The lysis of red blood cells was shown to occur in human ruptured atherosclerotic lesions and intraventricular hemorrhage (IVH) of the brain. Liberated cell-free hemoglobin was found to undergo oxidation in both pathologies. We hypothesize that hemoglobin-derived peptides are generated during hemoglobin oxidation both in complicated atherosclerotic lesions and IVH of the brain, triggering endothelial cell dysfunction. Oxidized hemoglobin and its products were followed with spectrophotometry, LC–MS/MS analysis and detection of the cross-linking of globin chains in complicated atherosclerotic lesions of the human carotid artery and the hemorrhaged cerebrospinal liquid of preterm infants. The vascular pathophysiologic role of oxidized hemoglobin and the resultant peptides was assessed by measuring endothelial integrity, the activation of endothelial cells and the induction of proinflammatory genes. Peptide fragments of hemoglobin (VNVDEVGGEALGRLLVVYPWTQR, LLVVYPWTQR, MFLSFPTTK, VGAHAGEYGAELERMFLSFPTTK, and FLASVSTVLTSKYR) were identified in ruptured atherosclerotic lesions and in IVH of the human brain. Fragments resulting from the oxidation of hemoglobin were accompanied by the accumulation of ferryl hemoglobin. Similar to complicated atherosclerotic lesions of the human carotid artery, a high level of oxidized and cross-linked hemoglobin was observed in the cerebrospinal fluid after IVH. Haptoglobin inhibited hemoglobin fragmentation provoked by peroxide. The resultant peptides failed to bind haptoglobin or albumin. Peptides derived from hemoglobin oxidation and ferryl hemoglobin induced intercellular gap formation, decreased junctional resistance in the endothelium, and enhanced monocyte adhesion to endothelial cells. Enhanced expression of TNF and the activation of NLRP3 and CASP1 followed by the increased generation of IL-1β and nuclear translocation of the NF-κβ transcription factor occurred in response to hemoglobin-derived peptides, and ferryl hemoglobin in endothelium was upregulated in both pathologies. We conclude that the oxidation of hemoglobin in complicated atherosclerotic lesions and intraventricular hemorrhage of the brain generates peptide fragments and ferryl hemoglobin with the potential to trigger endothelial cell dysfunction.

Objective— Calcific aortic valve disease is a prominent finding in elderly and in patients with chronic kidney disease. We investigated the potential role of iron metabolism in the pathogenesis of calcific aortic valve disease. Approach and Results— Cultured valvular interstitial cells of stenotic aortic valve with calcification from patients undergoing valve replacement exhibited significant susceptibility to mineralization/osteoblastic transdifferentiation in response to phosphate. This process was abrogated by iron via induction of H-ferritin as reflected by lowering ALP and osteocalcin secretion and preventing extracellular calcium deposition. Cellular phosphate uptake and accumulation of lysosomal phosphate were decreased. Accordingly, expression of phosphate transporters Pit1 and Pit2 were repressed. Translocation of ferritin into lysosomes occurred with high phosphate-binding capacity. Importantly, ferritin reduced nuclear accumulation of RUNX2 (Runt-related transcription factor 2), and as a recipr...

Background and Purpose: Calcification of heart valves is a frequent pathological finding in chronic kidney disease and in elderly patients. Hydrogen sulfide (H₂S) may exert anti‐calcific actions. Here we investigated H₂S as an inhibitor of valvular calcification and to identify its targets in the pathogenesis.Experimental Approach: Effects of H₂S on osteoblastic transdifferentiation of valvular interstitial cells (VIC) isolated from samples of human aortic valves were studied using immunohistochemistry and western blots. We also assessed H2S on valvular calcification in apolipoprotein E‐deficient (ApoE^−/−) mice.Key Results: In human VIC, H₂S from donor compounds (NaSH, Na₂S, GYY4137, AP67, and AP72) inhibited mineralization/osteoblastic transdifferentiation, dose‐dependently in response to phosphate. Accumulation of calcium in the extracellular matrix and expression of osteocalcin and alkaline phosphatase was also inhibited. RUNX2 was not translocated to the nucleus and phosphate uptake was decreased. Pyrophosphate generation was increased via up‐regulating ENPP2 and ANK1. Lowering endogenous production of H₂S by concomitant silencing of cystathionine γ‐lyase (CSE) and cystathionine β‐synthase (CBS) favoured VIC calcification. analysis of human specimens revealed higher Expression of CSE in aorta stenosis valves with calcification (AS) was higher than in valves of aortic insufficiency (AI). In contrast, tissue H₂S generation was lower in AS valves compared to AI valves. Valvular calcification in ApoE^−/− mice on a high‐fat diet was inhibited by H₂S.Conclusions and Implications: The endogenous CSE‐CBS/H₂S system exerts anti‐calcification effects in heart valves providing a novel therapeutic approach to prevent hardening of valves.Linked Articles: This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc

