HCV, Heroin Use, and MicroRNAs

Abstract

Hepatitis C virus (HCV) infection is common among injection drug users (IDUs). There is accumulating evidence that circulating microRNAs (miRNAs) are related to HCV infection and disease progression. The present study was undertaken to determine the in vivo impact of heroin use on HCV infection and HCV-related circulating miRNA expression. Using the blood specimens from four groups of study subjects (HCV-infected individuals, heroin users with/without HCV infection, and healthy volunteers), we found that HCV- infected heroin users had significantly higher viral load than HCV-infected non-heroin users (p=0.0004). Measurement of HCV-related circulating miRNAs in plasma showed that miRs-122, 141, 29a, 29b, and 29c were significantly increased in the heroin users with HCV infection, whereas miR-351, an HCV inhibitory miRNA, was significantly decreased in heroin users as compared to control subjects. Further investigation identified a negative correlation between the plasma levels of miR-29 family members and severity of HCV infection based on aspartate aminotransferase to platelet ratio index (APRI). Heroin use and/or HCV infection also dysregulated a panel of plasma miRNAs. Taken together, these data for the first time revealed in vivo evidence that heroin use and/or HCV infection alter circulating miRNAs, which provides a novel mechanism for the impaired innate anti-HCV immunity among IDUs. Recent studies revealed that extracellular miRNAs were able to incorporate into cell-derived exosomes as a method of cell-to-cell interaction. Exosomes are a class of cell-released small vesicles that mediate intercellular communication by delivering functional factors to recipient cells. During HCV infection, the interaction between liver resident macrophages and hepatocytes is important for host defense and viral elimination, triggered by innate immune activation, especially Toll like receptors (TLR). In our study, we explored the role of macrophage-derived exosomes in the transmission of innate immune responses against HCV infection in hepatocytes, and the involvement of exosomal miRNAs in transferring the anti-HCV activities. We reported that upon TLR3 activation, macrophages shed exosomes that were able to attenuate HCV-JFH1 infection in Huh7 cells. We further demonstrated that exosomes from poly I:C treated macrophages were internalized by Huh7 cells, which induced the intercellular anti-HCV responses (type I interferon, interferon stimulated genes, etc.) and thus drastically inhibited HCV infection in Huh7 cells. Moreover, using an in vitro macrophage and Huh7 cell co-culture model, we also found exosomes mediated HCV suppression in Huh7 cells after TLR3 activation. The presence of exosome inhibitor in co-culture compromised the anti-HCV activity by TLR3-activated macrophages. Interestingly, the miRNA-29 family, which was reported to suppress HCV infection, was significantly increased in the macrophage exosomes after TLR3 activation. The inhibition of miRNA-29 partially compromised the anti-HCV activity of TLR3-activated macrophages, indicating the potential involvement of exosomal miRNAs in the transmission of anti-HCV activity from macrophages to Huh7 cells through exosomes. In conclusion, this study proposed an antiviral mechanism of TLR3 activation that involves the intercellular communication between immune cells and hepatic parenchymal cells via exosomes, and exosomal miRNAs. This discovery sheds light on exploiting the therapeutic potential of new drugs against HCV infection.