Rise In mRNA Levels Research Articles

Inhibition of intestinal FXR activity as a possible mechanism for the beneficial effects of a probiotic mix supplementation on lipid metabolism alterations and weight gain in mice fed a high fat diet

ABSTRACT Supplementation with probiotics has emerged as a promising therapeutic tool to manage metabolic diseases. We investigated the effects of a mix of Bifidobacterium animalis subsp. lactis LA804 and Lactobacillus gasseri LA806 on high-fat (HF) diet -induced metabolic disease in mice. Supplementation with the probiotic mix in HF diet-fed mice (HF-Pr2) reduced weight and fat mass gains, decreased hepatic lipid accumulation, and lowered plasma triglyceride peak during an oral lipid tolerance test. At the molecular level, the probiotic mix protected against HF-induced rise in mRNA levels of genes related to lipid uptake, metabolism, and storage in the liver and white adipose tissues, and strongly decreased mRNA levels of genes related to inflammation in the white adipose tissue and to oxidative stress in the liver. Regarding intestinal homeostasis, the probiotic mix did not prevent HF-induced gut permeability but slightly modified microbiota composition without correcting the dysbiosis induced by the HF diet. Probiotic supplementation also modified the cecal bile acid (BA) profile, leading to an increase in the Farnesoid-X-Receptor (FXR) antagonist/agonist ratio between BA species. In agreement, HF-Pr2 mice exhibited a strong inhibition of FXR signaling pathway in the ileum, which was associated with lipid metabolism protection. This is consistent with recent reports proposing that inhibition of intestinal FXR activity could be a potent mechanism to overcome metabolic disorders. Altogether, our results demonstrate that the probiotic mix evaluated, when administered preventively to HF diet-fed mice could limit obesity and associated lipid metabolism disorders, likely through the inhibition of FXR signaling in the intestinal tract.

Dynamic modulation of genomic enhancer elements in the suprachiasmatic nucleus, the site of the mammalian circadian clock.

The mammalian suprachiasmatic nucleus (SCN), located in the ventral hypothalamus, synchronizes and maintains daily cellular and physiological rhythms across the body, in accordance with environmental and visceral cues. Consequently, the systematic regulation of spatiotemporal gene transcription in the SCN is vital for daily timekeeping. So far, the regulatory elements assisting circadian gene transcription have only been studied in peripheral tissues, lacking the critical neuronal dimension intrinsic to the role of the SCN as central brain pacemaker. By using histone-ChIP-seq, we identified SCN-enriched gene regulatory elements that associated with temporal gene expression. Based on tissue-specific H3K27ac and H3K4me3 marks, we successfully produced the first-ever SCN gene-regulatory map. We found that a large majority of SCN enhancers not only show robust 24-h rhythmic modulation in H3K27ac occupancy, peaking at distinct times of day, but also possess canonical E-box (CACGTG) motifs potentially influencing downstream cycling gene expression. To establish enhancer-gene relationships in the SCN, we conducted directional RNA-seq at six distinct times across the day and night, and studied the association between dynamically changing histone acetylation and gene transcript levels. About 35% of the cycling H3K27ac sites were found adjacent to rhythmic gene transcripts, often preceding the rise in mRNA levels. We also noted that enhancers encompass noncoding, actively transcribing enhancer RNAs (eRNAs) in the SCN, which in turn oscillate, along with cyclic histone acetylation, and correlate with rhythmic gene transcription. Taken together, these findings shed light on genome-wide pretranscriptional regulation operative in the central clock that confers its precise and robust oscillation necessary to orchestrate daily timekeeping in mammals.

Probiotics Surface-Delivering Fiber2 Protein of Fowl Adenovirus 4 Stimulate Protective Immunity Against Hepatitis-Hydropericardium Syndrome in Chickens.

