ATM-deficient neural precursors develop senescence phenotype with disturbances in autophagy

ATM is a kinase involved in DNA damage response (DDR), regulation of response to oxidative stress, autophagy and mitophagy. Mutations in the ATM gene in humans result in ataxi A-Telangiectasia disease (A-T) characterized by a variety of symptoms with neurodegeneration and premature ageing among them. Since brain is one of the most affected organs in A-T, we have focused on senescence of neural progenitor cells (NPCs) derived from A-T reprogrammed fibroblasts. Accordingly, A-T NPCs obtained through neural differentiation of iPSCs in 5% oxygen possessed some features of senescence including increased activity of SA-β-gal and secretion of IL6 and IL8 in comparison to control NPCs. This phenotype of A-T NPC was accompanied by elevated oxidative stress. A-T NPCs exhibited symptoms of impaired autophagy and mitophagy with lack of response to chloroquine treatment. Additional sources of oxidative stress like increased oxygen concentration (20 %) and H₂O₂ respectively aggravated the phenotype of senescence and additionally disturbed the process of mitophagy. In both cases only A-T NPCs reacted to the treatment. We conclude that oxidative stress may be responsible for the phenotype of senescence and impairment of autophagy in A-T NPCs. Our results point to senescent A-T cells as a potential therapeutic target in this disease.

Clinical value of tissue DNA integrity index in pancreatic cancer

BACKGROUND

DNA integrity index as a blood biomarker is associated with the prognosis of cancer patients.

AIMS

The primary goal of the study was to examine tissue DNA integrity index (DII) in a group of pancreatic cancer (PC) tumor tissues and control adjacent pancreatic tissues. We also aimed to test the relationship between the tumor tissue DII and the clinicopathological parameters and the overall survival.

METHODS

In the prospective study, DII was calculated using: the Alu 247/115 ratio, the LINE1 300/79 ratio and the average of the above values, based on the data obtained by real-time PCR. The tumors samples (n = 42) originated from the patients with pathologically confirmed pancreatic ductal adenocarcinoma and the control adjacent pancreatic tissue specimens (n = 32) were received from surgical margins.

RESULTS

Specimens from the tumors pathologically marked as R1 (microscopic residual tumor) had a significantly higher LINE1 300/79 ratio values than specimens from adjacent normal pancreatic tissue (P<0.05). ROC curve analysis revealed that LINE1 300/79 ratio is a good parameter to distinguish between R0 and R1 tumors (AUC = 0.703, P<0.05).

CONCLUSIONS

This is the first study exploring the tissue DNA integrity index (DII) in pancreatic cancer. LINE1 DII can be used as auxiliary parameter for objective evaluation of margin status.

Increased activity of the sterol branch of the mevalonate pathway elevates glycosylation of secretory proteins and improves antifungal properties of Trichoderma atroviride

Some Trichoderma spp. have an ability to inhibit proliferation of fungal plant pathogens in the soil. Numerous compounds with a proven antifungal activity are synthesized via the terpene pathway. Here, we stimulated the activity of the mevalonate pathway in T. atroviride P1 by expressing the Saccharomyces cerevisiae ERG20 gene coding for farnesyl pyrophosphate (FPP) synthase, a key enzyme of this pathway. ERG20-expressing Trichoderma strains showed higher activities of FPP synthase and squalene synthase, the principal recipient of FPP in the mevalonate pathway. We also observed activation of dolichyl phosphate mannose (DPM) synthase, an enzyme in protein glycosylation, and significantly increased O- and N-glycosylation of secreted proteins. The hyper-glycosylation of secretory hydrolases could explain their increased activity observed in the ERG20 transformants. Analysis of the antifungal properties of the new strains revealed that the hydrolases secreted by the transformants inhibited growth of a plant pathogen, Pythium ultimum more efficiently compared to the control strain. Consequently, the biocontrol activity of the transgenic strains, determined as their ability to protect bean seeds and seedlings against harmful action of P. ultimum, was also improved substantially.

Tetrabromobisphenol A-induced depolarization of rat cerebellar granule cells: ex vivo and in vitro studies

