Downregulation of IL7R, CCR7, and TLR4 in the cord blood of children with respiratory syncytial virus disease.

The association between gene expression at birth of 11 candidate genes with important innate and adaptive immune functions and later respiratory syncytial virus (RSV) disease was investigated. Cord blood was collected from 2108 newborns. Forty-seven were subsequently RSV positive. Gene expression analysis by quantitative reverse transcription-polymerase chain reaction was compared to 17 controls. There was downregulation of interleukin 7 receptor (IL7R) (P = .0001) and chemokine receptor 7 (CCR7) (P = .002), and in the severe disease subcategory, downregulation of Toll-like receptor 4 (TLR4) (P = .003). IL7R and CCR7 facilitate communication between adaptive and innate immune systems. TLR4 activates the innate immune system on RSV exposure. Delayed innate and adaptive immune activation may predispose children to more severe RSV disease.

Antioxidant protects against increases in low molecular weight hyaluronan and inflammation in asphyxiated newborn pigs resuscitated with 100% oxygen.

BACKGROUND: Newborn resuscitation with 100% oxygen is associated with oxidative-nitrative stresses and inflammation. The mechanisms are unclear. Hyaluronan (HA) is fragmented to low molecular weight (LMW) by oxidative-nitrative stresses and can promote inflammation. We examined the effects of 100% oxygen resuscitation and treatment with the antioxidant, N-acetylcysteine (NAC), on lung 3-nitrotyrosine (3-NT), LMW HA, inflammation, TNFα and IL1ß in a newborn pig model of resuscitation. METHODS & PRINCIPAL FINDINGS: Newborn pigs (n = 40) were subjected to severe asphyxia, followed by 30 min ventilation with either 21% or 100% oxygen, and were observed for the subsequent 150 minutes in 21% oxygen. One 100% oxygen group was treated with NAC. Serum, bronchoalveolar lavage (BAL), lung sections, and lung tissue were obtained. Asphyxia resulted in profound hypoxia, hypercarbia and metabolic acidosis. In controls, HA staining was in airway subepithelial matrix and no 3-NT staining was seen. At the end of asphyxia, lavage HA decreased, whereas serum HA increased. At 150 minutes after resuscitation, exposure to 100% oxygen was associated with significantly higher BAL HA, increased 3NT staining, and increased fragmentation of lung HA. Lung neutrophil and macrophage contents, and serum TNFα and IL1ß were higher in animals with LMW than those with HMW HA in the lung. Treatment of 100% oxygen animals with NAC blocked nitrative stress, preserved HMW HA, and decreased inflammation. In vitro, peroxynitrite was able to fragment HA, and macrophages stimulated with LMW HA increased TNFα and IL1ß expression. CONCLUSIONS & SIGNIFICANCE: Compared to 21%, resuscitation with 100% oxygen resulted in increased peroxynitrite, fragmentation of HA, inflammation, as well as TNFα and IL1ß expression. Antioxidant treatment prevented the expression of peroxynitrite, the degradation of HA, and also blocked increases in inflammation and inflammatory cytokines. These findings provide insight into potential mechanisms by which exposure to hyperoxia results in systemic inflammation.

The impact of hyaluronan on monocyte Toll-like receptor expression in term infant cord blood.

AIM: To explore the possible effects of hyaluronan, an endogenous mediator of inflammation, on monocyte surface expression of Toll-like receptors 2 and 4 in human umbilical cord blood ex vivo, and in a model mimicking Gram-negative neonatal sepsis. METHODS: Term infant cord blood was obtained after elective caesarean sections, n = 15. Both unstimulated and lipopolysaccharide-stimulated (10 ng/mL) blood was incubated with 500 µg/mL high- or low-molecular-weight hyaluronan for 6 h. Expression of Toll-like receptors 2 and 4 on monocytes was measured using flow cytometry, and plasma concentrations of proinflammatory cytokines and matrix metalloproteinase 9 were analysed. RESULTS (MEAN ± SEM): We found a significant decrease in Toll-like receptor 4 expression in the presence of high-molecular-weight hyaluronan (HMW HA) in unstimulated blood (median fluorescence intensity 141 ± 7.3 vs. 163 ± 9.8, p = 0.019). There were no significant changes in Toll-like receptor 2 expression. Levels of cytokines and matrix metalloproteinase 9 increased in the presence of both forms of hyaluronan. CONCLUSIONS: Our results confirm that hyaluronan affects the neonatal immune response. The biological significance of these findings requires further clarification. More studies are needed to validate the possible down-modulation of Toll-like receptor 4 exerted by HMW HA.

Moderate temperature alterations affect Gram-negative immune signalling in ex vivo whole blood.

BACKGROUND: Alterations in body temperature may influence immune system function and consequently affect the risk of infection and inflammatory diseases. Lipopolysaccharide (LPS) from gram-negative bacteria induces production of inflammatory cytokines after ligand binding to Toll-like receptor 4 (TLR4) on immune cells (especially monocytes/ macrophages). Our aim was to explore how clinically relevant hypo- and hyperthermia affect this signalling in an ex vivo whole blood model, and investigate if the cytokine response was correlated with monocyte TLR4 expression level. METHODS: Blood from 11 healthy volunteers was incubated with LPS 10 ng/ml for 6 h at 33, 37 or 40°C. The concentrations of selected pro-inflammatory (tumour necrosis factor-α (TNF-α) and interleukin (IL)-1ß) and anti-inflammatory (IL-10) cytokines were measured in plasma, and the surface expression of TLR4 was quantified on CD14 + monocytes. RESULTS: Monocyte TLR4 expression and plasma IL-1ß were inversely related to temperature. The TNF-α production was unaffected by hypothermia but increased significantly during hyperthermia, whereas plasma IL-10 was significantly reduced during both hypo- and hyperthermic incubation. No correlation was found between TLR4 expression and cytokine concentrations. During hypothermia, the TNF-α/IL-10 and IL-1ß/IL-10 ratios increased seven and nine times, respectively. Hyperthermia increased the TNF-α/IL-10 ratio, but to a lesser extent (doubling), whereas the IL-1ß/IL-10 ratio remained unchanged. CONCLUSION: Hypothermia significantly changed the cytokine ratios in the pro-inflammatory direction. In comparison, the effect of hyperthermia was sparse, with a modest increase in the TNF-α/IL-10 ratio only. No association was found between LPS-stimulated cytokine production and TLR4 expression on CD14 + monocytes.