A single dose of Sn-mesoporphyrin prevents development of severe hyperbilirubinemia in glucose-6-phosphate dehydrogenase-deficient newborns

Single-cell profiling of ineffective erythropoiesis in a mouse model of β-thalassaemia intermedia

Beta-thalassaemia is an inherited haemoglobin disorder characterised by ineffective erythropoiesis (IE). The detailed pathogenesis of IE remains unclear. In this study, we used single-cell RNA sequencing (scRNA-seq) to examine IE in Th3/+ β-thalassaemic mice. The results showed that the erythroid group was remarkably expanded, and genes involved in biological processes such as iron metabolism, haeme synthesis, protein folding, and response to heat were significantly upregulated from erythroid progenitors to reticulocytes in β-thalassaemic mice. In particular, we identified a unique cell population close to reticulocytes, named ThReticulocytes, characterised by a high level of heat shock protein 70 (Hsp70) expression and dysregulation of iron metabolism and haeme synthesis signalling. Treatment of β-thalassaemic mice with the haeme oxygenase inhibitor tin-mesoporphyrin effectively improved the iron disorder and IE, and the ThReticulocyte population and Hsp70 expression were significantly suppressed. This study revealed in detail the progression of IE at the single-cell level and possibly provided clues to find therapeutic targets in thalassaemia.

Efficacy and Safety Concerns with Sn-Mesoporphyrin as an Adjunct Therapy in Neonatal Hyperbilirubinemia: A Literature Review

Neonatal hyperbilirubinemia is a frequently observed clinical situation that, sometimes, may result in complications ranging from mild neurodevelopment impairment to serious outcome of kernicterus. The rationale logic of heme oxygenase enzyme inhibition to lower bilirubin levels is intriguing. In compliance with that rationale, metalloporphyrin was discovered. After successful results in in-vitro and animal studies, tin mesoporphyrin is now under phase II clinical trial to test for preventive and therapeutic efficacy in unconjugated hyperbilirubinemia. This review evaluates in-vitro studies, animal studies, and clinical trials for the efficacy and safety of tin analogues of metalloporphyrin. Few alternatives to metalloporphyrins are also available, synchronizing with the same rationale logic of inhibition of bilirubin production, which need further research.

Stannsoporfin with phototherapy to treat hyperbilirubinemia in newborn hemolytic disease

OBJECTIVE

To evaluate the efficacy and safety of tin mesoporphyrin (SnMP) in neonates with hyperbilirubinemia (HB) due to hemolysis.

STUDY DESIGN

This multicenter, placebo-controlled phase 2b study (NCT01887327) randomized newborns (35-42 weeks) with hemolysis started on phototherapy (PT) to placebo (Ctrl), SnMP 3.0 mg/kg, or SnMP 4.5 mg/kg given once IM within 30 min of initiation of PT.

RESULTS

In all, 91 patients were randomized (Ctrl: n = 30; 3 mg/kg SnMP: n = 30; 4.5 mg/kg SnMP: n = 31). At 48 h TSB significantly increased in Ctrl by 17.5% (95% CI 5.6-30.7; p = 0.004) and significantly decreased by -13% (95% CI -21.7 to -3.2; p = 0.013) in the 3.0 mg/kg and by -10.5% (95% CI -19.4 to -0.6; p = 0.041) in the 4.5 mg/kg group. Decreases in SnMP groups were significant (p < 0.0001) vs Ctrl.

CONCLUSION

SnMP with PT significantly reduced TSB by 48 h. SnMP may be useful as a treatment for HB in neonates with hemolysis.

Long-Term Effects of Biliverdin Reductase a Deficiency in Ugt1-/- Mice: Impact on Redox Status and Metabolism

Accumulation of neurotoxic bilirubin due to a transient neonatal or persistent inherited deficiency of bilirubin glucuronidation activity can cause irreversible brain damage and death. Strategies to inhibit bilirubin production and prevent neurotoxicity in neonatal and adult settings seem promising. We evaluated the impact of Bvra deficiency in neonatal and aged mice, in a background of unconjugated hyperbilirubinemia, by abolishing bilirubin production. We also investigated the disposal of biliverdin during fetal development. In Ugt1^−/− mice, Bvra deficiency appeared sufficient to prevent lethality and to normalize bilirubin level in adults. Although biliverdin accumulated in Bvra-deficient fetuses, both Bvra^−/− and Bvra^−/−Ugt1^−/− pups were healthy and reached adulthood having normal liver, brain, and spleen histology, albeit with increased iron levels in the latter. During aging, both Bvra^−/− and Bvra^−/−Ugt1^−/− mice presented normal levels of relevant hematological and metabolic parameters. Interestingly, the oxidative status in erythrocytes from 9-months-old Bvra^−/− and Bvra^−/−Ugt1^−/− mice was significantly reduced. In addition, triglycerides levels in these 9-months-old Bvra^−/− mice were significantly higher than WT controls, while Bvra^−/−Ugt1^−/− tested normal. The normal parameters observed in Bvra^−/−Ugt1^−/− mice fed chow diet indicate that Bvra inhibition to treat unconjugated hyperbilirubinemia seems safe and effective.

Severe Presentation of Congenital Hemolytic Anemias in the Neonatal Age: Diagnostic and Therapeutic Issues

Congenital hemolytic anemias (CHAs) are a group of diseases characterized by premature destruction of erythrocytes as a consequence of intrinsic red blood cells abnormalities. Suggestive features of CHAs are anemia and hemolysis, with high reticulocyte count, unconjugated hyperbilirubinemia, increased lactate dehydrogenase (LDH), and reduced haptoglobin. The peripheral blood smear can help the differential diagnosis. In this review, we discuss the clinical management of severe CHAs presenting early on in the neonatal period. Appropriate knowledge and a high index of suspicion are crucial for a timely differential diagnosis and management. Here, we provide an overview of the most common conditions, such as glucose-6-phosphate dehydrogenase deficiency, pyruvate kinase deficiency, and hereditary spherocytosis. Although rare, congenital dyserythropoietic anemias are included as they may be suspected in early life, while hemoglobinopathies will not be discussed, as they usually manifest at a later age, when fetal hemoglobin (HbF) is replaced by the adult form (HbA).

Exchange transfusion for hemolytic hyperbilirubinemia: could some be averted by emergent administration of an inhibitor of bilirubin production?

OBJECTIVES

The objective of this study is to explore the hypothetical number of neonates where an exchange transfusion (ET) could be prevented by emergency administration of an inhibitor of bilirubin production.

STUDY DESIGN

We identified all neonates who received an ET in our NICUs during the past 12 years. We reviewed the indications for ET and recorded the time between ordering and beginning the exchange.

RESULTS

Forty-six neonates underwent ET, 37 (80.4%) for hemolytic hyperbilirubinemia (36.9 ± 2.9 weeks gestation and 2.5 ± 2.1 days old at ET). The mean delay period was 7.5 ± 3.5 h. Nine (19.6%) had ET not involving bilirubin.

