Neonatal jaundice and severity of glucose-6-phosphate dehydrogenase deficiency in Sardinian babies

Sirtuin 2 inhibition modulates chromatin landscapes genome-wide to induce senescence in ATRX-deficient malignant glioma

BACKGROUND

Functional inactivation of ATRX characterizes large subgroups of malignant gliomas in adults and children. ATRX deficiency in glioma induces widespread chromatin remodeling, driving transcriptional shifts and oncogenic phenotypes. Effective strategies to therapeutically target these broad epigenomic sequelae remain undeveloped.

METHODS

We utilized integrated multiomics and the Broad Institute Connectivity Map (CMAP) to identify drug candidates that could potentially revert ATRX-deficient transcriptional changes. We then employed disease-relevant experimental models to evaluate functional phenotypes, coupling these studies with epigenomic profiling to elucidate molecular mechanism(s).

RESULTS

CMAP analysis and transcriptional/epigenomic profiling implicated the Class III HDAC Sirtuin2 (SIRT2) as a central mediator of ATRX-deficient cellular phenotypes and a driver of unfavorable prognosis in ATRX-deficient glioma. SIRT2 inhibitors reverted Atrx-deficient transcriptional signatures in murine neuroepithelial progenitor cells (mNPCs), impaired cell migration in Atrx/ATRX-deficient mNPCs and human glioma stem cells (GSCs), and increased expression of senescence markers in glioma models. Moreover, SIRT2 inhibition impaired growth and increased senescence in ATRX-deficient GSCs in vivo. These effects were accompanied by genome-wide shifts in enhancer-associated H3K27ac and H4K16ac marks, with the latter in particular demonstrating compelling transcriptional links to SIRT2-dependent phenotypic reversals. Motif analysis of these data identified the transcription factor KLF16 as a mediator of phenotype reversal in Atrx-deficient cells upon SIRT2 inhibition.

CONCLUSIONS

Our findings indicate that SIRT2 inhibition selectively targets ATRX-deficient gliomas for senescence through global chromatin remodeling, while demonstrating more broadly a viable approach to combat complex epigenetic rewiring in cancer.

Sirtuin 2 inhibition modulates chromatin landscapes genome-wide to induce senescence in ATRX-deficient malignant glioma

Inactivating mutations in ATRX characterize large subgroups of malignant gliomas in adults and children. ATRX deficiency in glioma induces widespread chromatin remodeling, driving transcriptional shifts and oncogenic phenotypes. Effective strategies to therapeutically target these broad epigenomic sequelae remain undeveloped. We utilized integrated mulit-omics and the Broad Institute Connectivity Map (CMAP) to identify drug candidates that could potentially revert ATRX-deficient transcriptional changes. We then employed disease-relevant experimental models to evaluate functional phenotypes, coupling these studies with epigenomic profiling to elucidate molecular mechanim(s). CMAP analysis and transcriptional/epigenomic profiling implicated the Class III HDAC Sirtuin2 (Sirt2) as a central mediator of ATRX-deficient cellular phenotypes and a driver of unfavorable prognosis in ATRX-deficient glioma. Sirt2 inhibitors reverted Atrx-deficient transcriptional signatures in murine neuroprogenitor cells (mNPCs) and impaired cell migration in Atrx/ATRX-deficient mNPCs and human glioma stem cells (GSCs). While effects on cellular proliferation in these contexts were more modest, markers of senescence significantly increased, suggesting that Sirt2 inhibition promotes terminal differentiation in ATRX-deficient glioma. These phenotypic effects were accompanied by genome-wide shifts in enhancer-associated H3K27ac and H4K16ac marks, with the latter in particular demonstrating compelling transcriptional links to Sirt2-dependent phenotypic reversals. Motif analysis of these data identified the transcription factor KLF16 as a mediator of phenotype reversal in Atrx-deficient cells upon Sirt2 inhibition. Finally, Sirt2 inhibition impaired growth and increased senescence in ATRX-deficient GSCs in vivo . Our findings indicate that Sirt2 inhibition selectively targets ATRX-deficient gliomas through global chromatin remodeling, while demonstrating more broadly a viable approach to combat complex epigenetic rewiring in cancer.

