Endogenous Interleukin 18 Suppresses Liver Regeneration After Hepatectomy in Mice

Molecular Pathways Governing the Termination of Liver Regeneration

The liver has the unique capacity to regenerate, and up to 70% of the liver can be removed without detrimental consequences to the organism. Liver regeneration is a complex process involving multiple signaling networks and organs. Liver regeneration proceeds through three phases: the initiation phase, the growth phase, and the termination phase. Termination of liver regeneration occurs when the liver reaches a liver-to-body weight that is required for homeostasis, the so-called "hepatostat." The initiation and growth phases have been the subject of many studies. The molecular pathways that govern the termination phase, however, remain to be fully elucidated. This review summarizes the pathways and molecules that signal the cessation of liver regrowth after partial hepatectomy and answers the question, "What factors drive the hepatostat?" SIGNIFICANCE STATEMENT: Unraveling the pathways underlying the cessation of liver regeneration enables the identification of druggable targets that will allow us to gain pharmacological control over liver regeneration. For these purposes, it would be useful to understand why the regenerative capacity of the liver is hampered under certain pathological circumstances so as to artificially modulate the regenerative processes (e.g., by blocking the cessation pathways) to improve clinical outcomes and safeguard the patient's life.

Unveiling the power of microenvironment in liver regeneration: an in-depth overview

The liver serves as a vital regulatory hub for various physiological processes, including sugar, protein, and fat metabolism, coagulation regulation, immune system maintenance, hormone inactivation, urea metabolism, and water-electrolyte acid-base balance control. These functions rely on coordinated communication among different liver cell types, particularly within the liver's fundamental hepatic lobular structure. In the early stages of liver development, diverse liver cells differentiate from stem cells in a carefully orchestrated manner. Despite its susceptibility to damage, the liver possesses a remarkable regenerative capacity, with the hepatic lobule serving as a secure environment for cell division and proliferation during liver regeneration. This regenerative process depends on a complex microenvironment, involving liver resident cells, circulating cells, secreted cytokines, extracellular matrix, and biological forces. While hepatocytes proliferate under varying injury conditions, their sources may vary. It is well-established that hepatocytes with regenerative potential are distributed throughout the hepatic lobules. However, a comprehensive spatiotemporal model of liver regeneration remains elusive, despite recent advancements in genomics, lineage tracing, and microscopic imaging. This review summarizes the spatial distribution of cell gene expression within the regenerative microenvironment and its impact on liver regeneration patterns. It offers valuable insights into understanding the complex process of liver regeneration.

The pharmacology and mechanisms of traditional Chinese medicine in promoting liver regeneration: A new therapeutic option

BACKGROUND

The liver is renowned for its remarkable regenerative capacity to restore its structure, size and function after various types of liver injury. However, in patients with end-stage liver disease, the regenerative capacity is inhibited and liver transplantation is the only option. Considering the limitations of liver transplantation, promoting liver regeneration is suggested as a new therapeutic strategy for liver disease. Traditional Chinese medicine (TCM) has a long history of preventing and treating various liver diseases, and some of them have been proven to be effective in promoting liver regeneration, suggesting the therapeutic potential in liver diseases.

PURPOSE

This review aims to summarize the molecular mechanisms of liver regeneration and the pro-regenerative activity and mechanism of TCM formulas, extracts and active ingredients.

METHODS

We conducted a systematic search in PubMed, Web of Science and the Cochrane Library databases using "TCM", "liver regeneration" or their synonyms as keywords, and classified and summarized the retrieved literature. The PRISMA guidelines were followed.

RESULTS

Forty-one research articles met the themes of this review and previous critical studies were also reviewed to provide essential background information. Current evidences indicate that various TCM formulas, extracts and active ingredients have the effect on stimulating liver regeneration through modulating JAK/STAT, Hippo, PI3K/Akt and other signaling pathways. Besides, the mechanisms of liver regeneration, the limitation of existing studies and the application prospect of TCM to promote liver regeneration are also outlined and discussed in this review.

CONCLUSION

This review supports TCM as new potential therapeutic options for promoting liver regeneration and repair of the failing liver, although extensive pharmacokinetic and toxicological studies, as well as elaborate clinical trials, are still needed to demonstrate safety and efficacy.

