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Mechanisms of haptoglobin protection against hemoglobin peroxidation triggered endothelial damage

ABSTRACT: Extracellular hemoglobin (Hb) has been recognized as a disease trigger in hemolytic conditions such as sickle cell disease, malaria and blood transfusion. In vivo, many of the adverse effects of free Hb can be attenuated by the Hb scavenger acute phase protein haptoglobin (Hp). The primary physiologic disturbances that can be caused be free Hb are found within the cardiovascular system and Hb triggered oxidative toxicity towards the endothelium has been promoted as a potential mechanism. The molecular mechanisms of this toxicity as well as of the protective activities of Hp are not yet clear. Within this study we systematically investigated the structural, biochemical and cell biologic nature of Hb toxicity in an endothelial cell system under peroxidative stress. We identified two principal mechanisms of oxidative Hb toxicity that are mediated by globin degradation products and by modified lipoprotein species, respectively. The two damage pathways trigger diverse and discriminative inflammatory and cytotoxic responses. Hp provides structural stabilization of Hb and shields Hb’s oxidative reactions with lipoproteins providing dramatic protection against both pathways of toxicity. By these mechanisms Hp shifts Hb’s destructive pseudo-peroxidative reaction into a potential anti-oxidative function during peroxidative stress.

ORGANISM(S): Homo sapiens

PROVIDER: GSE46471 | GEO | 2015/04/30

SECONDARY ACCESSION(S): PRJNA200580

REPOSITORIES: GEO

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Mechanisms of haptoglobin protection against hemoglobin peroxidation triggered endothelial damage

Project description:Extracellular hemoglobin (Hb) has been recognized as a disease trigger in hemolytic conditions such as sickle cell disease, malaria and blood transfusion. In vivo, many of the adverse effects of free Hb can be attenuated by the Hb scavenger acute phase protein haptoglobin (Hp). The primary physiologic disturbances that can be caused be free Hb are found within the cardiovascular system and Hb triggered oxidative toxicity towards the endothelium has been promoted as a potential mechanism. The molecular mechanisms of this toxicity as well as of the protective activities of Hp are not yet clear. Within this study we systematically investigated the structural, biochemical and cell biologic nature of Hb toxicity in an endothelial cell system under peroxidative stress. We identified two principal mechanisms of oxidative Hb toxicity that are mediated by globin degradation products and by modified lipoprotein species, respectively. The two damage pathways trigger diverse and discriminative inflammatory and cytotoxic responses. Hp provides structural stabilization of Hb and shields Hb’s oxidative reactions with lipoproteins providing dramatic protection against both pathways of toxicity. By these mechanisms Hp shifts Hb’s destructive pseudo-peroxidative reaction into a potential anti-oxidative function during peroxidative stress. HPAEC: A two color common reference design was chosen with 4-8 independent biological replicates of each condition. Each experimental sample (Cy5 labeled) was hybridized against a non-treated reference sample (Cy3 labeled). HUVEC: A two color common reference design was chosen with 3-4 independent biological replicates of each condition. Each experimental sample (Cy5 labeled) was hybridized against a non-treated reference sample (Cy3 labeled).

2015-04-30 | E-GEOD-46471 | biostudies-arrayexpress

Different target specificities of haptoglobin and hemopexin define their sequential role as primary and backup protective systems against hemoglobin toxicity

Project description:Hemoglobin (Hb) released from red blood cells during hemolysis is a trigger of oxidative vascular damage with endothelial cells being a primary target. The Hb and heme scavenger proteins haptoglobin (Hp) and hemopexin (Hx) have been characterized as a sequential defense system with Hp as the primary protector and Hx as a backup when all Hp is depleted during more severe or prolonged hemolysis. The paradigm of sequential protection by the two scavengers is based on observational patient data proposed by Mueller-Eberhardt. In this study we present a mechanistic rationale for these clinical observations using a novel in vitro model of Hb triggered endothelial damage. We identified oxyHb(Fe2+) transformation to ferric Hb(Fe3+), free heme transfer from ferric Hb(Fe3+) to lipoprotein and subsequent oxidative reactions in the lipophilic phase. The accumulation of toxic lipid peroxidation products liberated during oxidation reactions lead to endothelial damage characterized by a specific gene expression pattern, reduced cellular ATP and monolayer disintegration. Quantitative analysis of key biochemical and functional parameters allowed us to precisely define the mechanisms and concentrations required for Hp and Hx to prevent this toxicity. In the case of Hp we defined an exponential relationship between Hp availability relative to oxyHb(Fe2+) and related protective activity. This exponential relationship demonstrates that large Hp quantities are required to prevent Hb toxicity. In contrast, the linear relationship between Hx concentration and protective activity allows for significant protection by the backup scavenger during conditions of large excess of free oxyHb(Fe2+) that occurs when all Hp is consumed. The diverse protective function of Hp and Hx in this model can be explained by the different target specificities of the two proteins.

