PARP1 and chronic obstructive pulmonary disease: Changing poly(ADP-ribose) polymerase (PARP) activity and PARP-1 mRNA expression in peripheral blood mononuclear cells from never-smoking control individuals through current smokers or ex-smokers with normal lung function and patients with stabile chronic obstructive pulmonary disease (COPD) of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages I-IV to patients with a COPD exacerbation, evaluated with ordinal logistic regression analysis.