The brominated flame retardant tetrabromobisphenol A (TBBPA) is toxic to cultured brain neurons, and glutamate receptors partially mediate this effect; consequently, the depolarizing effect of TBBPA on neurons is to be expected, but it is yet to be actually demonstrated. The aim of this study was to detect TBBPA-evoked depolarization and identify the underlying mechanisms. The plasma membrane potential of rat cerebellar granule cells (CGC) in cerebellar slices or in primary cultures was measured using whole-cell current clamp recordings, or the fluorescent probe oxonol VI, respectively. The contribution of NMDA and AMPA receptors, voltage-gated sodium channels and intracellular calcium mobilization was tested using their selective antagonists or inhibitors. Direct interactions of TBBPA with NMDARs were tested by measuring the specific binding of radiolabeled NMDAR ligands to isolated rat cortical membrane fraction. TBBPA (25 μM) strongly depolarized CGC in cerebellar slices, and at ≥ 7.5 μM concentration-dependently depolarized primary CGC cultures. Depolarization of the primary CGC by 25 μM TBBPA was partly reduced when MK-801 was applied alone or in combination with either TTX or CNQX, or where bastadin 12 was applied in combination with ryanodine, whereas depolarization was completely prevented when MK-801, CNQX and TTX where combined. TBBPA had no effect on the specific binding of NMDAR radio-ligands to isolated cortical membranes. These results demonstrate the depolarizing effect of TBBPA on CGC, which is mainly mediated by ionotropic glutamate receptors, while voltage-gated sodium channels are also involved. We found no evidence for the direct activation of NMDARs by TBBPA.

The collagen scaffold supports hiPSC-derived NSC growth and restricts hiPSC

The human induced pluripotent stem cells (hiPSC) are one of the promising candidates as patient specific cell source for autologous transplantation or modeling of diseases. The collagen (Col) scaffolds have been shown suitable to create in vitro biomimetic microenvironment for human neural stem cells, but their ability to accommodate stem cells at different stages of neural differentiation has not been verified yet. In this paper we compare lineage related hiPSC during neural differentiation for their ability to colonize Col scaffold. We have also focused on modification of collagen physicochemical properties with improved mechanical and thermal stability, without loss of its biological activity. The hiPSC expressing markers of pluripotency (OCT4, SOX2, NANOG) after neural commitment are NESTIN, GFAP, PDGFR alpha, beta- TUBULIN III, MAP-2, DCX, GalC positive. We have shown, that Col scaffold was not preferable for hiPSC culture, while the neurally committed population after seeding on Col scaffolds revealed good adhesion, viability, proliferation, along with sustaining markers of neuronal and glial differentiation. The Col scaffold-based 3D culture of hiPSC-NSCs may serve as a research tool for further translational studies.

Is mitochondrial DNA copy number a good prognostic marker in resectable pancreatic cancer?

BACKGROUND

The aim of this prospective study was to investigate mitochondrial DNA (mtDNA) copy number in a group of resectable pancreatic cancer (PC) tumor tissues and adjacent normal pancreatic tissues, and to explore the correlation between the mtDNA content in tissues and the clinicopathological parameters and the overall survival.

METHODS

Relative mtDNA copy number was measured by the quantitative PCR-based assay. The tumors specimens (n = 43) originated from the patients with pathologically confirmed pancreatic ductal adenocarcinoma who did not receive any neoadjuvant systemic therapy. The adjacent normal pancreatic tissue samples (n = 31) were obtained from surgical margins.

RESULTS

mtDNA copy number was significantly lower in PC tissue (P < 0.001) compared to adjacent normal pancreatic tissue. Jonckheere-Terpstra trend testing indicated a statistically significant decrease in median mtDNA copy number across the differentiation (adjacent normal pancreatic tissue, low-grade, intermediate-grade, high-grade cancer), P < 0.001. However, the survival analyses failed to show a significant difference in survival between patients with high and low mtDNA copy number.

CONCLUSIONS

To the best of our knowledge, we provided the first evidence that mitochondrial DNA copy number was significantly lower in pancreatic cancer tissue (P < 0.001) compared to adjacent normal pancreatic tissue. Also, we demonstrated that mitochondrial copy number was not a significant marker for predicting prognosis in resectable pancreatic cancer.

Bezafibrate Upregulates Mitochondrial Biogenesis and Influence Neural Differentiation of Human-Induced Pluripotent Stem Cells

Bezafibrate (BZ) regulates mitochondrial biogenesis by activation of PPAR’s receptors and enhancing the level of PGC-1α coactivator. In this report, we investigated the effect of BZ on the expression of genes (1) that are linked to different pathways involved in mitochondrial biogenesis, e.g., regulated by PPAR’s receptors or PGC-1α coactivator, and (2) involved in neuronal or astroglial fate, during neural differentiation of hiPSC. The tested cell populations included hiPSC-derived neural stem cells (NSC), early neural progenitors (eNP), and neural progenitors (NP). RNA-seq analysis showed the expression of PPARA, PPARD receptors and excluded PPARG in all tested populations. The expression of PPARGC1A encoding PGC-1α was dependent on the stage of differentiation: NSC, eNP, and NP differed significantly as compared to hiPSC. In addition, BZ-evoked upregulation of PPARGC1A, GFAP, S100B, and DCX genes coexist with downregulation of MAP2 gene only at the eNP stage of differentiation. In the second task, we investigated the cell sensitivity and mitochondrial biogenesis upon BZ treatment. BZ influenced the cell viability, ROS level, mitochondrial membrane potential, and total cell number in concentration- and stage of differentiation-dependent manner. Induction of mitochondrial biogenesis evoked by BZ determined by the changes in the level of SDHA and COX-1 protein, and mtDNA copy number, as well as the expression of NRF1, PPARGC1A, and TFAM genes, was detected only at NP stage for all tested markers. Thus, developmental stage-specific sensitivity to BZ of neurally differentiating hiPSC can be linked to mitochondrial biogenesis, while fate commitment decisions to PGC-1α (encoded by PPARGC1A) pathway.

