PRKN and chronic obstructive pulmonary disease: The protein levels of PINK1 were decreased, while that of PARK2 and SQSTM1/p62 and ratios of LC3b II/I were increased in both smokers and COPD patients compared to non-smokers, which may indicate an enhanced mitophagy (p < 0.05, p < 0.001, p < 0.05, p < 0.001, p < 0.05, p < 0.001 and p < 0.05 respectively, Fig. 2J–M).