Purinergic receptor P2X7 regulates the proliferative, vascular and inflammatory response in the injured retina of adult zebrafish

MEDRANO MP; FAILLACE MP

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de BioCiencias 2017; 2017

SAIC, SAFIS, SAFE, SAIB, SAA, SAI, SAB, SAB, SAH, SAP

Unlike mammals, zebrafish can regenerate retinal neurons to replace those lost by injury. Injury-responsive Müller cells inzebrafish show cell cycle reprogramming to repair the retina. The P2X7 receptor(P2X7R) has been involved in the genesis of several retinopathies as well as in the control of embryonic stem cell proliferation and neural differentiationin mammals. We have characterized an injury model with mainly cytotoxic and possiblehypoxia-like components that chiefly kills all photoreceptors in the adult zebrafishretina. By using this injury paradigm we examined the in vivo retina regenerative response in the presence or absence ofa specific P2X7R antagonist (A740003) or an excess of apyrase within thevitreous cavity. We quantified the number of proliferative progenitor andmicroglial cells. We labeled endothelial cells and assessed GFAPimmunoreactivity. Quantitative mRNA expression of different hypoxia-induced andcell proliferation-related genes was also analyzed by RT-qPCR.Results: lesioned retinas treatedwith 25 µM A740003 showed a significant increase in the number of proliferativeprogenitors including a larger number of dividing nuclei of the GFAP-positiveMüller glia. The number of microglial cells around vessels and proliferation-relatedgene expression were also significantly enhanced. Vascular endothelial growthfactor and its receptors and hypoxia-induced factor gene expression was alsomodified in the antagonist-treated injured retinas. Likewise, 6 U/ml apyrase-treatedinjured retinas exhibited a larger number of proliferative progenitor cellswhile the number of apoptotic cells increased in all retina layers whereas thatof bipolar cells displayed a significant decrease. On the other hand, in vivo treatments with 1 mM ATPƔS and 500µM Bz-ATP of uninjured mature retinas provoked slight or injury-induced-likeeffects, respectively, on multipotent progenitor cell proliferative activity inthe retina layers.In conclusion, the antagonist ofP2X7R enhanced overall injury severity. Similar results were observed whenextracellular nucleotides were eliminated by an excess of intraocular apyrase. Thesefindings suggest that the P2X7R plays a crucial neuroprotective role in the injuredenvironment of the zebrafish retina since the selective blockade of itsactivity had a deleterious impact on the previously damaged tissue. Incontrast, P2X7R activation with a potent agonist (Bz-ATP) in uninjured retinasprovoked a damage-like effect with strong activation of progenitor Müller gliaactivity.