Transcriptomic Analysis Suggests the M1 Polarization and Launch of Diverse Programmed Cell Death Pathways in Japanese Encephalitis Virus-Infected Macrophages

Abstract

The Japanese encephalitis virus (JEV) is a Culex mosquito-borne flavivirus and is the pathogenic agent of Japanese encephalitis, which is the most important type of viral encephalitis in the world. Macrophages are a type of pivotal innate immunocyte that serve as sentinels and respond quickly to pathogen invasions. However, some viruses like JEV can hijack macrophages as a refuge for viral replication and immune escape. Despite their crucial involvement in early JEV infection, the transcriptomic landscapes of JEV-infected macrophages are void. Here, by using an in situ JEV infection model, we investigate the transcriptomic alteration of JEV-infected peritoneal macrophages. We found that, upon JEV infection, the macrophages underwent M1 polarization and showed the drastic activation of innate immune and inflammatory pathways. Interestingly, almost all the programmed cell death (PCD) pathways were activated, especially the apoptosis, pyroptosis, and necroptosis pathways, which were verified by the immunofluorescent staining of specific markers. Further transcriptomic analysis and TUNEL staining revealed that JEV infection caused apparent DNA damage. The transcriptomic analysis also revealed that JEV infection promoted ROS and RNS generation and caused oxidative stress, which activated multiple cell death pathways. Our work uncovers the pivotal pathogenic roles of oxidative stress and multiple PCD pathways in JEV infection, providing a novel perspective on JEV–host interactions.

The Dual Regulation of Apoptosis by Flavivirus

“…Although JEV induces the classic intrinsic apoptotic pathway in N18 neuroblastoma cells, it activates both caspase-8 (part of the extrinsic pathway) and caspase-9 in a predominantly mitochondria-dependent pathway in MCF cells ( Tsao et al, 2008 ). Interestingly, in addition to apoptosis, JEV can also activate other PCD pathways, especially the pyroptosis and necroptosis pathways, which were verified by the immunofluorescent staining of specific markers ( Wang et al, 2020 ). The regulation of JEV and its protein on apoptosis is summarized in Table 3 .…”

Comparative transcriptomic analysis of THP‐1‐derived macrophages infected with Mycobacterium tuberculosis H37Rv, H37Ra and BCG

“…Classical M1 and alternative M2 polarization are the two extremes of macrophage phenotype transformation. 18 Pro‐inflammatory M1 macrophages show anti‐infection activity by promoting T helper (Th) 1 response. M2 macrophages promote Th2 responses and contribute to tissue repair, which are supposed to be anti‐inflammatory.…”

Pathogenicity and virulence of Japanese encephalitis virus: Neuroinflammation and neuronal cell damage

“…The pyroptotic macrophages released a significant amount of IL-1α in the serum, which in turn, mediated JEV neuroinvasion by breaching the BBB and induced JE in mice [ 72 ]. Furthermore, using an in situ JEV-infection model system, the transcriptomic profiling of peritoneal macrophages revealed significant enrichment of programmed cell death pathways, including necroptosis and pyroptosis verified by immunostaining of specific markers, i.e., RIPK1 and gasdermin D [ 73 ].…”