Background and ObjectivesHepatitis-hydropericardium syndrome (HHS) caused by Fowl adenoviruses serotype 4 (FAdV-4) leads to severe economic losses to the poultry industry. Although various vaccines are available, vaccines that effectively stimulate intestinal mucosal immunity are still deficient. In the present study, novel probiotics that surface-deliver Fiber2 protein, the major virulence determiner and efficient immunogen for FAdV-4, were explored to prevent this fecal–oral-transmitted virus, and the induced protective immunity was evaluated after oral immunization.MethodsThe probiotic Enterococcus faecalis strain MDXEF-1 and Lactococcus lactis NZ9000 were used as host strains to deliver surface-anchoring Fiber2 protein of FAdV-4. Then the constructed live recombinant bacteria were orally vaccinated thrice with chickens at intervals of 2 weeks. Following each immunization, immunoglobulin G (IgG) in sera, secretory immunoglobulin A (sIgA) in jejunum lavage, immune-related cytokines, and T-cell proliferation were detected. Following challenge with the highly virulent FAdV-4, the protective effects of the probiotics surface-delivering Fiber2 protein were evaluated by verifying inflammatory factors, viral load, liver function, and survival rate.ResultsThe results demonstrated that probiotics surface-delivering Fiber2 protein stimulated humoral and intestinal mucosal immune responses in chickens, shown by high levels of sIgA and IgG antibodies, substantial rise in mRNA levels of cytokines, increased proliferative ability of T cells in peripheral blood, improved liver function, and reduced viral load in liver. Accordingly, adequate protection against homologous challenges and a significant increase in the overall survival rate were observed. Notably, chickens orally immunized with E. faecalis/DCpep-Fiber2-CWA were completely protected from the FAdV-4 challenge, which is better than L. lactis/DCpep-Fiber2-CWA.ConclusionThe recombinant probiotics surface-expressing Fiber2 protein could evoke remarkable humoral and cellular immune responses, relieve injury, and functionally damage target organs. The current study indicates a promising method used for preventing FAdV-4 infection in chickens.

Transcriptional regulation of acetyl CoA and lipid synthesis by PII protein in Synechococcus PCC 7942.

PII protein family is widespread in prokaryotes and plants. In this study, impacts of PII deficiency on the synthesis of acetyl CoA and acetyl CoA carboxylase enzyme (ACCase) was analyzed in the Synechococcus sp. PCC 7942 by evaluating the mRNA levels of pyruvate kinase (PK), pyruvate dehydrogenase (PDH), citrate synthase (CS), biotin synthase (BS), biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), carboxyl transferase (CT) α and β subunits. The PII deficient Synechococcus sp. PCC 7942 showed upregulation of all the above-mentioned genes, except CS. Analyses of genes required for acetyl coA synthesis exhibited a substantial increase in the transcript levels of PK and PDH in the PII mutant strain. In addition, the PII mutant also displayed reduced acetyl CoA content, high ACCase activity, and increased lipid content. The lessening of acetyl CoA content was attributed to the rapid utilization of acetyl CoA in fatty acid synthesis as well as in the TCA cycle whereas the increased ACCase activity was ascribed to the rise in mRNA levels of BS, BC, BCCP, CT α, and β genes. However, increased lipid content was correlated with the declined total protein content. Hence, the study suggested that PII protein regulates the synthesis of acetyl CoA and ACCase enzyme at the transcriptional level.

OP86 – 2425: Expression patterns of micro-RNAs 146a, 181a, and 155 in subacute sclerosing panencephalitis

Objective Subacute sclerosing panencephalitis is caused by persistent brain infection of mutated virus, showing inflammation, neurodegeneration, and demyelination. Although many factors are emphasized in the pathogenesis of subacute sclerosing panencephalitis, the exact mechanism of neurodegeneration remains unknown. Micro-RNAs are small, noncoding RNAs that regulate gene expression at the posttranscriptional levels. Micro-RNAs are essential for normal immune system development; besides they are also implicated in the pathogenesis of many chronic inflammatory disorders. The aim of this study is to investigate the expression patterns of micro-RNAs 146a, 181a, and 155 in peripheral blood mononuclear cells of patients with subacute sclerosing panencephalitis. Methods We enrolled 39 patients with subacute sclerosing panencephalitis and 41 healthy controls. Quantitative analysis of micro-RNAs 146a, 181a, and 155 were performed using specific stem-loop primers followed by real-time polymerase chain reaction. Results All of 3 micro-RNAs were upregulated in subacute sclerosing panencephalitis patients. In addition, the level of micro-RNA 155 expression was higher in stage 3 patients. But, micro-RNA 146a and 181a expression levels showed no association or correlation with clinically relevant data. Conclusion Alteration of peripheral blood mononuclear cell micro-RNAs in subacute sclerosing panencephalitis may shed new light on the pathogenesis of disease and may contribute to the aberrant systemic rise in mRNA levels in subacute sclerosing panencephalitis.

