Haptoglobin therapy for acute favism: a Japanese boy with glucose-6-phosphate dehydrogenase Guadalajara

Haptoglobin: From hemoglobin scavenging to human health

Haptoglobin (Hp) belongs to the family of acute-phase plasma proteins and represents the most important plasma detoxifier of hemoglobin (Hb). The basic Hp molecule is a tetrameric protein built by two α/β dimers. Each Hp α/β dimer is encoded by a single gene and is synthesized as a single polypeptide. Following post-translational protease-dependent cleavage of the Hp polypeptide, the α and β chains are linked by disulfide bridge(s) to generate the mature Hp protein. As human Hp gene is characterized by two common Hp1 and Hp2 alleles, three major genotypes can result (i.e., Hp1-1, Hp2-1, and Hp2-2). Hp regulates Hb clearance from circulation by the macrophage-specific receptor CD163, thus preventing Hb-mediated severe consequences for health. Indeed, the antioxidant and Hb binding properties of Hp as well as its ability to stimulate cells of the monocyte/macrophage lineage and to modulate the helper T-cell type 1 and type 2 balance significantly associate with a variety of pathogenic disorders (e.g., infectious diseases, diabetes, cardiovascular diseases, and cancer). Alternative functions of the variants Hp1 and Hp2 have been reported, particularly in the susceptibility and protection against infectious (e.g., pulmonary tuberculosis, HIV, and malaria) and non-infectious (e.g., diabetes, cardiovascular diseases and obesity) diseases. Both high and low levels of Hp are indicative of clinical conditions: Hp plasma levels increase during infections, inflammation, and various malignant diseases, and decrease during malnutrition, hemolysis, hepatic disease, allergic reactions, and seizure disorders. Of note, the Hp:Hb complexes display heme-based reactivity; in fact, they bind several ferrous and ferric ligands, including O₂, CO, and NO, and display (pseudo-)enzymatic properties (e.g., NO and peroxynitrite detoxification). Here, genetic, biochemical, biomedical, and biotechnological aspects of Hp are reviewed.

The role of haptoglobin and hemopexin in the prevention of delayed cerebral ischaemia after aneurysmal subarachnoid haemorrhage: a review of current literature

Delayed cerebral ischaemia (DCI) after aneurysmal subarachnoid haemorrhage (aSAH) is a major cause of mortality and morbidity. The pathophysiology of DCI after aSAH is thought to involve toxic mediators released from lysis of red blood cells within the subarachnoid space, including free haemoglobin and haem. Haptoglobin and hemopexin are endogenously produced acute phase proteins that are involved in the clearance of these toxic mediators. The aim of this review is to investigate the pathophysiological mechanisms involved in DCI and the role of both endogenous as well as exogenously administered haptoglobin and hemopexin in the prevention of DCI.

New Therapeutic Options for the Treatment of Sickle Cell Disease

Sickle cell disease (SCD; ORPHA232; OMIM # 603903) is a chronic and invalidating disorder distributed worldwide, with high morbidity and mortality. Given the disease complexity and the multiplicity of pathophysiological targets, development of new therapeutic options is critical, despite the positive effects of hydroxyurea (HU), for many years the only approved drug for SCD. New therapeutic strategies might be divided into (1) pathophysiology-related novel therapies and (2) innovations in curative therapeutic options such as hematopoietic stem cell transplantation and gene therapy. The pathophysiology related novel therapies are: a) Agents which reduce sickling or prevent sickle red cell dehydration; b) Agents targeting SCD vasculopathy and sickle cell-endothelial adhesive events; c) Anti-oxidant agents. This review highlights new therapeutic strategies in SCD and discusses future developments, research implications, and possible innovative clinical trials.

Haptoglobin and Free Haemoglobin during Cardiac Surgery—is there a Link to Acute Kidney Injury?

Acute kidney injury (AKI) is frequently observed after cardiac surgery (CS) with cardiopulmonary bypass (CPB). Multiple mechanisms underlie this phenomenon, including CPB-dependent haemolysis. Haemoglobin is released during haemolysis, and free haemoglobin (frHb) causes tubular cell injury after exceeding the binding capacity of haptoglobin (Hp). The objective of this study was to investigate the influence of perioperative changes in frHb and Hp levels on the incidence of CS-associated (CSA) AKI. After receiving local ethics committee approval and obtaining informed consent from our patients, we analysed the data pertaining to 154 patients undergoing CPB surgery. We recorded frHb and Hp concentrations pre-, intra- and postoperatively and defined AKI using the Kidney Disease Improving Global Outcomes (KDIGO) classification. We observed that frHb levels increased significantly during surgery and then decreased at ten hours thereafter and that Hp levels decreased during surgery and remained at low levels until the first postoperative day. We noted a moderate negative correlation between frHb and Hp levels. AKI was identified in 45.5% of patients; however, there was no significant difference in frHb or Hp levels between patients with and without AKI. We did not observe a relationship between frHb or Hp levels and CSA AKI and thus could not confirm the hypothesis that patients with higher baseline Hp concentrations experience a lower incidence of AKI than patients with lower baseline Hp concentrations.