CONCLUSIONS

A trial testing compounds that can inhibit bilirubin production would have about three eligible neonates/years in our system. Since our births are 1% of national, up to 300 neonates/years might qualify for such a study.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Cobalt protoporphyrin IX increases endogenous G-CSF and mobilizes HSC and granulocytes to the blood

Granulocyte colony‐stimulating factor (G‐CSF) is used in clinical practice to mobilize cells from the bone marrow to the blood; however, it is not always effective. We show that cobalt protoporphyrin IX (CoPP) increases plasma concentrations of G‐CSF, IL‐6, and MCP‐1 in mice, triggering the mobilization of granulocytes and hematopoietic stem and progenitor cells (HSPC). Compared with recombinant G‐CSF, CoPP mobilizes higher number of HSPC and mature granulocytes. In contrast to G‐CSF, CoPP does not increase the number of circulating T cells. Transplantation of CoPP‐mobilized peripheral blood mononuclear cells (PBMC) results in higher chimerism and faster hematopoietic reconstitution than transplantation of PBMC mobilized by G‐CSF. Although CoPP is used to activate Nrf2/HO‐1 axis, the observed effects are Nrf2/HO‐1 independent. Concluding, CoPP increases expression of mobilization‐related cytokines and has superior mobilizing efficiency compared with recombinant G‐CSF. This observation could lead to the development of new strategies for the treatment of neutropenia and HSPC transplantation.

Reductive effect of ursodeoxycholic acid on bilirubin levels in neonates on phototherapy

Background

Phototherapy is paramount in the management of high total serum bilirubin (TSB). Whether its effectiveness can be improved with ursodeoxycholic acid (UDCA) has not been evaluated among newborns of African descent.

Methods

A double-blind-controlled study was used to evaluate the effect of UDCA on the management of high TSB in neonates. Recruited neonates were categorized into the experimental group (given UDCA plus phototherapy) and the control group (phototherapy and plain syrup), and their TSB and conjugated bilirubin levels were measured. The data were analyzed using SPSS version 20. Statistical significance was set at a p-value of <0.05.

Results

The mean (SD) percentage reductions in TSB after 24 hrs were 40.73% (18.1) and 10.21% (7.1) in the experimental and control groups, respectively, and the difference was statistically significant (p=0.001). The mean (SD) durations on therapy were 3.0 days (0.58) in the experimental group and 5.5 days (1.35) in the control group (p=0.001).

Conclusions

Phototherapy is still effective in the management of neonatal hyperbilirubinemia, but inclusion of UDCA accentuates the reductive effect of phototherapy on the TSB in neonates, reducing the duration of treatment and in-patient care.

Progress in the development of selective heme oxygenase-1 inhibitors and their potential therapeutic application

Heme oxygenases (HOs) are a family of enzymes involved in the selective catabolism of free circulating heme. While HO-2 is constitutively expressed, HO-1 is strongly overexpressed under stressful stimuli (e.g., oxidative stress). Under these conditions, HO-1 exerts its strong cytoprotective activities and plays a crucial role in stimulating cell survival by removing the pro-oxidant heme and by producing carbon monoxide and biliverdin (promptly reduced to bilirubin). Unfortunately, the broad spectrum of HO-1 cytoprotective effects has been well experimentally documented both in normal and tumor cells, where the enzyme can be overexpressed, making it an exciting target in the management of some type of tumors. Development of non-competitive HO-1 inhibitors dates back in 2002 with the discovery of Azalanstat. Since then, many efforts have been devoted to the identification of selective HO-1 and HO-2 inhibitors and to unravel the molecular determinants responsible for selectivity. Molecular modeling studies supported the identification of chemical features involved in the recognition and inhibition of these enzymes. Herein, medicinal chemistry aspects and in silico studies related to the development of HO inhibitors will be discussed. The purpose of this review is to highlight recent advances in the development of new selective HO-1 and HO-2 inhibitors and covers the last six years (2013-2018).

Inhibition of Heme Oxygenase-1 Activity Enhances Wilms Tumor-1-Specific T-Cell Responses in Cancer Immunotherapy

Wilms tumor protein-1 (WT1) is an attractive target for adoptive T-cell therapy due to its expression in solid tumors and hematologic malignancies. However, T cells recognizing WT1 occur in low frequencies in the peripheral blood of healthy donors, limiting potential therapeutic possibilities. Tin mesoporphyrin (SnMP) is known to inhibit heme oxygenase-1 (HO-1), which has been shown to boost the activation and proliferation of human virus-specific T cells. We analyzed the influence of this effect on the generation of WT1-specific T cells and developed strategies for generating quantities of these cells from healthy donors, sufficient for adoptive T-cell therapies. HO-1 inhibition with SnMP increased WT1-specific T-cell frequencies in 13 (26%) of 50 healthy donors. To assess clinical applicability, we measured the enrichment efficiency of SnMP-treated WT1-specific T cells in response to a WT1-specific peptide pool and a HLA-A*02:01-restricted WT1 peptide by cytokine secretion assay. SnMP treatment resulted in a 28-fold higher enrichment efficacy with equal functionality. In conclusion, pharmacological inhibition of HO-1 activity with SnMP results in more efficient generation of functionally active WT1-specific T cells. This study demonstrates the therapeutic potentials of inhibiting HO-1 with SnMP to enhance antigen-specific T-cell responses in the treatment of cancer patients with WT1-positive disease.

Red Blood Cell Enzyme Disorders

Mature red blood cells are reliant on the glycolytic pathway for energy production and the hexose monophosphate shunt for cell protection from oxidative insults. The most common red blood cell enzyme disorders are characterized by hemolysis but with wide clinical variability. Glucose-6-phosphate dehydrogenase deficiency is the most common red cell enzyme disorder worldwide. Frequent clinical presentations include neonatal jaundice and episodic hemolysis after exposure to oxidative stress. Symptoms of pyruvate kinase deficiency and other glycolytic enzyme disorders include neonatal jaundice, chronic hemolytic anemia, gallstones, and transfusion-related and transfusion-independent iron overload. Diagnosis is critical for appropriate supportive care, monitoring, and treatment.

Clinical trial of tin mesoporphyrin to prevent neonatal hyperbilirubinemia

OBJECTIVE

To assess the efficacy of the heme oxygenase inhibitor, tin mesoporphyrin (SnMP), to reduce total bilirubin (TB) levels.

STUDY DESIGN

Masked, SnMP (4.5 mg kg(-1)), placebo-controlled, multicenter trial of single intramuscular injection to newborns ⩾35 weeks gestational age whose predischarge screening transcutaneous bilirubin (TcB) was >75th percentile.