One Sentence Summary

Our study demonstrates that SIRT2 inhibition promotes senescence in ATRX-deficient glioma model systems through global epigenomic remodeling, impacting key downstream transcriptional profiles.

G6PD Deficiency and Breast Cancer

A study of the relative 2dG6P utilization in mononuclear cells from a group of 150 women with breast cancer was undertaken to evaluate a possible negative correlation between G6PD deficiency and cancer, as suggested by some authors. Twenty-one women (14.00 %) were heterozygotes and 2 were homozygotes (1.33 %). The prevalence found was not different from that expected. It would therefore seem that the G6PD Mediterranean allele does not play a protective role against the development of breast cancer.

Markers of oxidative stress in umbilical cord blood from G6PD deficient African newborns

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked disorder that affects as many as 400 million people worldwide, making it the most common enzymatic defect. Subjects with G6PD deficiency are more likely to develop neonatal hyperbilirubinemia potentially leading to kernicterus and are at increased risk for acute hemolytic anemia when exposed to pro-oxidant compounds such as anti-malarial drugs. We collected umbilical cord blood from 300 males born in Uganda to assess for novel markers of systemic oxidative stress. We determined that 10.7% of the samples collected were G6PD A- deficient (G202A/A376G) and when these were compared with unaffected controls, there was significantly higher 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentration, elevated ferritin, increased leukocyte count and higher small molecule antioxidant capacity. These data suggest increased baseline oxidative stress and an elevated antioxidant response in umbilical cord blood of patients with G6PD deficiency.

The Preterm Infant: A High-Risk Situation for Neonatal Hyperbilirubinemia Due to Glucose-6-Phosphate Dehydrogenase Deficiency

Prematurity and glucose-6-phosphate dehydrogenase (G6PD) deficiency are risk factors for neonatal hyperbilirubinemia. The 2 conditions may interact additively or synergistically, contributing to extreme hyperbilirubinemia, with the potential for bilirubin neurotoxicity. This hyperbilirubinemia is the result of sudden, unpredictable, and acute episodes of hemolysis in combination with immaturity of bilirubin elimination, primarily of conjugation. Avoidance of contact with known triggers of hemolysis in G6PD-deficient individuals will prevent some, but not all, episodes of hemolysis. All preterm infants with G6PD deficiency should be vigilantly observed for the development of jaundice both in hospital and after discharge home.

Hyperbilirubinemia, hemolysis, and increased bilirubin neurotoxicity

Increased hemolysis in the presence of severe neonatal hyperbilirubinemia appears to augment the risk of bilirubin neurotoxicity. The mechanism of this intensifying effect is uncertain. In direct antiglobulin titer (DAT) positive, isoimmune hemolytic disease, the bilirubin threshold at which neurotoxicity occurs appears to be lower than in DAT-negative hyperbilirubinemia. In other hemolytic conditions, the hemolysis may simply facilitate the development of extremely high serum bilirubin levels. Whether the hemolytic process per se exerts an independent effect or whether a very rapid rise in serum bilirubin might lead to greater penetration of the blood-brain barrier is unclear. In this review, we survey the synergistic role of hemolysis associated with severe hyperbilirubinemia in the potentiation of bilirubin-induced neurotoxicity and suggest methods of identifying at-risk babies with increased hemolysis to allow for their increased surveillance.

Is it accurate to separate glucose-6-phosphate dehydrogenase activity in neonatal hyperbilirubinemia as deficient and normal?

BACKGROUND

The aim of this study was to investigate glucose 6-phosphate dehydrogenase (G6PD) activity in term and late preterm babies with severe neonatal hyperbilirubinemia and its relationship to the severity and treatment of this disorder, regardless of level of G6PD activity (deficient/normal).

