Microcirculatory disturbance in acute liver injury is triggered by IFNγ-CD40 axis.

BACKGROUND: Acute liver failure (ALF) is a life-threatening disorder that progresses from self-limiting acute liver injury (ALI). Microcirculatory disturbance characterized by sinusoidal hypercoagulation and subsequent massive hypoxic hepatocyte damage have been proposed to be the mechanism by which ALI deteriorates to ALF; however, the precise molecular pathway of the sinusoidal hypercoagulation remains unknown. Here, we analyzed ALI patients and mice models to uncover the pathogenesis of ALI with microcirculatory disturbance. METHODS: We conducted a single-center retrospective study for ALI and blood samples and liver tissues were analyzed to evaluate the microcirculatory disturbance in ALI patients (n = 120). Single-cell RNA sequencing analysis (scRNA-seq) was applied to the liver from the concanavalin A (Con A)­induced mouse model of ALI. Interferon-gamma (IFNγ) and tumor necrosis factor-alpha knockout mice, and primary human liver sinusoidal endothelial cells (LSECs) were used to assess the mechanism of microcirculatory disturbance. RESULTS: The serum IFNγ concentrations were significantly higher in ALI patients with microcirculatory disturbance than in patients without microcirculatory disturbance, and the IFNγ was upregulated in the Con A mouse model which presented microcirculatory disturbance. Hepatic IFNγ expression was increased as early as 1 hour after Con A treatment prior to sinusoidal hypercoagulation and hypoxic liver damage. scRNA-seq revealed that IFNγ was upregulated in innate lymphoid cells and stimulated hepatic vascular endothelial cells at the early stage of liver injury. In IFNγ knockout mice treated with Con A, the sinusoidal hypercoagulation and liver damage were remarkably attenuated, concomitant with the complete inhibition of CD40 and tissue factor (TF) upregulation in vascular endothelial cells. By ligand-receptor analysis, CD40-CD40 ligand interaction was identified in vascular endothelial cells. In human LSECs, IFNγ upregulated CD40 expression and TF was further induced by increased CD40-CD40 ligand interaction. Consistent with these findings, hepatic CD40 expression was significantly elevated in human ALI patients with microcirculatory disturbance. CONCLUSION: We identified the critical role of the IFNγ-CD40 axis as the molecular mechanism of microcirculatory disturbance in ALI. This finding may provide novel insights into the pathogenesis of ALI and potentially contribute to the emergence of new therapeutic strategies for ALI patients.

Acute kidney injury is an unfavorable prognostic factor in acute liver failure and is associated with tumor necrosis factor-alpha.

Acute kidney injury (AKI) is a common complication of acute liver failure (ALF); but its pathogenesis is unknown. ALF was divided into 2 subgroups; ALF with hepatic coma, which corresponds to ALF in the US and Europe, and ALF without hepatic coma. AKI has been shown to worsen the prognosis of ALF patients with hepatic coma; however, its prognostic significance in ALF without hepatic coma remains unknown. A single-center retrospective study of 174 patients with ALF was performed. AKI was defined according to KDIGO criteria. AKI developed in 29 (66.0%) of 44 ALF patients with hepatic coma and 27 (38.5%) of 130 ALF patients without hepatic coma. Systemic inflammatory response syndrome (SIRS) was found to be significantly associated with AKI incidence in ALF patients (P < .001). Tumor necrosis factor-alpha (TNF-α) was found to be significantly associated with the presence and severity of AKI (P = .0039 and P = .0140, respectively). On multivariate analysis, TNF-α was an independent risk factor linked with AKI (P = .0103). Even in the absence of hepatic coma, the transplant-free survival rate of ALF was significantly associated with the presence and severity of AKI. Even when hepatic coma is absent, AKI complicated in ALF is strongly associated with TNF-α and worsens the transplant-free survival rate. Before the onset of hepatic coma, plasma exchange, or extracorporeal blood purification to remove inflammatory cytokines should be considered in ALF patients.

Upregulated expression of hypoxia reactive genes in peripheral blood mononuclear cells from chronic liver disease patients.

Liver fibrosis induces intrahepatic microcirculation disorder and hypoxic stress. Hypoxic stress has the potential for an increase in the possibility of more liver fibrosis and carcinogenesis. Liver biopsy is a standard method that evaluates of intrahepatic hypoxia, however, is invasive and has a risk of bleeding as a complication. Here, we investigated the hypoxia reactive gene expressions in peripheral blood mononuclear cells (PBMC) from chronic liver disease patients to evaluate intrahepatic hypoxia in a non-invasive manner. The subjects enrolled for this study were composed of 20 healthy volunteers (HV) and 48 patients with chronic liver disease (CLD). CLD patients contained 24 patients with chronic hepatitis（CH）and 24 patients with liver cirrhosis (LC). PBMC were isolated from heparinized peripheral blood samples. We measured the transcriptional expression of hypoxia reactive genes and inflammatory cytokines by quantitative RT-PCR. mRNA expression of adrenomedullin (AM), vascular endothelial growth factor A (VEGFA) superoxide dismutase (SOD), glutathione peroxidase (GPx) (p < 0.05), Interleukin-6 (IL-6), transforming growth factor-beta (TGF-ß) and heme oxygenase-1 (HO-1) in CLD group were significantly higher than HV. AM mRNA expression is correlated with serum lactate dehydrogenase (LDH), serum albumin (Alb), IL6, and SOD mRNA expression. The hypoxia reactive gene expression in PBMCs from CLD patients was more upregulated than HV. Especially, angiogenic genes were notably upregulated and correlated with liver fibrosis. Here, we suggest that mRNA expression of AM in PBMCs could be the biomarker of intrahepatic hypoxia.

