Oxidative stress and cerebral endothelial cells: regulation of the blood-brain-barrier and antioxidant based interventions

Abstract

While numerous lines of evidence point to increased levels of oxidative stress playing a causal role in a number of neurodegenerative conditions, our current understanding of the specific role of oxidative stress in the genesis and/or propagation of neurodegenerative diseases remains poorly defined. Even more challenging to the "oxidative stress theory of neurodegeneration" is the fact that many antioxidant-based clinical trials and therapeutic interventions have been largely disappointing in their therapeutic benefit. Together, these factors have led researchers to begin to focus on understanding the contribution of highly localized structures, and defined anatomical features, within the brain as the sites responsible for oxidative stress-induced neurodegeneration. This review focuses on the potential for oxidative stress within the cerebrovascular architecture serving as a modulator of neurodegeneration in a variety of pathological settings. In particular, this review highlights important implications for vascular-derived oxidative stress in the initiating and promoting pathophysiology in the brain, identifying new roles for cerebrovascular oxidative stress in a variety of brain disorders. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Figure 1. Sources of Oxidative Stress at Cerebral Endothelial cells

A) In the healthy brain, the BBB is intact with the help of claudins, occludin, and junctional adhesion molecules (JAMs) to create the tight junction between endothelial cells. Actin and the zona occludens (ZO-1 and ZO-2, etc.) also create a scaffold for the tight junction. Further support for the BBB comes from the extracellular matrix and astrocytic end feet. B) In the unhealthy brain, ROS accumulate from various sources including mitochondria, microglia, the lipid bilayer, and astrocytes. This causes altered assembly of the tight junctions, breakdown of the extracellular matrix by MMPs and subsequent loss of BBB integrity.