Neuroprotective Effect of VEGF-Mimetic Peptide QK in Experimental Brain Ischemia Induced in Rat by Middle Cerebral Artery Occlusion Giuseppe Pignataro, † Barbara Ziaco, § Anna Tortiglione, † Rosaria Gala, † Ornella Cuomo, † Antonio Vinciguerra, † Dominga Lapi, ‡ Teresa Mastantuono, ‡ Serenella Anzilotti, ∥ Luca Domenico D’Andrea, § Carlo Pedone, § Gianfranco di Renzo, † Lucio Annunziato, †,∥ and Mauro Cataldi* ,† † Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatologic Sciences, ‡ Division of Physiology, Department of Clinical Medicine and Surgery, School of Medicine, Federico II University of Naples, 80131 Naples, Italy § Institute of Biostructure and Bioimaging, Italian National Research Council (CNR), 80145 Naples, Italy ∥ IRCCS SDN, Via Gianturco, 80143 Naples, Italy ABSTRACT: We investigated the effect of the VEGF-mimetic peptide, QK, on ischemic brain damage and on blood−brain barrier permeability in the rat. QK administered by the intracerebroventricular, intravenous, or intranasal route caused a 40% decrease in ischemic brain damage induced by permanent occlusion of the middle cerebral artery relative to that in controls. No increase in the volume of the ischemic hemisphere compared to that of the contralateral nonischemic hemisphere was observed in rats treated with QK, suggesting that this peptide did not cause brain edema. The effect of QK on vessel permeability was evaluated by intravital pial microvessel videoimaging, a technique that allows the pial vessels to be visualized through a surgically prepared open cranial window. The results showed that QK did not cause any leakage of intravenously injected fluorescein−dextran conjugates after intracarotid administration or topical application to the brain cortex. Collectively, these data suggest that QK may exert neuroprotective activity in the context of stroke without promoting any increase in vascular permeability. Because VEGF’s neuroprotective activity may be overshadowed by the appearance of brain edema and microbleeds, QK could represent a significant step forward in stroke treatment. KEYWORDS: Cerebral ischemia, vascular endothelial growth factor, vascular permeability, brain edema, neuroprotection V EGF has long been considered a promising drug candidate for stroke therapy because of its neuroregenerative and neuroprotective properties. 1 Indeed, after a stroke, the synthesis and release of VEGF are induced in the brain, 2 and this growth factor orchestrates a reparative cascade that aims to restore blood perfusion through new blood vessels and to repopulate the injured brain with new neuronal, glial, and endothelial cells. 3,4 Specifically, VEGF activates the neurovascular niche, a highly specialized unit composed of mutually interacting neuroblasts and newly formed endothelial cells and glial cells. 1,5−7 Moreover, VEGF exerts significant neuroprotective activity in in vitro models of ischemic neuronal cell death 8 and excitotoxicity. 9,10 This suggests that, after stroke, VEGF not only promotes regeneration but also rescues neurons in the ischemic penumbra, 11 the brain region that surrounds the ischemic core and that dies hours or days after vessel occlusion because of the impairment of intracellular ion homeostasis. 12−14 Despite this strong rationale, the use of VEGF in experimental brain ischemia has yielded controversial and generally dis- appointing results. It has become clear that the increase in vascular permeability induced by this growth factor may overshadow its neuroprotective effects. 15,16 VEGF induces, indeed, the formation of blood vessels that are immature and leaky 17 and acutely increases the permeability of preexisting blood vessels, causing the loosening of endothelial cell junctions and the formation of fenestrations. 18−22 Because of these effects on vascular permeability, VEGF caused brain edema and microbleeds and ultimately worsened tissue damage in animal models of stroke. 23,24 Therefore, the development of this growth factor as a therapeutic tool in brain ischemia appears to be problematic. New VEGF-like peptides with proangiogenic activity have been recently synthesized. They are considered to be a promising alternative to VEGF for clinical applications such as wound repair and ulcer healing because of their less expensive and easier synthesis. 25,26 It is still unclear, however, whether these VEGF- mimetic peptides could also represent an improvement over VEGF for stroke therapy. In particular, it has not yet been established whether they have neuroprotective activity in the context of stroke and whether they promote blood−brain barrier (BBB) permeabilization like VEGF. In the present article, we explored this issue using one of the most interesting members of this new family of VEGF-mimetic peptides, the QK peptide that Received: October 6, 2014 Published: July 14, 2015 Research Article pubs.acs.org/chemneuro © 2015 American Chemical Society 1517 DOI: 10.1021/acschemneuro.5b00175 ACS Chem. Neurosci. 2015, 6, 1517−1525