Crosstalk between the FGFR2 and TP53 genes in breast cancer: data from an association study and epistatic interaction analysis

To evaluate the potential for gene-gene interaction effects in sporadic breast cancer (BC) risk, we studied combinations of the fibroblast growth factor receptor 2 (FGFR2) rs1219648 and tumor protein 53 (TP53) rs1042522, rs1625895, and rs17878362 polymorphisms in BC patients (n=388) and healthy persons (n=275). In addition to a single-locus effect manifested by the association of FGFR2 rs1219648 and TP53 rs1042522 polymorphisms with high BC risk, depending on menopause status (0.001相似文献   

Dual effect of heat shock on DNA replication and genome integrity

Heat shock (HS) is one of the better-studied exogenous stress factors. However, little is known about its effects on DNA integrity and the DNA replication process. In this study, we show that in G1 and G2 cells, HS induces a countable number of double-stranded breaks (DSBs) in the DNA that are marked by γH2AX. In contrast, in S-phase cells, HS does not induce DSBs but instead causes an arrest or deceleration of the progression of the replication forks in a temperature-dependent manner. This response also provoked phosphorylation of H2AX, which appeared at the sites of replication. Moreover, the phosphorylation of H2AX at or close to the replication fork rescued the fork from total collapse. Collectively our data suggest that in an asynchronous cell culture, HS might affect DNA integrity both directly and via arrest of replication fork progression and that the phosphorylation of H2AX has a protective effect on the arrested replication forks in addition to its known DNA damage signaling function.     

Characterization of the nature of photosynthetic recovery of wheat seedlings from short-term dark heat exposures and analysis of the mode of acclimation to different light intensities

The nature of photosynthetic recovery was investigated in 10-d-old wheat (Triticum aestivum L., cv. Moskovskaya-35) seedlings exposed to temperatures of 40 and 42 °C for 20 min and to temperature 42 °C for 40 min in the dark. The aftereffect of heat treatment was monitored by growing the heat-treated plants in low/moderate/high light at 20 °C for 72 h. The net photosynthetic rates (P_N) and the fluorescence ratios F_v/F_m were evaluated in intact primary leaves and the rates of cyclic and non-cyclic photophosphorylation were measured in the isolated thylakoids. At least two temporally separated steps were identified in the path of recovery from heat stress at 40 and 42 °C in the plants growing in high and moderate/high light, respectively. Both photochemical activity of the photosystem II (PSII) and the activity of CO₂ assimilation system were lowered during the first step in comparison with the corresponding activities immediately after heat treatment. During the second step, the photosynthetic activities completely or partly recovered. Recovery from heat stress at 40 °C was accompanied by an appreciably higher rate of cyclic photophosphorylation in comparison with control non-heated seedlings. In pre-heated seedlings, the tolerance of the PSII to photoinhibition was higher than in non-treated ones. The mode of acclimation to different light intensities after heat exposures is analyzed.     

Distinct organization of energy metabolism in HL-1 cardiac cell line and cardiomyocytes

Expression and function of creatine kinase (CK), adenylate kinase (AK) and hexokinase (HK) isoforms in relation to their roles in regulation of oxidative phosphorylation (OXPHOS) and intracellular energy transfer were assessed in beating (B) and non-beating (NB) cardiac HL-l cell lines and adult rat cardiomyocytes or myocardium. In both types of HL-1 cells, the AK2, CKB, HK1 and HK2 genes were expressed at higher levels than the CKM, CKMT2 and AK1 genes. Contrary to the saponin-permeabilized cardiomyocytes the OXPHOS was coupled to mitochondrial AK and HK but not to mitochondrial CK, and neither direct transfer of adenine nucleotides between CaMgATPases and mitochondria nor functional coupling between CK-MM and CaMgATPases was observed in permeabilized HL-1 cells. The HL-1 cells also exhibited deficient complex I of the respiratory chain. In conclusion, contrary to cardiomyocytes where mitochondria and CaMgATPases are organized into tight complexes which ensure effective energy transfer and feedback signaling between these structures via specialized pathways mediated by CK and AK isoforms and direct adenine nucleotide channeling, these complexes do not exist in HL-1 cells due to less organized energy metabolism.     

Glioma Cell and Astrocyte Co-cultures As a Model to Study Tumor–Tissue Interactions: A Review of Methods

Astrocytes are a dominant cell type that envelopes the glioma bed. Typically, that is followed by formation of contacts between astrocytes and glioma cells and accompanied by change in astrocyte phenotype, a phenomenon known as a ‘reactive astrogliosis.’ Generally considered glioma-promoting, astrocytes have many controversial peculiarities in communication with tumor cells, which need thorough examination in vitro. This review is devoted to in vitro co-culture studies of glioma cells and astrocytes. Firstly, we list several fundamental works which allow understanding the modalities of co-culturing. Cell-to-cell interactions between astrocytes and glioma cells, the roles of astrocytes in tumor metabolism, and glioma-related angiogenesis are reviewed. In the review, we also discuss communications between glioma stem cells and astrocytes. Co-cultures of glioma cells and astrocytes are used for studying anti-glioma treatment approaches. We also enumerate surgical, chemotherapeutic, and radiotherapeutic methods assessed in co-culture experiments. In conclusion, we underline collisions in the field and point out the role of the co-cultures for neurobiological studies.     

