Alkaline phosphatase expression in cultured endothelial cells of aorta and brain microvessels: induction by interleukin-6-type cytokines and suppression by transforming growth factor betas.

Alkaline phosphatase (ALP) activity is markedly high in endothelial cells of the blood-brain barrier (BBB) type but absent from or low in those of the non-BBB type. Interleukin 6 (IL-6) has been identified as a glial cell line-derived factor that induces high ALP activity in cultured aortic endothelial cells. In the present study, we examined the effect of IL-6-type cytokines and transforming growth factor betas (TGF-betas) on ALP expression in cultures of calf pulmonary aortic endothelial (CPAE) cells and porcine brain microvascular endothelial (PBME) cells. Leukemia inhibitory factor, ciliary neurotrophic factor, and oncostatin M, which are known as IL-6-type cytokines, induced high ALP expression in the CPAE cells but not in the PBME cells. ALP levels in these cells were markedly suppressed by culture with TGF-betas. However, in cultured PBME cells, IL-6 and a derivative of cyclic adenosine monophosphate significantly increased ALP activity. Our findings raise the posibility that local concentrations of IL-6, IL-6-type cytokines, and TGF-betas affect the ALP levels in the endothelial cells of aorta and brain microvessels under normal development and also under inflammatory conditions.