PDE4A and chronic obstructive pulmonary disease: Targeted inhibiting PDE4 has been demonstrated as an effective therapeutic strategy for treating diseases such as asthma, chronic obstructive pulmonary disease (COPD), psoriasis, atopic dermatitis (AD), inflammatory bowel disease (IBD), rheumatoid arthritis (RA), lupus, neuropathy, depression, memory enhancement, and emesis (Schick and Schlegel, 2022).