Platelet-Activating Factor Induces TLR4 Expression in Intestinal Epithelial Cells: Implication for the Pathogenesis of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of morbidity and mortality in neonatal intensive care units, however its pathogenesis is not completely understood. We have previously shown that platelet activating factor (PAF), bacteria and TLR4 are all important factors in the development of NEC. Given that Toll-like receptors (TLRs) are expressed at low levels in enterocytes of the mature gastrointestinal tract, but were shown to be aberrantly over-expressed in enterocytes in experimental NEC, we examined the regulation of TLR4 expression and signaling by PAF in intestinal epithelial cells using human and mouse in vitro cell lines, and the ex vivo rat intestinal loop model. In intestinal epithelial cell (IEC) lines, PAF stimulation yielded upregulation of both TLR4 mRNA and protein expression and led to increased IL-8 secretion following stimulation with LPS (in an otherwise LPS minimally responsive cell line). PAF stimulation resulted in increased human TLR4 promoter activation in a dose dependent manner. Western blotting and immunohistochemical analysis showed PAF induced STAT3 phosphorylation and nuclear translocation in IEC, and PAF-induced TLR4 expression was inhibited by STAT3 and NFκB Inhibitors. Our findings provide evidence for a mechanism by which PAF augments inflammation in the intestinal epithelium through abnormal TLR4 upregulation, thereby contributing to the intestinal injury of NEC

Aerosol therapy in intensive and intermediate care units: prospective observation of 2808 critically ill patients.

PURPOSE: Unlike in the outpatient setting, delivery of aerosols to critically ill patients may be considered complex, particularly in ventilated patients, and benefits remain to be proven. Many factors influence aerosol delivery and recommendations exist, but little is known about knowledge translation into clinical practice. METHODS: Two-week cross-sectional study to assess the prevalence of aerosol therapy in 81 intensive and intermediate care units in 22 countries. All aerosols delivered to patients breathing spontaneously, ventilated invasively or noninvasively (NIV) were recorded, and drugs, devices, ventilator settings, circuit set-up, humidification and side effects were noted. RESULTS: A total of 9714 aerosols were administered to 678 of the 2808 admitted patients (24 %, CI95 22-26 %), whereas only 271 patients (10 %) were taking inhaled medication before admission. There were large variations among centers, from 0 to 57 %. Among intubated patients 22 % (n = 262) received aerosols, and 50 % (n = 149) of patients undergoing NIV, predominantly (75 %) inbetween NIV sessions. Bronchodilators (n = 7960) and corticosteroids (n = 1233) were the most frequently delivered drugs (88 % overall), predominantly but not exclusively (49 %) administered to patients with chronic airway disease. An anti-infectious drug was aerosolized 509 times (5 % of all aerosols) for nosocomial infections. Jet-nebulizers were the most frequently used device (56 %), followed by metered dose inhalers (23 %). Only 106 (<1 %) mild side effects were observed, despite frequent suboptimal set-ups such as an external gas supply of jet nebulizers for intubated patients. CONCLUSIONS: Aerosol therapy concerns every fourth critically ill patient and one-fifth of ventilated patients