Blood-brain barrier permeability and brain immunity in yellow catfish (Pelteobagrus fulvidraco) responding to Edwardsiella ictaluri infection

Abstract

The blood-brain barrier (BBB) plays a crucial role in maintaining the homeostasis of the central nervous system (CNS) by preventing the entry of harmful substances into the brain parenchyma. Although bacterial infections of the CNS are typically linked to BBB disruption, there is a notable paucity of knowledge concerning alterations in BBB permeability and the CNS immune response in teleosts during such infections. This study investigates these phenomena by administering an intraperitoneal injection of Edwardsiella ictaluri to yellow catfish (Pelteobagrus fulvidraco), followed by an evaluation of BBB permeability and the CNS immune response. E. ictaluri has the capability to penetrate the BBB and predominantly colonizes the mesencephalon region. Furthermore, there was a significant elevation in reactive oxygen species (ROS) activity within both the telencephalon and mesencephalon, accompanied by a reduction in mRNA expression levels of tight junction (TJ) proteins, which coincided with increased BBB permeability. Additionally, pathological alterations in brain tissue structure were observed following E. ictaluri infection.The immune response of the CNS was triggered by E. ictaluri infection, which primarily affected the functionality of the neuropeptide signaling pathway and chemokine activity. Notably, E. ictaluri infection resulted in a significant increase in the amount of B cells in the mesencephalon and elevated antibody levels. According to these findings, E. ictaluri enhanced the permeability of the BBB by rupturing the TJs between endothelial cells. This disruption induced inflammation and resulted in an increased presence of immunoglobulins and B cells within the CNS.