Reclassifying Hepatic Cell Death during Liver Damage:Ferroptosis-A Novel Form of Non-Apoptotic Cell Death?

Ferroptosis has emerged as a new type of cell death in different pathological conditions, including neurological and kidney diseases and, especially, in different types of cancer. The hallmark of this regulated cell death is the presence of iron-driven lipid peroxidation; the activation of key genes related to this process such as glutathione peroxidase-4 (gpx4), acyl-CoA synthetase long-chain family member-4 (acsl4), carbonyl reductase [NADPH] 3 (cbr3), and prostaglandin peroxidase synthase-2 (ptgs2); and morphological changes including shrunken and electron-dense mitochondria. Iron overload in the liver has long been recognized as both a major trigger of liver damage in different diseases, and it is also associated with liver fibrosis. New evidence suggests that ferroptosis might be a novel type of non-apoptotic cell death in several liver diseases including non-alcoholic steatohepatitis (NASH), alcoholic liver disease (ALD), drug-induced liver injury (DILI), viral hepatitis, and hemochromatosis. The interaction between iron-related lipid peroxidation, cellular stress signals, and antioxidant systems plays a pivotal role in the development of this novel type of cell death. In addition, integrated responses from lipidic mediators together with free iron from iron-containing enzymes are essential to understanding this process. The presence of ferroptosis and the exact mechanisms leading to this non-apoptotic type of cell death in the liver remain scarcely elucidated. Recognizing ferroptosis as a novel type of cell death in the liver could lead to the understanding of the complex interaction between different types of cell death, their role in progression of liver fibrosis, the development of new biomarkers, as well as the use of modulators of ferroptosis, allowing improved theranostic approaches in the clinic

The role of innate cells is coupled to a Th1-polarized immune response in pediatric nonalcoholic steatohepatitis

Background: Nonalcoholic steatohepatitis (NASH) is a chronic inflammatory liver disease influenced by risk factors for the metabolic syndrome. In adult patients, NASH is associated with an altered phenotype and functionality of peripheral immune cells, the recruitment of leukocytes and intrahepatic activation, and an exacerbated production of reactive oxygen species (ROS) and cytokines. It remains unclear if the previously described differences between pediatric and adult nonalcoholic fatty liver diseases also reflect differences in their pathogenesis. Aims: We aimed to investigate the phenotype and functionality of circulating immune cells and the potential contribution of liver infiltrating leukocytes to the immunological imbalance in pediatric NASH. Results: By a real-time PCR-based analysis of cytokines and immunohistochemical staining of liver biopsies, we demonstrated that the hepatic microenvironment is dominated by interferon-gamma (IFN-γ) but not interleukin-4 and is infiltrated by a higher number of CD8 + cells in pediatric NASH. The number of infiltrating neutrophils positively correlated with ROS generation by peripheral polymorphonuclear cells. By a flow cytometric analysis of peripheral blood lymphocytes, a distinctive increase in CD8 + CD45RO and CD8 + CD45RA subpopulations and an increased production of IFN-γ by CD4 + and CD8 + cells were shown. The production of ROS following PMA stimulation was augmented in circulating neutrophils but not in monocytes. Conclusion: In sum, the distinctive phenotype and functionality of infiltrating and circulating cells suggest that the role of innate cells is coupled to a Th1-polarized immune response in pediatric NASH.Fil: Ferreyra Solari, Nazarena Eugenia. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín. Laboratorio de Inmunogenética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Inzaugarat, Maria Eugenia. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín. Laboratorio de Inmunogenética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Baz, Placida. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín. Laboratorio de Inmunogenética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: de Matteo, Elena Noemí. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lezama, Carol. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; ArgentinaFil: Galoppo, Marcela. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; ArgentinaFil: Galoppo, María Cristina. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; ArgentinaFil: Cherñavsky, Alejandra Claudia. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín. Laboratorio de Inmunogenética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; Argentin

New evidence for the therapeutic potential of curcumin to treat nonalcoholic fatty liver disease in humans.

INTRODUCTION:The immune system acts on different metabolic tissues that are implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Leptin and linoleic acid have the ability to potentially affect immune cells, whereas curcumin is a known natural polyphenol with antioxidant and anti-inflammatory properties. AIMS:This study was designed to evaluate the pro-inflammatory and pro-oxidant effects of leptin and linoleic acid on immune cells from patients with NAFLD and to corroborate the modulatory effects of curcumin and its preventive properties against the progression of NAFLD using a high-fat diet (HFD)-induced NAFLD/nonalcoholic steatohepatitis mouse model. RESULTS:The ex vivo experiments showed that linoleic acid increased the production of reactive oxygen species in monocytes and liver macrophages, whereas leptin enhanced tumor necrosis factor-α (TNF-α) production in monocytes and interferon-γ production in circulating CD4+ cells. Conversely, oral administration of curcumin prevented HFD-induced liver injury, metabolic alterations, intrahepatic CD4+ cell accumulation and the linoleic acid- and leptin- induced pro-inflammatory and pro-oxidant effects on mouse liver macrophages. CONCLUSION:Our findings provide new evidence for the therapeutic potential of curcumin to treat human NAFLD. However, the development of a preventive treatment targeting human circulating monocytes and liver macrophages as well as peripheral and hepatic CD4+ cells requires additional research

Effect of linoleic acid on reactive oxygen species production in human monocytes and liver macrophages.

