LECT2: A pleiotropic and promising hepatokine, from bench to bedside

Updates on the role of leukocyte cell-derived chemotaxin-2 in inflammation regulation and immunomodulation

Leukocyte cell-derived chemotaxin-2 (LECT2), originally identified as a novel neutrophil chemokine, is a multifunctional secreted factor primarily produced in hepatocytes. However, many studies have shown that LECT2 is a pleiotropic protein that not only exerts chemotaxis properties as a cytokine but also plays an important role in inflammatory regulation and immune regulation. Pathogens such as bacteria and the role of the host immune system are key factors in the inflammatory response. In antibacterial, LECT2 can directly destroy bacterial structure or affect the normal metabolism of bacteria to inactivate bacteria and can also achieve this effect by activating immune cells and regulating cytokines. In immunomodulation, LECT2 has neutrophil chemotactic activity and regulates the quantities of Natural killer T (NKT) cells, regulatory T cells, monocytes/macrophages, granulocytes, and/or the expression of associated cytokines, thereby influencing their effect in immune reaction. Inflammation and immune regulation are closely related to a variety of diseases, such as bacterial infection, liver cirrhosis, dermatitis, coronary atherosclerotic heart disease, and so on. This review summarizes the basic and clinical studies of LECT2 in antibacterial effects and its effects on immune cells to explore the mechanism of LECT in inflammatory regulation and immune regulation in physiological and pathological conditions better.

Global research trends and hotspots for leukocyte cell-derived chemotaxin-2 from the past to 2023: a combined bibliometric review

Leukocyte cell-derived chemotaxin-2 (LECT2) is an important cytokine synthesized by liver. Significant research interest is stimulated by its crucial involvement in inflammatory response, immune regulation, disease occurrence and development. However, bibliometric study on LECT2 is lacking. In order to comprehend the function and operation of LECT2 in human illnesses, we examined pertinent studies on LECT2 investigation in the Web of Science database, followed by utilizing CiteSpace, VOSview, and Scimago Graphica for assessing the yearly quantity of papers, countries/regions involved, establishments, authors, publications, citations, and key terms. Then we summarized the current research hotspots in this field. Our study found that the literature related to LECT2 has a fluctuating upward trend. "Angiogenesis", "ALECT2", "diagnosis", and "biliary atresia" are the current investigative frontiers. Our findings indicated that liver diseases (e.g. liver fibrosis and hepatic cell carcinoma), systemic inflammatory disease, and amyloidosis are the current research focus of LECT2. The current LECT2 research outcomes are not exceptional. We hope to promote the scientific research of LECT2 and exploit its potential for clinical diagnosis and treatment of related diseases through a comprehensive bibliometric review.

Elevated serum levels of leukocyte cell-derived chemotaxin 2 are associated with the prevalence of metabolic syndrome

AIMS

Inflammation is central to the pathogenesis of metabolic syndrome (MetS). Leukocyte cell-derived chemotaxin 2 (LECT2) is constitutively secreted in response to inflammatory stimuli and oxidative stress contributing to tissue or systemic inflammation. We explored the relationship between LECT2 levels and MetS severity in humans and mice.

METHODS

Serum LECT2 levels were measured in 210 participants with MetS and 114 without MetS (non-MetS). LECT2 expression in the liver and adipose tissue was also examined in mice fed a high-fat diet (HFD) and genetically obese (ob/ob) mice.

