GRK2 and heart failure: Thus, compounds with hydrazone cores express inhibitory effects against numerous enzymes, such as cyclooxygenase (COX-1 and COX-2) [20,34], acetyl- and butyrylcholinesterase (AChE and BuChE) [35], monoamine oxidase A (MAO A) [36], as well as G-Protein-Coupled Receptor Kinase 2 (GRK2) involved in heart failure [37].