Nrf2 activation in myeloid cells and endothelial cells differentially mitigates sickle cell disease pathology in mice

Abstract

Sickle cell disease (SCD) is caused by a monogenic mutation of the β-globin gene and affects millions of people worldwide. SCD is associated with sustained hemolytic anemia, vasoocclusion, ischemia-reperfusion injury, oxidative tissue damage, inflammatory cell activation, and systemic endothelial dysfunction. The transcription factor Nrf2 coordinates the expression of a wide variety of genes encoding antioxidant, detoxification, and metabolic enzymes. Nrf2 participates in suppressing proinflammatory cytokines and organ protection in SCD. However, little is known regarding the mechanisms by which Nrf2 ameliorates SCD pathology or how some cells respond to Nrf2 stimuli to alleviate SCD pathology. Here, we asked whether monocytes/granulocytes and/or endothelial cells are particularly critical in alleviating the pathology of SCD. By targeting these cells with a Cre recombinase system, we generated SCD::Keap1F/F::LysM-Cre and Tie1-Cre mice with constitutive Nrf2 activation in monocytes/granulocytes and endothelial cells, respectively. Analyses of SCD::Keap1F/F::LysM-Cre and SCD::Keap1F/F::Tie1-Cre mice revealed significantly reduced inflammation, along with decreased white blood cell counts and lower Tnfα and Il1β expression in the lungs. Notably, SCD::Keap1F/F::LysM-Cre mice exhibited reduced heme distribution in the liver, consistent with a decrease in the damaged areas. Vascular function in SCD::Keap1F/F::Tie1-Cre mice was significantly improved, with a 50% decrease in vascular leakage and low expression of the adhesion molecules Vcam1 and P-selectin. Thus, Nrf2 activation in monocytes/granulocytes and endothelial cells contributes differentially and cooperatively to the improvement of SCD pathology.

Mitochondrial Reactive Oxygen Species Participate in Signaling Triggered by Heme in Macrophages and upon Hemolysis

“…Constitutive expression of NRF2 or treatment with an activator of NRF2, which is important for antioxidant responses, have a protective effect in mouse models of sickle cell disease-reducing cytokine production and vaso-occlusive episodes (28,29). The selective activation of NRF2 in myeloid cells and endothelial cells contributes to the protection against the tissue damage caused by hemolysis in sickle cell disease, through several complementary mechanisms (30). Induction of heme oxygenase-1 (HO-1) also mitigates the inflammatory response and vascular stasis in sickle cell disease-transgenic mouse models indicating the contribution of heme and ROS to tissue damage caused by hemolysis (31).…”

Loss of PKA regulatory subunit 1α aggravates cardiomyocyte necrosis and myocardial ischemia/reperfusion injury

“…In addition, ablation of Nrf2 aggravates pressure-overload-induced myocardial necrosis ( 32 ), whereas overexpression of Nrf2 prevents puromycin-induced necrosis in adult cardiomyocytes ( 33 ). Nrf2 activation also mitigates liver necrosis in a mouse model of hepatic I/R or sickle cell disease ( 34 , 35 ). Interestingly, Nrf2 appears to suppress necrosis without altering apoptosis ( 33 , 34 ).…”

Multifaceted Roles of the KEAP1–NRF2 System in Cancer and Inflammatory Disease Milieu

“…A key question remained, is systemic NRF2 activation important for NRF2-mediated attenuation of SCD pathology, or is it vital only in certain crucial cell lineages? To answer this question, a study with sickle murine model mice in which KEAP1 was specifically deleted in myeloid lineage cells (SCD::Keap1 F/F ::LysM-Cre) or endothelial cells (SCD::Keap1 F/F ::Tie1-Cre) has been carried out [103]. Among the many other cells that might participate in SCD pathology, endothelial cells, and myeloid lineage cells were selected for evaluation because they reside in proximal to areas with ischemic/reperfusion injury and heme metabolism, respectively.…”