A Role of Renal Replacement Therapy for Acute Liver Failure.

Pathogenesis of Liver Injury in Acute Liver Failure

Serum Apoptosis Markers in Acute Liver Failure: A Pilot Study

Beta-Catenin Activation Promotes Liver Regeneration after Acetaminophen-Induced Injury

Children with acute liver failure (ALF) often experience hyperammonaemia, fluid overload, metabolic derangements, and multi-organ failure. Continuous renal replacement therapy (CRRT) is commonly used for renal and non-renal indications, particularly in those with hyperammonaemia and hepatic encephalopathy. However, the non-selective nature of CRRT can result in the clearance of beneficial metabolites and liver-related biomarkers, which are important for monitoring disease progression or improvement. Therefore, understanding the kinetic principles governing molecular clearance during CRRT is crucial for accurate interpretation of liver biochemistry to inform clinical decision-making. By considering the kinetic properties of hepatic markers, including bilirubin, bile acids, liver enzymes, metabolites, waste products, inflammatory markers, albumin, and coagulation proteins, we describe the impact of CRRT on the plasma levels of these markers. In addition, we discuss various CRRT attributes, and the removal of these markers is also discussed. Metabolites and waste products, including ammonia, lactate, and urea, are the most useful markers to inform CRRT responsiveness, owing to their small molecular size, low degree of protein binding, and small volume of distribution; whereas bilirubin, bile acids, coagulation factors, and albumin remain true indicators of hepatic function and clinical condition. It should be noted that the overall plasma levels of any molecules reflect the balance between production and clearance, even for molecules with a high degree of CRRT removal. Awareness of these properties helps clinicians differentiate dialytic response versus genuine hepatic recovery or deterioration, guiding a more rational interpretation of clinical progression in ALF with liver transplant/spontaneous native recovery or mortality as the outcomes.Conclusion: Understanding the kinetic behaviour of liver-related markers during CRRT is essential to distinguish between dialytic clearance and true changes in hepatic function. This knowledge enables more accurate clinical interpretation, guiding decision-making in children with acute liver failure and optimizing management strategies toward recovery or timely transplantation.What is Known:• Children with acute liver failure often require CRRT for non-renal causes, including metabolic derangements, hyperammonemia, and multi-organ support.• CRRT non-selectively clears both toxic metabolites and liver-related biomarkers, complicating the interpretation of hepatic function.What is New:• Accounting for the kinetic properties of liver markers during CRRT allows clinicians to distinguish dialytic clearance from true hepatic recovery or deterioration.• Small molecules (ammonia, lactate, urea) might reflect CRRT responsiveness, whereas bilirubin, bile acids, albumin, and coagulation factors indicate liver function and clinical status.

Acute Liver Failure: Indian Perspective.

The acute inflammatory milieu in patients with acute liver failure (ALF) results in 'toxic' blood in these patients. In vitro experiments have shown that the plasma obtained from ALF patients is toxic to rabbit hepatocytes and inhibits regeneration of rat hepatocytes. Treatments such as plasma exchange and continuous renal replacement therapy to cleanse the blood have improved survival in ALF patients. In the liver microcirculation, the exchange of fluid across fenestrae in liver sinusoidal endothelial cells (LSECs) is vital for proper functioning of hepatocytes. Clogging of the liver filter bed by inflammatory debris and cells ('traffic jam hypothesis') impeding blood flow in sinusoids may in turn reduce the exchange of fluid across LSEC fenestrae and cause dysfunction and necrosis of hepatocytes in ALF patients. In mouse model of paracetamol overdose, disturbances in microcirculation in the liver preceded the development of injury and necrosis of hepatocytes. This may represent a reversible pathophysiological mechanism in ALF which may be improved by the anti-inflammatory effect of plasma exchange. Wider access to urgent plasma exchange is a major advantage compared to urgent liver transplantation to treat ALF patients worldwide, especially so in resource constrained settings. Continuous hemo-filtration or dialysis is used toreduce ammonia levels and treat cerebral edema in ALF patients. In this review, we discuss the different modalities to cleanse the blood in ALF patients, with an emphasis on plasma exchange, from a hepatology perspective.