Altered expression of genes involved in programmed cell death in primary cultured rat cerebellar granule cells acutely challenged with tetrabromobisphenol A

In the present study, primary cultures of rat cerebellar granule cells (CGC) and the RT² Profiler PCR array were used to examine the effect of acutely applied brominated flame retardant tetrabromobisphenol A (TBBPA) on the expression of 84 genes related to the main modes of programmed cell death. CGC, at the 7th day of culture, were exposed to 10 or 25μM TBBPA for 30min. Then, 3, 6, and 24h later, the viability of the cells was examined by the staining with propidium iodide (PI) or using the calcein/ethidium homodimer (CA/ET) live/dead kit, and RNA was extracted for the evaluation of gene expression by RT-PCR. At 3, 6 and 24h after the treatment, the number of viable neurons decreased, according to the PI staining method, to 75%, 58% and 41%, respectively, and with the CA/ET method to 65%, 58% and 28%, respectively. In CGC analyzed 3h after the treatment with 25μM TBBPA or 6h after 10μM TBBPA, the only change in the gene expression was a reduction in the expression of Tnf, which is associated with autophagy and may activate some pro-apoptotic proteins. Six hours after 25μM TBBPA, only 2 genes were over-expressed, a pro-apoptotic Tnfrsf10b and Irgm, which is related to autophagy, and the genes that were suppressed included the anti-apoptotic gene Xiap, the necrosis-related Commd4, pro-apoptotic Abl1, 5 genes involved in autophagy (App, Atg3, Mapk8, Pten, and Snca) and 2 genes that participate in two metabolic pathways: Atp6v1g2 (pro-apoptotic and necrosis) and Tnf (pro-apoptotic, autophagy). Autophagy-related Snca and Tnf remained under-expressed 24h after treatment with 25μM TBBPA, which was accompanied by the over-expression of the pro-apoptotic Casp6, the anti-apoptotic Birc3, 2 genes related to autophagy (Htt and Irgm) and 2 genes (Fas and Tp53) that are involved in both apoptosis (pro-apoptotic) and autophagy. These results show a complex pattern of TBBPA-evoked changes in the expression of the genes involved in the programmed neuronal death, indicating no induction of programmed necrosis, an early suppression of the autophagy and anti-apoptotic genes, followed by a delayed activation of genes associated with apoptosis.

Mitochondrial biogenesis and neural differentiation of human iPSC is modulated by idebenone in a developmental stage-dependent manner

Idebenone, the synthetic analog of coenzyme Q10 can improve electron transport in mitochondria. Therefore, it is used in the treatment of Alzheimer’s disease and other cognitive impairments. However, the mechanism of its action on neurodevelopment is still to be elucidated. Here we demonstrate that the cellular response of human induced pluripotent stem cells (hiPSC) to idebenone depends on the stage of neural differentiation. When: neural stem cells (NSC), early neural progenitors (eNP) and advanced neural progenitors (NP) have been studied a significant stimulation of mitochondrial biogenesis was observed only at the eNP stage of development. This coexists with the enhancement of cell viability and increase in total cell number. In addition, we report novel idebenone properties in a possible regulation of neural stem cells fate decision: only eNP stage responded with up-regulation of both neuronal (MAP2), astrocytic (GFAP) markers, while at NSC and NP stages significant down-regulation of MAP2 expression was observed, promoting astrocyte differentiation. Thus, idebenone targets specific stages of hiPSC differentiation and may influence the neural stem cell fate decision.

Sensitivity of hiPSC-derived neural stem cells (NSC) to Pyrroloquinoline quinone depends on their developmental stage

Pyrroloquinoline quinone (PQQ) is a factor influencing on the mitochondrial biogenesis. In this study the PQQ effect on viability, total cell number, antioxidant capacity, mitochondrial biogenesis and differentiation potential was investigated in human induced Pluripotent Stem Cells (iPSC) - derived: neural stem cells (NSC), early neural progenitors (eNP) and neural progenitors (NP). Here we demonstrated that sensitivity to PQQ is dependent upon its dose and neural stage of development. Induction of the mitochondrial biogenesis by PQQ at three stages of neural differentiation was evaluated at mtDNA, mRNA and protein level. Changes in NRF1, TFAM and PPARGC1A gene expression were observed at all developmental stages, but only at eNP were correlated with the statistically significant increase in the mtDNA copy numbers and enhancement of SDHA, COX-1 protein level. Thus, the "developmental window" of eNP for PQQ-evoked mitochondrial biogenesis is proposed. This effect was independent of high antioxidant capacity of PQQ, which was confirmed in all tested cell populations, regardless of the stage of hiPSC neural differentiation. Furthermore, a strong induction of GFAP, with down regulation of MAP2 gene expression upon PQQ treatment was observed. This indicates a possibility of shifting the balance of cell differentiation in the favor of astroglia, but more research is needed at this point.

