Ginsenoside Rb1 alleviates isoproterenol- and transverse aortic constriction-induced cardiac fibrosis by suppressing monocyte recruitment via targeting Raf1.

BACKGROUND: A major pathological event in heart failure (HF) is cardiac fibrosis induced by pressure overload, and infiltration of monocytes is essential in this scenario. Nevertheless, there are no targeted therapies. Ginsenoside Rb1 (Rb1), a major active component of Panax ginseng, has been proven to have cardioprotective ability, although the exact molecular target is not yet clearly understood. METHODS: Mouse models of cardiac fibrosis were induced by subcutaneous isoproterenol (ISO) injection or transverse aortic constriction (TAC). Echocardiography, histology, and molecular biology techniques were used to evaluate the effects of Rb1 on cardiac function, hypertrophy, fibrosis, and macrophage infiltration. The direct target of Rb1 was identified through a combined methodology that includes phosphoproteomics, thermal proteome profiling, cellular thermal shift assay, and surface plasmon resonance. The specific role of monocytic Raf1 was further validated using a pharmacological inhibitor (GW5074) and monocyte/macrophage-specific Raf1 knockdown in vivo. RESULTS: Rb1 was effective in the prevention of cardiac dysfunction, hypertrophy, and fibrosis in both ISO- and TAC-induced mouse models. These effects were mediated through the inhibition of monocyte recruitment by directly targeting Raf1. Mechanistically, Rb1 interacts with Raf1, inhibits its kinase activity, and consequently suppresses the Raf1-MEK-Erk-Creb signaling, which resulted in decreased CD11b/CD18 expression and inhibited migration of monocytes. Importantly, the anti-fibrotic effects of Rb1 were recapitulated by the Raf1 inhibitor GW5074 and in vivo monocyte/macrophage-specific Raf1 knockdown. CONCLUSION: Our research not only unveils a new immunomodulatory effect of Ginsenoside Rb1 that targets monocytic Raf1 as a key mediator but also notes Raf1 inhibition as a promising therapeutic strategy of HF.