MyD88 in hepatic stellate cells enhances liver fibrosis via promoting macrophage M1 polarization

The circAno6/miR-296-3p/TLR4 signaling axis mediates the inflammatory response to induce the activation of hepatic stellate cells

BACKGROUND

Circular RNA (circRNA) is a novel functional non-coding RNA(ncRNA) that plays a role in the occurrence and development of multiple human liver diseases, including liver fibrosis (LF). LF is a reversible repair response after liver injury, and the activation of hepatic stellate cells (HSCs) is the core event. However, the regulatory mechanisms by which circRNAs induce the activation of HSCs in LF are still poorly understood. The circAno6/miR-296-3p/toll-like receptor 4 (TLR4) signaling axis that mediates the inflammatory response and causes the activation of HSCs was investigated in this study.

METHODS

First, a circAno6 overexpression plasmid and small interfering RNA were transfected into cells to determine whether circAno6 can affect the function of HSCs. Second, real-time quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), western blotting (WB) and immunofluorescence (IF) were used to detect the effects of circAno6 plasmid/siRNA transfection on HSC activation indices, inflammatory markers and the circAno6/miR-296-3p/TLR4 signaling axis. The subcellular position of circAno6 was then examined by nucleo-cytoplasmic separation and fluorescence in situ hybridization (FISH). Finally, a luciferase reporter gene assay was used to identify the relationship between circAno6 and miR-296-3p as well as the relationship between miR-296-3p and TLR4.

RESULTS

CircAno6 was considerably upregulated in HSCs and positively correlated with cell proliferation and alpha-smooth muscle actin (α-SMA), collagen I, NOD-likereceptorthermalproteindomainassociatedprotein 3 (NLRP3), interleukin-1β (IL-1β) and interleukin-18 (IL-18) expression. Overexpression of circAno6 increased the inflammatory response and induced HSC activation, whereas interference resulted in the opposite effects. FISH experiments revealed the localization of circAno6 in the cytoplasm. Then, a double luciferase reporter assay confirmed that miR-296-3p significantly inhibited luciferase activity in the circAno6-WT and TLR4-WT groups.

CONCLUSION

This study suggests that circAno6 and miR-296-3p/TLR4 may form a regulatory axis and regulate the inflammatory response, which in turn induces HSC activation. Targeting circAno6 may be a potential therapeutic strategy to treat LF.

The roles of orphan nuclear receptor 4 group A1 and A2 in fibrosis

Fibrosis is not a disease but rather an outcome of the pathological tissue repair response. Many myofibroblasts are activated which lead to the excessive accumulation of extracellular matrix components such as collagen and fibronectin with fibrosis. A variety of organs, including kidney, liver, lung, heart and skin, can undergo fibrosis under the stimulation of exogenous or endogenous pathogenic factors. The orphan nuclear receptor 4 group A1 (NR4A1) and nuclear receptor 4 group A2（NR4A2）are belong to the nuclear receptor subfamily and inhibit the occurrence and development of fibrosis. NR4A1 is an inhibitory factor of TGF-β signaling transduction. Overexpression of NR4A1 in fibroblasts can reduce TGF-β induced collagen deposition and fibrosis related gene expression. Here, we summarize the current research progress on the NR4A1/2 and fibrosis, providing reference for the treatment of fibrosis.

Pathoimmunological analyses of fatal E11 infection in premature infants

E11 causes acute fulminant hepatitis in newborns. We investigated the pathological changes of different tissues from premature male twins who died due to E11 infection. The E11 expression level was higher in the liver than in other tissues. IP10 was upregulated in liver tissue in the patient group, and might be regulated by IFNAR and IRF7, whereas IFNα was regulated by IFNAR or IRF5.

Morus alba L. (Sangzhi) alkaloids mitigate atherosclerosis by regulating M1/M2 macrophage polarization

BACKGROUND

Atherosclerosis (AS) is an important cause of cardiovascular disease, posing a substantial health risk. Recognized as a chronic inflammatory disorder, AS hinges on the pivotal involvement of macrophages in arterial inflammation, participating in its formation and progression. Sangzhi alkaloid (SZ-A) is a novel natural alkaloid extracted from the mulberry branches, has extensive pharmacological effects and stable pharmacokinetic characteristics. However, the effects and mechanisms of SZ-A on AS remain unclear.

PURPOSE

To explore the effect and underlying mechanisms of SZ-A on inflammation mediated by macrophages and its role in AS development.

