Liver-specific deletion of LASS2 delayed regeneration of mouse liver after partial hepatectomy

Remifentanil preconditioning promotes liver regeneration via upregulation of β-arrestin 2/ERK/cyclin D1 pathway

Remifentanil is a potent, short-acting opioid analgesic drug that can protect tissues from ischemia and reperfusion injury though anti-inflammatory effects. However, the utility of remifentanil in liver regeneration after hepatectomy is not known. Using a 70% hepatectomy mouse model (PHx), we found that preconditioning animals with 4 μg/kg remifentanil enhanced liver regeneration through supporting hepatocyte proliferation but not through anti-inflammatory effects. These effects were also phenocopied in vitro where 40 mM remifentanil promoted the proliferation of primary mouse hepatocyte cultures. We further identified that remifentanil treatment increased the expression of β-arrestin 2 in vivo and in vitro. Demonstrating specificity, remifentanil preconditioning failed to promote liver regeneration in liver-specific β-arrestin 2 knockout (CKO) mice subjected to PHx. While remifentanil increased the expression of activated (phosphorylated)-ERK and cyclin D1 in PHx livers, their levels were not significantly changed in remifentanil-treated CKO mice nor in WT mice pretreated with the ERK inhibitor U0126. Our findings suggest that remifentanil promotes liver regeneration via upregulation of a β-arrestin 2/ERK/cyclin D1 axis, with implications for improving regeneration process after hepatectomy.

Cell Sources and Influencing Factors of Liver Regeneration: A Review

Liver regeneration (LR) is a set of complicated mechanisms between cells and molecules in which the processes of initiation, maintenance, and termination of liver repair are regulated. Although LR has been studied extensively, there are still numerous challenges in gaining its full understanding. Cells for LR have a wide range of sources and the feature of plasticity, and regeneration patterns are not the same under different conditions. Many patients undergoing partial hepatectomy develop cirrhosis or steatosis. The changes of LR in these cases are not clear. Many types of cells participate in LR. Hepatocytes, biliary epithelial cells, hepatic progenitor cells, and human liver stem cells can serve as the cell sources for LR. However, different types and degrees of damage trigger the response from the most suitable cells. Exploring the cell sources of LR is of great significance for accelerating recovery of liver function under different pathological patterns and developing a cell therapy strategy to cope with the shortage of donors for liver transplantation. In clinical practice, the background of the liver influences regeneration. Fibrosis and steatosis create different LR microenvironments and signal molecule interaction patterns. In addition, factors such as partial hepatectomy, aging, platelets, nerves, hormones, bile acids, and gut microbiota are widely involved in this process. Understanding the influencing factors of LR has practical value for individualized treatment of patients with liver diseases. In this review, we have summarized recent studies and proposed our views. We discuss cell sources and the influential factors on LR to help in solving clinical problems.

RNA-seq Used to Explore circRNA Expression and Identify Key circRNAs During the DNA Synthesis Phase of Mice Liver Regeneration

The liver has an excellent capacity for regeneration when faced with external injury and the damage differs from that of other organs in the body. Our aim was to identify the role of circular RNA (circRNA) during the DNA synthesis phase (36 h) of mice liver regeneration. High-throughput RNA sequencing was conducted to explore circRNA and messenger RNA (mRNA) expression in three pairs of mice liver tissue at 0 and 36 h after 2/3 partial hepatectomy. One hundred differentially expressed circRNAs were detected, including 66 upregulated and 34 downregulated circRNAs. We also explored 2483 differentially expressed mRNAs, including 1422 upregulated and 1061 downregulated mRNAs. Gene ontology and Kyoto Encyclopedia of Genes and Genomes indicated that cell cycle regulation, material metabolism, and multiple classical pathways were involved in the DNA synthesis process. A competing endogenous RNA (ceRNA) network containing 5 circRNAs, 28 target genes, and 533 microRNAs (miRNAs) was constructed, and we selected the top 5 miRNAs to map it. Potential key circRNAs were validated with the quantitative real-time PCR technique and their regeneration curves, including consecutive time points, were produced. Finally, a cell counting kit-8 assay on key circRNAs of ceRNA network was performed to further confirm their roles in the DNA synthesis phase of liver regeneration. This study provides a circRNA expression profile for liver regeneration and contributes valuable information for future research.

Liver-specific Sirtuin6 ablation impairs liver regeneration after 2/3 partial hepatectomy

Sirtuin 6 (Sirt6) is an NAD+-dependent deacetylase that regulates central metabolic functions such as glucose homeostasis, fat metabolism, and cell apoptosis. However, the tissue-specific function of Sirt6 in liver regeneration remains unknown. Here, we show that liver-specific Sirt6 knockout (Sirt6LKO) impaired liver reconstitution after 2/3 partial hepatectomy, which was attributed to an alteration of cell cycle progression. Sirt6 LKO delayed hepatocyte transition into S phase during liver regeneration, as shown by the analysis of cell cycle-related proteins and the immuno staining of Ki-67 and 5-bromo-2-deoxyuridine (BrdU). The delayed cell cycle in Sirt6 LKO mice was attributed to the disruption of m-TOR and Akt activity, which is an important pro-proliferation pathway in liver regeneration. Sirt6 LKO also reduced carbon tetrachloride (CCl₄ )-induced liver damage. Our results suggest that Sirt6 LKO impaired liver regeneration via delayed cell cycle and impaired m-TOR and Akt activity.

