Abstract WMP112: Type 2 Diabetes Dampens Neuroprotection Against Ischemic Injury By Lipopolysaccharide-Induced Preconditioning

Abstract

Introduction: Evidence suggests that lipopolysaccharide ( LPS ) preconditioning (PC) provides neuroprotection by inducing tolerance to subsequent lethal ischemia. Ischemic tolerance (IT) declines with age, yet it is unclear whether metabolic disease like type 2 diabetes (T2DM) also interfere with IT. The current study sought to determine whether T2DM reduces neuroprotection induced by LPS PC, and the molecular mechanisms underlying the dampened IT. Methods: Male and female diabetic db/db and control db/+ mice (8-10 months of age) were i.p. injected with Toll-like receptor (TLR)4 ligand LPS at 0.2 mg/kg or saline. Stroke was induced 3 days later by permanent distal occlusion of middle cerebral artery and temporary occlusion of ipsilateral common carotid artery for 60 min. Sensory and motor function was evaluated 1 day after stroke by a combination of tests. Infarct size was determined 3 days after stroke following TTC staining. The effect of LPS PC on the phenotypes of leukocytes in the brain parenchyma after stroke was quantified by Fluorescent activated cell sorter (FACS) 2 days after stroke with a panel of markers for subsets of myeloid cells. Transcriptome was determined by RNAseq of isolated monocytes from peripheral blood mononuclear cells. Differentially expressed genes were examined for distinct biological pathways via enrichment analysis. Results: LPS PC significantly reduced infarct in db/+ mice by one third and improved neurological scores, but it did not protect the db/db mice from stroke. FACS data showed that LPS PC reduced the number of Ly6G+ cells in db/+ but not db/db brains, suggesting that LPS PC curbed stroke-induced infiltration of neutrophils in the brain parenchyma. Pathway analysis suggests that diabetic mice exhibited down-regulated pathways in interferon signaling. The expression of Jak-Stat signaling (such as Stat1), MHC antigen presentation (H2A family), and Toll-like receptor (TLR) signaling (such as Irf7) were also reduced in diabetic mice after stroke. Conclusions: The dampened IT in the diabetic mice induced by LPS-PC is associated with increased neutrophil infiltration after stroke compared to control mice. Ongoing studies will seek toovercome the underlying defective molecular mechanisms in T2DM.