Tyrosine kinase Fyn promotes apoptosis after intracerebral hemorrhage in rats by activating Drp1 signaling.

Tyrosine kinase Fyn is a member of the Src kinase family, which is involved in neuroinflammation, apoptosis, and oxidative stress. Its role in intracerebral hemorrhage (ICH) is not fully understood. In this study, we found that Fyn was significantly elevated in human brain tissue after ICH. Accordingly, we investigated the role of Fyn in a rat ICH model, which was constructed by injecting blood into the right basal ganglia. In this model, Fyn expression was significantly upregulated in brain tissue adjacent to the hematoma. SiRNA-induced Fyn knockdown was neuroprotective for secondary cerebral damage, as demonstrated by reduced brain edema, suppression of the modified neurological severity score, and mitigation of blood-brain barrier permeability and neuronal damage. Fyn downregulation reduced apoptosis following ICH, as indicated by downregulation of apoptosis-related proteins AIF, Cyt.c, caspase 3, and Bax; upregulation of anti-apoptosis-related protein Bcl-2; and decreased tunnel staining. Mdivi-1, a Drp1 inhibitor, reversed Fyn overexpression induced pro-apoptosis. However, Fyn did not significantly affect inflammation-related proteins NF-κB, TNF-α, caspase 1, MPO, IL-1β, or IL-18 after ICH. Fyn activated Drp1 signaling by phosphorylating Drp1 at serine 616, which increased apoptosis after ICH in rats. This study clarifies the relationship between Fyn, apoptosis, and inflammation following ICH and provides a new strategy for exploring the prevention and treatment of ICH. KEY MESSAGES: ICH induced an increase in Fyn expression in human and rat cerebral tissues. Knockdown of Fyn prevented cerebral damage following ICH. Inhibition of Fyn had no significant effects on inflammatory responses. However, the downregulation of Fyn exerted neuroprotective effects on apoptosis. Fyn perturbed ICH-induced cell apoptosis by interacting with and phosphorylating (Ser616) Drp1 in a rat ICH model.