Abstract P773: Autotaxin and Lysophosphatidic Acid Impair Blood Brain Barrier and Mitochondria Following Ischemic Stroke

Abstract

Introduction: Ischemic stroke is a leading cause of death and a serious cause of long-term disability in the US. r-TPA is the only treatment available for stroke. Only 5% of patients receive it, as others have the risk of intracerebral hemorrhage. Ischemic reperfusion (I/R) following stroke exacerbates the condition and initiates various molecular signals, ultimately interrupting blood-brain barrier BBB so, better therapy is in need. Lysophosphatidic acid (LPA) is a bioactive lipid regulating various essential cellular functions such as migration, proliferation, adhesion. Autotaxin (ATX) produces LPA, which then regulates through its six G-protein coupled receptors. Methods: Transient middle cerebral artery occlusion (MCAO) with 90 minutes of ischemia and 24 hours of reperfusion was used as a stroke model in mice. LPA was analyzed in plasma with mass spectrometry and in tissue with immunohistochemistry. AR-2 probe fluorescence measured ATX activity. Seahorse analyzer measured the mitochondrial bioenergetics in brain and mouse brain microvascular endothelial cells (MBMEC). Permeability was studied with Electric Cell Substrate Impedance System. Results: ATX was elevated in mRNA level with 1.7 fold increased activity following I/R. LPA showed a significant (P<0.01) increase in the plasma of MCAO mice. LPA in the brain tissue of MCAO mice revealed an increased synthesis of LPA by ATX following I/R injury. Brain mitochondria isolated following I/R injury had significantly (P<0.01) reduced the mitochondrial oxygen consumption rate (OCR). Permeability measured in MBMECs showed LPA treatment increases the permeability. Also, the protein levels of junctional proteins such as βcatenin, Claudin5, VEcadherin, and Zo1 were significantly (P<0.05) decreased with LPA exposure. LPA, as a negative regulator of the BBB, caused permeability through LPA-LPAR1-ROCK dependent pathway. MBMECs show impaired mitochondrial function with decreased OCR and elevated glycolysis towards LPA treatment (P<0.01). Conclusion: We have shown that LPA and its regulator enzyme ATX play a significant role in ischemic stroke, increasing BBB permeability, and elevating mitochondrial dysfunction. ATX inhibitors as therapy could improve the condition of stroke patients.