METHODS

Atherosclerosis was induced in vivo in apolipoprotein E-deficient mice through a high-fat and high-choline diet. We utilized macrophages and vascular endothelial cells to investigate the effects of SZ-A on macrophage polarization and its anti-inflammatory properties on endothelial cells in vitro. The transcriptomic analyses were used to investigate the major molecule that mediates cell-cell interactions and the antiatherogenic mechanisms of SZ-A based on AS, subsequently validated in vivo and in vitro.

RESULTS

SZ-A demonstrated a significant inhibition in vascular inflammation and alleviation of AS severity by mitigating macrophage infiltration and modulating M1/M2 macrophage polarization in vitro and in vivo. Moreover, SZ-A effectively reduced the release of the proinflammatory mediator C-X-C motif chemokine ligand (CXCL)-10, predominantly secreted by M1 macrophages. This reduction in CXCL-10 contributed to improved endothelial cell function, reduced recruitment of additional macrophages, and inhibited the inflammatory amplification effect. This ultimately led to the suppression of atherogenesis.

CONCLUSION

SZ-A exhibited potent anti-inflammatory effects by inhibiting macrophage-mediated inflammation, providing a new therapeutic avenue against AS. This is the first study demonstrating the efficacy of SZ-A in alleviating AS severity and offers novel insights into its anti-inflammatory mechanism.

Immunoreactive Microenvironment Modulator GBP5 Suppresses Ovarian Cancer Progression by Inducing Canonical Pyroptosis

Ovarian cancer has the highest mortality among gynecological malignancies, and exploring effective strategies to reverse the immunosuppressive tumor microenvironment in patients remains a pressing scientific challenge. In this study, we identified a pyroptosis-related protective factor, GBP5, which significantly inhibits the growth of ovarian cancer cells and patient-derived ovarian cancer organoids, impeding the invasion and migration of ovarian cancer cells. Results of immunohistochemistry and external single-cell data verification were consistent. Further research confirmed that GBP5 in ovarian cancer cell can induce canonical pyroptosis through JAK2/STAT1 pathway, thereby restraining the progression of ovarian cancer. Interestingly, in this study, we also discovered that ovarian cancer cells with high GBP5 expression exhibit increased expressions of CXCL9/10/11 in a co-culture assay. Subsequent immune cell infiltration analyses revealed the remodeling of immunosuppressive microenvironment in ovarian cancer patients, characterized by increased infiltration and polarization of M1 macrophages. External immunotherapy database analysis showed profound potential for the application of GBP5 in immunotherapy strategies for ovarian cancer. Overall, our study demonstrates that the protective factor GBP5 significantly inhibits ovarian cancer progression, triggering canonical pyroptosis through the JAK2-STAT1 pathway. Driven by its pro-inflammatory nature, it can also enhance M1 macrophages polarization and reverse immunosuppressive microenvironment, thus providing new insights for ovarian cancer treatment.

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Therapeutic Activity of Resolvin D1 (RvD1) in Murine MASH

Background and Aims

Recent studies have highlighted the beneficial effect of resolvin D1 (RvD1), a DHA-derived specialized pro-resolving mediator, on metabolic dysfunction-associated steatohepatitis (MASH), but the underlying mechanisms are not well understood. Our study aims to determine the mechanism by which RvD1 protects against MASH progression.

Methods

RvD1 was administered to mice with experimental MASH, followed by bulk and single-cell RNA sequencing analysis. Primary cells including bone marrow-derived macrophages (BMDMs), Kupffer cells, T cells, and primary hepatocytes were isolated to elucidate the effect of RvD1 on inflammation, cell death, and fibrosis regression genes.

Results

Hepatic tissue levels of RvD1 were decreased in murine and human MASH, likely due to an expansion of pro-inflammatory M1-like macrophages with diminished ability to produce RvD1. Administering RvD1 reduced inflammation, cell death, and liver fibrosis. Mechanistically, RvD1 reduced inflammation by suppressing the Stat1-Cxcl10 signaling pathway in macrophages and prevented hepatocyte death by alleviating ER stress-mediated apoptosis. Moreover, RvD1 induced Mmp2 and decreased Acta2 expression in hepatic stellate cells (HSCs), and promoted Mmp9 and Mmp12 expression in macrophages, leading to fibrosis regression in MASH.

Conclusions

RvD1 reduces Stat1-mediated inflammation, mitigates ER stress-induced apoptosis, and promotes MMP-mediated fibrosis regression in MASH. This study highlights the therapeutic potential of RvD1 to treat MASH.

