Highlights:

  • NMN treatment reduces lung damage and lung scarring in mice exposed to silica — a mineral constituent of sand found in industrial materials like concrete.
  • Reduced inflammatory cells were seen in the lungs of mice treated with NMN.
  • NMN increases glutathione — a potent antioxidant associated with mitigating the effects of aging.  

Aging is often associated with an increased risk of lung injury and lung disease, and advanced age has been shown to lead to an enhanced inflammatory response to lung assaults. Now, a recent study shows that nicotinamide mononucleotide (NMN) treatment may reduce injury due to silica inhalation, possibly modeling NMN’s ability to help reduce injury due to other inhaled particulates.

The study, out of China, published in Nutrients, focused on male mice subjected to silica-induced lung injury, or silicosis. Silicosis promotes cellular damage — oxidative stress — by increasing reactive oxygen species (ROS) – highly reactive oxygen-containing molecules. Treating mice with NMN reduced lung damage, leading to positive tissue changes and reduced inflammation. Additionally, oxidative stress was decreased, ROS reduced, and glutathione increased. 

“This study reveals that NMN supplementation might be a promising strategy for mitigating oxidative stress and inflammation in silicosis,” the scientists wrote.

NMN Reduces Lung Tissue Damage in Silicosis

To model silicosis, silica was introduced directly into the trachea of mice. The mice were then  treated with either saline (meaning no treatment), low-dose NMN (500 mg/kg/day), or high-dose NMN (1000 mg/kg/day). After 28 days, both doses of NMN reduced collagen within the lungs – indicative of decreased lung scarring. NMN treatment also maintained the structure of alveoli – air sacs in the lungs where oxygen is exchanged.  

(Wang et al., 2023 | Nutrients) NMN Reduces Lung Injury in Silicosis Model. Compared to normal mice (Sham), mice exposed to silica (Vehicle) display increased lung scarring, as measured by the B) Ashcroft score and C) collagen volume fraction. However, high (NMN-H) and low (NMN-L) dose NMN reduces scarring. NMN-Con = no silica with NMN. #### difference from untreated (Vehicle) mice ** difference between low and high dose NMN.

Silica particles are nearly impossible for the body to degrade, leading to continuous damage to the lungs via oxidative stress. This oxidative stress recruits inflammatory cells to the site of damage, inducing more inflammation. However, the researchers found that with NMN treatment, this cycle of continuous assault was prevented with NMN restoring inflammatory cell levels back to nearly normal levels after 28 days of treatment.

(Wang et al., 2023 | Nutrients) NMN Reduces Infiltrating Inflammatory Cells in Silicosis Model. High (NMN-H) and low (NMN-L) dose NMN reduces the percent of macrophages – infiltrating inflammatory cells – in the lungs of mice exposed to silica (Vehicle), close to levels of mice that did not have silica injuries or NMN treatment (Sham).  NMN-Con = no silica with NMN. #### difference from untreated (Vehicle) mice.

Furthermore, Wang and colleagues found that, after 28 days, both high and low doses of NMN effectively decreased ROS. Additionally, glutathione – a key antioxidant that neutralizes ROS – was increased with NMN,suggesting that NMN can help reduce the oxidative stress caused by silica. 

(Wang et al., 2023 | Nutrients) NMN Decreases Reactive Oxygen Species and Increases Glutathione Levels. High (NMN-H) and low (NMN-L) doses of NMN decrease D) ROS (Mean fluorescent intensity) and increase F) glutathione (GSH) levels in the lungs of mice exposed to silica (Vehicle), close to normal mice (Sham). NMN-Con = no silica with NMN.  #### difference from untreated (Vehicle) mice ** difference between low and high dose NMN.

NMN for Lung Injuries

Wang and colleagues show that NMN may be a promising treatment for silicosis. Other models of lung injury, including sepsis-induced lung injuries and cigarette-induced lung fibrosis, have also been shown to be positively affected by NMN treatment. These studies hold promise for both those affected by lung injury, as well as those affected by aging lung tissue. With NMN effectively reducing oxidative stress in the lungs, it holds the possibility of doing the same for aging tissue. 

Previous work has actually shown that NMN helps to reduce signs of aging and functional decline in the lungs of old mice. However, clinical research studies with long-term follow-up are needed before determining the full extent of NMN’s benefits on human lungs.