METHODS

A total of 529 term and late preterm (≥35 weeks) infants (228 female, 301 male) who were diagnosed with severe hyperbilirubinemia were included in this study. In each case, serum was collected to evaluate blood group, direct Coombs' test, complete blood cell count, total and direct bilirubin, thyroid-stimulating hormone, and G6PD activity. A partial correlation analysis was carried out to assess the relationship between G6PD activity and total bilirubin levels.

RESULTS

A significant correlation was found between the severity of hyperbilirubinemia and G6PD activity in both males and females. Male neonates who had G6PD levels <12 U/g Hb required more phototherapy time than neonates who had G6PD levels ≥12 U/g Hb; and female neonates who had G6PD levels <16 U/g Hb required more phototherapy time than neonates who had G6PD levels ≥16 U/g Hb (p < 0.0001). When we analyzed only breastfed infants, a significant difference also emerged in both sexes. Decreased G6PD activity was associated with increased phototherapy time and the need for exchange transfusion.

CONCLUSION

Routine checks of G6PD level in hyperbilirubinemic neonates are very important in providing proper medical management to prevent bilirubin-induced neurological dysfunction. Appropriate identification of G6PD (<12 U/g Hb for male infants and <16 U/g Hb for female infants) raises awareness of the severity of the condition and the necessity for immediate care of severe hyperbilirubinemic infants.

Severe hemolysis with normal blood count in a glucose-6-phosphate dehydrogenase deficient neonate

A premature glucose-6-phosphate dehydrogenase (G-6-PD) deficient neonate was readmitted for exponential rise in the plasma bilirubin concentration to 33.0 mg dl(-1). Blood carboxyhemoglobin (2.8% of total hemoglobin, >threefold normal value) confirmed the presence of hemolysis; however, hematological indices were unchanged from the birth hospitalization. Serum unbound bilirubin, although present, was probably at a concentration insufficient to cause bilirubin encephalopathy. In G-6-PD deficient neonates, severe hemolysis may occur in the absence of hematological changes typical of a hemolytic process.

Glucose-6-phosphate dehydrogenase deficiency: a hidden risk for kernicterus

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, a commonly occurring enzymatic defect, is an important risk factor in the pathogenesis of severe neonatal hyperbilirubinemia. Many of the recently reported cases of kernicterus, even in countries with a low overall incidence of the G-6-PD deficiency such as the United States and Canada, have been found to be enzyme deficient. In many cases the hyperbilirubinemia may be due to acute hemolysis precipitated by exposure to an identifiable chemical trigger, or to infection. In other cases the hemolysis may be mild, the hyperbilirubinemia being due to diminished bilirubin conjugation. An interaction between G-6-PD deficiency and promoter polymorphism for the gene encoding the bilirubin conjugating enzyme, UDP-glucuronosyltranferase 1A1, associated with Gilbert syndrome, has been implicated in the pathogenesis of hyperbilirubinemia. Neonates whose families originated in areas at high risk for G-6-PD deficiency should be vigilantly observed for jaundice. Phototherapy is the mainstay of treatment, with exchange transfusion being performed in those unresponsive to phototherapy. A high degree of physician awareness is essential in the identification and follow-up of these high-risk neonates.

Hyperbilirubinemia among African American, glucose-6-phosphate dehydrogenase-deficient neonates

BACKGROUND

Although glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is prevalent in African Americans, their risk of associated neonatal hyperbilirubinemia has not been prospectively studied.

OBJECTIVE

To compare hemolysis and the risk of hyperbilirubinemia among African American, G-6-PD-deficient neonates (study group) and G-6-PD-normal control subjects.

METHODS

Consecutive, healthy, term and near-term, male neonates born to African American mothers comprised the patient cohort. G-6-PD testing was performed with umbilical cord blood samples. Routine management included measurement of the end tidal carbon monoxide level corrected for ambient carbon monoxide level (ETCOc) within 4 hours after delivery (assessment of hemolysis), > or =1 predischarge bilirubin determination, and additional bilirubin testing as clinically indicated. Indications for phototherapy were identical for study patients and control subjects. Neonates were monitored for the first 1 week of life. ETCOc results, the incidence of hyperbilirubinemia (defined as a transcutaneous or plasma total bilirubin concentration of > or =95th percentile for the hour of life), and the need for phototherapy were compared between the G-6-PD-deficient and G-6-PD-normal groups.

