Hypoxia-reoxygenation affects whole-genome expression in the newborn eye.

PURPOSE: Resuscitation of newborns is one of the most frequent procedures in neonatal medicine. The use of supplementary oxygen during resuscitation of the asphyxiated newborn has been shown to be detrimental to vulnerable tissues. We wanted to assess transcriptional changes in ocular tissue after the acute use of oxygen in the delivery room in a hypoxia-reoxygenation model of the newborn mouse. METHODS: C57BL/6 mice (n = 57), postnatal day 7, were randomized to receive either 120 minutes of hypoxia, at 8% O2, followed by 30 minutes of reoxygenation with 21, 40, 60, or 100% O2 or to normoxia followed by 30 minutes of 21% or 100% O2. Whole ocular homogenates were analyzed by Affymetrix 750k expression array, and RT-PCR was performed for validation. Bayesian analysis of variance for microarray data (BAMarray) was used to identify single significant genes, and Gene Set Enrichment Analysis (GSEA) was applied to reveal significant pathway systems. RESULTS: In total, ∼ 92% of the gene expression changes were altered in response to reoxygenation with 60% or 100% O2 compared to expression at the lower percentages of 21% and 40%. After 100% O2 treatment, genes involved in inflammation (Ccl12), angiogenesis (Igfr1, Stat3), and metabolism (Hk2) were upregulated. Pathway analyses after hypoxia-reoxygenation revealed significant alterations of six pathways which included apoptosis, TGF-beta signaling, oxidative phosphorylation, voltage-gated calcium channel complex, mitochondrion, and regulation of RAS protein signal transduction. CONCLUSIONS: Hypoxia-reoxygenation can induce immediate transcriptional responses in ocular tissue involving inflammation, angiogenesis, energy failure, and Ras signaling.

Transcriptome profiling of the newborn mouse brain after hypoxia-reoxygenation: hyperoxic reoxygenation induces inflammatory and energy failure responsive genes.

BACKGROUND: Supplemental oxygen used during resuscitation can be detrimental to the newborn brain. The aim was to determine how different oxygen therapies affect gene transcription in a hypoxia-reoxygenation model. METHODS: C57BL/6 mice (n = 56), postnatal day 7, were randomized either to 120 min of hypoxia 8% O2 followed by 30 min of reoxygenation with 21, 40, 60, or 100% O2, or to normoxia followed by 30 min of 21 or 100% O2. Affymetrix 750k expression array was applied with RT-PCR used for validation. Histopathology and immunohistochemistry 3 d after hypoxia-reoxygenation compared groups reoxygenated with 21 or 100% O2 with normoxic controls (n = 22). RESULTS: In total, ~81% of the gene expression changes were altered in response to reoxygenation with 60 or 100% O2 and constituted many inflammatory-responsive genes (i.e., C5ar2, Stat3, and Ccl12). Oxidative phosphorylation was downregulated after 60 or 100% O2. Iba1(+) cells were significantly increased in the striatum and hippocampal CA1 after both 21 and 100% O2. CONCLUSION: In the present model, hypoxia-reoxygenation induces microglial accumulation in subregions of the brain. The transcriptional changes dominating after applying hyperoxic reoxygenation regimes include upregulating genes related to inflammatory responses and suppressing the oxidative phosphorylation pathway.

Transcriptome profiling of the newborn mouse lung after hypoxia and reoxygenation: hyperoxic reoxygenation affects mTOR signaling pathway, DNA repair, and JNK-pathway regulation.