Gasdermin D-mediated pyroptosis suppresses liver regeneration after 70% partial hepatectomy

Pyroptosis is a kind of programmed cell death primarily mediated by gasdermin D (GSDMD) and shown to regulate multiple diseases. However, its contribution to liver regeneration, a fine‐tuned tissue repair process mediated primarily by hepatocytes after mass loss, remains unclear. Herein, we found that caspase‐11/GSDMD‐mediated pyroptosis was activated in regenerating liver after 70% partial hepatectomy. Impeding pyroptosis by deleting GSDMD significantly reduced liver injury and accelerated liver regeneration. Mechanistically, GSDMD deficiency up‐regulates the activation of hepatocyte growth factor/c‐Met and epidermal growth factor receptor mitogenic pathways at the initiation phase. Moreover, activin A and glypican 3 (GPC3), two terminators of liver regeneration, were inhibited when GSDMD was absent. In vitro study suggested the expressions of activin A and GPC3 were induced by interleukin (IL)–1β and IL‐18, whose maturations were regulated by GSDMD‐mediated pyroptosis. Similarly, pharmacologically inhibiting GSDMD recapitulates these phenomena. Conclusion: This study characterizes the role of GSDMD‐mediated pyroptosis in liver regeneration and lays the foundation for enhancing liver restoration by targeting GSDMD in liver patients with impaired regenerative capacity.

Cytokines in Liver Transplantation

Cytokines, soluble mediators of the immune system, play a critical role in the pathogenesis of autoimmune, allergic and infectious diseases. They are also implicated in the initiation and development of allograft rejection. During recent years, there have been considerable advances in generating novel anti-cytokine agents with promoted efficacy and safety, which could be administrated for managing dysregulated cytokine secretion; besides, gene therapy for overexpression of immunomodulatory cytokines has shown substantial improvements. Liver transplantation has been established as a life-saving treatment for end-stage hepatic diseases but the growing number of recipients urge for improved post-transplant care including tolerance induction, infection control and resolving immunosuppressant drugs adverse effects. Cytokines with a wide range of proinflammatory and regulatory properties might be considered as potential therapeutic targets for selective suppression or enhancement of the immune responses in recipients. In the present review, we aimed to summarize the positive and negative effects of cytokines on liver allograft in addition to their prognostic and therapeutic values.

Anti-hepatic fibrosis effects of AD-2 affecting the Raf-MEK signaling pathway and inflammatory factors in thioacetamide-induced liver injury

25-Hydroxylprotopanaxadiol-3β, 12β, 20-triol (25-OH-PPD or AD-2) belongs to dammarane ginsenoside, and is commonly obtained from the acidic hydrolysate of total ginsensides of Panax ginseng. This study investigated the potential mechanism of AD-2 toward improving thioacetamide (TAA)-induced hepatic fibrosis in mice. Mice were divided into seven groups: control group, TAA model group, TAA + AD-2 (5, 10, and 20 mg/kg) groups, TAA + silymarin (100 mg/kg) group, and TAA + Fu Fang Biejia (FFBj; 300 mg/kg) group. All mice were treated to intraperitoneal TAA injection to establish a hepatic fibrosis model, and drugs were administered orally. The mechanism and related pathways underlying the AD-2-mediated action against hepatic fibrosis were explored by Western blotting and immunohistochemical staining. After AD-2 treatment, the expression levels of Lipin-1, SREBP1, and F4/80 significantly decreased, meanwhile the protein expressions levels of IL1β, IL1R1, IL18, Bax, Bid, Bcl-2, and cFlips also decreased. Furthermore, AD-2 inhibited RAF and MEK pathways. The results demonstrate that AD-2 can alleviate hepatic fibrosis. The mechanism is likely related to the regulation of lipid accumulation, inflammatory response, apoptosis pathway, and Raf-MEK signaling pathways, which provide a basis for clinical research for the treatment of hepatic fibrosis. PRACTICAL APPLICATION: Ginsenoside is one of the main active ingredients of ginseng, and can alleviate the symptoms of various diseases, for example, hepatic fibrosis. This paper mainly used Western blotting to explore its possible mechanism of action. The goal was to provide a reference for the development of traditional Chinese medicines for hepatic fibrosis.