Dose-dependency for nitrite-induced hypoxic vasodilation in the presence and absence of myoglobin (Mb).

<p>(A) Experimental schema. After equilibration, normoxic gassing was either continued or changed to hypoxia (1% O₂). Isolated aortic rings of <i>Mb^+/+</i> and <i>Mb^−/−</i> mice were then pre-constricted using phenylephrine (Phe) and subsequently challenged with cumulating doses of nitrite from physiological to pharmacological levels. Under normoxia, nitrite-vasodilation response were identical in both mouse types (B) leading to similar EC₅₀ levels (C). On the contrary, under hypoxia, nitrite-induced vasodilation was significantly impaired in <i>Mb^−/−</i> (D) with significantly higher resulting EC₅₀ levels (E). All values are means±s.e.m.</p

Role of nitrite and reactive oxygen species (ROS) in hypoxic vasodilation – proposed mechanism.

<p>Nitrite derives from NO^• synthesis dietary sources. NO^• to nitrite reactions occur by autoxidation or by reaction with ceruloplasmin (CP). Under hypoxia, nitrite levels in the vessel wall are increased. Nitrite can then be reduced to vasodilatory NO^• particularly by reaction with myoglobin (Mb). ROS modulate this response.</p

Nitrite and nitrate levels in mouse tissue.

<p>Aortic tissue of NMRI wild-types, myoglobin (Mb) deficient mice, C57BL/6 wild-types and endothelial nitric oxide synthase (eNOS) knockout mice was analyzed for (A) nitrite and (B) nitrate levels with no significant difference between the species as a prerequisite for dose-response experiments (n = 5–6, means±s.d.).</p

Endogenous ROS modulate the nitrite-induced hypoxic vasodilation response.

<p>(A) Experimental schema. After an equilibration period, SOD, SOD mimic tempol, catalase and gluthation peroxidase mimic ebselen were added to the organ bath in order to decompose endogenously formed ROS. The nitrite concentration in the organ bath was 300 nM. Vessels were then preconstricted with phenylephrine (Phe). After stabilization of constriction, hypoxic was induced and vasodilation observed for the following 15 min. (B) Graph shows the decrease in intention for the 15 min of hypoxia for controls and treated rings. Incubation of SOD mimic tempol with catalase and with catalase/ebselen significantly increased the vasodilation response at 10 and 15 min (*<i>P</i><0.05, n = 3–5). Values are means±s.e.m.</p

Hypoxia-induced myoglobin desaturation.

<p>Gassing with a 1% oxygen gas mixture leads to shift of the UV vis spectrum from oxygenated myoglobin (oxyMb) to deoxygenated myoglobin (deoxyMb). Figure shows final levels of saturation with a significant reduction under hypoxic gassing (means±s.d).</p

Procedural Characteristics.

<p>Procedural Characteristics.</p

Cell-free plasma hemoglobin, flow-mediated dilation (FMD) and hemoglobin.

<p>(A) Reduction of cell-free plasma hemoglobin (cell-free Hb) is observed 3 months following PMVR. (B) Increased endothelial functions after PMVR. (C) No change is observed for Hb. Data given as mean±SD, n = 27. * denotes p <0.05.</p

Decompartmentalization of hemoglobin is associated with endothelial dysfunction in MR and improved following PMVR.

<p>Cell-free plasma hemoglobin (cell-free Hb) increases and flow-mediated dilation (FMD) significantly decreases following PMVR. Baseline data are given in black, three month follow-up in red. Data given as mean±SD, n = 27. *Each p <0.05.</p

Basic clinical and biochemical characteristics.

<p>Basic clinical and biochemical characteristics.</p

Vascular function and blood parameters following PMVR.

<p>Vascular function and blood parameters following PMVR.</p