Inhibition of Stroke‐Induced Injury by Phlebotomy

Stroke is the second most common death and a leading cause of long‐term disability worldwide, yet the therapeutic options are still limited. Hemodilution has been reported to reduce brain infarction in experimental stroke model. Phlebotomy causes hypovolemic‐hemodilting effect, but whether it offers protection after ischemic stroke remains unclear. Using permanent occlusion model, we aimed to assess the effect of phlebotomy on ischemic stroke. Male spontaneously hypertensive rats (SHR) were subjected to permanent MCA occlusion (pMCAO) to produce cerebral ischemia. Phlebotomy was conducted by drawing 0.8 ml of whole blood after the pMCAO. In another set of experiment, macrophage migration inhibitory factor (MIF, 10 or 20μg/kg, i.v.) or its antagonist, ISO‐1 (3 mg/kg, s.c.), were administered 3 h after pMCAO. Brain infarction, neurological function and protein expression were analyzed 24 h after pMCAO. Cerebrovascular integrity was analyzed 7 h after pMCAO. Analysis of serum by proteome profiler array and ELISA were performed at 3 h, 6 h and 24 h after pMCAO. Our results show that phlebotomy at 3 h after MCA occlusion significantly reduced stroke‐induced infarction and brain edema and shows an improvement in behavioral deficit. Inflammatory responses were decreased in phlebotomy‐3h group as the expression of inflammation‐related mediators were reduced. Analysis of the cytokine profile in serum led us to presume Macrophage migration inhibitory factor (MIF) as a possible mediator of the protection by phlebotomy. MIF aggravated stroke injury with a larger infarction and a more severe cerebrovascular disruption was observed, whereas, its antagonist ISO‐1 inhibited stroke‐induced infarction. In conclusion, phlebotomy offers protection when conducted 3 h after stroke onset and may exert its protective effect through the suppression of inflammatory cascade by interfering the balance of inflammatory mediators in serum. Support or Funding Information This work was supported by the Ministry of Science and Technology grants, 104‐2321‐B‐002‐033, Taiwan.