Background levels of neomorphic 2-hydroxyglutarate facilitate proliferation of primary fibroblasts

Each cell types or tissues contain certain "physiological" levels of R-2-hydroxyglutarate (2HG), as well as enzymes for its synthesis and degradation. 2HG accumulates in certain tumors, possessing heterozygous point mutations of isocitrate dehydrogenases IDH1 (cytosolic) or IDH2 (mitochondrial) and contributes to strengthening their malignancy by inhibiting 2-oxoglutarate-dependent dioxygenases. By blocking histone de-methylation and 5-methyl-cytosine hydroxylation, 2HG maintains cancer cells de-differentiated and promotes their proliferation. However, physiological 2HG formation and formation by non-mutant IDH1/2 in cancer cells were neglected. Consequently, low levels of 2HG might play certain physiological roles. We aimed to elucidate this issue and found that compared to highest 2HG levels in hepatocellular carcinoma HepG2 cells and moderate levels in neuroblastoma SH-SY5Y cells, rat primary fibroblast contained low basal 2HG levels at early passages. These levels increased at late passage and likewise 2HG/2OG ratios dropped without growth factors and enormously increased at hypoxia, reaching levels compared to cancer HepG2 cells. Responses in SH-SY5Y cells were opposite. Moreover, external 2HG supplementation enhanced fibroblast growth. Hence, we conclude that low 2HG levels facilitate cell proliferation in primary fibroblasts, acting via hypoxia-induced factor regulations and epigenetic changes.

Silica-modified monodisperse hexagonal lanthanide nanocrystals: synthesis and biological properties

Oleic acid-stabilized hexagonal NaYF4:Yb(3+)/Er(3+) nanocrystals, emitting green and red luminescence, were prepared by the high-temperature co-precipitation of lanthanide chlorides. By varying the reaction time and the Ln(3+)/Na(+) ratio, the nanocrystal size can be controlled within the range 16-270 nm. The maximum upconversion quantum yield is achieved under 970 nm excitation. The reverse microemulsion technique using hydrolysis and condensation of tetraethoxysilane is a suitable method to coat the nanocrystal surface with a silica shell to make the particles dispersible and colloidally stable in aqueous media. During the subsequent functionalization, (3-aminopropyl)trimethoxysilane introduced amino groups onto the silica to enable future bioconjugation with the target molecules. All specimens were characterized by TEM microscopy, electron and X-ray diffraction, ATR FT-IR spectroscopy, and upconversion luminescence. Finally, in vitro cytotoxicity and intracellular nanoparticle uptake (using confocal microscopy) were determined with human cervical carcinoma HeLa and mRoGFP HeLa cells, respectively. From the investigated particles, amino-functionalized NaYF4:Yb(3+)/Er(3+) nanocrystals internalized into the cells most efficiently. The nanoparticles proved to be nontoxic at moderate concentrations, which is important when considering their prospective application in biolabeling and luminescence imaging of various cell types.

Redistribution of cell death-inducing DNA fragmentation factor-like effector-a (CIDEa) from mitochondria to nucleus is associated with apoptosis in HeLa cells

Cell death-inducing DFF[DNA fragmentation factor]-like effector-a (CIDEa), may initiate apoptosis by disrupting a complex consisting of 40-kDa caspase-3-activated nuclease (DFF40/CAD) and its 45-kDa inhibitor (DFF45/ICAD). CIDEa, however, was found to be localized in mitochondria. We have performed immunodetection of CIDEa in whole cells and subcellular fractions of HeLa cells adapted for a tetracycline-inducible CIDEa expression. Using immunocytochemistry we observed redistribution, enhanced upon treatment with camptothecin or valinomycin, of CIDEa to nucleus. Similarly, CIDEa content increased in the nuclear fraction but decreased in cytosolic fraction in cells treated to initiate apoptosis. We hypothesize that CIDEa is sequestered in mitochondria while transfer of this potentially dangerous protein from mitochondria into nucleus intensifies or even initiates apoptosis.