Cigarette smoke is a complex mixture of various chemical compounds, including free radicals and highly toxic compounds. This study aimed to determine the effects of CSE on VEGF expression and to investigate the underlying molecular mechanisms of CSE in nasal fibroblasts.
Cytotoxicity was evaluated by 3-(4,5- dimethylthiazol-2yl)-2,5-diphenyl-tetrazolium bromide assay. The expression level was measured using RT-PCR and enzyme-linked immunosorbent assay. RT-PCR determined the mRNA expression level of TLR4R. siRNA for TLR4 was transfected to suppress TLR4 expression. Activation of ROS was analyzed by using dichlorodihydro-fluorescein diacetate assay. MAPK and NF-kappaB activations were determined using western blot and luciferase assay.
CSE had no significant cytotoxic effect in nasal fibroblast up to 5%. CSE significantly increased both VEGF mRNA and protein expression dose-dependently. The down-regulation of TLR4 transcription by siRNA treatment suppressed CSE-induced expressions of both TLR4 and VEGF. Pretreatment with ROS scavengers, specific inhibitors of each MAPK, and NF-kappaB inhibitor significantly decreased CSE-induced VEGF expression.
The study concluded that CSE has a stimulatory effect on VEGF expression through the TLR4, ROS, MAPK, and NF-kappaB signaling pathway in nasal fibroblasts.