interleukin-8 and Anemia--Hemolytic

Hemolytic uremic syndrome (HUS), a vascular disease characterized by hemolytic anemia, thrombocytopenia, and acute renal failure, is caused by enterohemorrhagic Shiga toxin (Stx)-producing bacteria, which mainly affect children. Besides Stx, the inflammatory response mediated by neutrophils (PMN) is essential to HUS evolution. PMN can release neutrophil extracellular traps (NET) composed of DNA, histones, and other proteins. Since NET are involved in infectious and inflammatory diseases, the aim of this work was to investigate the contribution of NET to HUS. Plasma from HUS patients contained increased levels of circulating free-DNA and nucleosomes in comparison to plasma from healthy children. Neutrophils from HUS patients exhibited a greater capacity to undergo spontaneous NETosis. NET activated human glomerular endothelial cells, stimulating secretion of the proinflammatory cytokines IL-6 and IL-8. Stx induced PMN activation as judged by its ability to trigger reactive oxygen species production, increase CD11b and CD66b expression, and induce NETosis in PMN from healthy donors. During HUS, NET can contribute to the inflammatory response and thrombosis in the microvasculature and thus to renal failure. Intervention strategies to inhibit inflammatory mechanisms mediated by PMN, such as NETosis, could have a potential therapeutic impact towards amelioration of the severity of HUS.

Topics: Acute Kidney Injury; Anemia, Hemolytic; Apoptosis; Bacterial Infections; Cells, Cultured; Child; Endothelial Cells; Extracellular Traps; Hemolytic-Uremic Syndrome; Humans; Interleukin-6; Interleukin-8; Kidney; Neutrophil Activation; Neutrophils; Reactive Oxygen Species; Shiga Toxin; Thrombocytopenia

Lysis of RBCs during numerous clinical settings such as severe hemolytic anemia, infection, tissue injury, or blood transfusion releases the endogenous damage-associated molecular pattern, hemoglobin (Hb), into the plasma. The redox-reactive Hb generates cytotoxic reactive oxygen species, disrupting the redox balance and impairing the immune-responsive blood cells. Therefore, it is crucial to understand how the immune system defends against the cytotoxic Hb. We identified a shortcut "capture and quench" mechanism of detoxification of Hb by the monocyte scavenger receptor CD163, independent of the well-known dominant antioxidant, haptoglobin. Our findings support a highly efficient two-pass mechanism of detoxification and clearance of Hb: 1) a direct suppression of Hb-pseudoperoxidase activity by CD163, involving an autocrine loop of CD163 shedding, sequestration of Hb, recycling, and homeostasis of CD163 in human monocytes and 2) paracrine transactivation of endothelial cells by the shedded soluble CD163 (sCD163), which further detoxifies and clears residual Hb. We showed that sCD163 and IgG interact with free Hb in the plasma and subsequently the sCD163-Hb-IgG complex is endocytosed into monocytes via FcγR. The endocytosed sCD163 is recycled to restore the homeostasis of CD163 on the monocyte membrane in an autocrine cycle, whereas the internalized Hb is catabolized. Using ex vivo coculture experiments, we demonstrated that the monocyte-derived sCD163 and IgG shuttle residual plasma Hb into the proximal endothelial cells. These findings suggest that CD163 and IgG collaborate to engage monocytes and endothelial cells in a two-pass detoxification mechanism to mount a systemic defense against Hb-induced oxidative stress.

Topics: Anemia, Hemolytic; Antigens, CD; Antigens, Differentiation, Myelomonocytic; Apoptosis; Cell Line; Cell Survival; Endothelial Cells; Haptoglobins; HEK293 Cells; Hemoglobins; Hemolysis; Humans; Immunoglobulin G; Interleukin-10; Interleukin-8; Membrane Proteins; Monocytes; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Receptors, Cell Surface; Receptors, IgG; RNA Interference; RNA, Small Interfering; Tumor Necrosis Factor-alpha

Several recent studies have reported both the generation of cytokines, including interleukin (IL)-1 beta, IL-6, tumor necrosis factor alpha (TNF-alpha), and IL-8, in the supernatants of stored platelet concentrates (PCs) and the implications of this generation in febrile nonhemolytic transfusion reactions. Prestorage filtration is regarded as highly effective in the prevention of cytokine generation.. Studies evaluated 1) the levels of these cytokines in apheresis PCs during storage, 2) the effects of white cell inactivation by ultraviolet B or gamma-radiation on the generation of cytokines, and 3) the effects of poststorage filtration on cytokine levels. The apheresis PCs were treated by either ultraviolet B radiation (20,000 J/m2), gamma-radiation (30 Gy), or filtration. Samples were collected sequentially on various days after storage. Cytokines were determined by enzyme-linked immunosorbent assay.. The average white cell count in 15 PCs tested was 2.58 +/- 0.7 x 10(6) per mL (range, 0.7-10 x 10(6)/mL). A detectable level of IL-8 was found at 3 days of storage, and the levels of this cytokine increased progressively with increasing storage time, ranging from 1.6 to 35,280 pg per mL on Day 5 and from 2.7 to 83,601 pg per mL on Day 8. Reverse transcriptase-polymerase chain reaction analysis showed that the level of IL-8 paralleled the expression of IL-8 transcripts. The levels of IL-1 beta, IL-6, TNF-alpha, and monocyte chemotactic protein-1 were very low, even on Day 8. Ultraviolet B-radiated PCs failed to generate IL-8, even at 8 days of storage, whereas levels of IL-8 in gamma-radiated PCs were similar to those in nonirradiated PCs. Poststorage filtration of PCs with a negatively charged polyester filter, but not with a positively charged one, markedly reduced the levels of IL-8.. Of the cytokines tested, IL-8 had the most evident generation in apheresis PCs during storage. Prestorage inactivation of white cells by ultraviolet B radiation, but not by gamma-radiation, was effective in preventing the generation of cytokines during the storage of PCs.

Topics: Anaphylatoxins; Anemia, Hemolytic; Blood Platelets; Blood Preservation; Filtration; Gamma Rays; Graft vs Host Disease; Humans; Interleukin-8; Plateletpheresis; RNA, Messenger; Time Factors; Transfusion Reaction; Ultraviolet Rays