Thinking through acetaminophen hepatotoxicity and liver transplantation: choosing worthy recipients

Determinants of outcome among patients with acute liver failure listed for liver transplantation in the United States

Analyses of outcomes after acute liver failure (ALF) have typically included all ALF patients regardless of whether they were listed for liver transplantation (LT). We hypothesized that limiting analysis to listed patients might provide novel insights into factors associated with outcome, focusing attention on disease evolution after listing. Listed adult ALF patients enrolled in the US Acute Liver Failure Study Group registry between 2000 and 2013 were analyzed to determine baseline factors associated with 21-day outcomes after listing. We classified 617 patients (36% of overall ALF group) by 3-week outcome after study admission: 117 were spontaneous survivors (SSs; survival without LT), 108 died without LT, and 392 underwent LT. Only 22% of N-acetyl-p-aminophenol (APAP) ALF patients were listed; however, this group of 173 patients demonstrated greater illness severity: higher coma grades and more patients requiring ventilator, vasopressor, or renal replacement therapy support. Only 62/173 (36%) of APAP patients received a graft versus 66% for drug-induced liver injury patients, 86% for autoimmune-related ALF, and 71% for hepatitis B-related ALF. APAP patients were more likely to die than non-APAP patients (24% versus 17%), and the median time to death was sooner (2 versus 4.5 days). Despite greater severity of illness, the listed APAP group still had a SS rate of 40% versus 11% for non-APAP causes (P < 0.001). APAP outcomes evolve rapidly, mainly to SS or death. Patients with APAP ALF listed for LT had the highest death rate of any etiology, whereas more slowly evolving etiologies yielded higher LT rates and, consequently, fewer deaths. Decisions to list and transplant must be made early in all ALF patients, particularly in those with APAP ALF.

Transplantation of hESC-derived hepatocytes protects mice from liver injury

Background

Hepatic cell therapy has become a viable alternative to liver transplantation for life-threatening liver diseases. However, the supply of human hepatocytes is limited due to the shortage of suitable donor organs required to isolate high-quality cells. Human pluripotent stem cells reflect a potential renewable source for generating functional hepatocytes. However, most differentiation protocols use undefined matrices or factors of animal origin; as such, the resulting hepatocytes are not Good Manufacturing Practice compliant. Moreover, the preclinical studies employed to assess safety and function of human embryonic stem cell (hESC)-derived hepatocytes are generally limited to immunodeficient mice. In the present study, we evaluate the generation of hepatocytes under defined conditions using a European hESC line (VAL9) which was derived under animal-free conditions. The function capacity of VAL9-derived hepatocytes was assessed by transplantation into mice with acetaminophen-induced acute liver failure, a clinically relevant model.

Methods

We developed a protocol that successfully differentiates hESCs into bipotent hepatic progenitors under defined conditions, without the use of chromatin modifiers such as dimethyl sulphoxide. These progenitors can be cryopreserved and are able to generate both committed precursors of cholangiocytes and neonate-like hepatocytes.

Results

Thirty days post-differentiation, hESCs expressed hepatocyte-specific markers such as asialoglycoprotein receptor and hepatic nuclear factors including HNF4α. The cells exhibited properties of mature hepatocytes such as urea secretion and UGT1A1 and cytochrome P450 activities. When transplanted into mice with acetaminophen-induced acute liver failure, a model of liver damage, the VAL9-derived hepatocytes efficiently engrafted and proliferated, repopulating up to 10 % of the liver. In these transplanted livers, we observed a significant decrease of liver transaminases and found no evidence of tumourigenicity. Thus, VAL9-derived hepatocytes were able to rescue hepatic function in acetaminophen-treated animals.

Conclusions

Our study reveals an efficient protocol for differentiating VAL9 hESCs to neonatal hepatocytes which are then able to repopulate livers in vivo without tumour induction. The human hepatocytes are able to rescue liver function in mice with acetaminophen-induced acute toxicity. These results provide proof-of-concept that replacement therapies using hESC-derived hepatocytes are effective for treating liver diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0227-6) contains supplementary material, which is available to authorized users.

Pharmacologic cholinesterase inhibition improves survival in acetaminophen-induced acute liver failure in the mouse

Background

Acetaminophen (APAP) is one of the most widely used analgesic and antipyretic pharmaceutical substances in the world and accounts for most cases of drug induced liver injury resulting in acute liver failure. Acute liver failure initiates a sterile inflammatory response with release of cytokines and innate immune cell infiltration in the liver. This study investigates, whether pharmacologic acetylcholinesterase inhibition with neostigmine diminishes liver damage in acute liver failure via the cholinergic anti-inflammatory pathway.

Methods

Acute liver failure was induced in BALB/c mice by a toxic dose of acetaminophen (APAP). Neostigmine and/or N-acetyl-cysteine (NAC) were applied therapeutically at set time points and the survival was investigated. Liver damage was assessed by serum parameters, histopathology and serum cytokine assays 12 h after initiation of acute liver failure.

Results

Serum parameters, histopathology and serum cytokine assays showed pronounced features of acute liver failure 12 h after application of acetaminophen (APAP). Neostigmine treatment led to significant reduction of serum liver enzymes (LDH (47,147 ± 12,726 IU/l vs. 15,822 ± 10,629 IU/l, p = 0.0014) and ALT (18,048 ± 4,287 IU/l vs. 7,585 ± 5,336 IU/l, p = 0.0013), APAP-alone-treated mice vs. APAP + neostigmine-treated mice), inflammatory cytokine levels (IL-1β (147 ± 19 vs. 110 ± 25, p = 0.0138) and TNF-α (184 ± 23 vs. 130 ± 33, p = 0.0086), APAP-alone-treated mice vs. APAP + neostigmine-treated mice) and histopathological signs of damage.

Animals treated with NAC in combination with the peripheral cholinesterase inhibitor neostigmine showed prolonged survival and improved outcome.

Conclusions

Neostigmine is an acetylcholinesterase inhibitor that ameliorates the effects of APAP-induced acute liver failure in the mouse and therefore may provide new treatment options for affected patients.

Highly specific, sensitive and rapid enzyme immunoassays for the measurement of acetaminophen in serum

Acetaminophen antibodies were purified using affinity chromatography and labelled with horseradish peroxidase (HRP). The antibody-HRP conjugate and a new acetaminophen derivative were used in the construction of two immunoassay methods facilitating the direct quantitative measurement of acetaminophen in serum: a 96-well microtitre plate and coated-tube ELISAs. A minimum detection limit of 0.2 μg mL(-1) and a dynamic range of 0.2 to 1 μg mL(-1) in serum were achieved using the 96-well microtitre plate ELISA. The tube assay was optimised for the measurement of the clinically critical acetaminophen concentration of 50 to 250 μg mL(-1) of serum. The quantitative and specific tests could be completed within less than an hour. Common drugs including aspirin showed less than 0.1% cross-reactivity.