Impaired liver regeneration is associated with reduced cyclin B1 in natural killer T cell-deficient mice

Liver Regeneration in Chronic Liver Injuries: Basic and Clinical Applications Focusing on Macrophages and Natural Killer Cells

BACKGROUND & AIMS

Liver regeneration is a necessary but complex process involving multiple cell types besides hepatocytes. Mechanisms underlying liver regeneration after partial hepatectomy and acute liver injury have been well-described. However, in patients with chronic and severe liver injury, the remnant liver cannot completely restore the liver mass and function, thereby involving liver progenitor-like cells (LPLCs) and various immune cells.

RESULTS

Macrophages are beneficial to LPLCs proliferation and the differentiation of LPLCs to hepatocytes. Also, cells expressing natural killer (NK) cell markers have been studied in promoting both liver injury and liver regeneration. NK cells can promote LPLC-induced liver regeneration, but the excessive activation of hepatic NK cells may lead to high serum levels of interferon-γ, thus inhibiting liver regeneration.

CONCLUSIONS

This review summarizes the recent research on 2 important innate immune cells, macrophages and NK cells, in LPLC-induced liver regeneration and the mechanisms of liver regeneration during chronic liver injury, as well as the latest macrophage- and NK cell-based therapies for chronic liver injury. These novel findings can further help identify new treatments for chronic liver injury, saving patients from the pain of liver transplantations.

Natural Killer T Cells in Various Mouse Models of Hepatitis

Natural killer T (NKT) cells are a key component of innate immunity. Importantly, a growing body of evidence indicates that NKT cells play an integral role in various acute and chronic liver injuries. NKT cells participate in the progression of an injury through the secretion of cytokines, which promote neutrophil infiltration and enhance Fas ligand (FasL) and granzyme-mediated NKT cytotoxic activity. Therefore, examining the role of NKT cells in hepatic disease is critical for a comprehensive understanding of disease pathogenesis and may provide insight into novel approaches for treatment. For more than a century, mouse models that imitate the physiopathological conditions of human disease have served as a critical tool in biological and medical basic research, including studies of liver disease. Here, we review the role of NKT cells in various mouse models of hepatitis.

The assembly of glycosphingolipid determines their immunomodulatory effect: A novel method for structure-based design of immunotherapy

Structure-activity relationships provide insight into the binding interactions of beta-glycosphingolipids (GSLs) with both the TCR and the CD1d molecules, as well as the subsequent immunologic response of regulatory NKT cells.

AIM

To determine the effects of synthetic GSL structures on their immune modulatory functions.

METHODS

GSLs of various structures were tested in vitro and in an animal model of Concanavalin A (ConA) immune-mediated hepatitis.

RESULTS

In vitro, using SV40 binding to live monkey CV1 cells, the l-threo stereoisomer of C8-β-LacCer inhibits caveolar internalization, reducing viral binding to the cell surface. In vivo, in the ConA model, LR172, which has a saturated C8 chain, and LR178, which has a trans double bond at C-2 in the C8 chain, suppressed the immune-mediated liver inflammation and reduced IFNγ levels in a dose dependent manner. The beneficial effects of LR172 and of LR178 are associated with suppression of liver apoptosis, increased phosphorylated STAT3 expression in the liver, and an increase in the NKT liver/spleen ratio.

SUMMARY

The assembly of GSLs determines their immunomodulatory effect and can serve as a method for structure-based design of immunotherapy.

Tissue-specific functions of invariant natural killer T cells

Invariant natural killer T cells (iNKT cells) are an innate-like T cell subset that expresses an invariant T cell receptor (TCR) α-chain and recognizes lipids presented on CD1d. They secrete diverse cytokines and can influence many types of immune responses. Despite having highly similar TCR specificities, iNKT cells differentiate in the thymus into distinct subsets that are analogous to T helper 1 (T_H1), T_H2 and T_H17 cell subsets. Additional iNKT cell subsets that may require peripheral activation have also been described, including one that produces IL-10. In general, iNKT cells are non-circulating, tissue-resident lymphocytes, but the prevalence of different iNKT cell subsets differs markedly between tissues. Here, we summarize the functions of iNKT cells in four tissues in which they are prevalent, namely, the liver, the lungs, adipose tissue and the intestine. Importantly, we explain how local iNKT cell responses at each site contribute to tissue homeostasis and protection from infection but can also contribute to tissue inflammation and damage.

