CD105 prevents apoptosis in hypoxic endothelial cells

CD105, a marker of endothelial cells, is abundantly expressed in tissues undergoing angiogenesis and is a receptor for transforming growth factorß. The pivotal role of CD105 in the vascular system was demonstrated by the severe vascular defects that occur in CD105-knockout mice, but the exact mechanisms for CD105 regulation of vascular development have not been fully elucidated. In light of the function of CD105 and the importance of hypoxia in neovascularisation, we speculated that CD105 is involved in hypoxia-initiated angiogenesis. Using tissue-cultured human microvascular endothelial cells, we have investigated the effects of hypoxic stress on CD105 gene expression. Hypoxia induced a significant increase in membrane-bound and secreted CD105 protein levels. CD105 mRNA and promoter activity were also markedly elevated, the latter returning to the basal level after 16 hours of hypoxic stress. Hypoxia induced cell cycle arrest at the G0/G1 phases and massive cell apoptosis after 24 hours through a reduction in the Bcl-2 to Bax ratio, downregulation of Bcl-XL and Mcl-1, and upregulation of caspase-3 and caspase-8. The consequence of CD105 upregulation was revealed using an antisense approach and a TUNEL assay. Suppression of CD105 increased cell apoptosis under hypoxic stress in the absence of TGFß1. Furthermore, hypoxia and TGFß1 synergistically induced apoptosis in the CD105-deficient cells but not in the control cells. We conclude that hypoxia is a potent stimulus for CD105 gene expression in vascular endothelial cells, which in turn attenuates cell apoptosis and thus contributes to angiogenesis

Vascular endothelial growth factor and its receptor, KDR, in human brain tissue after ischemic stroke

Ischemic stroke results from a reduction in cerebral blood flow to a focal region of the brain after the occlusion of an artery, causing damage to nervous tissue. There is a region of cerebral ischemic tissue (penumbra) surrounding an acute cerebral infarct that is dysfunctional but potentially viable. Restoration of perfusion in the penumbra may ameliorate the tissue damage. The identity and the role of growth factors that control the extent of tissue damage and its repair are poorly understood. Angiogenesis has been demonstrated to occur in brain tissues of patients surviving an acute ischemic stroke. In this paper we have investigated the status of a potent angiogenesis factor, vascular endothelial growth factor (VEGF), in patients after acute ischemic brain stroke. Western blotting and immunohistochemistry were used to determine protein expression, and in situ hybridization was used to quantify and localize mRNA synthesis. The expression of VEGF protein was increased in the penumbra compared with infarcted brain and contralateral hemisphere. Neurones, endothelial cells, and astrocytes in the penumbra in all patients studied had significant up-regulation of both VEGF165 and VEGF189 mRNA (p < 0.01, Wilcoxon Matched-Pairs Signed-Ranks Test) compared with infarcted tissue and the normal looking contralateral hemisphere that was used as a control. Immunohistochemistry demonstrated that kinase insert domain receptor was present in blood vessels within the infarct/penumbra and absent from the normal contralateral hemisphere. VEGF, which is important in angiogenesis, may also influence long term neuronal survival, and possibly its modulation may prove to be of therapeutic value for patients with ischemic stroke

A putative role for platelet-derived growth factor in angiogenesis and neuroprotection after ischemic stroke in humans

