STAT3 Regulates Monocyte TNF-Alpha Production in Systemic Inflammation Caused by Cardiac Surgery with Cardiopulmonary Bypass

BACKGROUND: Cardiopulmonary bypass (CPB) surgery initiates a controlled systemic inflammatory response characterized by a cytokine storm, monocytosis and transient monocyte activation. However, the responsiveness of monocytes to Toll-like receptor (TLR)-mediated activation decreases throughout the postoperative course. The purpose of this study was to identify the major signaling pathway involved in plasma-mediated inhibition of LPS-induced tumor necrosis factor (TNF)-α production by monocytes. METHODOLOGY/PRINCIPAL FINDINGS: Pediatric patients that underwent CPB-assisted surgical correction of simple congenital heart defects were enrolled (n = 38). Peripheral blood mononuclear cells (PBMC) and plasma samples were isolated at consecutive time points. Patient plasma samples were added back to monocytes obtained pre-operatively for ex vivo LPS stimulations and TNF-α and IL-6 production was measured by flow cytometry. LPS-induced p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB activation by patient plasma was assessed by Western blotting. A cell-permeable peptide inhibitor was used to block STAT3 signaling. We found that plasma samples obtained 4 h after surgery, regardless of pre-operative dexamethasone treatment, potently inhibited LPS-induced TNF-α but not IL-6 synthesis by monocytes. This was not associated with attenuation of p38 MAPK activation or IκB-α degradation. However, abrogation of the IL-10/STAT3 pathway restored LPS-induced TNF-α production in the presence of suppressive patient plasma. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that STAT3 signaling plays a crucial role in the downregulation of TNF-α synthesis by human monocytes in the course of systemic inflammation in vivo. Thus, STAT3 might be a potential molecular target for pharmacological intervention in clinical syndromes characterized by systemic inflammation

Zur sprachlichen und stilistischen Würdigung der altkirchenslavischen Vita Constantini

Overdruk uit: Südost-Forschungen, p. 74-10

Neonatal thymectomy reveals differentiation and plasticity within human naive T cells

The generation of naive T cells is dependent on thymic output, but in adults, the naive T cell pool is primarily maintained by peripheral proliferation. Naive T cells have long been regarded as relatively quiescent cells; however, it was recently shown that IL-8 production is a signatory effector function of naive T cells, at least in newborns. How this functional signature relates to naive T cell dynamics and aging is unknown. Using a cohort of children and adolescents who underwent neonatal thymectomy, we demonstrate that the naive CD4+ T cell compartment in healthy humans is functionally heterogeneous and that this functional diversity is lost after neonatal thymectomy. Thymic tissue regeneration later in life resulted in functional restoration of the naive T cell compartment, implicating the thymus as having functional regenerative capacity. Together, these data shed further light on functional differentiation within the naive T cell compartment and the importance of the thymus in human naive T cell homeostasis and premature aging. In addition, these results affect and alter our current understanDing on the identification of truly naive T cells and recent thymic emigrants

Main pulmonary artery area limits exercise capacity in patients long-term after arterial switch operation

OBJECTIVES: Despite excellent survival in patients after the arterial switch operation, reintervention is frequently required and exercise capacity is decreased in a substantial number of patients. This study relates right-sided imaging features in patients long-term after the arterial switch operation to exercise capacity and ventilatory efficiency to investigate which lesions are functionally important. METHODS: Patients operated in the UMC Utrecht, the Netherlands (1976-2001) and healthy controls underwent cardiac magnetic resonance imaging and cardiopulmonary exercise testing within 1 week. We measured main, left, and right pulmonary artery cross-sectional areas, pulmonary blood flow distribution, peak oxygen uptake, and minute ventilation relative to carbon dioxide elimination. RESULTS: A total of 71 patients (median age, 20 [12-35] years, 73% were male) and 21 healthy controls (median age, 26 [21-35] years, 48% were male) were included. Main, left, and right pulmonary artery areas were decreased compared with controls (190 vs 269 mm(2)/m(2), 59 vs 157 mm(2)/m(2), 98 vs 139 mm(2)/m(2), respectively, all P 25 years) showed that the main pulmonary artery area was smaller in older age groups. In multivariable analysis, the main pulmonary artery area was independently associated with peak oxygen uptake (P = .032). CONCLUSIONS: In adult patients after the arterial switch operation, narrowing of the main pulmonary artery is a common finding and is the main determinant of limitation in functional capacity, rather than pulmonary branch stenosis

Post-perfusion plasma suppresses LPS-induced TNF-α production by monocytes.

<p><b>A</b>. Percentage of TNF-α producing cells in the monocyte population after <i>ex vivo</i> LPS stimulation (100 ng/mL) of patient PBMC isolated at various time points (n = 4). <b>B</b>. Reduced TNF-α synthesis by monocytes after LPS (10 ng/mL) stimulation in whole blood assays with patient samples obtained at the indicated time points (n = 5). <b>C</b>. Experimental setup for experiments shown in D,E,G-I. In short, patient PBMC obtained before surgery (Pre-op) were mixed with control (pooled AB plasma from healthy donors) or autologous patient plasma samples obtained at indicated time points, followed by LPS (100 ng/mL) stimulation for 4 h. Monocyte populations (CD14/SSC gate) were then analyzed for intracellular TNF-α and IL-6 synthesis. <b>D</b>. Significantly reduced production of TNF-α by monocytes after LPS stimulation in the presence of plasma samples from different sources (n = 13). Shown are percentages of TNF-α producing monocytes relative to control (100%). *<i>P</i><0.05, **<i>P</i><0.001 vs. control (ANOVA). <b>E</b>. Percentages of IL-6 producing monocytes as in D. **<i>P</i><0.001 vs. control (ANOVA). <b>F</b>. Dexamethasone levels in patient plasma samples as measured by radio-immunoassay (n = 9). Median ± interquartile range. *<i>P</i><0.05 vs. pre-op (ANOVA). <b>G</b>. Production of TNF-α and IL-6 by monocytes after LPS stimulation in the presence of dexamethasone-free plasma samples (n = 4). *<i>P</i><0.05 vs. control (ANOVA). <b>H</b>. Mean fluorescence intensities (MFI) of TNF-α and IL-6 in monocytes after LPS stimulation in different plasma milieus (n = 7). *<i>P</i><0.05, **<i>P</i><0.001 vs. control (ANOVA). <b>I</b>. Representative flow cytometry results (contour plots) of the LPS-induced TNF-α production by monocytes in the presence of control or patient plasma (Pre-op, End-CPB, 4 h or 24 h post-perfusion plasma from a No-dexamethasone patient). Isotype control: mouse IgG1. Data represented as mean ± SEM, unless otherwise indicated.</p