Zac1 is up-regulated in neural cells of the limbic system of mouse brain following seizures that provoke strong cell activation

The benefit of combinations of oximes for the ability of antidotal treatment to counteract sarin-induced brain damage in rats

Background

The aim of our study was to compare the ability of two combinations of oximes (HI-6 + trimedoxime and HI-6 + K203) with atropine to counteract acute sarin-induced brain damage with the efficacy of antidotal treatment involving single oxime (HI-6) and atropin using in vivo methods.

Methods

Brain damage and neuroprotective effects of antidotal treatment were evaluated in rats poisoned with sarin at a sublethal dose (108 μg/kg i.m.; 90% LD₅₀) using histopathological, Fluoro-Jade B and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis 24 h after sarin administration.

Results

Both combinations of oximes reduce the number of rats that died before the end of experiment compared to non-treated sarin poisoning and sarin poisoning treated with HI-6 and atropine. In the case of treatment of sarin poisoning with HI-6 in combination with K203, all rats survived till the end of experiment. HI-6 with atropine was able to reduce sarin-induced brain damage, however, both combinations were slightly more effective.

Conclusions

The oxime HI-6 in combination with K203 and atropine seems to be the most effective. Thus, both tested oxime combinations bring a small benefit in elimination of acute sarin-induced brain damage compared to single oxime antidotal therapy.

Hippocampal Transcriptomic Profiles: Subfield Vulnerability to Age and Cognitive Impairment

The current study employed next-generation RNA sequencing to examine gene expression differences related to brain aging, cognitive decline, and hippocampal subfields. Young and aged rats were trained on a spatial episodic memory task. Hippocampal regions CA1, CA3, and the dentate gyrus were isolated. Poly-A mRNA was examined using two different sequencing platforms, Illumina, and Ion Proton. The Illumina platform was used to generate seed lists of genes that were statistically differentially expressed across regions, ages, or in association with cognitive function. The gene lists were then retested using the data from the Ion Proton platform. The results indicate hippocampal subfield differences in gene expression and point to regional differences in vulnerability to aging. Aging was associated with increased expression of immune response-related genes, particularly in the dentate gyrus. For the memory task, impaired performance of aged animals was linked to the regulation of Ca²⁺ and synaptic function in region CA1. Finally, we provide a transcriptomic characterization of the three subfields regardless of age or cognitive status, highlighting and confirming a correspondence between cytoarchitectural boundaries and molecular profiling.

Down-regulation of Zac1 gene expression in rat white adipose tissue by androgens

ZAC1 is a zinc-finger protein transcription factor, a transcriptional cofactor for nuclear receptors, and a co-activator of nuclear receptors, which interacts with multiple signaling pathways affecting apoptosis, cell cycle arrest, and metabolism. Some data suggest that ZAC1 regulates the expression of genes associated with function of adipose tissue. Since there is no information about the levels of Zac1 gene expression in white adipose tissue (WAT), and the expression of several genes associated with metabolic function of WAT is significantly lower in male than female animals, we have examined: (a) the relative ZAC1 mRNA levels in some organs/tissues, including three main depots of WAT, in 3-month-old male rats; (b) the relative ZAC1 mRNA levels in WAT of male and female rats; (c) the effect of orchidectomy and orchidectomy with concomitant testosterone treatment on ZAC1 mRNA and protein levels; (d) the effect of ovariectomy and ovariectomy with concomitant 17β-estradiol treatment on ZAC1 mRNA levels; (e) the effect of dihydrotestosterone on ZAC1 mRNA levels in isolated adipocytes. Our results indicate that: (a) ZAC1 mRNA levels are relatively high in WAT in comparison with other organs/tissues; (b) ZAC1 mRNA levels in subcutaneous WAT are approximately 2-fold lower than in epididymal and retroperitoneal adipose tissue; (c) ZAC1 mRNA levels in WAT of adult female rats are approximately 2-fold higher than in male rats; (d) testosterone is inversely related to ZAC1 mRNA and protein levels in WAT of male rats; and (e) dihydrotestosterone decreases the ZAC1 mRNA levels in adipocytes in dose dependent manner. In conclusion, Zac1 gene is highly expressed in white adipose tissue of adult rats. Androgens could play an important role in down-regulation of the ZAC1 mRNA and protein levels in rats.