Impact and implications

Metabolic dysfunction-associated steatohepatitis (MASH) is an increasing healthcare burden worldwide. Current treatments for MASH and its sequelae are very limited. Recent studies highlighted the therapeutic benefit of specialized pro-resolving mediators (SPMs), including resolvin D1 (RvD1), in liver diseases. However, the mechanisms underlying these beneficial effects are not well understood. Based on unbiased transcriptomic analyses using bulk and single-cell RNA sequencing in RvD1-treated MASH livers, we show that RvD1 suppresses Stat1-mediated inflammatory responses and ER stress-induced apoptosis, and induces gene expression related to fibrosis regression. Our study provides new mechanistic insight into the role of RvD1 in MASH and highlights its therapeutic potential to treat MASH.

Highlights

Liver RvD1 levels are decreased in MASH patients and MASH miceRvD1 administration suppresses Stat1-mediated inflammatory responseRvD1 administration alleviates ER stress-induced apoptosisRvD1 administration induces fibrosis regression gene expression.

Tianhuang formula ameliorates liver fibrosis by inhibiting CCL2-CCR2 axis and MAPK/NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

In the progression of chronic liver diseases, liver fibrosis is a reversible pathophysiologic event for liver diseases prognosis and risk of cirrhosis. Liver injury factors of different etiologies mediate this process. There is still a lack of effective medications for treating liver fibrosis. Additionally, the ameliorative effects of traditional herbs on liver fibrosis have been commonly reported. Tianhuang formula (THF) is a drug combination consisting of 2 traditional Chinese herbs, which has been showing significant improvement in metabolic liver diseases. However, the hepatoprotective effect and mechanism of THF in ameliorating liver fibrosis are still unclear.

AIM OF THE STUDY

This study aimed to investigate the effects of THF on carbon tetrachloride (CCl4)-induced and methionine-choline-deficient (MCD) diet-induced liver fibrosis model and to reveal the potential mechanisms. It can provide experimental evidence for THF as a therapeutic candidate for liver fibrosis.

MATERIALS AND METHODS

In this study, CCl4-induced mice were treated with THF (80 mg/kg, 160 mg/kg) or Fuzheng Huayu (FZHY) capsules (4.8 g/kg) for 6 weeks. MCD-induced mice received the same doses of THF or FZHY for 4 weeks. FZHY is used as a comparative study in these two models. Following that, using kit reagents detected changes in relevant serum and liver biochemical indicators. Histological changes in mouse liver were measured by staining of H&E and Sirius Red. The markers expression of liver fibrosis and inflammation were detected using qRT-PCR, western blotting and immunohistochemical staining analysis. The potential regulatory mechanism of THF to ameliorate liver fibrosis was performed by RNA-sequencing analysis. Finally, the analysis results were verified by immunofluorescence co-staining, qRT-PCR and western blotting.

RESULTS

Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and hepatic triglyceride (TG) levels in CCl4 and MCD-induced liver fibrosis mice were significantly improved after THF treatment. Meanwhile, the expression of fibrosis and inflammation markers were significantly suppressed. Furthermore, THF downregulated the expression of the macrophage marker CD68. According to RNA-sequencing analysis, we found the CCL2-CCR2 axis and MAPK/NF-κB as the potential signaling pathway for THF against liver fibrosis.

CONCLUSION

This study revealed that THF ameliorated liver injury, inflammation and fibrotic process by inhibiting CCL2-CCR2 axis and its downstream MAPK/NF-κB signaling pathway.

Jiawei Taohe Chengqi decoction inhibition of the notch signal pathway affects macrophage reprogramming to inhibit HSCs activation for the treatment of hepatic fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

Jiawei Taohe Chengqi Tang (JTCD) is a modified formulation of Traditional Chinese Medicine (TCM) known as Taohe Chengqi Decoction, which has been described in the ancient TCM literature "Treatise on Febrile Diseases". As a formula that can activate blood circulation and eliminate blood stasis and regulate Yin and Yang in traditional Chinese medicine applications, JTCD has been reported to be effective in the treatment of chronic liver disease and hepatic fibrosis (HF).

AIM OF STUDY

The current study aimed to evaluate the effectiveness of JTCD in modulating hepatic macrophages by regulating the Notch signal pathway, and to further investigate the mechanisms underlying macrophage reprogramming that leads to HF.

