Time to target stroke: Examining the circadian system in stroke

Stroke is the 5^th leading cause of death in the United States and a leading cause of long-term disability. Ischemic strokes account for 87 percent of total stroke cases, yet the only FDA-approved treatments involve disruption of the blood clot to restore blood flow. New treatments aimed at saving or protecting neural tissue have largely failed in clinical trials and so new methodology or targets must be found. The occurrence of strokes significantly increases between 6 AM and 12 PM, implicating the circadian system in the onset of this debilitating brain injury. But it is not known whether or how the circadian system may regulate the response to and recovery from stroke. New strategies to identify treatments for stroke are beginning to look at cell types other than neurons as therapeutic targets, including astrocytes. In this review, we present links between the astrocyte circadian clock, the molecular response to stroke, and the damage caused by ischemia. We highlight aspects of astrocyte circadian function that could dictate new methodologies for stroke treatment, including the potential of chronotherapy.