Lutein and candesartan co-treatment attenuates retinal neurodegeneration and glial activation in hyperglycemic Ins2^Akita/+ mice

Abstract

Purpose : Diabetic retinopathy leads to irreversible blindness; its early treatment is crucial to slow sight deterioration. Lutein is a natural xanthophyll shown to be neuroprotective upon retinal ischemia/reperfusion injury while candesartan is an angiotensin receptor antagonist able to restore retinal function in hyperglycemic Ins2^Akita/+ mice. Here, we assessed effects of lutein and candesartan co-treatment in early non-proliferative diabetic retinopathy.

Methods : Male Ins2^Akita/+ mice received the following drug treatment in drinking water starting at 6 weeks old: vehicle; lutein 4.2 mg/kg/d (L4.2); lutein 4.2 mg/kg/d+candesartan 0.01 mg/kg/d (L4.2+C0.01); lutein 4.2 mg/kg/d+candesartan 0.1 mg/kg/d (L4.2+C0.1); candesartan 0.1 mg/kg/d (C0.1). Mice were sacrificed at 4.5, 6.5 and 9 months old (n=4 to 9/group). 5um retinal paraffin sections with optic nerve stump were selected for immunohistochemistry using antibodies against calretinin (amacrine cell), calbindin (horizontal cell), protein kinase C alpha (bipolar cell), glial fibrillary acidic protein (GFAP, astrocyte), and glutamine synthetase (GS, Muller cell). Number of calretinin-immunopositive cells was counted while a scoring system was used to assess immunoreactivity for other markers. Activated microglia were identified and counted on retinal flat-mounts. Data was compared by ANOVA followed by Bonferroni’s post hoc tests.

Results : Ins2^Akita/+ mice displayed loss of retinal neurons and more glial activation when compared with wildtype mice. At 9 months old number of calretinin-immunopositive cells in C0.1 single treatment group and L4.2+C0.1 co-treatment group were significantly larger. Calbindin immunoreactivity was the highest with L4.2+C0.01 co-treatment while highest PKCalpha immunoreactivity was obtained with C0.1 single treatment. GS and GFAP expression were significantly reduced by L4.2 single treatment in older groups while L4.2+C0.1 co-treatment significantly decreased GFAP level at 9 months old only. Density of reactive microglia was reduced by all treatments.

Conclusions : Better preservation of retinal neurons was observed after candesartan single treatment or co-treatment while lutein single treatment or co-treatment resulted in lower glial activation. Thus, early lutein and candesartan co-treatment could protect the retina against retinal neurodegeneration and glial activation in diabetic retinopathy.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.