Published online before print October 30, 2008, doi: 10.1161/STROKEAHA.108.524504
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(Stroke. 2009;40:652.)
© 2009 American Heart Association, Inc.
Research Letters |
Lithium Upregulates Vascular Endothelial Growth Factor in Brain Endothelial Cells and Astrocytes
From the Neuroprotection Research Laboratory, Departments of Radiology and Neurology (S.G., K.A., E.H.L.), Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, Mass; the Department of Neurology (M.F.S.), Johns Hopkins School of Medicine, Baltimore, Md; and the Molecular Neurobiology Section (D.-M.C.), National Institutes of Mental Health, Bethesda, Md.
Correspondence to Eng H. Lo, PhD, MGH East 149-2401, Charlestown, MA 02129. E-mail Lo{at}helix.mgh.harvard.edu
Background and Purpose— We recently reported that delayed lithium therapy can improve stroke recovery in rats by augmenting neurovascular remodeling. We tested the hypothesis that lithium can promote the expression of growth factors in brain endothelial cells and astrocytes.
Methods— Human brain microvascular endothelial cells and primary rat cortical astrocytes were exposed to lithium chloride in serum-free medium. We examined 2 representative growth factors: brain-derived neurotrophic factor and vascular endothelial growth factor (VEGF). Cell lysates were collected for Western blot analysis. Conditioned media was analyzed with enzyme-linked immunosorbent assay. SB-216763 and LY294002 were used to assess the roles of the glycogen synthase kinase-3β (GSK-3β) and PI3-K signaling in the lithium-induced responses.
Results— No consistent responses were observed for brain-derived neurotrophic factor. However, lithium (0.2 to 20 mmol/L) increased the phosphorylation of GSK-3β and promoted VEGF secretion in a concentration-dependent manner in both endothelial and astrocyte cells. For endothelial cells, the potent GSK-3β inhibitor SB-216763 upregulated VEGF, whereas inhibition of PI3-K with LY294002 suppressed lithium-induced responses in both phospho-GSK-3β and VEGF. In contrast, neither inhibition of GSK-3β nor inhibition of PI3-K had any detectable effects on VEGF levels in astrocytes.
Conclusions— Lithium promotes VEGF expression through PI3-K/GSK-3β-dependent and -independent pathways in brain endothelium and astrocytes, respectively. This growth factor signaling mechanism may contribute to lithium’s reported ability to promote neurovascular remodeling after stroke.
Key Words: growth factor • neuroprotection • neurovascular unit • stroke recovery