VEGFR-3 deficiency in astrocytes exacerbates Japanese encephalitis virus-induced neuroinflammation in mouse brains.

Japanese encephalitis virus (JEV), a highly neurotropic flavivirus, preferentially targets neurons, where it replicates efficiently and induces extensive neuroinflammation and neural injury within the central nervous system (CNS), resulting in severe neurological deficits and high mortality. Vascular endothelial growth factor receptor 3 (VEGFR-3), a receptor tyrosine kinase encoded by FLT4, plays an essential role in vascular system regulation, especially in the development and maintenance of the lymphatic system. While previous studies have shown that macrophage-expressed VEGFR-3 suppresses bacterial sepsis and neuroinflammatory responses, its function in astrocytes during viral encephalitis remains unclear. To elucidate the astrocytic role of VEGFR-3 in JEV pathogenesis, mice carrying a conditional deletion of the VEGFR-3 ligand-binding domain specifically in astrocytes were generated. Astrocyte-specific VEGFR-3 deficiency led to increased brain viral load, amplified transcription of proinflammatory genes, and reduced survival following JEV challenge. JEV-infected brains with astrocytic VEGFR-3 deficiency exhibited heightened expression of multiple inflammatory cytokines and chemokines. Complementary in vitro experiments further confirmed that chemical inhibition of VEGFR-3 intracellular kinase activity enhanced inflammatory cytokine gene expression in JEV-infected astrocytes. Collectively, these findings identify astrocytic VEGFR-3 as a critical negative regulator of virus-triggered neuroinflammation, implicating it as a protective modulator of host responses during JEV infection.