RESULTS

Two hundred and thirteen newborns (median age 30 h) were randomized to treatment with SnMP (n=87) or 'sham' (n=89). We found that the duration of phototherapy was halved. Within 12 h of SnMP administration, the natural TB trajectory was reversed. At age 3 to 5 days, TB in the SnMP-treated group was +8% but sixfold lower than the 47% increase in the sham-treated group (P<0.001). At age 7 to 10 days, mean TB declined 18% (P<0.001) compared with a 7.1% increase among controls. No short-term adverse events from SnMP treatment were noted other than photoreactivity due to inadvertent exposure to white light phototherapy.

CONCLUSION

Early, predischarge SnMP administration decreased the duration of phototherapy, reversed TB trajectory and reduced the severity of subsequent hyperbilirubinemia.

Inhibition of heme oxygenase activity using a microparticle formulation of zinc protoporphyrin in an acute hemolytic newborn mouse model

BACKGROUND

Increased bilirubin production due to hemolysis can lead to neonatal hyperbilirubinemia. Inhibition of heme oxygenase (HO), the rate-limiting enzyme in heme catabolism, by metalloporphyrins (Mps) may be an ideal preventive strategy for neonatal hemolytic disease. Zinc protoporphyrin (ZnPP) is a naturally occurring Mp, potent, not phototoxic, with minimal HO-1 upregulation, but is not orally absorbed. Recently, we designed a lipid-based ZnPP formulation (ZnPP-Lipid), which is orally absorbed by newborn mice. Here, we evaluated the efficacy of ZnPP-Lipid in heme-loaded newborn mice, a model analogous to hemolytic infants.

METHODS

After 24 h of heme administration (30 µmol/kg s.c.), 4-d-old mice were given 30 µmol ZnPP-Lipid/kg via intragastric injections. After 3 h, liver and brain HO activity were measured. HO-1 upregulation was assessed by determinations of HO-1 protein, promoter activity, and mRNA by Western blot, in vivo bioluminescence imaging, and RT-PCR, respectively.

RESULTS

After heme loading, liver HO activity significantly increased ~1.6-fold, which was inhibited in a dose-dependent manner by ZnPP-Lipid. A dose of 30 µmol/kg returned activity to control levels. Brain HO activity was not inhibited. No significant increases in liver and brain HO-1 protein, promoter activity, and mRNA were observed.

CONCLUSION

ZnPP-Lipid is effective and thus has potential for treating neonatal hyperbilirubinemia due to hemolysis.

Phototherapy in ELBW newborns: does it work? Is it safe? The evidence from randomized clinical trials

Phototherapy is assumed to be both effective and safe for extremely low-birth-weight infants. Our objective was to critically assess the relevant evidence from randomized trials. In the decades-old Collaborative Phototherapy Trial, phototherapy reduced serum bilirubin but not neurodevelopmental impairments. In the recent and larger Neonatal Network Trial, aggressive phototherapy compared to conservative phototherapy reduced both peak serum bilirubin (7.0 vs. 9.8mg/dL) and profound impairment at 18-22 months adjusted age (relative risk = 0.68). However, both trials suggested that phototherapy increased deaths among the smallest infants. Conservative Bayesian analyses of ventilator-treated infants under 751g birth weight in the Network trial identified a 99% probability of increased deaths and 99% probability of reduced profound impairment with aggressive phototherapy. Potential strategies to optimize the risk/benefit ratio in achieving low serum bilirubin levels, e.g., use of lowered irradiance levels, light-emitting diode phototherapy units, cycled phototherapy, and/or porphyrin compounds, deserve rigorous evaluation.

Should we screen newborns for glucose-6-phosphate dehydrogenase deficiency in the United States?

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, a common X-linked enzymopathy can lead to severe hyperbilirubinemia, acute bilirubin encephalopathy and kernicterus in the United States. Neonatal testing for G6PD deficiency is not yet routine and the American Academy of Pediatrics recommends testing only in jaundiced newborns who are receiving phototherapy whose family history, ethnicity, or geographic origin suggest risk for the condition, or for infants whose response to phototherapy is poor. Screening tests for G6PD deficiency are available, are suitable for use in newborns and have been used in birth hospitals. However, US birth hospitals experience is limited and no national consensus has emerged regarding the need for newborn G6PD testing, its effectiveness or the best approach. Our review of current state of G6PD deficiency screening highlights research gaps and informs specific operational challenges to implement universal newborn G6PD testing concurrent to bilirubin screening in the United States.

Tin-mesoporphyrin in the treatment of refractory hyperbilirubinemia due to Rh incompatibility

We describe the use of tin-mesoporphyrin (SnMP) in the treatment of an infant with Rh hemolytic disease. The infant's hyperbilirubinemia responded to phototherapy but every time the phototherapy was discontinued, the serum bilirubin rebounded and repeat phototherapy was necessary. A single intramuscular dose of SnMP on day 18 eliminated the need for further phototherapy and allowed us to discharge this infant.

Metalloporphyrins - an update

Metalloporphyrins are structural analogs of heme and their potential use in the management of neonatal hyperbilirubinemia has been the subject of considerable research for more than three decades. The pharmacological basis for using this class of compounds to control bilirubin levels is the targeted blockade of bilirubin production through the competitive inhibition of heme oxygenase (HO), the rate-limiting enzyme in the bilirubin production pathway. Ongoing research continues in the pursuit of identifying ideal metalloporphyrins, which are safe and effective, by defining therapeutic windows and targeted interventions for the treatment of excessive neonatal hyperbilirubinemia.

Theoretical investigations on the hydrolysis pathway of tin verdoheme complexes: elucidation of tin's ring opening inhibition role

In order to obtain a better molecular understanding of inhibitory role of tin metal in the verdoheme ring opening process, hydrolysis of three possibly six, five, and four coordinate verdoheme complexes of tin(IV) and (II) have been studied using DFT method. The results of calculations indicate that, in excellent accord with experimental reports, hydrolysis of different possibly coordinated tin(IV) and (II) verdohemes does not lead to the opening of the macrocycle. Contrary to iron and zinc verdohemes, in five and four coordinate verdoheme complexes of tin(IV) and (II), formation of open ring helical complexes of tin are unfavorable both thermodynamically and kinetically. In these pathways, coordination of hydroxide nucleophile to tin metal due to the highly charged, exclusive oxophilicity nature of the Sn center, and high affinity of Sn to increase coordination state are proposed responsible as inhibiting roles of tin via the ring opening. While, in saturated six coordinate tin(IV) and (II) verdoheme complexes the ring opening of tin verdohemes is possible thermodynamically, but it is not predicted to occur from a kinetics point of view. In the six coordinate pathway, tin plays no coordination role and direct addition of hydroxide nucleophile to the positive oxo-carbon centers and formation of closed ring hydroxy compounds is proposed for preventing the verdoheme ring opening. These key points and findings have been corroborated by the results obtained from atomic charge analysis, geometrical parameters, and molecular orbital calculations. In addition, the results of inhibiting ring opening reaction of tin verdoheme complexes could support the great interest of tin porphyrin analogues as pharmacologic means of chemoprevention of neonatal jaundice by the competitive inhibitory action of tin porphyrins on heme oxygenase.

