Establishment of an immunodeficient alcohol mouse model to study the effects of alcohol on human cells in vivo

Hepatocyte-Specific Triggering of Hepatic Stellate Cell Profibrotic Activation by Apoptotic Bodies: The Role of Hepatoma-Derived Growth Factor, HIV, and Ethanol

Liver disease is one of the leading comorbidities in HIV infection. The risk of liver fibrosis development is potentiated by alcohol abuse. In our previous studies, we reported that hepatocytes exposed to HIV and acetaldehyde undergo significant apoptosis, and the engulfment of apoptotic bodies (ABs) by hepatic stellate cells (HSC) potentiates their pro-fibrotic activation. However, in addition to hepatocytes, under the same conditions, ABs can be generated from liver-infiltrating immune cells. The goal of this study is to explore whether lymphocyte-derived ABs trigger HSC profibrotic activation as strongly as hepatocyte-derived ABs. ABs were generated from Huh7.5-CYP2E1 (RLW) cells and Jurkat cells treated with HIV+acetaldehyde and co-culture with HSC to induce their pro-fibrotic activation. ABs cargo was analyzed by proteomics. ABs generated from RLW, but not from Jurkat cells activated fibrogenic genes in HSC. This was driven by the expression of hepatocyte-specific proteins in ABs cargo. One of these proteins is Hepatocyte-Derived Growth Factor, for which suppression attenuates pro-fibrotic activation of HSC. In mice humanized with only immune cells but not human hepatocytes, infected with HIV and fed ethanol, liver fibrosis was not observed. We conclude that HIV+ABs of hepatocyte origin promote HSC activation, which potentially may lead to liver fibrosis progression.

Alcohol and HIV-Derived Hepatocyte Apoptotic Bodies Induce Hepatic Stellate Cell Activation

Recently, we found that both HIV and acetaldehyde, an alcohol metabolite, induce hepatocyte apoptosis, resulting in the release of large extracellular vesicles called apoptotic bodies (ABs). The engulfment of these hepatocyte ABs by hepatic stellate cells (HSC) leads to their profibrotic activation. This study aims to establish the mechanisms of HSC activation after engulfment of ABs from acetaldehyde and HIV-exposed hepatocytes (ABAGS+HIV). In vitro experiments were performed on Huh7.5-CYP (RLW) cells to generate hepatocyte ABs and LX2 cells were used as HSC. To generate ABs, RLW cells were pretreated for 24 h with acetaldehyde, then exposed overnight to HIV1ADA and to acetaldehyde for 96 h. Thereafter, ABs were isolated from cell suspension by a differential centrifugation method and incubated with LX2 cells (3:1 ratio) for profibrotic genes and protein analyses. We found that HSC internalized ABs via the tyrosine kinase receptor, Axl. While the HIV gag RNA/HIV proteins accumulated in ABs elicited no productive infection in LX2 and immune cells, they triggered ROS and IL6 generation, which, in turn, activated profibrotic genes via the JNK-ERK1/2 and JAK-STAT3 pathways. Similarly, ongoing profibrotic activation was observed in immunodeficient NSG mice fed ethanol and injected with HIV-derived RLW ABs. We conclude that HSC activation by hepatocyte ABAGS+HIV engulfment is mediated by ROS-dependent JNK-ERK1/2 and IL6 triggering of JAK-STAT3 pathways. This can partially explain the mechanisms of liver fibrosis development frequently observed among alcohol abusing PLWH.

Ethanol Exposure Attenuates Immune Response in Sepsis via Sirtuin 2 Expression

BACKGROUND

Sepsis and septic shock kill over 270,000 patients per year in the United States. Sepsis transitions from a hyper-inflammatory to a hypo-inflammatory phase. Alcohol dependence is a risk factor for mortality from sepsis. Ethanol (EtOH) exposure impairs pathogen clearance through mechanisms that are not fully understood. Sirtuin 2 (SIRT2) interferes with pathogen clearance in immune cells but its role in the effects of EtOH on sepsis is unknown. We studied the effect of EtOH exposure on hyper- and hypo-inflammation and the role of SIRT2 in mice.

METHODS

We exposed C57Bl/6 (WT) mice to EtOH via drinking water and used intraperitoneal cecal slurry (CS)-induced sepsis to study: (i) 7-day survival, (ii) leukocyte adhesion (LA) in the mesenteric microcirculation during hyper- and hypo-inflammation, (iii) peritoneal cavity bacterial clearance, and (iv) SIRT2 expression in peritoneal macrophages. Using EtOH-exposed and lipopolysaccharide (LPS)-stimulated RAW 264.7 (RAW) cell macrophages for 4 hours or 24 hours, we studied: (i) tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), and SIRT2 expression, and (ii) the effect of the SIRT2 inhibitor AK-7 on inflammatory response at 24 hours. Lastly, we studied the effect of EtOH on sepsis in whole body Sirt2 knockout (SIRT2KO) mice during hyper- and hypo-inflammation, bacterial clearance, and 7-day survival.

RESULTS

WT EtOH-sepsis mice showed: (i) Decreased survival, (ii) Muted LA in the microcirculation, (iii) Lower plasma TNF-α and IL-6 expression, (iv) Decreased bacterial clearance, and (v) Increased SIRT2 expression in peritoneal macrophages versus vehicle-sepsis. EtOH-exposed LPS-stimulated RAW cells showed: (i) Muted TNF-α, IL-6, and increased IL-10 expression at 4 hours, (ii) endotoxin tolerance at 24 hours, and (iii) reversal of endotoxin tolerance with the SIRT2 inhibitor AK-7. EtOH-exposed SIRT2KO-sepsis mice showed greater 7-day survival, LA, and bacterial clearance than WT EtOH-sepsis mice.

CONCLUSION

EtOH exposure decreases survival and reduces the inflammatory response to sepsis via increased SIRT2 expression. SIRT2 is a potential therapeutic target in EtOH with sepsis.