Intrahepatic T-Cell Receptor β Immune Repertoire Is Essential for Liver Regeneration

T lymphocytes synergize with the cellular immune system to promote hepatocyte regeneration. The T-cell receptor (TCR) immune repertoire is closely associated with the host immune response and regenerative proliferation. High-throughput sequencing of TCR provides deep insight into monitoring the immune microenvironment. Here, we aimed to determine the role of the TCRβ immune repertoire in liver regeneration (LR). We investigated hepatic regeneration in TCRβ chain-deficient (tcrb^-/- ) mice by two-thirds partial hepatectomy (PHx) method. Our results demonstrated that tcrb^-/- mice revealed a reduced capacity for LR, which was characterized by impaired hepatocyte proliferation and enhanced hepatocyte apoptosis. Dysregulation of inflammatory signaling activation and inflammatory factors was observed in regenerated tcrb^-/- livers. Simultaneously, significantly altered immunocyte levels and aberrant cytokine levels were observed during hepatic regeneration. In addition, we first determined the profile of the TCRβ immune repertoire during LR, indicating that PHx resulted in remarkably lower TCRβ diversity in intrahepatic T lymphocytes. Conclusion: Taken together, our data suggest that TCRβ deficiency gives a rise to aberrant intrahepatic immune microenvironment that impairs LR, and the TCRβ reconstitution is required for hepatic immunocyte recruitment and activation during LR.

miR-155 accelerates proliferation of mouse hepatocytes during liver regeneration by directly targeting SOCS1

Liver regeneration after two-thirds partial hepatectomy (PH) is a clinically significant repair process for restoring proper liver architecture. Although microRNA-155 (miR-155) has been found to serve as a crucial microRNA regulator that controls liver cell function and proliferation, little is known about its specific role in the regenerating liver. Using a mouse model with miR-155 overexpression or miR-155 knockout, we investigated the molecular mechanisms of miR-155 in liver regeneration. We found a marked induction of miR-155 in C57BL/6 mice after PH. Furthermore, RL-m155 mice showed enhanced liver regeneration as a result of accelerated progression of hepatocytes into the cell cycle, mainly through an increase in cyclin levels. However, proliferation of hepatocytes was delayed in miR-155-deficient livers. Expression of suppressor of cytokine signaling 1 (SOCS1) was dramatically downregulated in the process of liver regeneration, and enhancement of SOCS1 contributed to impaired proliferation of hepatocytes. Additionally, in vitro and in vivo experiments showed that adenovirus- or adeno-associated virus-mediated overexpression of SOCS1 attenuated improved liver regeneration induced by miR-155 overexpression. Our study shows that miR-155 is a pro-proliferative regulator in liver regeneration by facilitating the cell cycle and directly targeting SOCS1. NEW & NOTEWORTHY Our findings suggest a microRNA-155 (miR-155)-mediated positive regulation pattern in liver regeneration. A series of in vivo and in vitro studies showed that miR-155 upregulation enhanced partial hepatectomy-induced proliferation of hepatocytes by promoting the cell cycle without inducing DNA damage or apoptosis. Suppressor of cytokine signaling 1, a target gene of miR-155, antagonized the proliferation-promoting effect of miR-155. Therefore, pharmacological intervention targeting miR-155 may be therapeutically beneficial in various liver diseases.

Lumbrokinase/paclitaxel nanoparticle complex: potential therapeutic applications in bladder cancer

Background

Lumbrokinase (LK) is an enzyme complex with antithrombotic, antioxidant, antitumor, and immunomodulatory effects. It has been extensively studied and used in clinical anti-tumor therapy. However, its half-life is short, its bioavailability is low, and its toxicity and side effects are great, which greatly limit its clinical application. Therefore, LK is often combined with other drugs (such as immune agents, hormones, or Chinese herbal medicine) to reduce its dosage and side effects and to improve its anti-tumor effects.

Methods and results

Here, we described an LK/paclitaxel (PTX) nanocarrier based on poly(ethylene glycol)-b-(poly(ethylenediamine l-glutamate)-g-poly(ε-benzyoxycarbonyl-l-lysine)-r-poly(l-lysine)) (PEG-b-(PELG-g-(PZLL-r-PLL))). In the present study, LK and PTX were loaded by electrostatic and/or hydrophobic effects under mild conditions, thereby increasing the half-life and bioavailability of the drugs via the sustained release and enhancement of tumor site enrichment by the LK/PTX/PEG-b-(PELG-g-(PZLL-r-PLL)) complex through passive targeting. In this study, using bladder cancer cells (J82 cells) and rat bladder cancer model as the object, the structure of the nanocarrier, the relationship between drugs composition and antitumor properties were systematically studied.

Conclusion

We propose that the block copolymer PEG-b-(PELG-g-(PZLL-r-PLL)) may function as a potent nanocarrier for augmenting anti-bladder cancer pharmacotherapy, with unprecedented clinical benefits.