Abstract
Cigarette smoke (CS) is a main risk factor for chronic obstructive pulmonary disease (COPD). Oxidative stress induced by CS causes DNA and lung damage. Oxidant/antioxidant imbalance occurs in the distal air spaces of smokers and in patients with COPD. We studied the effect of oxidative stress generated by CS both in vivo and in vitro on murine primary alveolar type II (ATII) cells isolated from nuclear erythroid 2-related factor-2 (Nrf2)−/− mice. We determined human primary ATII cell injury by CS in vitro and analyzed ATII cells isolated from smoker and non-smoker lung donors ex vivo. We also studied whether trolox (water-soluble derivative of vitamin E) could protect murine and human ATII cells against CS-induced DNA damage and/or decrease injury. We analyzed oxidative stress by 4-hydroxynonenal expression, reactive oxygen species (ROS) generation by Amplex Red Hydrogen Peroxide Assay, Nrf2, heme oxygenase 1, p53 and P53-binding protein 1 (53BP1) expression by immonoblotting, Nrf2 nuclear translocation, Nrf2 and p53 DNA-binding activities, apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and cytokine production by ELISA. We found that ATII cells isolated from Nrf2−/− mice are more susceptible to CS-induced oxidative DNA damage mediated by p53/53BP1 both in vivo and in vitro compared with wild-type mice. Therefore, Nrf2 activation is a key factor to protect ATII cells against injury by CS. Moreover, trolox abolished human ATII cell injury and decreased DNA damage induced by CS in vitro. Furthermore, we found higher inflammation and p53 mRNA expression by RT-PCR in ATII cells isolated from smoker lung donors in comparison with non-smokers ex vivo. Our results indicate that the Nrf2 and p53 cross talk in ATII cells affect the susceptibility of these cells to injury by CS. Trolox can protect against oxidative stress, genotoxicity and inflammation induced by CS through ROS scavenging mechanism, and serve as a potential antioxidant prevention strategy against oxidative injury of ATII cells in CS-related lung diseases.
Highlights
There is no effective therapy to prevent the progression of this disease.[2]
We studied the effect of oxidative stress generated by Cigarette smoke (CS) both in vivo and in vitro on murine primary alveolar type II (ATII) cells isolated from nuclear erythroid 2-related factor-2 (Nrf2) À / À mice
We found significantly higher expressions of Nrf[2], heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), glutamyl-cysteine ligase catalytic subunit (GCLc) and 4-HNE induced by CS in ATII cells obtained from Nrf[2] þ / þ mice and lower levels of these proteins after trolox administration followed by CS
Summary
There is no effective therapy to prevent the progression of this disease.[2]. Oxidative stress induced by CS is the main cause of DNA damage[3] and defects in DNA damage recognition and repair mechanisms are associated with cancer predisposition.[4]. P53-binding protein 1 (53BP1) is a major determinant of DNA damage[5] and is a mediator that relays signals from DNA damage sensors and activates various effectors for the DNA repair.[6] There is an urgent need to develop new strategies to prevent oxidative lung injury induced by CS. The Nrf2-dependent genes have the ability to upregulate antioxidant defenses and decrease lung inflammation and alveolar cell apoptosis.[11] Pulmonary Nrf[2] effector genes bearing AREs include, for example, heme oxygenase 1. Antioxidant compounds could have a key role in the protection against CS-induced DNA damage and/or decreasing lung injury.[14] Vitamin E is known to be one of the most potent lipophilic chain-breaking antioxidants in biological membranes, where it scavenges reactive oxygen species (ROS), inhibits the initiation and chain propagation of
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