Neurovascular mechanisms of ischemia tolerance against brain injury

Abstract

Traumatic brain injury (TBI) can result in secondary ischemia. This secondary ischemic insult is implicated in post-TBI pathophysiology. Pharmacological intervention to elevate cerebral blood flow can improve outcomes following TBI. The brain and other organ systems have an innate ability to induce protection against ischemic injury, limiting the severity of the ischemia-induced damage. This "self" protection can be initiated by exposing the brain to a stimulus before ischemia called "preconditioning," such as exposure to a mild episode(s) of ischemia, hypoxia, anesthesia, or pharmacologically induced mild cell stressors. Current efforts to reduce ischemia-induced brain damage have been the focus in determining the mechanisms of preconditioning-induced ischemia tolerance as findings may help lower cerebral ischemia-induced brain damage in at-risk patients including TBI patients. Different preconditioning paradigms have been shown to lower TBI-induced damage. Although not all of the mechanisms of preconditioning are confirmed in models of TBI, basic mechanisms of preconditioning applies here as ischemia is a major part of TBI. Ischemic preconditioning, in part, confers protection by modulating regulators of cerebral blood flow, increase angiogenesis, and prevent cerebral ischemia-induced increase in blood-brain barrier permeability. This chapter highlights preconditioning-induced changes in components of the neurovascular system involved in ischemia tolerance. Understanding of these pathways may aid in the development of novel therapies to protect the brain from TBI-induced secondary ischemic insult.