Abstract WMP73: TGFβ-Activated Kinase 1 (TAK1) is a Key Molecular Switch That Drives Proinflammatory Microglia/macrophage Responses and Aggravates Long-Term Stroke Outcomes

Abstract

Introduction: Microglia/macrophages (Mi/MΦ) profoundly influence stroke outcomes, but the molecular mechanisms dictating their functional phenotype after brain ischemia/reperfusion (I/R) are poorly understood. We hypothesized that activation of TAK1, a key MAPKKK upstream of multiple inflammation-regulating pathways, drives Mi/MΦ towards a proinflammatory phenotype and potentiates I/R brain injury. Methods: TAK1 was targeted in mice by tamoxifen-induced, Mi/MΦ-specific knockout (mKO) or a relatively selective inhibitor 5Z-7-oxozeaenol (OZ; 2.5 mg/kg i.p.). Sensorimotor/cognitive deficits, grey/white matter injury and brain inflammatory profiles were assessed after 1 h MCAO and reperfusion. Results: TAK1 mKO markedly ameliorated neurological deficits in the rotarod, cylinder and water maze tests (p<0.05 vs WT, n=10-11/group) for at least 35 d after I/R. Mechanistically, RNA-seq (n=3/group) of FACS-sorted brain Mi (CD45 low ) and MΦ (CD45 high ) cells revealed that multiple genes participating in pro-inflammatory responses were downregulated in both Mi and MΦ from mKO mice versus WT mice 3 d after I/R. Consistent with the phenotype of mKO, OZ mitigated neuroinflammation 3 d after I/R, reflected by less Iba1 + /CD16 + proinflammatory Mi/MΦ and less brain invasion of peripheral immune cells (neutrophils, MΦ, T cells). OZ treatment beginning 2 h after I/R effectively improved long term (35 d) sensorimotor and cognitive functions in the foot fault, rotarod and water maze tests (p<0.05 vs vehicle) in male (n=13-19/group) and ovariectomized female (n=11/group) mice. Furthermore, OZ promoted both gray matter (MAP2/NeuN staining) and white matter (Caspr/Nav1.6 staining) integrity at 35 d after I/R (p<0.05 vs vehicle, n=8/group). Conclusions: TAK1 promotes I/R-induced inflammation, brain injury, and maladaptive behavior by enhancing neurotoxic Mi/MΦ responses. TAK1 inhibition is a promising therapy to improve long term stroke outcomes in both sexes.