title: Adenosine A3 receptor activation is neuroprotective against retinal neurodegeneration.
abstract: Death of retinal neural cells, namely retinal ganglion cells (RGCs), is a characteristic of several retinal neurodegenerative diseases. Although the role of adenosine A3 receptor (A3R) in neuroprotection is controversial, A3R activation has been reported to afford protection against several brain insults, with few studies in the retina. In vitro models (retinal neural and organotypic cultures) and animal models [ischemia-reperfusion (I-R) and partial optic nerve transection (pONT)] were used to study the neuroprotective properties of A3R activation against retinal neurodegeneration. The A3R selective agonist (2-Cl-IB-MECA, 1 μM) prevented apoptosis (TUNEL(+)-cells) induced by kainate and cyclothiazide (KA + CTZ) in retinal neural cultures (86.5 ± 7.4 and 37.2 ± 6.1 TUNEL(+)-cells/field, in KA + CTZ and KA + CTZ + 2-Cl-IB-MECA, respectively). In retinal organotypic cultures, 2-Cl-IB-MECA attenuated NMDA-induced cell death, assessed by TUNEL (17.3 ± 2.3 and 8.3 ± 1.2 TUNEL(+)-cells/mm(2) in NMDA and NMDA+2-Cl-IB-MECA, respectively) and PI incorporation (ratio DIV4/DIV2 3.3 ± 0.3 and 1.3 ± 0.1 in NMDA and NMDA+2-Cl-IB-MECA, respectively) assays. Intravitreal 2-Cl-IB-MECA administration afforded protection against I-R injury decreasing the number of TUNEL(+) cells by 72%, and increased RGC survival by 57%. Also, intravitreal administration of 2-Cl-IB-MECA inhibited apoptosis (from 449.4 ± 37.8 to 207.6 ± 48.9 annexin-V(+)-cells) and RGC loss (from 1.2 ± 0.6 to 8.1 ± 1.7 cells/mm) induced by pONT. This study demonstrates that 2-Cl-IB-MECA is neuroprotective to the retina, both in vitro and in vivo. Activation of A3R may have great potential in the management of retinal neurodegenerative diseases characterized by RGC death, as glaucoma and diabetic retinopathy, and ischemic diseases.
authors: Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3004-548 Coimbra, Portugal; Glaucoma & Retinal Neurodegeneration Research Group, University College London, London EC1V 9EL, UK. Electronic address: jgalvao@ucsd.edu.
authors: Joana
authors: J
authors: Galvao
authors: Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3004-548 Coimbra, Portugal; Association for Innovation and Biomedical Research on Light (AIBILI), Coimbra 3000-548, Portugal. Electronic address: filipe.elvas@gmail.com.
authors: Filipe
authors: F
authors: Elvas
authors: Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3004-548 Coimbra, Portugal; Association for Innovation and Biomedical Research on Light (AIBILI), Coimbra 3000-548, Portugal. Electronic address: tiagofmendesmartins@gmail.com.
authors: Tiago
authors: T
authors: Martins
authors: Glaucoma & Retinal Neurodegeneration Research Group, University College London, London EC1V 9EL, UK; Western Eye Hospital, Imperial College, London, UK. Electronic address: m.cordeiro@ucl.ac.uk.
authors: M Francesca
authors: MF
authors: Cordeiro
authors: Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3004-548 Coimbra, Portugal; Association for Innovation and Biomedical Research on Light (AIBILI), Coimbra 3000-548, Portugal; CNC.IBILI, University of Coimbra, 3004-517 Coimbra, Portugal. Electronic address: afambrosio@fmed.uc.pt.
authors: António Francisco
authors: AF
authors: Ambrósio
authors: Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3004-548 Coimbra, Portugal; Association for Innovation and Biomedical Research on Light (AIBILI), Coimbra 3000-548, Portugal; CNC.IBILI, University of Coimbra, 3004-517 Coimbra, Portugal. Electronic address: asantiago@fmed.uc.pt.
authors: Ana Raquel
authors: AR
authors: Santiago
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058909:Adenosine A3 Receptor Agonists / Q000494:pharmacology; D058918:Adenosine A3 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival; D004195:Disease Models, Animal; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D019084:Fluorescent Antibody Technique, Indirect; D020287:In Situ Nick-End Labeling; D058449:Intravitreal Injections; D008297:Male; D016202:N-Methylaspartate / Q000633:toxicity; D000066829:Neuroprotection / Q000502:physiology*; D020221:Optic Nerve Injuries / Q000378:metabolism; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D043684:Receptor, Adenosine A3 / Q000378:metabolism*; D012160:Retina / Q000187:drug effects / Q000473:pathology; D012162:Retinal Degeneration / Q000378:metabolism / Q000517:prevention & control*; D055351:Retinal Neurons / Q000378:metabolism*
chemical_list: D058909:Adenosine A3 Receptor Agonists; D058918:Adenosine A3 Receptor Antagonists; D018690:Excitatory Amino Acid Agonists; D043684:Receptor, Adenosine A3; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; D016202:N-Methylaspartate; D000241:Adenosine; C090034:2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide
keywords: A(3) adenosine receptor; Axon injury; Excitotoxicity; Ischemia-reperfusion; Neuroprotection; Retinal ganglion cell