New perspectives on the thrombotic complications of haemolysis

Many clinical settings are associated with haemolysis, from rare conditions, such as paroxysmal nocturnal haemoglobinuria, to common interventions, such as mechanical circulatory support and blood transfusion. The toxic effects of circulating free haemoglobin, haem, and iron are becoming increasingly understood and include an increased risk of thrombotic complications. This review summarizes the epidemiological evidence for an association between haemolysis and thrombosis and explores potential underlying mechanisms. New insights into the role haem plays in inflammatory signalling and in generating neutrophil extracellular traps (NETs) may provide useful strategies for managing pathological states associated with severe haemolysis. A better understanding of the toxic effects of haemolysis will result in better therapies to prevent the side effect of thrombosis.

Hemolysis and free hemoglobin revisited: exploring hemoglobin and hemin scavengers as a novel class of therapeutic proteins

Hemolysis occurs in many hematologic and nonhematologic diseases. Extracellular hemoglobin (Hb) has been found to trigger specific pathophysiologies that are associated with adverse clinical outcomes in patients with hemolysis, such as acute and chronic vascular disease, inflammation, thrombosis, and renal impairment. Among the molecular characteristics of extracellular Hb, translocation of the molecule into the extravascular space, oxidative and nitric oxide reactions, hemin release, and molecular signaling effects of hemin appear to be the most critical. Limited clinical experience with a plasma-derived haptoglobin (Hp) product in Japan and more recent preclinical animal studies suggest that the natural Hb and the hemin-scavenger proteins Hp and hemopexin have a strong potential to neutralize the adverse physiologic effects of Hb and hemin. This includes conditions that are as diverse as RBC transfusion, sickle cell disease, sepsis, and extracorporeal circulation. This perspective reviews the principal mechanisms of Hb and hemin toxicity in different disease states, updates how the natural scavengers efficiently control these toxic moieties, and explores critical issues in the development of human plasma-derived Hp and hemopexin as therapeutics for patients with excessive intravascular hemolysis.

Glucose-6-phosphate dehydrogenase variants associated with favism in Thai children

In a study conducted at Songklanagarind Hospital in the south of Thailand, the subjects were 225 patients (210 boys and 15 girls) with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Favism was found in 3.6% of the G6PD-deficient children. Approximately one half of the G6PD-deficient patients with favism were younger than 2 years. Sudden onset of anemia was found within 1 to 3 days after ingestion of dried fava beans. The classic features of favism, which are pallor, hemoglobinuria, and jaundice, were detected in all cases. To characterize the known G6PD mutations in Thai children, molecular analysis was performed for 8 G6PD-deficient children with favism by a combination of polymerase chain reaction-restriction fragment length polymorphism analysis and amplification refractory mutation system analysis. The G6PD variants in these children were G6PD Kaiping 1388,G-->A; G6PD Mahidol 487,G-->A; G6PD Viangchan 871,G-->A; and uncharacterized mutation with silent mutation 1311,C-->T.

Molecular heterogeneity of glucose-6-phosphate dehydrogenase deficiency in Mexico: overall results of a 7-year project

