Hydroxyurea Improves Mesenteric Blood Flow and Reduces Gut Permeability in Sickle Cell Disease Mice

Activated leukocytes and polymorphonuclear neutrophils (PMN) release myeloperoxidase (MPO), which binds to endothelial cells (EC), is translocated, and generates oxidants that scavenge nitric oxide (NO) and impair EC function. To determine whether MPO impairs EC function in sickle cell disease (SCD), control (AA) and SCD mice were treated with N-acetyl-lysyltyrosylcysteine-amide (KYC). SCD humans and mice have high plasma MPO and soluble L-selectin (sL-selectin). KYC had no effect on MPO but decreased plasma sL-selectin and malondialdehyde in SCD mice. MPO and 3-chlorotyrosine (3-ClTyr) were increased in SCD aortas. KYC decreased MPO and 3-ClTyr in SCD aortas to the levels in AA aortas. Vasodilatation in SCD mice was impaired. KYC increased vasodilatation in SCD mice more than 2-fold, to ∼60% of levels in AA mice. KYC inhibited MPO-dependent 3-ClTyr formation in EC proteins. SCD mice had high plasma alanine transaminase (ALT), which tended to decrease in KYC-treated SCD mice (P = 0.07). KYC increased MPO and XO/XDH and decreased 3-ClTyr and 3-nitrotyrosine (3-NO₂Tyr) in SCD livers. These data support the hypothesis that SCD increases release of MPO, which generates oxidants that impair EC function and injure livers. Inhibiting MPO is an effective strategy for decreasing oxidative stress and liver injury and restoring EC function in SCD.

Upregulation of Renal Iron Metabolism in Sickle Cell Disease Mice

Dietary Iron Restriction Alters Microbiota-Host Crosstalk and Protects Against Vaso-Occlusion and Organ Damage in Sickle Cell Disease Mice

Protection of Microvascular Liver Perfusion with 5-Hydroxymethylfurfural in Sickle Cell Disease Mice Following Hypoxia-Induced Vasoocclusion

Metabolic and Hematological Changes Following Traumatic Brain Injury in Sickle Cell Mice

Purpose: Sickle cell disease (SCD) is the most commonly inherited monogenic hemoglobinopathy and results from a mutation in the β-globin gene (HbS), leading to red blood cell (RBC) sickling, vaso-occlusive episodes (VOE), and organ damage. Chronic hemolysis, inflammation, and repeated red blood cell transfusions in SCD can disrupt iron homeostasis. Patients who receive multiple blood transfusions develop iron-overload, and another subpopulation of SCD patients manifest iron deficiency. SCD mice exhibit increased iron absorption via upregulation of the intestinal transcription factor hypoxia inducible factor-2a(HIF-2a) leading to the development of iron overload. Disruption of intestinal HIF-2a or limiting iron intake by dietary iron restriction in SCD mice, significantly reduced systemic iron overload, lowered cellular sickle hemoglobin as reflected by reduced RBC mean corpuscular hemoglobin concentration (MCHC), and consequently improved hemolysis and ameliorated anemia. Understanding iron homeostasis is therefore critical to SCD pathogenesis and holds the promise for identifying novel approaches to treat SCD. Materials and methods: SCD mice were generated by transplanting bone marrow cells from Berkeley SCD (Tg[Hu-miniLCRα1GγAγδβS]Hba−/− Hbb−/−) mice into 8-week old, lethally-irradiated C57BL/6J mice. Immediately after transplantation, SCD mice were fed either a regular-iron diet (Ctrl) containing 185 parts per million (ppm) iron or an otherwise identical iron-restricted diet (IRD) containing 3 ppm iron. VOE and organ damage analysis were done 3-4 months after treatments. Results: IRD resulted in a reduced organ iron concentration (Fig-1A) in SCD compared to Ctrl group, confirming that dietary iron restriction ameliorates organ iron deposition in SCD mice. SCD mice treated with IRD exhibited reduced MCHC (Fig-1B) and serum indirect bilirubin(IDBILC) (Fig-1C) indicating a decrease in cellular sickle hemoglobin and hemolysis. Furthermore, IRD reduced the fraction of aged neutrophils by >50% in SCD mice (Fig-1D), which corresponded with improved VOE parameters. Specifically, intravital microscopy (IVM) demonstrated elevated mean centerline RBC velocity and blood flow rate and decreased leukocyte adhesion in IRD compared to Ctrl mice (Fig-1E-G). Importantly, IRD led to prolonged survival after TNF-a challenge in SCD mice (Fig-1H). IRD resulted in a dramatic reduction in lung leukocyte infiltration, indicating significantly reduced lung inflammation in SCD mice (Fig-2A). Compared to Ctrl liver samples, IRD resulted in significantly less liver necrosis, leukocyte infiltration and fibrosis (Fig-2B,C), decreased serum liver enzymes (ALT, AST; Fig-2D), and reduced levels of total and direct bilirubin (TBILC, DBILC; Fig-2D).We further hypothesized that, in addition to reducing iron concentration in organs, IRD ameliorates organ damage by preventing translocation of microbial compounds.IRD inhibits translocation of FITC-Dextran by 5-fold compared to Ctrl suggesting functionally improved gut permeability (Fig-2E). We detected significantly decreased TLR2 ligands in serum of IRD mice (Fig-2F) suggesting ligands from gram-positive bacteria (TLR2 agonists) may play a role in triggering SCD complications. Conclusion: Our study demonstrates for the first time that dietary iron restriction reduces VOE severity and alleviates chronic organ damage in SCD mice. Novel approaches that target iron availability/absorption in the gut, the gut microbiome and aged neutrophil crosstalk and gut barrier integrity, provide an important area of further investigation with the potential of improving hemolysis, VOE, and organ damage in SCD patients.(A)The bone-marrow/spleen/liver Non-heme iron content. (B)MCHC, (C)IDBILC,(D)aged neutrophils percentage in Ctrl/IRD SCD mice. IVM parameters (E) (Vrbc) (F) blood flow rate (J) the number of adherent leukocytes and (J) survival rate after TNF-a injection(A)Leukocyte infiltration in lung and (B)liver tissue. (C)Liver necrosis, leukocyte infiltration, and fibrosis. (D)Liver ALT and AST, TBILC, and DBILC from sera. (E)serum FITC-Dextran and (F) TLR2 ligands activity in Ctrl/IRD SCD mice The authors do not declare any conflict of interest

