Mechanisms of Impaired Neutrophil Migration by MicroRNAs in Myelodysplastic Syndromes

Abstract

In myelodysplastic syndromes (MDS), functional defects of neutrophils result in high mortality because of infections; however, the molecular basis remains unclear. We recently found that miR-34a and miR-155 were significantly increased in MDS neutrophils. To clarify the effects of the aberrant microRNA expression on neutrophil functions, we introduced miR-34a, miR-155, or control microRNA into neutrophil-like differentiated HL60 cells. Ectopically introduced miR-34a and miR-155 significantly attenuated migration toward chemoattractants fMLF and IL-8, but enhanced degranulation. To clarify the mechanisms for inhibition of migration, we studied the effects of miR-34a and miR-155 on the migration-regulating Rho family members, Cdc42 and Rac1. The introduced miR-34a and miR-155 decreased the fMLF-induced active form of Cdc42 to 29.0 ± 15.9 and 39.7 ± 4.8% of that in the control cells, respectively, although Cdc42 protein levels were not altered. miR-34a decreased a Cdc42-specific guanine nucleotide exchange factor (GEF), dedicator of cytokinesis (DOCK) 8, whereas miR-155 reduced another Cdc42-specific GEF, FYVE, RhoGEF, and PH domain-containing (FGD) 4. The knockdown of DOCK8 and FGD4 by small interfering RNA suppressed Cdc42 activation and fMLF/IL-8-induced migration. miR-155, but not miR-34a, decreased Rac1 protein, and introduction of Rac1 small interfering RNA attenuated Rac1 activation and migration. Neutrophils from patients showed significant attenuation in migration compared with healthy cells, and protein levels of DOCK8, FGD4, and Rac1 were well correlated with migration toward fMLF ( = 0.642, 0.686, and 0.436, respectively) and IL-8 ( = 0.778, 0.659, and 0.606, respectively). Our results indicated that reduction of DOCK8, FGD4, and Rac1 contributes to impaired neutrophil migration in MDS.

Rac‐GTPases and Rac‐GEFs in neutrophil adhesion, migration and recruitment

“…In contrast to Rac2, no Rac1 mutation is known to cause human immunodeficiency. Interestingly, reduced levels of Rac1 (and other Rho‐GTPases and their regulators) were recently linked to the upregulation of microRNAs in human myelodysplastic syndrome, a condition characterized by a range of functional neutrophil defects . However, more study is required to establish causal relationships and specificity.…”

“…Interestingly, reduced levels of Rac1 (and other Rho-GTPases and their regulators) were recently linked to the upregulation of micro-RNAs in human myelodysplastic syndrome, a condition characterized by a range of functional neutrophil defects. 44 However, more study is required to establish causal relationships and specificity. Deleting Rac1 in the mouse is embryonic lethal, but drug-inducible conditional Rac1-deficiency is known to increase the integrin-mediated spreading of neutrophils derived from hematopoietic stem cells.…”

1-Palmitoyl-2-Linoleoyl-3-Acetyl-rac-Glycerol (PLAG) Mitigates Monosodium Urate (MSU)-Induced Acute Gouty Inflammation in BALB/c Mice

“…HL-60 (ATCC) cells were cultured in RPMI 1640 medium containing 20% FBS and differentiated with complete media containing 1.5% DMSO (Sigma-Aldrich, MO, USA) for 5 days. Differentiated HL-60 (dHL-60) was used in vitro assay for neutrophil migration (34)(35)(36).…”

MicroRNA, an Antisense RNA, in Sensing Myeloid Malignancies

“…High expressions of miR-155, miR-126, and miR-130 in MDS restrain megakaryopoiesis and may account for higher frequency of thrombocytopenia observed during disease progression ( 46 ). However, recent evidence reveals that reduction of Rho family members by miR-155 contributes to impaired neutrophil migration in MDS ( 58 ). miR-21 expression has been found to be increased in MDS, and its interaction with SMAD7 mRNA leads to ineffective, MDS-like hematopoiesis via overactivating TGFβ signaling ( 42 ).…”