Disruption of in vitro endothelial barrier integrity by Japanese encephalitis virus‐Infected astrocytes

Abstract

Blood-brain barrier (BBB) characteristics are induced and maintained by crosstalk between brain microvascular endothelial cells and neighboring cells. Using in vitro cell models, we previously found that a bystander effect was a cause for Japanese encephalitis-associated endothelial barrier disruption. Brain astrocytes, which neighbor BBB endothelial cells, play roles in the maintenance of BBB integrity. By extending the scope of relevant studies, a potential mechanism has been shown that the activation of neighboring astrocytes could be a cause of disruption of endothelial barrier integrity during the course of Japanese encephalitis viral (JEV) infection. JEV-infected astrocytes were found to release biologically active molecules that activated ubiquitin proteasome, degraded zonula occludens-1 (ZO-1) and claudin-5, and disrupted endothelial barrier integrity in cultured brain microvascular endothelial cells. JEV infection caused astrocytes to release vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), and matrix metalloproteinases (MMP-2/MMP-9). Our data demonstrated that VEGF and IL-6 released by JEV-infected astrocytes were critical for the proteasomal degradation of ZO-1 and the accompanying disruption of endothelial barrier integrity through the activation of Janus kinase-2 (Jak2)/signal transducer and activator of transcription-3 (STAT3) signaling as well as the induction of ubiquitin-protein ligase E3 component, n-recognin-1 (Ubr 1) in endothelial cells. MMP-induced endothelial barrier disruption was accompanied by MMP-mediated proteolytic degradation of claudin-5 and ubiquitin proteasome-mediated degradation of ZO-1 via extracellular VEGF release. Collectively, these data suggest that JEV infection could activate astrocytes and cause release of VEGF, IL-6, and MMP-2/MMP-9, thereby contributing, in a concerted action, to the induction of Japanese encephalitis-associated BBB breakdown. GLIA 2015;63:1915-1932.

Fast type I interferon response protects astrocytes from flavivirus infection and virus-induced cytopathic effects

“…Previous studies have revealed that although TBEV infects astrocytes, viral infection did not affect the viability of the cells [34,35]. Similar findings have been observed with other viral infections such as WNV, JEV, and Junin virus whereas infection with Venezuelan equine encephalitis virus infection induced cell death in cultured astrocytes [31,37,39,85,86]. However, the mechanism underlying the resistance to virus-induced cell death in astrocytes is not well understood.…”

“…Both rat and human astrocytes have been shown to be infected in vitro with TBEV; however, the number of infected cells never exceeded 20 %, and the infection did not affect astrocyte viability [34,35]. Similar findings have also been observed for other neurotropic flaviviruses [36][37][38][39]. Therefore, we set out to investigate how the type I IFN system in primary mouse astrocytes contributes to cell survival and restriction of neurotropic flavivirus growth.…”

Junctional proteins of the blood-brain barrier: New insights into function and dysfunction

“…143 The polyubiquitination of claudin-5 (Lys-199), ZO-1, Ve-cadherin, JAM-A, cortactin and particularly connexins trigger junction protein proteasome-dependent degradation and serve as a mechanism of protein turnover and junction complex remodeling. 65,[144][145][146][147] So far, the ubiquitination and proteasomal degradation of occludin is the only one described as an underlying mechanism of BBB dysfunction in permanent brain ischemia.…”

Exploitation of microRNAs by Japanese Encephalitis virus in human microglial cells

“…KLF4 has been reported to regulate the endothelial barrier function in glioma cells, by suppressing the promoter activity of tight junction proteins . Further, disruption of BBB has been documented in JEV infection where the tight junction proteins are degraded . Therefore, the suppression of KLF4 during JEV infection and disruption of BBB might be co‐related.…”