Inhibition of heme oxygenase activity in newborn mice by azalanstat

Inhibition of heme oxygenase (HO), the rate-limiting enzyme in heme catabolism, may be an ideal strategy for preventing neonatal jaundice. Although natural and synthetic heme analogs, called metalloporphyrins (Mps), have been extensively investigated for this purpose, some Mps are phototoxic, affect the activity of other enzymes, or induce HO-1 transcription-properties that may limit their clinical use. Another class of compounds, imidazole-dioxolanes, has been shown to selectively inhibit the inducible isozyme HO-1. Therefore, we investigated the efficacy of azalanstat (AZA), an imidazole-dioxolane, towards inhibiting HO activity in 7-day-old mice. We found that a single dose of AZA at 500 micromol.kg(-1) body mass (BM) administered i.p. significantly inhibited HO activity and reduced in vivo bilirubin production. In the spleen, HO inhibition (>50%) was observed within 0.25-3 h after administration. After 24 h, however, spleen HO activity, HO-1 protein, and HO-1 mRNA levels significantly increased 1.2-, 2.4-, and 4.0-fold, respectively. We conclude that AZA effectively inhibits in vivo HO activity only at a high dose and that it also induces spleen HO-1 gene transcription. Therefore, other imidazole-dioxolanes should be evaluated to determine whether they are more potent than AZA for use in treating neonatal jaundice.

Pharmacological and clinical aspects of heme oxygenase

This review is intended to stimulate interest in the effect of increased expression of heme oxygenase-1 (HO-1) protein and increased levels of HO activity on normal and pathological states. The HO system includes the heme catabolic pathway, comprising HO and biliverdin reductase, and the products of heme degradation, carbon monoxide (CO), iron, and biliverdin/bilirubin. The role of the HO system in diabetes, inflammation, heart disease, hypertension, neurological disorders, transplantation, endotoxemia and other pathologies is a burgeoning area of research. This review focuses on the clinical potential of increased levels of HO-1 protein and HO activity to ameliorate tissue injury. The use of pharmacological and genetic probes to manipulate HO, leading to new insights into the complex relationship of the HO system with biological and pathological phenomena under investigation, is reviewed. This information is critical in both drug development and the implementation of clinical approaches to moderate and to alleviate the numerous chronic disorders in humans affected by perturbations in the HO system.

The Galpha12/13 family of heterotrimeric G proteins and the small GTPase RhoA link the Kaposi sarcoma-associated herpes virus G protein-coupled receptor to heme oxygenase-1 expression and tumorigenesis

Heme oxygenase-1 (HO-1), an inducible enzyme that metabolizes the heme group, is highly expressed in human Kaposi sarcoma lesions. Its expression is up-regulated by the G protein-coupled receptor from the Kaposi sarcoma-associated herpes virus (vGPCR). Although recent evidence shows that HO-1 contributes to vGPCR-induced tumorigenesis and vascular endothelial growth factor (VEGF) expression, the molecular steps that link vGPCR to HO-1 remain unknown. Here we show that vGPCR induces HO-1 expression and transformation through the Galpha(12/13) family of heterotrimeric G proteins and the small GTPase RhoA. Targeted small hairpin RNA knockdown expression of Galpha(12), Galpha(13), or RhoA and inhibition of RhoA activity impair vGPCR-induced transformation and ho-1 promoter activity. Knockdown expression of RhoA also reduces vGPCR-induced VEFG-A secretion and blocks tumor growth in a murine allograft tumor model. NIH-3T3 cells expressing constitutively activated Galpha(13) or RhoA implanted in nude mice develop tumors displaying spindle-shaped cells that express HO-1 and VEGF-A, similarly to vGPCR-derived tumors. RhoAQL-induced tumor growth is reduced 80% by small hairpin RNA-mediated knockdown expression of HO-1 in the implanted cells. Likewise, inhibition of HO-1 activity by chronic administration of the HO-1 inhibitor tin protoporphyrin IX to mice reduces RhoAQL-induced tumor growth by 70%. Our study shows that vGPCR induces HO-1 expression through the Galpha(12/13)/RhoA axes and shows for the first time a potential role for HO-1 as a therapeutic target in tumors where RhoA has oncogenic activity.

The global market for ADHD medications

Little is known about the global use and cost of medications for attention deficit hyperactivity disorder (ADHD). Global use of ADHD medications rose threefold from 1993 through 2003, whereas global spending (2.4 billion US dollars in 2003) rose ninefold, adjusting for inflation. Per capita gross domestic product (GDP) robustly predicted use across countries, but the United States, Canada, and Australia showed significantly higher-than-predicted use. Use and spending grew in both developed and developing countries, but spending growth was concentrated in developed countries, which adopted more costly, long-acting formulations. Promoting optimal prescription and monitoring should be a priority.

Systemic effects of orally-administered zinc and tin (IV) metalloporphyrins on heme oxygenase expression in mice

Some metalloporphyrins (Mps) inhibit heme oxygenase (HO), the rate-limiting enzyme in the production of bilirubin, and are potential compounds for the treatment of neonatal jaundice. We studied the safety and efficacy of Mps following oral administration. Adult HO-1-luc reporter mice were administered 30 micromol/kg body weight of tin mesoporphyrin (SnMP), zinc bis glycol deuteroporphyrin (ZnBG), or zinc protoporphyrin (ZnPP), or vehicle by oral gavage. Bilirubin production was measured as total body carbon monoxide (CO) excretion (VeCO). HO activity was quantitated via CO measurements by gas chromatography. HO-1 protein was determined by Western blot. HO-1 transcription levels were assessed by in vivo bioluminescence imaging. A significant 28% decrease in bilirubin production occurred within 3 h of SnMP treatment and persisted beyond 48 h. Bilirubin production decreased 15% and 9% by 3 h after administration of ZnBG and ZnPP, respectively, but returned to baseline within 48 h. Maximal inhibition of liver, spleen, and intestine HO activity was seen at 3 h with inhibitory effects decreasing in the order: SnMP > or = ZnBG > or = ZnPP. After SnMP treatment, HO-1 transcription increased 5.7-fold after 24 h. Furthermore, liver and spleen HO-1 protein significantly increased 3.7- and 2.0-fold, respectively, after 24 h. HO-1 transcription and protein were not affected in ZnBG- or ZnPP-treated mice. We conclude that the three Mps are absorbed at different rates in the mouse and affect bilirubin production and HO-1 expression in a tissue- and time-dependent manner.

