Non-ISGylated HIV proteins are sorted to hepatic exosomes to activate liver fibrosi - In an era of improved survival due to modern antiretroviral therapy (ART), liver disease has become a major
cause of morbidity and mortality among HIV-infected persons causing death in 15–17% of HIV-infected patients.
Whereas the rate of alcohol abuse is approximately 4.6% in the general U.S. population, 8% of HIV-infected
individuals in U.S. cohorts can be classified as heavy drinkers. Despite the great progress in the development of
efficient and less liver-toxic ART, current ART regimens do not eliminate all symptoms associated with HIV-
induced pathology in various organs, including the liver. HIV-induced liver fibrosis is a frequent event in people
living with HIV (PLWH), and it is further potentiated by alcohol use disorders (AUD). Previously, we have shown
that hepatocytes exposed to HIV and ethanol express HIV RNA and HIV proteins and secrete the highest levels
of extracellular vesicles (EVs/exosomes). These EVs may program the activation of non-parenchymal liver cells,
including hepatic stellate cells (HSC) to promote the fibrosis progression. However, it is not clear which
components of exosome cargo are responsible for HSC activation. Here, we explore the possibility that liver
fibrogenic effects are induced by HIV proteins contained in hepatocyte-derived EVs. In this regard, we will focus
on HIV proteins post-translationally modified with ubiquitin-like ISG15, the product of interferon-stimulated genes
(ISGs) that promotes protein ISGylation to reduce toxicity of HIV proteins and decrease its release with EVs. In
preliminary experiments, we demonstrated that protein ISGylation is suppressed in HIV-infected hepatocytes
treated with ethanol metabolites and the engulfment of these exosomes by HSC induced their pro-fibrotic
activation. These data allowed us to generate the hypothesis: Ethanol metabolism sorts of HIV proteins to
exosomes via suppression of protein ISGylation in hepatocytes. These exosomes with non-ISGylated HIV
protein cargo are internalized by hepatic stellate cells (HSC) to induce pro-fibrotic activation. This hypothesis will
be tested in two Specific Aims: Aim1: To study the effects of ethanol metabolism on HIV protein ISGylation in
hepatocytes and subsequent release of HIV proteins with exosomes; Aim 2: To elucidate the effects of
exosomes derived from HIV-ethanol exposed hepatocytes on pro-fibrotic activation of hepatic stellate cells
(HSC). Here, we will use multiple in vitro and in vivo approaches. Our experimental results will offer strong
translatable potential into clinical practice by clarifying one of the mechanisms of HIV-alcohol-induced liver
fibrosis development, which requires therapeutic interventions additional to ART to prevent liver disease
progression.
