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Fowl Adenovirus Serotype 4 Induces Hepatic Steatosis via Activation of Liver X Receptor-α.

Abstract：

:Fowl adenovirus serotype 4 (FAdV-4) is a hepatotropic virus that causes severe hepatic damage characterized by basophilic intranuclear inclusion bodies, vacuolar degeneration, and multifocal necrosis in hepatocytes. Many aspects of FAdV-4 infection and pathogenesis, however, remain unknown. Here, we found that FAdV-4-induced hepatic injury is accompanied by the accumulation of oil droplets (triglycerides) in the cytoplasm of hepatocytes, a typical indicator of steatosis, in FAdV-4-infected chickens. Significant upregulation of adipose synthesis-related genes, such as LXR-α, PPAR-γ, and SREBP-1c, and significant downregulation of low-density lipoprotein secretion-related genes and lipid oxidation- and lipid decomposition-related genes were observed in the infected chickens. FAdV-4 infection in cultured leghorn male hepatoma (LMH) cells caused similar signs of steatosis, with alterations in various lipogenesis-related genes. We extermined the effect of LXR-α activation on FAdV-4-induced steatosis and found that treatment with an LXR-α antagonist (SR9243) and RNA interference (si-LXR-α) decreased the number of oil droplets and the accumulation of lipogenic genes, but treatment with an LXR-α agonist (T0901317) increased the number of oil droplets and the accumulation of lipogenic genes in the cells. Additionally, SR9243 treatment or si-LXR-α transfection led to significant reductions in viral DNA level, protein expression, and virus production, whereas T0901317 treatment caused significant increases in viral DNA level, protein expression, and virus production. However, inhibition of SREBP-1c activity had no significant effect on virus production. Collectively, these results indicated that FAdV-4-induced steatosis involves activation of the LXR-α signaling pathway, which might be a molecular mechanism underlying the hepatic injury associated with FAdV-4 infection.IMPORTANCE FAdV-4 is an important hepatotropic adenovirus in chicken, but the underlying mechanism of FAdV-4-induced hepatic injury remains unclear. We report here that infection with FAdV-4 induced the accumulation of oil droplets (triglycerides) in the cytoplasm of hepatocytes, a typical indicator of steatosis, in the livers of chickens. FAdV-4-induced steatosis might be caused by a disrupted balance of fat metabolism, as evidenced by differential regulation of various lipase genes. The significant upregulation of LXR-α prompted us to investigate the interplay between LXR-α activation and FAdV-4-induced steatosis. Treatment with an agonist, an antagonist, or RNA interference targeting LXR-α in cultured LMH cells indicated that FAdV-4-induced steatosis was dependent upon LXR-α activation, which contributed to virus replication. These results provide important mechanistic insights, revealing that FAdV-4 induces hepatic steatosis by activating the LXR-α signaling pathway and highlighting the therapeutic potential of strategies targeting the LXR-α pathway for the treatment of FAdV-4 infection.

journal_name

J Virol

journal_title

Journal of virology

authors

Yuan F,Hou L,Wei L,Quan R,Wang J,Liu H,Liu J

doi

10.1128/JVI.01938-20

subject

Has Abstract

pub_date

2020-12-23 00:00:00

eissn

0022-538X

issn

1098-5514

pii

JVI.01938-20

pub_type

杂志文章

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Fowl Adenovirus Serotype 4 Induces Hepatic Steatosis via Activation of Liver X Receptor-α.