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Biomedical subjects

Myriam Bernaudin

Publications and source records attributed to Myriam Bernaudin.

14 recordsLinked to original sources
PubMed2006

Synergistic effects of CoCl(2) and ROCK inhibition on mesenchymal stem cell differentiation into neuron-like cells.

Bone-marrow-derived mesenchymal stem cells (MSCs) constitute an interesting cellular source to promote brain regeneration after neurodegenerative diseases. Recently, several studies suggested that oxygen-dependent gene expression is of crucial importance in governing the essential steps of neurogenesis such as cell proliferation, survival and differentiation. In this context, we analysed the effect of the HIF-1 (hypoxia inducible factor-1) activation-mimicking agent CoCl(2) on MSCs. CoCl(2) treatment increased the expression of the anti-proliferative gene BTG2/PC3 and decreased cyclin D1 expression. Expression of HIF-1alpha and its target genes EPO, VEGF and p21 was also upregulated. These changes were followed by inhibition of cell proliferation and morphological changes resulting in neuron-like cells, which had increased neuronal marker expression and responded to neurotransmitters. Echinomycin, a molecule inhibiting HIF-1 DNA-binding activity, blocked the CoCl(2) effect on MSCs. Additionally, by using Y-27632, we demonstrated that Rho kinase (ROCK) inhibition potentiated CoCl(2)-induced MSC differentiation in particular into dopaminergic neuron-like cells as attested by its effect on tyrosine hydroxylase expression. Altogether, these results support the ability of MSCs to differentiate into neuron-like cells in response to CoCl(2), an effect that might act, in part, through HIF-1 activation and cell-cycle arrest, and which is potentiated by inhibition of ROCK.

Amides↗
PubMed2006

Long-term functional outcome following transient middle cerebral artery occlusion in the rat: correlation between brain damage and behavioral impairment.

The assessment of both histological and functional long-term outcomes after cerebral ischemia is increasingly recommended for preclinical studies. Whereas correlations between behavioral impairments and primary ischemic lesion are documented, little is known about their relationships with remote nonischemic regions that undergo secondary degeneration, such as the thalamus. Anesthetized rats were subjected to mild (30 min) or severe (60 min) occlusion of the middle cerebral artery. Two months after ischemia, sensorimotor behavior was assessed according to the neurological score, limb-placing, adhesive-removal, and staircase tests; the final histological lesion was measured after this assessment. Cortical damage was correlated to all transient and long-lasting sensorimotor deficits, whereas striatal lesion was more consistently reflected by the forelimb-placing reflexes and adhesive-removal motor deficits. By contrast, the thalamic atrophy was not correlated to early neurological impairment, but rather to the late sensory deficit at the adhesive-removal test and to the skilled forepaw reaching alteration at the staircase test. This suggests that thalamus contributes, albeit moderately, to the ischemia-induced long-lasting sensorimotor deficits, some of which represent relevant targets for therapeutic interventions.

Analysis of Variance↗
PubMed2006

Delayed administration of deferoxamine reduces brain damage and promotes functional recovery after transient focal cerebral ischemia in the rat.

The mechanisms underlying functional recovery after stroke are poorly understood. Brain-adaptive responses to the hypoxic stress elicited by ischemia could contribute to these mechanisms. Indeed, hypoxia-inducible factor-1 (HIF-1), one of the main transcriptional factors regulated by oxygen level, increases the expression of several beneficial genes such as erythropoietin, glucose transporter-1 and vascular endothelial growth factor. In order to strengthen the expression of these hypoxia-inducible factors, we administered deferoxamine, an iron chelator known to stabilize HIF-1alpha protein expression, and examined its effects on the functional deficits induced by ischemia. Anesthetized Sprague-Dawley rats were subjected to 60 min of intraluminal occlusion of the middle cerebral artery. Chronic deferoxamine treatment (300 mg/kg, s.c.), or its vehicle, started 24 h after ischemia and was continued bi-weekly until the animals were killed. Sensorimotor deficits were periodically assessed over 2 months, and at this end point, the lesion volume was determined by histology. Treatment with deferoxamine significantly decreased the size of brain damage (-28%) after ischemia and improved behavioral recovery. Indeed, neurological score and sensorimotor performances in the adhesive removal test recovered earlier in the deferoxamine-treated animals. Moreover, the long-lasting skilled forepaw reaching deficits were attenuated by deferoxamine. Although an antioxidant effect of deferoxamine cannot be excluded, the hypothesis that its beneficial effects could be mediated by an increase in HIF-1 target genes merits further investigations. Our data suggest that delayed administration of deferoxamine could represent an interesting therapeutical approach to treat focal cerebral ischemia.

