Research report Glycerophosphoinositol and dexamethasone improve transendo electrical resistance in an in vitro study of the blood–brain barr Luca Cucullo a , Kerri Hallene a , Gabriele Dini a , Roberto Dal Toso b , Damir Janigro a,c, * a Cerebrovascular Research Center, Department of Neurological Surgery, Cleveland Clinic Foundation, Cleveland, OH 44195, USA b I.R.B. Altavilla Vicentina, 36077, Italy c Cerebrovascular Research Center, Department of Cell Biology, Cleveland Clinic Foundation, Cleveland, OH 44195, USA Accepted 12 September 2003 Abstract The blood – brain barrier (BBB) maintains the homeostasis of the brain microenvironment, which is crucial for neuronal activity and function. Under pathological conditions, the BBB may fail due to yet unknown mechanisms. BBB failure is accompanied by the transendothelial permeability to substances such as sucrose that are normally extruded. Furthermore, altered BBB fun to development of abnormal drug extrusion mechanisms including expression of multiple drug resistance proteins. Therefore, it is not surprising that strategies have been developed to ‘‘repair’’ the BBB in order to restore normal brain homeostasis and pene pharmacologically active (noxious) substances. To this end, steroidal hormones and synthetic analogues such as dexamet been used to counteract BBB failure. However, several side effects limit the usefulness of steroid treatment in humans lea developing novel strategies for BBB repair. We here show that, in an in vitro model of the BBB based on a co-culture of en (EC) and glia, the natural compound glycerophosphoinositol (GPI) may replicate the effects of DEX. Thus, GPI in concentra from 3 to 100 AM promoted both BBB formation and repair in a dose dependent fashion. Similar effects were obtained with of DEX (10 AM); at higher concentrations (100 AM), DEX was cytotoxic. We conclude that the endogenous anti-inflammatory agent GP may ameliorate BBB function with efficacy comparable to that of steroids, but with significantly fewer side effects. Further confirm the efficacy of this treatment in vivo and elucidate the pathways that lead to BBB repair after exposure to GPI. D 2003 Elsevier B.V. All rights reserved. Keywords: Blood – brain barrier; Dexamethasone; GPI anti-inflammatory agent; Glucocorticoid; Arachidonic acid; In vitro model 1. Introduction The blood – brain barrier (BBB) is composed of a con- tinuous layer of cerebrovascular endothelial cells (EC) that lie on a basal lamina. EC are joined by tight intercellular junctions that provide a biological barrierto maintain the homeostasis of the brain microenvironment. This special- ized barrier serves as an interface between the circulating blood,brain interstitium and parenchyma, isolating brain tissue from blood constituents [1]. Given the crucial impor- tance of BBB functions in maintaining the central nervous system (CNS) homeostasis by preventing entry of substan- ces thatmightalterneuronalfunction in theCNS, it becomes evident how failure or partial deterioration of the BBB could play a role in the pathogenesis of brain disease Inflammatory processes at the BBB level,occurring for whatevereason,are one ofthe main causes of BBB disruption [11,20,28]. Matrix metalloproteinases such as gelatinase A (MMP 2 ) and gelatinase B (MMP 9 ) are directly involved in this process due their degrading action on the extracellular matrix that existbetween EC and their astro- cytic counterpart [15,23,27]. Glucocorticoids, a subclass of anti-inflammatory steroid hormones called corticosteroids (CS), have been extensive- ly used to treat a broad variety of autoimmune disorders and to reduce brain edema [10]. CS exerts their complex effectson cellsinvolved in immuneand inflammatory responsesprimarily by modulating gene transcription. However, they also influence the translational and post- translational mechanisms by which proteinsaresynthe- sized,processed and exported from cells [14,17,26]. The 0006-8993/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2003.09.079 * Corresponding Author. Cleveland Clinic Foundation NB20, Neuro- surgery, 9500 Euclid Avenue/NB20, Cleveland, OH 44195, USA. Tel.: +1- 216-445-0561; fax: +1-216-444-1466. E-mail address: janigrd@ccf.org (D. Janigro). www.elsevier.com/locate/brainres Brain Research 997 (2004) 147 – 151