Hemoglobin, heme and iron are implicated in the progression of atherosclerosis. Therefore, we investigated whether the hydrophobic fungal iron chelator siderophore, desferricoprogen (DFC) inhibits atherosclerosis. DFC reduced atherosclerotic plaque formation in ApoE^−/− mice on an atherogenic diet. It lowered the plasma level of oxidized LDL (oxLDL) and inhibited lipid peroxidation in aortic roots. The elevated collagen/elastin content and enhanced expression of adhesion molecule VCAM-1 were decreased. DFC diminished oxidation of Low-density Lipoprotein (LDL) and plaque lipids catalyzed by heme or hemoglobin. Formation of foam cells, uptake of oxLDL by macrophages, upregulation of CD36 and increased expression of TNF-α were reduced by DFC in macrophages. TNF-triggered endothelial cell activation (vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecules (ICAMs), E-selectin) and increased adhesion of monocytes to endothelium were attenuated. The increased endothelial permeability and intracellular gap formation provoked by TNF-α was also prevented by DFC. DFC acted as a cytoprotectant in endothelial cells and macrophages challenged with a lethal dose of oxLDL and lowered the expression of stress-responsive heme oxygenase-1 as sublethal dose was employed. Saturation of desferrisiderophore with iron led to the loss of the beneficial effects. We demonstrated that DFC accumulated within the atheromas of the aorta in ApoE^−/− mice. DFC represents a novel therapeutic approach to control the progression of atherosclerosis.

Abdominal aortic aneurysm (AAA) is a lethal vascular disease characterized by intramural hemorrhage. This study delineates the signatures of heme and its metabolic imbalance related to progression and inflammation in AAA. Clinical analyses of patients undergoing open AAA surgery show that AAA patients exhibit vascular inflammation, with elevated serum CRP, IL-6, and heme levels correlating with the expression of heme-regulated gene Hmox1/HO-1 (heme oxygenase-1) in the affected aortic wall. Oxidation of hemoglobin to ferri state leading to accumulation of methemoglobin readily releasing heme occurs in human AAA and in angiotensin II (AngII)-induced AAA in apolipoprotein E-deficient mice. Transcriptomic analysis for AngII-induced AAA identifies upregulated genes predominantly enriched in inflammatory signaling, extracellular matrix degradation, oxidative stress pathways, and altered expression of genes related to heme metabolism including Hmox1. Immunohistochemistry for IL1β and TNFα confirms inflammatory activation within AAA tissues. The signatures of heme-responsive gene inductions, enhanced expression of HO-1 and H-ferritin, are detected. Mechanistic studies employing endothelial cells and smooth muscle cells reveal that heme exposure of resident cells markedly enhances the expression of IL1β and ICAM1, as well as the inflammasome component NLRP3, and such inflammatory response is controlled by HO-1. Intervention with Normosang (heme arginate), an HO-1 inducer, attenuates aneurysm progression, whereas HO-1 inhibition by Tin protoporphyrin IX abolishes this protection. Induction of HO-1 accompanied by elevated H-ferritin level also mitigated aortic wall inflammation as reflected by lowering IL1β and TNFα. These findings highlight the heme-HO-1-H-ferritin axis as an element of AAA pathogenesis and a potential therapeutic target.