Chemoprevention of severe neonatal hyperbilirubinemia

Chemoprevention of bilirubin encephalopathy with a nanoceutical agent

BACKGROUND

Targeted rapid degradation of bilirubin has the potential to thwart incipient bilirubin encephalopathy. We investigated a novel spinel-structured citrate-functionalized trimanganese tetroxide nanoparticle (C-Mn3O4 NP, the nanodrug) to degrade both systemic and neural bilirubin loads.

METHOD

Severe neonatal unconjugated hyperbilirubinemia (SNH) was induced in neonatal C57BL/6j mice model with phenylhydrazine (PHz) intoxication. Efficiency of the nanodrug on both in vivo bilirubin degradation and amelioration of bilirubin encephalopathy and associated neurobehavioral sequelae were evaluated.

RESULTS

Single oral dose (0.25 mg kg-1 bodyweight) of the nanodrug reduced both total serum bilirubin (TSB) and unconjugated bilirubin (UCB) in SNH rodents. Significant (p < 0.0001) UCB and TSB-degradation rates were reported within 4-8 h at 1.84 ± 0.26 and 2.19 ± 0.31 mg dL-1 h-1, respectively. Neural bilirubin load was decreased by 5.6 nmol g-1 (p = 0.0002) along with improved measures of neurobehavior, neuromotor movements, learning, and memory. Histopathological studies confirm that the nanodrug prevented neural cell reduction in Purkinje and substantia nigra regions, eosinophilic neurons, spongiosis, and cell shrinkage in SNH brain parenchyma. Brain oxidative status was maintained in nanodrug-treated SNH cohort. Pharmacokinetic data corroborated the bilirubin degradation rate with plasma nanodrug concentrations.

CONCLUSION

This study demonstrates the in vivo capacity of this novel nanodrug to reduce systemic and neural bilirubin load and reverse bilirubin-induced neurotoxicity. Further compilation of a drug-safety-dossier is warranted to translate this novel therapeutic chemopreventive approach to clinical settings.

IMPACT

None of the current pharmacotherapeutics treat severe neonatal hyperbilirubinemia (SNH) to prevent risks of neurotoxicity. In this preclinical study, a newly investigated nano-formulation, citrate-functionalized Mn3O4 nanoparticles (C-Mn3O4 NPs), exhibits bilirubin reduction properties in rodents. Chemopreventive properties of this nano-formulation demonstrate an efficacious, efficient agent that appears to be safe in these early studies. Translation of C-Mn3O4 NPs to prospective preclinical and clinical trials in appropriate in vivo models should be explored as a potential novel pharmacotherapy for SNH.

Hyperbilirubinemia in Preterm Neonates

Preterm neonates with increased bilirubin production loads are more likely to sustain adverse outcomes due to either neurotoxicity or overtreatment with phototherapy and/or exchange transfusion. Clinicians should rely on expert consensus opinions to guide timely and effective interventions until there is better evidence to refine bilirubin-induced neurologic dysfunction or benefits of bilirubin. In this article, we review the evolving evidence for bilirubin-induced brain injury in preterm infants and highlight the clinical approaches that minimize the risk of bilirubin neurotoxicity.

A heme oxygenase-1 transducer model of degenerative and developmental brain disorders

Heme oxygenase-1 (HO-1) is a 32 kDa protein which catalyzes the breakdown of heme to free iron, carbon monoxide and biliverdin. The Hmox1 promoter contains numerous consensus sequences that render the gene exquisitely sensitive to induction by diverse pro-oxidant and inflammatory stimuli. In “stressed” astroglia, HO-1 hyperactivity promotes mitochondrial iron sequestration and macroautophagy and may thereby contribute to the pathological iron deposition and bioenergetic failure documented in Alzheimer disease, Parkinson disease and certain neurodevelopmental conditions. Glial HO-1 expression may also impact neuroplasticity and cell survival by modulating brain sterol metabolism and the proteasomal degradation of neurotoxic proteins. The glial HO-1 response may represent a pivotal transducer of noxious environmental and endogenous stressors into patterns of neural damage and repair characteristic of many human degenerative and developmental CNS disorders.

Erythropoietin Attenuates Pulmonary Vascular Remodeling in Experimental Pulmonary Arterial Hypertension through Interplay between Endothelial Progenitor Cells and Heme Oxygenase

BACKGROUND

Pulmonary arterial hypertension (PAH) is a pulmonary vascular disease with a high mortality, characterized by typical angio-proliferative lesions. Erythropoietin (EPO) attenuates pulmonary vascular remodeling in PAH. We postulated that EPO acts through mobilization of endothelial progenitor cells (EPCs) and activation of the cytoprotective enzyme heme oxygenase-1 (HO-1).

METHODS

Rats with flow-associated PAH, resembling pediatric PAH, were treated with HO-1 inducer EPO in the presence or absence of the selective HO-activity inhibitor tin-mesoporphyrin (SnMP). HO activity, circulating EPCs and pulmonary vascular lesions were assessed after 3 weeks.

