The Role of TNF-α in Ischemic Stroke

Ischemic stroke accounts for approximately 80-85% of all stroke cases and triggers a complex cascade of metabolic, immunological, and neurodegenerative processes. Among the key mediators involved, TNF-α occupies a central position due to its distinctly dual and phase-dependent actions. Importantly, the biological effects of TNF-α are not static but evolve dynamically over time following ischemic insult. During the acute phase of ischemia, a rapid increase in TNF-α levels, primarily originating from activated microglia, leads to the predominant activation of the TNFR1 receptor. This results in enhanced apoptosis and necroptosis, disruption of the blood-brain barrier, increased leukocyte recruitment, and the progression of secondary neuronal injury. In later phases, the role of TNF-α shifts, with signaling through TNFR2 becoming more prominent, thereby supporting reparative mechanisms, including neurogenesis, angiogenesis, and synaptic remodeling. The dual nature of TNF-α means that both its excessive activation and complete inhibition may produce detrimental effects. Notably, the therapeutic relevance of TNF-α critically depends on the timing of intervention relative to stroke onset. A comprehensive analysis of current evidence underscores the central, temporally and contextually dependent role of TNF-α in the pathophysiology of ischemic stroke. It also indicates that future therapeutic strategies should aim to selectively suppress the harmful TNFR1-mediated signaling while preserving or enhancing TNFR2-dependent neuroprotective pathways. Such time-sensitive and receptor-selective modulation holds promise for limiting acute ischemic injury and promoting endogenous repair processes, representing a compelling direction for the development of next-generation neuroprotective therapies.