Inhibition of complement C3 signaling ameliorates locomotor and visual dysfunction in autoimmune inflammatory diseases.

Neuromyelitis optica (NMO) is an autoimmune inflammatory disease of the central nervous system (CNS) characterized by transverse myelitis and optic neuritis. The pathogenic serum IgG antibody against the aquaporin-4 (AQP4) on astrocytes triggers the activation of the complement cascade, causing astrocyte injury, followed by oligodendrocyte injury, demyelination, and neuronal loss. Complement C3 is positioned as a central player that relays upstream initiation signals to activate downstream effectors, potentially stimulating and amplifying host immune and inflammatory responses. However, whether targeting the inhibition of C3 signaling could ameliorate tissue injury, locomotor defects, and visual impairments in NMO remains to be investigated. In this study, using the targeted C3 inhibitor CR2-Crry led to a significant decrease in complement deposition and demyelination in both slice cultures and focal intracerebral injection models. Moreover, the treatment downregulated the expression of inflammatory cytokines and improved motor dysfunction in a systemic NMO mouse model. Similarly, employing serotype 2/9 adeno-associated virus (AAV2/9) to induce permanent expression of CR2-Crry resulted in a reduction in visual dysfunction by attenuating NMO-like lesions. Our findings reveal the therapeutic value of inhibiting the complement C3 signaling pathway in NMO.