Albumin internalizes and inhibits endosomal TLR signaling in leukocytes from patients with decompensated cirrhosis

Leukocyte endosomal trafficking plays a critical role in the anti-inflammatory actions of human albumin. Taking an immune look into decompensated cirrhosis In patients with acutely decompensated cirrhosis, human serum albumin (HSA) administration has been shown to reduce inflammation in patients; however, the mechanisms underlying treatment efficacy are unclear. Now, Casulleras et al. used peripheral blood leukocytes from patients and showed that HSA inhibited cytokine production induced by CpG-DNA. HSA was taken up by leukocytes and localized in endosomes, where it inhibited Toll-like receptor signaling. The results suggest that leukocytes play a critical role in the effect of HSA and offer an alternative perspective for understanding the pathophysiology of acutely decompensated cirrhosis. Human serum albumin (HSA) is an emerging treatment for preventing excessive systemic inflammation and organ failure(s) in patients with acutely decompensated (AD) cirrhosis. Here, we investigated the molecular mechanisms underlying the immunomodulatory properties of HSA. Administration of HSA to patients with AD cirrhosis with elevated circulating bacterial DNA rich in unmethylated cytosine-phosphate-guanine dideoxynucleotide motifs (CpG-DNA) was associated with reduced plasma cytokine concentrations. In isolated leukocytes, HSA abolished CpG-DNA–induced cytokine expression and release independently of its oncotic and scavenging properties. Similar anti-inflammatory effects were observed with recombinant human albumin. HSA exerted widespread changes on the immune cell transcriptome, specifically in genes related to cytokines and type I interferon responses. Our data revealed that HSA was taken up by leukocytes and internalized in vesicles positively stained with early endosome antigen 1 and colocalized with CpG-DNA in endosomes, where the latter binds to Toll-like receptor 9 (TLR9), its cognate receptor. Furthermore, HSA also inhibited polyinosinic:polycytidylic acid– and lipopolysaccharide-induced interferon regulatory factor 3 phosphorylation and TIR domain–containing adapter-inducing interferon-β–mediated responses, which are exclusive of endosomal TLR3 and TLR4 signaling, respectively. The immunomodulatory actions of HSA did not compromise leukocyte defensive mechanisms such as phagocytosis, efferocytosis, and intracellular reactive oxygen species production. The in vitro immunomodulatory effects of HSA were confirmed in vivo in analbuminemic humanized neonatal Fc receptor transgenic mice. These findings indicate that HSA internalizes in immune cells and modulates their responses through interaction with endosomal TLR signaling, thus providing a mechanism for the benefits of HSA infusions in patients with cirrhosis.

[1]  R. Moreau,et al.  Albumin in decompensated cirrhosis: new concepts and perspectives , 2020, Gut.

[2]  R. Moreau,et al.  Effects of Albumin Treatment on Systemic and Portal Hemodynamics and Systemic Inflammation in Patients With Decompensated Cirrhosis. , 2019, Gastroenterology.

[3]  R. Stauber,et al.  Oxidized albumin triggers a cytokine storm in leukocytes through p38 MAP kinase: role in systemic inflammation in decompensated cirrhosis. , 2018 .

[4]  R. Stauber,et al.  Oxidized Albumin Triggers a Cytokine Storm in Leukocytes Through P38 Mitogen‐Activated Protein Kinase: Role in Systemic Inflammation in Decompensated Cirrhosis , 2018, Hepatology.

[5]  A. Gasbarrini,et al.  Long-term albumin administration in decompensated cirrhosis (ANSWER): an open-label randomised trial , 2018, The Lancet.

[6]  A. Chakravarti,et al.  Caveolae-Mediated Endocytosis Is Critical for Albumin Cellular Uptake and Response to Albumin-Bound Chemotherapy. , 2017, Cancer research.

[7]  J. Cameron,et al.  Direct demonstration of a neonatal Fc receptor (FcRn)-driven endosomal sorting pathway for cellular recycling of albumin , 2017, The Journal of Biological Chemistry.

[8]  J. Wan,et al.  Type I interferon signaling in systemic immune cells from patients with alcoholic cirrhosis and its association with outcome. , 2017, Journal of hepatology.

[9]  Joel Babdor,et al.  IRAP+ endosomes restrict TLR9 activation and signaling , 2017, Nature Immunology.

[10]  J. Andersen,et al.  Hepatic FcRn regulates albumin homeostasis and susceptibility to liver injury , 2017, Proceedings of the National Academy of Sciences.

[11]  R. Moreau,et al.  The Acute-on-Chronic Liver Failure Syndrome, or When the Innate Immune System Goes Astray , 2016, The Journal of Immunology.

