p53-dependent stimulation of redox-related genes in the lymphoid organs of γ-irradiated mice—identification of Haeme-oxygenase 1 as a direct p53 target gene

Recent data showed that p53 stimulates the expression of genes encoding not only pro- but also antioxidant enzymes. It was suggested that antioxidant genes could be induced under physiologic levels of stress while the prooxidant ones respond to higher level of stress. Results presented in this article illustrate an additional degree of complexity. We show that the expression of Haeme-oxygenase 1 (HO-1), a stress-inducible gene that codes for an enzyme having antioxidant properties, is stimulated in a p53-dependent manner in the thymus and spleen of irradiated mice. We prove that HO-1 is a direct p53 target gene by showing that the p53RE identified within human and mouse genes is specifically bound by p53. The threshold of irradiation dose required to induce a significant response of HO-1 in the lymphoid organs of the irradiated mice is higher than that for Waf1/p21 that encodes an universal inhibitor of cell cycle. Moreover, induction of HO-1 occurs later than that of Waf1/p21. Finally, the higher stimulation of HO-1 is reached when Waf1/p21 stimulation starts to decrease

Cerebral and Peripheral Changes Occurring in Nitric Oxide (NO) Synthesis in a Rat Model of Sleeping Sickness: Identification of Brain iNOS Expressing Cells

International audienceBACKGROUND: The implication of nitric oxide (NO) in the development of human African trypanosomiasis (HAT) using an animal model, was examined. The manner by which the trypanocidal activity of NO is impaired in the periphery and in the brain of rats infected with Trypanosoma brucei brucei (T. b. brucei) was analyzed through: (i) the changes occurring in NO concentration in both peripheral (blood) and cerebral compartments; (ii) the activity of nNOS and iNOS enzymes; (iii) identification of the brain cell types in which the NO-pathways are particularly active during the time-course of the infection. METHODOLOGY/PRINCIPAL FINDINGS: NO concentration (direct measures by voltammetry) was determined in central (brain) and peripheral (blood) compartments in healthy and infected animals at various days post-infection: D5, D10, D16 and D22. Opposite changes were observed in the two compartments. NO production increased in the brain (hypothalamus) from D10 (+32%) to D16 (+71%), but decreased in the blood from D10 (-22%) to D16 (-46%) and D22 (-60%). In parallel with NO measures, cerebral iNOS activity increased and peaked significantly at D16 (up to +700%). However, nNOS activity did not vary. Immunohistochemical staining confirmed iNOS activation in several brain regions, particularly in the hypothalamus. In peritoneal macrophages, iNOS activity decreased from D10 (-83%) to D16 (-65%) and D22 (-74%) similarly to circulating NO. CONCLUSION/SIGNIFICANCE: The NO changes observed in our rat model were dependent on iNOS activity in both peripheral and central compartments. In the periphery, the NO production decrease may reflect an arginase-mediated synthesis of polyamines necessary to trypanosome growth. In the brain, the increased NO concentration may result from an enhanced activity of iNOS present in neurons and glial cells. It may be regarded as a marker of deleterious inflammatory reactions

Malignant astrocyte swelling and impaired glutamate clearance drive the expansion of injurious spreading depolarization foci

Spreading depolarizations (SDs) indicate injury progression and predict worse clinical outcome in acute brain injury. We demonstrate in rodents that acute brain swelling upon cerebral ischemia impairs astroglial glutamate clearance and increases the tissue area invaded by SD. The cytotoxic extracellular glutamate accumulation (>15 mu M) predisposes an extensive bulk of tissue (4-5 mm(2)) for a yet undescribed simultaneous depolarization (SiD). We confirm in rat brain slices exposed to osmotic stress that SiD is the pathological expansion of prior punctual SD foci (0.5-1 mm(2)), is associated with astrocyte swelling, and triggers oncotic neuron death. The blockade of astrocytic aquaporin-4 channels and Na+/K+/Cl- co-transporters, or volume-regulated anion channels mitigated slice edema, extracellular glutamate accumulation (<10 mu M) and SiD occurrence. Reversal of slice swelling by hyperosmotic mannitol counteracted glutamate accumulation and prevented SiD. In contrast, inhibition of glial metabolism or inhibition of astrocyte glutamate transporters reproduced the SiD phenotype. Finally, we show in the rodent water intoxication model of cytotoxic edema that astrocyte swelling and altered astrocyte calcium waves are central in the evolution of SiD. We discuss our results in the light of evidence for SiD in the human cortex. Our results emphasize the need of preventive osmotherapy in acute brain injury

Cerebral Changes Occurring in Arginase and Dimethylarginine Dimethylaminohydrolase (DDAH) in a Rat Model of Sleeping Sickness

Involvement of nitric oxide (NO) in the pathophysiology of human African trypanosomiasis (HAT) was analyzed in a HAT animal model (rat infected with Trypanosoma brucei brucei). With this model, it was previously reported that trypanosomes were capable of limiting trypanocidal properties carried by NO by decreasing its blood concentration. It was also observed that brain NO concentration, contrary to blood, increases throughout the infection process. The present approach analyses the brain impairments occurring in the regulations exerted by arginase and N(G), N(G)-dimethylarginine dimethylaminohydrolase (DDAH) on NO Synthases (NOS). In this respect: (i) cerebral enzymatic activities, mRNA and protein expression of arginase and DDAH were determined; (ii) immunohistochemical distribution and morphometric parameters of cells expressing DDAH-1 and DDAH-2 isoforms were examined within the diencephalon; (iii) amino acid profiles relating to NOS/arginase/DDAH pathways were established.Arginase and DDAH activities together with mRNA (RT-PCR) and protein (western-blot) expressions were determined in diencephalic brain structures of healthy or infected rats at various days post-infection (D5, D10, D16, D22). While arginase activity remained constant, that of DDAH increased at D10 (+65%) and D16 (+51%) in agreement with western-blot and amino acids data (liquid chromatography tandem-mass spectrometry). Only DDAH-2 isoform appeared to be up-regulated at the transcriptional level throughout the infection process. Immunohistochemical staining further revealed that DDAH-1 and DDAH-2 are contained within interneurons and neurons, respectively.In the brain of infected animals, the lack of change observed in arginase activity indicates that polyamine production is not enhanced. Increases in DDAH-2 isoform may contribute to the overproduction of NO. These changes are at variance with those reported in the periphery. As a whole, the above processes may ensure additive protection against trypanosome entry into the brain, i.e., maintenance of NO trypanocidal pressure and limitation of polyamine production, necessary for trypanosome growth

The neurogene BTG2TIS21/PC3 is transactivated by Np73 via p53 specifically in neuroblastoma cells

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In vivo brain nitric oxide detection using fluorinated xerogel-coated carbon fiber microelectrodes

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In vivo brain nitric oxide detection using fluorinated xerogel-coated carbon fiber microelectrodes

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Microelectrode Biosensors for in vivo Analysis of Brain Interstitial Fluid

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Electrochemical Nitric Oxide Microsensors Based on a Fluorinated Xerogel Screening Layer for in Vivo Brain Monitoring

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Modifications métaboliques liées aux dépolarisations corticales envahissantes après un traumatisme crânien sévère chez le rat : une origine des crises métaboliques ?

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