Apigenin Alleviates Oxidative Stress-Induced Cellular Senescence via Modulation of the SIRT1-NAD+-CD38 Axis

Oxidative stress-induced cellular senescence is now regarded as an important driving mechanism in chronic lung diseases-particularly chronic obstructive pulmonary disease (COPD). 4',5,7-trihydroxyflavone (Apigenin) is a natural flavonoid product abundantly present in fruits, vegetables, and Chinese medicinal herbs. It has been known that apigenin has anti-oxidant, anti-inflammatory and liver-protecting effects. The efficacy of apigenin for lung aging, however, has not been reported. In this study, we selected the hydrogen peroxide (H2O2)- or doxorubicin (DOXO)-induced senescence model in WI-38 human embryonic lung fibroblast cells to determine the potential anti-aging effects of apigenin in vitro and associated molecular mechanisms. We found that apigenin reduced senescence-associated beta-galactosidase (SA-beta-gal) activity and promoted cell growth, concomitant with a decrease in levels of Acetyl (ac)-p53, p21(Waf1/Cip1), and p16(Ink4a) and an increase in phospho (p)-Rb. Apigenin also increased the activation ratio of silent information regulator 1 (SIRT1), nicotinamide adenine dinucleotide (NAD(+)), and NAD(+)/NADH and inhibited cluster of differentiation 38 (CD38) activity in a concentration-dependent manner. SIRT1 inhibition by SIRT1 siRNA abolished the anti-aging effect of apigenin. In addition, CD38 inhibition by CD38 siRNA or apigenin increased the SIRT1 level and reduced H2O2-induced senescence. Our findings suggest that apigenin is a promising phytochemical for reducing the impact of senescent cells in age-related lung diseases such as COPD.