Animals↗
PubMed2006

Erythropoietin, a cytoprotective and regenerative cytokine, and the hypoxic brain.

Hypoxia and ischemia in the brain often result in brain dysfunctions and neuronal death during both the neonatal and adult periods. Though the mechanisms contributing to brain injury secondary to hypoxia-ischemia are more clearly defined, there are still no pharmacological treatments available to reduce cell death in the ischemic brain. This review highlights the beneficial effects of hypoxia-inducible factors, such as the transcriptional factor hypoxia-inducible factor-1 and its target genes, as both cytoprotective and regenerative factors, and focuses in particular on one of the most well-known: erythropoietin. Altogether, the data presented in this review suggest that further insights into the role of hypoxia-inducible factors would help develop promising strategies to improve the outcome of hypoxia/ischemia-related brain pathologies.

Animals↗
PubMed2005

Effect of hypoxic preconditioning on brain genomic response before and following ischemia in the adult mouse: identification of potential neuroprotective candidates for stroke.

The aim of the present study is to better understand oxygen-sensitive adaptative pathways underlying the hypoxic preconditioning-induced protection of the brain against ischemia. Using oligonucleotide microarrays, we examined the brain genomic response of adult mice following hypoxia preconditioning (8% O2 for 1 or 6 h of hypoxia with reoxygenation 12, 18, 24 h or 72 h) and ischemia (6 h), preceeded (tolerant state) or not, by preconditioning. Real-time PCR was used to validate the results. Most gene expression increases occurred during hypoxia, including those of HIF-1-dependent genes (RTP801, AM, VEGF, p21, GLUT-1), early response genes (IER3) and transcriptional factors (ATF3, C/EBPdelta). A second wave of changes occurred 24 h after reoxygenation (S100A5, TH, Calretinin, PBX3). A third one occurred during ischemia itself, revealing that hypoxic preconditioning modifies the brain genomic response to ischemia. In addition, we show that some identical genes are overexpressed by hypoxia in both neonatal and adult brains (VEGF, EPO, GLUT-1, AM, MTs, C/EBPdelta).

Age Factors↗
PubMed2005

Expression of erythropoietin and erythropoietin receptor in non-small cell lung carcinomas.

PURPOSE: Expression of erythropoietin (Epo) and its receptor (Epo-R) has been shown in various normal and neoplastic nonhematopoietic tissues. This study, in non-small cell lung carcinoma, was designed to investigate the previously unreported expression of Epo and Epo-R as well as hypoxia-inducible factor-1alpha (HIF-1alpha), which is known to control Epo expression. EXPERIMENTAL DESIGN: Samples from lung squamous cell carcinomas (n = 17) and adenocarcinomas (n = 12) were obtained from patients undergoing curative surgery. mRNA transcripts of Epo, Epo-R, soluble Epo-R (sEpo-R), HIF-1alpha, and factor inhibiting HIF-1 (FIH-1) were evaluated by reverse transcription-PCR, whereas localization of Epo, Epo-R, and HIF-1alpha was assessed by immunohistochemistry. RESULTS: Epo, Epo-R, sEpo-R, HIF-1alpha, and FIH-1 transcripts were detected by reverse transcription-PCR in all samples tested, but with heterogeneous levels of expression for Epo, Epo-R, and sEpo-R. Coordinated levels of mRNA were observed for HIF-1alpha and FIH-1.Epo was detected in carcinomatous cells by immunohistochemistry in 50% of samples and Epo-R was detected in 96% of samples. Co-expression of Epo and Epo-R was observed on contiguous sections from 50% of tumors. HIF-1alpha was immunolocalized in 80% of non-small cell lung carcinomas. CONCLUSION: Epo-R was expressed in almost all samples and Epo was expressed in one half of samples on immunohistochemistry and in 100% of samples by mRNA detection, suggesting a potential paracrine and/or autocrine role of endogenous Epo in non-small cell lung carcinoma. The detection of stabilized HIF-1alpha suggests a possible role in Epo expression. Moreover, in the light of these results, the potential interactions between therapeutic recombinant Epo and the putative neoplastic Epo/Epo-R signaling pathways must be considered.

