Loss of Hfe leads to progression of tumor phenotype in primary retinal pigment epithelial cells.

Abstract

PURPOSE:

Hemochromatosis is a disorder of iron overload arising mostly from mutations in HFE. HFE is expressed in retinal pigment epithelium (RPE), and Hfe(-/-) mice develop age-related iron accumulation and retinal degeneration associated with RPE hyperproliferation. Here, the mechanism underlying the hyperproliferative phenotype in RPE was investigated.

METHODS:

Cellular senescence was monitored by β-galactosidase activity. Gene expression was monitored by real-time PCR. Survivin was analyzed by Western blot and immunofluorescence. Migration and invasion were monitored using appropriate kits. Glucose transporters (GLUTs) were monitored by 3-O-methyl-D-glucose uptake. Histone deacetylases (HDACs) were studied by monitoring catalytic activity and acetylation status of histones H3/H4.

RESULTS:

Hfe(-/-) RPE cells exhibited slower senescence rate and higher survivin expression than wild type cells. Hfe(-/-) cells migrated faster and showed greater glucose uptake and increased expression of GLUTs. The expression of HDACs and DNA methyltransferase (DNMTs) also was increased. Similarly, RPE cells from hemojuvelin (Hjv)-knockout mice, another model of hemochromatosis, also had increased expression of GLUTs, HDACs, and DNMTs. The expression of Slc5a8 was decreased in Hfe(-/-) RPE cells, but treatment with a DNA methylation inhibitor restored the transporter expression, indicating involvement of DNA methylation in the silencing of Slc5a8 in Hfe(-/-) cells.

CONCLUSIONS:

RPE cells from iron-overloaded mice exhibit several features of tumor cells: decreased senescence, enhanced migration, increased glucose uptake, and elevated levels of HDACs and DNMTs. These features are seen in Hfe(-/-) RPE cells as well as in Hjv(-/-) RPE cells, providing a molecular basis for the hyperproliferative phenotype of Hfe(-/-) and Hjv(-/-) RPE cells.

• Authors: Jaya P Gnana-Prakasam, Rajalakshmi Veeranan-Karmegam, Veena Coothankandaswamy, Sushma K Reddy, Pamela M Martin, Muthusamy Thangaraju, Sylvia B Smith, Vadivel Ganapathy
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 54 Issue 1 Pg. 63-71 (Jan 07 2013) ISSN: 1552-5783 [Electronic] United States
• PMID: 23169885 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Amino Acid Transport Systems
• Birc5 protein, mouse
• Cation Transport Proteins
• Hemochromatosis Protein
• Hfe protein, mouse
• Histocompatibility Antigens Class I
• Inhibitor of Apoptosis Proteins
• Membrane Proteins
• Monocarboxylic Acid Transporters
• Plasma Membrane Neurotransmitter Transport Proteins
• Repressor Proteins
• Slc5a8 protein, mouse
• Slc6A14 protein, mouse
• Survivin
• Glucose

Topics

• Amino Acid Transport Systems (genetics)
• Animals
• Cation Transport Proteins (genetics)
• Cell Movement (physiology)
• Cell Transformation, Neoplastic (pathology)
• Cellular Senescence (physiology)
• DNA Methylation (physiology)
• Disease Progression
• Eye Neoplasms (genetics, pathology, physiopathology)
• Female
• Glucose (pharmacokinetics)
• Hemochromatosis (genetics, pathology, physiopathology)
• Hemochromatosis Protein
• Histocompatibility Antigens Class I (genetics)
• Inhibitor of Apoptosis Proteins (metabolism)
• Male
• Membrane Proteins (genetics)
• Mice
• Mice, 129 Strain
• Mice, Inbred C57BL
• Mice, Knockout
• Mice, Nude
• Monocarboxylic Acid Transporters
• Phenotype
• Plasma Membrane Neurotransmitter Transport Proteins (genetics)
• Primary Cell Culture
• Repressor Proteins (metabolism)
• Retinal Pigment Epithelium (pathology, physiopathology)
• Survivin
• Transplantation, Heterologous