RESUMO
ObjectiveTo investigate whether cytotoxic T lymphocyte （CTL）－derived exosomes can downregulate HBx expression and inhibit hepatic stellate cell （HSC） activation. MethodsThe supernatants of HepG2， HepGA14， and CTL cells were collected to extract exosomes， which were referred to as NC－exo， HBV－exo， and CTL－exo， respectively）. Transmission electron microscopy was used to observe their morphology， and Western Blot was used to measure the expression of the markers of exosomes CD63 and TSG101. NC－exo， HBV－exo， and CTL－exo labeled by BODIPY dye were mixed with HBV－exo at different ratios and were then co－cultured with HSC LX－2 （HSC－LX2）. A fluorescence microscope was used to observe whether exosomes could enter LX－2 cells， and an fluorescence microscope was used to observe cell morphological changes； quantitative real－time PCR （qPCR） was used to measure the expression of the activated biomarkers such as transforming growth factor－β1 （TGF－β1）， ɑ－smooth muscle actin （ɑ－SMA）， and collagen type I （Collagen I） in LX－2 cells. CTL－exo was added to the HepGA14 culture system； then qPCR was used to measure the mRNA expression level of HBV DNA， cccDNA， and HBx in exosomes in HepGA14 cells， and Western Blot was used to measure the protein expression level of HBx in exosomes. The t-test was used for comparison of normally distributed continuous data between two groups； a one-way analysis of variance was used for comparison between multiple groups， and the least significant difference t-test was used for further comparison between two groups. ResultsThe exosomes were all microcysts with a double－layer membrane structure and were circular or elliptical in shape， with the expression of the signature proteins CD63 and TSG101， and the vesicles had a diameter of 50－100 nm. The fluorescence microscope showed that exosomes could enter LX－2 cells， and HSC were enlarged with extended cell processes. The results of qPCR showed that there were significant differences in the expression levels of TGF－β1， ɑ－SMA， and Collagen I genes between the NC－exo， HBV－exo， NC－exo+HBV－exo， and Con groups （F=444.678， 417.144， and 571.508， all P<0.05）. After the intervention of HepGA14 cells with CTL－exo， qPCR results showed that compared with the control group， there were significant reductions in the expression levels of HBV DNA and cccDNA in HepGA14 cells （all P<0.05）， the relative mRNA expression level of HBx in exosomes （P<0.05）， and the protein expression level of HBx （P<0.05）. CTL－exo and HBV－exo were mixed at different ratios （2∶1， 5∶1， 10∶1） and were then used for the intervention of LX－2 cells， and qPCR results showed that the expression levels of TGF－β1， ɑ－SMA， and Collagen I genes in LX－2 cells gradually decreased with the increase in the ratio of CTL－exo between groups （P<0.05）. ConclusionCTL－exo can downregulate the protein expression of HBx in HBV－exo to inhibit HSC activation， suggesting that CTL－exo has an anti－hepatitis B liver fibrosis effect.