Mitochondria in brain hypoxia

Neurons vary widely in shape, size, type of neurotransmitters and number of synapses. Their common characteristic is a very high sensitivity to changes in oxygen concentration. The consequence of hypoxia is to launch a series of biochemical reactions called the ischemic cascade. The term is a bit misleading, because it suggests that there is a succession of events, in a linear fashion. In fact, the ischemic cascade involves very complex processes that take place simultaneously and interact with each other. The key role in neuronal responses to hypoxia is played by changes related to mitochondria, which occur immediately after hypoxia, at the beginning of the ischemic cascade. Disturbances in the mitochondrial functions are recognized as an essential element not only in acute but also in chronic hypoxia, as well as neurodegenerative diseases.

The Role of Ca2+ Imbalance in the Induction of Acute Oxidative Stress and Cytotoxicity in Cultured Rat Cerebellar Granule Cells Challenged with Tetrabromobisphenol A

Using primary cultures of rat cerebellar granule cells (CGC) we examined the role of calcium transients induced by tetrabromobisphenol A (TBBPA) in triggering oxidative stress and cytotoxicity. CGC were exposed for 30 min to 10 or 25 µM TBBPA. Changes in intracellular calcium concentration ([Ca²⁺]_i), in the production of reactive oxygen species (ROS), and in the potential of mitochondria (∆Ψm) were measured fluorometrically during the exposure. The intracellular glutathione (GSH) and catalase activity were determined after the incubation; cell viability was evaluated 24 h later. TBBPA concentration-dependently increased [Ca²⁺]_i and ROS production, and reduced GSH content, catalase activity, ∆Ψm and neuronal viability. The combination of NMDA and ryanodine receptor antagonists, MK-801 and bastadin 12 with ryanodine, respectively, prevented Ca²⁺ transients and partially reduced cytotoxicity induced by TBBPA at both concentrations. The antagonists also completely inhibited oxidative stress and depolarization of mitochondria evoked by 10 µM TBBPA, whereas these effects were only partially reduced in the 25 µM TBBPA treatment. Free radical scavengers prevented TBBPA-induced development of oxidative stress and improved CGC viability without having any effect on the rises in Ca²⁺ and drop in ∆Ψm. The co-administration of scavengers with NMDA and ryanodine receptor antagonists provided almost complete neuroprotection. These results indicate that Ca²⁺ imbalance and oxidative stress both mediate acute toxicity of TBBPA in CGC. At 10 µM TBBPA Ca²⁺ imbalance is a primary event, inducing oxidative stress, depolarization of mitochondria and cytotoxicity, whilst at a concentration of 25 µM TBBPA an additional Ca²⁺-independent portion of oxidative stress and cytotoxicity emerges.

Select putative neurodevelopmental toxins modify SNAP-25 expression in primary cultures of rat cerebellar granule cells

A presynaptic protein SNAP-25 belonging to SNARE complex which is instrumental in intracellular vesicular trafficking and exocytosis, has been implicated in hyperactivity and cognitive abilities in some neuropsychiatric disorders. The unclear etiology of the behavior disrupting neurodevelopmental disabilities in addition to genetic causes most likely involves environmental factors. The aim of this in vitro study was to test if various suspected developmental neurotoxins can alter SNAP-25 mRNA and protein expression in neurons. Real-time PCR and Western blotting analyses were used to assess SNAP-25 mRNA and protein levels in primary cultures of rat cerebellar granule cells (CGCs). The test substances: tetrabromobisphenol-A (TBBPA), thimerosal (TH), silver nanoparticles (NAg), valproic acid (VPA) and thalidomide (THAL), were administered to CGC cultures at subtoxic concentrations for 24h. The results demonstrated that SNAP-25 mRNA levels were increased by 49 and 66% by TBBPA and THAL, respectively, whereas VPA and NAg reduced these levels to 48 and 64% of the control, respectively. The SNAP-25 protein content in CGCs was increased by 79% by TBBPA, 25% by THAL and 21% by NAg; VPA and TH reduced these levels to 73 and 69% of the control, respectively. The variety of changes in SNAP-25 expression on mRNA and protein level suggests the diversity of the mechanism of action of the test substances. This initial study provided no data on concentration-effect relations and on functional changes in CGCs. However it is the first to demonstrate the effect of different compounds that are suspected of causing neurodevelopmental disabilities on SNAP-25 expression. These results suggest that this protein may be a common target for not only inherited but also environmental modifications linked to behavioral deficits in neurodevelopmental disabilities.