Currently, the most effective therapy for acute liver failure and advanced cirrhosis is liver transplantation. However, this procedure has several limitations, including lack of donors, surgical complications, immunological suppression, and high medical costs. The alternative approaches that circumvent the use of a whole liver, such as stem cell transplantation, have been suggested as an effective alternate therapy for hepatic diseases. Mesenchymal stem cells (MSCs), also known as multipotent mesenchymal stromal cells, are self-renewing cells that can be found in almost all postnatal organs and tissues, including liver. During the past decade, great progress has been made in the field of MSC-dependent liver regeneration and immunomodulation. Because of their potential for differentiation into hepatocytes as well as their immunomodulatory characteristics, MSCs are considered as promising therapeutic agents for the therapy of acute liver failure and cirrhosis. In this concise review, we have summarized therapeutic potential of MSCs in the treatment of acute liver failure and cirrhosis, emphasizing their regenerative and immunomodulatory characteristics after engraftment in the liver. We have also presented several outstanding problems including conflicting data regarding MSCs engraftment in the liver and unwanted mesenchymal lineage differentiation in vivo which limits MSC therapy as a mainstream treatment approach for liver regeneration. It can be concluded that efficient and safe MSC-based therapy for acute and chronic liver failure remains a challenging issue that requires more investigation and continuous cooperation between clinicians, researchers, and patients.

Mesenchymal stem cells increase heme oxygenase 1-activated autophagy in treatment of acute liver failure

