, continued expression of Slc16a1 (MCT1) requires glucose supply. Messenger RNA for Slc17a7 (MCT2) and Slc16a3 (MCT4) has been detected in mouse preimplantation embryos; however, protein function, localization, and regulation of expression at the basis of these net pyruvate uptake changes remain unclear. The expression and localization of SLC16A7 and SLC16A3 have therefore been examined to clarify their respective roles in embryos derived from the reproductive tract and cultured under varied conditions. SLC16A3 appears localized to the plasma membrane until the morula stage and also maintains a nuclear distribution throughout preimplantation development. However, continued Slc16a3 mRNA expression is dependent on prior exposure to glucose. SLC16A7 localizes to apical cortical regions with punctate, vesicular expression throughout blastomeres, partially colocalizing in peroxisomes with peroxisomal catalase (CAT). In contrast to SLC16A3 and SLC16A1, SLC16A7 and CAT demonstrate upregulation in the absence of glucose. These striking differences between the two isoforms in expression localization and regulation suggest unique roles for each in monocarboxylate transport and pH regulation during preimplantation development, and implicate peroxisomal SLC16A7 as an important redox regulator in the absence of glucose.

Differential expression of peroxisomal matrix and membrane proteins during postnatal development of mouse brain

In peroxisomal biogenesis disorders, serious neurological abnormalities can be observed in the patients and the respective knockout mouse models. As a prerequisite for a better understanding of the relationship between the absence of peroxisomes and the observed neuropathology, knowledge of the regional and cell-type specific distribution of peroxisomal proteins in mouse brain is necessary. Therefore, we investigated the expression of distinct peroxins, peroxisomal membrane and matrix proteins (e.g. Pex5p, Pex14p, Pex13p, PMP70, catalase, peroxisomal thiolase, Acox1, "SKL"-PTS1 proteins) by indirect immunofluorescence 1) in primary cultures of the medial neocortex, hippocampus, and cerebellum of newborn mice and 2) in paraffin sections of mouse brain of different ages (newborn-adult). Quantitative analysis revealed a comparable abundance (number/microm(2)) of peroxisomes in cultured neurons and astrocytes of all three brain regions. In contrast, catalase immunoreactivity was higher in cultured astrocytes than in neurons. In mouse brain tissue, the abundance of peroxisomes decreased by half during postnatal development, also exhibiting prominent differences between distinct brain regions and cell types. Catalase protein levels in neuronal peroxisomes, however, decreased much more strongly in the neocortex, CA1-3 areas of the hippocampus, dentate gyrus, cerebellar nuclei, and cerebellar cortex but remained high in Bergmann glia and other astrocytes, epithelial cells of the choroid plexus, and ependyma. Similar age-dependent changes were found for thiolase and Acox1 protein levels. Developmental changes were confirmed by Western blot analysis using enriched peroxisomal and cytosolic fractions of the brain tissue as well as by measurement of catalase activity.

Conserved expression of alternative splicing variants of peroxisomal acyl-CoA oxidase 1 in vertebrates and developmental and nutritional regulation in fish

The acyl-coenzyme A oxidase 1 (ACOX1) catalyzes the first, rate-limiting step in peroxisomal beta-oxidation of medium to very long straight-chain fatty acids. Zebrafish (Danio rerio) acox1 was characterized and compared with homologs from other sequenced genomes, revealing a remarkable conservation of structure in the vertebrate lineage. Strictly conserved regions of the deduced proteins included acyl-CoA oxidase and FAD binding domains, as well as a COOH-terminal peroxisomal targeting signal. Whole mount in situ hybridization showed that zebrafish acox1 transcripts were diffusely distributed in early-stage embryonic cells, then discreetly expressed in the brain and widely present in the liver and intestine at later stages. An evolutionarily conserved alternative splicing of the corresponding acox1 primary transcript was identified in teleosts and tetrapods including mammals, giving rise, after exon skipping, to two splice variants, ACOX1-3I and ACOX1-3II. Real-time quantitative RT-PCR on zebrafish adult tissues indicated high levels of both variants in the liver, anterior intestine, and to a lesser extent, in the brain. However, the ACOX1-3II transcript variant was expressed seven times more in zebrafish brain than the ACOX1-3I variant. These data suggest a tissue-specific modulation of ACOX1 activity by exchanging exon 3 duplicated isoforms containing amino acid sequences that are potentially implicated in fatty acyl chain specificity. In addition, a significant pretranslational up-regulation of zebrafish and rainbow trout (Oncorhynchus mykiss) acox1 expression was observed in the anterior intestine after feeding. Taken together, these data indicate that ACOX1 alternative splicing isoforms play a key conserved role in the vertebrate fatty acid metabolism.

Tissue expression of the mulibrey nanism-associated Trim37 protein in embryonic and adult mouse tissues

Mutations in the TRIM37 gene underlie mulibrey nanism (muscle-liver-brain-eye nanism), a rare monogenic developmental disorder characterized by severe growth failure, characteristic dysmorphic features, cardiopathy, failure of sexual maturation, and metabolic syndrome. The TRIM37 protein, a member of the tripartite motif subfamily of RING finger proteins, is highly conserved between human and mouse. High evolutionary conservation is seen also at the gene level. We here show that the mouse Trim37 gene presents several alternative splice variants, including a testis-specific transcript with an additional 3' exon. By Northern blot analysis the highest level of Trim37 mRNA was detected in testis and brain. In embryonic tissues, the Trim37 protein was detected in epithelia, including ducts of the developing pancreas, epithelium of the midgut and nasal epithelium. In adult mouse tissues, Trim37 immunoreactivity was detected in the central and peripheral nervous systems, including enteric ganglia, retina, and the adrenal medulla. Moreover, specific cellular populations in the adenohypophysis, pancreatic islets, intestine and gonads showed intense Trim37 staining. Both nuclear and granular cytoplasmic staining patterns were observed. These findings are in agreement with the clinical manifestations of mulibrey nanism and provide a basis for the future analysis of Trim37 knock-out mice.