Role of Dietary Antioxidants in the Preservation of Vascular Function and the Modulation of Health and Disease

In vascular diseases, including hypertension and atherosclerosis, vascular endothelial dysfunction (VED) occurs secondary to altered function of endothelial nitric oxide synthase (eNOS). A novel redox regulated pathway was identified through which eNOS is uncoupled due to S-glutathionylation of critical cysteine residues, resulting in superoxide free radical formation instead of the vasodilator molecule, nitric oxide. In addition, the redox sensitive cofactor tetrahydrobiopterin, BH4, is also essential for eNOS coupling. Antioxidants, either individually or combined, can modulate eNOS uncoupling by scavenging free radicals or impairing specific radical generating pathways, thus preventing oxidative stress and ameliorating VED. Epidemiological evidence and dietary guidelines suggest that diets high in antioxidants, or antioxidant supplementation, could preserve vascular health and prevent cardiovascular diseases (CVDs). Therefore, the purpose of this review is to highlight the possible role of dietary antioxidants in regulating eNOS function and uncoupling which is critical for maintenance of vascular health with normal blood flow/circulation and prevention of VED. We hypothesize that a conditioned dietary approach with suitable antioxidants may limit systemic oxidation, maintain a beneficial ratio of reduced to oxidized glutathione, and other redox markers, and minimize eNOS uncoupling serving to prevent CVD and possibly other chronic diseases

Targeting the Nrf2/ARE Signalling Pathway to Mitigate Isoproterenol-Induced Cardiac Hypertrophy: Plausible Role of Hesperetin in Redox Homeostasis

Cardiac hypertrophy is the underlying cause of heart failure and is characterized by excessive oxidative stress leading to collagen deposition. Therefore, understanding the signalling mechanisms involved in excessive extracellular matrix deposition is necessary to prevent cardiac remodelling and heart failure. In this study, we hypothesized that hesperetin, a flavanone that elicits the activation of Nrf2 signalling and thereby suppresses oxidative stress, mediated pathological cardiac hypertrophy progression. A cardiac hypertrophy model was established with subcutaneous injection of isoproterenol in male Wistar rats. Oxidative stress markers, antioxidant defense status, and its upstream signalling molecules were evaluated to discover the impacts of hesperetin in ameliorating cardiac hypertrophy. Our results implicate that hesperetin pretreatment resulted in the mitigation of oxidative stress by upregulating antioxidant capacity of the heart. This curative effect might be owing to the activation of the master regulator of antioxidant defense system, known as Nrf2. Further, analysis of Nrf2 revealed that hesperetin enhances its nuclear translocation as well as the expression of its downstream targets (GCLC, NQO1, and HO-1) to boost the antioxidative status of the cells. To support this notion, in vitro studies were carried out in isoproterenol-treated H9c2 cells. Immunocytochemical analysis showed augmented nuclear localization of Nrf2 implicating the action of hesperetin at the molecular level to maintain the cellular redox homeostasis. Thus, it is conceivable that hesperetin could be a potential therapeutic candidate that enhances Nrf2 signalling and thereby ameliorates pathological cardiac remodelling

Synthesis, photoluminescence and Judd-Ofelt parameters of LiNa3P2O7:Eu3+ orthorhombic microstructures

We report, for the first time, the photoluminescence properties of Eu3+-doped LiNa3P2O7 phosphor, synthesized by a facile solid-state reaction method in air atmosphere. The crystal structure and phase purity of the phosphors were analyzed by X-ray diffraction analysis. Orthorhombic structural morphology was identified by scanning electron microscopy. The phosphate groups in the phosphor were confirmed by Fourier transform infrared analysis. Bandgap of the phosphor was calculated from the diffuse reflectance spectra data using Kubelka-Munk function. Under 395-nm UV excitation, the phosphors show signs of emitting red color due to the D-5(0) -> F-7(2) transition. In accordance with Judd-Ofelt theory, spectroscopic parameters such as oscillator intensity parameter Omega(t) (t = 2), spontaneous emission probabilities, fluorescence branching ratios and radiative lifetimes were calculated and analyzed for the first time in this system

Arterial Levels of Oxygen Stimulate Intimal Hyperplasia in Human Saphenous Veins via a ROS-Dependent Mechanism