From omics to drug metabolism and high content screen of natural product in zebrafish: a new model for discovery of neuroactive compound

The zebrafish (Danio rerio) has recently become a common model in the fields of genetics, environmental science, toxicology, and especially drug screening. Zebrafish has emerged as a biomedically relevant model for in vivo high content drug screening and the simultaneous determination of multiple efficacy parameters, including behaviour, selectivity, and toxicity in the content of the whole organism. A zebrafish behavioural assay has been demonstrated as a novel, rapid, and high-throughput approach to the discovery of neuroactive, psychoactive, and memory-modulating compounds. Recent studies found a functional similarity of drug metabolism systems in zebrafish and mammals, providing a clue with why some compounds are active in zebrafish in vivo but not in vitro, as well as providing grounds for the rationales supporting the use of a zebrafish screen to identify prodrugs. Here, we discuss the advantages of the zebrafish model for evaluating drug metabolism and the mode of pharmacological action with the emerging omics approaches. Why this model is suitable for identifying lead compounds from natural products for therapy of disorders with multifactorial etiopathogenesis and imbalance of angiogenesis, such as Parkinson's disease, epilepsy, cardiotoxicity, cerebral hemorrhage, dyslipidemia, and hyperlipidemia, is addressed.

Dietary supplementation with acetyl-l-carnitine in seizure treatment of pentylenetetrazole kindled mice

In spite of the availability of new antiepileptic drugs a considerable number of epilepsy patients still have pharmacoresistant seizures, and thus there is a need for novel approaches. Acetyl-l-carnitine (ALCAR), which delivers acetyl units to mitochondria for acetyl-CoA production, has been shown to improve brain energy homeostasis and protects against various neurotoxic insults. To our knowledge, this is the first study of ALCAR's effect on metabolism in pentylenetetrazole (PTZ) kindled mice. ALCAR or the commonly used antiepileptic drug valproate, was added to the drinking water of mice for 25days, and animals were injected with PTZ or saline three times a week during the last 21 days. In order to investigate ALCAR's effects on glucose metabolism, mice were injected with [1-(13)C]glucose 15 min prior to microwave fixation. Brain extracts from cortex and the hippocampal formation (HF) were studied using (1)H and (13)C NMR spectroscopy and HPLC. PTZ kindling caused glucose hypometabolism, evidenced by a reduction in both glycolysis and TCA cycle turnover in both brain regions investigated. Glutamatergic and GABAergic neurons were affected in cortex and HF, but the amount of glutamate was only reduced in HF. Slight astrocytic involvement could be detected in the cortex. Interestingly, the dopamine content was increased in the HF. ALCAR attenuated the PTZ induced reduction in [3-(13)C]alanine and the increase in dopamine in the HF. However, TCA cycle metabolism was not different from that seen in PTZ kindled animals. In conclusion, even though ALCAR did not delay the kindling process, it did show some promising ameliorative effects, worthy of further investigation.

Glutamine synthetase becomes nitrated and its activity is reduced during repetitive seizure activity in the pentylentetrazole model of epilepsy

PURPOSE

The astrocyte-specific glutamine synthetase (GS) plays a key role in glutamate recycling and Gamma-aminobutyric acid (GABA) metabolism. Changes in the expression or activity of GS have been proposed to contribute to epileptogenesis. The mechanisms or how and where GS may contribute to epilepsy is still a matter of discussion. Here we asked the question whether brain regions, which show an astrocytic stress response respond with alterations of GS.