Variants in CUL4B are associated with cerebral malformations

Variants in cullin 4B (CUL4B) are a known cause of syndromic X-linked intellectual disability. Here, we describe an additional 25 patients from 11 families with variants in CUL4B. We identified nine different novel variants in these families and confirmed the pathogenicity of all nontruncating variants. Neuroimaging data, available for 15 patients, showed the presence of cerebral malformations in ten patients. The cerebral anomalies comprised malformations of cortical development (MCD), ventriculomegaly, and diminished white matter volume. The phenotypic heterogeneity of the cerebral malformations might result from the involvement of CUL-4B in various cellular pathways essential for normal brain development. Accordingly, we show that CUL-4B interacts with WDR62, a protein in which variants were previously identified in patients with microcephaly and a wide range of MCD. This interaction might contribute to the development of cerebral malformations in patients with variants in CUL4B.

Novel Mutations in the IRF6 Gene on the Background of Known Polymorphisms in Polish Patients with Orofacial Clefting

Objective

To examine the role of the IRF6 mutations in Polish families with Van der Woude syndrome and popliteal pterygium syndrome and to determine the effect of IRF6 single nucleotide polymorphisms (rs7552506, rs2013162, and rs2235375) on cleft lip and/or palate susceptibility.

Design

IRF6 mutation screening was performed by direct sequencing of all coding exons of the gene and their flanking intronic regions. Cosegregation analysis was performed to establish the relation of single nucleotide polymorphisms and cleft lip and/or palate phenotypes.

Patients

We screened the IRF6 gene in eight families with clinical recognition of Van der Woude syndrome and popliteal pterygium syndrome.

Results

In five families we identified pathogenic mutations, all affecting the DNA-binding or the protein-binding domain of IRF6. Two of the mutations were novel—a missense mutation Arg31Thr and a small deletion Trp40Glyfs∗23. In most cases we found also a haplotype of three single nucleotide polymorphisms—rs7552506, rs2013162, and rs2235375. The association of the single nucleotide polymorphisms and cleft lip and/or palate susceptibility has been previously published. The variants did not cosegregate with phenotype in examined families nor did they cosegregate with pathogenic mutations. The single nucleotide polymorphisms were deemed not causative, due to their presence in unaffected family members.

Conclusions

Two novel mutations (Arg31Thr and Trp40Glyfs∗23) in the IRF6 gene were identified to be causative for Van der Woude and popliteal pterygium syndromes. In the present study no association between the single nucleotide polymorphisms rs7552506, rs2013162, and rs2235375 and the cleft lip and/or palate phenotype was found. The hypothesis, whether the haplotype of the three single nucleotide polymorphisms was correlated with IRF6 expression level, demands further investigation.

General anesthesia soon after dialysis may increase postoperative hypotension - A pilot study

INTRODUCTION

Pilot study associating hemodialysis-to-general-anesthesia time interval and post-operative complications in hemodialysis patients to better define a more optimal pre-anesthetic waiting period.

METHODS

Pre-anesthetic and 48-hours post-anesthetic parameters (age, gender, body-mass-index, pre-operative ultrafiltrate, potassium, renal disease etiology, hemodialysis sessions per week, Acute Physiology and Chronic Health Evaluation-II score, Portsmouth-Physiologic and Operative Severity Score for the Enumeration of Mortality and Morbidity, American Society of Anesthesiologists physical status, Johns Hopkins Surgical Classification System Category, surgical urgency, intra-operative fluids, estimated blood loss, post-operative complications) were collected on chronic hemodialysis patients between 11/2009-12/2010. Continuous data were analyzed by Analysis of Variance or t-test. Bivariate data were analyzed by Fisher's Exact Test. Relative Risks/Confidence Intervals were calculated for statistically significant comparisons (p=0.05). Exclusion criteria were incomplete records, peritoneal dialysis, intra-operative hemodialysis, liver transplant, and cardiopulmonary bypass.

RESULTS

Patients were grouped by dialysis to anesthesia time interval: Group 1 >24 hours, Group 2 7-23.9 hours, Group 3 < 7 hours. Among Surgical Category 3-5 patients, hypotension was more common in Group 3 than Group 1 (63.6% vs 9.2%, p<0.0001, relative risk=6.9, confidence interval=3.0-15.7) or Group 2 (63.6% vs 17.3%, p=0.0002, relative risk=3.7, confidence interval=1.9-7.2). Other complications rates were not statistically significant. Disease and surgical severity scores, preoperative ultrafiltrate, and intra-operative fluids were not different.

CONCLUSIONS

Post-anesthetic hypotension within 48 hours was more common in those with < 7 hours interval between dialysis and anesthesia. Therefore, if surgical urgency permits, a delay of ≥7 hours may limit postoperative hypotension. More precise associations should be obtained through a prospective study.