Expression patterns of micro-RNAs 146a, 181a, and 155 in subacute sclerosing panencephalitis.

Subacute sclerosing panencephalitis is caused by persistent brain infection of mutated virus, showing inflammation, neurodegeneration, and demyelination. Although many factors are emphasized in the pathogenesis of subacute sclerosing panencephalitis, the exact mechanism of neurodegeneration remains unknown. Micro-RNAs are small, noncoding RNAs that regulate gene expression at the posttranscriptional levels. Micro-RNAs are essential for normal immune system development; besides they are also implicated in the pathogenesis of many chronic inflammatory disorders. The aim of this study is to investigate the expression patterns of micro-RNAs 146a, 181a, and 155 in peripheral blood mononuclear cells of patients with subacute sclerosing panencephalitis. We enrolled 39 patients with subacute sclerosing panencephalitis and 41 healthy controls. Quantitative analysis of micro-RNAs 146a, 181a, and 155 were performed using specific stem-loop primers followed by real-time polymerase chain reaction. All of 3 micro-RNAs were upregulated in subacute sclerosing panencephalitis patients. In addition, the level of micro-RNA 155 expression was higher in stage 3 patients. But, micro-RNA 146a and 181a expression levels showed no association or correlation with clinically relevant data. Alteration of peripheral blood mononuclear cell micro-RNAs in subacute sclerosing panencephalitis may shed new light on the pathogenesis of disease and may contribute to the aberrant systemic rise in mRNA levels in subacute sclerosing panencephalitis.

Ischemic Post-Conditioning Partially Reverses Cell Cycle Reactivity Following Ischemia/Reperfusion Injury: A Genome-Wide Survey

Neuronal cell cycle re-entry is pro-apoptotic. The neuroprotective effects and anti-apoptosis of ischemic postconditioning (IPostC) are well established but the underlying mechanism is still unknown. We explored this critical gap in the present study by genomic comparison of ischemic rat cortex following transient middle cerebral artery occlusion (tMCAO) alone and tMCAO+IPostC. The gene expression profiles of ipsilateral cortices were subjected to microarray analysis. RT-PCR, immunoblotting, and immunofluorescence were subsequently used to quantify or localize the cell proliferation marker proliferating cell nuclear antigen (PCNA), positive and negative cell cycle regulators, and related signaling molecules. Microarray analysis revealed that tMCAO-induced transcriptional changes in 40 cell cycle regulators were ameliorated by IPostC, suggesting that IPostC reversed neuronal cell cycle re-entry. IPostC reversed the rise in mRNA levels of positive cell cycle regulators ccnb1, cdk1, cdca2, cdca3, and cdca7. Elevations in cyclin D1 and neuronal cyclin A2 were similarly inhibited as well. tMCAO-induced phosphorylation of extracellular signal-regulated kinase (p-ERK), glycogen synthase kinase-3β (p-GSK-3β), and cAMP response element binding protein (p-CREB) were also all depressed by IPostC. Furthermore, p-ERK colocalized with neuronal cyclin A2. The present study demonstrates the potent inhibitory effect of IPostC treatment on tMCAO-induced cell-cycle reentry and on ERK/CREB and GSK- 3β/CREB signaling. Because neuronal cell cycle re-entry is pro-apoptotic, these findings lend insight into potential mechanisms underlying neuroprotection of IPostC.

