Retinal ganglion cell loss and gliosis in the retinofugal projection following intravitreal exposure to amyloid-beta

Pathological accumulations of amyloid-beta (A beta) peptide are found in retina early in Alzheimer's disease, yet its effects on retinal neuronal structure remain unknown. To investigate this, we injected fibrillized A beta(1-42) protein into the eye of adult C57BL/6 J mice and analyzed the retina, optic nerve (ON), and the superior colliculus (SC), the primary retinal target in mice. We found that retinal A beta exposure stimulated microglial activation and retinal ganglion cell (RGC) loss as early as 1-week post-injection. Pathology was not limited to the retina, but propagated into other areas of the central nervous system. Microgliosis spread throughout the retinal projection (retina, ON, and SC), with multiplex protein quantitation demonstrating an increase in endogenously produced A beta in the ON and SC corresponding to the injected retinas. Surprisingly, this pathology spread to the opposite side, with unilateral A beta eye injections driving increased A beta levels, neuroinflammation, and RGC death in the opposite, un-injected retinal projection. As A beta-mediated microglial activation has been shown to propagate A beta pathology, we also investigated the role of the A beta-binding microglial scavenger receptor CD36 in this pathology. Transgenic mice lacking the CD36 receptor were resistant to A beta-induced inflammation and RGC death up to 2 weeks following exposure. These results indicate that A beta pathology drives regional neuropathology in the retina and does not remain isolated to the affected eye, but spreads throughout the nervous system. Further, CD36 may serve as a promising target to prevent A beta-mediated inflammatory damage.

Automated summary

The study revealed that exposure to A beta (1-42) protein in the retina can stimulate microglial activation and cause RGC loss, with pathology spreading beyond the retina into other areas of the central nervous system. CD36 may serve as a promising target to prevent A beta-mediated inflammatory damage.