MATERIALS AND METHODS

Molecular assays were performed using in vitro cultures of human mononuclear THP-1 cells and human-derived hepatic stellate cells LX-2. CCl4-induced mice were utilized as an in vivo model to simulate HF.

RESULTS

Our results demonstrated that JTCD exhibited dual effects by inhibiting hepatic stellate cell (HSCs) activation and modulating the polarisation of macrophages towards the M2 phenotype while decreasing the M1 phenotype. Network pharmacological analyses and molecular docking studies revealed that the Notch signal pathway was significantly enriched and played a crucial role in the therapeutic response of JTCD against HF. Moreover, through the establishment of a co-culture model, we validated that JTCD inhibited the Notch signal pathway in macrophages, leading to alterations in macrophage reprogramming, subsequent inhibition of HSC activation, and ultimately exerting anti-HF effects.

CONCLUSION

In conclusion, our findings provide solid evidence for JTCD in treating HF, as it suppresses the Notch signal pathway in macrophages, regulates macrophage reprogramming, and inhibits HSC activation.

MyD88 in myofibroblasts enhances nonalcoholic fatty liver disease-related hepatocarcinogenesis via promoting macrophage M2 polarization

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver diseases and has emerged as the leading factor in the pathogenesis of hepatocellular carcinoma (HCC). MyD88 contributes to the development of HCC. However, the underlying mechanism by which MyD88 in myofibroblasts regulates NAFLD-associated liver cancer development remains unknown.

RESULTS

Myofibroblast MyD88-deficient (SMAMyD88-/-) mice were protected from diet-induced obesity and developed fewer and smaller liver tumors. MyD88 deficiency in myofibroblasts attenuated macrophage M2 polarization and fat accumulation in HCC tissues. Mechanistically, MyD88 signaling in myofibroblasts enhanced CCL9 secretion, thereby promoting macrophage M2 polarization. This process may depend on the CCR1 receptor and STAT6/ PPARβ pathway. Furthermore, liver tumor growth was attenuated in mice treated with a CCR1 inhibitor. CCLl5 (homologous protein CCL9 in humans) expression was increased in myofibroblasts of HCC and was associated with shorter survival of patients with HCC. Thus, our results indicate that MyD88 in myofibroblasts promotes NAFLD-related HCC progression and may be a promising therapeutic target for HCC treatment.

CONCLUSION

This study demonstrates that MyD88 in myofibroblasts can promote nonalcoholic fatty liver disease-related hepatocarcinogenesis by enhancing macrophage M2 polarization, which might provide a potential molecular therapeutic target for HCC.

Recent advances in pyroptosis, liver disease, and traditional Chinese medicine: A review

In recent years, the incidence of liver disease has increased, becoming a major cause of death. Various liver diseases are intricately linked to pyroptosis, which is one of the most common forms of programmed cell death. As a powerful weapon in the fight against liver diseases, traditional Chinese medicine (TCM) can affect pyroptosis via a number of routes, including the classical, nucleotide oligomerization domain-like receptors protein 3/caspase-1/gasdermin D (GSDMD) pathway, the nonclassical lipopolysaccharide/caspase-11/GSDMD pathway, the ROS/caspase-3/gasdermin E pathway, the caspase-9/caspase-3/GSDMD pathway, and the Apaf-1/caspase-11/caspase-3 pathway. In this review, we provide an overview of pyroptosis, the interplay between pyroptosis and liver diseases, and the mechanisms through which TCM regulates pyroptosis in liver diseases. The information used in the text was collected and compiled from the databases of PubMed, Web of Science, Scopus, CNKI, and Wanfang Data up to June 2023. The search was not limited with regard to the language and country of the articles. Research and review articles were included, and papers with duplicate results or unrelated content were excluded. We examined the current understanding of the relationship between pyroptosis and liver diseases as well as the advances in TCM interventions to provide a resource for the identification of potential targets for TCM in the treatment of liver diseases.

Targeting MyD88: Therapeutic mechanisms and potential applications of the specific inhibitor ST2825

BACKGROUND

Myeloid differentiation factor-88 (MyD88) is a crucial adapter protein that coordinates the innate immune response and establishes an adaptive immune response. The interaction of the Toll/Interleukin-1 receptor (IL-1R) superfamily with MyD88 triggers the activation of various signalling pathways such as nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), promoting the production of a variety of immune and inflammatory mediators and potentially driving the development of a variety of diseases.