Abstract WP117: Ischemic Post-conditioning Partially Reverses Cell Cycle Re-entry Following Transient Ischemia/Reperfusion Injury

Background and purpose —The neuroprotective effects of ischemic postconditioning (IPostC) are well established but the underlying mechanism is still unknown. We began to explore this critical gap in the field by genomic comparison of ischemic rat cortex following transient middle cerebral artery occlusion (tMCAO) alone or tMCAO+IPostC. Methods and Results —Microarray analysis revealed that tMCAO-induced transcriptional changes in 40 cell cycle regulators were ameliorated by IPostC, suggesting that IPostC reversed neuronal cell cycle re-entry. RT-PCR, immunoblotting, and immunofluorescence were subsequently used to quantify or localize the cell proliferation marker proliferating cell nuclear antigen (PCNA), positive and negative cell cycle regulators, and related signaling molecules. As expected, IPostC reversed the rise in mRNA levels of positive cell cycle regulators cdcb1, cdk1, cdca2, cadca3, and cdca7. Elevations in cyclin D1 and neuronal cyclin A2 were similarly inhibited. tMCAO-induced phosphorylation of extracellular signal-regulated kinase (p-ERK), glycogen synthase kinase-3β (p-GS3K3β), and cAMP response element binding protein (p-CREB) were also all depressed by IPostC. Furthermore, p-ERK colocalized with neuronal cyclin A2. Conclusions —The present study demonstrates the potent inhibitory effect of IPostC treatment on tMCAO-induced cell-cycle reentry and on ERK/CREB and GSK3β/CREB signaling. Because neuronal cell cycle re-entry is pro-apoptotic, these findings lend insight into potential mechanisms underlying neuroprotection with IPostC.

Upregulation of Intestinal Mucin Expression by the Probiotic Bacterium E. coli Nissle 1917.

The probiotic E. coli Nissle 1917 (EcN) has been reported to have various health benefits; however, very little is known about their underlying mechanisms. In this regard, the present study aimed to elucidate the effect of the bacterium on mucin production by intestinal epithelial cells. Incubation of HT-29 cells with EcN lead to a contact time-dependent rise in mRNA levels of the MUC2, MUC3, MUC5AC, and MUC5A. The expression was markedly higher with MUC5AC gene. In most cases, MUC genes expression was more pronounced in polarized cells compared to non-polarized ones. In contrast to MUC3, the basal stimulation of polarized cells brought about markedly higher levels of other tested mucins. Similar but milder results were observed when living EcN was replaced by inactivated bacteria. With exception of MUC3, the conditioned media showed no significant effect on the mRNA level of the tested mucins. The above-mentioned mRNA results were confirmed on protein level using enzyme-linked lectin assay (ELLA) and enzyme-linked immunosorbant assay (ELISA). In contrast to other treatments, basal stimulation of polarized cells showed a growth phase-dependent MUC induction with more prominent effect by stationary-phase bacteria. In contrast to MUC 2 and MUC3, the induction of MUC5AC and MUC5B showed a bacterial count-dependent pattern. In conclusion, EcN was found to stimulate MUC gene expression in HT-29 intestinal cells. This stimulation was more distinct with polarized cells. Such observation may partially interpret some health benefits of the probiotic bacterium including antagonizing pathogen adhesion and protection of the intestinal mucosa.

EGO-1, a C. elegans RdRP, Modulates Gene Expression via Production of mRNA-Templated Short Antisense RNAs

