Erythrocyte plasma membrane–bound ERK1/2 activation promotes ICAM-4–mediated sickle red cell adhesion to endothelium

Abstract

IntroductionSickle (homozygous hemoglobin S, SS) RBC-based adhesion and vaso-occlusive events likely initiate and/or exacerbate the profound vasculopathy present in patients with sickle cell disease (SCD). 1,2 SS RBCs possess unusually active signaling pathways that contribute to a panoply of abnormalities, including RBC adhesion to the endothelium and vaso-occlusion. [2][3][4] Cell adhesion is a multistep cellular process that is regulated by complex extracellular and intracellular signals that may differ from one cell type to another. We have previously shown that abnormal SS RBC interaction with the endothelium and with leukocytes can be induced via ␤ 2 adrenergic receptor (␤ 2 AR) activation by the stress hormone epinephrine. [4][5][6] Such stimulation activates the intracellular cAMP/protein kinase A (PKA) pathway. 4 ␤ 2 ARs are prototypic G-coupled receptors whose signaling properties are in part mediated by the activation of stimulatory GTP-binding proteins (G s proteins), which in turn activate adenylate cyclase (AC), leading to the generation of cAMP and the subsequent activation of PKA. The cAMP/PKA pathway can modulate the MAPK/ERKs cascade both directly and indirectly. 7-9 PKA has been reported to stimulate B-Raf, while inhibiting c-Raf. Therefore, the activity of downstream signaling proteins, such as MEKs and ERKs, could be either enhanced or inhibited depending on the balance of c-Raf and B-Raf activation. 10,11 The cellular functions mediated by ␤ 2 ARs can also be independent of adenylyl cyclase activation and involve other mediators instead. [12][13][14][15] The functions attributed to ERK1/2 at both the cellular and physiologic levels are diverse, including modulation of proliferation, differentiation, apoptosis, migration, and cell adhesion. [16][17][18][19] Physiologically, ERK1/2 is required for immune system development, homeostasis and antigen activation, memory formation, development of the heart, and responses to many hormones, growth factors, and insulin. Most of these previous studies have involved only nucleated cells, including erythroid cells, in which erythropoietin is the primary regulatory cytokine of this pathway. 20 However, aberrations in ERK1/2 signaling are known to occur in a wide range of pathologies, including cancer, diabetes, viral infection, and cardiovascular disease. 21,22 In preliminary studies, authors have indicated that ERK1/2 is highly abundant in both SS and normal RBCs. Yet, whether this kinase remains functional in normal or SS RBCs is unknown, and an extremely critical question in the study of SCD pathophysiology. Such a mechanism of action could represent a novel target for the treatment of SCD. Methods Endothelial cellsPrimary HUVECs were grown as monolayers in EBM2 medium (Lonza Walkersville) supplemented with EGM2 (Lonza Walkersville) as described previously. 4 All experiments were approved by the Duke University institutional review board. AntibodiesAbs used included the following monoclonal and polyclonal Abs (as purified Ig unless otherwise noted): B...

Acid sphingomyelinase is activated in sickle cell erythrocytes and contributes to inflammatory microparticle generation in SCD

“…Additionally, we show that SS MPs, and not AA MPs, enhance monocyte adhesion to endothelial cells ( Figure 6A), and similarly, co-incubation of monocytes with SS RBCs enhances monocyte-endothelial adhesion relative to AA RBCs ( Figure 5C). Zennadi et al established an ERK1/2-mediated mechanism for ICAM-4 activation on SS RBCs, which mediates monocyte adhesion and activation 26,27 ; therefore, For personal use only. on June 7, 2019.…”

“…Zennadi et al established an ERK1/2-mediated mechanism for ICAM-4 activation on SS RBCs, which mediates RBC adhesion to both monocytes and endothelial cells. 26,27 Both AA and SS RBC-derived MPs expressed ICAM-4 ( Figure 6B). SS RBC-derived MPs, however, expressed significantly activated ERK1/2 as indicated by significantly higher p-ERK1/2 to total ERK1/2 than AA RBC-derived MPs (Figure 6C-D).…”

Randomized phase 2 study of GMI-1070 in SCD: reduction in time to resolution of vaso-occlusive events and decreased opioid use

“…[7][8][9][10][11][12][13][14] Binding of both red cells and leukocytes to endothelial selectins has been proposed to have a critical role in SCD VOC. 13,[15][16][17] Endothelial E-selectin expression is upregulated by inflammatory cytokines and can become a target, along with P-selectin, for leukocyte adhesion.…”

Molecular mechanisms underlying synergistic adhesion of sickle red blood cells by hypoxia and low nitric oxide bioavailability

“…Recently, extracellular signal-regulated kinases were shown to participate in sRBC adhesion to endothelial cells. 40 Thus, the activation of MAPK pathways likely enhances sRBC adhesion to endothelial cells, which in turn may lead to the initiation of vasoocclusion. Caution should be taken when deciding whether the benefits of fetal hemoglobin induction through the activation of MAPK pathways outweigh the risks for enhanced sRBC adhesion that may elicit vaso-occlusion.…”