Abstract WP260: The Response Of Annexin A1 In Astrocyte Activation And White Matter Injury- A New Target For Stroke In Sickle Cell Disease

Abstract

Introduction: Ischemic stroke is common in sickle cell disease (SCD). White matter injuries, incorporated into silent cerebral infarcts, are major risk factors of stroke in SCD. The pathogenesis of cerebral infarction in SCD is not known. Induced thrombogenesis may cause impaired astrocyte that stimulates demyelination leading to white matter injury. Annexin A1 (Anxa1) can regulate astrocyte function by inhibiting intracellular phospholipase A2 (PLA2). We hypothesized that astrocyte activation during thrombogenic events promotes white matter injury in SCD. We tested astrocyte dysfunction and white matter injury in a clinically relevant mouse model of SCD. Methods: Cerebral Infarctions induced by de novo thrombogenesis were identified by TTC staining in transgenic sickle (SS) and control (AA) mice with human sickle and normal hemoglobin respectively. Cerebral microvessels and astrocytes were isolated from SS and AA mice. Elisa assays were used to measure thrombin, PLA2 and Anxa1. Immunofluorescence staining was performed to determine astrocyte activation and demyelination. Results: Thrombogenesis within cerebral microvessels was elevated by ~2-fold (n=5, p<0.05), and cerebral infarction became prevalent in SS mice compared to AA mice (n=7, p<0.001). The infarcted brain tissue from SS mice showed neuronal cell death, whereas the brain tissue from the AA mice appeared normal. The SS mice had increased glial fibrillary acid protein positive (GFAP + ) activated astrocytes with significant increase in PLA2 accumulation. Relative abundance of non-phosphorylated neurofilament H (SMI32) and myelin basic protein (MBP) (SMI32/MBP), indicating white matter injury, was substantially induced in the SS compared to the AA. Expression of Anxa1 reduced significantly in plasma as well as within astrocytes’ end feet attached to the isolated cerebral microvessels of the SS mice. Recombinant Anxa1 prophylaxis to SS mice reduced the GFAP + astrocytes, PLA2 accumulation, demyelination and infarct score (n=6, p<0.01) compared to SS mice treated with vehicle. Conclusion: White matter injury in SS mice is associated with astrocyte dysfunction and lack of Anxa1, which may be developed as potential therapeutic targets to prevent and/or treat stroke in SCD.