A Novel Hemoglobin-Binding Agent Reduces Plasma Free Hemoglobin and Partially Improves Vascular Function In Murine Hemolytic Anemia

Hematopoietic Stem Cells from Mice and Individuals with Sickle Cell Disease Display Premature Senescence and Loss of Function That Is Targetable By Senolytic Therapy

The Effect of the Soluble Guanylate Cyclase Stimulator Olinciguat on Renal Function and Biomarkers of Inflammation and Renal Injury in Sickle Cell Mice

A Novel Selectin Antagonist, GMI-1070, Prevents Vaso-Occlusion in Sickle Cell Mice by Inhibiting Leukocyte Adhesion and Activation.

Flu Induced Acute Chest Syndrome in Sickle Cell Disease Mice

Sodium-glucose co-transporter 2 inhibitors are widely used to treat patients with type 2 diabetes and exhibit beneficial cardiovascular effects beyond glucose lowering. In this study, we investigated their potential to alleviate vaso-occlusive events and organ damage in sickle cell disease (SCD) mice. Intravital and immunofluorescence microscopy reveal that 4-day oral administration of dapagliflozin (DAPA) or sotagliflozin (SOTA) significantly reduces neutrophil adhesion and transmigration in cremaster venules, with SOTA showing greater inhibition, and downregulates E-selectin and intercellular adhesion molecule-1 (ICAM-1) expression in cremaster venules of TNF-α-challenged SCD mice. Intriguingly, only SOTA improves mouse survival acutely. Similar inhibitory effects on neutrophil recruitment are observed in SCD mice subjected to hypoxia-reoxygenation. Flow chamber assays indicate that neither drug directly affects neutrophil or endothelial cell adhesive function. In addition, treatment of neutrophils and platelets from SCD mice and patients with DAPA or SOTA does not affect their activation. When administered for 4 months, DAPA or SOTA mitigates neutrophil recruitment and enhances microcirculation in cremaster venules of TNF-α-challenged SCD mice, while only SOTA confers a survival benefit. Both drugs reduce leukocyte infiltration in the liver or lungs, suggesting their ability to protect against organ damage. Co-administration with hydroxyurea for 4 months does not enhance these effects. Multiplex analysis shows that DAPA and SOTA lower plasma levels of soluble P-selectin, ICAM-1, S100A8/A9, and pro-inflammatory cytokines in SCD mice. Our findings suggest that DAPA and SOTA mitigate vaso-occlusive events in SCD, with SOTA providing superior benefits. Sickle cell disease (SCD) is an inherited autosomal recessive disorder characterized by red blood cell hymolysis, oxidative stress, and chronic inflammation. Recurrent vaso-occlusive crises driven by intravascular cell-cell adhesion and aggregation and the hallmark of SCD. In this study, we show that dapagliflozing (DAPA), a sodium-glucose co-transporter 2 inhibitor (SGLT2i), and sotagliflozin (SOTA), an SGLT1/2i, reduce acute vaso-occlusion in SCD mice subjected to severe inflammation or hypoxia-reoxygenation, with SOTA providing greater benefit.These findings suggest that SGLT2 or SGLT1/2 inhibition may help attenuate vaso-occlusive pain crises in SCD patients.

Mildronate Ameliorates Kidney Function and Reduces Inflammation in SCD Mice

Platelet-Neutrophil Aggregates Promote Pulmonary Arteriole Microembolism in Sickle Cell Disease

Berkeley Sickle Cell Disease Mice Exhibit Multifaceted Immune Hyper-Activation, and Avidly Reject Allogeneic Bone Marrow Transplantation.