Nuove strategie sperimentali per la comprensione e il trattamento dell’ischemia cerebrale

Abstract

Ischemic stroke is a leading cause of death and long-term disabilities worldwide. Although the pathophysiology of stroke has been studied extensively and several drugs have been proposed in preclinical trials, the pharmacological approach to stroke treatment still remains limited to thrombolysis. The development of neuroprotective strategies is crucial to preserve the integrity of the so-called neurovascular unit (the network of neurons, glial components and endothelial cells which interact regulating brain homeostasis) during and following an ischemic event, and then to increase the chances of neurological recovery. Furthermore, a relevant part of all stroke subtypes has not been studied yet, because the lack of specific animal models able to mimic their pathological features. This Ph.D. Thesis, indeed, was aimed both at study new therapeutic strategies to treat stroke pathology and at elucidate pathophysiological mechanisms not yet fully understood. In the first part of this dissertation, I propose a new drug to treat acute ischemic stroke, the 5’-adenosine monophosphate (AMP). AMP administration reduces the infarct size after 90’ of middle cerebral artery occlusion acting on the modulation of body temperature. In particular, AMP reduces the temperature in a dose-dependent manner through the stimulation of Adenosine-1 receptors in the Central Nervous System, as demonstrated using specific inhibitors. Since endogenous AMP is also able to modulate body temperature, I conclude that the stimulation of AMP signaling pathway is beneficial in an experimental model of stroke and may offer a new target to design neuroprotective drugs In the second part of my Ph.D. Thesis I show the relationship between PARP-1 inhibitors and the mechanisms of ischemic tolerance. PARP-1 inhibition have been shown to improve stroke outcome in several animal models of cerebral ischemia, but its unclear if their use affects the development of brain tolerance. To investigate this aspect, I have studied PARP-1 activity in an animal model of ischemic preconditioning and I have evaluated the extent of neuroprotection provided by the brain conditioning using both pharmacological and genetic modulation of PARP-1. My results show that PARP-1 is not involved in our model of ischemic preconditioning and its pharmacological modulation doesn’t affect the mechanisms of brain tolerance The last chapter is focused on a new animal model to study the lacunar stroke. Deep white matter and lacunar strokes accounts for more than one quarter of all ischemic strokes, but our knowledges of this stroke subtype are incomplete. I have characterized a selective model of sub-cortical white matter stroke, showing both axonal and myelin degeneration and behavioral deficits induced by a lesion strategically located to mimic human pathology. Since the development of vascular dementia, a neurological condition leading to progressive cognitive skills loss and strictly connected to lacunar strokes, is associated with blood brain barrier (BBB) disruption, I have studied the time-course of BBB opening in this animal model to clarify the relationship between white matter fiber degeneration and BBB breakdown leading to vasogenic edema. This model can help to better understand important pathophysiological mechanisms in the field of ischemic lacunar strokes