Haptoglobin Therapeutics and Compartmentalization of Cell-Free Hemoglobin Toxicity

Buehler, Paul W.; Humar, Rok; Schaer, Dominik J.

doi:10.1016/j.molmed.2020.02.004

Cited by 71 publications

(64 citation statements)

References 147 publications

(184 reference statements)

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“…Macrophages also play a key role in physiological erythrocyte turnover by mediating phagocytic clearance of senescent and damaged red blood cells (RBC). This homeostatic function of macrophages becomes imperative in conditions with enhanced erythrolytic stress such as in patients with an acquired or genetic hemolytic anemia (4) .…”

Section: Introductionmentioning

confidence: 99%

Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes

Pfefferlé

Ingoglia

Schaer

et al. 2020

Journal of Clinical Investigation

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During hemolysis, macrophages in the liver phagocytose damaged erythrocytes to prevent the toxic effects of cell-free hemoglobin and heme. It remains unclear how this homeostatic process modulates phagocyte functions in inflammatory diseases. Using a genetic mouse model of spherocytosis and single-cell RNA sequencing, we found that erythrophagocytosis skewed liver macrophages into a unique anti-inflammatory phenotype that we defined as Marcohigh/Hmoxhigh/MHC-class IIlow erythrophagocytes. This phenotype transformation profoundly mitigated disease expression in a model of an anti-CD40-induced hyperinflammatory syndrome with necrotic hepatitis and in a non-alcoholic steatohepatitis model, representing two macrophage-driven sterile inflammatory diseases. We reproduced the anti-inflammatory erythrophagocyte transformation in vitro by heme-exposure of mouse and human macrophages, yielding a distinctive transcriptional signature that segregated heme-polarized from M1-and M2-polarized cells. Mapping transposase-accessible chromatin in single cells by sequencing (scATAC-seq) defined the transcription factor NFE2L2/NRF2 as a critical driver of erythrophagocytes, and Nfe2l2/Nrf2-deficiency restored heme-suppressed inflammation. Our findings point to a pathway that regulates macrophage functions to link erythrocyte homeostasis with innate immunity.

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Section: Introductionmentioning

confidence: 99%

Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes

Pfefferlé

Ingoglia

Schaer

et al. 2020

Journal of Clinical Investigation

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“…Hb carries four heme molecules, one in each of the four globin molecules that make up Hb. Each Hb molecule is composed of two αβ dimers (Perutz, 1989;Buehler et al, 2020). Heme B, the metalloporphyrin found in Hb, is made from protoporphyrin IX coordinated to a Fe(2+) cation (Figure 1).…”

Section: Heme and Hemoglobinmentioning

confidence: 99%

“…The clearance of the iron takes place via several mechanisms. First, blood products (methemoglobin, hemin, and iron cations) can be released by eryptosis and the uncontrolled cell death pathway, hemolysis (Foller et al, 2008;Dang et al, 2017;Buehler et al, 2020). Second, damaged red blood cells can be consumed by macrophages through erythrophagocytosis (Bulters et al, 2018).…”

Section: Release and Capture Of Iron In Intracerebral Hemorrhagementioning

confidence: 99%

“…Haptoglobin, a dimeric (trimeric, or tetrameric; depending on which exons are transcribed) polypeptide is expressed by hepatocytes to bind hemoglobin αβ subunit dimers in circulation. Adult humans have a wide range of circulating haptoglobin levels (0.3-1.9 mg/ml) which binds the hemoglobin subunit with effective irreversibility at a rate constant of 5.5 × 10 5 M −1 s −1 (Kristiansen et al, 2001;Buehler et al, 2009Buehler et al, , 2020. Haptoglobin has the additional function of reducing the reactivity of hemin to oxygen while in circulation (Mollan et al, 2014).…”

Section: Release and Capture Of Iron In Intracerebral Hemorrhagementioning

confidence: 99%

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The Chemical Basis of Intracerebral Hemorrhage and Cell Toxicity With Contributions From Eryptosis and Ferroptosis

Derry

Gnanansekaran

et al. 2020

Front. Cell. Neurosci.

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Intracerebral hemorrhage (ICH) is a particularly devastating event both because of the direct injury from space-occupying blood to the sequelae of the brain exposed to free blood components from which it is normally protected. Not surprisingly, the usual metabolic and energy pathways are overwhelmed in this situation. In this review article, we detail the complexity of red blood cell degradation, the contribution of eryptosis leading to hemoglobin breakdown into its constituents, the participants in that process, and the points at which injury can be propagated such as elaboration of toxic radicals through the metabolism of the breakdown products. Two prominent products of this breakdown sequence, hemin, and iron, induce a variety of pathologies including free radical damage and DNA breakage, which appear to include events independent from typical oxidative DNA injury. As a result of this confluence of damaging elements, multiple pathways of injury, cell death, and survival are likely engaged including ferroptosis (which may be the same as oxytosis but viewed from a different perspective) and senescence, suggesting that targeting any single cause will likely not be a sufficient strategy to maximally improve outcome. Combination therapies in addition to safe methods to reduce blood burden should be pursued.

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“…3,5 Further information on the structure and function of Hp and Hpr can be found in various review articles. 5,6,8,14,[25][26][27][28] Given its function as a Hb scavenger, Hp can be used as a therapeutic during conditions characterized by states of hemolysis (e.g., hemolytic anemia, massive blood transfusion, etc.). In these states, red blood cell (RBC) rupture releases cell-free Hb that can scavenge NO, leading to vasoconstriction as well as formation of free radicals and reactive oxygen species that can lead to oxidative damage of surrounding tissues.…”

Section: Introductionmentioning

confidence: 99%

Tangential flow filtration of haptoglobin

Pires

Palmer

2020

Biotechnology Progress

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Haptoglobin (Hp) is a plasma glycoprotein that scavenges cell-free hemoglobin (Hb). Hp has various potential therapeutic applications, but it has been mainly studied for treatment of acute hemolytic conditions that can arise from situations such as massive blood transfusion, infusion of stored red blood cells, severe burns, trauma, sepsis, radiation injury, and others. Therefore, Hp may also be beneficial during chronic hemolytic disease states such as hereditary spherocytosis, nocturnal hemoglobinuria, sickle-cell anemia, and malaria. Various methods have been developed to purify Hp from plasma or plasma fractions. However, none of these methods have exploited the large molecular weight (MW) range distribution of Hp polymers to easily isolate Hp from other plasma proteins. The present study used tangential flow filtration (TFF) to isolate polymeric Hp from plasma proteins using human Fraction IV (FIV) as the starting material. After removal of insoluble material from a suspension of FIV paste, the protein mixture was clarified on a 0.2 μm hollow fiber (HF) TFF filter. The clarified protein solution was then bracketed based on protein MW using HF filters with MW cutoffs (MWCOs) of 750, 500, and 100 kDa. Using untreated FIV, the Hp purity of the main bracket was~75% with a total Hb binding capacity (HbBC) yield of 1.2 g starting from 500 g of FIV paste. However, pretreatment of FIV with fumed silica to remove lipoproteins increased Hp purity to >95% with a HbBC yield of 1.7 g per 500 g of FIV. Taken together this study provides a novel and scalable method to purify Hp from plasma or plasma fractions.

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Haptoglobin Therapeutics and Compartmentalization of Cell-Free Hemoglobin Toxicity

Cited by 71 publications

References 147 publications

Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes

Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes

The Chemical Basis of Intracerebral Hemorrhage and Cell Toxicity With Contributions From Eryptosis and Ferroptosis

Tangential flow filtration of haptoglobin

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