Presence of hemoglobin inside aortic endothelial cells after cell-free hemoglobin administration in guinea pigs

Abstract

The endothelium is the production site of several potent vasoactive factors that contribute to the modulation of the vascular tone. Because hemoglobin-based oxygen carriers (HBOC) have been demonstrated to cause vasoconstriction and thereby increase arterial pressure by interacting with endothelium-derived factors such as nitric oxide and endothelin-1, we hypothesized that hemoglobin could penetrate into the endothelial cells. Therefore, we investigated the presence of hemoglobin into guinea pig aortic endothelial cells by immunohistochemical staining after exchange transfusion with a hemoglobin-based oxygen carrier. Despite the large molecular size of HBOC due to chemical modifications designed to prevent hemoglobin subunit dissociation and extravascular leakage, hemoglobin was detectable by immunohistochemical staining into the endothelial cells. These findings suggest that the vascular endothelial cells could uptake hemoglobin by endocytosis mechanisms or could help hemoglobin to cross the endothelial barrier toward media by transcytosis mechanisms. These findings are very important to lead future investigations to the mechanisms by which HBOC cause vasoconstriction.

Highly glycated oxyhaemoglobin impairs nitric oxide relaxations in human mesenteric microvessels

“…It is sensitive to changes in glycaemic concentrations [27], it circulates freely in plasma in nanomolar concentrations [7] and it can penetrate into the vascular wall in non-pathological circumstances [30,31]. Very recently it has been shown that endothelial cells are able to incorporate cell-free haemoglobin, creating a new way for circulating haemoglobin to be in close contact with NO [32]. Finally, we have recently described both in vitro and in vivo a high correlation between HbA 1 c values and endothelial dysfunction in rats with streptozotocin-induced diabetes [8,9].…”

Oxidized Ferric and Ferryl Forms of Hemoglobin Trigger Mitochondrial Dysfunction and Injury in Alveolar Type I Cells

“…In contrast to HbFe 21 , HbFe 31 reduced basal oxygen consumption rate, indicating compromised mitochondrial activity. However, HbFe 41 exposure not only induced early expression of HO-1 but also caused mitochondrial dysfunction within 12 hours when compared with HbFe 21 and HbFe 31 . Exposure to HbFe 41 for 24 hours also caused mitochondrial depolarization in E10 cells.…”

“…Exposure to HbFe 41 for 24 hours also caused mitochondrial depolarization in E10 cells. The deleterious effects of HbFe 31 and HbFe 41 were reversed by the addition of scavenger proteins, haptoglobin and hemopexin. Collectively, these data establish, for the first time, a central role for cell-free Hb in lung epithelial injury, and that these effects are mediated through the redox transition of Hb to higher oxidation states.…”

Dissociation of local nitric oxide concentration and vasoconstriction in the presence of cell-free hemoglobin oxygen carriers

“…2,3 Hb extravasation into the vessel wall is presumed to cause NO scavenging. 4,5 Polymerization of the protein that limits extravasation has in some cases elicited 6,7 or prevented 8 hypertension. In general, large conjugated or polymerized Hbs with increased effective molecular radii appear to be inversely correlated with the hypertensive response.…”