Roles of Ceramides and Other Sphingolipids in Immune Cell Function and Inflammation

Ceramides are bioactive sphingolipids that support the structure of the plasma membrane and mediate numerous cell-signaling events in eukaryotic cells. The finding that ceramides act as second messengers transducing cellular signals has attracted substantial attention in several fields of Biology. Since all cells contain lipid plasma membranes, the impact of various ceramides, ceramide synthases, ceramide metabolites, and other sphingolipids has been implicated in a vast range of cellular functions including, migration, proliferation, response to external stimuli, and death. The roles of lipids in these functions widely differ among the diverse cell types. Herein, we discuss the roles of ceramides and other sphingolipids in mediating the function of various immune cells; particularly dendritic cells, neutrophils, and macrophages. In addition, we highlight the main studies describing effects of ceramides in inflammation, specifically in various inflammatory settings including insulin resistance, graft-versus-host disease, immune suppression in cancer, multiple sclerosis, and inflammatory bowel disease.

Overexpression of LASS2 inhibits proliferation and causes G0/G1 cell cycle arrest in papillary thyroid cancer

Background

The aim of this study was to investigate the role of LAG1 longevity-assurance homologue 2 (LASS2) in papillary thyroid cancer (PTC).

Methods

Immunohistochemistry staining was conducted to explore the expression levels of LASS2 in PTC tissues and adjacent normal thyroid tissues and nodular goiter tissues. Western blotting and RT-qPCR were performed to explore the expression levels of LASS2 in three PTC cell lines (TPC-1, K1, BCPAP). An Adv-LASS2-GFP recombinant adenovirus vector was constructed and transduced into BCPAP cells. Then CCK-8 assay, colony formation assay, cell cycle distribution, and apoptosis were performed. Western blotting was used to examine the expression of p21, cyclin D1, cyclin-dependent kinase 4, p53 and p-p53.

Results

LASS2 was downregulated in PTC tissues compared with adjacent thyroid tissues or nodular goiter tissues. In addition, the expression of LASS2 was found to be associated with TNM stage and lymph node metastasis. BCPAP cells expressed the lowest LASS2 compared to TPC-1 cells or K1 cells. Overexpression of LASS2 significantly inhibited proliferation, promoted apoptosis and caused G0/G1 cell cycle arrest in BCPAP cells. Furthermore, overexpression of LASS2 significantly increased the expression of p21, inhibited the expression of cyclin D1 and cyclin-dependent kinase 4, and increased the expression of p-p53, but did not effect the expression of p53 in BCPAP cells.

Conclusion

Our findings indicate that overexpression of LASS2 inhibits PTC cell proliferation, promotes apoptosis and causes G0/G1 cell cycle arrest via a p53-dependent pathway. Thus, LASS2 may serve as a novel biomarker in PTC.

LASS2 regulates invasion and chemoresistance via ERK/Drp1 modulated mitochondrial dynamics in bladder cancer cells

Mitochondria coordinated a lot of vital cellular processes of energy production and distribution. Change of mitochondrial functions has been implicated in cancer progression. The present study aims to investigate the involvement of mitochondria dynamics in LASS2 induced invasion and chemoresistance of bladder cancer cells. J82 and BIU87 cell lines were used for LASS2 plasmid transfection while siRNA knockdown was carried out in 5637 cell line. Matrigel invasion assay and Annexin V/PI staining demonstrated that LASS2 negatively regulated cancer cell invasion and chemoresistance. JC-1 staining suggested that LASS2 overexpression downregulated mitochondrial membrane potential. Mitotracker staining showed that LASS2 induced mitochondrial fusion and inhibited mitochondrial fission. In addition, LASS2 overexpression downregulated expression of mitochondrial fission protein p-Drp1 Drp1 and Fis1. While depletion of LASS2 exhibited the opposite effects. Drp1 inhibitor Mdivi abolished invasion and chemoresistance induced by LASS2 siRNA. Furthermore, we found that LASS2 overexpression could inhibit phosphorylation of ERK, which act upstream of Drp1. ERK inhibitor PD98059 suppressed Drp1 phosphorylation and abrogated the effects of LASS2 depletion. In conclusion, the present study demonstrated that LASS2 inhibits bladder cancer invasion and chemoresistance through regulation of ERK-Drp1 induced mitochondrial dynamics.