Stroke is the most common cause of long-term disability, and there are no known drug therapies to improve recovery after stroke. To understand how successful recovery occurs, dissect candidate molecular pathways, and test new therapies, there is a need for multiple distinct mouse stroke models, in which the parameters of recovery after stroke are well defined. Hypoxic–ischemic stroke is a well-established stroke model, but behavioral recovery in this model is not well described. We therefore examined a panel of behavioral tests to see whether they could be used to quantify functional recovery after hypoxic–ischemic stroke. We found that in C57BL/6J mice this stroke model produces high mortality (approximately one-third) and variable stroke sizes, but is fast and easy to perform on a large number of mice. Horizontal ladder test performance on day 1 after stroke was highly and reproducibly correlated with stroke size (P < 0.0001, R2 = 0.7652), and allowed for functional stratification of mice into a group with >18% foot faults and 2.1-fold larger strokes. This group exhibited significant functional deficits for as long as 3 weeks on the horizontal ladder test and through the last day of testing on automated gait analysis (33 days), rotarod (30 days), and elevated body swing test (EBST) (36 days). No deficits were observed in an automated activity chamber. We conclude that stratification by horizontal ladder test performance on day 1 identifies a subset of mice in which functional recovery from hypoxic–ischemic stroke can be studied.

Presenilin 1 (PS1) and Presenilin 2 (PS2) are the enzymatic component of the γ-secretase complex that cleaves amyloid precursor protein (APP) to release amyloid beta (Aβ) peptide. PS deficiency in mice results in neuroinflammation and neurodegeneration in the absence of accumulated Aβ. We hypothesize that PS influences neuroinflammation through its γ-secretase action in CNS innate immune cells. We exposed primary murine microglia to a pharmacological γ-secretase inhibitor which resulted in exaggerated release of TNFα and IL-6 in response to lipopolysaccharide. To determine if this response was mediated by PS1, PS2 or both we used shRNA to knockdown each PS in a murine microglia cell line. Knockdown of PS1 did not lead to decreased γ-secretase activity while PS2 knockdown caused markedly decreased γ-secretase activity. Augmented proinflammatory cytokine release was observed after knockdown of PS2 but not PS1. Proinflammatory stimuli increased microglial PS2 gene transcription and protein in vitro. This is the first demonstration that PS2 regulates CNS innate immunity. Taken together, our findings suggest that PS2 is the predominant γ-secretase in microglia and modulates release of proinflammatory cytokines. We propose PS2 may participate in a negative feedback loop regulating inflammatory behavior in microglia.