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The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease.

ABSTRACT: Hemolysis is a pathological feature of several diseases of diverse etiology such as hereditary anemias, malaria, and sepsis. A major complication of hemolysis involves the release of large quantities of hemoglobin into the blood circulation and the subsequent generation of harmful metabolites like labile heme. Protective mechanisms like haptoglobin-hemoglobin and hemopexin-heme binding, and heme oxygenase-1 enzymatic degradation of heme limit the toxicity of the hemolysis-related molecules. The capacity of these protective systems is exceeded in hemolytic diseases, resulting in high residual levels of hemolysis products in the circulation, which pose a great oxidative and proinflammatory risk. Sickle cell disease (SCD) features a prominent hemolytic anemia which impacts the phenotypic variability and disease severity. Not only is circulating heme a potent oxidative molecule, but it can act as an erythrocytic danger-associated molecular pattern (eDAMP) molecule which contributes to a proinflammatory state, promoting sickle complications such as vaso-occlusion and acute lung injury. Exposure to extracellular heme in SCD can also augment the expression of placental growth factor (PlGF) and interleukin-6 (IL-6), with important consequences to enthothelin-1 (ET-1) secretion and pulmonary hypertension, and potentially the development of renal and cardiac dysfunction. This review focuses on heme-induced mechanisms that are implicated in disease pathways, mainly in SCD. A special emphasis is given to heme-induced PlGF and IL-6 related mechanisms and their role in SCD disease progression.

SUBMITTER: Gbotosho OT

PROVIDER: S-EPMC7873693 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease.

Gbotosho Oluwabukola T OT Kapetanaki Maria G MG Kato Gregory J GJ

Frontiers in immunology 20210127

Hemolysis is a pathological feature of several diseases of diverse etiology such as hereditary anemias, malaria, and sepsis. A major complication of hemolysis involves the release of large quantities of hemoglobin into the blood circulation and the subsequent generation of harmful metabolites like labile heme. Protective mechanisms like haptoglobin-hemoglobin and hemopexin-heme binding, and heme oxygenase-1 enzymatic degradation of heme limit the toxicity of the hemolysis-related molecules. The ...[more]

PMID: 33584641

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Project description:Sickle Cell Disease (SCD) is a painful, lifelong hemoglobinopathy inherited as a missense point mutation in the hemoglobin (Hb) beta-globin gene. This disease has significant impact on quality of life and mortality, thus a substantial medical need exists to reduce the vaso-occlusive crises which underlie the pathophysiology of the disease. The concept that a gaseous molecule may exert biological function has been well known for over one hundred years. Carbon monoxide (CO), although studied in SCD for over 50 years, has recently emerged as a powerful cytoprotective biological response modifier capable of regulating a host of physiologic and therapeutic processes that, at low concentrations, exerts key physiological functions in various models of tissue inflammation and injury. CO is physiologically generated by the metabolism of heme by the heme oxygenase enzymes and is measurable in blood. A substantial amount of preclinical and clinical data with CO have been generated, which provide compelling support for CO as a potential therapeutic in a number of pathological conditions. Data underlying the therapeutic mechanisms of CO, including in SCD, have been generated by a plethora of in vitro and preclinical studies including multiple SCD mouse models. These data show CO to have key signaling impacts on a host of metallo-enzymes as well as key modulating genes that in sum, result in significant anti-inflammatory, anti-oxidant and anti-apoptotic effects as well as vasodilation and anti-adhesion of cells to the endothelium resulting in preservation of vascular flow. CO may also have a role as an anti-polymerization HbS agent. In addition, considerable scientific data in the non-SCD literature provide evidence for a beneficial impact of CO on cerebrovascular complications, suggesting that in SCD, CO could potentially limit these highly problematic neurologic outcomes. Research is needed and hopefully forthcoming, to carefully elucidate the safety and benefits of this potential therapy across the age spectrum of patients impacted by the host of pathophysiological complications of this devastating disease.

Project description:ImportanceIndividuals with sickle cell disease (SCD) have reduced life expectancy; however, there are limited data available on lifetime income in patients with SCD.ObjectiveTo estimate life expectancy, quality-adjusted life expectancy, and income differences between a US cohort of patients with SCD and an age-, sex-, and race/ethnicity-matched cohort without SCD.Design, setting, and participantsCohort simulation modeling was used to (1) build a prevalent SCD cohort and a matched non-SCD cohort, (2) identify utility weights for quality-adjusted life expectancy, (3) calculate average expected annual personal income, and (4) model life expectancy, quality-adjusted life expectancy, and lifetime incomes for SCD and matched non-SCD cohorts. Data sources included the Centers for Disease Control and Prevention, National Newborn Screening Information System, and published literature. The target population was individuals with SCD, the time horizon was lifetime, and the perspective was societal. Model data were collected from November 29, 2017, to March 21, 2018, and the analysis was performed from April 28 to December 3, 2018.Main outcomes and measuresLife expectancy, quality-adjusted life expectancy, and projected lifetime income.ResultsThe estimated prevalent population for the SCD cohort was 87 328 (95% uncertainty interval, 79 344-101 398); 998 were male and 952 were female. Projected life expectancy for the SCD cohort was 54 years vs 76 years for the matched non-SCD cohort; quality-adjusted life expectancy was 33 years vs 67 years, respectively. Projected lifetime income was $1 227 000 for an individual with SCD and $1 922 000 for a matched individual without SCD, reflecting a lost income of $695 000 owing to the 22-year difference in life expectancy. One study limitation is that the higher estimates of life expectancy yielded conservative estimates of lost life-years and income. The analysis only considered the value of lost personal income owing to premature mortality and did not consider direct medical costs or other societal costs associated with excess morbidity (eg, lost workdays for disability, time spent in the hospital). The model was most sensitive to changes in income levels and mortality rates.Conclusions and relevanceIn this simulated cohort modeling study, SCD had societal consequences beyond medical costs in terms of reduced life expectancy, quality-adjusted life expectancy, and lifetime earnings. These results underscore the need for disease-modifying therapies to improve the underlying morbidity and mortality associated with SCD.

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The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease.

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The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease.

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