Role of ATP and P2X7 receptorin the regulation of the regenerative response in the injured retina of adult zebrafish.

MATIAS MEDRANO; MARIA PAULA FAILLACE

Fox de Iguazu

Congreso; Purines 2018 International - Basic and translational science on purinergic signaling and its components for a healthy and better world; 2018

Brazilian Purine Club and the Organizing Committee of Purines 2018 International

3. Role of ATP and P2X7 receptorin the regulation of the regenerative response in the injured retina of adult zebrafish. Maria Paula Faillace, University of Buenos Aires, Argentina 86FAILLACE, M. P.1;MEDRANO, M. P.1 (1-Instituto de Fisiología y Biofísica (IFIBIO-Houssay),UBA-CONICET; Departamento de Fisiología, Facultad de Medicina, Universidad deBuenos Aires, Ciudad Autónoma De Buenos Aires, Argentina) pfaillace@qb.ffyb.uba.ar  Zebrafish can regenerate retinal neurons to replace those lost by damageor disease. Injury triggers cell cycle reprogramming of multipotent progenitorMüller glia to repair the retina. The P2X7 receptor (P2X7R) has been involvedin the genesis of several retinopathies (Sanderson et al. Exp. Eye. Res. 127;270, 2014) as well as in the control of embryonic progenitor cell proliferationin mammals (Glazer et al. PLoS One 9; e9628, 2014). We have generated andcharacterized an injury model with mainly cytotoxic and possible hypoxia-like components that chiefly kills all photoreceptors in the adultzebrafish retina. By using this injury paradigm we examined the in vivo retinaregenerative response in the presence or absence of a specific P2X7R antagonist(A740003) or an excess of apyrase within the vitreous cavity. We quantified thenumber of proliferative progenitor and microglial cells. We labelledendothelial cells and assessed GFAP immunoreactivity. Quantitative mRNAexpression of different hypoxia-induced and cell proliferation-related geneswas also analyzed by RT-qPCR.Results: lesioned retinas treated with 25 μM A740003 showed asignificant increase in the number of proliferative progenitors including a larger number of dividing nucleiof the GFAP-positive Müller glia. The number of microglial cells around vesselsand proliferation-related gene expression were also significantly enhanced.Vascular endothelial growth factor and its receptors and hypoxia-induced factorgene expression was also modified in the antagonist-treated injured retinas.Likewise, 6 U/ml apyrase-treated injured retinas exhibited a larger number ofproliferative progenitor cells while the number of apoptotic cells increased inall retina layers whereas that of bipolar cells displayed a significantdecrease. On the other hand, in vivotreatments with 1 mM ATPƔS and 500 μM Bz-ATP of uninjured mature retinasprovoked slight activation or injury-induced-like effects, respectively, onmultipotent progenitor cell proliferative activity in the retina layers. In conclusion, the antagonist of P2X7R enhanced overall injury severity.Similar results were observed when extracellular nucleotides were eliminated byan excess of intraocular apyrase. These findings suggest that the P2X7R plays acrucial neuroprotective role in the injured environment of the zebrafish retinasince the selective blockade of its activity had a deleterious impact on thepreviously damaged tissue. In contrast, P2X7R activation with a potent agonist(Bz-ATP) in uninjured retinas provoked a damage-like effect with strongactivation of progenitor Müller glia activity.Grant: UBACYT 0061BA, 2016-2019, Universidad de Buenos Aires ZEBRAFISHRETINA INJURY PARADIGM,PHOTORECEPTOR CELL DEATH, P2X7RANTAGONIST TREATMENT