BACKGROUND: The use of oxygen in acute treatment of asphyxiated term newborns is associated with increased mortality. It is unclear how hyperoxic reoxygenation after hypoxia affects transcriptional changes in the newborn lung. METHODS: On postnatal day 7, C57BL/6 mice (n = 62) were randomized to 120-min hypoxia (fraction of inspired oxygen (FiO2) 0.08) or normoxia. The hypoxia group was further randomized to reoxygenation for 30 min with FiO2 0.21, 0.40, 0.60, or 1.00, and the normoxia group to FiO2 0.21 or 1.00. Transcriptome profiling was performed on homogenized lung tissue using the Affymetrix 750k expression array, and validation was carried out by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS: The hypoxia-reoxygenation model induced hypoxia-inducible factor 1 (HIF-1) targets like Vegfc, Adm, and Aqp1. In total, ~70% of the significantly differentially expressed genes were detected in the two high hyperoxic groups (FiO2 0.60 and 1.00). Reoxygenation with 100% oxygen after hypoxia uniquely upregulated Gadd45g, Dusp1, Peg3, and Tgm2. Pathway analysis identified mammalian target of rapamycin (mTOR) signaling pathway, DNA repair, c-jun N-terminal kinase (JNK)-pathway regulation, and cell cycle after hyperoxic reoxygenation was applied. CONCLUSION: Acute hypoxia induces HIF-1 targets independent of the reoxygenation regime applied. Hyperoxic reoxygenation affects pathways regulating cell growth and survival. DNA-damage-responsive genes are restricted to reoxygenation with 100% oxygen.

Resuscitation of newborn piglets. short-term influence of FiO2 on matrix metalloproteinases, caspase-3 and BDNF.

BACKGROUND: Perinatal hypoxia-ischemia is a major cause of mortality and cerebral morbidity, and using oxygen during newborn resuscitation may further harm the brain. The aim was to examine how supplementary oxygen used for newborn resuscitation would influence early brain tissue injury, cell death and repair processes and the regulation of genes related to apoptosis, neurodegeneration and neuroprotection. METHODS AND FINDINGS: Anesthetized newborn piglets were subjected to global hypoxia and then randomly assigned to resuscitation with 21%, 40% or 100% O(2) for 30 min and followed for 9 h. An additional group received 100% O(2) for 30 min without preceding hypoxia. The left hemisphere was used for histopathology and immunohistochemistry and the right hemisphere was used for in situ zymography in the corpus striatum; gene expression and the activity of various relevant biofactors were measured in the frontal cortex. There was an increase in the net matrix metalloproteinase gelatinolytic activity in the corpus striatum from piglets resuscitated with 100% oxygen vs. 21%. Hematoxylin-eosin (HE) staining revealed no significant changes. Nine hours after oxygen-assisted resuscitation, caspase-3 expression and activity was increased by 30-40% in the 100% O(2) group (n = 9/10) vs. the 21% O(2) group (n = 10; p<0.04), whereas brain-derived neurotrophic factor (BDNF) activity was decreased by 65% p<0.03. CONCLUSIONS: The use of 100% oxygen for resuscitation resulted in increased potentially harmful proteolytic activities and attenuated BDNF activity when compared with 21%. Although there were no significant changes in short term cell loss, hyperoxia seems to cause an early imbalance between neuroprotective and neurotoxic mechanisms that might compromise the final pathological outcome.

5-fluorouracil-induced death of Jurkat T-cells--a role for caspases and MCL-1.

5-Fluorouracil (5-FU) is frequently used in cancer treatment. Previous studies with 5-FU suggest that proapoptotic protein BAX and tumor suppressor protein TP53 are central factors in this process. As the leukemic T cell line Jurkat E6 has mutations in both these genes, we investigated a possible activation of alternative death pathways following 5-FU treatment. Here we show that 5-FU triggers apoptosis in Jurkat cells in a dose-dependent manner. Death responses were only moderately attenuated in the presence of a general caspase inhibitor. However, flow cytometric analysis showed activation of caspase 3 and a slight increase in ROS generation in a time- and dose-dependent manner. Furthermore, we observed 5-FU induced PARP cleavage and notably, reduced expression of antiapoptotic MCL-1L associated with the appearance of proapoptotic MCL-1S. Our results demonstrate the activation of alternative death pathways following treatment with 5-FU, despite mutations in the TP53 and BAX genes.

