AIBP-mediated neuroprotection in glaucomatous optic neuropathy

青光眼是全球失明的主要原因，胶质细胞驱动的神经炎症是青光眼的关键因素

Glaucoma is a leading cause of blindness worldwide and glia-driven neuroinflammation is a key element in the pathogenesis of glaucoma. Increasing evidence from clinical studies indicate that primary open-angle glaucoma is linked to single-nucleotide polymorphisms of toll-like receptor 4 (TLR4), mitochondrial cytochrome c oxidase subunit I of the oxidative phosphorylation (OXPHOS) complex-IV, ATP-binding cassette transporter A1 and Cholesterol-24S-hydroxylase, suggesting that TLR4-mediated neuroinflammation, cholesterol efflux and/or OXPHOS stress-mediated mitochondrial dysfunction play roles in glaucoma pathogenesis. ApoA-I binding protein (AIBP), encoded by the APOA1BP gene, is a secreted protein, which serves as a selective regulator of cellular cholesterol metabolism, targeting inflammatory cells via its binding to TLR4. Cholesterol depletion from inflammatory cells reduces lipid raft abundance and the membrane occupancy of receptors (such as TLR4) that mediate inflammatory signaling. Emerging evidence from our group showed that AIBP deficiency is associated with glia-driven inflammatory TLR4/interleukin-1β signaling axis and mitochondrial dysfunction in glaucomatous degeneration. In addition to protecting retinal ganglion cells (RGCs) against neuroinflammation, AIBP prevents RGC mitochondrial dysfunction in glaucomatous neurodegeneration. In preliminary studies, we demonstrated that AIBP expression is highly reduced in glaucomatous human and mouse RGCs and their axons, as well as Müller glia, and that amplification of retinal AIBP expression by adeno-associated virus delivery protects RGCs and preserves visual function in experimental glaucoma in vivo. In addition, treatment with recombinant AIBP protein promotes mitochondrial function in Müller glia against elevated pressure in vitro. Based on our previous and these findings, we propose to test the novel concept that AIBP controls retinal neuroinflammation and the RGC mitochondrial dysfunction, which lead to glaucomatous neurodegeneration, as well as to test the therapeutic potential of raising AIBP expression in the retina. The Specific Aims of this proposal are: (1) to define the mechanisms by which AIBP controls TLR4-lipid raft activation in inflammatory Müller glial cells; (2) to determine the protective mechanisms of AIBP amplification on mitochondrial network and bioenergetics in glaucomatous RGCs and Müller glial cells; and (3) to determine how therapeutic augmentation of AIBP expression impacts structural integrity and synapses linking RGCs and the central visual pathway. Our proposed studies will explore novel pathways which potentially link neuroinflammation regulation to elevated IOP-mediated mitochondrial function and cellular cholesterol metabolism. This work may also lead to the development of a new glaucoma therapy.