Naringenin attenuates Mandarin fish ranavirus (MRV)-induced hyperinflammation through the inhibition of MAPK and NF-κB signaling pathways.

Mandarin fish ranavirus (MRV) has caused substantial economic losses in the culture of mandarin fish (Siniperca chuatsi) in China. The pathogenesis of MRV infection is largely attributed to the systemic hyperinflammation. However, the roles of specific signaling pathways and their activation in driving the excessive triggering of pro-inflammatory mediators during MRV infection remain inadequately understood. Naringenin, a dihydroflavonoid predominantly found in citrus fruits and tomatoes, demonstrates high intestinal absorption efficiency with multiple bioactivities, including antioxidant, antiviral, and anti-inflammatory activities. In the present study, the up-regulation of inflammation-associated genes (il-1β, il-8, tnf-α and inos) was confirmed in the MRV-infected mandarin fish spleen, accompanied by severe histological lesions. Moreover, the activation of MAPK and NF-κB pathways was further verified by the up-regulation of myd88, traf6, erk, p38, jnk, and nf-κb p65, along with the nuclear translocation of NF-κB p65. Then, we further discovered that the oral administration of naringenin inhibited the activation of MAPK and NF-κB signaling pathways and restricted MRV replication, correlating with the amelioration of spleen lesions. Ultimately, Naringenin treatment significantly increased the survival of MRV-infected fish from 20 % to 60 %. In conclusion, these findings clarify the mechanisms of MRV-induced hyperinflammation and demonstrate that naringenin mitigates this pathology by suppressing MAPK and NF-κB signaling pathways and viral replication. Our results provide a foundation for therapeutic strategies against MRV infection in aquaculture.