OBJECTIVE

This article will explore the therapeutic potential and mechanism of the MyD88-specific inhibitor ST2825 and describe its use in the treatment of several diseases. We envision future research and clinical applications of ST2825 to provide new ideas for the development of anti-inflammatory drugs and disease-specific drugs to open new horizons for the prevention and treatment of related inflammatory diseases.

MATERIALS AND METHODS

This review analysed relevant literature in PubMed and other databases. All relevant studies on MyD88 inhibitors and ST2825 that were published in the last 20 years were used as screening criteria. These studies looked at the development and improvement of MyD88 inhibitors and ST2825.

RESULTS

Recent evidence using the small-molecule inhibitor of ST2825 has suggested that blocking MyD88 activity can be used to treat diseases such as neuroinflammation, inflammatory diseases such as acute liver/kidney injury, or autoimmune diseases such as systemic lupus erythematosus and can affect transplantation immunity. In addition, ST2825 has potential therapeutic value in B-cell lymphoma with the MyD88 L265P mutation.

CONCLUSION

Targeting MyD88 is a novel therapeutic strategy, and scientific research is presently focused on the development of MyD88 inhibitors. The peptidomimetic compound ST2825 is a widely studied small-molecule inhibitor of MyD88. Thus, ST2825 may be a potential therapeutic small-molecule agent for modulating host immune regulation in inflammatory diseases and inflammatory therapy.

Molecular mechanisms of metabolic disease-associated hepatic inflammation in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide, with a progressive form of non-alcoholic steatohepatitis (NASH). It may progress to advanced liver diseases, including liver fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD/NASH is a comorbidity of many metabolic disorders such as obesity, insulin resistance, type 2 diabetes, cardiovascular disease, and chronic kidney disease. These metabolic diseases are often accompanied by systemic or extrahepatic inflammation, which plays an important role in the pathogenesis and treatment of NAFLD or NASH. Metabolites, such as short-chain fatty acids, impact the function, inflammation, and death of hepatocytes, the primary parenchymal cells in the liver tissue. Cholangiocytes, the epithelial cells that line the bile ducts, can differentiate into proliferative hepatocytes in chronic liver injury. In addition, hepatic non-parenchymal cells, including liver sinusoidal endothelial cells, hepatic stellate cells, and innate and adaptive immune cells, are involved in liver inflammation. Proteins such as fibroblast growth factors, acetyl-coenzyme A carboxylases, and nuclear factor erythroid 2-related factor 2 are involved in liver metabolism and inflammation, which are potential targets for NASH treatment. This review focuses on the effects of metabolic disease-induced extrahepatic inflammation, liver inflammation, and the cellular and molecular mechanisms of liver metabolism on the development and progression of NAFLD and NASH, as well as the associated treatments.

FKBP5 deficiency attenuates calcium oxalate kidney stone formation by suppressing cell-crystal adhesion, apoptosis and macrophage M1 polarization via inhibition of NF-κB signaling

Surgical crushing of stones alone has not addressed the increasing prevalence of kidney stones. A promising strategy is to tackle the kidney damage and crystal aggregation inherent in kidney stones with the appropriate therapeutic target. FKBP prolyl isomerase 5 (FKBP5) is a potential predictor of kidney injury, but its status in calcium oxalate (CaOx) kidney stones is not clear. This study attempted to elucidate the role and mechanism of FKBP5 in CaOx kidney stones. Lentivirus and adeno-associated virus were used to control FKBP5 expression in a CaOx kidney stone model. Transcriptomic sequencing and immunological assays were used to analyze the mechanism of FKBP5 deficiency in CaOx kidney stones. The results showed that FKBP5 deficiency reduced renal tubular epithelial cells (RTEC) apoptosis and promoted cell proliferation by downregulating BOK expression. It also attenuated cell-crystal adhesion by downregulating the expression of CDH4. In addition, it inhibited M1 polarization and chemotaxis of macrophages by suppressing CXCL10 expression in RTEC. Moreover, the above therapeutic effects were exerted by inhibiting the activation of NF-κB signaling. Finally, in vivo experiments showed that FKBP5 deficiency attenuated stone aggregation and kidney injury in mice. In conclusion, this study reveals that FKBP5 deficiency attenuates cell-crystal adhesion, reduces apoptosis, promotes cell proliferation, and inhibits macrophage M1 polarization and chemotaxis by inhibiting NF-κB signaling. This provides a potential therapeutic target for CaOx kidney stones.

