Exercise Attenuates Acute β-Adrenergic Overactivation – Induced Cardiac Fibrosis by Modulating Cytokines Abstract During acute sympathetic stress, the overactivation of β-adrenergic receptors (β-ARs) causes cardiac fibrosis by triggering inflammation and cytokine expression. It is unknown whether exercise training inhibits acute β-AR overactivation–induced cytokine expression and cardiac injury. Here, we report that running exercise inhibited cardiac fibrosis and improved cardiac function in mice treated with isoproterenol (ISO), a β-AR agonist. A cytokine antibody array revealed that running exercise prevented most of the changes in cytokine expression induced by ISO. Specifically, ISO-induced upregulation of 18 cytokines was prevented by running exercise. A Kyoto encyclopedia of genes and genomes analysis of these cytokines revealed that Hedgehog and RAP1 signaling pathways were involved in the regulation of cytokine expression by exercise. The changes in the expression of some cytokines that were prevented by exercise were verified by an enzyme-linked immunosorbent assay and real-time PCR. In conclusion, running exercise prevented the cytokine expression changes after acute β-AR overactivation and therefore attenuated cardiac fibrosis. Acute sympathetic stress is an important risk factor for the patients with cardiovascular diseases, and the present study revealed that exercise training can prevent against the upregulation of cytokines and the subsequent cardiac injury induced by acute sympathetic stress, suggesting that exercise training may be beneficial for cardiovascular patients who are in risk of acute sympathetic stress. This finding provides a theoretical basis for the application of exercise training in patients who may suffer from acute sympathetic stress.