P21-PARP-1 Pathway Is Involved in Cigarette Smoke-Induced Lung DNA Damage and Cellular Senescence

Hongwei Yao,Irfan Rahman,Isaac K Sundar,Vera Gorbunova

doi:10.1371/journal.pone.0080007

Hongwei Yao, Irfan Rahman + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0080007

Copy DOI

Abstract

Persistent DNA damage triggers cellular senescence, which may play an important role in the pathogenesis of cigarette smoke (CS)-induced lung diseases. Both p21CDKN1A (p21) and poly(ADP-ribose) polymerase-1 (PARP-1) are involved in DNA damage and repair. However, the role of p21-PARP-1 axis in regulating CS-induced lung DNA damage and cellular senescence remains unknown. We hypothesized that CS causes DNA damage and cellular senescence through a p21-PARP-1 axis. To test this hypothesis, we determined the levels of γH2AX (a marker for DNA double-strand breaks) as well as non-homologous end joining proteins (Ku70 and Ku80) in lungs of mice exposed to CS. We found that the level of γH2AX was increased, whereas the level of Ku70 was reduced in lungs of CS-exposed mice. Furthermore, p21 deletion reduced the level of γH2AX, but augmented the levels of Ku70, Ku80, and PAR in lungs by CS. Administration of PARP-1 inhibitor 3-aminobenzamide increased CS-induced DNA damage, but lowered the levels of Ku70 and Ku80, in lungs of p21 knockout mice. Moreover, 3-aminobenzamide increased senescence-associated β-galactosidase activity, but decreased the expression of proliferating cell nuclear antigen in mouse lungs in response to CS. Interestingly, 3-aminobenzamide treatment had no effect on neutrophil influx into bronchoalveolar lavage fluid by CS. These results demonstrate that the p21-PARP-1 pathway is involved in CS-induced DNA damage and cellular senescence.

Highlights

Cigarette smoke (CS) is an important risk factor in chronic inflammatory pulmonary diseases including chronic obstructive pulmonary disease (COPD), due to increased inflammation, oxidative stress, apoptosis/proliferation, and premature senescence/aging [1,2]
An early cellular response to double-strand breaks (DSB) is the rapid phosphorylation of H2AX at Ser139, which is a sensitive molecular marker for DNA damage [23,24]
To determine whether CS causes DNA damage, we performed the immunoblotting for cH2AX in mouse lungs

Summary

Introduction

Cigarette smoke (CS) is an important risk factor in chronic inflammatory pulmonary diseases including chronic obstructive pulmonary disease (COPD), due to increased inflammation, oxidative stress, apoptosis/proliferation, and premature senescence/aging [1,2]. We have shown that CS exposure causes premature senescence in lung cells, leading to airspace enlargement and lung function decline [3]. Increased DNA damage is observed in lungs of patients with COPD [7,8,9,10,11,12]. The molecular mechanism of CSinduced DNA damage and subsequent lung cellular senescence is unknown. Accumulating evidence has shown that p21CDKN1A (p21), the first identified inhibitor of cyclin/cyclin-dependent kinase complex, participates in the DNA damage response [13]. Poly(ADP-ribose) polymerase 1 (PARP-1), an NAD+-dependent ADP-ribosyltransferase 1, is known as a damage sensor, which binds to damaged DNA and thereby promotes the cellular response to DNA single-strand breaks and double-strand breaks (DSB) [17,18]. PARP-1-mediated PARylation promotes non-homologous end joining (NHEJ) through recruitment or retention of repair factors at DSB sites [19]

Methods

Results

Conclusion