TGF-ß1 is an important cytokine in airway remodeling in asthma. However, results of studies focusing on the effect of TGFß1 on proliferation of ASMCs are controversial.
METHODS:
An allergic model that mimics airway remodeling in chronic asthma was established and primary ASMCs were cultured. Cell proliferation was detected by viable cell counting and Cell Counting Kit (CCK)-8 analysis. Expression and phosphorylation of Smad3, type 1 TGFß receptor (TGFßRI), type 2 TGFß receptor (TGFßRII), extracellular signal-regulated kinase (ERK)-1/2, p38 mitogen-activated protein kinase (MAPK), C-Jun N-terminal kinase (JNK) and AKT were detected by western blot. siRNAs were used to knock down Smad3 and TGFßRII.
RESULTS:
Smad3 and TGFßRII were up-regulated in primary ASMCs isolated from ovalbumin (OVA)-sensitized mice as compared with ASMCs isolated from unsensitized controlmice, which persisted for at least four passages. TGFß1 stimulated proliferation of ASMCs isolated from OVA-sensitized mice, which was inhibited by specific siRNA targeting Smad3 or TGFßRII. However ASMCs from controlmice showed no proliferative response to TGFß1. TGFß1-induced proliferation of ASMCs from OVA-sensitized mice was markedly attenuated by PD-98059, a specific ERK1/2 inhibitor. TGFß1 induced ERK1/2 phosphorylation within 15 minute, which was partially blocked by specific inhibitor of Smad3 (SIS3).
CONCLUSIONS:
ASMCs isolated from OVA-sensitized mice showed hyper-proliferation upon TGFß1 stimulation. This might have been associated with up-regulated Smad3 and TGFßRII and mediated by ERK1/2 downstream to Smad3.