Publishing in Environmental Health Perspectives, researchers from Sun Yat-sen University in China show that PM exposure significantly reduces NAD+ levels in the lungs, which may lead to inflammation and lung damage in mice. Supplementation with NMN, the precursor of NAD, has been shown to restore NAD+ levels, and additionally, NMN supplementation can also prevent severe lung injury from PM exposure.
During the experiment, the researchers further confirmed that NMN could prevent severe lung damage by reducing inflammation, as it reduced the levels of the inflammatory protein TNF-α during PM exposure.
These results suggest that NMN supplementation can attenuate PM exposure-induced lung injury and systemic inflammation, which is very helpful for people living in air-polluted environments, especially urban environments.
To test whether PM exposure affects inflammation and subsequent lung damage from reduced NAD+ levels, the researchers placed mice in a room with high PM levels for 16 weeks.
After mice were exposed to PM, the researchers measured NAD+ levels in different tissues. They found that NAD+ levels decreased by 39.86% in the lungs, 37.28% in the liver and 41.20% in the spleen. These data suggest that the deleterious effects of PM exposure on the lungs can be attributed at least in part to lower NAD+ levels.
16 weeks of PM exposure significantly reduced NAD+ levels in different tissues of mice. After PM exposure (Exp), compared with unexposed healthy mice, NAD+ content in lung decreased by 39.86%, NAD+ content in liver decreased by 37.28%, and NAD+ content in spleen decreased by 41.20% (Con).
Since NMN supplementation has been shown to increase NAD+ levels, researchers sought to determine whether NMN (500 mg/kg/day) could attenuate PM-induced lung injury by adding NMN (500 mg/kg/day) to the drinking water of mice.
NMN prevents acute lung injury (ALI) in PM-exposed mice. The ALI score is calculated based on parameters such as protein debris and the presence of immune cells in the lungs. PM exposure nearly doubled the ALI score, indicating increased lung damage, but NMN significantly prevented the significant increase in ALI score.
In this experiment, the researchers started supplementing with NMN two weeks before PM exposure (18 weeks in total), and found that NMN could prevent severe lung damage caused by PM. This experiment demonstrates that NMN supplementation can prevent lung damage caused by PM exposure.
NMN prevents dramatic accumulation of inflammatory protein markers. PM exposure (Exp) more than doubled plasma levels of the inflammatory protein marker TNF-α. NMN almost halved PM-induced TNF-α levels.
In addition, the researchers also confirmed that NMN can reduce PM-induced lung injury by reducing inflammation. They measured plasma levels of the inflammatory protein TNF-α and found that PM exposure more than doubled TNF-α levels; NMN treatment reduced elevated TNF-α levels by half. These data demonstrate that increasing NAD+ with NMN can suppress the inflammation that leads to lung damage.
The above studies have shown that after prolonged exposure to PM, NAD+ levels drop significantly, which often triggers inflammation. Inflammation leads to tissue damage, i.e. PM exposure leads to lung damage. NMN effectively attenuated lung injury from PM exposure, possibly by reducing inflammation.