It has been known that HDAC is a key molecule in the repression of production of pro-inflammatory cytokines in AMs, and a decrease in HDAC is associated with increased inflammation in COPD and an increase in phosphorylated p38 MAPKs, playing a pivotal role in generating inflammatory cytokines in COPD smokers [142]. Here, HDAC9 is linked to chronic obstructive pulmonary disease.