RESULTS

In PAH rats, circulating EPCs were decreased and HO activity was increased compared to control. EPO treatment restored circulating EPCs and improved pulmonary vascular remodeling, as shown by a reduced wall thickness and occlusion rate of the intra-acinar vessels. Inhibition of HO activity with SnMP aggravated PAH. Moreover, SnMP treatment abrogated EPO-induced amelioration of pulmonary vascular remodeling, while surprisingly further increasing circulating EPCs as compared with EPO alone.

CONCLUSION

In experimental PAH, EPO treatment restored the number of circulating EPCs to control level, improved pulmonary vascular remodeling, and showed important interplay with HO activity. Inhibition of increased HO activity in PAH rats exacerbated progression of pulmonary vascular remodeling, despite the presence of restored number of circulating EPCs. We suggest that both EPO-induced HO-1 and EPCs are promising targets to ameliorate the pulmonary vasculature in PAH.

Unregulated brain iron deposition in transgenic mice over-expressing HMOX1 in the astrocytic compartment

The mechanisms responsible for pathological iron deposition in the aging and degenerating mammalian CNS remain poorly understood. The stress protein, HO-1 mediates the degradation of cellular heme to biliverdin/bilirubin, free iron, and CO and is up-regulated in the brains of persons with Alzheimer's disease and Parkinson's disease. HO-1 induction in primary astroglial cultures promotes deposition of non-transferrin iron, mitochondrial damage and macroautophagy, and predisposes cocultured neuronal elements to oxidative injury. To gain a better appreciation of the role of glial HO-1 in vivo, we probed for aberrant brain iron deposition using Perls' method and dynamic secondary ion mass spectrometry in novel, conditional GFAP.HMOX1 transgenic mice that selectively over-express human HO-1 in the astrocytic compartment. At 48 weeks, the GFAP.HMOX1 mice exhibited increased deposits of glial iron in hippocampus and other subcortical regions without overt changes in iron-regulatory and iron-binding proteins relative to age-matched wild-type animals. Dynamic secondary ion mass spectrometry revealed abundant FeO⁻ signals in the transgenic, but not wild-type, mouse brain that colocalized to degenerate mitochondria and osmiophilic cytoplasmic inclusions (macroautophagy) documented by TEM. Sustained up-regulation of HO-1 in astrocytes promotes pathological brain iron deposition and oxidative mitochondrial damage characteristic of Alzheimer's disease-affected neural tissues. Curtailment of glial HO-1 hyperactivity may limit iron-mediated cytotoxicity in aging and degenerating neural tissues.

Successful plasmapheresis for acute and severe unconjugated hyperbilirubinemia in a child with crigler najjar type I syndrome

Crigler-Najjar syndrome type I (CN-I, MIM #218800) is a rare and severe autosomal disorder. It is caused by deficiency of the liver enzyme responsible for bilirubin elimination, the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1; EC 2.4.1.17). Biologically, the disease manifests itself with severe and persistent unconjugated hyperbilirubinemia. Kernicterus is a well-known complication of severe unconjugated hyperbilirubinemia in infants and young children, especially in patients with CN-I.Few articles have shown the efficiency of plasmapheresis for extreme hyperbilirubinemia.In this report, we describe the efficiency of plasmapheresis for a rapid control of acute and severe unconjugated hyperbilirubinemia in a 6-year-old CN-I patient who had previously developed kernicterus in the neonatal period. In spite of intensification of phototherapy, the patient developed severe hyperbilirubinemia (up to 830 μmol/l, with bilirubin/albumin ratio at 1.2). With two plasmapheresis procedures, bilirubin serum concentration decreased to 420 μmol/ and bilirubin/albumin ratio to 0.55. Following the acute episode of very severe unconjugated hyperbilirubinemia, the child recovered and neurological examination was unchanged, thus suggesting that plasmapheresis possibly prevented further worsening of kernicterus.

Assessment of UGT polymorphisms and neonatal jaundice

Elevation of the serum bilirubin level is a common, if not universal, finding during the first week of life. This can be a transient phenomenon that resolves spontaneously or can signify a serious or even life-threatening condition. There are many causes of hyperbilirubinemia and related therapeutic and prognostic implications. The diseases in which there is a primary disorder of the metabolism of bilirubin will be reviewed regarding their clinical presentation, pathophysiology, diagnosis, and treatment. These disorders-Gilbert's syndrome and Crigler-Najjar Syndrome-both involve abnormalities in bilirubin conjugation secondary to deficiency of bilirubin uridine diphosphate glucuronosyltransferase. The purpose of this article is to review the current understanding of the genetic polymorphisms that result in these diseases and discuss recent advances in diagnosis and treatment.

Bilirubin in clinical practice: a review

Bilirubin is an endogenous compound that can be toxic under certain conditions but, on the other hand, mild unconjugated hyperbilirubinaemia might protect against cardiovascular diseases and tumour development. Serum bilirubin levels are often enhanced under a variety of clinical conditions. These are discussed and the mechanisms are outlined.

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.

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.