Inhibition of heme oxygenase-1 interferes with the transforming activity of the Kaposi sarcoma herpesvirus-encoded G protein-coupled receptor

Heme oxygenase-1 (HO-1), the inducible enzyme responsible for the rate-limiting step in the heme catabolism, is expressed in AIDS-Kaposi sarcoma (KS) lesions. Its expression is up-regulated by the Kaposi sarcoma-associated herpesvirus (KSHV) in endothelial cells, but the mechanisms underlying KSHV-induced HO-1 expression are still unknown. In this study we investigated whether the oncogenic G protein-coupled receptor (KSHV-GPCR or vGPCR), one of the key KSHV genes involved in KS development, activated HO-1 expression. Here we show that vGPCR induces HO-1 mRNA and protein levels in fibroblasts and endothelial cells. Moreover, targeted knock-down gene expression of HO-1 by small hairpin RNA and chemical inhibition of HO-1 enzymatic activity by tin protoporphyrin IX (SnPP), impaired vGPCR-induced survival, proliferation, transformation, and vascular endothelial growth factor (VEGF)-A expression. vGPCR-expressing cells implanted in the dorsal flank of nude mice developed tumors with elevated HO-1 expression and activity. Chronic administration of SnPP to the implanted mice, under conditions that effectively blocked HO-1 activity and VEGF-A expression in the transplanted cells, strikingly reduced tumor growth, without apparent side effects. On the contrary, administration of the HO-1 inducer cobalt protoporphyrin (CoPP) further enhanced vGPCR-induced tumor growth. These data postulate HO-1 as an important mediator of vGPCR-induced tumor growth and suggest that inhibition of intratumoral HO-1 activity by SnPP may be a potential therapeutic strategy.

The evolution of neonatology

In 1960, the terms "neonatology" and "neonatologist" were introduced. Thereafter, an increasing number of pediatricians devoted themselves to full-time neonatology. In 1975, the first examination of the Sub-Board of Neonatal-Perinatal Medicine of the American Board of Pediatrics and the first meeting of the Perinatal Section of the American Academy of Pediatrics were held. One of the most important factors that improved the care of the neonate was the miniaturization of blood samples needed to determine blood gases, serum electrolytes, glucose, calcium, bilirubin, and other biochemical measurements. Another factor was the ability to provide nutrition intravenously, and the third was the maintenance of normal body temperature. The management of respiratory distress syndrome improved with i.v. glucose and correction of metabolic acidosis, followed by assisted ventilation, continuous positive airway pressure, antenatal corticosteroid administration, and the introduction of exogenous surfactant. Pharmacologic manipulation of the ductus arteriosus, support of blood pressure, echocardiography, and changes in the management of persistent pulmonary hypertension, including the use of nitric oxide and extracorporeal membrane oxygenation, all have influenced the cardiopulmonary management of the neonate. Regionalization of neonatal care; changes in parent-infant interaction; and technological changes such as phototherapy, oxygen saturation monitors, and brain imaging techniques are among the important advances reviewed in this report. Most remarkable, a 1-kg infant who was born in 1960 had a mortality risk of 95% but had a 95% probability of survival by 2000. However, errors in neonatology are acknowledged, and potential directions for the future are explored.

A randomized, triple-blind, placebo-controlled trial of prophylactic oral phenobarbital to reduce the need for phototherapy in G6PD-deficient neonates

OBJECTIVE

Decreased conjugation is probably more important than hemolysis for causing jaundice in G6PD-deficient neonates. The role of enzyme inducers, like phenobarbital, in G6PD deficiency is unclear. This randomized controlled trial was performed to evaluate Phenobarbital's role in reducing the need for phototherapy among G6PD-deficient neonates.

STUDY DESIGN

This stratified, randomized, triple-blinded, placebo-controlled trial was conducted in a level III NICU. Consecutive babies with gestation >/=34 weeks and birth weight >/=1800 g were screened from cord blood. G6PD-deficient neonates, who were otherwise healthy, were enrolled. Rh isoimmunization, maternal Phenobarbital use and lack of parental consent were exclusion criteria. Subjects were randomly allocated to receive 5 mg/kg day of oral phenobarbital/ placebo for first 3 days. They were monitored daily for total serum bilirubin (TSB) until declining TSB was documented twice. The primary outcome was requirement for phototherapy and secondary outcomes were duration of phototherapy, need for exchange transfusion, peak TSB and adverse effects. Sample size of 56 could detect a decline in phototherapy requirement from 40 to 5% with 80% power and 5% error.

RESULTS

Of 2370 babies screened, 63 were G6PD-deficient. Of them, 56 eligible babies were allocated to phenobarbital (n=27) or placebo (n=29). The mean age of administration of the first dose was 18.55+/-7.3 h. In total, 44% in phenobarbital group and 41% in placebo group required phototherapy (p=1.0). There was no significant difference in exchange transfusion rates (18.5 vs 10%, p=0.46). No baby had adverse reactions.

CONCLUSION

Prophylactic oral phenobarbital does not decrease the need for phototherapy or exchange transfusions in G6PD-deficient neonates.

Changes in gene expression profiles of multiple myeloma cells induced by arsenic trioxide (ATO): possible mechanisms to explain ATO resistance in vivo

Multiple myeloma (MM) is an incurable plasma cell malignancy marked by eventual resistance to therapy. Although arsenic trioxide (ATO) can induce apoptosis in MM cell lines, the in vivo activity of ATO in MM has been disappointing. The existence of ATO resistance mechanisms in MM can be inferred. We sought to generate hypotheses for ATO resistance by studying the gene expression profiles of MM cells that survived in culture with 0.5 micromol/l ATO. Among the 31 genes whose quantitative levels of expression (QLE) significantly increased in ATO were haem oxygenase 1 (HO-1) and metallothionein-2A (MT-2A). Among the 56 genes whose QLE were significantly decreased were genes that modulate cell cycling [BTBD2 and IGFBP7 (mac25)] and sensitivity to reactive oxygen species (ROS) (BACH2). HO-1 exerts an anti-apoptotic effect in ischaemic cells, and MT-2A chelates ATO intracellularly. Inhibition of HO-1 with tin protoporphyrin enhances ROS in MM cells in ATO, and addition of N-acetylcysteine increases MT-2A. Protective antioxidant responses occur in MM cells exposed to ATO, and may occur in stromal cells as well, and act to quench ROS and provide diffusible anti-apoptotic factors. They may also involve cysteine-rich proteins that chelate ATO and modulate redox-sensitive residues on proteins, such as nuclear factor kappa B and p53. A better understanding of ATO resistance will enable ATO to be combined with other agents for MM.

