Role of the Immune Modulator Programmed Cell Death-1 during Development and Apoptosis of Mouse Retinal Ganglion Cells

Abstract

PURPOSE Mammalian programmed cell death-1 (PD-1) is a membrane-associated receptor regulating the balance between T cell activation, tolerance and immunopathology, however its role in neurons has not yet been defined. We investigate the hypothesis that PD-1 signaling actively promotes retinal ganglion cell (RGC) death within the developing mouse retina. METHODS Mature retinal cell types expressing PD-1 were identified by immunofluorescence staining of vertical retina sections; developmental expression was localized by immunostaining and quantified by Western analysis. PD-1 involvement in developmental RGC survival was assessed in vitro using retina explants and in vivo using PD-1 knockout mice. PD-1 ligand gene expression was detected by RT-PCR. RESULTS PD-1 is expressed in most adult RGCs, and undergoes dynamic upregulation during the early postnatal window of retinal cell maturation and physiological programmed cell death (PCD). In vitro blockade of PD-1 signaling during this time selectively increases survival of RGCs. Furthermore, PD-1 deficient mice show a selective increase in RGC number in the neonatal retina at the peak of developmental RGC death. Lastly, throughout postnatal retina maturation, we find gene expression of both immune PD-1 ligand genes, PD-L1 and PD-L2. CONCLUSIONS These findings collectively support a novel role for a PD-1-mediated signaling pathway in developmental PCD during postnatal RGC maturation.

Programmed cell death-1 is expressed in large retinal ganglion cells and is upregulated after optic nerve crush

“…Concordant with its functions in the immune system, we further demonstrated that PD-1 and its partner(s) play an important role in RGC death during retinal development (Chen et al, 2009b; Sham et al, 2012). It is known that pathological RGC degeneration may share the same mechanisms as those in physiological RGC loss; therefore, we investigated whether PD-1 is involved in RGC apoptosis in pathological settings.…”

“…In the developing retina, PD-1 expression undergoes dynamic regulation and correlates with the time of active RGC culling (Chen et al, 2009b). The level of PD-1 expression decreases after the early postnatal stage, and remains low but measurable in the adult retina.…”

“…Our group previously found that PD-1 is expressed in more than 95% of RGCs in the adult retina, studies that were performed in vertical retinal sections (Chen et al, 2009b). In the current study, employment of retinal flatmounts allowed us to further characterize the PD-1 expression pattern in the mouse retina.…”

B7-H1 Selectively Controls TH17 Differentiation and Central Nervous System Autoimmunity via a Novel Non–PD-1–Mediated Pathway

“…This result was unexpected, because several studies proposed that this pathway primarily affects generation of IFN-g-producing T H 1 cells (41)(42)(43)(44). Another aspect that argues against a general interference with T cell responses by B7-H1 is the selective promoting effect of B7-H1-Ig on murine TGF-bmediated inducible T reg (iT reg ) differentiation, in line with other studies (30,45,46). However, it has been reported that induction of iT reg generation and function by B7-H1 is mediated via PD-1 (30,46).…”

Astrocyte-derived lipoxins A4 and B4 promote neuroprotection from acute and chronic injury

“…For each eye, at least 5 central retinal sections were analyzed at the level of the ON to the periphery and the results averaged, as previously described (14). In parallel, TUNEL-positive GCL nuclei were counted and expressed as a fraction of the total GCL nuclei (58,(73)(74)(75)(76). For in vitro experiments, RGCs were isolated, treated, and probed with an antibody to β3-tubulin and imaged as above.…”