To further investigate whether NMN directly protects against AEC senescence, Wei and colleagues looked at the effect of the NAD+ precursor on AECs that had been induced into senescence in two different ways. NMN treatment substantially reduced the number of lung cells that entered replicative senescence — a state in which cells can no longer proliferate after undergoing too many divisions — when cultured in laboratory dishes.
Wei and colleagues also stressed the lung cells by treating them with an antibiotic called bleomycin, known to induce lung cell senescence. They found that NMN treatment significantly reduced the number of senescent cells following the bleomycin antibiotic stress. These findings show that NMN protects against senescence induced both by excessive replication and stress.