The Role of Lipopolysaccharide Structure in Monocyte Activation and Cytokine Secretion.

BACKGROUND: The lipopolysaccharide (LPS) molecule is composed of a hydrophobic lipid region (Lipid A), an oligosaccharide core, and an O-Antigen chain. Lipid A has been described as the molecular region responsible for inducing activation of immune cells. We hypothesize that the O-Antigen plays a critical role in the activation and responsiveness of mononuclear cell immune function. METHODS: Peripheral blood mononuclear cells (PBMCs) from healthy volunteers were stimulated with LPS, LPS with attenuated O-Antigen (RF5), or Lipid A (DPL), which lacks an O-Antigen. Selected cells were pretreated with a blocking antibody to CD14. Western blots were performed to determine activation of mitogen-activated protein kinases (MAPK) p38, ERK, and JNK at selected time-points. RNA was extracted for RT-PCR quantification of TNF-α and IL-10 gene transcription. Supernatants were harvested and analyzed by ELISA for tumor necrosis factor alpha (TNF-α) and interleukin 10 (IL-10). RESULTS: LPS elicited maximal response, including phosphorylation of p38, ERK, and JNK, synthesis of TNF-α and IL-10 mRNA, and secretion of TNF-α and IL-10. Stimulation with RF5 activated the same pathways to a lesser degree. DPL led to increased phosphorylation of p38 and ERK and increased secretion of IL-10. CD14 blockade was associated with a significant decrease in cytokine secretion by LPS, and abolished cytokine secretion in cells stimulated with RF5 or DPL. CONCLUSIONS: Structural variants of LPS activate monocytes differentially. The complete O-Antigen is important for maximal activation of MAPK, cytokine synthesis, and cytokine secretion. LPS with attenuated O-Antigen and Lipid A activate only certain components of these pathways. LPS with a complete O-Antigen stimulates cytokine secretion that is partially independent of CD14, but shortening or removal of the O-Antigen inhibits this secretion.

Surgical versus nonsurgical interventions to relieve upper airway obstruction in children with Pierre Robin sequence.

BACKGROUND: Newborns with Pierre Robin sequence (PRS) often experience chronic intermittent hypoxemia/hypoventilation associated with airway obstruction. The heterogeneity of the severity of upper airway obstruction makes management a challenge; the optimal intervention in individual cases is not clear. OBJECTIVE: To investigate the prevalence of surgical/nonsurgical interventions for PRS at two children's hospitals. Patient characteristics and outcomes were examined. METHODS: The present retrospective chart review identified 139 patients with PRS born between 2000 and 2010. Demographic information, mode of airway management, associated anomalies and syndromes, polysomnography results, length of intensive care unit and hospital stay, complications and deaths were extracted. RESULTS: Interventions included prone positioning (alone [61%]), tongue-lip adhesion (45%), nasopharyngeal intubation (28%), continuous positive airway pressure (20%), tracheostomy (19%) and mandibular distraction osteogenesis (5%). Tracheostomies were more prevalent in syndromic patients (P=0.03). Patients who underwent tracheostomy had a lower birth weight (P=0.03) compared with newborns with other interventions. Patients who underwent surgical interventions had longer intensive care unit stays (P<0.001). No intervention was associated with a statistically significant likelihood of requiring a subsequent intervention. Thirty percent of patients underwent polysomnography, with a higher proportion of these using continuous positive airway pressure (n=15) (P<0.01). CONCLUSIONS: In the present descriptive study, patients with syndromic PRS or low birth weight underwent early intervention, which included a tracheostomy. Objective measures of airway obstruction were underutilized. Decision making regarding evaluation and management of upper airway obstruction in this population remains clinician and resource dependent. Reporting data obtained from a large cohort of PRS patients is important to compare experiences and motivate future studies investigating this complex condition.