Aβ42 production in brain capillary endothelial cells after oxygen and glucose deprivation Alessandra Bulbarelli a , Elena Lonati a, ⁎, Anna Brambilla a , Antonina Orlando a , Emanuela Cazzaniga a , Fabrizio Piazza b , Carlo Ferrarese b, c , Massimo Masserini a , Giulio Sancini a a Department of Experimental Medicine, University of Milano-Bicocca via Cadore 48, 20900 Monza, MI, Italy b Department of Neuroscience and Biomedical Technologies, University of Milano-Bicocca via Cadore 48, 20900 Monza, MI, Italy c Department of Neurology, San Gerardo Hospital via Pergolesi 33, 20900 Monza, Italy abstract article info Article history: Received 21 July 2011 Revised 6 December 2011 Accepted 25 January 2012 Available online 3 February 2012 Keywords: Alzheimer's disease Amyloid-β 1-42 Amyloid-β protein precursor Blood brain barrier Brain ischemia–anoxia HIF-1alpha protein Although the diverse triggers of AD are still under debate, the hypothesis of the contribution of cerebrovascu- lar deficiencies has emerged in recent years. Cerebrovascular dysfunction may precede cognitive decline and onset of neurodegeneration. Indeed, the toxic Aβ 42 aggregates constituting senile plaques, one of AD hall- marks, is often detected as amorphous material or fine fibrils in the brain capillary of AD patients. Aβ 42 causing cerebral microangiopathy might originate either from the circulating blood, the vessel wall itself or the brain parenchyma. In the present investigation we show, for the first time, that in rat brain capillary endothelial cells (RBE4), in vitro oxygen glucose deprivation treatment elicits 250% of Aβ 42 peptide production increase through a mechanism that involves the hypoxia inducible factor-1-mediated β-secretase (BACE1) up- regulation. Furthermore, we observed a time dependent increase of amyloid protein precursor (AβPP) gene and protein expression, confirming previous reports which established the existence of AβPP in the cerebro- vascular domain. Our experimental evidences point out that ischemic events may directly contribute in brain capillary endo- thelial cells to the enhancement of the amyloidogenic metabolism, leading to intracellular deposition of Aβ 42 . This events may contribute to the impairment of Aβ brain clearance and AD related blood brain barrier dysfunctions. © 2012 Elsevier Inc. All rights reserved. Introduction Alzheimer's disease (AD) is a progressive neurodegenerative ill- ness affecting the elderly population. The pathological hallmarks of the disease are senile plaques consisting of amyloid-β (1-42) (Aβ 42 ) aggregates, neurofibrillary tangles (NFTs) and neuronal loss in the patient's brain (Allsop, 2000; Swerdlow, 2007a,b). The pathogenesis of sporadic late-onset AD has not been identi- fied, but further studies support that the environmental risk factors play an important role in its onset and development. The major risk factors for AD include aging, atherosclerosis, diabetes mellitus and stroke (Cechetto et al., 2008; Isik, 2010; Marques et al., 2011). Although the etiology of neurodegenerative mechanisms are still under elucidation, the possible contribution of cerebrovascular defi- ciencies has been vigorously promoted in recent years (Farkas and Luiten, 2001). Various forms of cerebrovascular insufficiency, such as reduced blood supply to the brain or disrupted microvascular integrity, may oc- cupy an initiating or intermediate position in the chain of events of neu- rodegenerative changes in AD onset, ending with cognitive failure (Bell and Zlokovic, 2009; de la Torre, 2008). Moreover, the cerebrovascular district is physiologically involved in Aβ clearance through perivascular drainage (Preston et al., 2003) and receptor-mediated uptake or bidi- rectional exchanges across the blood brain-barrier (BBB) (Tanzi et al., 2004)(Wang et al., 2006). Cerebral imbalance between Aβ 42 peptide production and clearance may play a causal role in AD, leading to in- creased amounts of Aβ 42 in various aggregated forms in the central ner- vous system. Ultrastructural studies in humans and animal models suggest the strong contribution of vascular deficiency in the distinctive AD neuro- degenerative mechanisms, given that the toxic Aβ is often encoun- tered as amorphous material or fine fibrils in the brain capillary of Molecular and Cellular Neuroscience 49 (2012) 415–422 Abbreviations: AD, Alzheimer's disease; A β 42 , amyloid-β (1-42); BBB, Blood Brain Barrier; AβPP, amyloid-β protein precursor; OGD, Oxygen Glucose Deprivation; HIF-1α, Hypoxia Inducible Factor-1alpha; RBE4, rat brain capillary endothelial cells; BACE1, β- secretase 1; VEGF, vascular endothelial growth factor. ⁎ Corresponding author. Fax: + 39 02 64488068. E-mail addresses: alessandra.bulbarelli@unimib.it (A. Bulbarelli), elena.lonati1@unimib.it (E. Lonati), a.brambilla18@campus.unimib.it (A. Brambilla), a.orlando7@campus.unimib.it (A. Orlando), emanuela.cazzaniga@unimib.it (E. Cazzaniga), fabrizio.piazza@unimib.it (F. Piazza), carlo.ferrarese@unimib.it (C. Ferrarese), massimo.masserini@unimib.it (M. Masserini), giulio.sancini@unimib.it (G. Sancini). 1044-7431/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.mcn.2012.01.007 Contents lists available at SciVerse ScienceDirect Molecular and Cellular Neuroscience journal homepage: www.elsevier.com/locate/ymcne