Post-stroke inhibition of induced NADPH oxidase type 4 prevents oxidative stress and neurodegeneration

Ischemic stroke is the second leading cause of death worldwide. Only one moderately effective therapy exists, albeit with contraindications that exclude 90% of the patients. This medical need contrasts with a high failure rate of more than 1,000 pre-clinical drug candidates for stroke therapies. Thus, there is a need for translatable mechanisms of neuroprotection and more rigid thresholds of relevance in pre-clinical stroke models. One such candidate mechanism is oxidative stress. However, antioxidant approaches have failed in clinical trials, and the significant sources of oxidative stress in stroke are unknown. We here identify NADPH oxidase type 4 (NOX4) as a major source of oxidative stress and an effective therapeutic target in acute stroke. Upon ischemia, NOX4 was induced in human and mouse brain. Mice deficient in NOX4 (Nox4(-/-)) of either sex, but not those deficient for NOX1 or NOX2, were largely protected from oxidative stress, blood-brain-barrier leakage, and neuronal apoptosis, after both transient and permanent cerebral ischemia. This effect was independent of age, as elderly mice were equally protected. Restoration of oxidative stress reversed the stroke-protective phenotype in Nox4(-/-) mice. Application of the only validated low-molecular-weight pharmacological NADPH oxidase inhibitor, VAS2870, several hours after ischemia was as protective as deleting NOX4. The extent of neuroprotection was exceptional, resulting in significantly improved long-term neurological functions and reduced mortality. NOX4 therefore represents a major source of oxidative stress and novel class of drug target for stroke therapy

Hypoxia-inducible Factor-1 Activation in Nonhypoxic Conditions: The Essential Role of Mitochondrial-derived Reactive Oxygen Species

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor for responses to low oxygen. Here we report that the generation of mitochondrial reactive oxygen species are essential for regulating HIF-1 in normal oxygen conditions in the vasculature

Translating the oxidative stress hypothesis into the clinic: NOX versus NOS

Cardiovascular diseases remain the leading cause of death in industrialised nations. Since the pathomechanisms of most cardiovascular diseases are not understood, the majority of therapeutic approaches are symptom-orientated. Knowing the molecular mechanism of disease would enable more targeted therapies. One postulated underlying mechanism of cardiovascular diseases is oxidative stress, i.e. the increased occurrence of reactive oxygen species such as superoxide. Oxidative stress leads to a dysfunction of vascular endothelium-dependent protective mechanisms. There is growing evidence that this scenario also involves impaired nitric oxide (NO)-cyclic GMP signalling. Out of a number of enzyme families that can produce reactive oxygen species, NADPH oxidases stand out, as they are the only enzymes whose sole purpose is to produce reactive oxygen species. This review focuses on the clinically validated targets of oxidative stress, NO synthase (NOS) and the NO receptor, soluble guanylate cyclase as well as the source of ROS, e.g. NADPH oxidases. We place recent knowledge in the function and regulation of these enzyme families into clinical perspective. For a comprehensive overview of the biology and pharmacology of oxidative stress and possible other sources and targets, we refer to other literature overviews

The NOX toolbox: validating the role of NADPH oxidases in physiology and disease

Reactive oxygen species (ROS) are cellular signals but also disease triggers; their relative excess (oxidative stress) or shortage (reductive stress) compared to reducing equivalents are potentially deleterious. This may explain why antioxidants fail to combat diseases that correlate with oxidative stress. Instead, targeting of disease-relevant enzymatic ROS sources that leaves physiological ROS signaling unaffected may be more beneficial. NADPH oxidases are the only known enzyme family with the sole function to produce ROS. Of the catalytic NADPH oxidase subunits (NOX), NOX4 is the most widely distributed isoform. We provide here a critical review of the currently available experimental tools to assess the role of NOX and especially NOX4, i.e. knock-out mice, siRNAs, antibodies, and pharmacological inhibitors. We then focus on the characterization of the small molecule NADPH oxidase inhibitor, VAS2870, in vitro and in vivo, its specificity, selectivity, and possible mechanism of action. Finally, we discuss the validation of NOX4 as a potential therapeutic target for indications including stroke, heart failure, and fibrosis

