Damaging effects of the cyanotoxin BMAA in cultured retinal neurons and Müller glial cells: neuroprotection by retinoid X receptor (RXR) activation

SOTO, T. B.; TENCONI, P. E.; BUZZI E.; MATEOS, M.; GERMAN O. L.

Simposio; Simposio Frontiers in Neuroscience 4; 2023

The cyanotoxin, β-methylamine-L-alanine (BMAA), is related to the development of neurodegenerative diseases. We demonstrated that BMAA promotes cell death in cultured amacrine and photoreceptor neurons (PHRs), and that Müller glial cells (MGCs), cannot prevent this degeneration. In addition, the activation of Retinoid X Receptors (RXR) protects different retinal cells from oxidative stress-induced apoptosis.In this work, we studied the direct effects of BMAA on neurons and MGCs in pure retinal neuronal and glial cultures, respectively, obtained from newborn rat retinas. For that, neuronal cultures were pre-treated with 1 µM HX630, a RXR agonist, and incubated with 0.4 µM BMAA for 3 days. Besides, glial cultures were treated with BMAA 0.4, 1 and 10 µM, in a short (during 3-days) and long-term (during 9-days). We evaluated nuclear morphology and cell death by DAPI staining and apoptosis by TUNEL assay; ROS levels using the DCDCDHF probe; lysosomal activity by Lysotracker assay; and by immunocytochemistry the Lamin-A expression and the Poly(ADP-ribose) polymer (PAR) levels.In pure neuronal cultures, pre-treatment with HX630 prevented BMAA-induced increase in fragmented nuclei, and apoptosis in PHRs, and blocked the increase in fragmented nuclei in amacrine neurons. Furthermore, our preliminary results showed that BMAA induced PAR expression in both neuronal types and HX630 pre-treatment diminished it.Moreover, in long-term exposure of glial cultures to BMAA, MGCs displayed nuclear deformation with altered nuclear Lamin-A morphology. Additionally; BMAA (0.4 and 1 µM) promoted ROS generation in short-term, but not in long-term studies. Moreover, our preliminary results showed that BMAA increased the lysosomal activity in MGC in long-term cultures. These results suggest that activation of RXR can prevent the deleterious effects of BMAA on retinal neurons and that BMAA induces several subcellular alterations in MGCs. These results might contribute to the development of novel therapeutic strategies for retinopathies associated with BMAA exposure.