METHODS

Biochemical and histological alterations of GS, HSP-27, and GFAP were studied after pentylenetetrazole-induced repetitive epileptic seizures (PIRS) in rats using a topographical quantification of the GS-immunoreactivity (GSIR) in relation to the focal heat shock response (HSR). Saline-treated rats served as controls and rats treated by the GS-inhibitor, L-methionine-sulfoximine (MSO) served as a positive control.

RESULTS

No changes in the amount of GSIR and GS-protein occurred during PIRS. A significant reduction of GSIR was observed by histochemistry (in situ) and in native (nonheated) protein extracts of MSO-treated rats. In rats affected by PIRS, GS-activity showed a significant, region-specific reduction in association with a nitration of the enzyme.

DISCUSSION

These results show that neither PIRS nor GS-inhibition reduced the amount of GS protein, but that MSO interferes with antibody binding to native GS. PIRS resulted in a focal increase of astrocytic stress response, whereas MSO caused a widespread, homogeneous astrocytic HSR independent from quantitative changes of GS content. In rats with PIRS the regions showing a strong glial HSR, respond with reduced GS-activity and GS-nitration, which all together are clear indicators of a nitrosative stress response.

Preferential loss of the nonimprinted allele for the ZAC1 tumor suppressor gene in human capillary hemangioblastoma

Capillary hemangioblastomas (CHBs) are vascular, usually benign, tumors of the CNS, occurring either as a component of familial von Hippel-Lindau (VHL) disease or as a sporadic entity. Both familial and sporadic forms of VHL-associated tumors involve inactivation of the VHL gene; for CHB, 20% to 50% of sporadic cases are affected. However, other molecular alterations involved in the pathogenesis of sporadic CHBs, which represent up to 70% of CHBs, remain largely unknown. We previously identified a minimal deleted area at 6q23-24 in CHB, and the present study focused on the ZAC1 gene (6q24-25). ZAC1 is a maternally imprinted tumor suppressor gene with antiproliferative properties. We investigated loss of heterozygosity (LOH), promoter methylation, and expression status of ZAC1 in mainly sporadic cases of CHB. Our LOH analysis with 6 microsatellite markers spanning the ZAC1 gene region revealed a high frequency (6 of 10, 60%) of LOH. The promoter methylation analysis detected predominance of the methylated ZAC1 sequence in the majority (9 of 10, 90%) of the tumors. Immunohistochemistry exhibited a strongly reduced expression of ZAC1 in stromal cells of all CHBs studied. Collectively, our current results indicate that the absence of the unmethylated ZAC1 sequence was highly concurrent with ZAC1 region LOH or 6q loss and with lack of ZAC1 expression, suggesting preferential loss of the nonimprinted, expressed ZAC1 allele in CHB. This novel finding highlights the importance of ZAC1 in development of CHB, particularly in non-VHL-associated cases.

LOT1 (ZAC1/PLAGL1) and its family members: mechanisms and functions

Lost-on-transformation 1 (LOT1) (PLAGL1/ZAC1) is a member of the novel subfamily of zinc-finger transcription factors, designated as PLAG family. The other members in this group include PLAG1 and PLAGL2, which share high homology with each other and with LOT1, particularly in their zinc-finger amino-terminal region. They are structurally similar but functionally different. For example, the LOT1 gene encodes a growth suppressor protein and is localized on human chromosome 6q24-25, a chromosomal region that is frequently deleted in many types of human cancers. The gene is maternally imprinted and is linked to developmental disorders such as growth retardation and transient neonatal diabetes mellitus (TNDM). LOT1 is a target of growth factor signaling pathway(s) and silenced by epigenetic mechanisms, as well as by the loss of heterozygosity in different tumor tissues. PLAG1 is a protooncogene that is localized on chromosome 8q12 and was found to be a target of several types of chromosomal rearrangement including the one identified in pleomorphic adenomas of the salivary gland. Since the discovery of the PLAG family members in 1997, much has been learned about their structure and function, as are summarized in this review. While the available data suggest that these proteins may play important roles in regulating normal physiological functions in the mammals, a great deal more about their signaling pathway(s), potential role in the complex pathologies such as cancer and developmental disorders, and functional relationship between different family members and splice variants still remains to be uncovered.

