The Mechanism of How Anti-IL-18 Prevents Concanavalin-A-Induced Hepatic Fibrosis on a Mouse Model

Role of NLRP3 inflammasome in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune rheumatic disease with high mortality, which is featured by inflammation, vascular damage, and aggressive fibrosis. To date, the pathogenesis of SSc remains unclear and effective treatments are still under research. Active NLRP3 recruits downstream proteins such as ASC and caspase-1 and assembles into inflammasome, resulting in excretion of inflammatory cytokines including IL-1β and IL-18, as well as in pyroptosis mediated by gasdermin D. Various studies demonstrated that NLRP3 inflammasome might be involved in the mechanism of tenosynovitis, arthritis, fibrosis, and vascular damage. The pathophysiological changes might be due to the activation of proinflammatory Th2 cells, profibrotic M2 macrophages, B cells, fibroblasts, and endothelial cells. Here, we review the studies focused on NLRP3 inflammasome activation, its association with innate and adaptive immune cells, endothelium injury, and differentiation of fibroblasts in SSc. Furthermore, we summarize the prospect of therapy targeting NLRP3 pathway.

SIRT1/IGFBPrP1/TGF β1 axis involved in cucurbitacin B ameliorating concanavalin A-induced mice liver fibrosis

The present study investigated the improving effect of cucurbitacin B on liver fibrosis induced by concanavalin A in mice and explored its possible mechanism. AST, ALT and TB were detected by kits. ELISA was performed to detect the levels of IL 5, IL 6, IL 13 and TNF-α in serum. Haematoxylin-eosin (HE) staining and Masson's trichrome staining were used to evaluate pathological changes. Western blotting was performed to observe expression levels of sirtuin (SIRT) 1, insulin-like growth factor binding protein-related protein 1 (IGFBPrP1) and TGF β1. The activity of SIRT 1 also was detected. Results showed that cucurbitacin B could effectively improve the abnormal liver function, inhibit liver fibrosis and suppress releases of inflammatory factors in mice induced by concanavalin A. Furthermore, cucurbitacin B could down-regulate the expressions of TGF β1 and IGFBPrP1, increase the expression and activity of SIRT 1. Interestingly, when SIRT1 activity was inhibited by EX 527, a selective inhibitor of SIRT 1, the preventive effect of cucurbitacin B was significantly attenuated. Taken together, the above results showed that cucurbitacin B could significantly suppress releases of inflammatory cytokines and improve liver fibrosis induced by concanavalin A in mice, and those may be achieved through SIRT1/IGFBPrP1/TGF β1 axis.

Neutralization of IL-18 by IL-18 binding protein ameliorates bleomycin-induced pulmonary fibrosis via inhibition of epithelial-mesenchymal transition

Idiopathic pulmonary fibrosis (IPF) is a fatal parenchymal lung disease with limited effective therapies. Interleukin (IL)-18 belongs to a rather large IL-1 gene family and is a proinflammatory cytokine, which acts in both acquired and innate immunity. We have previously reported that IL-18 play an important role in lipopolysaccharide-induced acute lung injury in mice. Persistent inflammation often drives fibrotic progression in the bleomycin (BLM) injury model. However, the role of IL-18 in pulmonary fibrosis (PF) is still unknown. IL-18 binding protein (IL-18BP) is able to neutralize IL-18 biological activity and has a protective effect against renal fibrosis. The aim of this study was to investigate the effects of IL-18BP on BLM-induced PF. In the present study, we found that IL-18 was upregulated in lungs of BLM-injured mice. Neutralization of IL-18 by IL-18BP improved the survival rate and ameliorated BLM-induced PF in mice, which was associated with attenuated pathological changes, reduced collagen deposition, and decreased content of transforming growth factor-β1 (TGF-β1). We further demonstrated that IL-18BP treatment suppressed the BLM-induced epithelial mesenchymal transition (EMT), characterized by decreased α-smooth muscle actin (α-SMA) and increased E-cadherin (E-cad) in vivo. In addition, we provided in vitro evidence demonstrating that IL-18 promoted EMT through upregulation of Snail-1 in A549 cells. In conclusion, our findings raise the possibility that the increase of IL-18 is involved in the development of BLM-induced PF through modulating EMT in a Snail-1-dependent manner. IL-18BP may be a worthwhile candidate option for PF therapy.