Deficiency of manganese superoxide dismutase in hepatocytes disrupts zonated gene expression in mouse liver

The liver acinus displays a physiological periportal to perivenous oxygen gradient. This gradient was implicated to use reactive oxygen species (ROS) as mediators for the zonal gene expression. Mitochondria use oxygen and produce ROS, therefore they may contribute to the zonation of gene expression. To further elucidate this, we used the Cre-loxP system to generate a hepatocyte-specific null mutation of the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) in mice. We found that ROS levels were enhanced in livers of MnSOD(-/-) mice which were reduced in size and displayed signs of liver failure such as intracellular protein droplets, increased apoptotic bodies and Bax levels as well as multinuclear hepatocytes. Further, the zonation of glutamine synthetase, glucokinase and phosphoenolpyruvate carboxykinase was no longer preserved. We conclude that deficiency of mitochondrial MnSOD initiates a dysregulation of zonated gene expression in liver.

Heterozygous deficiency of manganese superoxide dismutase results in severe lipid peroxidation and spontaneous apoptosis in murine myocardium in vivo

To circumvent the early lethality of manganese superoxide dismutase (SOD2)-deficient mice, we have used a skin-specific strategy with introduction of loxP sites flanking exon 3 of the SOD2 gene. To our surprise, when breeding a female keratin 14 Cre transgenic mouse to a SOD2 "floxed" male mouse, due to keratin 14 promoter-driven Cre expression in the oocytes, all offspring were heterozygous for SOD2. In sharp contrast to initial publications on SOD2(+/-) mice, the herein reported mice on a mixed genetic background (C57BL/6 x 129/Ola) in their heterozygous state (SOD(+/-)) revealed distinct ultrastructural damage of the myocard, with swelling and disruption of mitochondria and accumulation of lipid droplets, increased nitrotyrosine formation, and lipid peroxidation as well as activation of apoptosis signaling pathways in the heart in vivo. Strikingly, and so far unreported, we found a substantial decrease in the activity of the cytosolic copper, zinc superoxide dismutase (SOD1) in the heart tissue of SOD2(+/-) mice, suggesting that the breakdown of mitochondrial membranes in the heart of SOD2(+/-) mice results in the enhanced release of superoxide anion radicals or derivatives thereof with subsequent inactivation of cytosolic SOD1. This model may be particularly suited to long-term studies on age-related heart failure as well as other age-related diseases and the polygenic base of tissue-specific responses to oxidative injury.

Enhanced plasminogen activator inhibitor-1 expression in transgenic mice with hepatocyte-specific overexpression of superoxide dismutase or glutathione peroxidase

In this study, we developed a double-transgenic mouse model allowing hepatocyte-specific and regulated expression of the redox-modifying enzymes copper/zinc superoxide dismutase (SOD) and glutathione peroxidase (GPX) by using a tetracycline-regulatable gene expression system. Within this system, the SOD and GPX level can be regulated deliberately by addition or removal of doxycycline hydrochloride to the drinking water. As reactive oxygen species (ROS) have been implicated in a number of pathological conditions, such as atherosclerosis, thrombosis, or liver fibrosis, processes that are also frequently associated with enhanced levels of plasminogen activator inhibitor-1 (PAI-1), it was the aim of the present study to investigate the influence of SOD and GPX overexpression on the regulation of PAI-1. PAI-1 mRNA and protein levels in tetracycline transactivator-dependent SOD-overexpressing double-transgenic mice reached values 2.5- to threefold above the normal mRNA level. By applying doxycycline, a deinduction of the PAI-1 levels was observed. By using the same protocol, PAI-1 mRNA and protein levels were enhanced in GPX double-transgenic mice, and again this response was blunted by the addition of doxycycline. These studies provide some new information regarding the role of ROS within the proteolytic processes in hepatocytes that require PAI-1.

Growth and development of tetracycline-resistant Chlamydia suis

Tetracycline (TET) is a front-line antibiotic for the treatment of chlamydial infections in both humans and animals, and the emergence of TET-resistant (Tet(r)) Chlamydia is of significant clinical importance. Recently, several Tet(r) chlamydial strains have been isolated from swine (Sus scrofa) raised in production facilities in Nebraska. Here, the intracellular development of two Tet(r) strains, R19 and R27, is characterized through the use of tissue culture and immunofluorescence. The strains grow in concentrations of up to 4 microg of TET/ml, while a TET-sensitive (Tet(s)) swine strain (S45) and a strain of the human serovar L2 (LGV-434) grow in up to 0.1 microg of TET/ml. Although inclusions form in the presence of TET, many contain large aberrant reticulate bodies (RBs) that do not differentiate into infectious elementary bodies. The percentage of inclusions containing typical developmental forms decreases with increasing TET concentrations, and at 3 microg of TET/ml 100% of inclusions contain aberrant RBs. However, upon removal of TET the aberrant RBs revert to typical RBs, and a productive developmental cycle ensues. In addition, inclusions were found that contained both C. suis R19 and Chlamydia trachomatis L2 after sequential infection, demonstrating that two biologically distinct chlamydial strains could both develop within a single inclusion.

