The blood-brain barrier: an overview: structure, regulation, and clinical implications

Cell Biology of the Neurovascular Unit: Implications for Drug Delivery Across the Blood–Brain Barrier

The central nervous system (CNS) neurovascular unit is a dynamic structure consisting of vascular endothelial cells, pericytes, and closely juxtaposed astrocytes and neurons. Contact and communication events between cells of the neurovascular unit regulate CNS development, modulate cerebral blood flow, and influence permeability properties of the blood-brain barrier. Dysregulation of proper neurovascular unit function is linked to many common human CNS pathologies, making it a target for a variety of neurotherapeutic interventions. Furthermore, manipulation of the neurovascular unit to enhance the delivery of drugs to the CNS is an active area of interest. In this review I summarize current data concerning the cell and molecular biology of the neurovascular unit. Additionally, I suggest how manipulation of novel protein components of the neurovascular unit may enhance delivery of neurotherapeutic drugs across the blood-brain barrier.

Peroxisome proliferator-activated receptor-γ ligands reduce inflammation and infarction size in transient focal ischemia

Newly developed insulin-sensitizing agents, which target the nuclear receptor peroxisome proliferator-activated receptor-gamma have recently been appreciated to exhibit potent anti-inflammatory actions. Since stroke is associated with an intense inflammatory response, we reasoned that these agents may ameliorate injury from stroke. We report that administration of troglitazone or pioglitazone 24 h before and at the time of cerebral infarction dramatically reduced infarction volume and improved neurological function following middle cerebral artery occlusion in rats. Furthermore, we find that delayed therapy also significantly reduced infarct volume. The brains of the drug-treated animals displayed reduced inflammation as evidenced by decreased immunoreactivity for microglial/macrophage markers and reduced protein and mRNA for interleukin-1beta, cyclooxygenase-2 and inducible nitric oxide synthase. We argue that the beneficial effects of these drugs are likely due to reduced expression of these inflammatory mediators, which are known to exacerbate ischemic injury following stroke. These results are of particular relevance to diabetic patients chronically treated with these agents who may benefit from the neuroprotective actions of these drugs.

Role of glial cells in cerebral ischemia

Despite intense efforts at the bench and at the bedside, few therapeutic strategies exist to combat the consequences of cerebral ischemia. Traditionally, a "neurocentric" view has dominated research in this field. Evidence is now accumulating that glial cells, in particular astrocytes, play an active and important role in the pathophysiology of cerebral ischemia. Brain energetics, water and ion homeostasis, inflammation, trophic factor production, vascular regulation, neuroneogenesis, and vasculogenesis, among others, are all under the control of glial cells. As a consequence, glial cells have been identified as promising targets for novel therapeutic approaches in brain protection. This review aims at dissecting possible protective as well as destructive roles of astrocytes (and other glial cells) in cerebral ischemia. By emphasizing open issues in this field, we hope to stimulate further research into this relatively unexplored aspect of brain pathophysiology.