α5 Nicotinic acetylcholine receptor mediates nicotine-induced HIF-1α and VEGF expression in non-small cell lung cancer.

By binding to nicotinic acetylcholine receptors (nAChRs), nicotine induces the proliferation and apoptosis of non-small cell lung cancer (NSCLC). Previous studies have indicated that α5-nAChR is highly associated with lung cancer risk and nicotine dependence. However, the mechanisms through which α5-nAChRs may influence lung carcinogenesis are far from clear. In the present study, we investigated the roles of α5-nAChR in the nicotine-induced expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). Immunohistochemistry was used to detect the expression of α5-nAChR and HIF-1α in 60 specimens of lung cancer and para-carcinoma tissue. The correlations between the expression levels of α5-nAChR and HIF-1α and other clinicopathological data were analyzed. In a cell line that highly expressed α5-nAChR, the loss of α5-nAChR function by siRNA was used to study whether α5-nAChR is involved in the nicotine-induced expression of HIF-1α and VEGF through the activation of the ERK1/2 and PI3K/Akt signaling pathways. Cell growth was detected using the cell counting kit-8 (CCK-8). α5-nAChR (78.3%) and HIF-1α (88.3%) were both overexpressed in NSCLC, and their expression levels were found to be correlated with each other (P<0.05). In the A549 cell line, α5-nAChR and HIF-1α were found to be expressed under normal conditions, and their expression levels were significantly increased in response to nicotine treatment. The silencing of α5-nAChR significantly inhibited the nicotine-induced cell proliferation compared with the control group and attenuated the nicotine-induced upregulation of HIF-1α and VEGF, and these effects required the cooperation of the ERK1/2 and PI3K/Akt signaling pathways. These results show that the α5-nAChR/HIF-1α/VEGF axis is involved in nicotine-induced tumor cell proliferation, which suggests that α5-nAChR may serve as a potential anticancer target in nicotine-associated lung cancer.

Dexamethasone induces osteogenesis via regulation of hedgehog signalling molecules in rat mesenchymal stem cells.

PURPOSE: Hedgehog signalling plays an important role during the development of tissues and organs, including bone and limb. Dexamethasone (DEX), a synthetic and widely used glucocorticoid, affects osteogenesis of bone marrow mesenchymal stem cells (MSCs), while the signalling pathway by which DEX affects osteoblast differentiation remains obscure. This study aimed to investigate expressions of hedgehog signalling molecules Shh, Ihh and Gli1 during DEX-induced osteogenesis of rat MSCs in vitro. METHODS: DEX promoted osteoblast differentiation of MSCs at 10(-8) mol/L from seven days to 21 days, demonstrated by enhancing alkaline phosphatase (ALP) activity and osteoblast-associated marker type I collagen expression during osteoblastic differentiation. Gene and protein expressions of hedgehog signalling molecules, Shh, Ihh and Gli1 were tested by RT-PCR and western blot analysis during osteoblast differentiation. RESULTS: Shh expression was increased compared to the control while Ihh and Gli1 expressions were decreased on both mRNA and protein level during DEX-induced osteoblast differentiation of MSCs from seven days to 21 days. Altogether, these data demonstrate that DEX can enhance Shh expression via a Gli1-independent mechanism during osteoblast differentiation of MSCs. CONCLUSIONS: These results indicate that different patterns of hedgehog signalling are involved in DEX-induced osteogenesis and these findings provide insights into the mechanistic link between glucocorticoid-induced osteogenesis and hedgehog signalling pathway.