Phosphocreatine attenuates isoproterenol-induced cardiac fibrosis via activation of the Nrf2/ARE antioxidant pathway and preservation of endothelial integrity

BACKGROUND Phosphocreatine (PCr), a high-energy phosphate donor with established cytoprotective and antioxidative properties, is known to support endothelial function. However, its role in the regulation of cardiac fibrogenesis remains poorly defined. This study aimed to determine whether PCr attenuates isoproterenol (ISO)-induced cardiac fibrosis and to examine the potential involvement of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. METHODS A murine model of cardiac fibrosis was established by subcutaneous administration of ISO. Mice were treated with PCr, and cardiac tissues were analyzed for histopathological alterations, collagen deposition, and markers of oxidative stress, endothelial integrity, and fibroblast activation. The expression and nuclear translocation of Nrf2 and its downstream antioxidant enzymes, including heme oxygenase-1 (HO-1) and superoxide dismutase (SOD), were evaluated by immunoblotting and immunofluorescence. Serum creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) levels were measured to assess myocardial injury. RESULTS ISO administration induced marked myocardial fibrosis characterized by excessive collagen accumulation, oxidative damage, myofibroblast activation, and endothelial disruption. PCr treatment significantly preserved myocardial architecture and reduced interstitial collagen deposition. PCr treatment is associated with enhanced Nrf2 nuclear translocation and upregulation of HO-1 and SOD, while reducing lipid peroxidation, as indicated by decreased malondialdehyde (MDA) levels. Associated with downregulation of α-smooth muscle actin (α-SMA) and collagen type I, these findings highlight the therapeutic potential of PCr in preventing cardiac fibrosis and adverse myocardial remodeling. PCr also maintained endothelial integrity (increased CD31 expression) and reduced serum CK-MB and LDH levels, indicating attenuation of ISO-induced cardiac injury. CONCLUSIONS PCr confers robust antifibrotic and antioxidant protection and is associated with activation of the Nrf2/ARE signaling pathway, suppression of fibroblast activation, and preservation of endothelial function. These findings highlight the therapeutic potential of PCr in preventing cardiac fibrosis and adverse myocardial remodeling.