The development of the germline in Caenorhabditis elegans is a complex process involving the regulation of thousands of genes in a coordinated manner. Several genes required for small RNA biogenesis and function are among those required for the proper organization of the germline. EGO-1 is a putative RNA-directed RNA polymerase (RdRP) that is required for multiple aspects of C. elegans germline development and efficient RNA interference (RNAi) of germline-expressed genes. RdRPs have been proposed to act through a variety of mechanisms, including the posttranscriptional targeting of specific mRNAs, as well as through a direct interaction with chromatin. Despite extensive investigation, the molecular role of EGO-1 has remained enigmatic. Here we use high-throughput small RNA and messenger RNA sequencing to investigate EGO-1 function. We found that EGO-1 is required to produce a distinct pool of small RNAs antisense to a number of germline-expressed mRNAs through several developmental stages. These potential mRNA targets fall into distinct classes, including genes required for kinetochore and nuclear pore assembly, histone-modifying activities, and centromeric proteins. We also found several RNAi-related genes to be targets of EGO-1. Finally, we show a strong association between the loss of small RNAs and the rise of mRNA levels in ego-1(-) animals. Our data support the conclusion that EGO-1 produces triphosphorylated small RNAs derived from mRNA templates and that these small RNAs modulate gene expression through the targeting of their cognate mRNAs.

EXPRESSION PROFILES OF THE CELL MIGRATION-ASSOCIATED GENES DURING RAT LIVER REGENERATION

Cell migration plays the essential role in embryogenesis, wound healing, immunization, infection, and cancer metastasis. To study actions of cell migration-associated genes in liver regeneration, these genes were obtained by seaching for the related databases and literatures, and comprehensive analysis for the gene expression change during the regenerating process in liver was detected by Rat Genome 230 2.0 array, and identification of the LR-associated genes was through comparing the discrepancy in gene expression between sham operation and partial hepatectomy groups. The initially and totally expressed numbers of these genes in the initial phase of LR, G0/G1 transition, cell proliferation, cell differentiation, and structural-functional reconstruction were 88, 16, 79, 9, and 177, 90, 632, 207, respectively, illustrating that the associated genes triggered their expression mainly in the priming stage, and worked in different phases. Their expression similarity was classified into five groups and their expression patterns were categorized into 38 types, and the overall times of up-regulation and down-regulation were 589 and 427. Based on expression profiles and expression patterns of cell migration-associated genes in LR, it was confirmed that cell migration-associated genes rise in mRNA levels.

Rapid Changes in Gene Expression Dynamics in Response to Superoxide Reveal SoxRS-Dependent and Independent Transcriptional Networks

BackgroundSoxR and SoxS constitute an intracellular signal response system that rapidly detects changes in superoxide levels and modulates gene expression in E. coli. A time series microarray design was used to identify co-regulated SoxRS-dependent and independent genes modulated by superoxide minutes after exposure to stress.Methodology/Principal Findings soxS mRNA levels surged to near maximal levels within the first few minutes of exposure to paraquat, a superoxide-producing compound, followed by a rise in mRNA levels of known SoxS-regulated genes. Based on a new method for determining the biological significance of clustering results, a total of 138 genic regions, including several transcription factors and putative sRNAs were identified as being regulated through the SoxRS signaling pathway within 10 minutes of paraquat treatment. A statistically significant two-block SoxS motif was identified through analysis of the SoxS-regulated genes. The SoxRS-independent response included members of the OxyR, CysB, IscR, BirA and Fur regulons. Finally, the relative sensitivity to superoxide was measured in 94 strains carrying deletions in individual, superoxide-regulated genes.Conclusions/SignificanceBy integrating our microarray time series results with other microarray data, E. coli databases and the primary literature, we propose a model of the primary transcriptional response containing 226 protein-coding and sRNA sequences. From the SoxS dependent network the first statistically significant SoxS-related motif was identified.

Systematic identification of protease genes that are differentially expressed in the primate follicle during the periovulatory interval

