ABSTRACT
BACKGROUND: Platelet Toll-like receptor (TLR)2/4 are key players in amplifying the host immune response; however, their role in human megakaryo/thrombopoiesis has not yet been defined. OBJECTIVES: We evaluated whether Pam3CSK4 or lipopolysaccharide (LPS), TLR2/4 ligands respectively, modulate human megakaryocyte development and platelet production. METHODS: CD34+ cells from human umbilical cord were stimulated with LPS or Pam3CSK4 with or without thrombopoietin (TPO). RESULTS: CD34+ cells and megakaryocytes express TLR2 and TLR4 at both RNA and protein level; however, direct stimulation of CD34+ cells with LPS or Pam3CSK4 had no effect on cell growth. Interestingly, both TLR ligands markedly increased TPO-induced CD34+ cell proliferation, megakaryocyte number and maturity, proplatelet and platelet production when added at day 0. In contrast, this synergism was not observed when TLR agonists were added 7 days after TPO addition. Interleukin-6 (IL-6) release was observed upon CD34+ or megakaryocyte stimulation with LPS or Pam3CSK4 but not with TPO and this effect was potentiated in combination with TPO. The increased proliferation and IL-6 production induced by TPO + LPS or Pam3CSK4 were suppressed by TLR2/4 or IL-6 neutralizing antibodies, as well as by PI3K/AKT and nuclear factor-κB inhibitors. Additionally, increased proplatelet and platelet production were associated with enhanced nuclear translocation of nuclear factor-E2. Finally, the supernatants of CD34+ cells stimulated with TPO+LPS-induced CFU-M colonies. CONCLUSIONS: Our data suggest that the activation of TLR2 and TLR4 in CD34+ cells and megakaryocytes in the presence of TPO may contribute to warrant platelet provision during infection episodes by an autocrine IL-6 loop triggered by PI3K/NF-κB axes.
Subject(s)
Antigens, CD34/metabolism , Blood Platelets/drug effects , Lipopeptides/pharmacology , Lipopolysaccharides/pharmacology , Megakaryocytes/drug effects , Thrombopoiesis/drug effects , Thrombopoietin/pharmacology , Toll-Like Receptor 2/agonists , Toll-Like Receptor 4/agonists , Blood Platelets/immunology , Blood Platelets/metabolism , Cell Proliferation/drug effects , Cells, Cultured , Humans , Interleukin-6/metabolism , Megakaryocytes/immunology , Megakaryocytes/metabolism , NF-kappa B/metabolism , Phosphatidylinositol 3-Kinase/metabolism , Signal Transduction , Toll-Like Receptor 2/genetics , Toll-Like Receptor 2/metabolism , Toll-Like Receptor 4/genetics , Toll-Like Receptor 4/metabolismABSTRACT
OBJECTIVE: The purpose of this study was to describe the clinical course, complications, and outcome of patients with septic abortion admitted to the intensive care unit (ICU). DESIGN, SETTING, AND PATIENTS: In this retrospective study, the records of 63 patients with septic abortion admitted to the ICU of a university hospital in Argentina between 1985 and 1995 were reviewed. RESULTS: The mean age of the patients was 28.5 years, and 33% had had previous abortions. The mean gestational age was 10.5 weeks. The first ICU day Acute Physiology and Chronic Health Evaluation (APACHE) II mean score was 13.9. Acute renal failure developed in 73% (46 of 63) of the patients, disseminated intravascular coagulation (DIC) in 31% (15 of 49), and septic shock in 32% (20 of 63). Blood cultures were positive in 24% (15 of 62). Twelve patients died (19%). Eight of the deaths occurred during the first 48 h of the ICU admission. Compared with survivors, non-survivors had higher median number of organ failures (1.0 vs 4.0, p<0.0001), mean first ICU day SOFA scores (6.6 vs 10.0, p=0.0059), and mean APACHE II scores (12.7 vs 20.2, p=0.0003), and were more likely to have septic shock (18 vs 92%, p<0.0001), and receive dopamine (37 vs 83%, p=0.0040), mechanical ventilation (8 vs 83%, p<0.0001), and pulmonary artery catheter (8 vs 41%, p=0.0026). CONCLUSIONS: Although it is an avoidable complication, septic abortion requiring admission to the ICU is associated with high morbidity and mortality.
