Hemoglobin-Induced Endothelial Cell Permeability Is Controlled, in Part, via a Myeloid Differentiation Primary Response Gene–88–Dependent Signaling Mechanism

C Lisk, D Kominsky, S Ehrentraut… - American journal of …, 2013 - atsjournals.org
C Lisk, D Kominsky, S Ehrentraut, J Bonaventura, R Nuss, K Hassell, E Nozik-Grayck
American journal of respiratory cell and molecular biology, 2013atsjournals.org
The release of hemoglobin (Hb) with hemolysis causes vascular dysfunction. New evidence
implicates Hb-induced NF-κB and hypoxia inducible factor (HIF) activation, which may be
under the control of a Toll-like receptor (TLR)–signaling pathway. Nearly all TLR-signaling
pathways activate the myeloid differentiation primary response gene–88 (MyD88) that
regulates NF-κB. We hypothesized that the differing transition states of Hb influence
endothelial cell permeability via NF-κB activation and HIF regulation through a MyD88 …
The release of hemoglobin (Hb) with hemolysis causes vascular dysfunction. New evidence implicates Hb-induced NF-κB and hypoxia inducible factor (HIF) activation, which may be under the control of a Toll-like receptor (TLR)–signaling pathway. Nearly all TLR-signaling pathways activate the myeloid differentiation primary response gene–88 (MyD88) that regulates NF-κB. We hypothesized that the differing transition states of Hb influence endothelial cell permeability via NF-κB activation and HIF regulation through a MyD88-dependent pathway. In cultured human dermal microvascular endothelial cells (HMECs-1), we examined the effects of Hb in the ferrous (HbFe2+), ferric (HbFe3+), and ferryl (HbFe4+) transition states on NF-κB and HIF activity, HIF-1α and HIF-2α mRNA up-regulation, and monolayer permeability, in the presence or absence of TLR4, MyD88, NF-κB, or HIF inhibition, as well as superoxide dismutase (SOD) and catalase. Our data showed that cell-free Hb, in each transition state, induced NF-κB and HIF activity, up-regulated HIF-1α and HIF-2α mRNA, and increased HMEC-1 permeability. The blockade of either MyD88 or NF-κB, but not TLR4, attenuated Hb-induced HIF activity, the up-regulation HIF-1 and HIF-2α mRNA, and HMEC-1 permeability. The inhibition of HIF activity exerted less of an effect on Hb-induced monolayer permeability. Moreover, SOD and catalase attenuated NF-κB, HIF activity, and monolayer permeability. Our results demonstrate that Hb-induced NF-κB and HIF are regulated by two mechanisms, either MyD88 activation or Hb transition state–induced ROS formation, that influence HMEC-1 permeability.
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