To systematically identify differentially expressed proteases in the rhesus macaque follicle during the ovulatory process. Changes in the rhesus macaque transcriptome were determined by DNA microarray analysis in the naturally-selected dominant follicle at specific intervals following an ovulatory stimulus. A controlled ovulation protocol (Human Reproduction, 18:2257, 2003) was employed to obtain individual follicles (n = 4/group) before (0 h) and after (12, 24, 36 h) an ovulatory bolus of hCG. The 36 h time point was comprised of two groups consisting of unruptured and ruptured follicles. Total RNA was isolated from individual follicles, with an aliquot being labeled and hybridized to Affymetrix GeneChip® Rhesus Macaque Arrays. Remaining RNA was converted to cDNA for verifying differential expression of select protease genes by real-time PCR. The resultant DNA microarray data revealed significant changes (false discovery rate <0.01) in the expression of genes encoding proteases belonging to the matrix metalloproteinase (MMP1, 9, 10, and 19) and a disintegrin and metalloproteinase with thrombospondin-like repeats (ADAMTS1 and 15) families, as well as for the cysteine protease cathepsin L (CTSL) and the serine protease pepsinogen 5, group I (pepsinogen A or PGA5). A similar pattern of expression was noted for MMP1, MMP9, MMP10, and CTSL genes, with mRNA levels increasing 12 h, followed by a lower level of expression 24–36 h (preovulatory follicles) post-hCG. A second pattern of gene expression was observed for MMP19, ADAMTS1 and ADAMTS15, with mRNA levels increasing significantly 12 h following the administration of an ovulatory bolus of hCG and remaining elevated at the subsequent time points (i.e., 24–36 h). PGA5, a protease not previously implicated in ovarian function, remained at low levels of expression until increasing by 9-fold at 36 h post-hCG. In many cases (MMP1, MMP10, MMP19, ADAMTS1, CTSL, and PGA5), a secondary rise in mRNA levels was noted in the ovulated follicle. Real-time PCR studies confirmed the microarray expression data for MMP1, MMP19, and PGA5. Protease genes belonging to several diverse families are differentially expressed through the rhesus macaque periovulatory interval, and as such likely play an important role in the tissue remodeling of the follicle and the release of a fertilizable oocyte, as well as in the subsequent development of the corpus luteum.

Stability of Nucleolin protein as the basis for the differential expression of Nucleolin mRNA and protein during serum starvation.

Nucleolin is a nucleolar phosphoprotein that plays a direct role in ribosome biogenesis. Our aim was to determine how its activity as a growth-promoting factor is coordinated with, if not regulated by, the cell cycle machinery. In serum starting and then rescuing these cells with serum, we found that the protein level did not drop in the same way that the mRNA level did. In addition, although the mRNA level rises during the immediate period during serum rescue, the protein level remained the same. We found that the protein level was maintained after serum starvation as a result of high stability. There was no selective enhanced translation of the remaining amount of Nucleolin mRNA. With regard to the constancy in protein level despite the rise in mRNA level during serum rescue, there is no concomitant degradation of newly synthesized or old protein and synthesis of new protein. Because Nucleolin has been documented to bind mRNA, APP mRNA being one among them, we propose a autoregulatory model in which Nucleolin regulates the translation of Nucleolin mRNA, such that during a period of excess protein, translation is inhibited through direct binding of Nucleolin protein to its mRNA.

The effect of diabetes on expression of beta1-, beta2-, and beta3-adrenoreceptors in rat hearts.

Diabetic hearts exhibit decreased responsiveness to stimulation by beta-adrenoreceptor (beta-AR) agonists. This decrease in activity may be due to changes in expression and/or signaling of beta-AR. Recently we showed that right atrial strips from 14-week streptozotocin (STZ)-induced diabetic rat hearts exhibit decreased responsiveness to beta1-AR agonist stimulation, but not to beta2-AR agonist. In the present study, we investigated the effects of long-term diabetes on the expression of cardiac beta1-, beta2-, and beta3-ARs and looked at whether these changes could be restored with insulin treatment. Using reverse transcription-polymerase chain reaction (RT-PCR), PAGE, and Western blot analysis, we found that beta1-AR mRNA and protein levels decreased by 34.9 +/- 5.8 and 44.4 +/- 5.8%, respectively, in 14 week-STZ-treated diabetic rat hearts when compared with age-matched controls. On the other hand, mRNA levels encoding beta2- and beta3-ARs increased by 72.5 +/- 16.6 and 97.3 +/- 26.1%, respectively. Although the latter translated into a proportional increase in beta3-AR protein levels (100.0 +/- 17.0%), beta2-AR protein levels decreased to 82.6 +/- 1.1% of control. Insulin treatment for 2 weeks, after 12 weeks of untreated diabetes, partially restored beta1-AR mRNA and protein levels to 60.1 +/- 8.4 and 83.2 +/- 5.0%, respectively, of control. Although insulin treatment minimally attenuated the rise in mRNA levels encoding beta2- and beta3-ARs, the steady-state levels of these proteins returned to near control values. These data suggest that the decreased responsiveness of diabetic hearts to stimulation of beta-AR agonists may be due to a decrease in beta1-AR and an increase beta3-AR expression.