Antioxidant mechanism of heme oxygenase-1 involves an increase in superoxide dismutase and catalase in experimental diabetes

Increased heme oxygenase (HO)-1 activity attenuates endothelial cell apoptosis and decreases superoxide anion (O2-) formation in experimental diabetes by unknown mechanisms. We examined the effect of HO-1 protein and HO activity on extracellular SOD (EC-SOD), catalase, O2-, inducible nitric oxide synthase (iNOS), and endothelial nitric oxide synthase (eNOS) levels and vascular responses to ACh in control and diabetic rats. Vascular EC-SOD and plasma catalase activities were significantly reduced in diabetic compared with nondiabetic rats (P < 0.05). Upregulation of HO-1 expression by intermittent administration of cobalt protoporphyrin, an inducer of HO-1 protein and activity, resulted in a robust increase in EC-SOD but no significant change in Cu-Zn-SOD. Administration of tin mesoporphyrin, an inhibitor of HO-1 activity, decreased EC-SOD protein. Increased HO-1 activity in diabetic rats was associated with a decrease in iNOS but increases in eNOS and plasma catalase activity. On the other hand, aortic ring segments from diabetic rats exhibited a significant reduction in vascular relaxation to ACh, which was reversed with cobalt protoporphyrin treatment. These data demonstrate that an increase in HO-1 protein and activity, i.e., CO and bilirubin production, in diabetic rats brings about a robust increase in EC-SOD, catalase, and eNOS with a concomitant increase in endothelial relaxation and a decrease in O2-. These observations in experimental diabetes suggest that the vascular cytoprotective mechanism of HO-1 against oxidative stress requires an increase in EC-SOD and catalase.

Recent advances in the pharmacotherapy for hyperbilirubinaemia in the neonate

Jaundice is a common cause for diagnostic works-up and therapeutic intervention in neonates. This is motivated by the risk for severe neurological sequelae (kernicterus). The mainstays of treatment for the past decades have been exchange transfusion and phototherapy. Exchange transfusion is now becoming rare due to immune prophylaxis in Rhesus-negative women, and treatment of sensitised infants with intravenous immunoglobulin. Several different pharmacological approaches have been studied as far as the treatment of neonatal jaundice. Of these, the focus of attention in recent years has been on the haem oxygenase inhibitors (metal meso- and protoporphyrins). These are effective inhibitors of bilirubin production and have been shown to significantly reduce peak serum bilirubin levels in several clinical trials, both when used prophylactically and therapeutically. However, questions remain regarding long-term safety, as well as the advisability of whole-scale inhibition of bilirubin production. Nevertheless, in selected infants with a high risk of severe jaundice, the use of haem oxygenase inhibitors may be acceptable. Pharmacotherapy in jaundiced infants is fraught with risks, as many drugs may increase the entry of bilirubin into the brain and presumably, the risk for neurotoxicity. Both the displacement of bilirubin from its albumin binding and interference with the function of phosphoglycoprotein in the blood-brain barrier are documented mechanisms in this respect.

Chemoprevention of severe neonatal hyperbilirubinemia

The uses of synthetic heme analogues that are competitive inhibitors of heme oxygenase, the rate-limiting enzyme in the production of bilirubin, represent a novel means of controlling severe hyperbilirubinemia in the newborn. The logic of this approach and the use of stannsoporfin (tin mesoporphyrin) as the compound of choice are discussed.

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.

In vivo role of heme oxygenase in ischemic coronary vasodilation

The heart constitutively expresses heme oxygenase (HO)-2, which catabolizes heme-containing proteins to produce biliverdin and carbon monoxide (CO). The heart also contains many possible substrates for HO-2 such as heme groups of myoglobin and cytochrome P-450s, which potentially could be metabolized into CO. As a result of observations that CO activates guanylyl cyclase and induces vascular relaxation and that HO appears to confer protection from ischemic injury, we hypothesized that the HO-CO pathway is involved in ischemic vasodilation in the coronary microcirculation. Responses of epicardial coronary arterioles to ischemia (perfusion pressure approximately 40 mmHg; flow velocity decreased by approximately 50%; dL/dt reduced by approximately 60%) were measured using stroboscopic fluorescence microangiography in 34 open-chest anesthetized dogs. Ischemia caused vasodilation of coronary arterioles by 36 +/- 6%. Administration of N(G)-monomethyl-L-arginine (L-NMMA, 3 micromol.kg(-1).min(-1) intracoronary), indomethacin (10 mg/kg iv), and K(+) (60 mM, epicardial suffusion) to prevent the actions of nitric oxide, prostaglandins, and hyperpolarizing factors, respectively, partially inhibited dilation during ischemia (36 +/- 6 vs. 15 +/- 4%; P < 0.05). The residual vasodilation during ischemia after antagonist administration was inhibited by tin mesoporphyrin IX (SnMP, 10 mg/kg iv), which is an inhibitor of HO (15 +/- 4 vs. 7 +/- 2%; P < 0.05 vs. before SnMP). The guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (10(-5) M, epicardial suffusion) also inhibited vasodilation during ischemia in the presence of L-NMMA with indomethacin and KCl. Moreover, administration of heme-L-arginate, which is a substrate for HO, produced dilation after ischemia but not after control conditions. We conclude that during myocardial ischemia, HO-2 activation can produce cGMP-mediated vasodilation presumably via the production of CO. This vasodilatory pathway appears to play a backup role and is activated only when other mechanisms of vasodilation during ischemia are exhausted.

Tin-mesoporphyrin in the treatment of severe hyperbilirubinemia in a very-low-birth-weight infant

Tin-mesoporphyrin (SnMP) is a competitive inhibitor of microsomal heme oxygenase (the rate-limiting enzyme in the heme catabolic pathway). It was administered as a single intramuscular dose at 46 hours of life to a very-low-birth-weight infant with severe hemolytic hyperbilirubinemia who had been awaiting an exchange transfusion. This case documents the effective elimination of the need for an exchange transfusion in a very-low-birth-weight infant and is a confirmation of the experience of others for the use of SnMP in reducing bilirubin production.

The heme-heme oxygenase system: a molecular switch in wound healing

When cells are injured they release their contents, resulting in a local accumulation of free heme proteins and heme. Here, we investigated the involvement of heme and its degrading enzyme heme oxygenase (HO) in the inflammatory process during wound healing. We observed that heme directly accumulates at the edges of the wound after inflicting a wound in the palate of Wistar rats. This coincided with an increased adhesion molecule expression and the recruitment of leukocytes. To prove that heme is responsible for the recruitment of leukocytes, heme was administered intradermally 24 hours prior to injury. A clear heme-induced influx of both macrophages and granulocytes was observed. When examining the HO isoforms, HO-1 and HO-2, we found that HO-2 was present in the entire submucosa. Surprisingly, we observed also that HO-1 is significantly expressed in the epithelium of both the mucosa and the skin of animals without wounds. On inflammation, HO-1 expression increased, particularly in infiltrating cells during the resolution phase of inflammation. Interestingly, we observed that heme-induced influx of leukocytes was highly elevated after pharmacologic inhibition of HO activity. These observations suggest that the heme-HO system is closely involved in the control of wound healing. Our results demonstrate that the local release of heme may be a physiologic trigger to start inflammatory processes, whereas HO-1 antagonizes inflammation by attenuating adhesive interactions and cellular infiltration. Moreover, the basal level of HO expression in the skin may serve as a first protective environment against acute oxidative and inflammatory insults.

