Role of apoptotic hepatocytes in HCV dissemination: regulation by acetaldehyde

Abstract

Alcohol consumption exacerbates hepatitis C virus (HCV) pathogenesis and promotes disease progression, although the mechanisms are not quite clear. We have previously observed that acetaldehyde (Ach) continuously produced by the acetaldehyde-generating system (AGS), temporarily enhanced HCV RNA levels, followed by a decrease to normal or lower levels, which corresponded to apoptosis induction. Here, we studied whether Ach-induced apoptosis caused depletion of HCV-infected cells and what role apoptotic bodies (AB) play in HCV-alcohol crosstalk. In liver cells exposed to AGS, we observed the induction of miR-122 and miR-34a. As miR-34a has been associated with apoptotic signaling and miR-122 with HCV replication, these findings may suggest that cells with intensive viral replication undergo apoptosis. Furthermore, when AGS-induced apoptosis was blocked by a pan-caspase inhibitor, the expression of HCV RNA was not changed. AB from HCV-infected cells contained HCV core protein and the assembled HCV particle that infect intact hepatocytes, thereby promoting the spread of infection. In addition, AB are captured by macrophages to switch their cytokine profile to the proinflammatory one. Macrophages exposed to HCV ϩ AB expressed more IL-1␤, IL-18, IL-6, and IL-10 mRNAs compared with those exposed to HCV Ϫ AB. The generation of AB from AGS-treated HCV-infected cells even enhanced the induction of aforementioned cytokines. We conclude that HCV and alcohol metabolites trigger the formation of AB containing HCV particles. The consequent spread of HCV to neighboring hepatocytes via infected AB, as well as the induction of liver inflammation by AB-mediated macrophage activation potentially exacerbate the HCV infection course by alcohol and worsen disease progression. HCV RNA; acetaldehyde; apoptosis; hepatocytes; macrophages ALCOHOL EXPOSURE EXACERBATES hepatitis C virus (HCV) infection severity, increases liver inflammation, and potentiates liver injury progression. However, the pathogenesis of HCV-alcohol interactions is not clear yet. The major difficulty in HCValcohol studies is related to the lack of adequate models that can recapitulate both viral replication and ethanol metabolism-two important features that potentiate liver injury progression in alcohol-abusing HCV patients. Human liver cell lines permissive for HCV (Huh7.5 or Huh 7.5.1) that are currently used for HCV-alcohol-related in vitro studies do not metabolize ethanol, while ethanol-metabolizing rodent liver cells cannot support HCV replication. Studies conducted with isolated human hepatocytes also have failed, since these cells require at least 4 -5 days to become infected with HCV; however, by this time, hepatocytes lose the expression and functional activity of CYP2E1 and alcohol dehydrogenase (ADH), the main ethanol-metabolizing enzymes (47). In vivo models of HCV infection are also questionable, since small rodents cannot be infected with human HCV, and they only transgenically express HCV proteins, in the absence of replicating virus. The best option i...

Acetaldehyde Disrupts Interferon Alpha Signaling in Hepatitis C Virus‐Infected Liver Cells by Up‐Regulating USP18

“…Therefore, these cells do not produce measurable amount of Ach. To recapitulate EtOH metabolism in hepatocytes, we exposed the cells to an artificial AGS that continuously generates physiological amounts of Ach (Ganesan et al., , ). HCV‐infected cells were exposed either to EtOH (in which case, mainly ROS were generated via CYP2E1‐mediated metabolism) or to AGS.…”

Aldehyde Dehydrogenase, Liver Disease and Cancer

“…At present, the association of ALDH genotype and viral hepatitis at the molecular level remains largely unexplored. The major difficulty is a lack of valid models in which a liver can support viral infection and alcohol metabolism that resembles liver injury caused by alcohol consumption and viral infection in alcoholic patients with chronic hepatitis C [41]. Our previous work demonstrated that alcohol-fed Aldh2 -/mice were less sensitive to concanavalin A-induced T-cell hepatitis than wild-type mice [42].…”

“…The antiviral activity of the ADH/ALDH pathway may be compromised even by a physiological alcohol concentration in alcoholic individuals, likely through alcohol-ROL metabolic competition [38]. A mechanism for acetaldehyde exposure-induced liver injury in HCV-infected cells was proposed by Ganesan et al, who found that acetaldehyde is continuously generated in the acetaldehyde-generating system (AGS), resulting in a transient increase in HCV RNA, which subsequently recedes to normal or lower levels when a significant number of HCV-infected cells undergo apoptosis [41]. Acetaldehyde is also associated with higher miR-122 and miR-34a expression in HCV-infected hepatocytes, leading to higher HCV replication, and consequently, apoptosis due to robust HCV replication and accumulation of viral products.…”

Alcohol Metabolism Potentiates HIV-Induced Hepatotoxicity: Contribution to End-Stage Liver Disease

“…To overcome this limitation, we treated RLW cells with an acetaldehyde-generating system (AGS), which contains yeast ADH as a source of enzyme, nicotinamide adenine dinucleotide (NAD) as a co-factor, and 50 mM ethanol (EtOH) (substrate for ADH), and continuously produces physiologically relevant amounts of acetaldehyde (Ach) without toxic effects. We have characterized and successfully used these cells and AGS for HCV-based ethanol in vitro studies [24,25]. The downstream effects of AGS were validated by experiments on ethanol-treated primary hepatocytes.…”

“…Here, we asked the question as to whether this ABHep formation from infected hepatocytes is beneficial or harmful for the liver. To mimic pro-apoptotic effects of AGS treatment, we generated ABHep from uninfected and HIV-infected RLW cells (apoptotic bodies control (ABcntr) and apoptotic bodies HIVinfected (ABHIV)) as described and characterized earlier [25]. These ABHep were incubated with MDMs for two hours and then inflammasome activation was measured based on NLRP3, caspase-1, IL-1β, and IL-18 mRNA expressions.…”