Iron, inflammation, and early death in adults with sickle cell disease.
BACKGROUND
Patients with sickle cell disease (SCD) have markers of chronic inflammation, but the mechanism of inflammation and its relevance to patient survival are unknown.


OBJECTIVE
To assess the relationship between iron, inflammation, and early death in SCD.


RESULTS
Using peripheral blood mononuclear cell transcriptome profile hierarchical clustering, we classified 24 patients and 10 controls in clusters with significantly different expression of genes known to be regulated by iron. Subsequent gene set enrichment analysis showed that many genes associated with the high iron cluster were involved in the toll-like receptor system (TLR4, TLR7, and TLR8) and inflammasome complex pathway (NLRP3, NLRC4, and CASP1). Quantitative PCR confirmed this classification and showed that ferritin light chain, TLR4, and interleukin-6 expression were >100-fold higher in patients than in controls (P<0.001). Further linking intracellular iron and inflammation, 14 SCD patients with a ferroportin Q248H variant that causes intracellular iron accumulation had significantly higher levels of interleukin-6 and C-reactive protein compared with 14 matched SCD patients with the wild-type allele (P<0.05). Finally, in a cohort of 412 patients followed for a median period of 47 months (interquartile range, 24-82), C-reactive protein was strongly and independently associated with early death (hazard ratio, 3.0; 95% confidence interval, 1.7-5.2; P<0.001).


CONCLUSIONS
Gene expression markers of high intracellular iron in patients with SCD are associated with markers of inflammation and mortality. The results support a model in which intracellular iron promotes inflammatory pathways, such as the TLR system and the inflammasome, identifying important new pathways for additional investigation.
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Eduard J
EJ
van Beers
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Yanqin
Y
Yang
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Nalini
N
Raghavachari
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Xin
X
Tian
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Darlene T
DT
Allen
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
James S
JS
Nichols
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Laurel
L
Mendelsohn
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Sergei
S
Nekhai
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
Victor R
VR
Gordeuk
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.).
James G
JG
Taylor
From the Hematology Branch (E.J.v.B., D.T.A., J.S.N., L.M., J.G.T., G.J.K.), Genomics Core Facility (Y.Y., N.R.), and Office of Biostatistics Research (X.T.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC (S.N.); Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago (V.R.G.); and Division of Hematology-Oncology, Department of Medicine and the Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, PA (G.J.K.). Current address: Van Creveldkliniek, University Medical Center Utrecht, Utrecht, The Netherlands (E.J.v.B.). katogj@upmc.edu.
Gregory J
GJ
Kato
D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood* / Q000235:genetics* / Q000401:mortality; D015331:Cohort Studies; D005260:Female; D005819:Genetic Markers / Q000235:genetics*; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000235:genetics / Q000401:mortality; D007501:Iron / Q000097:blood*; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008297:Male; D009026:Mortality / Q000639:trends; D011446:Prospective Studies; D012042:Registries
D005819:Genetic Markers; D007501:Iron
gene expression; inflammation; iron; mortality; sickle cell disease