Metalloporphyrins for treatment of unconjugated hyperbilirubinemia in neonates

BACKGROUND

Metalloporphyrins are heme analogues that inhibit heme oxygenase, the rate-limiting enzyme in the catabolism of heme to bilirubin. By preventing the formation of bilirubin, they have the potential to reduce the level of unconjugated bilirubin in neonates and thereby reduce the risk of neonatal encephalopathy and long term neurodevelopmental impairment from bilirubin toxicity to the nervous system.

OBJECTIVES

1. To determine the efficacy of metalloporphyrins in reducing bilirubin levels, reducing the need for phototherapy or exchange transfusion and reducing the incidence of bilirubin encephalopathy in neonates with unconjugated hyperbilirubinemia when compared to placebo, phototherapy or exchange transfusion. 2. To determine the nature and frequency of side effects of metalloporphyrins when used to treat unconjugated hyperbilirubinemia in neonates.

SEARCH STRATEGY

We searched Medline (1966 - January 2003) and the Cochrane Controlled Trials Register (CCTR) from the Cochrane Library (2003, issue 1). We hand-searched the articles cited in each publication obtained. We hand searched the abstracts of the Society for Pediatric Research (USA) (published in Pediatric Research) for the years 1985 - 2002.

SELECTION CRITERIA

We included only randomized controlled studies, in which preterm or term neonates (age 28 days of life or less) with unconjugated hyperbilirubinemia due to any cause were randomly allocated to receive a metalloporphyrin in the treatment arm(s), and to receive a placebo or a conventional treatment (phototherapy or exchange transfusion) or no treatment for hyperbilirubinemia in the comparison arm(s). Any preparation of metalloporphyrin could be used, in any form, by any route, at any dose.

DATA COLLECTION AND ANALYSIS

Two authors extracted data independently. Data were entered into Revman by one author and checked by a second author. Prespecified subgroup analyses were planned in term versus preterm infants, hemolytic versus non-hemolytic causes of jaundice and according to the type of metalloporphyrin used.

MAIN RESULTS

Three small studies, enrolling a total of 170 infants, were eligible for inclusion in this review. None blinded intervention or outcome assessment. In all three studies some patients were excluded after randomization. Metalloporphyrin-treated infants appeared to have short-term benefits compared to controls, including a lower maximum plasma bilirubin level in one study, a lower frequency of severe hyperbilirubinemia in one study, a decreased need for phototherapy, fewer plasma bilirubin measurements and a shorter duration of hospitalization. None of the enrolled infants required an exchange transfusion in the two studies that described this outcome. None of the studies reported on neonatal kernicterus, death, long-term neurodevelopmental outcomes or iron deficiency anemia. Though a small number of metalloporphyrin-treated as well as control infants developed a photosensitivity rash, the trials were too small to rule out an increase in the risk of photosensitivity or other adverse effects from metalloporphyrin treatment. No subgroup analyses were possible due to the small number of included trials.

REVIEWER'S CONCLUSIONS

Treatment of neonatal unconjugated hyperbilirubinemia with metalloporphyrins may reduce neonatal bilirubin levels and decrease the need for phototherapy and hospitalization. There is no evidence to support or refute the possibility that treatment with a metalloporphyrin decreases the risk of neonatal kernicterus or of long-term neurodevelopmental impairment due to bilirubin encephalopathy. There is no evidence to support or refute the possibility that cutaneous photosensitivity is increased with metalloporphyrin treatment. Routine treatment of neonatal unconjugated hyperbilirubinemia with a metalloporphyrin cannot be recommended at present.

Protective effect of HO-1 against oxidative stress in human hepatoma cell line (HepG2) is independent of telomerase enzyme activity

Heme oxygenase-1 (HO-1) is a stress response protein and its induction is associated with protection against oxidative stress. Cell survival during exposure to environmental stresses is associated with elevation of HO-1. Telomerase plays an important role in cell proliferation and immortalization. Our objective was to determine whether the adaptive cellular response to survive exposure to environmental stresses is dependent on expression of HO-1 and telomerase activity in hepatoma cell line (HepG2). Exposure of HepG2 to oxidants, H(2)O(2) (100 microM), as well as HO-1 inducers, heme (10 microM) and stannic chloride (SnCl(2)) (10 microM), resulted in an increased HO-1 mRNA, protein and total HO activity. On the other hand, HO activity was inhibited by addition of stannic mesoporphyrin (SnMP) (10 microM). These effects were brought about without altering endogenous HO-2 protein levels. Telomerase activity was not affected by oxidants, inducers of HO-1 or inhibitors of HO activity. Similarly, the catalytic subunit of telomerase enzyme human telomerase reverse transcriptase (hTERT), which is considered as the major regulator of telomerase activity, was not affected by oxidants, heme and H(2)O(2), or downregulation of HO gene activity by SnMP. This study demonstrates, for the first time, that induction of HO-1 gene mediates protection against oxidants and increases cell survival by a mechanism independent of telomerase enzyme activity. Suppression of HO activity by SnMP decreased cell resistance to oxidant stressors without altering telomerase activity.

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.

A significant role for the heme oxygenase-1 gene in endothelial cell cycle progression

Heme oxygenase (HO) catalyzes the conversion of heme to biliverdin with the release of iron and carbon monoxide. HO-1 is inducible by inflammatory conditions, which cause oxidative stress in endothelial cells. Overexpression of human HO-1 in endothelial cells may have the potential to provide protection against a variety of agents that cause oxidative stress. We investigated the physiological significance of human HO-1 overexpression, using a retroviral vector, on cell cycle progression in the presence and absence of pyrrolidine dithiocarbamate (PDTC). The addition of PDTC (25 and 50 microM) to human microvessel endothelial cells over 24 h resulted in significant (P < 0.05) abnormalities in DNA distribution and cell cycle progression compared to cells overexpressing the HO-1 gene. The addition of PDTC resulted in a significantly decreased G(1) phase and an increased G(2)/M phase in the control cells, but not in cells transduced with the human HO-1 gene (P < 0.05). Further, PDTC had a potent effect on DNA distribution abnormalities in exponentially grown cells compared to subconfluent cells. Upregulation of HO activity in endothelial cells, as a result of overexpressing human HO-1, prevented PDTC-mediated abnormalities in DNA distribution. Inhibition of HO activity by tin-mesoporphyrin (SnMP) (30 microM) resulted in enhancement of PDTC-mediated abnormalities in cell cycle progression. Bilirubin or iron did not mediate DNA distribution. We conclude that an increase in endothelial cell HO-1 activity with subsequent generation of carbon monoxide, elicited by gene transfer, reversed the PDTC-mediated abnormalities in cell cycle progression and is thus a potential therapeutic means for attenuating the effects of oxidative stress-causing agents.

