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Interleukin release from type 2 alveolar cell analogues following stretch mimicking standard inflations or sustained inflations at resuscitation

Presented at the Neonatal Society 2018 Spring Meeting (programme).

Harris C, Rushwan S, Wang W, Thorpe S, Gooptu B, Knight M, Greenough A

Kings College London
Queen Mary’s University London

Background: Pulmonary inflammation is increased in infants who develop BPD. There is increasing interest in the use of sustained inflations of 15 seconds or greater at initial resuscitation. Currently, UK practice is to deliver five 2-3 second inflations. Stretch has been shown to cause release of inflammatory mediators from type 2 alveolar cells and interleukin release was greater following tidal compared to static stretch (1, 2). We hypothesised that fewer and longer stretches of lung cells would produce lower levels of inflammation than more and shorter inflations.

Methods: Using a Flexcell 4000, type 2 alveolar cells analogues (A549 cells), cultured in medium for three days on flexible collagen plates were stretched at 20% basement membrane stretch (BMS) from rest for three seconds for 10 cycles (mimicking UK resuscitation council recommended inflations) or at 20% BMS for 15 seconds for two cycles (mimicking sustained inflations). The cells were incubated for four hours after stretching to allow for maximum IL-8 RNA expression. Media was then removed and analysed for interleukin 8 (IL-8) and interleukin 6 (IL-6) by ELISA. Each experimental protocol was repeated three times and interleukin release was compared to unstretched controls. Results were expressed as fold increase in interleukin release over unstretched controls.

Results: The mean fold increase of IL-8 was higher following 10 three second inflations compared to sustained inflations (1.24, standard deviation (SD) 0.19, versus 0.99, SD 0.17) p=0.016. The mean fold increase of IL-6 was higher following 10 three second inflations compared to sustained inflations (1.07, SD 0.13, versus 0.90 SD 0.13) p=0.014.

Conclusion: Alveolar cells subjected to ten three second inflations compared to those subjected to two sustained inflations for 15 seconds produced a greater inflammatory response. These results further suggest that modes of initial resuscitation might influence respiratory outcomes in prematurely born infants.

Corresponding author:

1. Vlahakis et al, Am J Physiol, 1999
2. Harris et al (abstract) ADC, 2017

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