Modulation of Heme-Induced Inflammation Using MicroRNA-Loaded Liposomes: Implications for Hemolytic Disorders Such as Malaria and Sickle Cell Disease.

Hemolytic disorders, like malaria and sickle cell disease (SCD), are responsible for significant mortality and morbidity rates globally, specifically in the Americas and Africa. In both malaria and SCD, red blood cell hemolysis leads to the release of a cytotoxic heme that triggers the expression of unique inflammatory profiles, which mediate the tissue damage and pathogenesis of both diseases. MicroRNAs (miRNAs), such as miR-451a and let-7i-5p, contribute to a reduction in the pro-inflammatory responses induced by circulating free hemes. MiR-451a targets both IL-6R (pro-inflammatory) and 14-3-3ζ (anti-inflammatory), and when this miRNA is present, IL-6R is reduced and 14-3-3ζ is increased. Let-7i-5p targets and reduces TLR4, which results in anti-inflammatory signaling. These gene targets regulate inflammation via NFκB regulation and increase anti-inflammatory signaling. Additionally, they indirectly regulate the expression of key heme scavengers, such as heme-oxygenase 1 (HO-1) (coded by the HMOX1 gene) and hemopexin, to decrease circulating cytotoxic heme concentration. MiRNAs can be transported within extracellular vesicles (EVs), such as exosomes, offering insights into the mechanisms of mitigating heme-induced inflammation. We tested the hypothesis that miR-451a- or let-7i-5p-loaded artificial EVs (liposomes) will reduce heme-induced inflammation in brain vascular endothelial cells (HBEC-5i, ATCC: CRL-3245) and macrophages (THP-1, ATCC: TIB-202) in vitro. We completed arginase and nitric oxide assays to determine anti- and pro-inflammatory macrophage presence, respectively. We also assessed the gene expression of IL-6R, TLR4, 14-3-3ζ, and NFκB by RT-qPCR for both cell lines. Our findings revealed that the exposure of HBEC-5i and THP-1 to liposomes loaded with miR-451a or let-7i-5p led to a reduced mRNA expression of IL-6R, TLR4, 14-3-3ζ, and NFκB when treated with a heme. It also resulted in the increased expression of HMOX1 and hemopexin. Finally, macrophages exhibited a tendency toward adopting an anti-inflammatory differentiation phenotype. These findings suggest that miRNA-loaded liposomes can modulate heme-induced inflammation and can be used to target specific cellular pathways, mediating inflammation common to hematological conditions, like malaria and SCD.

Sickle Cell Hemoglobin Genotypes Affect Malaria Parasite Growth and Correlate with Exosomal miR-451a and let-7i-5p Levels.

Malaria affects a significant portion of the global population, with 247 million cases in 2021, primarily in Africa. However, certain hemoglobinopathies, such as sickle cell trait (SCT), have been linked to lower mortality rates in malaria patients. Hemoglobin (Hb) mutations, including HbS and HbC, can cause sickle cell disease (SCD) when both alleles are inherited (HbSS and HbSC). In SCT, one allele is inherited and paired with a normal allele (HbAS, HbAC). The high prevalence of these alleles in Africa may be attributed to their protective effect against malaria. Biomarkers are crucial for SCD and malaria diagnosis and prognosis. Studies indicate that miRNAs, specifically miR-451a and let-7i-5p, are differentially expressed in HbSS and HbAS compared to controls. Our research examined the levels of exosomal miR-451a and let-7i-5p in red blood cells (RBCs) and infected red blood cells (iRBCs) from multiple sickle Hb genotypes and their impact on parasite growth. We assessed exosomal miR-451a and let-7i-5p levels in vitro in RBC and iRBC supernatants. Exosomal miRNAs exhibited distinct expression patterns in iRBCs from individuals with different sickle Hb genotypes. Additionally, we discovered a correlation between let-7i-5p levels and trophozoite count. Exosomal miR-451a and let-7i-5p could modulate SCD and malaria severity and serve as potential biomarkers for malaria vaccines and therapies.

