MTT Conversion Research Articles

An experimental platform using human intestinal epithelial cell lines to differentiate between hazardous and non-hazardous proteins

Human intestinal epithelial cell lines (T84, Caco-2, and HCT-8) grown on permeable Transwell™ filters serve as models of the gastrointestinal barrier. In this study, this in vitro model system was evaluated for effectiveness at distinguishing between hazardous and non-hazardous proteins. Indicators of cytotoxicity (LDH release, MTT conversion), monolayer barrier integrity ([3H]-inulin flux, horseradish peroxidase flux, trans-epithelial electrical resistance [TEER]), and inflammation (IL-8, IL-6 release) were monitored following exposure to hazardous or non-hazardous proteins. The hazardous proteins examined include streptolysin O (from Streptococcus pyogenes), Clostridium difficile Toxins A and B, heat-labile toxin from enterotoxigenic Escherichia coli, listeriolysin O (from Listeria monocytogenes), melittin (from bee venom), and mastoparan (from wasp venom). Non-hazardous proteins included bovine and porcine serum albumin, bovine fibronectin, and ribulose bisphosphate carboxylase/oxygenase (RuBisco) from spinach. Food allergenic proteins bovine milk β-lactoglobulin and peanut Ara h 2 were also tested as was the anti-nutritive food protein wheat germ agglutinin. Results demonstrated that this model system effectively distinguished between hazardous and non-hazardous proteins through combined analysis of multiple cells lines and assays. This experimental strategy may represent a useful adjunct to multi-component analysis of proteins with unknown hazard profiles.

Effects of Ranolazine on Astrocytes and Neurons in Primary Culture.

Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10−7, 10−6 and 10−5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents.

Efeito do produto iônico do biovidro 60S na diferenciação osteogênica de células-tronco mesenquimais do tecido adiposo de cães

O objetivo do presente trabalho foi avaliar o produto iônico do biovidro 60S (BV60S) na diferenciação osteogênica de células-tronco mesenquimais de origem adiposa (CTM-AD) de cães. As CTM-AD foram diferenciadas sem OSTe com o produto iônico (PI OST) por sete, 14 e 21 dias. Avaliou-se o MTT, a fosfatase alcalina (FA), o colágeno, mineralização e as expressões de osterix (OSX), sialoproteína óssea (BSP), osteonectina (ON) e osteocalcina (OC). O grupo PI OSTmostrou menor conversão de MTT aos sete dias e maior conversão aos 21 dias. A atividade de FA foi maior no grupo OST, aos 14 e 21 dias. A síntese de colágeno foi maior no grupo OST aos sete e 21 dias. Verificou-se maior área mineralizada no grupo PI OSTem todos os tempos. Não houve diferenças nas expressões de OSX e OC entre os grupos. Observou-se maior expressão de BSP no grupo PI OST, aos 14 e 21 dias. A expressão de ON foi maior no grupo OST aos 14 dias. Concluiu-se que o produto iônico do BV60S favorece a osteogênese in vitro de CTM-AD de cães.

Coenzyme Q10 protects astrocytes from ROS-induced damage through inhibition of mitochondria-mediated cell death pathway.

Coenzyme Q10 (CoQ10) acts by scavenging reactive oxygen species to protect neuronal cells against oxidative stress in neurodegenerative diseases. The present study was designed to examine whether CoQ10 was capable of protecting astrocytes from reactive oxygen species (ROS) mediated damage. For this purpose, ultraviolet B (UVB) irradiation was used as a tool to induce ROS stress to cultured astrocytes. The cells were treated with 10 and 25 μg/ml of CoQ10 for 3 or 24 h prior to the cells being exposed to UVB irradiation and maintained for 24 h post UVB exposure. Cell viability was assessed by MTT conversion assay. Mitochondrial respiration was assessed by respirometer. While superoxide production and mitochondrial membrane potential were measured using fluorescent probes, levels of cytochrome C (cyto-c), cleaved caspase-9, and caspase-8 were detected using Western blotting and/or immunocytochemistry. The results showed that UVB irradiation decreased cell viability and this damaging effect was associated with superoxide accumulation, mitochondrial membrane potential hyperpolarization, mitochondrial respiration suppression, cyto-c release, and the activation of both caspase-9 and -8. Treatment with CoQ10 at two different concentrations started 24 h before UVB exposure significantly increased the cell viability. The protective effect of CoQ10 was associated with reduction in superoxide, normalization of mitochondrial membrane potential, improvement of mitochondrial respiration, inhibition of cyto-c release, suppression of caspase-9. Furthermore, CoQ10 enhanced mitochondrial biogenesis. It is concluded that CoQ10 may protect astrocytes through suppression of oxidative stress, prevention of mitochondrial dysfunction, blockade of mitochondria-mediated cell death pathway, and enhancement of mitochondrial biogenesis.

