Selective Targeting of α4ß7/MAdCAM-1 Axis Suppresses Fibrosis Progression by Reducing Proinflammatory T Cell Recruitment to the Liver.

Integrin α4ß7+ T cells perpetuate tissue injury in chronic inflammatory diseases, yet their role in hepatic fibrosis progression remains poorly understood. Here, we report increased accumulation of α4ß7+ T cells in the liver of people with cirrhosis relative to disease controls. Similarly, hepatic fibrosis in the established mouse model of CCl4-induced liver fibrosis was associated with enrichment of intrahepatic α4ß7+ CD4 and CD8 T cells. Monoclonal antibody (mAb)-mediated blockade of α4ß7 or its ligand mucosal addressin cell adhesion molecule (MAdCAM)-1 attenuated hepatic inflammation and prevented fibrosis progression in CCl4-treated mice. Improvement in liver fibrosis was associated with a significant decrease in the infiltration of α4ß7+ CD4 and CD8 T cells, suggesting that α4ß7/MAdCAM-1 axis regulates both CD4 and CD8 T cell recruitment to the fibrotic liver, and α4ß7+ T cells promote hepatic fibrosis progression. Analysis of hepatic α4ß7+ and α4ß7- CD4 T cells revealed that α4ß7+ CD4 T cells were enriched for markers of activation and proliferation, demonstrating an effector phenotype. The findings suggest that α4ß7+ T cells play a critical role in promoting hepatic fibrosis progression, and mAb-mediated blockade of α4ß7 or MAdCAM-1 represents a promising therapeutic strategy for slowing hepatic fibrosis progression in chronic liver diseases.

Selective targeting of α 4 ß 7 /MAdCAM-1 axis suppresses liver fibrosis by reducing proinflammatory T cell recruitment to the liver.

Integrin α 4 ß 7 + T cells perpetuate tissue injury in chronic inflammatory diseases, yet their role in hepatic fibrosis progression remains poorly understood. Here we report increased accumulation of α 4 ß 7 + T cells in the liver of people with cirrhosis relative to disease controls. Similarly, hepatic fibrosis in the established mouse model of CCl 4 -induced liver fibrosis was associated with enrichment of intrahepatic α 4 ß 7 + CD4 and CD8 T cells. Monoclonal antibody (mAb)-mediated blockade of α 4 ß 7 or its ligand mucosal addressin cell adhesion molecule (MAdCAM)-1 attenuated hepatic inflammation and prevented fibrosis progression in CCl 4 treated mice. Improvement in liver fibrosis was associated with a significant decrease in the infiltration of α 4 ß 7 + CD4 and CD8 T cells suggesting that α 4 ß 7 /MAdCAM-1 axis regulates both CD4 and CD8 T cell recruitment to the fibrotic liver, and α 4 ß 7 + T cells promote hepatic fibrosis progression. Analysis of hepatic α 4 ß 7 + and α 4 ß 7 -CD4 T cells revealed that α 4 ß 7 + CD4 T cells enriched for markers of activation and proliferation demonstrating an effector phenotype. Notably, blockade of α 4 ß 7 or MAdCAM-1 did not affect the recruitment of Foxp3+ regulatory T cells, demonstrating the specificity of α 4 ß 7 /MAdCAM-1 axis in regulating effector T cell recruitment to the liver. The findings suggest that α 4 ß 7 + T cells play a critical role in promoting hepatic fibrosis progression, and mAb-mediated blockade of α 4 ß 7 or MAdCAM-1 represents a promising therapeutic strategy for slowing hepatic fibrosis progression in chronic liver diseases.

Western diet dampens T regulatory cell function to fuel hepatic inflammation in nonalcoholic fatty liver disease.

Background and aims: The immunosuppressive T regulatory cells (Tregs) regulate immune responses and maintain immune homeostasis, yet their functions in nonalcoholic fatty liver disease (NAFLD) pathogenesis remains controversial. Methods: Mice were fed a normal diet (ND) or a western diet (WD) for 16 weeks to induce NAFLD. Diphtheria toxin injection to deplete Tregs in Foxp3 DTR mice or Treg induction therapy in WT mice to augment Treg numbers was initiated at twelve and eight weeks, respectively. Liver tissues from mice and NASH human subjects were analyzed by histology, confocal imaging, and qRT-PCR. Results: WD triggered accumulation of adaptive immune cells, including Tregs and effector T cells, within the liver parenchyma. This pattern was also observed in NASH patients, where an increase in intrahepatic Tregs was noted. In the absence of adaptive immune cells in Rag1 KO mice, WD promoted accumulation of intrahepatic neutrophils and macrophages and exacerbated hepatic inflammation and fibrosis. Similarly, targeted Treg depletion exacerbated WD-induced hepatic inflammation and fibrosis. In Treg-depleted mice, hepatic injury was associated with increased accumulation of neutrophils, macrophages, and activated T cells within the liver. Conversely, induction of Tregs using recombinant IL2/αIL2 mAb cocktail reduced hepatic steatosis, inflammation, and fibrosis in WD-fed mice. Analysis of intrahepatic Tregs from WD-fed mice revealed a phenotypic signature of impaired Treg function in NAFLD. Ex vivo functional studies showed that glucose and palmitate, but not fructose, impaired the immunosuppressive ability of Treg cells. Conclusions: Our findings indicate that the liver microenvironment in NAFLD impairs ability of Tregs to suppress effector immune cell activation, thus perpetuating chronic inflammation and driving NAFLD progression. These data suggest that targeted approaches aimed at restoring Treg function may represent a potential therapeutic strategy for treating NAFLD. Lay summary: In this study, we elucidate the mechanisms contributing to the perpetuation of chronic hepatic inflammation in nonalcoholic fatty liver disease (NAFLD). We show that dietary sugar and fatty acids promote chronic hepatic inflammation in NAFLD by impairing immunosuppressive function of regulatory T cells. Finally, our preclinical data suggest that targeted approaches aimed at restoring T regulatory cell function have the potential to treat NAFLD.

