Spermine Oxidase inhibitor, MDL 72527, reduced neovascularization, vascular permeability, and acrolein-conjugated proteins in a mouse model of ischemic retinopathy

Abstract

Purpose : Disruptions in polyamine metabolism have been implicated in various central nervous system disorders. Research in our laboratory has demonstrated the critical involvement of spermine oxidase (SMOX) in experimental models of retinal neurovascular diseases. However, the impact of SMOX inhibition on ischemic retinopathy and the underlying molecular mechanisms of vascular protection are unclear. Using the oxygen-induced retinopathy (OIR) model and human retinal endothelial cells (HRECs), the present study investigated the effect of SMOX inhibition on retinal neovascularization, vascular permeability, and the molecular mechanisms of MDL 72527-mediated vasoprotection.

Methods : Newborn C57BL6/J mice were subjected to OIR and treated with SMOX inhibitor, MDL 72527, or vehicle during P12-P16. Retinas were processed to study vascular damage using flat-mount analysis and immunofluorescence staining. Western blotting was performed to determine the molecular signaling pathways, and fluorescein angiography was used to study vascular permeability. HRECs were used to investigate the impact of acrolein conjugates (a downstream effector of SMOX) on endothelial cell damage. Statistical analyses were performed using GraphPad Prism.

Results : Our results show that, in comparison with vehicle OIR, SMOX inhibition resulted in a significant reduction in vaso-obliteration (N=6; p<0.01) and neovascularization (N=6, p<0.05) in the OIR retina. Mice who received MDL 72527 treatment demonstrated significantly reduced vascular permeability compared to their vehicle-treated group (N=6; p<0.05). These changes were accompanied by reduced levels of Claudin 5, VEGF, and acrolein-conjugated proteins. Our studies focused on the mechanisms of OIR-induced vascular damage and demonstrated upregulation in the P38/ERK1/2/STAT3 signaling in the retina, which was significantly downregulated in response to SMOX blockade (N=3-7 per group; p<0.05). Further, our results demonstrate that treatment with BSA-Acrolein conjugates significantly reduced the viability of HRECs and activated P38 signaling (N=3; p<0.01).

Conclusions : The results provide valuable insights into the potential therapeutic benefits of SMOX inhibition in ischemic retinopathy.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.