Brancaccio, Paola (2016) CHARACTERIZATION OF A MOUSE MODEL OF HYPOXIC PRECONDITIONING IN NEONATAL HYPOXIA ISCHEMIA. [Tesi di dottorato]

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Item Type: Tesi di dottorato
Lingua: English
Title: CHARACTERIZATION OF A MOUSE MODEL OF HYPOXIC PRECONDITIONING IN NEONATAL HYPOXIA ISCHEMIA
Creators:
CreatorsEmail
Brancaccio, Paolapaolabrancaccio985@yahoo.it
Date: 31 March 2016
Number of Pages: 142
Institution: Università degli Studi di Napoli Federico II
Department: Neuroscienze e Scienze Riproduttive ed Odontostomatologiche
Scuola di dottorato: Medicina molecolare
Dottorato: Neuroscienze
Ciclo di dottorato: 28
Coordinatore del Corso di dottorato:
nomeemail
Annunziato, Luciolannunzi@unina.it
Tutor:
nomeemail
Pignataro, GiuseppeUNSPECIFIED
Date: 31 March 2016
Number of Pages: 142
Uncontrolled Keywords: Preconditioning, Neonatal hypoxia ischemia, NCX
Settori scientifico-disciplinari del MIUR: Area 05 - Scienze biologiche > BIO/14 - Farmacologia
Date Deposited: 11 Apr 2016 12:42
Last Modified: 21 Apr 2019 01:00
URI: http://www.fedoa.unina.it/id/eprint/11010

Abstract

BACKGROUND: Hypoxic-ischemic (HI) damage in neonatal brain is a major risk factor for different human disorders. So far, no drug is presently available to manage this clinical emergency, therefore, the attention of researchers working in the field has been given to endogenous neuroprotective strategies, in order to identify new druggable targets. In particular, one of the best endogenous neuroprotective strategies is Preconditioning (PC), which is a subliminal stimulus able to protect the brain from a subsequent harmful stimulus. AIM: The first aim of the present work was to identify a new model of hypoxic preconditioning. Then, we investigated whether hypoxic preconditioning (HPC) is able to stimulate the differentiation of neural stem cells (NSCs) in a mouse model of neonatal hypoxia ischemia. In addition, we investigated the relationship between the alteration of ionic homeostasis and the activation of endogenous neurogenesis mediated by NCX. The plasma membrane protein Na+/Ca2+ exchanger (NCX), whose activity has been linked to brain ischemic pathophysiology in adult animals. METHODS: Seven-day-old C57BL/6 mice were divided into different experimental groups. Hypoxia ischemia was induced by using Rice-Vannucci model. Briefly, they were subjected to ligation and cutting of the right common carotid artery followed by an exposure to hypoxia (92% N2 and 8% O2) at different time intervals and sacrificed at different times of reperfusion. Histopathological damage in the hippocampus was determined by measuring the expression level of Propidium Iodide (PI), whereas the neurogenesis was evaluated by using immunohistochemistry with different markers. The development of sensorimotor reflexes was examined by behavioral tests. The increase of NCX expression was evaluated by using immunohistochemical analyses in hippocampus dentate gyrus. RESULTS: As expected, the greatest damage was found in mice subjected to ischemia plus 60’ hypoxia (HI 60’) and sacrificed 7 days after ischemia induction. A significant reduction in the hippocampal damage was observed in mice subjected to hypoxia for 20 minutes at postnatal day seven (P7) followed, 3 days later, by HI 60’ (P10) and sacrificed at postnatal day eleven (P11). Indeed, this result suggests that 20’ hypoxia functions as a preconditioning stimulus. In animals subjected to hypoxic-ischemic insult the damage was mainly localized in CA1 and CA3 regions, whereas the dentate gyrus was spared. Concerning the mechanism by which preconditioning may exert its effects, we found that preconditioning stimulus was able to trigger an increased expression of Nestin, a marker of neurogenesis, in seven-day-old mice. In addition, hypoxic preconditioning was able to determine the increase of proliferating cells (BrdU+/PSANCAM+) and neuroblast cells (PSANCAM+) in the dentate gyrus of HI 60’ (P10) mice, sacrificed at P11. In subventricular zone hypoxic preconditioning determined the increase of neuroblast cells (PSANCAM+). Moreover, we observed an increase of NCX1 and NCX3 positive cells in dentate gyrus of preconditioned hypoxic-ischemic animals. Interestingly, the preconditioned hypoxic-ischemic animals also showed a better performance in the cliff avoidance and geotaxis reflex test than HI 60’ mice. CONCLUSIONS: Our results indicate that hypoxic preconditioning is associated to endogenous neurogenesis in immature brain after insult. The increase of neurogenic process is probably correlated to ionic homeostasis maintenance, regulated by NCX proteins. Therefore, NCX proteins can represent potential pharmacological targets for the treatment of brain damage associated to neonatal hypoxic-ischemic encephalopathy (HIE).

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