Methods: Primary normal human epithelial cells (NHBEC) and bronchial smooth muscle cells were incubated with SC-MN and examined for KLF4, KLF5, p38MAPK levels and phosphorylation over a time course by Western Blot (WB). Normal human bronchial smooth muscle cells were analyzed for SM22alpha levels by WB and alpha-isoactin by indirect immunofluorescent staining.
Results: Following exposure to SC-MN, protein levels of KLF4 and KLF5 increased in both NHBEC and NHBSM cells over the subsequent 2-18 h. SC-MN–treated bronchial smooth muscle cells, but not in NHBEC, showed biphasic activation of p38MAPK (5-120 min and 8 h) that is known to lead to KLF phosphorylation in vascular smooth muscle cells. In addition, SC-MN increased smoooth muscle specific alpha-isoactin and SM22alpha at 24 hrs, consistent with a phenotype change.
Conclusions: SC-MN can induce KLF4 or KLF5, transcription factors that are important in epithelial survival and regulation of smooth muscle proliferation.