SYK-3BP2 Pathway Activity in Parenchymal and Myeloid Cells Is a Key Pathogenic Factor in Metabolic Steatohepatitis

SYK promotes the formation of neutrophil extracellular traps by inducing PKM2 nuclear translocation and promoting STAT3 phosphorylation to exacerbate hepatic ischemia-reperfusion injury and tumor recurrence

BACKGROUND

At present, hepatic ischemia-reperfusion injury (IRI) is an important complication of partial hepatectomy and liver transplantation, and it is an important cause of poor prognosis. Spleen tyrosine kinase(SYK) plays an important role in a variety of signaling pathways in the liver, but its role in hepatic IRI is still unclear. This study aims to investigate the role and mechanism of SYK in hepatic IRI and tumor recurrence.

METHODS

We first observed the activation of SYK in the liver of mice in response to hepatic IRI. Subsequently, Pharmacological inhibitions of SYK were used to evaluated the effect of SYK on neutrophil recruitment and NETosis, and further explored the effect of SYK on IRI and tumor recurrence.

RESULTS

Our study shows that SYK is activated in response to hepatic IRI and aggravates liver injury. On the one hand, neutrophils SYK during the early stage of liver reperfusion increases neutrophil extracellular traps (NETs) production by promoting Pyruvate kinase M2(PKM2) nuclear translocation leading to upregulation of phosphorylated STAT3, thereby exacerbating liver inflammation and tumor recurrence. On the other hand, macrophages SYK can promote the recruitment of neutrophils and increase the activation of NLRP3 inflammasome and IL1β, which further promotes the formation of NETs.

CONCLUSIONS

Our study demonstrates that neutrophil and macrophage SYK synergistically promote hepatic IRI and tumor recurrence, and SYK may be a potential target to improve postoperative hepatic IRI and tumor recurrence.

Exploring Key Genes with Diagnostic Value for Nonalcoholic Steatohepatitis Based on Bioinformatics Analysis

We aimed to screen specific genes in liver tissue samples of patients with nonalcoholic steatohepatitis (NASH) with clinical diagnostic value based on bioinformatics analysis. The datasets of liver tissue samples from healthy individuals and NASH patients were retrieved for consistency cluster analysis to obtain the NASH sample typing, followed by verification of the diagnostic value of sample genotyping-specific genes. All samples were subjected to logistic regression analysis, followed by the establishment of the risk model, and then, the diagnostic value was determined by receiver operating characteristic curve analysis. NASH samples could be divided into cluster 1, cluster 2, and cluster 3, which could predict the nonalcoholic fatty liver disease activity score of patients. A total of 162 sample genotyping-specific genes were extracted from patient clinical parameters, and the top 20 core genes in the protein interaction network were obtained for logistic regression analysis. Five sample genotyping-specific genes (WD repeat and HMG-box DNA-binding protein 1 [WDHD1], GINS complex subunit 2 [GINS2], replication factor C subunit 3 (RFC3), secreted phosphoprotein 1 [SPP1], and spleen tyrosine kinase [SYK]) were extracted to construct the risk models with high diagnostic value in NASH. Compared with the low-risk group, the high-risk group of the model showed increased lipoproduction and decreased lipolysis and lipid β oxidation. The risk models based on WDHD1, GINS2, RFC3, SPP1, and SYK have high diagnostic value in NASH, and this risk model is closely related to lipid metabolism pathways.