Carcinoma, Non-Small-Cell Lung↗
PubMed2005

VEGF-induced BBB permeability is associated with an MMP-9 activity increase in cerebral ischemia: both effects decreased by Ang-1.

After cerebral ischemia, angiogenesis, by supplying for the deficient perfusion, may be a beneficial process for limiting neuronal death and promoting tissue repair. In this study, we showed that the combination of Ang-1 and vascular endothelial growth factor (VEGF) provides a more adapted therapeutic strategy than the use of VEGF alone. Indeed, we showed on a focal ischemia model that an early administration of VEGF exacerbates ischemic damage, because of its effects on blood-brain barrier (BBB) permeability. In contrast, a coapplication of Ang-1 and VEGF leads to a significant reduction of the ischemic and edema volumes by 50% and 42%, respectively, in comparison with VEGF-treated mice. We proposed that Ang-1 blocks the BBB permeability effect of VEGF in association with a modulation of matrix metalloproteinase (MMP) activity. Indeed, we showed on both ischemic in vivo and BBB in vitro models that VEGF enhances BBB damage and MMP-9 activity and that Ang-1 counteracts both effects. However, we also showed a synergic angiogenic effect of Ang-1 and VEGF in the brain. Taken together, these results allow to propose that, in cerebral ischemia, the combination of Ang-1 and VEGF could be used early to promote the formation of mature neovessels without inducing side effects on BBB permeability.

Angiopoietin-1↗
PubMed2004

Hypoxic preconditioning protects against ischemic brain injury.

Animals exposed to brief periods of moderate hypoxia (8% to 10% oxygen for 3 hours) are protected against cerebral and cardiac ischemia between 1 and 2 days later. This hypoxia preconditioning requires new RNA and protein synthesis. The mechanism of this hypoxia-induced tolerance correlates with the induction of the hypoxia-inducible factor (HIF), a transcription factor heterodimeric complex composed of inducible HIF-1alpha and constitutive HIF-1beta proteins that bind to the hypoxia response elements in a number of HIF target genes. Our recent studies show that HIF-1alpha correlates with hypoxia induced tolerance in neonatal rat brain. HIF target genes, also induced following hypoxia-induced tolerance, include vascular endothelial growth factor, erythropoietin, glucose transporters, glycolytic enzymes, and many other genes. Some or all of these genes may contribute to hypoxia-induced protection against ischemia. HIF induction of the glycolytic enzymes accounts in part for the Pasteur effect in brain and other tissues. Hypoxia-induced tolerance is not likely to be equivalent to treatment with a single HIF target gene protein since other transcription factors including Egr-1 (NGFI-A) have been implicated in hypoxia regulation of gene expression. Understanding the mechanisms and genes involved in hypoxic tolerance may provide new therapeutic targets to treat ischemic injury and enhance recovery.

Animals↗
PubMed2002

Brain genomic response following hypoxia and re-oxygenation in the neonatal rat. Identification of genes that might contribute to hypoxia-induced ischemic tolerance.

Hypoxic preconditioning (8% O2, 3 h) produces tolerance 24 h after hypoxic-ischemic brain injury in neonatal rats. To better understand the ischemic tolerance mechanisms induced by hypoxia, we used oligonucleotide microarrays to examine genomic responses in neonatal rat brain following 3 h of hypoxia (8% O2) and either 0, 6, 18, or 24 h of re-oxygenation. The results showed that hypoxia-inducible factor (HIF)-1- but not HIF-2-mediated gene expression may be involved in brain hypoxia-induced tolerance. Among the genes regulated by hypoxia, 12 genes were confirmed by real time reverse transcriptase-PCR as follows: VEGF, EPO, GLUT-1, adrenomedullin, propyl 4-hydroxylase alpha, MT-1, MKP-1, CELF, 12-lipoxygenase, t-PA, CAR-1, and an expressed sequence tag. Some genes, for example GLUT-1, MT-1, CELF, MKP-1, and t-PA did not show any hypoxic regulation in either astrocytes or neurons, suggesting that other cells are responsible for the up-regulation of these genes in the hypoxic brain. These genes were expressed in normal and hypoxic brain, heart, kidney, liver, and lung, with adrenomedullin, MT-1, and VEGF being prominently induced in brain by hypoxia. These results suggest that a number of endogenous molecular mechanisms may explain how hypoxic preconditioning protects against subsequent ischemia, and may provide novel therapeutic targets for treatment of cerebral ischemia.

