title: Clearance of apoptotic photoreceptors: elimination of apoptotic debris into the subretinal space and macrophage-mediated phagocytosis via phosphatidylserine receptor and integrin alphavbeta3.
abstract: The effective phagocytotic clearance of apoptotic debris is fundamental to the maintenance of neural tissues during apoptosis. Retinal photoreceptors undergo apoptosis after retinal detachment. Although their induction phase of apoptosis has been well discussed, their phagocytotic process remains quite unclear. We herein demonstrate that apoptotic photoreceptors are selectively eliminated from their physiological localization, the outer nuclear layer, to the subretinal space, and then phagocytosed by monocyte-derived macrophages. This could be shown by an ultrastructural and immunophenotypic analysis. Moreover, in chimera mice expressing transgenic green fluorescent protein in bone marrow-derived cells, the local infiltration of macrophages could be detected after retinal detachment-induced photoreceptor apoptosis. The local injection of an antibody blocking the phosphatidylserine receptor (PSR) or a peptide (GRGDSP)-blocking integrin alphavbeta3 revealed that phagocytotic clearance involves the PSR as well as integrin alphavbeta3 in vivo. Importantly, the level of blockade obtained with these reagents was different. Although anti-PSR increased the frequency of apoptotic cells that fail to bind to macrophages, GRGDSP prevented the engulfment (but not the recognition) of apoptotic photoreceptor cells by macrophages. To our knowledge, this is the first report describing the mechanisms through which apoptotic photoreceptors are selectively eliminated via a directional process in the subretinal space.
authors.affiliation: Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. hisatomi@med.kyushu-u.ac.jp
authors.forename: Toshio
authors.initials: T
authors.lastname: Hisatomi
authors.forename: Taiji
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Koh-Hei
authors.initials: KH
authors.lastname: Sonoda
authors.forename: Chikako
authors.initials: C
authors.lastname: Tsutsumi
authors.forename: Hong
authors.initials: H
authors.lastname: Qiao
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Enaida
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yamanaka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kubota
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Ishibashi
authors.forename: Shinobu
authors.initials: S
authors.lastname: Kura
authors.forename: Santos A
authors.initials: SA
authors.lastname: Susin
authors.forename: Guido
authors.initials: G
authors.lastname: Kroemer
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis; D051033:Apoptosis Inducing Factor; D005420:Flavoproteins / Q000032:analysis; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D016130:Immunophenotyping; D020287:In Situ Nick-End Labeling; D039302:Integrin alphaVbeta3 / Q000276:immunology / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D008565:Membrane Proteins / Q000032:analysis; D051379:Mice; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D009842:Oligopeptides / Q000494:pharmacology; D010587:Phagocytosis / Q000187:drug effects; D010786:Photoreceptor Cells / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D051381:Rats; D011914:Rats, Inbred BN; D011956:Receptors, Cell Surface / Q000276:immunology / Q000502:physiology*; D012160:Retina / Q000378:metabolism* / Q000473:pathology; D012162:Retinal Degeneration / Q000378:metabolism / Q000473:pathology
chemical_list: C494831:Aifm1 protein, rat; D000906:Antibodies; D051033:Apoptosis Inducing Factor; D005420:Flavoproteins; D039302:Integrin alphaVbeta3; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009842:Oligopeptides; C494830:AIFM1 protein, mouse; C498708:Ptdsr protein, mouse; D011956:Receptors, Cell Surface; C408123:phosphatidylserine receptor; D049452:Green Fluorescent Proteins; C047981:arginyl-glycyl-aspartic acid