PDE8A is a high-affinity, cAMP-specific phosphodiesterase that hydrolyzes the second messenger cAMP, a key regulator of physiological processes 1. The enzyme is expressed widely across tissues with highest levels in testis, ovary, small intestine, and colon, and functions in maintaining basal cAMP levels and regulating germ cell development 1. PDE8A exhibits high substrate specificity with a Km of 55 nM for cAMP and is IBMX-insensitive, distinguishing it from PDE4 and PDE7 1. Mechanistically, PDE8A regulates critical signaling pathways through cAMP degradation. Inhibition of PDE8A-mediated cAMP hydrolysis enhances PKA activation, thereby limiting caspase-11 inflammasome activation and pyroptosis in sepsis 2. In cardiac tissue, AKAP12-mediated upregulation of PDE8A reduces cAMP levels and impairs β2-adrenergic receptor signaling, contributing to cardiac dysfunction 3. In atrial fibrillation, upregulated PDE8B directly binds Cav1.2α1C, reducing L-type calcium current through decreased phosphorylation 4. Clinically, PDE8A alterations associate with multiple disease states. Elevated circular PDE8A in pancreatic cancer exosomes promotes invasion via the miR-338/MACC1/MET pathway and correlates with poor prognosis 5. Genetic variants in PDE8A associate with facial morphogenesis in genome-wide studies 6. PDE8 inhibitors show therapeutic potential in asthma and COPD through combined PDE4B/PDE8A/TRPA1 blockade 7.