Role of Rel A and IkappaB of nuclear factor kappaB in the release of interleukin-8 by cyclic mechanical strain in human alveolar type II epithelial cells A549.
OBJECTIVE
Overdistention of the lung tissue during mechanical ventilation may initiate ventilator-induced lung injury (VILI). Release of cytokines, including IL-8, may be responsible for VILI, although the mechanisms remain unclear. This study aimed to determine whether stretch-induced IL-8 production is dependent on degradation of IkappaB (IkappaB) and the resulting Rel A translocation into the nucleus.


METHODS
A549 cells were exposed to cyclic stretch of varying amplitude, frequency and duration before the mRNA and protein level of IL-8 were measured. To observe the role of Rel A and IkappaB of nuclear factor kappaB, A549 cells were exposed to cyclic stretch for 5 min to 1 h. Real-time PCR and ELISA respectively were performed to detect mRNA and IL-8 protein. Rel A and IkappaBalpha were assessed by Western blot. Further confirmation was sought using a nuclear factor kappaB inhibitor (PDTC) before mechanical stretch.


RESULTS
A549 cells exposed to cyclic stretch produced IL-8 in a time- and strain-dependent manner, but there was no observed effect related to stretch frequency. Activation of Rel A and IkappaBalpha was detected 10 min after the initiation of stretch, peaked at 15 min and returned to baseline within 1 h. IL-8 production was partially inhibited by the presence of PDTC.


CONCLUSIONS
Cyclic mechanical stretch can activate Rel A translocation and IkappaBalpha degradation, thus inducing the secretion of IL-8 in alveolar epithelial type II cells. Pharmacological inhibition of Rel A and IkappaBalpha inhibits IL-8 mRNA and protein levels, suggesting novel approaches to prevent VILI.
Ning
Qiaoming
Q
Department of Anesthesiology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
Wang
Xiangrui
X
D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000502:physiology; D006801:Humans; D020672:I-kappa B Proteins / Q000502:physiology*; D016209:Interleukin-8 / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology*; D011392:Proline / Q000031:analogs & derivatives / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical; D013859:Thiocarbamates / Q000494:pharmacology
D000975:Antioxidants; D020672:I-kappa B Proteins; D016209:Interleukin-8; D016328:NF-kappa B; D013859:Thiocarbamates; C066229:prolinedithiocarbamate; D011392:Proline