Iron Supplementation Alters Heme and Heme Oxygenase 1 (HO-1) Levels In Pregnant Women in Ghana

Inhibition of Heme Oxygenase-1 by Zinc Protoporphyrin IX Improves Adverse Pregnancy Outcomes in Malaria During Early Gestation

The enzyme heme oxygenase-1 (HO-1) has cytoprotective effects by catalyzing the degradation of heme to produce carbon monoxide, iron and biliverdin. Furthermore, HO-1 activity has been associated with successful pregnancy. On the other hand, in the context of certain inflammatory conditions, HO-1 can induce iron overload and cell death. To investigate the role of HO-1 in gestational malaria, pregnant BALB/c mice were infected with Plasmodium berghei ANKA in early, mid and late gestation. We found that malaria affected the pregnancy outcome in the three periods evaluated. However, only poor pregnancy outcomes in early pregnancy were related to HO-1 upregulation, iron overload, lipid peroxidation and necrosis of the decidua, which were prevented by HO-1 inhibition. In conclusion, HO-1 expression must be finely tuned in gestational malaria to avoid the deleterious effect of increased enzyme activity.

A novel murine model for assessing fetal and birth outcomes following transgestational maternal malaria infection

Plasmodium falciparum infection during pregnancy is a major cause of severe maternal illness and neonatal mortality. Mouse models are important for the study of gestational malaria pathogenesis. When infected with Plasmodium chabaudi chabaudi AS in early gestation, several inbred mouse strains abort at midgestation. We report here that outbred Swiss Webster mice infected with P. chabaudi chabaudi AS in early gestation carry their pregnancies to term despite high parasite burden and malarial hemozoin accumulation in the placenta at midgestation, with the latter associated with induction of heme oxygenase 1 expression. Infection yields reduced fetal weight and viability at term and a reduction in pup number at weaning, but does not influence postnatal growth prior to weaning. This novel model allows for the exploration of malaria infection throughout pregnancy, modeling chronic infections observed in pregnant women prior to the birth of underweight infants and enabling the production of progeny exposed to malaria in utero, which is critical for understanding the postnatal repercussions of gestational malaria. The use of outbred mice allows for the exploration of gestational malaria in a genetically diverse model system, better recapitulating the diversity of infection responses observed in human populations.

Modelling heme-mediated brain injury associated with cerebral malaria in human brain cortical organoids

Human cerebral malaria (HCM), a severe encephalopathy associated with Plasmodium falciparum infection, has a 20-30% mortality rate and predominantly affects African children. The mechanisms mediating HCM-associated brain injury are difficult to study in human subjects, highlighting the urgent need for non-invasive ex vivo human models. HCM elevates the systemic levels of free heme, which damages the blood-brain barrier and neurons in distinct regions of the brain. We determined the effects of heme on induced pluripotent stem cells (iPSCs) and a three-dimensional cortical organoid system and assessed apoptosis and differentiation. We evaluated biomarkers associated with heme-induced brain injury, including a pro-inflammatory chemokine, CXCL-10, and its receptor, CXCR3, brain-derived neurotrophic factor (BDNF) and a receptor tyrosine-protein kinase, ERBB4, in the organoids. We then tested the neuroprotective effect of neuregulin-1 (NRG-1) against heme treatment in organoids. Neural stem and mature cells differentially expressed CXCL-10, CXCR3, BDNF and ERBB4 in the developing organoids and in response to heme-induced neuronal injury. The organoids underwent apoptosis and structural changes that were attenuated by NRG-1. Thus, cortical organoids can be used to model heme-induced cortical brain injury associated with HCM pathogenesis as well as for testing agents that reduce brain injury and neurological sequelae.