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1.  Hypoxia‐inducible factor expression in human RPE cells 
The British Journal of Ophthalmology  2007;91(10):1406-1410.
Hypoxia‐inducible factor (HIF) is a common transcription factor for many angiogenic proteins. Retinal pigment epithelial (RPE) cells are an important source of angiogenic factors in the retina. The expression of HIF, its regulation by proline hydroxylase (PHD) enzymes, and its downstream regulation of angiogenic factors like vascular endothelial growth factor (VEGF) and erythropoietin (EPO) was studied in RPE cells in order to determine some of the molecular mechanisms underlying ischaemic retinal disease.
ARPE‐19 cells were cultured for various times under hypoxic conditions. Cellular HIF and PHD isoforms were analysed and quantified using western blot and densitometry. VEGF and EPO secreted into the media were assayed using enzyme‐linked immunosorbent assay (ELISA). Messenger RNA (mRNA) was quantified using real‐time quantitative reverse transcriptase polymerase chain reaction (qPCR). RNA interference was achieved using siRNA techniques.
HIF‐1α was readily produced by ARPE‐19 cells under hypoxia, but HIF‐2α and HIF‐3α could not be detected even after HIF‐1α silencing. HIF‐1α protein levels showed an increasing trend for the first 24 h while HIF‐1α mRNA levels fluctuated during this time. After 36 h HIF‐1α protein levels declined to baseline levels, a change that was coincident with a rise in both PHD2 and PHD3. Silencing HIF‐1α significantly decreased VEGF secretion. Significant production of EPO could not be detected at the protein or mRNA level.
HIF‐1α appears to be the main isoform of HIF functioning in ARPE‐19 cells. Under hypoxia, HIF‐1α levels are likely self‐regulated by a feedback loop that involves both transcriptional and post‐translational mechanisms. VEGF production by human RPE cells is regulated by HIF‐1α. EPO was not produced in significant amounts by RPE cells under hypoxic conditions, suggesting that other cells and/or transcription factors in the retina are responsible for its production.
PMCID: PMC2001032  PMID: 17567660
diabetic retinopathy; VEGF; erythropoietin; hypoxia‐inducible factor; proline hydroxylase
2.  Ventral Tegmental Area BDNF Induces an Opiate-Dependent–Like Reward State in Naïve Rats 
Science (New York, N.Y.)  2009;324(5935):1732-1734.
The neural mechanisms underlying the transition from a drug-nondependent to a drug-dependent state remain elusive. Chronic exposure to drugs has been shown to increase brain-derived neurotrophic factor (BDNF) levels in ventral tegmental area (VTA) neurons. BDNF infusions into the VTA potentiate several behavioral effects of drugs, including psychomotor sensitization and cue-induced drug seeking. We found that a single infusion of BDNF into the VTA promotes a shift from a dopamine-independent to a dopamine-dependent opiate reward system, identical to that seen when an opiate-naïve rat becomes dependent and withdrawn. This shift involves a switch in the γ-aminobutyric acid type A (GABAA) receptors of VTA GABAergic neurons, from inhibitory to excitatory signaling.
PMCID: PMC2913611  PMID: 19478142

Results 1-2 (2)