Secretion of Down Syndrome Critical Region 1 Isoform4 in ischemic retinal ganglion cells displays anti-angiogenic properties via NFATc1-dependent pathway

Abstract

Purpose : Down syndrome candidate region 1 (DSCR1) plays a role in number of physiological processes, such as inhibition of cardiachypertrophy, attenuation of angiogenesis and cancer, and protection against neuronal death, but the function of DSCR1 in the retina is still not clear. We hypothesize that DSCR1 may play an important role in ischemic retina via nuclear factor of activated T-cell (NFATc) 1-dependent pathway. In this study, we used an oxygen-induced retinopathy (OIR) model to analyze DSCR1 expression location in retina and its effects on angiogenesis.

Methods : The neonatal C57BL/6J mice were exposed to 75% O₂ for 5 days from postnatal day 7 (P7) to P12. At P12, the mice were returned to 21 % O₂ at room air. The primary retinal ganglion cells (RGCs) were exposed to hypoxia (93% N₂, 5% CO₂ and 2% O₂) at 37°C for 36 hours (h). And then the mouse retinal microvascular endothelial cells (mRMECs) treated with 25 ng/mL vascular endothelial growth factor (VEGF) or culture medium conditioned by hypoxic RGCs alone, hypoxic RGCs treated with siRNA to DSCR1-4 (siDSCR1-4) or hypoxic RGCs treated with siDSCR1-4 and 200 ng/ml Cyclosporin A (CsA), and then primed with VEGF (25 ng/mL).

Results : The expression of DSCR1-4 increased strongly at P16 in OIR compared to the control. There was no change in mRNA expression of DSCR1-1 at P16 in OIR. The increased DSCR1 was mainly located in the RGCs of avascular retina. In addition, DSCR1-4 expression was increased in primary RGCs after hypoxia exposure. There was no change in mRNA expression of DSCR1-1 in primaryRGCs after hypoxia exposure. Moreover, DSCR1-4 produced by hypoxic RGCs showed anti-angiogenic properties, with decreased cell proliferation, migration, tube formation, inflammatory cytokines production. These properties were incurred from inhibiting NFATc1 dephosphorylation and translocation into nuclear in VEGF-induced mRMECs. Using siRNA-mediated knockdown of DSCR1-4 and NFATc1 inhibitor (CsA), we found that DSCR1-4 inhibited angiogenesis in VEGF-induced mRMECs, and this effect was NFATc1-dependent.

Conclusions : This report describes novel DSCR1-4 anti-angiogenic effects, suggesting potential therapeutic strategies for proliferative retinopathies.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.