Protective Effects of Lipoxin A₄ and B₄ Signaling on the Inner Retina in a Mouse Model of Experimental Glaucoma

Glaucoma is a common neurodegenerative disease characterized by progressive degeneration of retinal ganglion cells (RGCs) and the retinal nerve fiber layer (RNFL), resulting in a gradual decline of vision. A recent study by our groups indicated that the levels of lipoxins A₄ (LXA₄) and B₄ (LXB₄) in the retina and optic nerve decrease following acute injury, and that restoring their function is neuroprotective. Lipoxins are members of the specialized pro-resolving mediator (SPM) family and play key roles to mitigate and resolve chronic inflammation and tissue damage. Yet, knowledge about lipoxin neuroprotective activity remains limited. Here we investigate the in vivo efficacy of exogenous LXA₄ and LXB₄ administration on the inner retina in a mouse model of chronic experimental glaucoma. To investigate the contribution of LXA₄ signaling we used transgenic knockout (KO) mice lacking the two mouse LXA₄ receptors (Fpr2/Fpr3^-/-). Functional and structural changes of inner retinal neurons were assessed longitudinally using electroretinogram (ERG) and optical coherence tomography (OCT). At the end of the experiment, retinal samples were harvested for immunohistological assessment. While both lipoxins generated protective trends, only LXB₄ treatment was significant, and consistently more efficacious than LXA₄ in all endpoints. Both lipoxins also appeared to dramatically reduce Müller glial reactivity following injury. In comparison, Fpr2/Fpr3 deletion significantly worsened inner retinal injury and function, consistent with an essential protective role for endogenous LXA₄. Together, these results support further exploration of lipoxin signaling as a treatment for glaucomatous neurodegeneration.