| First Author | Beckman JD | Year | 2020 |
| Journal | Front Immunol | Volume | 11 |
| Pages | 613278 | PubMed ID | 33542720 |
| Mgi Jnum | J:315108 | Mgi Id | MGI:6804330 |
| Doi | 10.3389/fimmu.2020.613278 | Citation | Beckman JD, et al. (2020) Endothelial TLR4 Expression Mediates Vaso-Occlusive Crisis in Sickle Cell Disease. Front Immunol 11:613278 |
| abstractText | Heme, released from red blood cells in sickle cell disease (SCD), interacts with toll-like receptor 4 (TLR4) to activate NF-kappaB leading to the production of cytokines and adhesion molecules which promote inflammation, pain, and vaso-occlusion. In SCD, TLR4 inhibition has been shown to modulate heme-induced microvascular stasis and lung injury. We sought to delineate the role of endothelial verses hematopoietic TLR4 in SCD by developing a TLR4 null transgenic sickle mouse. We bred a global Tlr4(-/-) deficiency state into Townes-AA mice expressing normal human adult hemoglobin A and Townes-SS mice expressing sickle hemoglobin S. SS-Tlr4(-/-) had similar complete blood counts and serum chemistries as SS-Tlr4 (+/+) mice. However, SS-Tlr4(-/-) mice developed significantly less microvascular stasis in dorsal skin fold chambers than SS-Tlr4 (+/+) mice in response to challenges with heme, lipopolysaccharide (LPS), and hypoxia/reoxygenation (H/R). To define a potential mechanism for decreased microvascular stasis in SS-Tlr4(-/-) mice, we measured pro-inflammatory NF-kappaB and adhesion molecules in livers post-heme challenge. Compared to heme-challenged SS-Tlr4 (+/+) livers, SS-Tlr4 (-/-) livers had lower adhesion molecule and cytokine mRNAs, NF-kappaB phospho-p65, and adhesion molecule protein expression. Furthermore, lung P-selectin and von Willebrand factor immunostaining was reduced. Next, to establish if endothelial or hematopoietic cell TLR4 signaling is critical to vaso-occlusive physiology, we created chimeric mice by transplanting SS-Tlr4 (-/-) or SS-Tlr4 (+/+) bone marrow into AA-Tlr4 (-/-) or AA-Tlr4 (+/+) recipients. Hemin-stimulated microvascular stasis was significantly decreased when the recipient was AA-Tlr4(-/-) . These data demonstrate that endothelial, but not hematopoietic, TLR4 expression is necessary to initiate vaso-occlusive physiology in SS mice. |
