Effects of light on metalloporphyrin-treated newborn mice

Is it time for a precision health approach to the management of newborn hyperbilirubinemia?

Newborn hyperbilirubinemia during the first two weeks of life is one of most common problems requiring management decisions by a pediatrician. However, high bilirubin levels in the circulation have been associated with neurologic injury under a variety of conditions encountered in the newborn infant, such as hemolysis. The risk for developing dangerous hyperbilirubinemia is multifactorial and is determined by a complex set of factors related to a newborn infant's genetic capacities as well as intra- and extrauterine exposures. To this end, a precision health approach based on the integration of prenatal genetic and postnatal diagnostic measures might improve the management of neonatal hyperbilirubinemia.

Efficacy of zinc sulfate on indirect hyperbilirubinemia in premature infants admitted to neonatal intensive care unit: a double-blind, randomized clinical trial

Background

Hyperbilirubinemia is a common neonatal problem. Studies conducted on the effectiveness of zinc salts on serum indirect bilirubin levels in newborns have yielded different results, all calling for further research. This study aimed to determine the effect of oral zinc sulfate on indirect hyperbilirubinemia in preterm infants admitted to the neonatal intensive care unit.

Methods

A randomized double-blind clinical trial was performed in the neonatal intensive care unit of Vali-e-Asr Hospital in Birjand, Iran. The study population comprised neonates aged between 31 and 36 gestational weeks, who required phototherapy in the neonatal intensive care unit. A total of 60 neonates were selected by census and allocated into an experimental group and a control group. In addition to phototherapy, the experimental group received 1 cc/Kg zinc sulfate syrup (containing 5 mg/5 cc zinc sulfate; Merck Company, Germany), and the control group received a placebo syrup (containing 1 cc/kg sucrose). Data were analyzed in SPSS-21 software using the independent t-test, repeated-measures ANOVA, Bonferroni post-hoc test, and Mann-Whitney test. P-values smaller than 0.05 were considered significant.

Results

Bilirubin level changes in the experimental and control groups six hours after intervention were − 1.45 ± 3.23 and − 0.49 ± 0.37 (p = 0.024), respectively. The changes 24 and 48 h after intervention were-3.26 ± 2.78 and − 1.89 ± 1.20 (p = 0.017) in the experimental group and − 4.89 ± 2.76 and − 3.98 ± 2.32 (p = 0.23) in the control group, respectively. There was no significant difference in the phototherapy duration between the two groups (p = 0.24).

Conclusions

The results of this study showed that the use of zinc sulfate syrup in preterm infants with indirect hyperbilirubinemia significantly reduced bilirubin levels within 48 h of treatment.

Trial registration

Trial registration: IRCT, IRCT2015120825439N1. Registered 21 February 2016, http://irct.ir/trial/21277

Experimental models assessing bilirubin neurotoxicity

The molecular and cellular events leading to bilirubin-induced neurotoxicity, the mechanisms regulating liver and intestine expression in neonates, and alternative pathways of bilirubin catabolism remain incompletely defined. To answer these questions, researchers have developed a number of model systems to closely recapitulate the main characteristics of the disease, ranging from tissue cultures to engineered mouse models. In the present review we describe in vitro, ex vivo, and in vivo models developed to study bilirubin metabolism and neurotoxicity, with a special focus on the use of engineered animal models. In addition, we discussed the most recent studies related to potential therapeutic approaches to treat neonatal hyperbilirubinemia, ranging from anti-inflammatory drugs, activation of nuclear receptor pathways, blockade of bilirubin catabolism, and stimulation of alternative bilirubin-disposal pathways.

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.

The phototoxicity of vemurafenib: An investigation of clinical monochromator phototesting and in vitro phototoxicity testing

BACKGROUND

Vemurafenib is a targeted therapy approved for the treatment of patients with metastatic melanoma harbouring the BRAF V600E mutation. Photosensitivity has been reported in over 50% of patients and has been demonstrated to involve at least the broadband UVA spectrum in most patients. Erythrocyte protoporphyrin levels have also been reported as elevated in some patients.

OBJECTIVES

We report the results of monochromator phototesting in one patient recorded before and while taking vemurafenib. Analysis of porphyrin levels was also conducted.

RESULTS

After one month of vemurafenib therapy the patient demonstrated markedly increased light sensitivity in the UVA spectrum between 335 ± 27 nm, 365 ± 27 nm and 400 ± 27 nm. However responses in the UVB (305 ± 5 nm) and blue light (430 ± 27 nm) regions were normal. There was no abnormal immediate erythemal response. Pre-vemurafenib baseline phototesting was normal, as was repeat testing two months later when the patient was taking high doses of systemic steroid. No abnormal porphyrins were detected and the antinuclear antibody test was normal. In parallel studies, HaCaT keratinocytes incubated with vemurafenib were killed by UVA but not by visible (blue) light and did not show evidence of detectable intracellular porphyrin in the presence of the drug.

CONCLUSION

These data confirm vemurafenib induced UVA photosensitivity with a probable phototoxic mechanism not mediated via enhanced porphyrin.