Nicotinamide mononucleotide prevents iris atrophy-associated corneal endothelial cell loss

Abstract

Purpose : Pathological alteration in the aqueous humor due to iris atrophy leads to corneal endothelial cell (CEnC) loss in humans and mice. Previously, we reported that stress-induced cell senescence and nicotinamide adenine dinucleotide (NAD) metabolic abnormalities of CEnC are involved in its pathogenesis. Nicotinamide mononucleotide (NMN) is reported to enhance NAD biosynthesis and can be beneficial in treating iris atrophy-associated CEnC loss. DBA2J mice develop age-dependent iris atrophy and CEnC loss. Herein, we evaluated the effect of systemic NMN administration on CEnC in DBA2J.

Methods : NMN was administered to 50-week DBA2J in drinking water at the approximately 100 and 300 mg/kg/day of body weight, for four weeks (n=10, each group). Corneas were excised and evaluated by immunohistology and transmission electron microscopy (TEM). CEnC density (CECD) was quantified stained with anti-ZO-1 antibody evaluation. For TEM, ultrathin sections with 70-nm thickness were prepared by ultramicrotome (Leica UC7, Leica Biosystems, Germany) and observed using TEM (JEM-1400plus, JEOL, Japan). Cytokine levels (interleukin [IL]-6, IL-10, interferon-γ, and monocyte chemotactic protein [MCP]-1) in the aqueous humor were measured using Lunaris (Ayoxxa, Germany).

Results : CECD significantly decreased from 2062±199 cells/mm² at the aged 8 weeks to 1541±90 cells/mm² at aged 50 weeks (P=0.0002). CECD was 1661±101 cells/mm² in 50-week DBA2J treated with 100 mg NMN/kg/day for 4 weeks（P=0.0013, compared with 8-week DBA2J and P=0.0533 compared with naïve 50-week) and 1797±221 cells/mm2 in those treated with 300 mg NMN/kg/day (P=0.054 compared with 8-week and P=0.016 compared with naïve 50-week). TEM showed that CEnC microstructures including the mitochondria were normal at 8 weeks, whereas mitochondria and rough endoplasmic reticulum vacuolization was observed at 50 weeks, which significantly improved with systemic NMN administration. The MCP-1, IL-6 and IL-10 levels were significantly higher at 50 weeks than that of those at 8 weeks (all, P<0.01), whereas IL-10 level significantly decreased by 300 mg NMN/kg/day (29.3±27.8 pg/mL, P=0.46 compared with 8-week [5.9±10.3 pg/mL] and P=0.015 compared with naïve 50-week [91.8±21.4 pg/mL]).

Conclusions : NMN administration can prevent iris atrophy-associated CEnC loss.

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