RESULTS

Serum LECT2 levels were significantly higher in MetS participants than in non-MetS participants (7.47[3.36-17.14] vs. 3.74[2.61-5.82], P < 0.001). Particularly, serum LECT2 levels were significantly elevated in participants with hypertension, central obesity, diabetes mellitus (DM), hyperglycaemia, elevated triglyceride (TG) levels, and reduced high-density lipoprotein cholesterol (HDL-C) levels compared to those in participants without these conditions. Pearson's correlation analysis showed that serum LECT2 levels were positively associated with conventional risk factors in all patients. Moreover, LECT2 was positively associated with the number of MetS components (r = 0.355, P < 0.001), indicating that higher serum LECT2 levels reflected MetS severity. Multivariate regression analysis revealed that a one standard deviation increase in LECT2 was associated with an odds ratio of 1.52 (1.01-2.29, P = 0.044) for MetS prevalence after adjusting for age, sex, body mass index, waist circumference, smoking status, white blood cell count, fasting blood glucose, TG, total cholesterol, HDL-C, blood urea nitrogen, and alanine aminotransferase. Receiver operating characteristic curve analysis confirmed the strong predictive ability of serum LECT2 levels for MetS. The optimum serum LECT2 cut-off value was 9.05. The area under the curve was 0.73 (95% confidence interval 0.68-0.78, P < 0.001), with a sensitivity and specificity of 45.71% and 95.61%, respectively. Additionally, LECT2 expression levels were higher at baseline and dramatically enhanced in metabolic organs (e.g. the liver) and adipose tissue in HFD-induced obese mice and ob/ob mice.

CONCLUSIONS

Increased LECT2 levels were significantly and independently associated with the presence and severity of MetS, indicating that LECT2 could be used as a novel biomarker and clinical predictor of MetS.

Elucidation of pericholangitis and periductal fibrosis in cholestatic liver diseases via extracellular vesicles released by polarized biliary epithelial cells

Cholestatic liver diseases causes inflammation and fibrosis around bile ducts. However, the pathological mechanism has not been elucidated. Extracellular vesicles (EVs) are released from both the basolateral and apical sides of polarized biliary epithelial cells. We aimed to investigate the possibility that EVs released from the basolateral sides of biliary epithelial cells by bile acid stimulation induce inflammatory cells and fibrosis around bile ducts, and they may be involved in the pathogenesis of cholestatic liver disease. Human biliary epithelial cells (H69) were grown on cell culture inserts and stimulated with chenodeoxycholic acid + IFN-γ. Human THP-1-derived M1-macrophages, LX-2 cells, and KMST-6 cells were treated with the extracted basolateral EVs, and inflammatory cytokines and fibrosis markers were detected by RT-PCR. Highly expressed proteins from stimulated EVs were identified, and M1-macrophages, LX-2, KMST-6 were treated with these recombinant proteins. Stimulated EVs increased the expression of TNF, IL-1β, and IL-6 in M1-macrophages, TGF-β in LX-2 and KMST-6 compared with the corresponding expression levels in unstimulated EVs. Nucleophosmin, nucleolin, and midkine levels were increased in EVs from stimulated cells compared with protein expression in EVs from unstimulated cells. Leukocyte cell-derived chemotaxin-2 (LECT2) is highly expressed only in EVs from stimulated cells. Stimulation of M1-macrophages with recombinant nucleophosmin, nucleolin, and midkine significantly increased the expression of inflammatory cytokines. Stimulation of LX-2 and KMST-6 with recombinant LECT2 significantly increased the expression of fibrotic markers. These results suggest that basolateral EVs are related to the development of pericholangitis and periductal fibrosis in cholestatic liver diseases.NEW & NOTEWORTHY Our research elucidated that the composition of basolateral EVs from the biliary epithelial cells changed under bile acid exposure and the basolateral EVs contained the novel inflammation-inducing proteins NPM, NCL, and MK and the fibrosis-inducing protein LECT2. We report that these new results are possible to lead to the potential therapeutic target of cholestatic liver diseases in the future.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

Association between Leukocyte Cell-Derived Chemotaxin 2 and Metabolic and Renal Diseases in a Geriatric Population: A Pilot Study