Hyperoxidized Albumin Modulates Platelets and Promotes Inflammation Through CD36 Receptor in Severe Alcoholic Hepatitis.

Hyperoxidized albumin promotes inflammation and modulates several immune cells in severe alcoholic hepatitis (SAH). Platelets mediate inflammation by interacting with immune cells, endothelium, and other cells. The role of hyperoxidized albumin in platelet activation and alteration of platelet phenotype/functions is not known. Quantitative platelet proteomics performed in 10 patients with SAH was compared with 10 patients with alcoholic cirrhosis and 10 healthy controls, respectively. Dysregulated pathways were identified and validated in a separate cohort (n = 40). Healthy platelets were exposed to patient plasma or purified albumin or ex vivo modified albumin (human-mercaptalbumin, humannonmercaptalbumin-1, and human nonmercaptalbumin 2) in the presence or absence of CD36 blockade, and platelet secretome was analyzed. Two hundred and two up-regulated proteins linked to platelet activation, complement regulation, lipid transportation, and 321 down-regulated proteins related to platelet hemostasis and coagulation (fold change ± 1.5, P < 0.01) were identified. Blood transcription module enrichment showed an inflammatory phenotype of SAH platelet. Increased level of platelet factor-4, P-selectin, and soluble cluster of differentiation-40 ligand correlated with severity (Model for End-Stage Liver Disease score, r > 0.3, P < 0.05) in SAH. Transcripts linked to platelet activation (increased) and granular secretions (decreased in SAH) correlated with disease severity. SNARE (soluble-N-ethylmaleimide-sensitive-factor-activating-protein-receptor) complex proteins (SNAP-23 [synaptosomal-associated protein 23] and VAMP-8 [vesicle-associated membrane protein 3]) were down-regulated in SAH platelets (P < 0.05). In vitro stimulation of healthy platelets showed enhanced activation with patient plasma, or purified albumin-treatment blocking of CD36 blunted this effect (P < 0.05). Ex vivo modified albumin (primarily nonmercaptalbumin-human nonmercaptalbumin 2 [HNA2; 1 mg/mL]) showed high activation and aggregation and intracellular reactive oxygen species production in healthy platelets (P < 0.05), which significantly reduced after CD36 neutralization. Platelet secretome showed reduced inflammatory mediators and increased repair proteins. Conclusion: Hyperoxidized albumin triggers platelet activation (possibly through the CD36 receptor), promotes inflammation and oxidative stress, and contributes to disease severity in patients with SAH.

Dysregulated Lipid Transport Proteins Correlate With Pathogenesis and Outcome in Severe Alcoholic Hepatitis.

Severe alcoholic hepatitis (SAH) has high mortality. Dysregulated lipid transport and metabolism in liver/macrophages contributes to disease pathophysiology. Paraoxonase/arylesterase 1 (PON1), a liver-specific enzyme, inhibits oxidation of phospholipids and prevents lipid-mediated oxidative damage. However, its functional contribution in macrophage-mediated hepatic injury warrants elucidation. Plasma proteome of patients with SAH (n = 20), alcoholic cirrhosis (n = 20), and healthy controls was analyzed. Dysregulated pathways were identified, validated, and correlated with severity and outcomes in 200 patients with SAH. Tohoku-Hospital-Pediatrics-1 (THP1)-derived macrophages were treated with plasma from study groups in the presence/absence of recombinant PON1 and the phenotype; intracellular lipid bodies and linked functions were evaluated. In patients with SAH, 208 proteins were >1.5 fold differentially regulated (32 up-regulated and 176 down-regulated; P < 0.01).Validation studies confirmed lower levels of lipid transporter proteins (Pon1, apolipoprotein [Apo]B, ApoA1, ApoA2, and ApoC3; P < 0.01). Low PON1 levels inversely correlated with severity and mortality (r2 > 0.3; hazard ratio, 0.91; P < 0.01) and predicted nonsurvivors (area under the receiver operating characteristic curve, 0.86; cut-off, <18 µg/mL; log rank, <0.01). Low PON1 levels corroborated with increased oxidized low-density lipoprotein levels, intracellular lipid bodies, lipid uptake, lipid metabolism, biosynthesis, and alternative macrophage activation genes in nonsurvivors (P < 0.01). Importantly, in vitro recombinant PON1 treatment on THP1 macrophages reversed these changes (P < 0.01), specifically by alteration in expression of clusters of differentiation 36 (CD36) and adenosine triphosphate-binding cassette subfamily A1 (ABCA1) receptor on macrophages. Conclusion: Lipid transport proteins contribute to the pathogenesis of SAH, and low PON1 levels inversely correlate with the severity of alcoholic hepatitis and 28-day mortality. Restitution of circulating PON1 may be beneficial and needs therapeutic evaluation in patients with SAH.