Sanchari Roy

Circulating MicroRNAs as Biomarkers for Sepsis

Sepsis represents a major cause of lethality during intensive care unit (ICU) treatment. Pharmacological treatment strategies for sepsis are still limited and mainly based on the early initiation of antibiotic and supportive treatment. In this context, numerous clinical and serum based markers have been evaluated for the diagnosis, the severity, and the etiology of sepsis. However until now, few of these factors could be translated into clinical use. MicroRNAs (miRNAs) do not encode for proteins but regulate gene expression by inhibiting the translation or transcription of their target mRNAs. Recently it was demonstrated that miRNAs are released into the circulation and that the spectrum of circulating miRNAs might be altered during various pathologic conditions, such as inflammation, infection, and sepsis. By using array- and single PCR-based methods, a variety of deregulated miRNAs, including miR-25, miR-133a, miR-146, miR-150, and miR-223, were described in the context of sepsis. Some of the miRNAs correlated with the disease stage, as well as patients’ short and long term prognosis. Here, we summarize the current findings on the role of circulating miRNAs in the diagnosis and staging of sepsis in critically ill patients. We compare data from patients with findings from animal models and, finally, highlight the challenges and drawbacks that currently prevent the use of circulating miRNAs as biomarkers in clinical routine.

miR-30c and miR-193 are a part of the TGF-β-dependent regulatory network controlling extracellular matrix genes in liver fibrosis.

MicroRNAs (miRNAs) have recently emerged as novel regulators in liver fibrosis. miR‐30c and miR‐193 are involved in fibrotic remodeling processes and cancer development, respectively. This study aimed to explore the role of miR‐30c and miR‐193 in liver fibrosis.

The role of miRNAs in the regulation of inflammatory processes during hepatofibrogenesis

Liver cirrhosis represents the end stage of most chronic inflammatory liver diseases and is a major global health burden. Despite the enormous relevance of cirrhotic disease, pharmacological strategies for prevention or treatment of hepatic fibrosis are still limited, underlining the need to establish a better understanding of the molecular mechanisms underlying the pathogenesis of hepatic cirrhosis. Recently, miRNAs have emerged as a new class of RNAs that do not withhold the information to encode for proteins but regulate whole gene expression networks during different physiological and pathological processes. Various authors demonstrated that miRNA species are functionally involved in the regulation of chronic liver damage and development of liver cirrhosis in inflamed livers. Moreover, circulating miRNA patterns were suggested to serve as blood-based biomarkers indicating liver injury and progression to hepatic cirrhosis and cancer. Here we summarize current findings on a potential role of miRNAs in the cascade leading from liver inflammation to liver fibrosis and finally hepatocellular carcinoma. We compare data from animal models with findings on miRNAs dysregulated in human patients and finally highlight a potential use of miRNAs as biomarkers for liver injury, fibrosis and cancer.

RIPK1 Suppresses a TRAF2-Dependent Pathway to Liver Cancer

Receptor-interacting protein kinase 1 (RIPK1) represents an essential signaling node in cell death and inflammation. Ablation of Ripk1 in liver parenchymal cells (LPC) did not cause a spontaneous phenotype, but led to tumor necrosis factor (TNF)-dependent hepatocyte apoptosis and liver injury without affecting inducible nuclear factor κB (NF-κB) activation. Loss of Ripk1 induced the TNF-dependent proteasomal degradation of the E3-ligase, TNF receptor-associated factor 2 (TRAF2), in a kinase-independent manner, thereby activating caspase-8. Moreover, loss of both Ripk1 and Traf2 in LPC not only resulted in caspase-8 hyperactivation but also impaired NF-κB activation, promoting the spontaneous development of hepatocellular carcinoma. In line, low RIPK1 and TRAF2 expression in human HCCs was associated with an unfavorable prognosis, suggesting that RIPK1 collaborates with TRAF2 to inhibit murine and human hepatocarcinogenesis.

The necroptosis-inducing kinase RIPK3 dampens adipose tissue inflammation and glucose intolerance.

Receptor-interacting protein kinase 3 (RIPK3) mediates necroptosis, a form of programmed cell death that promotes inflammation in various pathological conditions, suggesting that it might be a privileged pharmacological target. However, its function in glucose homeostasis and obesity has been unknown. Here we show that RIPK3 is over expressed in the white adipose tissue (WAT) of obese mice fed with a choline-deficient high-fat diet. Genetic inactivation of Ripk3 promotes increased Caspase-8-dependent adipocyte apoptosis and WAT inflammation, associated with impaired insulin signalling in WAT as the basis for glucose intolerance. Similarly to mice, in visceral WAT of obese humans, RIPK3 is overexpressed and correlates with the body mass index and metabolic serum markers. Together, these findings provide evidence that RIPK3 in WAT maintains tissue homeostasis and suppresses inflammation and adipocyte apoptosis, suggesting that systemic targeting of necroptosis might be associated with the risk of promoting insulin resistance in obese patients.

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.

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.

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.

Elevated serum levels of bone sialoprotein during ICU treatment predict long-term mortality in critically ill patients

Bone sialoprotein (BSP), a member of the SIBLINGs (for Small Integrin-Binding LIgand, N-linked Glycoproteins) family, has recently be associated to inflammatory and infectious diseases. We therefore measured BSP concentrations in 136 patients at admission to the intensive care unit (ICU) and 3 days of ICU. BSP levels were compared to 36 healthy blood donors and correlated to clinical data. In these analysis, BSP serum levels were strongly elevated at the time point of admission to the ICU when compared to healthy controls. Moreover BSP concentrations were significantly elevated after 3 days of treatment on the intensive care unit. A further increase in BSP levels was detected in patients with higher APACHE-II-scores and in patients with septic disease. While in most patients, BSP levels decreased during the first three days of treatment on a medical ICU, patients with persistently elevated BSP levels displayed an unfavorable outcome. In these patients, persistently elevated BSP concentrations were a superior predictor of mortality than established indicators of patient´ prognosis such as the SAPS2 or the APACHE-II score. In summary, our data argue for a novel utility for BSP as a biomarker in patients treated on a medical ICU.

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.