<p>(A) The stimulation index for reactive oxygen species production in monocytes was higher in patients with NAFLD (n = 12) than in control subjects (n = 10). The box and whiskers indicate the non-parametric statistics: the median, lower and upper quartiles and confidence interval around the median. A two-tailed Mann-Whitney U test was used; *p = 0.036. (B) DCF-MFI, 2', 7’-dichlorofluorescein median fluorescence intensity. Linoleic acid increased reactive oxygen species production in liver macrophages from patients with NAFLD (n = 12). Lines connect the “Basal” and “Linoleic acid” values for each patient. A Wilcoxon matched-pairs signed rank test was performed; *p = 0.001. (C) The stimulation index in monocytes and liver macrophages from patients with NAFLD were positively correlated. Spearman´s rank correlation coefficients test was used.</p

Curcumin effects on linoleic acid- and leptin-induced the production of reactive oxygen species and cytokines as well as the infiltration of CD4⁺ cells in HFD-fed mice.

<p><b>(A)</b> After they were treated with linoleic acid ex vivo, liver macrophages from HFD-fed mice showed a higher stimulation index for reactive oxygen species production (*p<0.05 vs. normal chow-fed mice). In vivo curcumin administration of HFD-fed mice (HFD+curcumin) prevented the increase in the stimulation index (*p<0.05 vs. HFD-fed mice). <b>(B)</b> Ex vivo linoleic acid stimulation of hepatocytes from all the experimental groups resulted in similar stimulation indexes for reactive oxygen species production. <b>(C)</b> TNF-α production induced by ex vivo leptin treatment was higher in liver macrophages from HFD-fed mice (*p<0.05 vs. normal chow-fed mice). In vivo curcumin treatment of HFD-fed mice also prevented the increase in TNF- α production (*p<0.05, HFD+curcumin vs. HFD). <b>(D)</b> The percentage of CD4⁺ cells among the non-parenchymal cell populations was higher in HFD-fed mice (*p<0.01 vs. normal chow-fed mice). In vivo curcumin treatment also prevented the increase in CD4⁺ cell recruitment (*p<0.01, HFD+curcumin vs. HFD). The box and whiskers show the non-parametric statistics: the median, lower and upper quartiles and confidence interval around the median. The Kruskal-Wallis test with Dunn’s post-test was performed.</p

The reversal effects of curcumin on peripheral immunological cells.

<p>Ex vivo curcumin treatment of PBMCs from patients with NAFLD resulted in decreases in <b>(A)</b> linoleic acid-induced reactive oxygen species generation (n = 9, *p = 0.011) and <b>(B)</b> leptin-induced TNF-α production (n = 9, *p = 0.016) by monocytes. <b>(C)</b> Ex vivo curcumin treatment of PBMCs from patients with NAFLD resulted in decreased IFN-γ production in CD4⁺ cells (n = 9, *p = 0.048). Lines connect the “Linoleic acid” and “Linoleic acid+Curcumin” stimulation indexes or the “Leptin” and "Leptin+Curcumin" fold of increase indexes for each patient. A Wilcoxon matched-pairs signed rank test was performed.</p

Effect of leptin on TNF-α and reactive oxygen species production in human monocytes.

<p>(A) The fold of increase index for TNF-α production was higher in monocytes from patients with NAFLD (n = 10) than those from control subjects (n = 10); however, when monocytes were stimulated with leptin, the stimulation index for reactive oxygen species production (B) was similar in patients with NAFLD (n = 10) and control subjects (n = 10). The box and whiskers indicate the non-parametric statistics: median, lower and upper quartiles and confidence interval around the median. A two-tailed Mann-Whitney U test was used, *p = 0.004.</p

Diagram of the experimental design.

<p>Experimental design using human peripheral blood mononuclear cells (PBMCs), human or mouse liver cells. PMA: phorbol myristate acetate, H₂DCFDA: 2’7’-dichlorofluorescein diacetate.</p

Demographic, anthropometric and biochemical baseline data of patients with NAFLD and control individuals.

<p>Demographic, anthropometric and biochemical baseline data of patients with NAFLD and control individuals.</p

The effects of leptin on IFN-γ production and T cell-associated alterations in liver samples from patients with NAFLD.

<p>(A) The fold of increase index for IFN-γ production in leptin-stimulated circulating CD4⁺ cells was higher in patients with NAFLD (n = 10) than in control subjects (n = 10; *p = 0.011). <b>(B)</b> The percentage of CD4⁺ cells among the total non-parenchymal cell population was higher in patients with NAFLD (n = 10) than in control subjects (n = 10), *p = 0.030. <b>(C)</b> Compared with control subjects (n = 9), patients with NAFLD (n = 9) showed increased hepatic mRNA expression levels of IFN-γ (*p = 0.012), T-bet (*p = 0.020) and CCL20 (*p = 0.007) as measured by quantitative PCR. The 2^-ΔΔCt method was used to calculate the mRNA fold change. The box and whiskers indicate the non-parametric statistics: the median, lower and upper quartiles and confidence interval around the median. A two-tailed Mann-Whitney U test was used for the statistical analysis.</p