Ferric carboxymaltose improves exercise capacity and quality of life in patients with pulmonary arterial hypertension and iron deficiency: A pilot study

Background: Pulmonary arterial hypertension (PAH) is a progressive condition harboring a poor prognosis. Iron deficiency in PAH correlates with disease severity and mortality. While replacement therapy may be beneficial, dietary iron absorption is impaired in PAH patients by hepcidin, a key regulatory protein of iron homoeostasis. We therefore assessed the therapeutic potential and safety of intravenous iron supplementation in patients with PAH and iron deficiency. Methods: 20 patients with PAH and iron deficiency, who were on stable targeted PAH therapy, received a single infusion of <= 1000 mg ferric carboxymaltose. All patients were assessed at baseline and two months after iron treatment. Exercise capacity was evaluated based on the 6-minute- walking distance (6MWD), and quality of life (QoL) was assessed by the SF-36 questionnaire (100 point scale). The effects were compared to 20 matched patients with stable PAH without iron deficiency who did not receive ferric carboxymaltose. Results: In iron deficient patients, iron supplementation led to a marked improvement of iron status (serum iron 5.7 +/- 0.4 to 11.1 +/- 1.1 mu mol/L, ferritin 29.3 +/- 6.3 to 145.2 +/- 25.4 mu g/L, transferrin saturation 7.5 +/- 0.7 to 19.3 +/- 2.3%, all p <= 0.001). Iron-deficient patients receiving ferric carboxymaltose showed a significant increase of the 6MWD from 346.5 +/- 28.3 to 374.0 +/- 25.5 m (p = 0.007), whereas no significant changes were found in the control group not receiving iron supplementation (6MWD 389.9 +/- 25.3 to 379.6 +/- 26.2 m; n.s.), resulting in a net increase in the 6MWD of 37.8 m (p = 0.003). This was associated with an improvement in QoL (SF-36 score from 44.3 +/- 3.7 to 50.6 +/- 3.6; p = 0.01). Only minimal side-effects were reported. Conclusions: These data indicate that parenteral iron supplementation with ferric carboxymaltose significantly improves exercise capacity and QoL and is well tolerated in patients with PAH and iron deficiency, and when administered in addition to targeted PAH therapies. Our results provide proof of concept for further studies evaluating the potential of iron as an adjunct in PAH treatment on a larger scale. (C) 2014 Published by Elsevier Ireland Ltd

Prognosis of persistent mitral regurgitation in patients undergoing transcatheter aortic valve replacement

Objective The objective of this study was to assess imaging predictors of mitral regurgitation (MR) improvement and to evaluate the impact of MR regression on long-term outcome in patients undergoing transcatheter aortic valve replacement (TAVR). Background Concomitant MR is a frequent finding in patients with severe aortic stenosis but usually left untreated at the time of TAVR. Methods Mitral regurgitation was graded by transthoracic echocardiography before and after TAVR in 677 consecutive patients with severe aortic stenosis. 2-year mortality was related to the degree of baseline and discharge MR. Morphological echo analysis was performed to determine predictors of MR improvement. Results 15.2% of patients presented with baseline MR >= 3 +, which was associated with a significantly decreased 2-year survival (57.7% vs. 74.4%, P = 3 +. Baseline parameters including non-severe baseline MR, the extent of mitral annular calcification and large annular dimension (>= 32 mm) predicted the likelihood of an improvement to MR <= 2 +. A score based on these parameters selected groups with differing probability of MR <= 2 + post TAVR ranging from 10.5 to 94.4% (AUC 0.816; P < 0.001), and was predictive for 2-year mortality. Conclusion Unresolved severe MR is a critical determinant of long term mortality following TAVR. Persistence of severe MR following TAVR can be predicted using selected parameters derived from TTE-imaging. These data call for close follow up and additional mitral valve treatment in this subgroup. Graphic abstract Factors associated with MR persistence or regression after TAVR [GRAPHICS]