The Continuing Challenge of “Indeterminate” Acute Liver Failure in Children

The simple answer to the question in the title is “no”. The complex answer involves looking into the “crystal ball” of prognostic markers yet again. “Fulminant hepatic failure” or acute liver failure (ALF) is a rare disorder which has devastating consequences. Predicting which patients require liver transplantation can be difficult at times. Early transplantation of a patient with hyper-acute liver failure secondary to paracetamol (acetaminophen) may be unnecessary. Late transplantation can reduce the chance of a successful outcome. The ideal prognostic marker should have high sensitivity and specificity allowing for prognostic information to be of clinical use early in the disease course. POD, paracetamol (acetaminophen); ALF, acute liver failure; KCH, King's College Hospital; MELD, Model for End-Stage Liver Disease; APACHE, Acute Physiology and Chronic Health Evaluation; PPV, positive predictive value; NPV, negative predictive value. All prognostic models have their limitations. The most widely used are the King's College Hospital (KCH) criteria.1 These were derived from a cohort of 588 patients presenting with acute liver failure during 1973-1985.1 They have clearly demonstrated the importance of underlying etiology in determining prognosis of ALF. They have been evaluated by other groups2-4 and are now benchmarked against all new prognostic markers of ALF. A review of the practical use of the KCH criteria is found elsewhere.5 The KCH criteria for paracetamol (POD)-induced ALF have been subject to a meta-analysis which revealed that although the criteria were specific, the sensitivity was low, suggesting that a number of patients who don't fulfill criteria will die without transplantation.6 More recently, a prospective study demonstrated that the addition of arterial blood lactate levels to the KCH POD criteria increased their sensitivity.7 However, the full impact of arterial blood lactate measurements as a prognostic marker in POD-induced ALF remains to be determined.8, 9 There is no doubt that modern intensive care has improved outcomes in POD-induced ALF. This is reflected in increasing spontaneous survivor rates in this group of patients relative to patients with non–POD-induced ALF whose prognosis remains poor without transplantation.10 Even when patients fulfill KCH POD criteria or are listed for liver transplantation, it appears that an increasing percentage of them survive without grafting.11, 12 Other prognostic markers of ALF include the Clichy criteria, which was developed from a cohort of 115 patients with ALF secondary to HBV infection.13 They define a poor prognosis by the grade of hepatic encephalopathy and factor V levels.13 The KCH and Clichy criteria have been compared as prognostic markers in ALF,14, 15 and the KCH criteria have gained more widespread use due in part to the lack of readily available factor V level measurements. Further prognostic markers for POD-induced ALF have been developed and include serum phosphate levels,3, 8 the MELD (Model for End-Stage Liver Disease) score,16 and APACHE II measurements.12, 17 None have gained widespread use. It is possible that APACHE III measurements may supplement the KCH criteria by identifying nonsurvivors among patients who do not fulfill the KCH POD criteria.18 Newer prognostic markers undergoing evaluation for non–POD-induced ALF include the MELD score10 and arterial blood lactate levels.8, 19 In this issue, Schiødt et al. test the predictive value of actin-free Gc-globulin in ALF.20 The plasma protein Gc-globulin (also known as vitamin D–binding protein) is a multifunctional protein whose properties include transporting vitamin D metabolites21 and actin scavenging.22 The authors previously showed that serum concentrations of Gc-globulin have prognostic value in ALF.23, 24 More recently, they tested prospectively the ability of total serum Gc-globulin to predict outcome in patients with ALF as part of the US ALF study group.25 They hypothesize that the fraction of Gc-globulin not bound to actin may represent a more sensitive prognostic marker than total Gc-globulin (that is, the actin-free Gc-globulin) in ALF, because the actin-free concentration of Gc-globulin possibly represents the hepatic reserve or capacity of the actin scavenger system.20 Until recently, actin-free Gc-globulin has been difficult to measure in a timely manner and analytical tools have not been commercially available. The authors measured actin-free Gc-globulin using a rapid new ELISA kit to determine its prognostic value relative to the KCH criteria in a total of 252 patients with varying aetiologies from the US ALF Study Group registry.20 The first 178 patients registered constituted the learning set, whereas the last 74 patients served as a validation set. The spontaneous survival rate (that is, transplantation-free) was 75% (82 of 110 patients) in the POD group and only 30% (43 of 142 patients) in the nonPOD group. They found that median actin-free Gc-globulin levels on admission and at day 3 were significantly reduced compared to controls. Actin-free Gc-globulin levels were also significantly higher in spontaneous survivors than in patients who died or underwent transplantation. A receiver operating characteristic (ROC) curve yielded a 40 mg/L cut-off for actin-free Gc-globulin as providing the best prognostic information (the area under the curve was 0.7), similar to a previous study.23 Using this 40 mg/L level of actin-free Gc-globulin, the positive predictive value (PPV) was low (50%) and the negative predictive value (NPV) was high (81%) in the POD group of the validation set, whereas the opposite was true in the non-POD group (76% PPV and 50% NPV).20 How do their results compare to KCH criteria? Actin-free Gc-globulin levels yielded PPV and NPV of 68% and 67%, respectively, which was similar to the corresponding PPV and NPV values for the KCH criteria of 72% and 64%, respectively.20 Thus, the predictive values of actin-free Gc-globulin and KCH criteria were not different. Combining actin-free Gc-globulin with the KCH criteria did not improve their prognostic ability. A larger cohort of POD-induced ALF patients in the US ALF study group also demonstrated underperformance of the KCH criteria.12 Why does the prognostic value of KCH criteria perform poorly in the United States? This issue was addressed by Schiødt et al. in their discussion20 and has been commented on in previous editorials.26 The use of FFP prior to enrollment in the US ALF study group may have had an impact on admission INR and Gc-globulin levels and thus influence the prognostic value of both markers. How do actin-free Gc-globulin levels compare to total Gc-globulin levels as a prognostic marker in ALF?25 Total Gc-globulin levels were not useful in predicting outcome in POD-induced ALF.25 Using an 80 mg/L level of total Gc-globulin, Schiødt et al. previously demonstrated a PPV and NPV of 85% and 43%, respectively, for non–POD-induced ALF.25 Thus, it appears that actin-free Gc-Globulin is a more sensitive prognostic marker than total Gc-globulin in POD-induced ALF. However as the authors conclude, further refinements and combinations with other prognostic markers in ALF will be necessary before the actin-free Gc-globulin ELISA assay can be recommended for routine clinical use. The limitations of actin-free Gc-globulin testing as a prognostic marker in ALF are similar to other prognostic markers. Prolonged serial monitoring of actin-free Gc-globulin levels may be of more clinical use. Patients with low serum levels of actin-free Gc-globulin had a worse outcome than those with higher levels although there was a degree of overlap as there invariably is with prognostic markers. The hepatic synthesis of Gc-globulin is increased in ALF,27 and higher levels of actin-free Gc-globulin may reflect increasing hepatocyte regeneration with greater potential for recovery. On the other hand, low Gc-globulin levels could be due to an increased Gc-globulin consumption or the lack of synthesis due to a failing liver which will not recover spontaneously. In keeping with this, the authors observed greater improvement in actin-free Gc-globulin levels in patients who recovered spontaneously, although the numbers studied were small.20 The authors postulate that lack of sufficient Gc-globulin and subsequent tissue ischemia caused by precipitation of actin filaments could partly explain why high arterial blood lactate levels are associated with a poor prognosis in ALF. The prognostic value of combining Gc-globulin levels and arterial blood lactate levels is worth pursuing in studies of POD-induced ALF. Clinical judgement is still very important in listing decisions by the transplant team. Psychosocial considerations may override prognostic criteria and contraindicate liver transplantation. Clearly, a single measurement at one point in time is not the answer, and measurements of serial prognostic markers will be required. Combining prognostic criteria also needs to be studied further. The “holy grail” of prognostication in ALF remains elusive and we continue to search for it. There is no doubt that better markers of outcome in ALF will help us make the right clinical decisions for our patients.

