Daidzein Augments Cholesterol Homeostasis via ApoE to Promote Functional Recovery in Chronic Stroke.

Stroke is the world's leading cause of physiological disability, but there are currently no available agents that can be delivered early after stroke to enhance recovery. Daidzein, a soy isoflavone, is a clinically approved agent that has a neuroprotective effect in vitro, and it promotes axon growth in an animal model of optic nerve crush. The current study investigates the efficacy of daidzein on neuroprotection and functional recovery in a clinically relevant mouse model of stroke recovery. In light of the fact that cholesterols are essential lipid substrates in injury-induced synaptic remodeling, we found that daidzein enhanced the cholesterol homeostasis genetic program, including Lxr and downstream transporters, Apoe, Abca1, and Abcg1 genes in vitro. Daidzein also elevated the cholesterol homeostasis genes in the poststroke brain with Apoe, the highest expressing transporter, but did not affect infarct volume or hemispheric swelling. Despite the absence of neuroprotection, daidzein improved motor/gait function in chronic stroke and elevated synaptophysin expression. However, the daidzein-enhanced functional benefits and synaptophysin expression were abolished in Apoe-knock-out mice, suggesting the importance of daidzein-induced ApoE upregulation in fostering stroke recovery. Dissociation between daidzein-induced functional benefits and the absence of neuroprotection further suggest the presence of nonoverlapping mechanisms underlying recovery processes versus acute pathology. With its known safety in humans, early and chronic use of daidzein aimed at augmenting ApoE may serve as a novel, translatable strategy to promote functional recovery in stroke patients without adverse acute effect. SIGNIFICANCE STATEMENT: There have been recurring translational failures in treatment strategies for stroke. One underlying issue is the disparity in outcome analysis between animal and clinical studies. The former mainly depends on acute infarct size, whereas long-term functional recovery is an important outcome in patients. In an attempt to identify agents that promote functional recovery, we discovered that an FDA-approved soy isoflavone, daidzein, improved stroke-induced behavioral deficits via enhancing cholesterol homeostasis in chronic stroke, and this occurs without causing adverse effects in the acute phase. With its known safety in humans, the study suggests that the early and chronic use of daidzein serves as a potential strategy to promote functional recovery in stroke patients.

Role of spleen-derived monocytes/macrophages in acute ischemic brain injury.

Monocytes/macrophages (MMs), mononuclear phagocytes, have been implicated in stroke-induced inflammation and injury. However, the presence of pro-inflammatory Ly-6C(high) and antiinflammatory Ly-6C(low) monocyte subsets raises uncertainty regarding their role in stroke pathologic assessment. With recent identification of the spleen as an immediate reservoir of MMs, this current study addresses whether the spleen-derived MMs are required for stroke pathologic assessment. We observed that the spleen was contracted in poststroke animals and the contraction was accompanied by decreased number of Ly-6C(high) and Ly-6C(low) subsets in the spleen. The deployment of these subsets from the spleen temporally coincided with respective increases in the ischemic brain. Compared to mice with the spleen, mice receiving a splenectomy just before the stroke displayed less accumulation of Ly-6C(high) and Ly-6C(low) MMs in the brain. Despite the reduced accumulation of both subsets, infarct size and swelling were not reduced in the asplenic mice. The dissociative findings of infarct size and extent of MM infiltration in the postischemic brain indicate minimal involvement of spleen-derived total MMs in acute infarct development. Selective Ly-6C(high) or Ly-6C(low) MM targeting is suggested to address the contribution of the individual subset to acute stroke pathologic assessment.