Sn-Mesoporphyrin interdiction of severe hyperbilirubinemia in Jehovah's Witness newborns as an alternative to exchange transfusion

OBJECTIVE

The religious convictions of parents who are Jehovah's Witness adherents lead them to reject the use of exchange transfusions as therapy for severe hyperbilirubinemia in newborns in whom intensive phototherapy has failed to control this problem. Consequently, physicians caring for such infants may be obliged to initiate legal action to compel use of the procedure when severe hyperbilirubinemia not sufficiently responsive to phototherapy warrants an exchange transfusion. Our goal was to determine if we could use the potent inhibitor of bilirubin production, Sn-Mesoporphyrin (SnMP), to resolve the troubling medical-legal issues in such situations in 2 infants with hemolytic disease of the newborn who required exchange transfusions for severe hyperbilirubinemia but whose Jehovah's Witness parents rejected the procedure. SnMP was administered in a single dose, as in previous studies, at the time when exchange transfusion would have been initiated and plasma bilirubin levels were monitored at close intervals thereafter.

METHODS

SnMP is a potent inhibitor of heme oxygenase, the rate-limiting enzyme in catabolism of heme to bilirubin. We found in earlier studies that in single doses of 6 micromol/kg birth weight, SnMP is extremely effective in moderating the course of hyperbilirubinemia and in eliminating the need for supplemental phototherapy in jaundiced newborns. In the 2 cases described, a single dose of SnMP (6 micromol/kg birth weight) was administered intramuscularly to severely jaundiced infants with immune hemolysis at a time when clinical circumstances dictated the need for exchange transfusion. CASE 1: This patient was a preterm male infant (gestational age: 35 5/7 weeks; birth weight: 2790 g) whose plasma bilirubin concentration (PBC) at 1 hour after birth was 5.0 mg/dL. Despite intensive phototherapy with 3 banks of lights and 1 biliblanket, the PBC increased steadily with no diminution in the rate of increase for 75 hours. In view of the problems of immune hemolysis, and prematurity, and the inability of phototherapy to stop progression of hyperbilirubinemia, a decision to carry out an exchange transfusion was made; the decision was, however, rejected by the Jehovah's Witness parents. Pending legal action to compel use of the procedure, a request to this (Rockefeller) laboratory for SnMP was made; its use was approved by the Food and Drug Administration; and the inhibitor was delivered to the physician-in-charge (D.P.M.) in Sioux Falls, South Dakota. The single dose of SnMP was administered to the infant at 75 hours after birth; the course of hyperbilirubinemia before and after the use of the inhibitor is shown in Fig 1. [figure: see text]. CASE 2: This female term infant (gestational age: 38-39 weeks; birth weight: 4140 g) with immune hemolysis was delivered by cesarean section and because of problems related to meconium aspiration required helicopter transfer to the Special Care Nursery in Abilene, Texas, where 10 hours after birth the first PBC was determined to be 18.0 mg/dL. Double-bank phototherapy plus a biliblanket was initiated; a third bank of lights was later ordered. The PBC fluctuated in the ensuing 2 days between 13.8 to 25.8 mg/dL during which suggestive clinical signs of possible bilirubin encephalopathy became manifest. In view of the clinical circumstances and the continued severe hyperbilirubinemia, permission for a double-exchange transfusion was requested. The parents, who were Jehovah's Witness adherents, refused the procedure. While preparing legal action to compel use of the exchange, a request was made to this (Rockefeller) laboratory for use of SnMP to attempt control of hyperbilirubinemia. With FDA approval, the SnMP was delivered to the attending neonatologist (J. R. M.) in Abilene and administered in a single dose (6 micromol/kg birth weight) at 56 hours after birth when the PBC was 19.5 mg/dL. The course of bilirubinemia before and after SnMP use is shown in Fig 2. [figure: see text].

RESULTS AND CONCLUSIONS

The use of SnMP to moderate or prevent the development of severe hyperbilirubinemia in newborns (preterm, near-term, term with high PBCs [15-18 mg/dL], ABO-incompatibility; glucose-6-phosphate dehydrogenase deficiency) has been extensively studied in carefully conducted clinical trials the results of which have been reported earlier. This inhibitor of bilirubin production has demonstrated marked efficacy in moderating the course of hyperbilirubinemia in all diagnostic groups of unconjugated neonatal jaundice. The 2 cases described in this report confirmed the efficacy of SnMP in terminating progression of hyperbilirubinemia in infants in whom phototherapy had failed to sufficiently control the problem and whose parents, for religious reasons, would not permit exchange transfusions. Interdiction of severe hyperbilirubinemia by inhibiting the production of bilirubin with SnMP can be an effective alternative to the use of exchange transfusion in the management of severe newborn jaundice that has not responded sufficiently to light treatment to ease concern about the development of bilirubin encephalopathy.

Regulation of human heme oxygenase in endothelial cells by using sense and antisense retroviral constructs

Our objective was to determine whether overexpression and underexpression of human heme oxygenase (HHO)-1 could be controlled on a long-term basis by introduction of the HO-1 gene in sense (S) and antisense (AS) orientation with an appropriate vector into endothelial cells. Retroviral vector (LXSN) containing viral long terminal repeat promoter-driven human HO-1 S (LSN-HHO-1) and LXSN vectors containing HHO-1 promoter (HOP)-controlled HHO-1 S and AS (LSN-HOP-HHO-1 and LSN-HOP-HHO-1-AS) sequences were constructed and used to transfect rat lung microvessel endothelial cells (RLMV cells) and human dermal microvessel endothelial cells (HMEC-1 cells). RLMV cells transduced with HHO-1 S expressed human HO-1 mRNA and HO-1 protein associated with elevation in total HO activity compared with nontransduced cells. Vector-mediated expression of HHO-1 S or AS under control of HOP resulted in effective production of HO-1 or blocked induction of endogenous human HO-1 in HMEC-1 cells, respectively. Overexpression of HO-1 AS was associated with a long-term decrease (45%) of endogenous HO-1 protein and an increase (167%) in unmetabolized exogenous heme in HMEC-1 cells. Carbon monoxide (CO) production in HO-1 S- or AS-transduced HMEC-1 cells after heme treatment was increased (159%) or decreased (50%), respectively, compared with nontransduced cells. HO-2 protein levels did not change. These findings demonstrate that HHO-1 S and AS retroviral constructs are functional in enhancing and reducing HO activity, respectively, and thus can be used to regulate cellular heme levels, the activity of heme-dependent enzymes, and the rate of heme catabolism to CO and bilirubin.