Sappanone A Alleviates the Severity of Carbon Tetrachloride-Induced Liver Fibrosis in Mice

Liver fibrosis is a major challenge to global health because of its various complications, including cirrhosis and hepatocarcinoma, while no effective treatment is available for it. Sappanone A (SA) is a homoisoflavonoid extracted from the heartwood of Caesalpinia sappan Linn. with anti-inflammatory and antioxidant properties. However, the effects of SA on hepatic fibrosis remain unknown. This study aimed to investigate the protective effects of SA on carbon tetrachloride (CCl4)-induced liver fibrosis in mice. To establish a liver fibrosis model, mice were treated intraperitoneally (i.p.) with CCl4 for 4 weeks. SA (25, 50, and 100 mg/kg body weight) was i.p. injected every other day during the same period. Our data indicated that SA decreased liver injury, fibrotic responses, and inflammation due to CCl4 exposure. Consistently, SA reduced oxidative stress and its-mediated hepatocyte death in fibrotic livers. Of note, SA could not directly affect the activation of hepatic stellate cells. Mechanistically, SA treatment lessened oxidative stress-triggered cell death in hepatocytes after CCl4 exposure. SA down-regulated the expression of M1 macrophage polarization markers (CD86 and iNOS) and up-regulated the expression of M2 macrophage polarization markers (CD163, IL-10, and Arg1) in livers and macrophages. Meanwhile, SA induced the activation of peroxisome proliferator-activated receptor gamma (PPARγ). However, decreased inflammatory responses and the trend of M2 macrophage polarization provided by SA were substantially abolished by SR202 (a PPARγ inhibitor) treatment in macrophages. Additionally, SA treatment promoted fibrosis regression. Taken together, our findings revealed that treatment with SA alleviated CCl4-induced fibrotic liver in mice through suppression of oxidative stress-mediated hepatocyte death and promotion of M2 macrophage polarization via PPARγ. Thus, SA might pave the way for a new hepatoprotective agent to treat liver fibrosis.

FABP4 in LSECs promotes CXCL10-mediated macrophage recruitment and M1 polarization during NAFLD progression

BACKGROUND AND AIMS

Non-alcoholic liver disease (NAFLD) is emerging as the leading cause of end-stage liver disease with a serious threat to global health burden. Fatty acid-binding protein 4 (FABP4) is closely associated with metabolic syndromes. We aimed to explore the potential mechanisms of FABP4 in NAFLD progression.

MATERIALS AND METHODS

For NAFLD mice, animals were fed with high fat diet (HFD) for 20 weeks. The assays of hematoxylin and eosin, Sirius Red, oil red O staining and immunohistology were performed to evaluate hepatic pathology. Flow cytometric analysis was used to distinguish macrophage subtypes.

RESULTS

Serum FABP4 level was positively correlate with the severity of hepatic steatosis in NAFLD patients. FABP4 expression was mainly distributed in liver sinusoidal endothelial cells (LSECs), which was significantly increased in HFD mice. The level of CXCL10 was positively correlated with FABP4 at mRNA and serum level. FABP4 inhibition resulted in decreased expression of CXCL10. The percentage of M1 macrophage and CXCR3⁺ cells in infiltrated macrophage was increased in liver of HFD mice. Inhibition of FABP4 ameliorated HFD-induced M1 macrophage polarization as well as CXCR3⁺ macrophages recruitment. Recombinant CXCL10 and co-culturing with TMNK-1 stimulated macrophage toward M1 polarization, which could be reversed by CXCR3 inhibitor. Palmitic acid treatment resulted in increased nuclear P65 expression, which could be reversed by inhibiting FABP4. Cxcl10 expression was dramatically suppressed by NF-κB inhibitor.

CONCLUSIONS

FABP4 in LSECs may play a pathogenic role in NAFLD course by promoting CXCL10-mediated macrophage M1 polarization and CXCR3⁺ macrophage infiltration via activating NF-κB/p65 signaling.

The role of murine M1 macrophages from different sources in unilateral ureteral obstruction

Introduction

The unilateral ureteral obstruction (UUO) model is the most extensively used model to investigate chronic renal fibrosis. Macrophages play a critical role in the UUO model. We aimed to analyze the phenotype of macrophages from different sources activated in vitro and explore the role of M1 macrophages from various sources in UUO.

