cAMP-specific 3',5'-cyclic phosphodiesterase 4 family (PDE4A, PDE4B, PDE4C, PDE4D) (PDE4)

The Phosphodiesterase 4 (PDE4) family consists of four subtypes (PDE4A, PDE4B, PDE4C, and PDE4D) that specifically catalyze the hydrolysis of cyclic adenosine monophosphate (cAMP), a vital intracellular second messenger [1, 4, 16]. These enzymes are widely distributed in immune cells, the central nervous system, and airway smooth muscle, where they play a central role in modulating inflammatory responses and cognitive functions [6, 13, 15]. Inhibition of PDE4 leads to an accumulation of intracellular cAMP, which subsequently activates protein kinase A (PKA) and suppresses the production of pro-inflammatory mediators like TNF-alpha, IL-17, and IL-23 [5, 16, 17]. Consequently, PDE4 inhibitors have been successfully developed for the treatment of chronic inflammatory conditions such as chronic obstructive pulmonary disease (COPD), psoriasis, and atopic dermatitis [11, 15, 18]. Despite their efficacy, the use of systemic PDE4 inhibitors is frequently limited by adverse effects, particularly nausea and emesis, which are primarily attributed to the inhibition of the PDE4D subtype in the area postrema of the brain [8, 12, 15]. To overcome these challenges, current research is directed toward developing subtype-selective inhibitors, such as PDE4B-selective agents for inflammation or PDE4D-selective agents for cognitive enhancement, as well as inhaled formulations to minimize systemic exposure [7, 10, 13]. Additionally, PDE4 has emerged as a potential target in various cancers and neurodegenerative diseases, reflecting its broad physiological impact [13, 14].

Other names

PDE4 familyPhosphodiesterase 4cAMP-specific 3',5'-cyclic phosphodiesterase 4

Inhibition of PDE4 enzymes prevents the hydrolysis of cyclic adenosine monophosphate (cAMP) to 5'-AMP, leading to increased intracellular cAMP levels [1, 9]. This activates protein kinase A (PKA) and Epac, resulting in the suppression of pro-inflammatory cytokines (e.g., TNF-alpha, IL-17, IL-23) and the promotion of anti-inflammatory mediators (e.g., IL-10), while also inducing smooth muscle relaxation in the airways [11, 16, 17].