Cellular strain amplifies lps-induced stress signaling in immature enterocytes: potential implications for preterm infant nasal CPAP

BACKGROUND: Recent clinical observations of increased necrotizing enterocolitis (NEC) incidence in some Nasal Continuous Positive Airway Pressure (NCPAP) patients raise concerns whether the related abdominal distension is benign or contributes to NEC. We tested the hypothesis that mechanical strain causes an exaggerated enterocyte inflammatory response and decreased enterocyte growth and proliferation, in the absence and presence of lipopolysaccharide (LPS). METHODS: First we used a confluent enterocyte (IEC-6) monolayer to investigate effects of strain on inflammatory cytokine production and Toll-like Receptor 4 (TLR4) gene expression. Then we used a low seeding density to measure cell growth and proliferation. 10% mechanical strain was applied. RESULTS: Significant increases in IL-8 and in IL-6 were observed after 8 and 24 h of cellular strain respectively, and maintained throughout the study. TLR-4 expression was increased at 48 hours. Mechanical strain led to slower proliferation and division whereas LPS alone had minimal effects. The responses of LPS and strain were supra-additive, suggesting synergistic cellular effects. CONCLUSION: We speculate intestinal distension associated with the use of NCPAP, especially in the presence of abnormal gut colonization, may result in increased inflammatory cytokine production and be a contributing factor to neonatal intestinal morbidities.