Material and methods

C57BL/6 mice were randomly allocated to five different groups (n = 5 per group): the sham-operated control group, PBS-treated (UUO + PBS) group, bone marrow-derived M1 macrophage-treated (UUO + BM1) group, peritoneal M1 macrophage-treated (UUO + PM1) group, and splenic M1 macrophage-treated (UUO + SPM1) group. After M1 macrophages were injected into the tail vein of UUO-treated mice, renal fibrosis indexes were determined using HE, Masson staining, and α-SMA.

Results

Compared to those in the UUO + PBS group, the pathological changes were much more severe in the UUO + BM1, UUO + PM1, and UUO + SPM1 groups. Compared to that in the UUO + PBS group, UUO + BM1 group, and UUO + SPM1 group, the collagen area in the UUO + PM1 group was higher at post-UUO day 5 (p < 0.01). The expression of α-SMA in the UUO + PM1 group was higher than that in the UUO + PBS group, UUO + BM1 group, and UUO + SPM1group (p < 0.001).

Conclusions

The M1 macrophages cultured in vitro were reinjected into mice and aggravated kidney injury and fibrosis. Compared with BM1 and SPM1, PM1 demonstrated a stronger effect on inducing renal injury and fibrosis.

Immune microenvironment changes of liver cirrhosis: emerging role of mesenchymal stromal cells

Cirrhosis is a progressive and diffuse liver disease characterized by liver tissue fibrosis and impaired liver function. This condition is brought about by several factors, including chronic hepatitis, hepatic steatosis, alcohol abuse, and other immunological injuries. The pathogenesis of liver cirrhosis is a complex process that involves the interaction of various immune cells and cytokines, which work together to create the hepatic homeostasis imbalance in the liver. Some studies have indicated that alterations in the immune microenvironment of liver cirrhosis are closely linked to the development and prognosis of the disease. The noteworthy function of mesenchymal stem cells and their paracrine secretion lies in their ability to promote the production of cytokines, which in turn enhance the self-repairing capabilities of tissues. The objective of this review is to provide a summary of the alterations in liver homeostasis and to discuss intercellular communication within the organ. Recent research on MSCs is yielding a blueprint for cell typing and biomarker immunoregulation. Hopefully, as MSCs researches continue to progress, novel therapeutic approaches will emerge to address cirrhosis.

Mivebresib alleviates systemic lupus erythematosus-associated diffuse alveolar hemorrhage via inhibiting infiltration of monocytes and M1 polarization of macrophages

BACKGROUND

Diffuse alveolar hemorrhage (DAH) is a serious complication that can arise from systemic lupus erythematosus (SLE) and other autoimmune diseases. While current treatments for DAH have limitations and adverse side effects, recent evidence suggests that inflammatory macrophages play a crucial role in the development of DAH. In this study, we investigated Mivebresib, a BET protein-bromodomain-containing protein 4 (BRD4) inhibitor, as a potential treatment for DAH.

RESULTS

Our findings show that Mivebresib effectively protected C57BL/6J mice against pristane-induced DAH by inhibiting the migration and polarization of monocytes and macrophages, as well as pathogenic B and T cells. Specifically, Mivebresib modified the distribution of leukocytes, impeded the polarization of inflammatory macrophages, and reduced the frequency of CD19 + CD5 + B cells in the lungs of pristane-treated mice. Furthermore, in vitro experiments demonstrated that Mivebresib inhibited LPS-induced M1 polarization of macrophages and the expression of pro-inflammatory cytokines, M1 marker genes, and chemokines-chemokine receptors while thwarting the secretion of IL-6 and TNF-α. Transcriptomic analysis suggested and experiments comfimed that Mivebresib inhibits M1 polarization via interrupting the p300/BRD4/HIF1A axis.

CONCLUSIONS

Our study demonstrates that Mivebresib has therapeutic potential for the life-threatening complication of DAH caused by SLE. By inhibiting macrophage polarization and the infiltration of inflammatory cells, Mivebresib may offer a promising treatment option for patients suffering from this disease.