10-Undecynoic acid, an inhibitor of cytochrome P450 4A1, inhibits ethanolamine-specific phospholipid base exchange reaction in rat liver microsomes

1,12-Dodecanedioic acid, the end-product of omega-hydroxylation of lauric acid, stimulates in a concentration dependent manner, phosphatidylethanolamine synthesis via ethanolamine-specific phospholipid base exchange reaction in rat liver endoplasmic reticulum. On the other hand, administration to rats of 10-undecynoic acid, a specific inhibitor of omega-hydroxylation reaction catalyzed by cytochrome P450 4A1, inhibits the ethanolamine-specific phospholipid base exchange activity by 30%. This is accompanied by a small but significant decrease in phosphatidylethanolamine content in the endoplasmic reticulum and inhibition of cytochrome P450 4A1. On the basis of these results it can be proposed that a functional relationship between cytochrome P450 4A1 and phosphatidylethanolamine synthesis exists in rat liver. Cytochrome P450 4A1 modulates the cellular level of lauric acid, an inhibitor of phospholipid synthesis. In turn, ethanolamine-specific phospholipid base exchange reaction provides molecular species of phospholipids, containing mainly long-chain polyunsaturated fatty acid moieties, required for the optimal activity of cytochrome P450 4A1.

10-Undecynoic acid, an inhibitor of cytochrome P450 4A1, inhibits ethanolamine-specific phospholipid base exchange reaction in rat liver microsomes

1,12-Dodecanedioic acid, the end-product of omega-hydroxylation of lauric acid, stimulates in a concentration dependent manner, phosphatidylethanolamine synthesis via ethanolamine-specific phospholipid base exchange reaction in rat liver endoplasmic reticulum. On the other hand, administration to rats of 10-undecynoic acid, a specific inhibitor of omega-hydroxylation reaction catalyzed by cytochrome P450 4A1, inhibits the ethanolamine-specific phospholipid base exchange activity by 30%. This is accompanied by a small but significant decrease in phosphatidylethanolamine content in the endoplasmic reticulum and inhibition of cytochrome P450 4A1. On the basis of these results it can be proposed that a functional relationship between cytochrome P450 4A1 and phosphatidylethanolamine synthesis exists in rat liver. Cytochrome P450 4A1 modulates the cellular level of lauric acid, an inhibitor of phospholipid synthesis. In turn, ethanolamine-specific phospholipid base exchange reaction provides molecular species of phospholipids, containing mainly long-chain polyunsaturated fatty acid moieties, required for the optimal activity of cytochrome P450 4A1.

Positive feedback between ethanolamine-specific phospholipid base exchange and cytochrome P450 activities in rat liver microsomes. The effect of clofibric acid

The results of the present investigation relate the effects of the nutritional state and administration of clofibric acid (CLA), a hypolipidaemic drug and peroxisomal proliferator, on phosphatidylethanolamine (PE) synthesis in rat liver and fatty acid metabolism. Fasting and CLA treatment of animals causes an increase in the amount of PE in endoplasmic reticulum (ER) membranes and mitochondria, as well as in the PE/phosphatidylcholine (PC) ratio. Moreover, the activity of the ethanolamine-specific phospholipid base exchange (PLBE) enzyme in liver ER membranes of fasted animals was enhanced by 75% in comparison to that of animals fed ad libitum. The effect of CLA treatment was additive to that of starvation; PE synthesis tested in vitro via the Ca2+-sensitive PLBE reaction increased 3-fold in comparison to rats fed ad libitum. This is confirmed by an increased Vmax for the reaction, but the affinity of the enzyme for ethanolamine was not significantly changed. These effects were accompanied by an enhanced expression of cytochrome P450 CYP4A1 isoform and elevated activity of the enzyme upon CLA administration. The stimulatory effect of CLA administration on the efficiency of the ethanolamine-specific PLBE reaction can be explained by elimination of lauric acid, a known inhibitor of de novo PE synthesis, during the course of omega-hydroxylation catalysed by CYP4A1, and by increased expression of the PLBE enzyme. The products of omega-hydroxylation of lauric acid, which are then converted by dehydrogenase to 1,12-dodecanedioic acid, did not significantly affect the in vitro synthesis of PE.

