Involvement of regional neutrophil apoptosis promotion by ribosomal protein S19 oligomers in resolution of experimental acute inflammation

Dissecting the immune discrepancies in mouse liver allograft tolerance and heart/kidney allograft rejection

The liver is the most tolerogenic of transplanted organs. However, the mechanisms underlying liver transplant tolerance are not well understood. The comparison between liver transplantation tolerance and heart/kidney transplantation rejection will deepen our understanding of tolerance and rejection in solid organs. Here, we built a mouse model of liver, heart and kidney allograft and performed single-cell RNA sequencing of 66,393 cells to describe the cell composition and immune cell interactions at the early stage of tolerance or rejection. We also performed bulk RNA-seq of mouse liver allografts from Day 7 to Day 60 post-transplantation to map the dynamic transcriptional variation in spontaneous tolerance. The transcriptome of lymphocytes and myeloid cells were characterized and compared in three types of organ allografts. Cell-cell interaction networks reveal the coordinated function of Kupffer cells, macrophages and their associated metabolic processes, including insulin receptor signalling and oxidative phosphorylation in tolerance induction. Cd11b+ dendritic cells (DCs) in liver allografts were found to inhibit cytotoxic T cells by secreting anti-inflammatory cytokines such as Il10. In summary, we profiled single-cell transcriptome analysis of mouse solid organ allografts. We characterized the immune microenvironment of mouse organ allografts in the acute rejection state (heart, kidney) and tolerance state (liver).

Ribosomal protein small subunit 15A (RPS15A) inhibits the apoptosis of breast cancer MDA-MB-231 cells via upregulating phosphorylated ERK1/2, Bad, and Chk1

AIM

To detect the expression and identify the role of Ribosomal protein S15A (RPS15A) in human breast cancer (BC).

METHODS

Immunohistochemistry (IHC) was carried out for detecting the levels of RPS15A protein. Quantitative PCR was used to evaluate the mRNA level of RPS15A in one normal breast and three BC cell lines. Lentivirus-mediated shRNA targeting RPS15A was designed to investigate the impact of silencing RPS15A in MDA-MB-231 cell.

RESULTS

Higher RPS15A expression was detected in tumor tissues than in para-cancer tissues, and higher RPS15A expression was related to larger tumor size and higher TNM stage. Also, RPS15A mRNA expression in all three BC cell lines was higher than that in normal breast cell (all P < .005). Further, RPS15A knockdown significantly suppressed MDA-MB-231 cell proliferation and induced apoptosis. Moreover, RPS15A knockdown increased the caspase-3/-7 activity, and suppressed the phosphorylated levels of ERK1/2, Bad, and Chk1 (all P < .01).

CONCLUSION

RPS15A inhibits apoptosis via upregulating phosphorylated ERK1/2, Bad, and Chk1 in MDA-MB-231 cell line.

The roles of a ribosomal protein S19 polymer in a mouse model of carrageenan-induced acute pleurisy

C5-deficient mice usually present moderate neutrophil activation during the initiation phase of acute inflammation. Conversely, C5a receptor (C5aR)-deficient mice show unusually excessive activation of neutrophils. We identified the ribosomal protein S19 (RP S19) polymer, which is cross-linked at Lys122 and Gln137 by transglutaminases in apoptotic neutrophils, as a second C5aR ligand during the resolution phase of acute inflammation. The RP S19 polymer promotes apoptosis via the neutrophil C5aR and phagocytosis via the macrophage C5aR. To confirm the roles of the RP S19 polymer, we employed a carrageenan-induced acute pleurisy mouse model using C57BL/6J mice with a knock-in of the Gln137Glu mutant RP S19 gene and replaced the RP S19 polymer with either an S-tagged C5a/RP S19 recombinant protein or the RP S19^122-145 peptide monomer and dimer (as functional C5aR agonists/antagonists) and the RP S19^122-145 peptide trimer (as a functional C5aR antagonist). Neutrophils and macrophages were still present in the thoracic cavities of the knock-in mice at 24h and 7days after carrageenan injection, respectively. Knock-in mice showed structural organization and severe hemorrhaging from the surrounding small vessels of the alveolar walls in the lung parenchyma. In contrast to the RP S19^122-145 peptide monomer and trimer, the simultaneous presence of S-tagged C5a/RP S19 and the RP S19^122-145 peptide dimer completely improved the physiological and pathological acute inflammatory cues. The RP S19 polymer, especially the dimer, appears to play a role at the resolution phase of carrageenan-induced acute pleurisy in C57BL/6J model mice.

Effects of ghrelin on the apoptosis of human neutrophils in vitro

Acute respiratory distress syndrome (ARDS) is characterized by lung inflammation and the diffuse infiltration of neutrophils into the alveolar space. Neutrophils are abundant, short-lived leukocytes that play a key role in immune defense against microbial infections. These cells die via apoptosis following the activation and uptake of microbes, and will also enter apoptosis spontaneously at the end of their lifespan if they do not encounter pathogens. Apoptosis is essential for the removal of neutrophils from inflamed tissues and for the timely resolution of neutrophilic inflammation. Ghrelin is an endogenous ligand for the growth hormone (GH) secretagogue receptor, produced and secreted mainly from the stomach. Previous studies have reported that ghrelin exerts anti-inflammatory effects in lung injury through the regulation of the apoptosis of different cell types; however, the ability of ghrelin to regulate alveolar neutrophil apoptosis remains largely undefined. We hypothesized that ghrelin may have the ability to modulate neutrophil apoptosis. In this study, to examine this hypothesis, we investigated the effects of ghrelin on freshly isolated neutrophils in vitro. Our findings demonstrated a decrease in the apoptotic ratio (as shown by flow cytometry), as well as in the percentage of cells with decreased mitochondrial membrane potential (ΔΨm) and in the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling-positive rate, accompanied by an increased B-cell lymphoma 2/Bax ratio and the downregulation of cleaved caspase-3 in neutrophils following exposure to lipopolysaccharide (100 ng/ml). However, pre-treatment with ghrelin at a physiological level (100 nM) did not have a notable influence on the neutrophils in all the aforementioned tests. Our findings suggest that ghrelin may not possess the ability to modulate the neutrophil lifespan in vitro.

