Complement C3a receptor antagonist alleviates tau pathology and ameliorates cognitive deficits in P301S mice

Human tauopathies, including Alzheimer's disease (AD), are a major class of neurodegenerative diseases characterized by intracellular deposition of pathological hyperphosphorylated forms of Tau protein. Complement system is composed of many proteins, which form a complex regulatory network to modulate the immune activity in the brain. Emerging studies have demonstrated a critical role of complement C3a receptor (C3aR) in the development of tauopathy and AD. The underlying mechanisms by which C3aR activation mediates tau hyperphosphorylation in tauopathies, however, remains largely unknown. Here, we observed that the expression of C3aR is upregulated in the brains of P301S mice - a mouse model of tauopathy and AD. Pharmacologic blockade of C3aR ameliorates synaptic integrity and reduced tau hyperphosphorylation in P301S mice. Besides, the administration of C3aR antagonist (C3aRA: SB 290157) improved spatial memory as tested in the Morris water maze. Moreover, C3a receptor antagonist inhibited tau hyperphosphorylation by regulating p35/CDK5 signaling. In summary, results suggest that the C3aR plays an essential role in the accumulation of hyperphosphorylated Tau and behavioral deficits in P301S mice. C3aR could be a feasible therapeutic target for the treatment of tauopathy disorders, including AD.