2018-02-25 | GSE66283 | GEO

Hydroxyl radical footprinting analysis of a human haptoglobin-hemoglobin complex

Project description:Methods of structural mass spectrometry have become more popular to study protein structure and dynamics. Among them, fast photochemical oxidation of proteins (FPOP) has several advantages such as irreversibility of modifications and more facile determination of the site of modification with single residue resolution. In the present study, FPOP analysis was applied to study the hemoglobin (Hb) – haptoglobin (Hp) complex allowing identification of respective regions altered upon the complex formation. The footprinting using a timsTOF Pro mass spectrometer allowed to obtain structural information for 84 and 76 residues in Hp and Hb, respectively, including statistically significant differences in the modification extent below 0.3 %. The most affected residues upon the complex formation were Met76 and Tyr140 in Hbα, and Tyr280 and Trp284 in Hpβ. The data allowed determination of amino acids directly involved in Hb – Hp interactions and those located outside of the interaction interface yet affected by the complex formation. Also, previously modeled interaction between Hb βTrp37 and Hp βPhe292 was not confirmed by our data.

2021-12-30 | PXD021621 | Pride

Microarray identification of functional modules involving Haptoglobin and/or Hemopexin

Project description:Haptoglobin and Hemopexin are plasma acute phase proteins that bind with high affinity hemoglobin and heme, respectively. Several studies have demonstrated that they have a key role in the protection against oxidative stress and inflammation. However, little is known about the functional modules in which they are involved. To gain insights into this issue, we integrated bioinformatic and experimental approaches to identify genes coexpressed with Haptoglobin or Hemopexin and modulated in Haptoglobin and/or Hemopexin knock-out mice. These genes have a high probability to be functionally related to Haptoglobin and/or Hemopexin. We performed a gene expression analysis of the livers of Hp- and/or Hx-null mice compared to wild-type controls. The mice used in the following experiments, i.e. wild-type (Hp+/Hx+/), Hp-null (Hp-/-Hx+/), Hx-null (Hp+/Hx-/-), and HpHx-null (Hp-/-Hx-/-), were littermates derived by breeding F1 double heterozygous Hp+/-Hx+/- mice in the mixed genetic background C57/BLJ6 X 129Sv. We have three experimental points: Hx-null mice, Hp-null mice and HpHx-null mice. At least 5 adult mice per genotype were perfused via aorta with PBS, sacrificed and their liver pooled. Thirty microgram of total RNA were subjected to direct labeling reaction by incorporation of cyanin 3 (Cy3) or cyanin 5 (Cy5) fluorescent dyes into the cDNA by priming with oligo(dT). Four replicates were set up for each experimental point. In order to exclude artifacts resulting from different dye usage, we employed the dye-swap approach.

2006-10-31 | E-GEOD-3656 | biostudies-arrayexpress

Microarray identification of functional modules involving Haptoglobin and/or Hemopexin

2006-11-01 | GSE3656 | GEO

Tumor ENPP1(CD203a)/Haptoglobin Axis Exploits Myeloid-Derived Suppressor Cells to Promote Post-Radiotherapy Local Recurrence in Breast Cancer [array]

Project description:Locoregional failure (LRF) in breast cancer patients post-surgery and post-irradiation (IR) is linked to a dismal prognosis. In a refined new model, we identified Enpp1 (Ectonucleotide pyrophosphatase /phosphodiesterase 1/CD203a) to be closely associated with LRF. Enpp1high circulating tumor cells (CTC) contribute to relapse by a self-seeding mechanism. This process requires the infiltration of PMN-MDSC and neutrophil extracellular traps (NET) formation. Genetic and pharmacological Enpp1 inhibition or NET blockade extend relapse-free survival. Furthermore, in combination with fractionated irradiation (FD), Enpp1 abrogation obliterates LRF. Mechanistically, Enpp1-generated adenosinergic metabolites enhance Haptoglobin (Hp) expression. This inflammatory mediator elicits myeloid invasiveness and promotes NET formation. Accordingly, a significant increase in ENPP1 and NET formation is detected in relapsed human breast cancer tumors. Moreover, high ENPP1 or HP levels are associated with poor prognosis. These findings unveil the ENPP1/HP axis as an unanticipated mechanism exploited by tumor cells linking inflammation to immune remodeling favoring local relapse.

2022-01-17 | GSE193691 | GEO

Effect of haptoglobin (purified from human serum) on gene expression in monocyte-derived macrophages.