Serum levels of interleukin-18-binding protein isoform a: Clinical association with inflammation and pulmonary hypertension in systemic sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune inflammatory disease characterized by extensive tissue fibrosis and various vascular complications. A wealth of evidence suggests the substantial contribution of pro-inflammatory cytokines to the development of SSc, but the role of interleukin (IL)-18 signaling in this disease still remains elusive. To address this issue, we herein determined serum levels of IL-18-binding protein isoform a (IL-18BPa), a soluble decoy receptor for IL-18, by enzyme-linked immunosorbent assay in 57 SSc patients and 20 healthy controls and evaluated their clinical correlation. Serum IL-18BPa levels were higher in SSc patients than in healthy controls, while comparable between diffuse cutaneous SSc and limited cutaneous SSc patients. Although serum IL-18BPa levels were not associated with dermal and pulmonary fibrotic parameters in SSc patients, there was a significant positive correlation between serum IL-18BPa levels and right ventricular systolic pressure estimated by echocardiography. Furthermore, in 24 SSc patients who underwent right heart catheterization, serum IL-18BPa levels positively correlated with mean pulmonary arterial pressure. As for systemic inflammatory markers, significant positive correlations of circulating IL-18BPa levels with erythrocyte sedimentation rate and C-reactive protein were noted. These results suggest that the inhibition of IL-18 signaling by IL-18BPa may be involved in the development of pulmonary vascular involvement leading to pulmonary hypertension and modulate the systemic inflammation in SSc.

Strategies to prevent and reverse liver fibrosis in humans and laboratory animals

Liver fibrosis results from chronic damage to the liver in conjunction with various pathways and is mediated by a complex microenvironment. Based on clinical observations, it is now evident that fibrosis is a dynamic, bidirectional process with an inherent capacity for recovery and remodeling. The major mechanisms involved in liver fibrosis include the repetitive injury of hepatocytes, the activation of the inflammatory response after injury stimulation, and the activation and proliferation of hepatic stellate cells (HSCs), which represents the major extracellular matrix (ECM)-producing cells, stimulated by hepatocyte injury and inflammation. The microenvironment in the liver is synergistically regulated abnormal ECM deposition, scar formation, angiogenesis, and fibrogenesis. Moreover, recent studies have clarified novel mechanism in fibrosis such as epigenetic regulation of HSCs, the leptin and PPARγ pathways, the coagulation system, and even autophagy. Uncovering the mechanisms of liver fibrogenesis provides a basis to develop potential therapies to reverse and treat the fibrotic response, thereby improving the outcomes of patients with chronic liver disease. Although both scientific and clinical challenges remain, emerging studies attempt to reveal the ideal anti-fibrotic drug that could be easily delivered to the liver with high specificity and low toxicity. This review highlights the mechanisms, including novel pathways underlying fibrogenesis that may be translated into preventive and treatment strategies, reviews both current and novel agents that target specific pathways or multiple targets, and discusses novel drug delivery systems such as nanotechnology that can be applied in the treatment of liver fibrosis. In addition, we also discuss some current treatment strategies that are being applied in animal models and in clinical trials.

Intrahepatic mRNA levels of SOCS1 and SOCS3 are associated with cirrhosis but do not predict virological response to therapy in chronic hepatitis C

BACKGROUND

Antiviral treatment of chronic hepatitis C is not invariably successful, costly and associated with serious side-effects, and therefore should be indicated only when the chances of benefitting patients exceed the potential risks. The suppressor of cytokine signalling (SOCS) family members have been suggested to affect the rate of virological response to therapy, but the published evidence is conflicting.

METHODS

We measured the intrahepatic SOCS1, SOCS3 and SOCS7 mRNA levels in 107 chronic hepatitis C patients and assessed their clinical and histological correlates with the virological response to therapy and with some factors known for affecting treatment outcome.

RESULTS

By multivariate analysis, SOCS1, SOCS3 and SOCS7 mRNA levels were not associated with rapid or sustained virological response. Similarly, no association was found between the levels of any intrahepatic SOCS mRNA and those of the homeostasis model assessment of insulin resistance. Conversely, SOCS1 (OR 2.185, 95% CI 1.223-3.906, P=0.0083) and SOCS3 (OR 40.601, 95% CI 2.357-699.25, P=0.0108) mRNA level (but not SOCS7), together with age (OR 1.156, 95% CI 1.049-1.275, P=0.0036), were independently associated with cirrhosis.

