Hypoxia causes increased expression of several proteins that have the potential to promote neovascularization. Vascular endothelial growth factor (VEGF) is up-regulated by hypoxia in the retina and plays a central role in the development of several types of ocular neovascularization, but the effects of other hypoxia-regulated proteins are less clear. Stromal-derived factor-1 (SDF-1) and its receptor, CXCR4, have hypoxia response elements in the promoter regions of their genes and are increased in hypoxic liver and heart. In this study, we found that SDF-1 and CXCR4 are increased in hypoxic retina, with SDF-1 localized in glial cells primarily near the surface of the retina and CXCR4 localized in bone marrow-derived cells. Glial cells also expressed CXCR4, which suggested the possibility of autocrine stimulation, but influx of bone marrow-derived cells is the major source of increased levels of CXCR4. High levels of VEGF in the retina in the absence of hypoxia also increased levels of Cxcr4 and Sdf1 mRNA. CXCR4 antagonists reduced influx of bone marrow-derived cells into ischemic retina and strongly suppressed retinal neovascularization, VEGF-induced subretinal neovascularization, and choroidal neovascularization. These data suggest that SDF-1 and CXCR4 contribute to the involvement of bone marrow-derived cells and collaborate with VEGF in the development of several types of ocular neovascularization. They provide new targets for therapeutic intervention that may help to bolster and supplement effects obtained with VEGF antagonists.

Our data support a role of HD-induced release of hemoglobin in the pathogenesis of endothelial dysfunction in patients with end-stage renal disease. Approaches that oxidize free plasma hemoglobin may restore NO bioavailability and may have potential beneficial effects on vascular function. (Influence of Hemodialysis on Endothel-Depending Dilatation of Peripheral Arteries; NCT00764192).

Chronic obstructive pulmonary disease (COPD) is a prevalent smoking-related disease for which no diseasealtering therapies currently exist. As dysregulated TGF-β signaling associates with lung pathology in patients with COPD and in animal models of lung injury induced by chronic exposure to cigarette smoke (CS), we postulated that inhibiting TGF-β signaling would protect against CS-induced lung injury. We first confirmed that TGF-β signaling was induced in the lungs of mice chronically exposed to CS as well as in COPD patient samples. Importantly, key pathological features of smoking-associated lung disease in patients, e.g., alveolar injury with overt emphysema and airway epithelial hyperplasia with fibrosis, accompanied CS-induced alveolar cell apoptosis caused by enhanced TGF-β signaling in CS-exposed mice. Systemic administration of a TGF-β-specific neutralizing antibody normalized TGF-β signaling and alveolar cell death, conferring improved lung architecture and lung mechanics in CS-exposed mice. Use of losartan, an angiotensin receptor type 1 blocker used widely in the clinic and known to antagonize TGF-β signaling, also improved oxidative stress, inflammation, metalloprotease activation and elastin remodeling. These data support our hypothesis that inhibition of TGF-β signaling through angiotensin receptor blockade can attenuate CS-induced lung injury in an established murine model. More importantly, our findings provide a preclinical platform for the development of other TGF-β-targeted therapies for patients with COPD.

Age-related macular degeneration (AMD), the leading cause of severe vision loss in the elderly, is a complex disease that results from genetic modifications that increase susceptibility to environmental exposures. Smoking, a major source of oxidative stress, increases the incidence and severity of AMD, and antioxidants slow progression, suggesting that oxidative stress plays a major role. Polymorphisms in the complement factor H (CFH) gene that reduce activity of CFH increase the risk of AMD. In this study we demonstrate an interaction between these two risk factors, because oxidative stress reduces the ability of an inflammatory cytokine, interferon-␥, to increase CFH expression in retinal pigmented epithelial cells. The interferon-␥-induced increase in CFH is mediated by transcriptional activation by STAT1, and its suppression by oxidative stress is mediated by acetylation of FOXO3, which enhances FOXO3 binding to the CFH promoter, reduces its binding to STAT1, inhibits STAT1 interaction with the CFH promoter, and reduces expression of CFH. Expression of SIRT1, a mammalian homolog of NAD-dependent protein deacetylase sir2, attenuated FOXO3 recruitment to the CFH regulatory region and reversed the H 2 O 2 -induced repression of CFH gene expression. These data suggest an important interaction between environmental exposure and genetic susceptibility in the pathogenesis of AMD and, by elucidating molecular signaling involved in the interaction, provide potential targets for therapeutic intervention.