Metallothioneins alter macrophage phenotype and represent novel therapeutic targets for acetaminophen-induced liver injury

Extracellular metallothionein as a therapeutic target in the early progression of type 1 diabetes

Type 1 diabetes (T1D) is characterized by lymphocyte infiltration into the pancreatic islets of Langerhans, leading to the destruction of insulin-producing beta cells and uncontrolled hyperglycemia. In the nonobese diabetic (NOD) murine model of T1D, the onset of this infiltration starts several weeks before glucose dysregulation and overt diabetes. Recruitment of immune cells to the islets is mediated by several chemotactic cytokines, including CXCL10, while other cytokines, including SDF-1α, can confer protective effects. Global gene expression studies of the pancreas from prediabetic NOD mice and single-cell sequence analysis of human islets from prediabetic, autoantibody-positive patients showed an increased expression of metallothionein (MT), a small molecular weight, cysteine-rich metal-binding stress response protein. We have shown that beta cells can release MT into the extracellular environment, which can subsequently enhance the chemotactic response of Th1 cells to CXCL10 and interfere with the chemotactic response of Th2 cells to SDF-1α. These effects can be blocked in vitro with a monoclonal anti-MT antibody, clone UC1MT. When administered to NOD mice before the onset of diabetes, UC1MT significantly reduces the development of T1D. Manipulation of extracellular MT may be an important approach to preserving beta cell function and preventing the development of T1D.

Ameliorative Effect of Macadamia Nut Protein Peptides on Acetaminophen-Induced Acute Liver Injury in Mice

This study aims to examine the ameliorative effect of macadamia nut protein peptides (MPP) on acetaminophen (APAP)-induced liver injury (AILI) in mice, and develop a new strategy for identifying hepatoprotective functional foods. The molecular weight distribution and amino acid composition of MPP were first studied. Forty mice were then randomized into four groups: control group (CON), APAP model group, APAP+MPP low-dose group (APAP+L-MPP), and APAP+MPP high-dose group (APAP+H-MPP). The APAP+L-MPP (320 mg/kg per day) and APAP+H-MPP (640 mg/kg per day) groups received continuous MPP gavage for 2 weeks. A 12 h of APAP (200 mg/kg) gavage resulted in liver damage. Pathological alterations, antioxidant index levels, expression of toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB), and associated inflammatory factors were determined for each treatment group. The results revealed that the total amino acid content of MPP was 39.58 g/100 g, with Glu, Arg, Asp, Leu, Tyr, and Gly being the major amino acids. The molecular weight range of 0-1000 Da accounted for 73.54%, and 0-500 Da accounted for 62.84% of MPP. MPP ameliorated the pathological morphology and reduced the serum levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase of AILI in mice. MPP significantly increased the activities of superoxide dismutase and glutathione peroxidase in the liver compared with the APAP group. MPP inhibited the expression of TLR4, NF-κB, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) genes in AILI mice. MPP also inhibited the expression levels of inflammatory factors (TNF-α and IL-6). Our study concludes that MPP alleviates AILI in mice by enhancing antioxidant capacity and inhibiting TLR4/NF-κB pathway-related gene activation.

Osteopontin characterizes bile duct-associated macrophages and correlates with liver fibrosis severity in primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is an immune-mediated cholestatic liver disease for which pharmacological treatment options are currently unavailable. PSC is strongly associated with colitis and a disruption of the gut-liver axis, and macrophages are involved in the pathogenesis of PSC. However, how gut-liver interactions and specific macrophage populations contribute to PSC is incompletely understood.

APPROACH AND RESULTS

We investigated the impact of cholestasis and colitis on the hepatic and colonic microenvironment, and performed an in-depth characterization of hepatic macrophage dynamics and function in models of concomitant cholangitis and colitis. Cholestasis-induced fibrosis was characterized by depletion of resident KCs, and enrichment of monocytes and monocyte-derived macrophages (MoMFs) in the liver. These MoMFs highly express triggering-receptor-expressed-on-myeloid-cells-2 ( Trem2 ) and osteopontin ( Spp1 ), markers assigned to hepatic bile duct-associated macrophages, and were enriched around the portal triad, which was confirmed in human PSC. Colitis induced monocyte/macrophage infiltration in the gut and liver, and enhanced cholestasis-induced MoMF- Trem2 and Spp1 upregulation, yet did not exacerbate liver fibrosis. Bone marrow chimeras showed that knockout of Spp1 in infiltrated MoMFs exacerbates inflammation in vivo and in vitro , while monoclonal antibody-mediated neutralization of SPP1 conferred protection in experimental PSC. In human PSC patients, serum osteopontin levels are elevated compared to control, and significantly increased in advanced stage PSC and might serve as a prognostic biomarker for liver transplant-free survival.

CONCLUSIONS

Our data shed light on gut-liver axis perturbations and macrophage dynamics and function in PSC and highlight SPP1/OPN as a prognostic marker and future therapeutic target in PSC.

Kupffer Cells Contested as Early Drivers in the Pathogenesis of Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is an idiopathic chronic immune-mediated cholestatic liver disease characterized by fibro-inflammatory bile duct strictures, progressive hepatobiliary fibrosis, and gut-liver axis disruption. The pathophysiology of PSC remains insufficiently characterized, which hampers the development of effective therapies. Hepatic macrophages (MFs) are implicated in PSC pathogenesis, but the exact role of Kupffer cells (KCs) is unclear. Using the latest markers to discriminate resident KCs (ResKCs) from their monocyte-derived counterparts (MoKCs), and two models for intrahepatic and extrahepatic cholestasis, respectively, this study shows that CLEC4F⁺TIM4⁺ ResKCs are depleted after chronic cholestatic liver injury, whereas infiltrating CLEC4F⁺TIM4^- MoKCs are already enriched during the acute phase. Transcriptional profiling of hepatic MF subsets during early cholestatic injury indicates that ResKCs are indeed activated and that MoKCs express even higher levels of pro-inflammatory and proliferative markers compared with ResKCs. Conditional depletion of KCs, by using Clec4f^DTR transgenic mice, before and during early cholestasis induction had no effect, however, on the composition of the hepatic myeloid cell pool following injury progression and did not affect disease outcomes. Taken together, these results provide new insights on the heterogeneity of the MF pool during experimental PSC and evidence that depletion of resident and activated KCs during sclerosing cholangitis does not affect disease outcome in mice.

Targeting innate immune responses to attenuate acetaminophen-induced hepatotoxicity

Acetaminophen (APAP) hepatotoxicity is an important cause of acute liver failure, resulting in massive deaths in many developed countries. Currently, the metabolic process of APAP in the body has been well studied. However, the underlying mechanism of APAP-induced liver injury remains elusive. Increasing clinical and experimental evidences indicate that the innate immune responses are involved in the pathogenesis of APAP-induced acute liver injury (AILI), in which immune cells have dual roles of inducing inflammation to exacerbate hepatotoxicity and removing dead cells and debris to help liver regeneration. In this review, we summarize the latest findings of innate immune cells involved in AILI, particularly emphasizing the activation of innate immune cells and their different roles during the injury and repair phases. Moreover, current available treatments are discussed according to the different roles of innate immune cells in the development of AILI. This review aims to update the knowledge about innate immune responses in the pathogenesis of AILI, and provide potential therapeutic interventions for AILI.

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.