RESULTS

Five hundred male patients were enrolled, of whom 64 (12.8%) were G-6-PD-deficient. ETCOc values (median and interquartile range) were higher among G-6-PD-deficient neonates than among control neonates (2.4 ppm [2.0-2.9 ppm] vs 2.1 ppm [1.7-2.5 ppm]). More G-6-PD-deficient neonates developed hyperbilirubinemia than did control subjects (14 of 64, 21.9%, vs 29 of 436, 6.7%; relative risk: 3.27; 95% confidence interval: 1.83-5.86), whereas 13 (20.3%) met the criteria for phototherapy, compared with 25 control subjects (5.7%) (relative risk: 3.53; 95% confidence interval: 1.91-6.56). No cases of kernicterus were observed.

CONCLUSIONS

Within the African American neonatal population, there is a subgroup of G-6-PD-deficient infants with elevated rates of hemolysis, a higher incidence of hyperbilirubinemia, and a greater requirement for phototherapy, compared with G-6-PD-normal control subjects. These newborns should be monitored vigilantly for the development of hyperbilirubinemia.

Glucose-6-phosphate dehydrogenase deficiency: a potential source of severe neonatal hyperbilirubinaemia and kernicterus

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is a commonly occurring enzyme defect that can lead to severe neonatal hyperbilirubinaemia and kernicterus. Both increased haemolysis, sometimes due to an identifiable chemical trigger or to infection, and diminished bilirubin conjugation, the result of an interaction between G-6-PD deficiency and Gilbert's syndrome, contribute to the pathogenesis of the jaundice. Phototherapy is the mainstay of treatment, with exchange transfusion held in reserve for those neonates who do not respond to phototherapy. Pharmacological agents such as Sn-mesoporphyrins, which prevent bilirubin production by inhibiting the enzyme heme oxygenase, can limit hyperbilirubinaemia and possibly prevent the need for exchange transfusion. Predischarge serum total bilirubin screening is useful in predicting which neonates are at high risk for developing hyperbilirubinaemia. Migration patterns make G-6-PD deficiency a condition which may nowadays be encountered in virtually any corner of the globe and a high degree of physician awareness is essential.

Alternations in quantities and activities of erythrocyte cytosolic carbonic anhydrase isoenzymes in glucose-6-phosphate dehydrogenase-deficient individuals

BACKGROUND

This study was designed to evaluate the quantitative and activity alterations of cytosolic carbonic anhydrase (CA) isoenzymes in the erythrocytes of glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals.

METHODS

Western Blot and CA esterase activity analysis were employed to measure cytosolic erythrocyte CA isoenzymes.

RESULTS

The total CA activities were analyzed from erythrocytes of 30 healthy and 30 G6PD-deficient individuals. The mean values with standard error (SE) were 22.9+/-1.69 U/gHb and 27.2+/-2.1 U/gHb (P<0.01), respectively. The ratio of CAI/CAII of G6PD-deficient individuals (1.28+/-0.06) was significantly lower than that of the normal subjects (3.79+/-0.18) (P<0.001). Furthermore, the concentration of CAIII in G6PD-deficient individuals was significantly lower than that of the normal subjects (P<0.001) and there were significant correlations between the concentration of CAI, CAII, CAIII, and ratio of CAI/CAII, and the activity concentration of G6PD.

CONCLUSIONS

Different carbonic anhydrase isoenzymes may serve different roles in the G6PD-deficient erythrocyte. CAI could be used as an indicator for hemolytic anemia. CAII is able to compensate for the functions of CAI and increased expression of CAII will promote oxidative damage. CAIII can provide the G6PD-deficient persons with some extent of protection against oxidative damage.

