Neuregulin-1 attenuates experimental cerebral malaria (ECM) pathogenesis by regulating ErbB4/AKT/STAT3 signaling.

BACKGROUND: Human cerebral malaria (HCM) is a severe form of malaria characterized by sequestration of infected erythrocytes (IRBCs) in brain microvessels, increased levels of circulating free heme and pro-inflammatory cytokines and chemokines, brain swelling, vascular dysfunction, coma, and increased mortality. Neuregulin-1ß (NRG-1) encoded by the gene NRG1, is a member of a family of polypeptide growth factors required for normal development of the nervous system and the heart. Utilizing an experimental cerebral malaria (ECM) model (Plasmodium berghei ANKA in C57BL/6), we reported that NRG-1 played a cytoprotective role in ECM and that circulating levels were inversely correlated with ECM severity. Intravenous infusion of NRG-1 reduced ECM mortality in mice by promoting a robust anti-inflammatory response coupled with reduction in accumulation of IRBCs in microvessels and reduced tissue damage. METHODS: In the current study, we examined how NRG-1 treatment attenuates pathogenesis and mortality associated with ECM. We examined whether NRG-1 protects against CXCL10- and heme-induced apoptosis using human brain microvascular endothelial (hCMEC/D3) cells and M059K neuroglial cells. hCMEC/D3 cells grown in a monolayer and a co-culture system with 30 µM heme and NRG-1 (100 ng/ml) were used to examine the role of NRG-1 on blood brain barrier (BBB) integrity. Using the in vivo ECM model, we examined whether the reduction of mortality was associated with the activation of ErbB4 and AKT and inactivation of STAT3 signaling pathways. For data analysis, unpaired t test or one-way ANOVA with Dunnett's or Bonferroni's post test was applied. RESULTS: We determined that NRG-1 protects against cell death/apoptosis of human brain microvascular endothelial cells and neroglial cells, the two major components of BBB. NRG-1 treatment improved heme-induced disruption of the in vitro BBB model consisting of hCMEC/D3 and human M059K cells. In the ECM murine model, NRG-1 treatment stimulated ErbB4 phosphorylation (pErbB4) followed by activation of AKT and inactivation of STAT3, which attenuated ECM mortality. CONCLUSIONS: Our results indicate a potential pathway by which NRG-1 treatment maintains BBB integrity in vitro, attenuates ECM-induced tissue injury, and reduces mortality. Furthermore, we postulate that augmenting NRG-1 during ECM therapy may be an effective adjunctive therapy to reduce CNS tissue injury and potentially increase the effectiveness of current anti-malaria therapy against human cerebral malaria (HCM).

Effects of Iron Supplements on Heme Scavengers in Pregnancy.

In malaria endemic countries, anemia in pregnant women occurs as a result of erythrocyte destruction by Plasmodium infections and other causes including malnutrition. Iron supplementation is recommended as treatment of iron-deficiency anemia. Erythrocyte destruction results in increased release of cytotoxic free heme that is scavenged by haptoglobin (Hp), hemopexin (Hx) and heme oxygenase-1 (HO-1). Paradoxically, iron supplementation in pregnant women has been reported to enhance parasitemia and increase levels of free heme. The relationship between free heme, heme scavengers, and birth outcomes has not been investigated, especially in women who are on iron supplementation. We hypothesized that parasite-infected pregnant women on routine iron supplementation have elevated heme and altered expression of heme scavengers. A cross-sectional study was conducted to determine the association between plasma levels of free heme, HO-1, Hp, Hx, and malaria status in pregnant women who received routine iron supplementation and their birth outcomes. Heme was quantified by colorimetric assay and scavenger protein concentration by ELISA. We demonstrated that iron-supplemented women with asymptomatic parasitemia had increased free heme (mean 75.6 µM; interquartile range [IQR] 38.8-96.5) compared with nonmalaria iron-supplemented women (mean 34.9 µM; IQR 17.4-43.8, P < 0.0001). Women with preterm delivery had lower levels of Hx (mean 656.0 µg/mL; IQR 410.9-861.3) compared with women with full-term delivery (mean: 860.9 µg/mL; IQR 715.2-1055.8, P = 0.0388). Our results indicate that iron supplementation without assessment of circulating levels of free heme and heme scavengers may increase the risk for adverse pregnancy outcomes.

Association of EPCR Polymorphism rs867186-GG With Severity of Human Malaria.

BACKGROUND: Cerebral malaria (CM) is characterized by the sequestration of Plasmodium-infected erythrocytes (pRBCs) to host brain microvasculature beds via P. falciparum erythrocyte membrane protein 1 (PfEMP1). Under normal conditions, activated protein C (APC) bound to endothelial protein C receptor (EPCR) has cytoprotective properties via the activation of protease-activated receptor 1 (PAR1). During malaria infection, pRBCs transports PfEMP1 to the membranes to bind EPCR in the same region as APC. As a result, APC is less capable of inducing cytoprotective effects via PAR1. Two studies involving adult malaria patients revealed that EPCR rs867186-GG allele is associated with protection against severe malaria, while three other studies involving child malaria patients could not show association between EPCR rs867186-GG genotype and severe malaria or increased mortality among children with CM. METHODS: We examined the association between the EPCR rs867186-GG genotype and the protection against cerebral malaria. Peripheral blood samples were collected from 47 malaria patients and 34 healthy individuals from a study conducted from 2004 to 2007 at the NSCB Medical College Hospital in India. CM and malaria-associated complications were defined based on WHO criteria. Genomic DNA was isolated from the peripheral blood mononuclear cells. Primer sequences were designed to contain rs867186 of the PROCR gene (NM 006404) and were used to amplify a 660 bp product as described before. PCR products were purified, and DNA sequences were determined by Sanger Sequencing (Genewiz, NJ). Nonparametric tests were used to compare the groups. To analyze differences in allele frequencies, we used chi-squared or Fisher's exact tests for categorical variables if the expected values were less than 5. P-value <0.05 was considered statistically significant. RESULTS: Our results showed significantly higher rates of AG and GG genotypes in CM patients compared to mild malaria (P = 0.0034). CONCLUSION: Our results indicate that rs867186-GG or rs867186-AG genotypes are not associated with protection against HCM.

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.

Aneurisma de ventrículo esquerdo associado à comunicaçäo interventricular pós-infarto / Aneurysm of left ventricle associated with post-infarction interventricular communication

Dois homens sexagenários apresentaram aneurisma do ventrículo esquerdo associado a comunicaçäo interventricular (CIV), na evoluçäo de infarto do miocárdio anterior extenso e ínfero-anterior. Os pacientes foram submetidos com sucesso a aneurismectomia ventricular esquerda, a revascularizaçäo do miocárdio e a fechamento da CIV