[12]  Richard Moreau,et al.  Systemic inflammation in decompensated cirrhosis: Characterization and role in acute‐on‐chronic liver failure , 2016, Hepatology.

[13]  P. Kamath,et al.  Acute-on-chronic liver failure in cirrhosis , 2016, Nature Reviews Disease Primers.

[14]  Yuquan Wei,et al.  Mitochondrial DNA in the regulation of innate immune responses , 2015, Protein & Cell.

[15]  Inger Sandlie,et al.  Unraveling the Interaction between FcRn and Albumin: Opportunities for Design of Albumin-Based Therapeutics , 2015, Front. Immunol..

[16]  M. Álvarez-Mon,et al.  Cirrhosis-associated immune dysfunction: distinctive features and clinical relevance. , 2014, Journal of hepatology.

[17]  X. Salvatella,et al.  Human serum albumin, systemic inflammation, and cirrhosis. , 2014, Journal of hepatology.

[18]  G. Barton,et al.  Trafficking of endosomal Toll-like receptors. , 2014, Trends in cell biology.

[19]  R. Doctor,et al.  Human podocytes perform polarized, caveolae-dependent albumin endocytosis. , 2014, American journal of physiology. Renal physiology.

[20]  Sandra Romero-Steiner,et al.  Molecular signatures of antibody responses derived from a systems biological study of 5 human vaccines , 2013, Nature Immunology.

[21]  Simon C Watkins,et al.  Caveolae-Dependent and -Independent Uptake of Albumin in Cultured Rodent Pulmonary Endothelial Cells , 2013, PloS one.

[22]  R. Moreau,et al.  Acute-on-chronic liver failure is a distinct syndrome that develops in patients with acute decompensation of cirrhosis. , 2013, Gastroenterology.

[23]  P. Angeli,et al.  Positive cardiac inotropic effect of albumin infusion in rodents with cirrhosis and ascites: molecular mechanisms , 2013, Hepatology.

[24]  Shi Xu,et al.  Targeting receptor-mediated endocytotic pathways with nanoparticles: rationale and advances. , 2013, Advanced drug delivery reviews.

[25]  G. Barton,et al.  Compartment-Specific Control of Signaling from a DNA-Sensing Immune Receptor , 2010, Science Signaling.

[26]  J. McIntosh,et al.  FcRn-mediated antibody transport across epithelial cells revealed by electron tomography , 2008, Nature.

[27]  A. Velasco,et al.  Megalin is a receptor for albumin in astrocytes and is required for the synthesis of the neurotrophic factor oleic acid , 2008, Journal of neurochemistry.

[28]  C. Watts Location, location, location: identifying the neighborhoods of LPS signaling , 2008, Nature Immunology.

[29]  R. Yumoto,et al.  Comparison of Albumin Uptake in Rat Alveolar Type II and Type I-like Epithelial Cells in Primary Culture , 2008, Pharmaceutical Research.

[30]  R. Yumoto,et al.  Clathrin-mediated endocytosis of FITC-albumin in alveolar type II epithelial cell line RLE-6TN. , 2006, American journal of physiology. Lung cellular and molecular physiology.

[31]  Didier Auboeuf,et al.  FAST DB: a website resource for the study of the expression regulation of human gene products , 2005, Nucleic acids research.

[32]  Craig J McClain,et al.  Albumin therapy in clinical practice. , 2005, Nutrition in clinical practice : official publication of the American Society for Parenteral and Enteral Nutrition.

[33]  D. Klinman Immunotherapeutic uses of CpG oligodeoxynucleotides , 2004, Nature Reviews Immunology.

[34]  B. Monks,et al.  TLR9 signals after translocating from the ER to CpG DNA in the lysosome , 2004, Nature Immunology.

[35]  R. Flavell,et al.  Recognition of double-stranded RNA and activation of NF-κB by Toll-like receptor 3 , 2001, Nature.

[36]  S. Akira,et al.  A Toll-like receptor recognizes bacterial DNA , 2000, Nature.

[37]  M. Navasa,et al.  Effect of intravenous albumin on renal impairment and mortality in patients with cirrhosis and spontaneous bacterial peritonitis. , 1999, The New England journal of medicine.

[38]  G. Bishop,et al.  CpG motifs in bacterial DNA trigger direct B-cell activation , 1995, Nature.

[39]  C. Stevens,et al.  Aquaporin 4 and glymphatic flow have central roles in brain fluid homeostasis , 2021, Nature Reviews Neuroscience.

[40]  J. Llach,et al.  Randomized comparative study of therapeutic paracentesis with and without intravenous albumin in cirrhosis. , 1988, Gastroenterology.

[41]  Sandra Romero-Steiner,et al.  Molecular signatures of antibody responses derived from a systems biology study of five human vaccines , 2022 .