High levels of eye pressure from diseases like glaucoma damage the nerve connecting the eye to the brain (optic nerve). Glaucoma can cause visual impairments, affecting approximately 3 million people in the US. While using eye drops, taking medicines, or having surgery can slow glaucoma’s progression, no cure currently exists. Rodent studies have shown that NMN protects the eye from retinal damage induced by light or detachment. However, no studies have examined how NMN affects eyes with pressure-induced damage, which occurs in diseases like glaucoma.
As published in the International Journal of Molecular Sciences, Kurihara and colleagues from Keio University in Japan demonstrate that injecting 500 mg/kg/day of NMN prevents eye damage from pressure-induced retinal injury in mice. They show that NMN preserves retinal electrical activity by reducing inflammation and rescues retinal cells from death by decreasing oxidative stress. These findings suggest that NMN could preserve eye health in conditions of pressure-induced injury like glaucoma.
To find whether NMN protects against pressure-induced eye injury, the Japanese research team injected a salt solution into the eyes of mice to increase pressure and cause damage. They then examined the retina’s electrical activity in response to flashes of light at varying intensity. It was found that NMN preserves the electrical activity of the inner layer of the retina, suggesting that NMN preserves retinal function in response to pressure-induced injury.
Since elevated inflammation has been associated with eye damage from diseases that raise eye pressure, the Keio University-based researchers looked at the accumulation of inflammatory cells. They found that these cells increased about 50-fold with pressure-induced damage, but NMN treatment substantially rever sed this inflammatory cell accumulation. These findings suggest that NMN could preserve the integrity of the retina by inhibiting the eye’s inflammatory response.
To verify that NMN provides anti-inflammatory benefits to preserve the retina, Kurihara and colleagues examined mouse retinal cells in laboratory dishes exposed to inflammation-inducing oxidative stress. They found that while oxidative stress correlates with high levels of cell death, NMN preserves the survival of retina cells. These findings provide evidence that NMN rescues retina cell death by warding off oxidative stress.
“In summary, we applied the promising NMN therapy to retinal injury in the current study,” said Kurihara and colleagues. “We further found that NMN treatment could protect against oxidative stress-induced retinal cell death.”
The results from the study provide the first evidence of NMN’s beneficial effects on eye pressure-induced damage. Although previous research indicates that NMN mitigates the harmful effects of retinal detachment and light-induced retinal damage to the eye, no study to date has examined how NMN affects eyes exposed to high intraocular pressure levels as seen in diseases like glaucoma, diabetic retinopathy, and vascular ischemic retinopathy. This mouse study begs the question of whether NMN provides benefits to humans with high intraocular pressure as seen in glaucoma. This possibility adds further prospects for NMN’s benefits for eye disorders and may negate the need for invasive surgical treatments.