Resuscitation of hypoxic newborn piglets with supplementary oxygen induces dose-dependent increase in matrix metalloproteinase-activity and down-regulates vital genes.

The optimal oxygen concentration for newborn resuscitation is still discussed. Oxygen administration during reoxygenation may induce short- and long-term pathologic changes via oxidative stress and has been associated to later childhood cancer. The aim was to study changes in oxidative stress-associated markers in liver and lung tissue of newborn pigs after acute hypoxia followed by reoxygenation for 30 min with 21, 40, or 100% oxygen compared with room air or to ventilation with 100% oxygen without preceding hypoxia. Nine hours after resuscitation, we found a dose-dependent increase in the matrix metalloproteinase gelatinase activity in liver tissue related to percentage oxygen supply by resuscitation (100% versus 21%; p = 0.002) pointing at more extensive tissue damage. Receiving 100% oxygen for 30 min without preceding hypoxia decreased the expression of VEGFR2 and TGFBR3 mRNA in liver tissue, but not in lung tissue. MMP-, VEGF-, and TGFbeta-superfamily are vital for the development, growth, and functional integrity of most tissues and our data rise concern about both short- and long-term consequences of even a brief hyperoxic exposure.

Inflammatory receptors and pathways in human NT2-N neurons during hypoxia and reoxygenation. Impact of acidosis.

Cytokines are released in response to brain injury and inflammation. By binding to receptors, they can cause, exacerbate or inhibit cellular injury and repair. We studied RNA expression of cytokine receptors and members of inflammatory pathways in human NT2-N neurons during 3 h of hypoxia and glucose deprivation followed by 21 h of reoxygenation, and the impact of acidosis. Right after acidotic hypoxia, RNA of IL-10RA and CXCR4 were significantly increased relative to acidotic control, while Bcl-2 and Bcl-xL were significantly decreased. After 21 h of neutral reoxygenation after neutral hypoxia, there was a significant increase in RNA of CXCR1 (relative quantification (RQ)=4.1, p<0.05), CXCR2 (3.6, p<0.05), CCR2 (3.8, p<0.05), Hsp70 (2.4, p<0.05), HIF-1alpha (1.5, p<0.001), TRAF6 (1.3, p<0.05) and TNFR1 (1.6, p<0.05). After 21 h of acidotic reoxygenation after acidotic hypoxia, we found a significant increase in RNA of IL-1R1, IL-10RA, CXCR4 and Hsp70 compared to control, and a significant decrease in FAS and TRAF6. There was a significant increase in Bax expression and a significant decrease in Bcl-2 and Bcl-xL expression in three out of four pH groups after 21 h of reoxygenation. Acidotic, relative to neutral, hypoxia and reoxygenation also influenced the expression of various genes. We conclude that inflammatory receptors and pathways are activated during hypoxia and reoxygenation in NT2-N neurons, and that this activation is pH dependent. This supports the concept that inflammatory pathways play a role in cerebral hypoxic-ischemic damage, and that they may represent important pharmacological targets.

Differential development of vesicular glutamate transporters in brain: an in vitro study of cerebellar granule cells.

The cerebellar granule cells have been extensively used for studies on metabolism, neurotransmission and neurotoxicology, since they can easily be grown in cultures. However, knowledge about the development of different proteins essential for synaptic transmission in these cells is lacking. This study has characterized the developmental profiles of the vesicular glutamate transporters (VGLUTs) and the synaptic vesicle proteins synapsins and synaptophysin in cerebellar granule cells and in co-cultures containing both granule cells and astrocytes. The protein levels of VGLUT2 decreased by approximately 70% from days 2 to 7 in vitro, whereas the levels of VGLUT1 increased by approximately 95%. Protein levels of synapsin I, synapsin IIIa and synaptophysin showed a developmental pattern similar to VGLUT1 while synapsin II and VGLUT3 were absent. The mRNA expressions of VGLUT1 and VGLUT2 were in accordance with the protein levels. The results indicate both that cerebellar granule cells are mature at approximately 7 days in vitro, and that the up-regulation of VGLUT1 and down-regulation of VGLUT2 in cerebellar granule cells are both independent of surrounding astrocytes and neuronal input. The results of this study are discussed in relation to general developmental profiles of VGLUTs in other brain regions.