Gliotoxin penetrates and impairs the integrity of the human blood-brain barrier in vitro

Cerebral fungal infections represent an important public health concern, where a key element of pathophysiology is the ability of the fungi to cross the blood-brain barrier (BBB). Yet the mechanism used by micro-organisms to cross such a barrier and invade the brain parenchyma remains unclear. This study investigated the effects of gliotoxin (GTX), a mycotoxin secreted by Aspergillus fumigatus, on the BBB using brain microvascular endothelial cells (BMECs) derived from induced pluripotent stem cells (iPSCs). We observed that both acute (2 h) and prolonged (24 h) exposure to GTX at the level of 1 μM or higher compromised BMECs monolayer integrity. Notably, acute exposure was sufficient to disrupt the barrier function in iPSC-derived BMECs, resulting in decreased transendothelial electrical resistance (TEER) and increased fluorescein permeability. Further, our data suggest that such disruption occurred without affecting tight junction complexes, via alteration of cell-matrix interactions, alterations in F-actin distribution, through a protein kinase C-independent signaling. In addition to its effect on the barrier function, we have observed a low permeability of GTX across the BBB. This fact can be partially explained by possible interactions of GTX with membrane proteins. Taken together, this study suggests that GTX may contribute in cerebral invasion processes of Aspergillus fumigatus by altering the blood-brain barrier integrity without disrupting tight junction complexes.     

Sap Flow Measurements in a Socotra Dragon’s Blood Tree (<Emphasis Type="Italic">Dracaena cinnabari</Emphasis>) in its Area of Origin

For the first time, in situ field measurements of sap flow were conducted in adult Dracaena cinnabari plant native to the arid tropical climate of Socotra Island. The heat field deformation (HFD) method was applied using both single and multi-point sensors to study azimuthal and radial sap flow variability in stem, roots and first-order branches over two weeks during a winter monsoon. The main aim of this work was to monitor sap flow in adult D. cinnabari in-situ to better understand its physiological adaptation to extreme arid environments. The second aim was to compare our results with earlier sap flow measurements in adult D. draco uing the same HFD method. The last question we wanted to answer was comparison of sap flow measurements in both, young and adult Dracaena species. We found that sap flow magnitude is low and of a similar range in all observed D. species. High sap flow variability was recorded in different parts of adult D. cinnabari plant which changed throughout the day responding to interplay between intrinsic and extrinsic water potential gradients induced by sunlight. Maximum sap flow levels had variable pattern around stem in response to sun exposure, similarly as it was observed in adult D. draco plant. Sensors installed tangentially in stem xylem showed that water transport in adult D. cinnabari may move in lateral direction. This work also presents several methodological aspects detected from earlier observations of dicots which proved to be more pronounced in adult D. species. These methodologies relate to interpreting negative sap flow rates in conjunction with established axial flow reversal during hydraulic redistribution usually occurring under low evaporative demands and dry soil. Conversely, flow reversal during the day under high evaporative demands and wet soil may designate lateral water movement induced by internal water redistribution.     

Mechanism of interactions of alpha-naphthoflavone with cytochrome P450 3A4 explored with an engineered enzyme bearing a fluorescent probe

Design of a partially cysteine-depleted C98S/C239S/C377S/C468A cytochrome P450 3A4 mutant designated CYP3A4(C58,C64) allowed site-directed incorporation of thiol-reactive fluorescent probes into alpha-helix A. The site of modification was identified as Cys-64 with the help of CYP3A4(C58) and CYP3A4(C64), each bearing only one accessible cysteine. Changes in the fluorescence of CYP3A4(C58,C64) labeled with 6-(bromoacetyl)-2-(dimethylamino)naphthalene (BADAN), 7-(diethylamino)-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM), or monobromobimane (mBBr) were used to study the interactions with bromocriptine (BCT), 1-pyrenebutanol (1-PB), testosterone (TST), and alpha-naphthoflavone (ANF). Of these substrates only ANF has a specific effect, causing a considerable decrease in fluorescence intensity of BADAN and CPM and increasing the fluorescence of mBBr. This ANF-binding event in the case of the BADAN-modified enzyme is characterized by an S50 of 18.2 +/- 0.7, compared with the value of 2.2 +/- 0.3 for the ANF-induced spin transition, thus revealing an additional low-affinity binding site. Studies of the effect of TST, 1-PB, and BCT on the interactions of ANF monitored by changes in fluorescence of CYP3A4(C58,C64)-BADAN or by the ANF-induced spin transition revealed no competition by these substrates. Investigation of the kinetics of fluorescence increase upon H2O2-dependent heme depletion suggests that labeled CYP3A4(C58,C64) is represented by two conformers, one of which has the fluorescence of the BADAN and CPM labels completely quenched, presumably by photoinduced electron transfer from the neighboring Trp-72 and/or Tyr-68 residues. The binding of ANF to the newly discovered binding site appears to affect the interactions of the label with the above residue(s), thus modulating the fraction of the fluorescent conformer.