Animals↗
PubMed2002

Normobaric hypoxia induces tolerance to focal permanent cerebral ischemia in association with an increased expression of hypoxia-inducible factor-1 and its target genes, erythropoietin and VEGF, in the adult mouse brain.

Tolerance to cerebral ischemia is achieved by preconditioning sublethal stresses, such as ischemia or hypoxia, paradigms in which the decrease of O2 availability may constitute an early signal inducing tolerance. In accordance with this concept, this study shows that hypoxia induces tolerance against focal permanent ischemia in adult mice. Normobaric hypoxia (8% O2 of 1-hour, 3-hour, or 6-hour duration), performed 24 hours before ischemia, reduces infarct volume by approximately 30% when compared with controls. To elucidate the mechanisms underlying this neuroprotection, the authors investigated the effects of preconditioning on cerebral expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and its target genes, erythropoietin and vascular endothelial growth factor (VEGF). Hypoxia, whatever its duration (1 hour, 3 hours, 6 hours), rapidly increases the nuclear content of HIF-1alpha as well as the mRNA levels of erythropoietin and VEGF. Furthermore, erythropoietin and VEGF are upregulated at the protein level 24 hours after 6 hours of hypoxia. The authors' findings show that (1) hypoxia elicits a delayed, short-lasting (<72 hours) tolerance to focal permanent ischemia in the adult mouse brain; (2) HIF-1 target genes could contribute to the establishment of tolerance; and (3) this model might be a useful paradigm to further study the mechanisms of ischemic tolerance, to identify new therapeutic targets for stroke.

Animals↗
PubMed2000

Neuroprotection and Angiogenesis: Dual Role of Erythropoietin in Brain Ischemia.

Erythropoietin, originally defined as an erythroid growth factor, is upregulated in the brain under conditions of hypoxia. So far, two functions have been identified for this locally produced cytokine: a direct protective effect on neuronal cells during cerebral ischemia and an indirect protection of brain tissue that could be provided by promoting brain vessel growth.

Journal Article↗
PubMedDate not supplied

Hypoxia preconditioning in the brain.

Exposure to moderate hypoxia alone does not cause neuronal death as long as blood pressure and cerebral blood flow are maintained in mammals. In neonatal and adult mammals including rats and mice, carotid occlusion in combination with hypoxia produces neuronal death and brain infarction. However, preexposure to 8% oxygen for 3 h protects the brain and likely other organs of neonatal and adult rats against combined hypoxia-ischemia 24 h later. In this paper, the possible mechanisms of this so-called hypoxia-induced tolerance to ischemia is discussed. One mechanism likely involves hypoxia-inducible factor-1alpha (HIF-1alpha). HIF-1alpha is a transcription factor that - during hypoxia - binds with a second protein (HIF-1beta) in the nucleus to promoter elements in hypoxia-responsive target genes. This causes upregulation of HIF target genes including VEGF, erythropoietin, iNOS, glucose transporter-1, glycolytic enzymes, and many other genes to protect the brain against ischemia 24 h later. In addition, non-HIF pathways including MTF-1, Egr-1 and others act directly or indirectly on other target genes to also promote hypoxia-induced preconditioning. Hypoxia preconditioning can be mimicked by iron chelators like desferrioxamine and transition metals like cobalt chloride that inhibit prolyl hydroxylases, increase HIF-1alpha levels in the brain, and produce protection of the brain against combined hypoxia-ischemia 24 h later. This hypoxia preconditioning has potential clinical usefulness in protecting high-risk newborns or to provide protection prior to surgery.

Animals↗