BACKGROUND AND PURPOSE: Growth factors control two important processes in infarcted tissue, ie, angiogenesis and gliosis. We recently reported that transforming growth factor-beta1 (TGF-beta1) might be involved in angiogenesis after ischemic stroke in humans; here we present data of an extensive study on platelet-derived growth factor (PDGF) and its receptors. METHODS: We studied brain samples from patients who suffered from ischemic stroke for the expression of mRNA encoding PDGF-A, PDGF-B, and PDGF receptors (PDGF-R). Proteins were examined by Western blotting and immunohistochemistry using the antibodies to PDGF-AB, PDGF-BB, PDGF-R alpha, and PDGF-R beta. RESULTS: At the mRNA level, PDGF-A and PDGF-B were expressed mainly in neurons in penumbra. PDGF-R mRNA was strongly expressed in some astrocytes but mainly in type III/IV neurons in infarct and penumbra. The least expression was seen in the contralateral hemisphere (P<.001). In contrast, both PDGF-AB and PDGF-BB immunoreactive products were present in most cell types: PDGF-R alpha and PDGF-R beta mainly on neurons, and PDGF-R beta on some endothelial cells, with less staining of all the isoforms in the contralateral hemisphere. On Western blots, PDGF-AB and -BB were expressed more within white matter than gray matter of infarct/penumbra, whereas both isoforms of receptor were expressed mainly in gray matter compared with contralateral hemisphere. There was no or very weak expression of the receptor in white matter. CONCLUSIONS: PDGF proteins are highly expressed in white matter, suggesting that PDGF may exert its function in white matter participating either in regeneration of damaged axons or in glial scar formation. PDGF-BB and its receptor expressed on microvessel endothelial cells might be involved in angiogenesis after stroke. Thus, PDGF is likely to be angiogenic and neuroprotective in stroke

Increased intrathecal levels of the angiogenic factors VEGF and TGF-beta in Alzheimer's disease and vascular dementia

The aim of the present study was to investigate, in patients with Alzheimer's disease (AD), and vascular dementia (VAD), patterns of local release of vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-beta), two cytokines having a pivotal role in hypoxia-induced angiogenesis. The intrathecal levels of these molecules were related to the clinical severity of these diseases and to the intrathecal levels of beta-amyloid protein.Significantly increased cerebrospinal fluid (CSF) levels of both VEGF and TGF-beta were observed in 20 patients with AD and in 26 patients with VAD compared to healthy controls. Interestingly, there was significant correlation between the CSF levels of TGF-beta and VEGF in all the individuals studied.Our study demonstrates, both in patients with AD and in patients with VAD, an intrathecal production of VEGF, a cytokine which plays a pivotal role in angiogenesis. These results suggest that vascular factors might not only play a role in the pathogenesis of VAD but also in the pathogenesis of AD. In addition, we show in AD and VAD an intrathecal production of TGF-beta, a cytokine exerting on one hand anti-inflammatory and angiogenic properties, but on the other promoting amyloidogenesis

Hepatic Stellate Cells Express the Low Affinity Nerve Growth Factor Receptor p75 and Undergo Apoptosis in Response to Nerve Growth Factor Stimulation

We have examined the expression of p75, a member of the TNF receptor superfamily in hepatic stellate cells (HSC) and pancreatic stellate cells (PSC). Activated HSC and PSC were demonstrated by Western blot analysis to express p75. p75 was immunolocalized to cells with a myofibroblast-like morphology in the fibrotic bands of six fibrotic and cirrhotic liver biopsies and three biopsies of fibrotic human pancreas. Immunostaining of parallel sections indicated that these cells were α-smooth muscle actin-positive, identifying them as activated HSC and PSC, respectively. HSC apoptosis in tissue culture in the presence of serum was quantified after addition of 0.1 to 100 ng/ml of nerve growth factor (NGF) a ligand for p75, by in situ counting of apoptotic bodies after addition of acridine orange. HSC demonstrated a significant increase in apoptosis in response to 100 ng/ml NGF (0.05 > P by Wilcoxon’s rank; n = 7) after 24 hours. NGF 100 ng/ml had no effect on HSC proliferation, but reduced total HSC DNA by 19% relative to control after 24 hours (n = 3). These data demonstrate that activated HSC express p75 and respond to NGF stimulation by undergoing apoptosis. We therefore report p75 as a novel marker of activated HSC and suggest that signaling via ligand binding to p75 may provide a mechanism for selective apoptosis of HSC