Oxidase activity in cord blood neutrophils: a balance between increased membrane associated cytochrome b558 and deficient cytosolic components

Defective Leukocyte β2 Integrin Expression and Reactive Oxygen Species Production in Neonates

Neonates are highly susceptible to bacterial infections, which represent a major source of mortality and morbidity in this age category. It is recognized that β2 integrins play a critical role in innate immunity by mediating leukocyte vascular adhesion, transmigration and bacterial phagocytosis. Therefore, we aimed to assess if the impaired immune functions seen in newborns may derive, in part, from a transient insufficient β2 integrin expression. In the present study we measured baseline lymphocyte function-associated antigen-1 (LFA-1 or CD11a/CD18), macrophage-1 antigen (MAC-1 or CD11b/CD18) and leukocyte integrin p150-95 (CD11c/CD18) expression on cord blood, and on the third day of life in a cohort of 35 healthy neonates, compared with a control group of 12 healthy adults. For any of the three β2 integrins, the expression on polymorphonuclear cells was significantly lower on cord blood than in adults and increased from birth to day 3. We also compared superoxide radical (SR) production in these neonates with 28 non-smoking adults. SR production in response to integrin stimulation by Zymosan was significantly lower at birth than in adults, and it decreased further in the third day of life. These findings suggest that innate immune impairment in newborns may be, in part, accounted for by a lower β2 integrin expression on phagocytes in the neonatal period, but also by a functional impairment of free radical production.

Effects of local anesthetics on the respiratory burst of cord blood neutrophils in vitro

BACKGROUND

Whether local anesthetics exert anti-inflammatory effects in fetal and newborn systemic neutrophils is unclear. The aim of the present study was to assess the effects of bupivacaine and lidocaine on the respiratory burst of cord blood neutrophils in vitro compared with adult cells.

METHODS

Whole cord blood (n = 12) and control adult blood samples (n = 7) were incubated with bupivacaine (0.0005, 0.005, 0.05, 1 mmol/l) and lidocaine (0.002, 0.02, 0.2, 4 mmol/l) for 1 and 4 h. The production of reactive oxygen species (ROS) by unstimulated neutrophils and the phorbol myristate acetate-induced oxidative burst were assessed by flow cytometry. A subset of neutrophils showing high fluorescence intensity (rho+) was analyzed separately.

RESULTS

After 1 h incubation, local anesthetics decreased the respiratory burst in whole cord blood and adult neutrophils in a similar manner. At the clinically relevant concentration of 0.0005 mmol/l, bupivacaine was active, but its effect in cord blood cells could not be detected after 4 h. The cord blood rho+ cell subset was unresponsive to the inhibitory action of bupivacaine. In rho+ neutrophils, basal ROS production was stimulated by lidocaine at the lowest concentration tested.

CONCLUSION

Bupivacaine and lidocaine can decrease the respiratory burst in neutrophils of term newborns.

Neonatal sepsis and neutrophil insufficiencies

Sepsis has continuously been a leading cause of neonatal morbidity and mortality despite current advances in chemotherapy and patient intensive care facilities. Neonates are at high risk for developing bacterial infections due to quantitative and qualitative insufficiencies of innate immunity, particularly granulocyte lineage development and response to infection. Although antibiotics remain the mainstay of treatment, adjuvant therapies enhancing immune function have shown promise in treating sepsis in neonates. This article reviews current strategies for the clinical management of neonatal sepsis and analyzes mechanisms underlying insufficiencies of neutrophil defense in neonates with emphasis on new directions for adjuvant therapy development.

Generation of reactive oxygen species by umbilical blood cells and immune status of newborns at risk of infectious inflammatory diseases

We carried out a comparative clinical and immunological examination of newborns whose mothers were at risk of infectious inflammatory diseases. Umbilical blood cell phenotype was evaluated by flow cytofluorometry. ROS level was evaluated by chemiluminescence intensity. Spontaneous production of ROS and phagocytic activity of cells in the whole umbilical blood was reduced in newborns born after complicated pregnancy. Low immunoregulatory index indicating changed CD4+/CD8+ ratio and low percentage of natural killer cells were observed in children with manifestations of bacterial infection. ROS production by isolated granulocytes and the effects of PI3K and p38 MAPK (kinases involved in the regulation of activity of NADPH oxidase responsible for the production of ROS) in the risk group infants differed from the corresponding parameters in the control group. The results indicate shifts in the phagocytosis system, immune status, and the receptor-conjugated regulatory systems of ROS generation by granulocytes in newborns at risk of infectious inflammatory diseases.