Microcirculatory disturbance in acute liver injury.

Microcirculatory disturbance is thought to be involved in the pathogenesis of acute liver injury (ALI). The current study examined the pathophysiologic role of hepatic microcirculatory disturbance in patients with ALI and in mouse models of ALI. Using serum aminotransferase (ALT)/lactate dehydrogenase (LDH) ratio as a hypoxic marker, 279 patients with ALI were classified into the low ALT/LDH ratio (ALT/LDH ≤1.5) and high ALT/LDH ratio group (ALT/LDH >1.5). In the low ALT/LDH ratio group, serum ALT, LDH, fibrinogen degradation products and prothrombin time-international normalized ratio were increased relative to the high ALT/LDH ratio group. Histologically, hepatic expression of tissue factor (TF) and hypoxia-related proteins was enhanced in the low ALT/LDH ratio group, and this was accompanied by sinusoidal fibrin deposition. Sinusoidal hypercoagulation and intrahepatic hypoxia was also analyzed in two different mouse models of ALI; Concanavalin A (ConA) mice and Galactosamine/tumor necrosis factor (TNF)-α (G/T) mice. Serum ALT/LDH ratio in ConA mice was significantly lower compared with G/T mice. Pimonidazole staining revealed the upregulation of hypoxia-related proteins in ConA mice. Recombinant human soluble thrombomodulin improved liver damage in ConA mice in association with reduced sinusoidal hypercoagulation and intrahepatic hypoxia. The present study provides evidence that serum ALT/LDH ratio aids in the identification of patients with ALI and intrahepatic hypoxia as a result of microcirculatory disturbance. The results facilitate the improved understanding of the pathogenesis of ALI, thereby offering a novel therapeutic strategy against ALI, which arises from sinusoidal hypercoagulation.

Metabolic Alteration in Hepatocellular Carcinoma: Mechanism of Lipid Accumulation in Well-Differentiated Hepatocellular Carcinoma.

Objective: Metabolic alteration is widely considered as one of the hallmarks of cancer. Hepatocellular carcinoma (HCC) presents a unique pathological feature in which lipid accumulation is common in well-differentiated HCC and rare in poorly differentiated HCC; however, the underlying mechanism remains unclear. Methods: Tissue samples were obtained from 103 HCC patients who had undergone hepatic resection and 12 living donors of liver transplantation. We evaluated metabolic gene expressions in cancer tissues as well as background noncancer tissues and compared the expressions by the degree of cancer differentiation and by liver disease states. Besides, the metabolomics was evaluated and integrated to gene expressions in nonalcoholic steatohepatitis (NASH)-HCC model mice. Results: In cancer tissues, the expression levels of enzymes related to glycolysis, pentose phosphate pathway (PPP), and fatty acid (FA) synthesis were increased and that of tricarboxylic acid (TCA) cycle and ß-oxidation were suppressed. Same metabolic alterations were observed in noncancer tissue as the liver disease progresses from healthy liver to chronic hepatitis, cirrhosis, and HCC. Similar alterations of metabolic genes were detected in NASH-HCC mice, which were consistent with the results of metabolomics. As the degree of cancer differentiation decreased, glycolysis and PPP were accelerated; however, FA synthesis and uptake were diminished. Conclusions: The metabolic alterations including glycolysis, PPP, TCA cycle, and ß-oxidation became more prominent as liver disease progresses from normal, chronic hepatitis, cirrhosis, well-, moderately, and poorly differentiated HCC. FA synthesis and uptake were highest in well-differentiated HCC, which could explain the lipid accumulation.

Clinical Features of Liver Injury Induced by Immune Checkpoint Inhibitors in Japanese Patients.

Aim: Immune checkpoint inhibitors (ICIs) have improved the survival rate of patients carrying various malignant neoplasms. Despite their efficacy, ICIs occasionally induce liver injury as an immune-related adverse event (irAE). This study aimed to reveal the clinical features of the hepatic irAE in Japanese patients. Methods: Among 387 patients treated with ICIs, those who developed drug-induced liver injury were investigated. We also describe the histological findings and clinical courses of four patients with hepatic irAE who underwent liver biopsy. Results: Among the 56 patients with all-grade liver injury, only 11 (19.6%) showed hepatocellular-type liver injury, which resembled autoimmune hepatitis. Thirty-four patients (60.7%) developed cholestatic or mixed-type liver injury, although only one patient showed abnormal image findings in the bile duct. Most patients with grade ≤2 liver injury improved spontaneously, while two patients with biliary dysfunction required ursodeoxycholic acid or prednisolone. Among eight patients with grade ≥3 liver injury, three required no immunosuppressants and five were treated with prednisolone (three of five patients required other types of immunosuppressants). Four patients in the case series showed diverse clinical features in terms of hepatotoxic pattern, symptoms, and the interval time between the initiation of immunotherapy and the onset of the hepatic irAE. Conclusions: Our findings suggest that ICIs could cause microscopic biliary disorder without any abnormal image finding. Because the hepatic irAE presents diverse clinical features, liver biopsy is recommended to provide appropriate treatments.