Project description:BACKGROUND AND AIMS: The effects of intravenous albumin on lymphocyte perturbations and defective neutrophil anti-microbial functions that characterize patients with acute-on-chronic liver failure (ACLF) are unknown. METHODS: Forty-nine patients admitted for severe acutely decompensated cirrhosis without ACLF were investigated with the use of whole-blood RNA sequencing (RNA-seq) on admission and after a median period of 15 days once they had developed ACLF. Such patients were selected because they follow a steady systemic inflammation course. Thirty patients had received albumin during the progression to ACLF but not the 19 others. Single-cell RNA-seq (scRNA-seq) in peripheral blood mononuclear cells (PBMCs) exposed ex vivo to albumin or vehicle for 2 hours, and assessment of the anti-microbial capacity of neutrophils exposed ex vivo to albumin were performed in additional patients with acutely decompensated cirrhosis. RESULTS: Analysis of whole-blood RNA-seq data revealed that patients who had received albumin exhibited specific upregulation of signatures related to B cells, plasma cells and immunoglobulins; CD4 T cells; myeloid cells; mismatch repair, cell cycle and mitosis; and transcription factors such as c-Myc and E2F family members. The use of scRNA-seq to analyze patients' PBMCs exposed ex vivo to albumin showed increases in signatures related to B cells, myeloid cells, and CD4 T cells. Neutrophils exposed ex vivo to albumin exhibited increased chemotactic and degranulation responses, enhanced phagocytosis, and increased pathogen-destroying swarming functions. CONCLUSIONS: In patients with severe acutely decompensated cirrhosis, albumin rewires transcription in B cells, CD4 T cells and mononuclear myeloid cells, and resets neutrophil anti-microbial functions to normal.
Project description: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 (CpG-DNA) was associated with reduced plasma cytokine levels. 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 the endosomal compartment involved in cytosolic DNA sensing and type I interferon responses. Flow cytometry and confocal microscopy analyses revealed that HSA was taken up by leukocytes and internalized in vesicles positively stained with EEA1, a marker of early endosomes. Indeed, HSA and CpG-DNA colocalized in endosomes, the compartment where CpG-DNA binds to TLR9, its cognate receptor. Furthermore, HSA also inhibited poly-(I:C)- and LPS-induced IRF3 phosphorylation and TRIF-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 ROS production. The in vitro immunomodulatory effects of HSA were confirmed in vivo in analbuminemic humanized FcRn transgenic mice. In conclusion, 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.