Transcriptional profiling of depolarization-dependent phenotypic alterations in primary cultures of developing granule neurons

Rat cerebellar granule neurons cultured in medium supplemented with elevated KCl are extensively used as a model to examine the coupling between neural activity and Ca(2+)-dependent gene expression. Elevated (25 mM) KCl is believed to mimic endogenous neural activity because it promotes depolarization and Ca(+2)-dependent survival and some aspects of maturation. By comparison, at least half of the granule neurons grown in standard medium containing 5 mM KCl undergo apoptosis beginning approximately 4 days in vitro. However, accumulating evidence suggests that chronic depolarization induces phenotypic abnormalities whereas growth in chemically defined medium containing 5 mM KCl more closely resembles the constitutive phenotype. To examine this, oligonucleotide microarrays and RT-PCR of selected mRNAs were used to compare transcription profiles of cultures grown in 5 mM and 25 mM KCl. In some cases, N-methyl-D-aspartate (NMDA) which, like elevated KCl, promotes long-term survival was also tested. Robust changes in several gene groups were observed and indicated that growth in elevated KCl: induces expression of mRNAs that are not normally observed; represses expression of mRNAs that should be present; maintains expression of mRNAs that are markers of immature neurons. Supplementation of the growth medium with NMDA instead of elevated KCl produces similar abnormalities. Altogether, these data indicate that growth in 5 mM KCl more closely mimics survival and maturation of granule neurons in vivo and should therefore be adopted in future studies.

Multitasking C2H2 zinc fingers link Zac DNA binding to coordinated regulation of p300-histone acetyltransferase activity

Zac is a C(2)H(2) zinc finger protein that regulates apoptosis and cell cycle arrest through DNA binding and transactivation. The coactivator proteins p300/CBP enhance transactivation through their histone acetyltransferase (HAT) activity by modulating chromatin structure. Here, we show that p300 increases Zac transactivation in a strictly HAT-dependent manner. Whereas the classic recruitment model proposes that coactivation simply depends on the capacity of the activator to recruit the coactivator, we demonstrate that coordinated binding of Zac zinc fingers and C terminus to p300 regulates HAT function by increasing histone and acetyl coenzyme A affinities and catalytic activity. This concerted regulation of HAT function is mediated via the KIX and CH3 domains of p300 in an interdependent manner. Interestingly, Zac zinc fingers 6 and 7 simultaneously play key roles in DNA binding and p300 regulation. Our findings demonstrate, for the first time, that C(2)H(2) zinc fingers can link DNA binding to HAT signaling and suggest a dynamic role for DNA-binding proteins in the enzymatic control of transcription.

Zac1 is expressed in progenitor/stem cells of the neuroectoderm and mesoderm during embryogenesis: differential phenotype of the Zac1-expressing cells during development

Zac1, a new zinc-finger protein that regulates both apoptosis and cell cycle arrest, is abundantly expressed in many neuroepithelia during early brain development. In the present work, we study the expression of Zac1 during early embryogenesis and we determine the cellular phenotype of the Zac1-expressing cells throughout development. Our results show that Zac1 is expressed in the progenitor/stem cells of several tissues (nervous system, skeleton, and skeletal muscle), because they colocalize with several progenitor/stem markers (Nestin, glial fibrillary acidic protein, FORSE-1, proliferating cell nuclear antigen, and bromodeoxyuridine). In postnatal development, Zac1 is expressed in all phases of the life cycle of the chondrocytes (from proliferation to apoptosis), in some limbic gamma-aminobutyric acid-ergic neuronal subpopulations, and during developmental myofibers. Therefore, the intense expression of Zac1 in the progenitor/stem cells of different cellular lineages during the proliferative cycle, before differentiation into postmitotic cells, suggests that Zac1 plays an important role in the control of cell fate during neurogenesis, chondrogenesis, and myogenesis.

