Heart–Brain Axis in Viral Myocarditis: Shared Cytokine Pathways, Blood–Brain Barrier Crosstalk, and Neuroinflammatory Consequences

The heart–brain axis is a bidirectional communication network composed of neural, humoral, and immune pathways that sustain cardiovascular and brain homeostasis. There is mounting evidence that viral myocarditis—a prototype of inflammatory heart disease—acts beyond the myocardium, triggering systemic immune cascades that lead to central nervous system (CNS) involvement. This involvement creates an inflammatory continuum in which cardiac damage and neuroinflammation reinforce each other via common cytokine and molecular mediators. Central mediators in this axis are the proinflammatory cytokines IL-1β, IL-6, tumor necrosis factor (TNF)-α, IL-17, IL-23, and IL-33. These cytokines are released by infected cardiomyocytes and immune cells during myocarditis, inducing endothelial cell (EC) activation, and causing blood–brain barrier (BBB) disruption. Simultaneously, TLR/NF-κB signaling and the stability of endothelial junctions are modulated by regulatory microRNAs such as miR-155 and miR-146a/b, which respectively enhance or attenuate inflammatory signals. Disruption of the BBB allows cytokines and immune cells to enter the brain parenchyma, where they activate microglia and astrocytes through NF-κB-dependent pathways. The resultant neuroinflammation disrupts autonomic equilibrium and leads to sympathetic overdrive, arrhythmogenesis, and overall worsening of cardiac injury, thus forming a self-perpetuating inflammatory cycle between the heart and the brain. Selective modulation of cytokines (anti-IL-1β, IL-6 receptor antagonists, and TNF-α modulators), blockade of the NLRP3 inflammasome, and miRNA therapy (anti-miR-155 and miR-146a mimics) are potential approaches for interrupting the heart–brain inflammatory circuit. In addition, neurotrophic therapies preserving BBB integrity may reduce secondary neuronal damage. Therefore, a future precision cardio-neuroprotective paradigm will rely on the integration of anti-inflammatory, molecular, and neurovascular strategies aimed at limiting systemic cytokine propagation and restoring bidirectional homeostasis through the heart–brain axis.