CONCLUSIONS

Intrahepatic SOCS1, SOCS3 and SOCS7 mRNA levels do not predict virological response to therapy in chronic hepatitis C. The association between SOCS1, SOCS3 and cirrhosis warrants further study.

Glycyrrhizin regulates CD4+T cell response during liver fibrogenesis via JNK, ERK and PI3K/AKT pathway

The aims of this study were to elucidate the immunomodulatory effects of glycyrrhizin (GL) on CD4(+)T cell responses during liver fibrogenesis. To obtain in vivo evidence about the effects of GL on CD4(+)T cells in livers and spleens of concanavalin A (ConA)-induced mouse model, mice were administrated with ConA together with or without GL for 8 weeks. Mice treated with GL dramatically prevented liver inflammation and fibrosis. Besides, GL inhibited the infiltration of T helper (Th) cell type 1, Th2, Th17 and regulatory T cells (Treg) in livers and spleens of mouse fibrosis models, and regulated the Th1/Th2 and Treg/Th17 balances respectively to a relative dominance of Th1 and Treg lineages in livers. Moreover, GL dramatically enhanced the antifibrotic cytokine interferon (IFN)-γ and interleukin (IL)-10. GL at a concentration of 10 or 100 μg/mL was respectively incubated with ConA-stimulated splenic CD4(+)T cells in vitro, and JNK inhibitor (SP600125), ERK inhibitor (U0126), p38 inhibitor (SB203580) or PI3K/AKT inhibitor (LY29400225) was added during the incubation. Notably, GL not only inhibited ConA-induced proliferation of splenic CD4(+)T cells but also enhanced the mRNAs of IFN-γ and IL-10 in these cells. Be similar to the effects of GL, SP600125, U0126 and LY29400225, however not SB203580, also inhibited ConA-induced CD4(+)T cell proliferation, indicating the involvement of JNK, ERK and PI3K/AKT in this process. Moreover, GL significantly inhibited ConA-induced phosphorylation of JNK, ERK and PI3K/AKT in vitro. Collectively, GL might alleviate liver injury and fibrosis progression via regulation of CD4(+)T cell response in JNK, ERK and PI3K/AKT-dependent pathways.

Significance of the balance between regulatory T (Treg) and T helper 17 (Th17) cells during hepatitis B virus related liver fibrosis

Background

Hepatitis B virus-related liver fibrosis (HBV-LF) always progresses from inflammation to fibrosis. However, the relationship between these two pathological conditions is not fully understood. Here, it is postulated that the balance between regulatory T (Treg) cells and T helper 17 (Th17) cells as an indicator of inflammation may predict fibrosis progression of HBV-LF.

Methodology/Principal Findings

The frequencies and phenotypes of peripheral Treg and Th17 cells of seventy-seven HBeAg-positive chronic hepatitis B (CHB) patients who underwent liver biopsies and thirty healthy controls were determined by flow cytometry. In the periphery of CHB patients, both Treg and Th17 frequencies were significantly increased and correlated, and a lower Treg/Th17 ratio always indicated more liver injury and fibrosis progression. To investigate exact effects of Treg and Th17 cells during HBV-LF, a series of in vitro experiments were performed using purified CD4⁺, CD4⁺CD25⁺, or CD4⁺CD25⁻ cells from the periphery, primary human hepatic stellate cells (HSCs) isolated from healthy liver specimens, human recombinant interleukin (IL)-17 cytokine, anti-IL-17 antibody and HBcAg. In response to HBcAg, CD4⁺CD25⁺ cells significantly inhibited cell proliferation and cytokine production (especially IL-17 and IL-22) by CD4⁺CD25⁻ cells in cell-contact and dose-dependent manners. In addition, CD4⁺ cells from CHB patients, compared to those from HC subjects, dramatically promoted proliferation and activation of human HSCs. Moreover, in a dramatically dose-dependent manner, CD4⁺CD25⁺ cells from CHB patients inhibited, whereas recombinant IL-17 response promoted the proliferation and activation of HSCs. Finally, in vivo evidence about effects of Treg/Th17 balance during liver fibrosis was obtained in concanavalin A-induced mouse fibrosis models via depletion of CD25⁺ or IL-17⁺ cells, and it’s observed that CD25 depletion promoted, whereas IL-17 depletion, alleviated liver injury and fibrosis progression.

Conclusions/Significance

The Treg/Th17 balance might influence fibrosis progression in HBV-LF via increase of liver injury and promotion of HSCs activation.