ABSTRACT
BACKGROUND: Adenosine levels are regulated by ecto-5'-nucleotidase/CD73 and adenosine deaminase (ADA). Adenosine regulates endothelial permeability and anti-inflammatory responses via adenosine receptors. Here, the adenosine receptors and purine-converting enzymes were studied during postnatal development and inflammation. METHODS: Newborn, 1-, 10-, 14-d-old and adult C57BL/6 mice were challenged intraperitoneally (i.p.) with lipopolysaccharide (LPS) for 6 h. The inflammatory response was evaluated by histochemistry. Expression levels of adenosine receptors (A1, A2A, A2B, and A3), CD73, and ADA were measured by quantitative reverse transcription polymerase chain reaction. A1 was studied by immunohistochemistry, and enzyme activities were analyzed by thin-layer chromatography. RESULTS: LPS caused respiratory distress in newborns within 24 h. LPS induced neutrophils at the basal stage and alveolar congestion. Low activity and expression of CD73 increased after birth. Expression of ADA after LPS increased 16-fold in adults and 2-fold in newborns (P < 0.05). A1 expression was high in newborns and increased after LPS (P < 0.05). A1 was localized to endothelial membranes. A2A decreased after LPS in newborns and increased in adults (P < 0.05). The expression of A3 increased in newborns and adults after LPS. CONCLUSION: Low pulmonary CD73 expression, LPS-induced suppression of A2A, LPS-induced increase of A1 expression, and severe respiratory distress were distinguishing responses in the newborns from those in the adults.
Subject(s)
5'-Nucleotidase/metabolism , Adenosine Deaminase/metabolism , Adenosine/metabolism , Lipopolysaccharides , Lung/enzymology , Pneumonia/enzymology , Receptors, Purinergic P1/metabolism , Respiratory Distress Syndrome, Newborn/enzymology , 5'-Nucleotidase/genetics , Adenosine Deaminase/genetics , Age Factors , Animals , Animals, Newborn , Disease Models, Animal , GPI-Linked Proteins/genetics , GPI-Linked Proteins/metabolism , Gene Expression Regulation, Enzymologic , Lung/growth & development , Mice, Inbred C57BL , Neutrophil Infiltration , Pneumonia/chemically induced , Pneumonia/genetics , Pneumonia/physiopathology , RNA, Messenger/metabolism , Receptors, Purinergic P1/genetics , Respiratory Distress Syndrome, Newborn/chemically induced , Respiratory Distress Syndrome, Newborn/genetics , Respiratory Distress Syndrome, Newborn/physiopathologyABSTRACT
OBJECTIVE: To study antenatal risk factors and inflammatory responses during hypoxic respiratory failure (HRF) in infants of very low gestational age (VLGA, ≤32.0 weeks). STUDY DESIGN: Of a cohort of 765 VLGA infants, 144 required mechanical ventilation. Airway specimens from these patients were prospectively studied. Infants who developed HRF (oxygenation index >25) with echocardiographic diagnosis of pulmonary hypertension were treated with inhaled nitric oxide (iNO). Three gestation comparison groups were formed on the basis of specific antenatal complications: prolonged preterm rupture of membranes (PPROM), spontaneous preterm birth, and preeclampsia. Chest radiographs were studied and airway specimens were analyzed for concentrations of tumor necrosis factor-α, interleukin (IL)-6, IL-8, IL-10, IL-12p70, IL-1ß, and nitrite + nitrate over 4 days. RESULTS: Seventeen (2.2% of all VLGA infants) developed HRF. In all 17 cases, PPROM complicated the antenatal course; these infants responded to iNO, regardless of infection or PPROM. The chest radiographs of HRF and non-HRF PPROM infants were similar. Airway proinflammatory cytokines and nitrite + nitrate levels were low in infants with HRF, but they increased during iNO treatment and remained elevated after discontinuation of iNO. Each of the 3 comparison groups had different and characteristic patterns of airway cytokines and nitrite + nitrate levels. CONCLUSIONS: Seven percent of VLGA infants with preterm rupture of membranes and 15% of those with PPROM developed HRF, characterized by pulmonary hypertension that acutely responds to iNO. These infants may have a transient deficiency in the inflammatory response, including a defect in nitric oxide generation in airspaces.
Subject(s)
Bronchodilator Agents/therapeutic use , Infant, Premature, Diseases/drug therapy , Nitric Oxide/therapeutic use , Respiratory Insufficiency/drug therapy , Administration, Inhalation , Bronchodilator Agents/administration & dosage , Female , Fetal Membranes, Premature Rupture , Humans , Hypoxia , Infant, Newborn , Infant, Premature , Infant, Premature, Diseases/physiopathology , Nitric Oxide/administration & dosage , Nitric Oxide/biosynthesis , Pregnancy , Respiratory Insufficiency/epidemiology , Respiratory Insufficiency/metabolism , Risk FactorsABSTRACT
Major cause of prematurity is spontaneous preterm birth (PTB) associated with intrauterine inflammation. Our aim was to establish a model of endotoxin Lipopolysaccharide-induced PTB of live-born pups and to study early immune activation in fetal and maternal compartments. Expression of several proteins that bind microbes (Toll-like receptors TLR4, TLR2; surfactant proteins SP-A, SP-D) was analyzed. At 16 or 17 d of gestation, C57BL/6 dams received a single dose of intraperitoneal LPS, leading to PTB within 17 h. Cytokine levels increased in maternal serum, followed by a modest increase in fetal serum and in amniotic fluid. In uterus, placenta, and fetal membranes, LPS mostly increased the expressions of TLR, SPs, and cytokines. The number of TLR2-positive macrophages increased in labyrinthine placenta. In fetal lung, intestine, liver, and brain there were modest changes in cytokine expressions. In fetal lung, SP and TLR mRNAs decreased and TLR2-positive macrophages redistributed around vessels. LPS-induced fetal deaths associated with early age (16 d gestation) rather than with proinflammatory activation. Here we propose that maternal LPS response leads to PTB and acute decrease of immune proteins in epithelial lining of fetal lung. Instead, acceleration of lung maturity has been previously observed in intraamniotic inflammation.