Phenotypic analysis and virulence of Candida albicans LIG4 mutants.

In previous studies, we reported the isolation and preliminary characterization of a DNA ligase-encoding gene of Candida albicans. This gene (LIG4) is the structural and functional homologue of both yeast and human ligase IV, which is involved in nonhomologous end joining (NHEJ) of DNA double-strand breaks. In the present study, we have shown that there are no other LIG4 homologues in C. albicans. In order to study the function of LIG4 in morphogenesis and virulence, we constructed gene deletions. LIG4 transcript levels were reduced in the heterozygote and were completely absent in null strains. Concomitantly, the heterozygote showed a pronounced defect in myceliation, which was slightly greater in the null strain. This was true with several solid and liquid media, such as Spider medium, medium 199, and 2% glucose-1% yeast extract-2% Bacto Peptone, at several pHs. Reintroduction of the wild-type allele into the null mutant partially restored the ability of cells to form hyphae. In agreement with the positive role of LIG4 in morphogenesis, we detected a significant rise in mRNA levels during the morphological transition. LIG4 is not essential for DNA replication or for the repair of DNA damage induced by ionizing radiation or UV light, indicating that these lesions are repaired primarily by homologous recombination. However, our data show that the NHEJ apparatus of C. albicans may control morphogenesis in this diploid organism. In addition, deletion of one or both copies of LIG4 resulted in attenuation of virulence in a murine model of candidiasis.

Increased vascular endothelial growth factor production in the lungs of rats with hypoxia-induced pulmonary hypertension.

Vascular endothelial growth factor (VEGF) is a potent mitogenic and permeability factor targeting predominantly endothelial cells. At least two tyrosine kinase receptors, Flk-1 and Flt-1, mediate its action and are mostly expressed by endothelial cells. VEGF and VEGF receptor expression are upregulated by hypoxia in vivo and the role of VEGF in hypoxia-induced angiogenesis has been extensively studied in a variety of disease entities. Although VEGF and its receptors are abundantly expressed in the lung, their role in hypoxic pulmonary hypertension and the accompanying vascular remodeling are incompletely understood. We report in this in vivo study that hypoxia increases mRNA levels for both VEGF and Flk-1 in the rat lung. The kinetics of the hypoxic response differ between receptor and ligand: Flk-1 mRNA showed a biphasic response to hypoxia with a significant, but transient, rise in mRNA levels observed after 9-15 h of hypoxic exposure and the highest levels noted after 3 wk. In contrast, VEGF mRNA levels did not show a significant increase with acute hypoxia, but increased progressively after 1-3 wk of hypoxia. By in situ hybridization, VEGF mRNA was localized predominantly in alveolar epithelial cells with increased signal in the lungs of hypoxic animals compared with controls. Immunohistochemical staining with anti-VEGF antibodies localized VEGF peptide throughout the lung parenchyma and was increased in hypoxic compared with normoxic animals. Furthermore, hypoxic animals had significantly higher circulating VEGF concentrations compared with normoxic controls. Lung vascular permeability as measured by extravasation of Evans Blue dye was not significantly different between normoxic and hypoxic animals, although a tendency for increased permeability was seen in the hypoxic animals. These findings suggest a possible role for VEGF in the pulmonary response to hypoxia.