MicroRNAs miR-451a and Let-7i-5p Profiles in Circulating Exosomes Vary among Individuals with Different Sickle Hemoglobin Genotypes and Malaria.

Sickle cell disease (SCD) occurs when two alleles of mutated hemoglobin (HbS or HbC) are inherited (HbSS and HbSC) rather than one (HbAS or HbAC), which indicates a person carries the sickle cell trait. The high prevalence of these two alleles in Africa have been associated with reduced malaria susceptibility. Recent in vitro research has been shown that microRNAs (miRNAs) miR-451a and let-7i-5p are differentially expressed in HbSS erythrocytes compared to healthy controls (HbAA) and are overexpressed in Plasmodium-infected malaria erythrocytes. However, these miRNAs have not been fully examined in the plasma of people with different sickle hemoglobin genotypes. Plasma circulating miRNAs are commonly encapsulated in extracellular vesicles, such as exosomes, and are thought to play a role in disease development. Circulating exosomal miR-451a and let-7i-5p were quantified from individuals with various hemoglobin genotypes (HbAA, HbAS, HbAC, HbSS, HbSC, and HbCC) with (+) and without (-) malaria. The results showed a higher level of exosomal let-7i-5p and miR-451a in HbSS-. Exosomal let-7i-5p and miR-451a levels were lower in HbSS+ compared to other genotypes. Based on the area under the curve (AUC) of the Receiver Operating Characteristics (ROCs), both exosomal miRNAs may be useful disease biomarkers for SCD with malaria. Finally, miR-451a and let-7i-5p modulate genes involved in inflammation, making them potential biomarkers of pathogenesis for both diseases.

MiR-451a and let-7i-5p loaded extracellular vesicles attenuate heme-induced inflammation in hiPSC-derived endothelial cells.

Hemolysis is associated with many pathologies, including trauma, sepsis, hemorrhagic stroke, malaria, and genetic disorders such as sickle cell disease (SCD). When hemolysis occurs, free-heme drives vascular inflammation, resulting in oxidative tissue damage and cardiometabolic complications. A better understanding of heme clearance and detoxification is essential to preventing sustained tissue damage. Human induced pluripotent stem cell (hiPSC)-derived endothelial cells (hiPSC-ECs) provide a novel source of patient-specific cells and tissues for disease modeling, drug discovery, and regenerative therapeutics. Here we report the use of hiPSC-ECs to elucidate the role of miR-451a and let-7i-5p-loaded extracellular vesicles (EVs, such as exosomes) in the inflammatory response to free-heme as a model for heme-induced inflammation. We provide evidence of a significant correlation between miR-451a and let-7i-5p-loaded circulating exosomes in plasmodium-infected patients with reported clinical benchmarks of malaria-severity (e.g., Hemoglobin (Hb) levels, white blood cell counts). Additionally, we determined that exposure of Plasmodium falciparum (Pf) parasites to EVs, loaded with either miRNA, significantly reduces their counts in vitro. Using hiPSCs derived from individuals with wild-type Hb (HbAA) or homozygous sickle cell mutated Hb (HbSS) genotypes, we demonstrate that heme-treated hiPSC-ECs secreted inflammatory products (cytokines, chemokines and growth factors) into supporting media at concentrations that were similar to that reported in HbAA and HbSS serum. This inflammatory response was attenuated by exposure with miR-451a or let-7i-5p-loaded EVs. We also found a decrease in transcription of ICAM1 and P-Selectin, as well as the secretion of key inflammatory cytokines (e.g., CXCL10, TNF-α, and IFN-γ). Based on these findings, we propose a model in which increased levels of exosomal miR-451a and let-7i-5p in Plasmodium-infected individuals will attenuate inflammatory responses to free-heme and parasite-derived products. As a result, infected erythrocytes will less likely adhere to the endothelium, sequester in brain micro vessels, and reduce vaso-occlusive crises that exacerbate cerebral malaria.