The effects of glucocorticoids in in vitro models of the blood-brain barrier facing an inflammatory challenge.

Abstract

Several neurological conditions are associated with the blood-brain barrier (BBB) rupture, including neurodegenerative diseases, trauma, brain tumors, stroke, and epilepsy. Among the risk factors for these diseases are chronic inflammation and stress, also related to the BBB loss of integrity. Glucocorticoids (GCs) are the main hormones related to the stress response in addition of being the most prescribed anti-inflammatory drugs worldwide. However, the literature and our laboratory have shown that GCs are not uniformly anti-inflammatory and can even increase some aspects of inflammation. Specifically, GCs modulate several functions of the BBB cells, from their stabilization, due the modulation of occlusive junctions proteins, to the reduction of the adhesion molecules expression and transcytosis in endothelial cells. However, these functions may be compromised, especially in the presence of an inflammatory challenge following a GCs stimulus. Furthermore, the effects of these hormones' actions are dependent on the target cells phenotypes and microenvironment, whether physiological or pathological. The Klotho protein has anti-inflammatory actions and its circulating levels are reduced in neurodegenerative diseases, however there is no information on BBB's effects nor direct correlation with GCs' levels. Thus, this project aims to evaluate and characterize the neurovascular unit (NVU, blood-brain barrier and neighboring cells) response in the face of prolonged GCs (endogenous or synthetic) treatment, and a subsequent inflammatory challenge, in the presence or absence of klotho, in in vitro models of BBB/NVU co-culture with inserts or microfluidic on chip. This project will evaluate several parameters in the NVU cell types, among them, structure and morphology, permeability, cell transport and its receptors, inflammatory mediators, as well as viability and types of cell death. We strongly believe that this project not only will provide new in vitro models to study the BBB physiology, which knowledge is fundamental to increase the understanding of the pathophysiology of the most devastating brain diseases but also will contribute to the better comprehension of the effects of GCs and Klotho (both physiological and pharmacological) in such diseases, considerably improving their treatment outcomes and therefore, their prognosis. (AU)