Abstract
Purpose :
Corneal endothelial cells (CEnCs) are impaired and reduced in humans and DBA/J2 mice with iris atrophy mediated by a pathological microenvironment of the aqueous humor. Previous multi-omics analyses have revealed that abnormalities in nicotinamide adenine dinucleotide (NAD) metabolism negatively impact CEnCs during bullous keratopathy. NAD is a crucial metabolite involved in genome stability and mitochondrial metabolism, and nicotinamide mononucleotide (NMN) promotes NAD biosynthesis. This study investigated gene expression related to oxidative stress or apoptosis in the cornea, the mitochondrial membrane potential of CEnCs, and the effects of NMN treatment on apoptosis in DBA/J2 mice.
Methods :
DBA/J2 mice, which develop iris atrophy and corneal endothelial reduction with aging, were used in this study. Four 50-week-old mice were orally administered NMN at doses of 100 and 300 mg/kg/day for one week, and their corneas were compared to four untreated 50-week-old mice and eight 8-week-old mice without iris atrophy. The corneas were excised from the mice and the RNA was isolated. cDNA was synthesized from that RNA, and real-time PCR was performed for Bcl-2, Snail1, Rspondin1, Cdkn2a, Nq01, Acta2, and GAPDH. Additionally, NMN at 300 mg/kg/day was administered for four weeks to six 50-week-old mice, and CEnCs were stained with JC-1 and TUNEL for comparison with those of six untreated 50-week-old mice.
Results :
Compared to 8-week-old mice, Bcl-2 expression was significantly increased in 50-week-old mice (P = 0.002, n = 4). However, in 50-week-old mice treated with NMN at 300 mg/kg/day for one week, Bcl-2 expression significantly decreased compared to untreated mice (P = 0.004, n = 4). No significant alterations in the expression of other genes were detected. Although an increase in mitochondrial membrane potential was observed in mice treated with NMN at 300 mg/kg/day for four weeks compared to untreated mice, there was no significant difference in apoptosis according to TUNEL staining.
Conclusions :
Oral administration of NMN in DBA/J2 mice led to alterations in corneal Bcl-2 expression and activation of mitochondrial metabolism.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.