Cyclic AMP-mediated regulation of transcription factor Lot1 expression in cerebellar granule cells

Lot1, a zinc finger transcription factor acting as a tumor suppressor gene on tumoral cells, is highly expressed during brain development. In developing rat cerebellum, Lot1 expression is high in cerebellar granule cells (CGC), a neuronal population undergoing postnatal neurogenesis. The time course of Lot1 cerebellar expression closely matches the expression of pituitary adenylate cyclase-activating polypeptide (PACAP) receptors coupled to adenylyl cyclase. The aim of this study was to ascertain whether Lot1 expression is regulated by cAMP-dependent pathways and to identify mechanisms of Lot1 activation in CGC cultures. Our results show that Lot1 expression in CGC is cAMP-dependent, as treatments with either forskolin or PACAP-38 induced an increase in its expression at both the mRNA and protein levels. This effect on Lot1 expression was mimicked by dibutyryl cAMP and suppressed by protein kinase A and MEK inhibitors. In parallel, we found that treatments with forskolin and PACAP-38 in precursor CGC inhibited bromodeoxyuridine incorporation by 25 and 35%, respectively, indicating a negative effect on neuronal precursor proliferation. Luciferase reporter analysis and mutagenesis of the Lot1 promoter region indicated a crucial role of the AP1-binding site (located at -268 bp) in cAMP-induced Lot1 transcription. In addition, cotransfection experiments indicated that the c-Fos/c-Jun heterodimer is responsible for cAMP-dependent Lot1 transcriptional activation. In conclusion, our data demonstrate that, in CGC, Lot1 is under the transcriptional control of cAMP through an AP1 site regulated by the c-Fos/c-Jun heterodimer and suggest that this gene may be an important element of the cAMP-mediated pathway that regulates neuronal proliferation through the protein kinase A-MEK signaling cascade.

Bilateral, vascular and perivascular glial upregulation of heat shock protein-27 after repeated epileptic seizures

Heat shock protein-27 (HSP-27) is an inducible stress response protein. It inhibits apoptotic cell death and is a reliable marker for oxidative stress. We studied the induction of HSP-27 in rat brains on days 1, 4 and 14 after repeated, pentylenetetrazole (PTZ)-induced seizures using immunohistochemisty. Saline treated control rats showed no induction of HSP-27. HSP-27 reactive astrocytes were rarely seen 1 or 4 days after PTZ injection. When present, single astrocytes were located in the cortex and/or the hippocampus. After 14 days PTZ treatment, a bilateral distribution of HSP-27 immunoreactive glia was present in piriform and entorhinal cortices and in the dentate gyrus of most brains. Rats with most intense HSP-27 upregulation showed HSP-27 in amygdala and thalamic nuclei. Astrocytes associated with blood vessels presented strongest HSP-27 staining, but did not show upregulation of gial fibrillary acidic protein and none responded with HSP-47 expression. Additionally, HSP-27 immunoreactivity increased in the endothelial cells of blood vessels in the affected brain regions, although no neuronal induction occurred. Contrastingly, a subconvulsive dose of the glutamine synthetase inhibitor L-methionine sulfoxime, which acts directly on astrocytes, resulted in a rapid, homogeneous astrocyte-specific HSP-27 upregulation within 24 h. Thus, repeated PTZ-induced seizure activity elicits a focal "heat shock" response in endothelial cells and astrocytes of selected cerebral regions indicating that expression of HSP-27 occurred in a seizure-dependent manner within the affected cerebral circuitries. Therefore, this PTZ-model of repeated seizure activity exhibited a cortical pattern of HSP-27 expression which is most comparable to that known from patients with epilepsy.