Monomethylfumarate induces γ-globin expression and fetal hemoglobin production in cultured human retinal pigment epithelial (RPE) and erythroid cells, and in intact retina.
OBJECTIVE
Sickle retinopathy (SR) is a major cause of vision loss in sickle cell disease (SCD). There are no strategies to prevent SR and treatments are extremely limited. The present study evaluated (1) the retinal pigment epithelial (RPE) cell as a hemoglobin producer and novel cellular target for fetal hemoglobin (HbF) induction, and (2) monomethylfumarate (MMF) as an HbF-inducing therapy and abrogator of oxidative stress and inflammation in SCD retina.


METHODS
Human globin gene expression was evaluated by RT-quantitative (q)PCR in the human RPE cell line ARPE-19 and in primary RPE cells isolated from Townes humanized SCD mice. γ-Globin promoter activity was monitored in KU812 stable dual luciferase reporter expressing cells treated with 0 to 1000 μM dimethylfumarate, MMF, or hydroxyurea (HU; positive control) by dual luciferase assay. Reverse transcriptase-qPCR, fluorescence-activated cell sorting (FACS), immunofluorescence, and Western blot techniques were used to evaluate γ-globin expression and HbF production in primary human erythroid progenitors, ARPE-19, and normal hemoglobin producing (HbAA) and homozygous β(s) mutation (HbSS) RPE that were treated similarly, and in MMF-injected (1000 μM) HbAA and HbSS retinas. Dihydroethidium labeling and nuclear factor (erythroid-derived 2)-like 2 (Nrf2), IL-1β, and VEGF expression were also analyzed.


RESULTS
Retinal pigment epithelial cells express globin genes and synthesize adult and fetal hemoglobin MMF stimulated γ-globin expression and HbF production in cultured RPE and erythroid cells, and in HbSS mouse retina where it also reduced oxidative stress and inflammation.


CONCLUSIONS
The production of hemoglobin by RPE suggests the potential involvement of this cell type in the etiology of SR. Monomethylfumarate influences multiple parameters consistent with improved retinal health in SCD and may therefore be of therapeutic potential in SR treatment.
Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, Georgia, United States.
Wanwisa
W
Promsote
Department of Pediatrics, Georgia Regents University, Augusta, Georgia, United States.
Levi
L
Makala
Department of Pediatrics, Georgia Regents University, Augusta, Georgia, United States.
Biaoru
B
Li
Department of Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia, United States.
Sylvia B
SB
Smith
Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, Georgia, United States The Cancer Center, Georgia Regents University, Augusta, Georgia, United States.
Nagendra
N
Singh
Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, Georgia, United States James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, United States The Cancer Center, Georgia Regents University, Augusta, Georgia, United States.
Vadivel
V
Ganapathy
Department of Pediatrics, Georgia Regents University, Augusta, Georgia, United States The Cancer Center, Georgia Regents University, Augusta, Georgia, United States.
Betty S
BS
Pace
Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, Georgia, United States Department of Ophthalmology, Georgia Regents University, Augusta, Georgia, United States.
Pamela M
PM
Martin
D000328:Adult; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D041905:Erythroid Cells / Q000187:drug effects* / Q000378:metabolism; D005319:Fetal Hemoglobin / Q000378:metabolism*; D005650:Fumarates / Q000494:pharmacology*; D006801:Humans; D008298:Maleates / Q000494:pharmacology*; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D012160:Retina / Q000166:cytology* / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism; D055545:gamma-Globins / Q000378:metabolism*
D000975:Antioxidants; D005650:Fumarates; D008298:Maleates; D051267:NF-E2-Related Factor 2; D055545:gamma-Globins; C073341:citraconic acid; D005319:Fetal Hemoglobin
fetal hemoglobin (HbF); monomethylfumarate; retinal pigment epithelium (RPE); sickle cell disease; sickle cell retinopathy