To analyze the differentially expressed proteins which interacted with NF-kappaB in the uterine lower segment smooth muscle tissues under different status of labor onset, and to provide a new foundation on the mechanisms for labor onset.
 Methods: NF-κB P65 protein expression in smooth muscle tissues from the term non-labor group, natural term labor group and drug-induced term labor group was analyzed by Western blot. Co-immunoprecipitation and SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) were performed to detect the proteins interacting with NF-κB p65 in the NF-κB p65 complexes. The components of the complex were identified by LC-ESI-MS/MS (liquid chromatography-tandem electrospray mass spectrometry) and database analysis. The identified differentially expressed proteins were confirmed by Western blot.
 Results: Positive expression of NF-κB was detected in all of the three groups. 10 differentially expressed proteins were identified by LC-ESI-MS/MS in human lower segment myometrium tissues in the term non-labor group and natural term labor group, mean while, 5 differentially expressed proteins were identified in the term non-labor group and the drug-induced labor group. 3 differential expression proteins were detected in all of the 3 groups, including Heat shock 70, Annexin A6 and Desmin, which were verified by Western blot. These proteins were mainly involved in chaperone, signal transduction, cell structure, and energy metabolism process, respectively.
 Conclusion: NF-κB expressed in uterine smooth muscle cells is involved in the process of initiation and regulation of labor onset through a number of proteins relevant to signal transduction, cell structure and energy metabolism.
Blotting, Western ; Electrophoresis, Polyacrylamide Gel ; Energy Metabolism ; genetics ; Female ; Humans ; Immunoprecipitation ; Labor, Obstetric ; genetics ; Molecular Chaperones ; genetics ; Myocytes, Smooth Muscle ; Myometrium ; physiology ; NF-kappa B ; genetics ; physiology ; Pregnancy ; Protein Interaction Mapping ; Proteomics ; Signal Transduction ; genetics ; Tandem Mass Spectrometry ; Transcription Factor RelA