ADORA2B and chronic obstructive pulmonary disease: However, there is a substantial amount of evidence indicating that ADORA2B also has a non-protective role; for instance, smokers with COPD have elevated mRNA levels of ADORA2B as compared to non-smokers and smokers without COPD (Sun et al., 2006; Zhou et al., 2009, 2010; Karmouty-Quintana et al., 2013).