Adenosine Signaling as a Central Integrative Network in Cellular Stress Responses and a Therapeutically Actionable Target in Human Disease

Adenosine has emerged as a central metabolic signal linking cellular stress to systemic physiological adaptation. Under conditions such as hypoxia, ischemia, inflammation, and tissue injury, extracellular adenosine triphosphate (eATP) released from stressed cells is sequentially metabolized by the ectonucleotidases CD39 and CD73, generating adenosine that accumulates in the extracellular microenvironment. This stress-responsive nucleoside activates four G-protein-coupled receptors (A1, A2A, A2B, and A3), triggering intracellular signaling networks including the cyclic adenosine monophosphate–protein kinase A (cAMP–PKA), mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase–protein kinase B (PI3K–Akt), and hypoxia-inducible factor-1 alpha (HIF-1α) pathways. Through these integrated mechanisms, adenosine orchestrates diverse physiological processes such as vascular regulation, metabolic adaptation, immune modulation, and cellular survival. In the cardiovascular system, adenosine promotes coronary vasodilation and ischemic preconditioning, limiting reperfusion injury. In pulmonary tissues, it mediates acute anti-inflammatory responses but may also drive chronic fibrotic remodeling. Within the central nervous system, adenosine functions as a neuromodulator regulating neuronal excitability, sleep–wake homeostasis, and neuroprotection. In the tumor microenvironment, hypoxia-driven adenosine accumulation suppresses cytotoxic T cell and natural killer activity, facilitating immune evasion and tumor progression. Collectively, adenosine signaling represents a central integrative network that links metabolic stress sensing to coordinated cellular adaptation while simultaneously emerging as a clinically actionable therapeutic target across cardiovascular, inflammatory, neurological, and oncological diseases.