Several years ago, a project aiming to determine (i) the molecular basis of G-6-PD deficiency, (ii) the distribution of four different mutant alleles previously detected, and (iii) the whole of polymorphic alleles that account for the overall prevalence of G-6-PD deficiency in Mexico was implemented. Nearly 5000 individuals-from the general population and patients with hemolytic anemia-belonging to at least 14 States were screened for G-6-PD deficiency. Seventy-six G-6-PD-deficient subjects were detected and the prevalence of G-6-PD deficiency in 4777 individuals from the general population was 0.71%. Screening for both mutations associated with enzyme deficiency and silent polymorphisms at the G-6-PD gene was performed in the enzyme-deficient individuals by PCR-SSCP combined with restriction enzyme analysis; the silent polymorphisms as well as the nondeficient variant G-6-PD A(376G) were also investigated in 366 G-6-PD normal individuals from the general population. In 88% of the enzyme-deficient individuals it was possible to define the mutation responsible and the type G-6-PD A- variants were the more common in both individuals from the general population and patients with hemolytic anemia. G-6-PD deficiency is heterogeneous at the DNA level in Mexico and up to date 10 different variants-8 in the present project and 2 previously-have been observed: G-6-PD A(-202A/376G), G-6-PD A(-376G/968C), G-6-PD Santamaria(376G/542T), G-6-PD Vanua Lava(383C), G-6-PD Tsukui(del561-563), G-6-PD "Mexico City"(680A), G-6-PD Seattle(844C), G-6PD Guadalajara(1159T),G-6-PD Nashville(1178A), and G-6-PD Union(1360T). The G-6-PD A(-) variants have a relatively homogeneous distribution and along with G-6-PD Santamaria(376G/542T), they account for 82% of the overall prevalence of G-6-PD deficiency in Mexico; all other seven variants represent 9% of the mutant alleles examined, and in the rest of the chromosomes the mutation responsible for the enzyme deficiency remains to be defined. Several of the variants observed in Mexico are common in Africa, South Europe, and Southeast Asia. The prevalence for the variant G-6-PD A(376G) was 1.64%. From 256 possible haplotypes only 14 were observed and haplotype analysis suggests that some of the G-6-PD variants probably were imported to Mexico by population flow from South Europe, Africa, and Southeast Asia. This work (i) identified the G-6-PD variants prevalent in Mexico, (ii) defines their geographical distribution, (iii) contributes to the knowledge of the genetic structure of the Mexican population, and (iv) will facilitate the molecular analysis of the G-6-PD gene in enzyme-deficient Mexican individuals.

Chronic non-spherocytic haemolytic disorders associated with glucose-6-phosphate dehydrogenase variants

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect, being present in over 400 million people world wide. In a small number of cases, G6PD deficiency can lead to mild-to-severe chronic haemolysis, which is further exacerbated by oxidative stress. Such G6PD variants have been described all over the world and are responsible for chronic non-spherocytic haemolytic anaemia (CNSHA). To date 61 G6PD molecular variants associated with CNSHA have been identified, only some of which can cause the severe reduction in stability of the red blood cell enzyme. The distribution of the different mutations shows a predominance of small mutational events, and many have been found repeatedly in different parts of the world. By revisiting the 61 class I variants described so far, we can observe that a low inhibition constant (Ki) for NADPH, a higher Km for substrates and a reduced thermostability are common.

Clinical and haematological consequences of recurrent G6PD mutations and a single new mutation causing chronic nonspherocytic haemolytic anaemia

We have determined the causative mutation in 12 cases of glucose-6-phosphate dehydrogenase deficiency associated with chronic non-spherocytic haemolytic anaemia. In 11 of them the mutation we found had been previously reported in unrelated individuals. These mutations comprise seven different missense mutations and a 24 base pair deletion. G6PD Nara, previously found in a Japanese boy. Repeated findings of the same mutations suggests that a limited number of amino acid changes can produce the CNSHA phenotype and be compatible with normal development. The one new mutation we have found, G6PD Serres, is 1082 C-->T causing a 361 Ala-->Val substitution in the dimer interface where most other severe G6PD mutations are found. Now that several patients with the same mutation have been reported we can compare the resulting clinical phenotypes. For each mutation we find a reasonably consistent clinical picture, ranging from mild (G6PD Clinic) through moderate (G6PD Nashville) to severe (G6PD Beverly Hills and G6PD Nara).

Molecular genetics of glucose-6-phosphate dehydrogenase deficiency in Mexico

Several studies carried out between 1965 and 1985 showed that G-6-PD deficiency in Mexico is heterogeneous at the biochemical level and that the G-6-PD A- phenotype is relatively common. We have now investigated the molecular basis of G-6-PD deficiency in Mexico. Up-to-date 60 chromosomes with G6PD mutations have been studied, 16 in previous studies and 44 in the present work. Molecular analysis of DNA from G-6-PD deficient Mexican mestizos and their relatives show that G-6-PD A- genotypes are relatively common but also that in Mexico G-6-PD deficiency is heterogeneous at the DNA level. Thus, five different genotypes have been observed: G-6-PD A-(202A/376G) (41 chromosomes), G-6-PD A-(376G/968C) (14 chromosomes), G-6-PD Seattle844C (3 chromosomes), G-6-PD "Mexico City"680A (1 chromosome) and G-6-PD Guadalajara1159T (1 chromosome). The G-6-PD A-(202A/376G), G-6-PD A-(376G/968C) and G-6-PD Seattle844C mutations in Mexico are on the same Pvu II/ Pst I/ 1311 / Nla III haplotypes as found in individuals from Africa, Spain and the Canary Islands. Consequently, these mutations were probably imported to Mexico through African slaves and/or the Spanish immigrants during and after the colonization.