The induction of cytochrome P450 isoform, CYP4A1, by clofibrate coincides with activation of ethanolamine-specific phospholipid base exchange reaction in rat liver microsomes

Administration of a hypolipidaemic drug, clofibrate, to rats resulted, 24 h after a single intraperitoneal injection (250 mg/kg body weight), in pronounced enhancement of the rate of phosphatidylethanolamine (PE) synthesis via the PE-specific base exchange (PEBE) reaction in liver microsomes. This was accompanied by 3.4-fold activation of microsomal omega-hydroxylation of lauric acid by cytochrome P450 4A1 isoform (CYP4A1) and an increase in the protein content of this isoform in endoplasmic reticulum (ER) membranes. Since PE represents a class of phospholipids (PL) prerequisite for proper functioning of CYP4A1, and the PEBE reaction is an inducible pathway of PL synthesis in hepatocytes under metabolic stress, one may speculate that this reaction is switched on when extensive remodelling of PL molecular species or/and massive synthesis of lipid bilayer components for membrane assembly is required.

The induction of cytochrome P450 isoform, CYP4A1, by clofibrate coincides with activation of ethanolamine-specific phospholipid base exchange reaction in rat liver microsomes

Administration of a hypolipidaemic drug, clofibrate, to rats resulted, 24 h after a single intraperitoneal injection (250 mg/kg body weight), in pronounced enhancement of the rate of phosphatidylethanolamine (PE) synthesis via the PE-specific base exchange (PEBE) reaction in liver microsomes. This was accompanied by 3.4-fold activation of microsomal omega-hydroxylation of lauric acid by cytochrome P450 4A1 isoform (CYP4A1) and an increase in the protein content of this isoform in endoplasmic reticulum (ER) membranes. Since PE represents a class of phospholipids (PL) prerequisite for proper functioning of CYP4A1, and the PEBE reaction is an inducible pathway of PL synthesis in hepatocytes under metabolic stress, one may speculate that this reaction is switched on when extensive remodelling of PL molecular species or/and massive synthesis of lipid bilayer components for membrane assembly is required.

Membrane integrity and phospholipid movement influence the base exchange reaction in rat liver microsomes

Properties of Ca(2+)-stimulated incorporation of amincalcohols, serine and ethanolamine, into phospholipids, and factors regulating the reaction were studied in endoplasmic reticulum membranes isolated from rat liver. In contrast to apparent K(m) values for either aminoalcohol, maximal velocities of the reaction were significantly affected by Ca2+ concentration. No competition between these two soluble substrates used at equimolar concentrations close to their K(m) values was observed, suggesting the existence of two distinct phospholipid base exchange activities. The enzyme utilizing the electrically neutral serine was not sensitive to changes of membrane potential evoked by valinomycin in the presence of KCl. On the other hand, when positively charged ethanolamine served as a substrate, the enzyme activity was inhibited by 140 mM KCl and this effect was reversed by valinomycin. The rates of inhibition of phospholipid base exchange reactions by various thiol group modifying reagents were also found to differ. Cd2+ and lipophylic p-chloromercuribenzoic acid at micromolar concentrations were most effective. It can be suggested that -SH groups located within the hydrophobic core of the enzymes molecules are essential for the recognition of membrane substrates. However, the influence of the -SH group modifying reagents on the protein-facilitated phospholipid motion across endoplasmic reticulum membranes can not be excluded, since an integral protein-mediated transverse movement of phospholipids within the membrane bilayer and Ca(2+)-mediated changes in configuration of the phospholipid polar head groups seem to be a regulatory step of the reaction. Indeed, when the membrane integrity was disordered by detergents or an organic solvent, the reaction was inhibited, although not due to the transport of its water-soluble substrates is affected, but due to modulation of physical state of the membrane bilayer and, in consequence, the accessibility of phospholipid molecules.

Nonenzymatically evoked and cytochrome P450-dependent lipid peroxidation inhibits synthesis of phosphatidylethanolaminevia the ethanolamine base exchange reaction in rat liver microsomes

In the present study the relationship between lipid peroxidation, changes in the redox state of membrane and phosphatidylethanolamine (PE) synthesis via base exchange reaction in rat liver microsomes was investigated. It was found that PE synthesis is enhanced in the presence of antioxidants, butylated hydroxytoluene (BHT), or unsaturated free fatty acids. Prooxidants, tert-butyl hydroxyperoxide (BHP), ferrous ions combined with ascorbate or NADPH (via cytochrome P450-dependent proteins), increased the amount of lipid peroxidation products in the membrane, and in consequence inhibited the reaction. The effect of BHP was fully reversed by reduced glutathione and dithiothreitol (DTT), whereas the effect of other compounds could be reversed only by BHT. In contrast, a reversal of the inhibitory effect of cadmium ions on base exchange activity was observed in the presence of DTT, but not BHT. Therefore, both the -SH/-S-S- ratio in the membrane, affected by BHP and cadmium ions, and the lipid hydroxyperoxides (rather than aldehydes), generated by ferrous ions and ascorbate or NADPH, are equally responsible for the inactivation of the ethanolamine base exchange enzyme in rat liver microsomes. This may suggest that the synthesis of PE via the base exchange reaction may be considered an element of the superfine cellular machinery involved in the repair of damage to unsaturated fatty acid chains of phospholipids caused by reactive oxygen species under oxidative stress.