Genetic interactions in the pathogenesis of neonatal hyperbilirubinemia: Gilbert's Syndrome and glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is a common condition with a worldwide distribution that has the potential for causing severe hyperbilirubinemia with bilirubin encephalopathy. Hemolysis resulting from identifiable triggers may be the cause of the jaundice in some cases, but in many, jaundice continues to occur despite avoidance of contact with known hemolytic triggers. In some G-6-PD-deficient population groups, carboxyhemoglobin studies have indicated exaggerated hemolysis; but in others, increased hemolysis has not correlated with serum total bilirubin values. As hyperbilirubinemia results from an imbalance between bilirubin production and bilirubin elimination, diminished bilirubin conjugation was suspected to contribute to the pathogenesis of hyperbilirubinemia. Serum-conjugated bilirubin fractions, reflecting intrahepatocytic bilirubin conjugation, were low in G-6-PD-deficient neonates who developed hyperbilirubinemia. This conjugated bilirubin profile was similar to that seen in adults with Gilbert's Syndrome, a condition associated with promoter polymorphism for the gene encoding the bilirubin-conjugating enzyme, UGT glucuronosyltransferase 1A1 (UGT). Whereas G-6-PD deficiency or Gilbert's Syndrome, alone, did not predispose to hyperbilirubinemia, G-6-PD-deficient neonates who also were heterozygotes or homozygotes for the variant UGT gene promoter did have significantly increased incidences of hyperbilirubinemia. Additional conditions which predispose to neonatal jaundice in the presence of Gilbert's Syndrome, include Coombs' negative ABO blood group heterospecificity, hereditary spherocytosis, and prolonged breastfeeding.Gilbert's Syndrome and G-6-PD deficiency are both common, inherited conditions. Individually, and in the absence of additional genetic or environmental factors, both are benign, and should result in minimal health disturbance or interference with the quality of life of affected individuals. However, in combination, or following exposure to environmental or other genetic factors, these benign conditions may have severe manifestations, with potentially dangerous and possibly life-threatening consequences. This review highlights the major clinical features of both Gilbert's Syndrome and G-6-PD deficiency, and surveys a series of studies related to neonatal jaundice in G-6-PD-deficient neonates culminating in the documentation of an interaction between the two conditions that is crucial to the pathogenesis of hyperbilirubinemia.

Acute hemolysis and severe neonatal hyperbilirubinemia in glucose-6-phosphate dehydrogenase-deficient heterozygotes

Two premature female infants had severe hyperbilirubinemia caused by hemolysis. Both neonates were heterozygotes for the glucose-6-phosphate dehydrogenase Mediterranean mutation as determined by DNA analysis. Glucose-6-phosphate dehydrogenase-deficient heterozygotes may be susceptible to the complications of this enzyme deficiency.

Glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) is expressed in all tissues, where it catalyses the first step in the pentose phosphate pathway. G6PD deficiency is prevalent throughout tropical and subtropical regions of the world because of the protection it affords during malaria infection. Although most affected individuals are asymptomatic, there is a risk of neonatal jaundice and acute haemolytic anaemia, triggered by infection and the ingestion of certain drugs and broad beans (favism). A rare but more severe form of G6PD deficiency is found throughout the world and is associated with chronic non-spherocytic haemolytic anaemia. Many deficient variants of G6PD have been described. DNA sequence analysis has shown that the vast majority of these are caused by single amino acid substitutions. The three-dimensional structure of G6PD shows a classical dinucleotide binding domain and a novel beta + alpha domain involved in dimerization.

