Human Retinal Transmitochondrial Cybrids with J or H mtDNA Haplogroups Respond Differently to Ultraviolet Radiation: Implications for Retinal Diseases

Abstract

BackgroundIt has been recognized that cells do not respond equally to ultraviolet (UV) radiation but it is not clear whether this is due to genetic, biochemical or structural differences of the cells. We have a novel cybrid (cytoplasmic hybrids) model that allows us to analyze the contribution of mitochondrial DNA (mtDNA) to cellular response after exposure to sub-lethal dose of UV. mtDNA can be classified into haplogroups as defined by accumulations of specific single nucleotide polymorphisms (SNPs). Recent studies have shown that J haplogroup is high risk for age-related macular degeneration while the H haplogroup is protective. This study investigates gene expression responses in J cybrids versus H cybrids after exposure to sub-lethal doses of UV-radiation.Methodology/Principal FindingsCybrids were created by fusing platelets isolated from subjects with either H (n = 3) or J (n = 3) haplogroups with mitochondria-free (Rho0) ARPE-19 cells. The H and J cybrids were cultured for 24 hours, treated with 10 mJ of UV-radiation and cultured for an additional 120 hours. Untreated and treated cybrids were analyzed for growth rates and gene expression profiles. The UV-treated and untreated J cybrids had higher growth rates compared to H cybrids. Before treatment, J cybrids showed lower expression levels for CFH, CD55, IL-33, TGF-A, EFEMP-1, RARA, BCL2L13 and BBC3. At 120 hours after UV-treatment, the J cybrids had decreased CFH, RARA and BBC3 levels but increased CD55, IL-33 and EFEMP-1 compared to UV-treated H cybrids.Conclusion/SignificanceIn cells with identical nuclei, the cellular response to sub-lethal UV-radiation is mediated in part by the mtDNA haplogroup. This supports the hypothesis that differences in growth rates and expression levels of complement, inflammation and apoptosis genes may result from population-specific, hereditary SNP variations in mtDNA. Therefore, when analyzing UV-induced damage in tissues, the mtDNA haplogroup background may be important to consider.

Mitochondrial DNA Variation in Human Radiation and Disease

“…Comparison of haplogroup H and J mtDNAs on a retinal pigment epithelial (RPE) nuclear background revealed that J mtDNA cells have reduced ATP, ROS, and reactive nitrogen species levels; increased lactate and growth rate; reduced expression of macular degeneration gene CFH; altered expression of genes involved in cell signaling, inflammation, and metabolism; and altered UV exposure response (Kenney et al, 2014a; Malik et al, 2014). Comparison of European H versus African L mtDNAs in RPE cells showed that the L mtDNA cells had lower ATP turnover rates; reduced spare respiratory capacity; reduced mtDNA copy number; increased mtDNA mRNA levels; and altered expression of nuclear complement, inflammation, and autoimmunity genes (Kenney et al, 2014b).…”

Increased expression of ApoE and protection from amyloid-beta toxicity in transmitochondrial cybrids with haplogroup K mtDNA

“…Using the cybrid model, it has been demonstrated that different mtDNA haplogroups mediate cellular bioenergetics, the levels of methylation, rates of growth, and transcription of inflammatory, complement and signaling pathway genes. (Bellizzi et al, 2009; Gomez-Duran et al, 2010; Chen et al, 2012; Pacheu-Grau et al, 2013; Kenney et al, 2013b, 2014a, 2014b; Malik et al, 2014) In addition, cybrids with different mtDNA haplogroups have different responses to hydrogen peroxide or ultraviolet radiation. (Malik et al, 2014; Mueller et al, 2012b; Lin et al, 2012) The conplastic mouse model, which crosses the mtDNA from one strain of mouse into a different background, has illustrated altered mitochondrial-nuclear interactions and increased susceptibility to cardiovascular disease.…”

“…(Bellizzi et al, 2009; Gomez-Duran et al, 2010; Chen et al, 2012; Pacheu-Grau et al, 2013; Kenney et al, 2013b, 2014a, 2014b; Malik et al, 2014) In addition, cybrids with different mtDNA haplogroups have different responses to hydrogen peroxide or ultraviolet radiation. (Malik et al, 2014; Mueller et al, 2012b; Lin et al, 2012) The conplastic mouse model, which crosses the mtDNA from one strain of mouse into a different background, has illustrated altered mitochondrial-nuclear interactions and increased susceptibility to cardiovascular disease. (Fetterman et al, 2013) These studies support the hypothesis that an individual’s mtDNA background contributes to baseline cellular homeostasis, making the cells differentially susceptible to identical stressors and contributing to differential disease susceptibility.…”

MITOCHONDRIAL DNA POLYMORPHISM AND PATHOGENETICS OF SUDDEN CARDIAC DEATH (review)

“…Проведенные эксперименты продемонстрировали, что гаплогруппа J мтДНК ассоциирована с более низким уровнем продукции как АТФ, так и АФК, чем гаплогруппа Н; также выявлены различия в экспрессии некоторых ядерных генов, вовлеченных в различные биохимические пути (апоптоз, воспаление, система комплемента) [32,33]. Цибридные линии с гаплогруппой J имели также более высокую скорость роста, по сравнению с Н, в том числе при воздействии сублетальных доз ультрафиолетового излучения [37]. Гаплогруппа Т была ассоциирована с более высоким по сравнению с гаплогруппой Н числом копий мтДНК в клетке, большей скоростью роста культуры и меньшей чувствительностью к окислительному стрессу, однако при этом активность комплексов I-V дыхательной цепи не различалась между двумя генотипами [40].…”