VEGF Stimulates the ERK 1/2 signaling pathway and apoptosis in cerebral endothelial cells after ischemic conditions

Oxidative stress and its role in the pathogenesis of ischaemic stroke

Stroke is one of the leading causes of mortality and morbidity, with astronomical financial repercussions on health systems worldwide. Ischaemic stroke accounts for approximately 80-85% of all cases and is characterised by the disruption of cerebral blood flow and lack of oxygen to the affected area. Oxidative stress culminates due to an imbalance between pro-oxidants and antioxidants and consequent excessive production of reactive oxygen species. Reactive oxygen species are biphasic, playing a role in normal physiological processes and are also implicated in a number of disease processes, whereby they mediate damage to cell structures, including lipids, membranes, proteins, and DNA. The cerebral vasculature is a major target of oxidative stress playing a critical role in the pathogenesis of ischaemic brain injury following a cerebrovascular attack. Superoxide, the primary reactive oxygen species, and its derivatives have been shown to cause vasodilatation via the opening of potassium channels and altered vascular reactivity, breakdown of the blood-brain barrier and focal destructive lesions in animal models of ischaemic stroke. However, reactive oxygen species are involved in normal physiological processes including cell signalling, induction of mitogenesis, and immune defence. Primarily, this review will focus on the cellular and vascular aspects of reactive oxygen and nitrogen species generation and their role in the pathogenesis of ischaemia-reperfusion phenomena. Secondly, the proposed mechanisms of oxidative stress-related neuronal death will be reflected upon and in summation specific targeted neuroprotective therapies targetting oxidative stress and their role in the pathogenesis of stroke will be discussed.

CREB activation mediates VEGF-A's protection of neurons and cerebral vascular endothelial cells

Hypoxic ischemia (HI) in neonates causes significant neurodevelopmental sequelae. Pharmacological agents designed to target specific transcription factors expressed in neurons and vasculature may provide powerful therapy against HI. Vascular endothelial growth factor-A (VEGF-A) and cAMP response element-binding protein (CREB) both underlie learning and memory, and survival of the nervous system. We examined whether CREB activation is a shared pathway underlying VEGF-A's protection in neurons and cerebral vascular endothelial cells. VEGF-A was used in a HI model of rat pups and in oxygen-glucose-deprivation (OGD) models of immortalized H19-7 neurons and b.End3 cerebral vascular endothelial cells. We found that VEGF-A activated VEGF receptor-2 (VEGFR-2), phosphorylated CREB in neurons and endothelial cells, and protected against HI, and inhibiting VEGFR-2 before VEGF-A reduced the protective effect of VEGF-A in rat pups. VEGF-A also up-regulated VEGFR-2 and phosphorylated CREB, and protected H19-7 neurons and b.End3 endothelial cells against OGD. Inhibiting VEGFR-2 and extracellular signal-regulated kinase (ERK), respectively, reduced VEGF-A-induced CREB phosphorylation and protection of H19-7 and b.End3 cells against OGD. Transfecting H19-7 and b.End3 cells with a serine-133 phosphorylation mutant CREB also inhibited VEGF-A's protection of both types of cells. We conclude that CREB phosphorylation through VEGFR-2/ERK signaling is the shared pathway that underlies VEGF-A's protection of neurons and vascular endothelial cells.

Icaritin induces growth inhibition and apoptosis of human prostatic smooth muscle cells in an estrogen receptor-independent manner

Icaritin has selective estrogen receptor (ER) modulating activity. ERs are expressed in the prostate stroma, and estrogens have an important role in the pathology of benign prostatic hyperplasia (BPH). However, the impact of icaritin on BPH was not studied. Human prostatic smooth muscle cells (PSMCs) were treated with 0-100 microM icaritin, also using 10 microM ICI182780 as a specific ER antagonist. The effects on cell growth and apoptosis were determined by cell counting and sandwich-enzyme-immunoassay. Western blotting was employed to illustrate the possible mechanisms. Cell growth was strongly inhibited by icaritin, and this was accompanied by an augmented apoptosis. Few changes in icaritin-induced growth inhibition and apoptosis were observed after pretreatment in the presence of ICI182780. Consistent with growth inhibition and apoptosis induction, icaritin decreased cyclin D1 and CDK4 expression and increased Bax/Bcl-2 ratio in human PSMCs. Furthermore, icaritin induced sustained phosphorylation of extracellular signal-regulated kinase (ERK) in human PSMCs. PD98059, a specific ERK inhibitor, blocked the activation of ERK by icaritin and abolished the icaritin-induced growth inhibition and apoptosis. The results indicate that icaritin reduces growth and induces apoptosis in human PSMCs via ERK signaling pathway without involvement of ERs.

Expression of HIF-1 alpha, VEGF and EPO in peripheral blood from patients with two cardiac abnormalities associated with hypoxia

OBJECTIVES

HIF-1 alpha (hypoxia-inducible factor-1 alpha) mediates the responses of mammalian cells to hypoxia/ischemia by inducing the expression of adaptive gene products (e.g., vascular endothelial growth factor (VEGF) and erythropoietin (EPO)). Persistent pulmonary hypertension of the newborn (PPHN) and cyanotic congenital heart disease (CCHD) are common neonatal diseases considered as paradigms of hypoxemia. Since the expression HIF-1 alpha, VEGF and EPO in newborns diagnosed with these diseases has yet to be studied, we set out to define the expression of these genes in peripheral blood from newborn infants diagnosed with PPHN and CCHD.

DESIGN AND METHODS

The mRNA transcripts encoding HIF-1 alpha, VEGF and EPO were measured by RT-PCR in healthy newborn infants and infants diagnosed with PPHN and CCHD.

RESULTS

An important increase in HIF-1 alpha expression was observed in both pathological conditions, accompanied by significant increases in VEGF and EPO expression when compared to healthy infants.

CONCLUSIONS

HIF-1 alpha mRNA expression increases in newborn infants with PPHN or CCHD, as does the expression of its target genes VEGF and EPO.