Neutrophil proteomic analysis reveals the participation of antioxidant enzymes, motility and ribosomal proteins in the prevention of ischemic effects by preconditioning

Intestinal ischemia and reperfusion injury are widely used models, which result into tissue injury and multiple organ failure also observed after trauma and surgery. Ischemic preconditioning (IPC) preceding ischemia and reperfusion (IR) was shown to attenuate this injury and has a potential therapeutic application; however the exact underlying mechanism is not clear. Neutrophils play an important role in the mechanism of injuries caused by ischemia and reperfusion while IPC led to a decrease in neutrophil stimulation and activation. The effect of preconditioning on the neutrophil proteome is unclear. Proteomic analysis has been ratified as an appropriate tool for studying complex systems. In order to evaluate the effect of IPC preceding 45min of ischemia on the proteome of neutrophils we used Wistar rats divided in four experimental groups: Control, sham laparotomy, intestinal ischemia reperfusion and ischemic preconditioning. After neutrophil separation, proteins were extracted, trypsin digested and the resulting peptides were iTRAQ labeled followed by HILIC fractionation and nLC-MS/MS analysis. After database searches, normalization and statistical analysis our proteomic analysis resulted in the identification of 2437 protein groups that were assigned to five different clusters based on the relative abundance profiles among the experimental groups. The clustering followed by statistical analysis led to the identification of significantly up and downregulated proteins in IR and IPC. Cluster based KEGG pathways analysis revealed up- regulation of actin cytoskeleton, metabolism, Fc gamma R mediated phagocytosis, chemokine signaling, focal adhesion and leukocyte transendothelial migration whereas downregulation in ribosome, spliceosome, RNA transport, protein processing in endoplasmic reticulum and proteasome, after intestinal ischemic preconditioning. Furthermore, enzyme prediction analysis revealed the regulation of some important antioxidant enzymes and having their role in reactive oxygen species production. To our knowledge, this work describes the most comprehensive and detailed quantitative proteomic study of the neutrophil showing the beneficial role of ischemic preconditioning and its effects on the neutrophil proteome. This data will be helpful to understand the effect of underlying protective mechanisms modulating the role of PMNs after IPC and provide a trustworthy basis for future studies.

BIOLOGICAL SIGNIFICANCE

Preconditioning is a relevant strategy to overcome clinical implications from ischemia and reperfusion. Such implications have the neutrophil as a major player. Although many publications describe specific biochemical and physiological roles of the neutrophil in such conditions, there is no report of a proteomic study providing a broader view of this scenario. Here we describe a group of proteins significantly regulated by ischemia and reperfusion being such regulation prevented by preconditioning. Such finding may provide relevant information for a deeper understanding of the mechanisms involved, as well as serve as basis for future biomarker or drug target assays.

The effect of ribosomal protein S15a in lung adenocarcinoma

Background: RPS15A (Ribosomal Protein S15A) promotes mRNA/ribosome interactions in translation. It is critical for the process of eukaryotic protein biosynthesis. Recently, aberrantly expressed RPS15A was found in the hepatitis virus and in malignant tumors. However, the role of RPS15A has not been fully revealed on the development of lung cancer. Method: In this study, a Tissue Microarray (TMA) of primary lung adenocarcinoma tissue specimens was carried out. Furthermore, to further investigate the function of RPS15A in lung cancer, RPS15A-specific short hairpin RNA (shRNA) expressing lentivirus (Lv-shRPS15A) was constructed and used to infect H1299 and A549 cells. Result: Our data showed that RPS15A expression was increased in tumor tissues. Furthermore, the knockdown of RSP15A inhibited cancer cell growth and induced apoptosis in the cancer cells. Gene expression profile microarray also revealed that the P53 signaling pathway was activated in Lv-shRPS15A-infected cancer cells. Conclusion: Taken together, our results demonstrate that RPS15A is a novel oncogene in non-small cell lung cancer and may be a potential therapeutic target in lung cancer.

Role of blood ribosomal protein S19 in coagulum resorption: a study using Gln137Glu-ribosomal protein S19 gene knock-in mouse

Sera of human, guinea pig or mouse contain a strong monocyte chemoattractant capacity that is attributed to the ribosomal protein S19 (RP S19) oligomers generated during blood coagulation. In contrast, sera prepared from Gln137Glu-RP S19 gene knock-in mice contained negligible chemoattractant capacity. When coagula that had been pre-formed from the blood of both the wild type and knock-in mice were intraperitoneally inserted into host mice, after 3 days of recovery, the knock-in mouse coagula remained larger than the wild type mouse coagula. The wild type mouse coagula were covered by multiple macrophage layers at the surface and were infiltrated inside by macrophages. Knock-in mouse coagula exhibited less macrophage involvement. When coagula of knock-in mice and coagula of knock-in mice containing C5a/RP S19, an artificial substitute of the RP S19 oligomers, were intraperitoneally inserted as pairs, the C5a/RP S19 containing coagulum was more rapidly absorbed, concomitant with increased macrophage involvement. Finally, when the knock-in mouse and wild type mouse coagula pairs were inserted into mice in which macrophages had been depleted using clodronate liposome, the size difference of recovered coagula was reversed. These results indicate the importance of the RP S19 oligomer-induced macrophage recruitment in coagulum resorption.