PARsylation-mediated ubiquitylation: lessons from rare hereditary disease Cherubism

Modification of proteins by ADP-ribose (PARsylation) is catalyzed by the poly(ADP-ribose) polymerase (PARP) family of enzymes exemplified by PARP1, which controls chromatin organization and DNA repair. Additionally, PARsylation induces ubiquitylation and proteasomal degradation of its substrates because PARsylation creates a recognition site for E3-ubiquitin ligase. The steady-state levels of the adaptor protein SH3-domain binding protein 2 (3BP2) is negatively regulated by tankyrase (PARP5), which coordinates ubiquitylation of 3BP2 by the E3-ligase ring finger protein 146 (RNF146). 3BP2 missense mutations uncouple 3BP2 from tankyrase-mediated negative regulation and cause Cherubism, an autosomal dominant autoinflammatory disorder associated with craniofacial dysmorphia. In this review, we summarize the diverse biological processes, including bone dynamics, metabolism, and Toll-like receptor (TLR) signaling controlled by tankyrase-mediated PARsylation of 3BP2, and highlight the therapeutic potential of this pathway.

Immune cells and their derived microRNA-enriched extracellular vesicles in nonalcoholic fatty liver diseases: Novel therapeutic targets

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. Despite extensive research and multiple clinical trials, there are still no FDA-approved therapies to treat the most severe forms of NAFLD. This is largely due to its complicated etiology and pathogenesis, which involves visceral obesity, insulin resistance, gut dysbiosis, etc. Although inflammation is generally believed to be one of the critical factors that drive the progression of simple steatosis to nonalcoholic steatohepatitis (NASH), the exact type of inflammation and how it contributes to NASH pathogenesis remain largely unknown. Liver inflammation is accompanied by the elevation of inflammatory mediators, including cytokines and chemokines and consequently intrahepatic infiltration of multiple types of immune cells. Recent studies revealed that extracellular vesicles (EVs) derived from inflammatory cells and hepatocytes play an important role in controlling liver inflammation during NASH. In this review, we highlight the roles of innate and adaptive immune cells and their microRNA-enriched EVs during NAFLD development and discuss potential drugs that target inflammatory pathways for the treatment of NAFLD.

The spleen tyrosine kinase (SYK): A crucial therapeutic target for diverse liver diseases

Spleen tyrosine kinase (SYK) is an enigmatic protein tyrosine kinase, and involved in signal transduction related with lots of cellular processes. It's highly expressed in the cells of hematopoietic origin and acts as an important therapeutic target in the treatment of autoimmune diseases and allergic disorders. In recent years, more and more evidences indicate that SYK is expressed in non-hematopoietic cells and effectively regulates various non-immune biological responses as well. In this review, we mainly summary the role of SYK in different liver diseases. Robust SYK expression has been discovered in hepatocytes, hepatic stellate cells, as well as Kupffer cells, which participates in the regulation of numerous signal transduction in various liver diseases (e.g. hepatitis, liver fibrosis and hepatocellular carcinoma). In addition, the blockage of SYK activity using small molecule modulators is considered as a significant therapeutic strategy against liver diseases, and both hepatic SYK and non-hepatic SYK could become highly promising therapeutic targets. Totally, even though some critical points about the significance of SYK in liver diseases treatment still need further elaboration, more reliable biotechnical or pharmacological therapy modes will be established based on the better understanding of the relationship between SYK and liver diseases.

Metabolic Fatty Liver Disease in Children: A Growing Public Health Problem

Metabolic-associated fatty liver disease (MAFLD), previously called nonalcoholic fatty liver diseases (NAFLD), is one of the most important causes of chronic liver disease worldwide and will likely become the leading cause of end-stage liver disease in the decades ahead. MAFLD covers a continuum of liver diseases from fatty liver to nonalcoholic steatohepatitis (NASH), liver fibrosis/cirrhosis and hepatocellular cancer. Importantly, the growing incidence of overweight and obesity in childhood, 4% in 1975 to 18% in 2016, with persisting obesity complications into adulthood, is likely to be harmful by increasing the incidence of severe MAFLD at an earlier age. Currently, MAFLD is the leading form of chronic liver disease in children and adolescents, with a global prevalence of 3 to 10%, pointing out that early diagnosis is therefore crucial. In this review, we highlight the current knowledge concerning the epidemiology, risk factors and potential pathogenic mechanisms, as well as diagnostic and therapeutic approaches, of pediatric MAFLD.