Nerve growth factor synthesis in human vascular smooth muscle cells and its regulation by dexamethasone

Neurotrophins are involved in inflammatory pathways influencing several cells in healthy states and in diseases such as bronchial asthma. Recent studies have shown that nerve growth factor (NGF) is expressed in various non-neuronal cells. Furthermore, little is known about the different origins and regulation of NGF. In the present study, the expression of NGF and its regulation by dexamethasone was investigated in cultured human smooth muscle cells derived from umbilical veins (HSMC) and human iliacal arteries (HISMC).

Vascular smooth muscle cells were prepared. The presence of NGF was demonstrated by APAAP staining, western blotting, ELISA, and reverse transcription polymerase chain reaction. Vascular smooth muscle cells were incubated with dexamethasone, and cells and supernatants were collected for the measurement of NGF.

Vascular smooth muscle cells demonstrate mRNA for NGF. Proteins were detectable by western blot, ELISA, and APAAP staining. NGF Protein and mRNA were suppressed after incubation with dexamethasone (0.1 microM) for 48 h in the vascular smooth muscle cells. NGF protein was also detected in cell supernatant and was suppressed by dexamethasone as well.

These data indicate that vascular smooth muscle cells are a source of circulating NGF and thus may be involved in inflammatory responses mediated by neurotrophins. The suppression of NGF synthesis by dexamethasone might be a hint of further anti-inflammatory mechanisms of glucocorticoids.