The Role of miRNAs in the Pathophysiology of Liver Diseases and Toxicity.

Both acute and chronic liver toxicity represents a major global health burden and an important cause of morbidity and lethality worldwide. Despite epochal progress in the treatment of hepatitis C virus infections, pharmacological treatment strategies for most liver diseases are still limited and new targets for prevention or treatment of liver disease are urgently needed. MicroRNAs (miRNAs) represent a new class of highly conserved small non-coding RNAs that are involved in the regulation of gene expression by targeting whole networks of so called "targets". Previous studies have shown that the expression of miRNAs is specifically altered in almost all acute and chronic liver diseases. In this context, it was shown that miRNA can exert causal roles, being pro- or anti-inflammatory, as well as pro- or antifibrotic mediators or being oncogenes as well as tumor suppressor genes. Recent data suggested a potential therapeutic use of miRNAs by targeting different steps in the hepatic pathophysiology. Here, we review the function of miRNAs in the context of acute and chronic liver diseases. Furthermore, we highlight the potential role of circulating microRNAs in diagnosis of liver diseases and discuss the major challenges and drawbacks that currently prevent the use of miRNAs in clinical routine.

miR-223 represents a biomarker in acute and chronic liver injury.

BACKGROUND: Dysregulation of miRNAs has been described in tissue and serum from patients with acute and chronic liver diseases. However, only little information on the role of miR-223 in the pathophysiology of acute liver failure (ALF) and liver cirrhosis is available. METHODS: We analysed cell and tissue specific expression levels as well as serum concentrations of miR-223 in mouse models of acute (hepatic ischaemia and reperfusion, single CCl4 injection) and chronic (repetitive CCl4 injection, bile duct ligation (BDL)) liver diseases. Results were validated in patients and correlated with clinical data. The specific hepatic role of miR-223 was analysed by using miR-223-/- mice in these models. RESULTS: miR-223 expression was significantly dysregulated in livers from mice after induction of acute liver injury and liver fibrosis as well as in liver samples from patients with ALF or liver cirrhosis. In acute and chronic models, hepatic miR-223 up-regulation was restricted to hepatocytes and correlated with degree of liver injury and hepatic cell death. Moreover, elevated miR-223 expression was reflected by significantly higher serum levels of miR-223 during acute liver injury. However, functional in vitro and in vivo experiments revealed no differences in the degree of liver cell death and liver fibrosis as miR-223-/- mice behaved identical with wild-type (wt) mice in all tested models. CONCLUSION: miR-223 represents a promising diagnostic marker in a panel of serum markers of liver injury. Together with previously published data, our results highlight that the role of miR-223 in the pathophysiology of the liver is complex and needs further analysis.

Differential Roles of Tumor Necrosis Factor Ligand Superfamily Members as Biomarkers in Pancreatic Cancer.

The tumor necrosis factor⁻related weak inducer of apoptosis (TWEAK) belongs to the tumor necrosis factor ligand superfamily, which was shown to play an important role in inflammatory and malignant gastrointestinal diseases, including colitis or colorectal cancer. However, in contrast to other members of the TNF ligand superfamily, its role as a biomarker in pancreatic cancer is currently unknown. We analyzed serum levels of A proliferation-inducing ligand (APRIL) and TWEAK in 134 patients with pancreatic cancer. Results were compared with 50 healthy controls and correlated with clinical data. Intratumoral expression of APRIL and TWEAK in pancreatic cancer was analysed using the datasets made available by the TCGA-LIHC project. APRIL serum levels were significantly elevated in patients with pancreatic cancer compared to healthy controls, which is in line with previous findings. Notably, the diagnostic accuracy of circulating APRIL levels was similar to CA19-9, an established tumor marker for pancreatic cancer. In contrast, serum concentrations of TWEAK were decreased in pancreatic cancer patients. Interestingly, no differences in TWEAK concentrations became apparent between different clinical subgroups of pancreatic cancer. Moreover, within our cohort of patients, TWEAK levels did not correlate with the patients' prognosis and the diagnostic as well as prognostic potential of TWEAK was lower than CA 19-9, when analyzed in this setting. Finally, using data from the TCGA-LIHC project, we demonstrate that expression levels of TWEAK and APRIL represent prognostic markers for patients' survival according to Kaplan-Meier curve analyses. TWEAK and APRIL serum concentrations are regulated differently in patients with pancreatic cancer, highlighting diverse roles of variant TNF ligands in this type of cancer.

The multikinase inhibitor regorafenib decreases angiogenesis and improves portal hypertension.

BACKGROUND AND AIMS: Angiogenesis is critically involved in the development of liver fibrosis, portal hypertension (PHT) and hepatocellular carcinoma (HCC). Regorafenib is a novel second-line therapy for HCC, but might also be beneficial in fibrosis and PHT even in absence of HCC. This study investigated the effects of regorafenib in experimental models without HCC. METHODS: Fibrosis (in vivo and in vitro), inflammation, liver damage (aminotransferases), angiogenesis (matrigel implantation) and in vivo systemic and portal hemodynamics were assessed in different mouse and rat models (bile duct ligation, CCl4, partial portal vein ligation) after acute and chronic treatment with regorafenib. RESULTS: Long-term treatment with regorafenib improved portal hypertension most likely due to blunted angiogenesis, without affecting fibrosis progression or regression. Interestingly, acute administration of regorafenib also ameliorated portal hemodynamics. Although regorafenib treatment led to hepatotoxic side effects in long-term treated fibrotic animals, in partial portal vein ligated rats, no liver toxicity due to regorafenib was observed. DISCUSSION: Regorafenib might be especially suitable as therapy in patients with PHT and preserved liver function.

Role of circulating microRNAs in liver diseases.

MicroRNAs (miRNAs) are small RNAs regulate gene expression by inhibiting the turnover of their target mRNAs. In the last years, it became apparent that miRNAs are released into the circulation and circulating miRNAs emerged as a new class of biomarkers for various diseases. In this review we summarize available data on the role of circulating miRNAs in the context of acute and chronic liver diseases including hepatocellular and cholangiocellular carcinoma. Data from animal models are compared to human data and current challenges in the field of miRNAs research are discussed.

Elevated Omentin Serum Levels Predict Long-Term Survival in Critically Ill Patients.

Introduction. Omentin, a recently described adipokine, was shown to be involved in the pathophysiology of inflammatory and infectious diseases. However, its role in critical illness and sepsis is currently unknown. Materials and Methods. Omentin serum concentrations were measured in 117 ICU-patients (84 with septic and 33 with nonseptic disease etiology) admitted to the medical ICU. Results were compared with 50 healthy controls. Results. Omentin serum levels of critically ill patients at admission to the ICU or after 72 hours of ICU treatment were similar compared to healthy controls. Moreover, circulating omentin levels were independent of sepsis and etiology of critical illness. Notably, serum concentrations of omentin could not be linked to concentrations of inflammatory cytokines or routinely used sepsis markers. While serum levels of omentin were not predictive for short term survival during ICU treatment, low omentin concentrations were an independent predictor of patients' overall survival. Omentin levels strongly correlated with that of other adipokines (e.g., leptin receptor or adiponectin), which have also been identified as prognostic markers in critical illness. Conclusions. Although circulating omentin levels did not differ between ICU-patients and controls, elevated omentin levels were predictive for an impaired patients' long term survival.