PROJECT SUMMARYStroke is the fifth leading cause of death in the United States. Approved stroke therapies are limited by narrowtreatment windows the risk of hemorrhagic transformation and reperfusion injury. Therefore there is a criticalneed for neuroprotective drugs that can improve post-stroke neurological performance. Currently 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (i.e. statins) are given to stroke patients due to theirproven utility in improving cognitive and motor outcomes. Studies in our laboratory have uncovered a specificbiological mechanism that enables statins to be effective drugs for stroke treatment: transport across the blood-brain barrier (BBB) via the endogenous uptake transporter organic anion transporting polypeptide 1a4 (Oatp1a4).We have shown for the first time that Oatp-mediated transport is required for atorvastatin to reduce cerebralinfarction volume and improve sensorimotor performance at 24 h following transient middle cerebral arteryocclusion (tMCAO). We also observed increased atorvastatin uptake in female rats subjected to tMCAO ascompared with their age-matched male counterparts; however it is unknown if these differences in Oatp-mediated transport at the BBB cause variations in atorvastatins ability to prevent stroke progression and/orworsening of neurocognitive deficits in the acute/subacute period. Our goals are to assess the role of sex as abiological variable on statin transport in the ischemic brain and to determine how these differences affect statinefficacy as stroke therapeutics. The central hypotheses of this F31 application are i) that functionalexpression of Oatp1a4 at the BBB is different in males as compared to females following tMCAO; and ii)that statin neuroprotective properties and/or their effects on post-stroke neurological outcomes areinfluenced by sex-dependent differences in BBB Oatp1a4 activity. Two aims will test these hypotheses:Aim 1: Investigate sex-dependent differences in Oatp1a4-mediated transport of statins at the BBB instroke. We will perform our studies in male and female SD rats using the tMCAO model. Oatp1a4 localizationand protein expression will be assessed using confocal microscopy and western blotting respectively. Blood-to-brain transport of statins will be measured using in situ brain perfusion a state-of-the-art methodology to studydrug transport at the BBB.Aim 2: Evaluate sex-dependent differences in statin-associated neuroprotection and functionalneurological recovery in stroke. In tMCAO operated male and female SD rats we will use confocal microscopyand western blot analysis to examine molecular biomarkers associated with neuroprotection. We will also assessmotor and cognitive performance in tMCAO-animals using robust behavioral tests (i.e. rotarod analysis MorrisWater Maze Novel Object Recognition test).Overall this project will provide critical mechanistic data on efficacy of statins as neuroprotective drugs for stroke.Furthermore this project directly aligns with NIH goals in studying sex as a biological variable in stroke.