Measurement of Serum Acetaminophen–Protein Adducts in Patients With Acute Liver Failure

Mesenchymal stem cells therapy for acute liver failure: Recent advances and future perspectives

Acute liver failure is a rapidly progressive deterioration of hepatic function resulting in high mortality and morbidity. Metabolic enzymes can translocate to the nucleus to regulate histone acetylation and gene expression. Levels and activities of pyruvate dehydrogenase complex (PDHC) and lactate dehydrogenase (LDH) were evaluated in nuclear fractions of livers of mice exposed to various hepatotoxins including CD95-antibody, α-amanitin, and acetaminophen. Whole-genome gene expression profiling by RNA-seq was performed in livers of mice with acute liver failure and analyzed by gene ontology enrichment analysis. Cell viability was evaluated in cell lines knocked-down for PDHA1 or LDH-A and in cells incubated with the LDH inhibitor galloflavin after treatment with CD95-antibody. We evaluated whether the histone acetyltransferase inhibitor garcinol or galloflavin could reduce liver damage in mice with acute liver failure. Levels and activities of PDHC and LDH were increased in nuclear fractions of livers of mice with acute liver failure. The increase of nuclear PDHC and LDH was associated with increased concentrations of acetyl-CoA and lactate in nuclear fractions, and histone H3 hyper-acetylation. Gene expression in livers of mice with acute liver failure suggested that increased histone H3 acetylation induces the expression of genes related to damage response. Reduced histone acetylation by the histone acetyltransferase inhibitor garcinol decreased liver damage and improved survival in mice with acute liver failure. Knock-down of PDHC or LDH improved viability in cells exposed to a pro-apoptotic stimulus. Treatment with the LDH inhibitor galloflavin that was also found to inhibit PDHC, reduced hepatic necrosis, apoptosis, and expression of pro-inflammatory cytokines in mice with acute liver failure. Mice treated with galloflavin also showed a dose-response increase in survival. PDHC and LDH translocate to the nucleus, leading to increased nuclear concentrations of acetyl-CoA and lactate. This results in histone H3 hyper-acetylation and expression of damage response genes. Inhibition of PDHC and LDH reduces liver damage and improves survival in mice with acute liver failure. Thus, PDHC and LDH are targets for therapy of acute liver failure. Acute liver failure is a rapidly progressive deterioration of liver function resulting in high mortality. In experimental mouse models of acute liver failure, we found that two metabolic enzymes, namely pyruvate dehydrogenase complex and lactic dehydrogenase, translocate to the nucleus resulting in detrimental gene expression. Treatment with an inhibitor of these two enzymes was found to reduce liver damage and to improve survival.