Project description:Haptoglobin is a major serum protein that sequesters free hemoglobin. Moreover, haptoglobin regulates the inflammatory response in the absence of hemoglobin. Conflicting functional outcomes are reported, whereas involvement of NFκB is suggested consistently. Our data indicate that purified haptoglobin induces NFκB-dependent transcription through toll-like receptor 4. Notably, haptoglobin itself is dispensable for this effect. We show here that haptoglobin binds lipopolysaccharides from different bacterial species with micromolar affinities. This finding explains previous divergent observations. Pro-inflammatory responses elicited by purified haptoglobin are caused by heterogeneous lipopolysaccharides associated with the protein. Given its abundance in human serum, haptoglobin constitutes a buffer for serum-borne lipopolysaccharide. Restricted lipopolysaccharide availability dampens inflammatory responses. Concordantly, NFκB activation in primary macrophages is delayed relative to stimulation with pure lipopolysaccharide. Our findings warrant evaluation of therapeutic benefits of haptoglobin for non-hemolytic conditions as well as re-evaluation of purification strategies and will furthermore allow to disentangle mechanisms of haptoglobin-dependent immunoregulation.

2022-10-24 | GSE215916 | GEO

Targeting Circulating Labile Heme as a Defense Strategy Against Malaria

Project description:Severe presentations of malaria emerge as parasites from Plasmodium spp. proliferate and lyse red blood cells (RBC), producing extracellular hemoglobin (HB). The heme prosthetic groups are released upon HB oxidation generating circulating labile heme. Here we asked whether scavenging of extracellular HB and/or labile heme, by haptoglobin (HP) and/or hemopexin (HPX), respectively, is protective against severe presentations of malaria. We found that circulating labile heme is an independent risk factor for cerebral and non-cerebral severe presentations of P. falciparum malaria. Labile heme was negatively correlated with HP and HPX, which were however, not risk factors for severe P. falciparum malaria. Genetic HP and/or HPX deletion in mice led to accumulation of labile heme in plasma and kidneys in response to Plasmodium (chabaudi chabaudi) infection. This was associated with increased mortality and acute kidney injury (AKI) in ageing but not adult mice, corroborated in P. falciparum malaria by a an inverse correlation between HPX and heme with serological markers of AKI. In conclusion, HP and HPX exert an age-dependent protective effect against malaria that counters the pathogenesis of AKI in mice and presumably in humans.

2024-01-30 | GSE253390 | GEO

Transcription profiling of human vascular smooth muscle cells treated with glucose oxidase and human haemoglogib reveals ferrous hemoglobin can protect vascular smooth muscle cells from hydrogen peroxide-induced oxidative stress response and cell damage

Project description:Hemoglobin (Hb) is released from red blood cells (RBC) during intravascular hemolysis. Cell free Hb has been implicated to play a pathogenic role in hemolytic diseases such as sickle cell anemia or malaria. Hydrogen peroxide (H2O2) is the most prevalent reactive oxygen species which is produced in excess during inflammation or tissue injury and has been included as a potential mediator of oxidative stress related cell and tissue damage. The biologic significance of Hbs peroxidase activity as an anti-oxidant is controversial as the radicals and higher oxidation iron species which are potentially released during these reactions could be a source of exaggerated oxidative damage. Using a cell culture model of low-flux continuous H2O2 generation by glucose-oxidase (GOx) Hb revealed the potential to protect vascular smooth muscle cells and macrophages from H2O2 mediated glutathione depletion and cell death. As revealed by gene array analysis, Hb effectively abolished H2O2 induced oxidative stress response in these cells. Through electron microscopy and quantitative mass spectrometry extensive oxidation of specific Hb amino acid residues, polymerization and precipitation was defined. This may be a consequence of potential protective mechanism within Hb. The net biologic effect of Hb, when present in oxidative rich environments, is likely a result of the balance of H2O2 consumption (protection) on one hand and the production of free radicals (damage) on the other hand. Further the extensive structural changes occurring during the reaction of ferrous Hb with H2O2 could 'absorb' a significant amount of oxidative impact and thereby further protect the environment from heme derived free radical damage. The intrinsic peroxidase activity of hemoglobin seems to be a constitutive 'enzymatic' function of Hb which adds a novel facet to the multivalent role played by the abundant oxygen carrier protein.

2009-09-15 | E-MEXP-2263 | biostudies-arrayexpress

PRM-MS quantitative analysis of isomeric N-glycopeptides derived from human serum haptoglobin of patients with cirrhosis and hepatocellular carcinoma

Project description:Comprehensive LC-PRM-MS approach where a targeted parallel reaction monitoring (PRM) strategy was coupled to a powerful LC system to study the microheterogeneity of serum haptoglobin (Hp) extracted from 15 patients with cirrhosis and 15 with hepatocellular carcinoma (HCC).

2021-09-10 | PXD023719 | Pride

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