LECT2 is not a routine diagnostic marker for any disease, but it has been associated with many pathologies, including systemic amyloidosis, rheumatoid arthritis, diabetes, atherosclerosis, and metabolic syndrome. With human aortic sections (n = 22) and sera from geriatric subjects (n = 79), we analyzed the relationships that could be observed between this protein and other parameters related to metabolic diseases. As a result, we observed a relatively high (r~0.8, p < 0.05) positive correlation between SRA and LECT2 and a negative correlation between EGFR and LECT2 (r~-0.4, p < 0.05). We observed LECT2 expression in macrophages, myocytes, and other aortic cells, with a tendency to be overexpressed in developed atherosclerotic plaques. We conclude that LECT2 exerts its chemotactic effects not only as a protein synthesized in the liver and secreted and circulating in the blood but also as a locally expressed protein within atherosclerotic plaque development. The LECT2-EGFR correlation suggests an association of this protein with loss of normal renal function. This fact can be associated with LECT2 amyloidosis, although it should be verified whether in the geriatric population there is indeed a widespread accumulation of LECT2 with the progression of aging or whether it is rather a marker of general deterioration of renal function.

The emerging roles of leukocyte cell-derived chemotaxin-2 in immune diseases: From mechanisms to therapeutic potential

Leukocyte cell-derived chemotaxin-2 (LECT2, also named ChM-II), initially identified as a chemokine mediating neutrophil migration, is a multifunctional secreted factor involved in diverse physiological and pathological processes. The high sequence similarity of LECT2 among different vertebrates makes it possible to explore its functions by using comparative biology. LECT2 is associated with many immune processes and immune-related diseases via its binding to cell surface receptors such as CD209a, Tie1, and Met in various cell types. In addition, the misfolding LECT2 leads to the amyloidosis of several crucial tissues (kidney, liver, and lung, etc.) by inducing the formation of insoluble fibrils. However, the mechanisms of LECT2-mediated diverse immune pathogenic conditions in various tissues remain to be fully elucidated due to the functional and signaling heterogeneity. Here, we provide a comprehensive summary of the structure, the “double-edged sword” function, and the extensive signaling pathways of LECT2 in immune diseases, as well as the potential applications of LECT2 in therapeutic interventions in preclinical or clinical trials. This review provides an integrated perspective on the current understanding of how LECT2 is associated with immune diseases, with the aim of facilitating the development of drugs or probes against LECT2 for the theranostics of immune-related diseases.

Liver infiltration of multiple immune cells during the process of acute liver injury and repair

BACKGROUND

Immune cells, including neutrophils, natural killer (NK) cells, T cells, NKT cells and macrophages, participate in the progression of acute liver injury and hepatic recovery. To date, there has been no systematic study on the quantitative changes in these different immune cells from initial injury to subsequent recovery.

AIM

To investigate the infiltration changes of various immune cells in acute liver injury models over time, and to study the relationship between the changes in leukocyte cell-derived chemotaxin 2 (LECT2) and the infiltration of several immune cells.

METHODS

Carbon tetrachloride- and concanavalin A-induced acute liver injury models were employed to mimic toxin-induced and autoimmune-mediated liver injury respectively. The quantitative changes in various immune cells were monitored at different time points. Serum samples were collected, and liver tissues were harvested. Ly6G, CD161, CD4, CD8 and F4/80 staining were used to indicate neutrophils, NK/NKT cells, CD4⁺ T cells, CD8⁺ T cells and macrophages, respectively. Lect2-KO mice were used to detect the function of LECT2.

RESULTS

During the injury and repair process, different types of immune cells began to increase, reached their peaks and fell into decline at different time points. Furthermore, when the serum alanine transaminase (ALT) and aspartate transaminase (AST) indices reverted to normal levels 7 d after the injury, the infiltration of immune cells still existed even 14 d after the injury, showing an obvious lag effect. We found that the expression of LECT2 was upregulated in acute liver injury mouse models, and the liver injuries of Lect2-KO mice were less severe than those of wild-type mice. Compared with wild-type mice, Lect2-KO mice had different immune cell infiltration.

CONCLUSION

The recovery time of immune cells was far behind that of serum ALT and AST during the process of liver repair. LECT2 could regulate monocyte/macrophage chemotaxis and might be used as a therapeutic target for acute liver injury.