Bilirubin levels in the acute hemolytic crisis of G6PD deficiency are related to Gilbert's syndrome

In this study we analyzed the effect of the (TA)7 polymorphism of the UGT1A gene associated with Gilbert's syndrome in G6PD-deficient subjects during an acute hemolytic crisis (fabic crisis). DNA from 44 subjects originating from the same geographic area in Sardinia was analyzed for the UGT1A promoter polymorphism. The increase of unconjugated bilirubin level during fabic crisis and its relationship with UGT1A polymorphism was evaluated. The UGT1A (TA)7 TATA box variant was found in 9/44 (21%) of the G6PD deficient subjects examined. The median value for unit of increase of bilirubin (mg/dl)/unit of decrease of hemoglobin (g/dl) was higher in variant homozygous than in heterozygous and normal subjects. These findings imply a contribution of the UGT1A polymorphism associated to Gilbert's syndrome to development of the hyperbilirubinemia in G6PD deficient subjects during acute hemolytic anemia.

Three major G6PD-deficient polymorphic variants identified among the Mauritian population

We report the results of the first epidemiological study investigating glucose 6-phosphate dehydrogenase (G6PD) deficiency among the heterogenous Mauritian population. Mauritius has a population of approximately 1 million, and of these 66.8% are Indo-Mauritian (of Indian origin), 27.9% are Creoles (of African ancestry) and 2.1% are Sino-Mauritian, predominantly of Chinese origin. Of the 1435 Mauritian males tested, 73 (5.1%) were G6PD deficient. However, the prevalence varied considerably between the two major ethnic groups: 35/1157 (3.0%) for Indo-Mauritians and 37/267 (13.9%) for Creoles. Molecular analysis revealed three major deficient polymorphic variants; G6PD Orissa, G6PD Mediterranean and G6PD A-. G6PD Orissa (nt 131 G-->C; residue 44 Ala-->Gly) was found to be the most common variant among Indo-Mauritians: this deficient variant was recently identified to be highly characteristic of the tribal groups in central India. In Creoles the most common deficient variant was G6PD A- (27/37). These data are consistent with the different ancestral contributions to the present gene pool of the Mauritian population. This study has provided further information as to the precise nature of G6PD deficiency at the molecular level among Indians, about whom previously there was scant information. The data presented suggest that G6PD Orissa is widespread in central and southern states of India. Additionally, the identification and frequency of G6PD-deficient alleles in Mauritius is of public-health importance.

Severe neonatal jaundice associated with glucose-6-phosphate dehydrogenase deficiency: pathogenesis and global epidemiology

The association of glucose-6-phosphate dehydrogenase deficiency (G6PD def) with severe neonatal jaundice (NJ) and Kernicterus was described just over 30 years ago in reports from Sardinia (1-4) Singapore (5,6) and Greece (7,8). In this review we will examine the progress made since that time in our understanding of the pathophysiology of severe NJ associated with G6PD def, its global epidemiology, and its role in the balanced polymorphism of the G6PD def gene (Gd). Including this review in the Festschrift to Spyros Doxiadis should highlight his contribution to the field. In Greece the search for a new cause of severe NJ and Kernicterus was triggered by his realization that the recognized at the time, causes of severe NJ were absent in a large proportion of the neonates treated at the "Alexandra" Maternity Hospital in Athens (9).

'Idiopathic' jaundice in Sardinian full-term newborn infants: a multivariate study

'Idiopathic' hyperbilirubinaemia in the first 4 days of life was studied in 431 unselected healthy full-term (gestational age > or = 37 weeks) singleton Sardinian infants with birthweight > or = 2500 g. All infants were free from malformations or any disease requiring treatment other than jaundice, they were ABO and Rh compatible with their mothers and were not G6PD deficient. The serum bilirubin level was > 11.9 mg/dl (204 mumol/l) and > 14.9 mg/dl (256 mumol/l) in 37.1% and 15.3% of the study subjects. The vast majority of the infants (94%) were breast fed; no difference in the incidence of jaundice was found between breast-fed and bottle-fed infants. A logistic regression analysis indicated that high alpha-fetoprotein concentrations in cord blood, history of neonatal jaundice in previous full-term siblings, delayed first meconium passage and weight loss were associated with jaundice, defined as a serum bilirubin level > 11.9 mg/dl. These results suggest that the high rate of neonatal hyperbilirubinaemia in Sardinia is mostly related to constitutional and possibly hereditary factors.