Engineered fibrotic liver-targeted truncated transforming growth factor β receptor type II variant for superior anti-liver fibrosis therapy

Truncated transforming growth factor β receptor type II (tTβRII) is a promising anti-liver fibrotic candidate because it serves as a trap for binding excessive TGF-β1 by means of competing with wild type TβRII (wtTβRII). However, the widespread application of tTβRII for the treatment of liver fibrosis has been limited by its poor fibrotic liver-homing capacity. Herein, we designed a novel tTβRII variant Z-tTβRII by fusing the platelet-derived growth factor β receptor (PDGFβR)-specific affibody Z_PDGFβR to the N-terminus of tTβRII. The target protein Z-tTβRII was produced using Escherichia coli expression system. In vitro and in vivo studies showed that Z-tTβRII has a superior specific fibrotic liver-targeting potential via the engagement of PDGFβR-overexpressing activated hepatic stellate cells (aHSCs) in liver fibrosis. Moreover, Z-tTβRII significantly inhibited cell migration and invasion, and downregulated fibrosis- and TGF-β1/Smad pathway-related protein levels in TGF-β1-stimiluated HSC-T6 cells. Furthermore, Z-tTβRII remarkably ameliorated liver histopathology, mitigated the fibrosis responses and blocked TGF-β1/Smad signaling pathway in CCl₄-induced liver fibrotic mice. More importantly, Z-tTβRII exhibits a higher fibrotic liver-targeting potential and stronger anti-fibrotic effects than either its parent tTβRII or former variant BiPPB-tTβRII (PDGFβR-binding peptide BiPPB modified tTβRII). In addition, Z-tTβRII shows no significant sign of potential side effects in other vital organs in liver fibrotic mice. Taken together, we conclude that Z-tTβRII with its a high fibrotic liver-homing potential, holds a superior anti-fibrotic activity in liver fibrosis in vitro and in vivo, which may be a potential candidate for targeted therapy for liver fibrosis.

MLKL signaling regulates macrophage polarization in acute pancreatitis through CXCL10

Acute pancreatitis (AP) is a disease characterized by local and systemic inflammation with an increasing incidence worldwide. Receptor-interacting serine/threonine protein kinase 3 (RIPK3), mixed-lineage kinase domain-like protein (MLKL), and innate immune cell macrophages have been reported to be involved in the pathogenesis of AP. However, the mechanisms by which RIPK3 and MLKL regulate pancreatic injury, as well as the interactions between injured pancreatic acinar cells and infiltrating macrophages in AP, remain poorly defined. In the present study, experimental pancreatitis was induced in C57BL/6J, Ripk3-/- and Mlkl-/- mice by cerulein plus lipopolysaccharide in vivo, and primary pancreatic acinar cells were also isolated to uncover cellular mechanisms during cerulein stimulation in vitro. The results showed that MLKL and its phosphorylated protein p-MLKL were upregulated in the pancreas of the mouse AP model and cerulein-treated pancreatic acinar cells, independent of its canonical upstream molecule Ripk3, and appeared to function in a cell death-independent manner. Knockout of Mlkl attenuated AP in mice by reducing the polarization of pancreatic macrophages toward the M1 phenotype, and this protective effect was partly achieved by reducing the secretion of CXCL10 from pancreatic acinar cells, whereas knockout of Ripk3 did not. In vitro neutralization of CXCL10 impaired the pro-M1 ability of the conditioned medium of cerulein-treated pancreatic acinar cells, whereas in vivo neutralization of CXCL10 reduced the polarization of pancreatic macrophages toward M1 and the severity of AP in mice. These findings suggested that targeting the MLKL-CXCL10-macrophage axis might be a promising strategy for the treatment of AP.

The gut-liver axis in immune remodeling of hepatic cirrhosis

In healthy settings, the gut-liver axis allows host-microbiota communications and mediates immune homeostasis through bidirectional regulation. Meanwhile, in diseases, gut dysbiosis, combined with an impaired intestinal barrier, introduces pathogens and their toxic metabolites into the system, causing massive immune alternations in the liver and other extrahepatic organs. Accumulating evidence suggests that these immune changes are associated with the progression of many liver diseases, especially hepatic cirrhosis. Pathogen-associated molecular patterns that originated from gut microbes directly stimulate hepatocytes and liver immune cells through different pattern recognition receptors, a process further facilitated by damage-associated molecular patterns released from injured hepatocytes. Hepatic stellate cells, along with other immune cells, contribute to this proinflammatory and profibrogenic transformation. Moreover, cirrhosis-associated immune dysfunction, an imbalanced immune status characterized by systemic inflammation and immune deficiency, is linked to gut dysbiosis. Though the systemic inflammation hypothesis starts to link gut dysbiosis to decompensated cirrhosis from a clinical perspective, a clearer demonstration is still needed for the role of the gut-liver-immune axis in cirrhosis progression. This review discusses the different immune states of the gut-liver axis in both healthy and cirrhotic settings and, more importantly, summarizes the current evidence about how microbiota-derived immune remodeling contributes to the progression of hepatic cirrhosis via the gut-liver axis.