<div><p>Saphenous veins used as arterial grafts are exposed to arterial levels of oxygen partial pressure (pO₂), which are much greater than what they experience in their native environment. The object of this study is to determine the impact of exposing human saphenous veins to arterial pO₂. Saphenous veins and left internal mammary arteries from consenting patients undergoing coronary artery bypass grafting were cultured ex vivo for 2 weeks in the presence of arterial or venous pO₂ using an established organ culture model. Saphenous veins cultured with arterial pO₂ developed intimal hyperplasia as evidenced by 2.8-fold greater intimal area and 5.8-fold increase in cell proliferation compared to those freshly isolated. Saphenous veins cultured at venous pO₂ or internal mammary arteries cultured at arterial pO₂ did not develop intimal hyperplasia. Intimal hyperplasia was accompanied by two markers of elevated reactive oxygen species (ROS): increased dihydroethidium associated fluorescence (4-fold, p<0.05) and increased levels of the lipid peroxidation product, 4-hydroxynonenal (10-fold, p<0.05). A functional role of the increased ROS saphenous veins exposed to arterial pO₂ is suggested by the observation that chronic exposure to tiron, a ROS scavenger, during the two-week culture period, blocked intimal hyperplasia. Electron paramagnetic resonance based oximetry revealed that the pO₂ in the wall of the vessel tracked that of the atmosphere with a ~30 mmHg offset, thus the cells in the vessel wall were directly exposed to variations in pO₂. Monolayer cultures of smooth muscle cells isolated from saphenous veins exhibited increased proliferation when exposed to arterial pO₂ relative to those cultured at venous pO₂. This increased proliferation was blocked by tiron. Taken together, these data suggest that exposure of human SV to arterial pO₂ stimulates IH via a ROS-dependent pathway.</p></div

ROS levels in freshly isolated and cultured SV as assessed by DHE staining.

<p>(A) DHE and DAPI staining of freshly isolated SV and SV cultured at arterial or venous pO₂. Scale bar is 100 μm. (B) Average normalized mean of DHE fluorescence intensity (n = 3). * indicates p<0.05 relative to other groups marked with #. There were no intragroup differences among subgroups marked with #.</p

Oxygen levels within the wall of SV cultured at various levels of pO₂ and the impact of pO₂ on the proliferation of cultured SMC.

<p>(A) Arrow indicates location of the black EPR probe within SV cultured ex vivo for internal pO₂ measurements. Intima and adventitia are labeled to show vessel orientation. Scale bar is 50 μm. (B) Quantification of oxygen levels within intact SV as measured by EPR probe. SV were in ex vivo culture at pO₂ of either 40 (venous), 95 (arterial) or 140 mmHg (typical cell culture atmosphere). Cell number as a function of time during culture for SMC isolated from HSV (C) and 3T3 fibroblasts (D). Isolated SMC were cultured at venous pO₂ or at arterial pO₂, with and without tiron. NIH3T3 fibroblasts were cultured at venous or arterial pO₂. *indicates statistically different compared to other groups at corresponding time point. Standard deviations bars are not visible when their size is small compared to the size of the symbols indicating means.</p

Quantification of intimal area.

<p>(A) Histogram of intimal areas for freshly isolated SV and SV cultured at arterial pO₂. (B) Normalized intimal area of SV (n≥6) and IMA (n = 4) when either freshly harvested or cultured at venous, arterial and typical cell culture pO₂. * indicates p<0.05 relative to other groups.</p

Elastin-stained sections from freshly harvested SV and SV cultured for 14 days.

<p>In Panels A, C, and D the and the IEL, which stain black, are intact and there is no neointimal formation. In Panel B there is rupture in the IEL (breaks in IEL indicated with black arrows) allowing cells from the media to migrate into the intima. Scale bar is 100 μm.</p

Distribution and levels of 4-HNE adducts in freshly isolated and cultured SV.

<p>(A) SV immunostained for 4-HNE adducts. Positive staining is shown in dark brownish black and detects levels of lipid peroxidation due to ROS. Conditions shown are freshly isolated (I), and after being cultured at venous pO₂ (II) or arterial pO₂ without (III) and with tiron (VI). Scale bar is 100 μm. (B) Western blot for 4-HNE adducts. Gels contained samples not related to the present study and these lanes are not shown. Noncontiguous gel lanes are demarcated by a vertical white line. (C) Quantification of 4-HNE normalized to actin amount. *p<0.05 relative to group marked with #.</p