Absence of synapsin I and II is accompanied by decreases in vesicular transport of specific neurotransmitters.

Studies of synapsin-deficient mice have shown decreases in the number of synaptic vesicles but knowledge about the consequences of this decrease, and which classes of vesicles are being affected, has been lacking. In this study, glutamatergic, GABAergic and dopaminergic transport has been analysed in animals where the genes encoding synapsin I and II were inactivated. The levels of the vesicular glutamate transporter (VGLUT) 1, VGLUT2 and the vesicular GABA transporter (VGAT) were decreased by approximately 40% in adult forebrain from mice devoid of synapsin I and II, while vesicular monoamine transporter (VMAT) 2 and VGLUT3 were present in unchanged amounts compared with wild-type mice. Functional studies on synaptic vesicles showed that the vesicular uptake of glutamate and GABA was decreased by 41 and 23%, respectively, while uptake of dopamine was unaffected by the lack of synapsin I and II. Double-labelling studies showed that VGLUT1 and VGLUT2 colocalized fully with synapsin I and/or II in the hippocampus and neostriatum, respectively. VGAT showed partial colocalization, while VGLUT3 and VMAT2 did not colocalize with either synapsin I or II in the brain areas studied. In conclusion, distinct vesicular transporters show a variable degree of colocalization with synapsin proteins and, hence, distinct sensitivities to inactivation of the genes encoding synapsin I and II.

Liver cells respond to Aspergillus fumigatus with an increase in C3 secretion and C3 gene expression as well as an expression increase in TLR2 and TLR4.

Fungal infections by molds like Aspergillus fumigatus are an increasing health problem which can be fatal in immuno-compromised patients. In healthy individuals, these infections are easily eliminated by the innate and acquired immune system. Complement factor 3 (C3) has a key place within the complement cascade and C3 RNA expression can therefore be used to monitor an impending immune response. Employing a liver cell line (HepG2) as a model system, we have examined their responses to A. fumigatus or beta-glucan, a major component of the fungal wall. C3 RNA expression was increased after stimulation with both LPS and A. fumigatus as well as after incubation with beta-glucan, although with different kinetics. C3 protein release into the supernatant followed an inverse bell-shaped curve when cells were incubated with A. fumigatus or beta-glucan while during LPS stimulation, the release was more stable. HepG2 cells also express Toll-like receptors (TLRs) and both for TLR2 and TLR4, an expression increase was found. These data demonstrate that liver cells are able to react specifically to a fungal pathogen without the help of Kupffer cells.

The colon mitosis-inhibitor pyroglutamyl-histidyl-glycine alters expression of immediate-early cancer-related genes in HT-29 cells.

BACKGROUND: The intestinal mitosis-inhibiting peptide pyroglu-His-GlyOH (pEHG), inhibits normal intestinal epithelial cells and the human colon adenocarcinoma cell line HT-29 and increases the expression of c-fos (1). In this study, we investigated the mechanisms of the growth-inhibiting effects of pEHG. MATERIALS AND METHODS: cDNA expression array was hybridized with cDNA from HT-29 cells exposed to pEHG or control. The results were confirmed with Northern blot or real-time PCR. RESULTS: pEHG(1 nM) provoked a significant increase in the expression of the early growth response protein 1 (egr-1) after an incubation of 20 minutes, while c-fos was confirmed up-regulated by the same treatment. We further studied the expression of fosB, c-jun and junB, in the AP-1 complex. fosB was up-regulated 20-fold, but only minor effects on jun variants were observed. CONCLUSION: pEHG stimulates the gene expression of some immediate-early transcription factors involved in cell proliferation.