Macrophage migration inhibitory factor regulates dengue virus type 2-induced autophagy in human umbilical vein endothelial cells

Objective:To investigate the effects of macrophage migration inhibitory factor (MIF) on AMPK/ERK/mTOR autophagy signaling pathway in primary human umbilical vein endothelial cells (HUVEC) after dengue virus type 2 (DENV2) infection.Methods:The virulence of DENV2 to C6/36 cells was assessed with 50% tissue culture infectious dose (TCID 50). NS1 gene fragments in DENV2-infected HUVEC were detected by RT-PCR. Transmission electron microscopy was used to detect autophagosomes. Western blot was performed to detect the effects of DENV2 infection on the expression of autophagy-related protein LC3-Ⅱ and MIF in HUVEC. The correction of MIF with LC3-Ⅱ was then analyzed. HUVEC were pretreated with MIF inhibitor (ISO-1) or pathway inhibitor (Compound C or U0126), and then the changes in the expression of MIF, adenosine 5′-monophosphate-activated protein kinase (AMPK) pathway-related proteins and LC3-Ⅱ after DENV2 infection were detected by Western blot to reveal the correlation between MIF and AMPK autophagy pathway. Results:The TCID 50 to C6/36 cells was 10 -9.09/ml in this experiment. NS1 gene fragments were detected in DENV2-infected HUVEC. Autophagosomes or autophagolysosomes were observed in the infected HUVEC and there were differences in autophagy induced by different doses of DENV2. The mRNA levels of MIF and LC3-Ⅱ in HUVEC were positively correlated after DENV2 infection. MIF inhibitor affected AMPK, ERK and LC3-Ⅱ levels, but had no significant influence on MIF expression at protein level. Conclusions:MIF could affect autophagy through regulating the AMPK/ERK/mTOR signaling pathway in HUVEC during DENV2 infection.