In toxicology, PDEs are significant due to their role in modulating cellular responses to toxicants. Alterations in PDE activity can lead to disrupted cellular signaling, resulting in toxicological outcomes such as Cellular Damage or cell death. Moreover, some toxicants can directly inhibit or activate specific PDE isoforms, leading to altered cyclic nucleotide levels and subsequent physiological effects. Understanding these interactions is crucial for evaluating the Toxic Effects of chemicals and drugs.