Role of calcium in the activation of erp72 and heme oxygenase-1 expression on depletion of endoplasmic reticulum calcium stores in rat neuronal cell culture

Endoplasmic reticulum (ER) calcium pool depletion was induced by 30 min exposure of primary neuronal cells to thapsigargin (Tg), an irreversible inhibitor of ER Ca 2+-ATPase. Twelve hours later, erp72 and heme oxygenase-1 (HO-1) mRNA levels were quantified by PCR. Protein synthesis was also measured. Transient Tg exposure of neurons induced a marked rise in mRNA levels (7-fold and a 21-fold increase in erp72 and HO-1 mRNA levels; P<0.001). Loading of neurons with the calcium chelator 1,2-bis(o-Aminophenoxy)ethane- N, N, N′, N′-tetra(acetoxymethyl)ester (BAPTA-AM) prior to thapsigargin treatment had only a minor effect on the Tg-induced rise in gene expression. This small inhibitory effect may result from the severe suppression of protein synthesis caused by BAPTA-AM. The results suggest that the increase in stress gene expression induced by exposure of neurons to Tg is triggered by a decrease in ER calcium activity and not by the corresponding increase in cytoplasmic calcium activity.

Temporal analysis of changes in neuronal c-fos mRNA levels induced by depletion of endoplasmic reticulum calcium stores: effect of clamping cytoplasmic calcium activity at resting levels.

Activation of immediate early gene expression is a key event in stress-induced neuronal cell injury. To study whether changes in cytoplasmic calcium activity are necessary to activate neuronal immediate early gene expression, endoplasmic reticulum (ER) calcium stores of primary neurons were depleted by exposing cells to thapsigargin (Tg), an irreversible inhibitor of ER Ca2+-ATPase. Tg-induced rise in [Ca2+]i and the effect of loading neurons with the cell-permeable calcium chelator BAPTA-AM on this increase in [Ca2+]i were measured in fura-2-loaded cells by fluorescence microscopy. Changes in c-fos mRNA levels were evaluated by quantitative PCR. Tg treatment of neurons produced a pronounced rise in c-fos mRNA levels (approximately 10-fold more than DMSO) which peaked at 1 h after exposure. The Tg-induced rise in c-fos mRNA content was unchanged (hippocampal neurons) or even increased further (cortical neurons) by preloading cells with BAPTA before incubation with Tg. It is concluded that in neuronal cells an increase in cytoplasmic calcium activity is not a prerequisite for a rise in mRNA levels of c-fos. Thus, stress-induced changes in mRNA levels of immediate early genes of neurons may also result from disturbances in ER calcium homeostasis and not necessarily by an overload of cells with calcium ions. The results of the present series of experiments cast further doubt on the widely accepted hypothesis that the stress-induced cytoplasmic overload of neurons with calcium ions is the primary event triggering cell injury.

Varied expression patterns of human H1 histone genes in different cell lines.

Five main type H1 histones have been described in man (H1.1-H1.5) in addition to the testis specific type H1t and the replacement subtype H1 degrees, which is found mainly in highly differentiated cells. We have isolated this whole complement of H1 genes and have studied the expression of the seven human H1 subtype genes in several cell lines. The RNAase protection assay was used to discriminate between the very similar transcripts derived from the seven H1 subtype genes. With the exception of H1.2 and H1.4, we found substantial differences between the H1 mRNA levels in the different cell lines tested. No H1.1 mRNA was detected in most of the cell lines and just a low level of H1.1 mRNA was found in human testis. In contrast to the differential patterns of the other subtypes, H1.2 and H1.4 were in all cells expressed at a high level, indicating a basal function compared with the other H1 histones. Because differences in the timing of H1 protein subtype synthesis have been reported, we have analyzed the kinetics of accumulation of H1 subtypes in synchronized HeLa cells and observed that all H1 subtypes examined (H1 degrees, H1.2-H1.5) were expressed in a replication-dependent manner. The analysis showed a differential rise of mRNA levels during S-phase, from four-fold (H1 degrees) to 15-fold (H1.5). Our results may point at a specific function of each subtype and suggest that expression of the H1 histone subtype genes depends on common S-phase-depent factors as well as on individual regulatory systems. Thus, the data presented here provide a basis for further analysis of the regulation and function of the complex H1 gene and protein family.