Potential conflict of interest: Nothing to report. We appreciate Kalal et al.'s comments to our article “Continuous Renal Replacement Therapy Is Associated With Reduced Serum Ammonia Levels and Mortality in Acute Liver Failure.”1 In acute liver failure, the lack of liver capacity to metabolize ammonia into urea and glutamine leads to its accumulation in the bloodstream. Uptake of part of this ammonia by the brain, muscle, and other tissues results in a gradient between arterial and venous ammonia levels.2 Therefore, the arterial ammonia level has been found to be a better surrogate for the risk of cerebral edema, intracranial hypertension, and mortality in acute liver failure.3 Nevertheless, venous ammonia has been shown to correlate well with arterial ammonia and to be associated with such clinical endpoints in acute liver failure.2 Taking this into account and to maximize sample size and the internal validity of our results, we decided to use both arterial and venous ammonia measurements. Furthermore, we were especially interested in the ammonia variation from days 1‐3 post–study inclusion with and without renal replacement therapy (RRT). Finally, in our cohort (n = 1,186), while the serum ammonia level (arterial or venous) at study inclusion was associated with 21‐day transplant‐free mortality (P < 0.001), the type of ammonia (arterial versus venous) at study inclusion was not associated with 21‐day transplant‐free mortality (P = 0.49). Moreover, median arterial and venous ammonia levels were similar for each of the continuous RRT, intermittent RRT, and no RRT subgroups on days 1, 2, and 3 (P ≥ 0.08 for all comparisons). Thus, we believe that our methodology was robust to extract our conclusions.

Plasma exchange has gained widespread acceptance as an effective mode of blood purification in patients suffering from acute hepatic failure. However, it is still undetermined whether a single use of plasma exchange is capable of removing inflammatory cytokines completely or of preventing the development of citrate toxicity inherent with fresh frozen plasma. To clarify these issues we developed combined plasma exchange and continuous hemodiafiltration (CHDF) modality in which CHDF is performed in an opposite direction to plasma exchange. This study was designed to assess the effectiveness of combined modality therapy. Fifteen patients with acute hepatic failure were treated with plasma exchange (plasma exchange group) or plasma exchange and CHDF (plasma exchange + CHDF group), and various biochemical parameters were determined before and after treatment. Although citrate levels increased significantly after treatment compared with pretreatment levels in both the plasma exchange group and the plasma exchange + CHDF group, the percentage of the increase in citrate levels was significantly higher in the plasma exchange group than in the plasma exchange + CHDF group. Bilirubin levels were significantly lower after treatment in both the plasma exchange and plasma exchange + CHDF groups. There were no significant differences in tumor necrosis factor-alpha levels before and after treatment in the plasma exchange group, but they were significantly lower after treatment in the plasma exchange + CHDF group. Interleukin-6 (IL-6) levels increased significantly after treatment in the plasma exchange group, but there were no significant differences in the IL-6 levels before and after treatment in the plasma exchange + CHDF group. Interleukin-8 levels increased significantly after treatment in the plasma exchange group while decreasing significantly after treatment in the plasma exchange + CHDF group. These results indicate that combining plasma exchange and CHDF in a parallel circuit is an effective modality for suppressing the elevation of blood citrate levels and for removing inflammatory cytokines. This finding may have important implications for the development of an effective treatment for patients with acute hepatic failure.