The cyclic AMP effects and neuroprotective activities of PACAP and VIP in cultured astrocytes and neurons exposed to oxygen-glucose deprivation

BackgroundPituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are endogenous peptides, widely expressed in the central and peripheral nervous system. The adenylyl cyclase (AC)/cyclic AMP (cAMP) is their main intracellular signal transduction pathway. Numerous data suggest that PACAP and VIP have considerable neuroprotective potential, indicating the possibility for their use as new therapeutic strategies in stroke treatment. The aim of this study was to evaluate the effect of oxygen-glucose deprivation (OGD) – an established in vitro model for ischemic cell stress – on PACAP and VIP-evoked receptor-mediated cAMP generation in glial and neuronal cells, and to determine whether PACAP and VIP have neuroprotective activity under these conditions. MethodsThe formation of [3H]cAMP by PACAP, VIP and forskolin (a direct activator of AC) was measured in [3H]adenine prelabeled primary rat glial and neuronal cells under normoxia and OGD conditions. The effects of PACAP and VIP on cell viability were measured using the MTT conversion method, and were compared to tacrolimus (FK506), a well known neuroprotective agent. ResultsThe OGD model inhibited the PACAP and VIP-induced cAMP formation in rat astrocytes and neurons. Incubation of neuronal cells with PACAP prevented OGD-induced cell death, more efficiently than VIP and FK506. ConclusionThe obtained results showed that hypoxia/ischemia may trigger down-regulation of the brain AC-coupled PACAP/VIP receptors, with a consequent decrease of PACAP- and/or VIP-ergic-dependent cAMP-driven signaling. Moreover, our findings indicate that PACAP and VIP can prevent the deleterious effect of OGD on rat neuronal cells.

OPTIMIZATION OF SODIUM DODECYL SULPHATE AS A FORMAZAN SOLVENT AND COMPARISON OF 3-(4,-5-DIMETHYLTHIAZO-2-YL)-2,5-DIPHENYLTETRAZOLIUM BROMIDE (MTT) ASSAY WITH WST-1 ASSAY IN MCF-7 CELLS

A 3-(4,-5- dimethylthiazo -2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay is a method that used to measure cell viability. It is based on the conversion of MTT by succinic dehydrogenase enzyme into insoluble formazan. Dissolution of formazan by using proper solvent is the most important step of MTT assay to obtain valid and reliable data. In this study, we observed several solvents [isopropanol, dimethyl sulfoxide (DMSO), and sodium dodecyl sulphate (SDS)] to validate MTT assay by using MCF-7 cells. The observation was performed by MTT addition at concentration of 0.5µg/µL, 3-4h cells incubation at 37°C, dissolution of formed formazan crystal and absorbance measurement at 570nm. The result showed that formazan completely dissolved in DMSO and 10% SDS. The most advantage of using SDS was it avoided the removal of partially dissolved formazan. In this observation, we also found that pH was a very important factor in SDS solution that affected the reaction. The use of optimal condition on MTT assay by SDS-0.01M HCl and SDS-0.025M HCl as formazan solvents showed that IC 50 of curcumin were 32.3±0.78µM and 24.08±1.72µM respectively, while WST-1 assay resulted IC 50 of curcumin 80.69±5.35µM. Altogether, this study strongly indicated that SDS-0.01M HCl was the best formazan solvent for MTT assay.

In vitro release of dimethyloxaloylglycine and l-mimosine from bovine bone mineral

ObjectiveProlyl hydroxylases (PHD) are oxygen sensors and therefore pharmacological targets to stimulate periodontal regeneration. Here we evaluate the release profile of the PHD inhibitors dimethyloxaloylglycine and l-mimosine from bone substitutes. MaterialsDimethyloxaloylglycine and l-mimosine were lyophilised onto bone substitutes including bovine bone mineral, beta-tricalcium phosphate, and hydroxyapatite. Release kinetic was evaluated by bioassays with gingival and periodontal ligament fibroblasts. We determined the capacity of PHD inhibitors to provoke VEGF expression and to repress metabolic activity and proliferation as assessed by immunoassay, MTT conversion and 3[H]thymidine incorporation, respectively. ResultsWe found that the PHD inhibitors are released from bovine bone mineral as indicated by the increase of VEGF production in gingival and periodontal ligament fibroblasts. Supernatants obtained after 1h also decreased metabolic activity and proliferation of the fibroblasts. A fibrin matrix prolonged the release of PHD inhibitors up to 192h. A similar cellular response was found when supernatants from PHD inhibitors loaded beta-tricalcium phosphate and hydroxyapatite embedded in fibrin were assessed. ConclusionsIn conclusion bone substitutes can serve as carriers for PHD inhibitors that maintain their capacity to provoke a pro-angiogenic response in vitro. These findings provide the basis for preclinical studies to evaluate if this release kinetic can stimulate periodontal regeneration.

Comparative study of osteogenic differentiation potential of mesenchymal stem cells derived from bone marrow and adipose tissue of osteoporotic female rats

Osteoporosis causes reduction of osteogenic differentiation of mesenchymal stem cells (MSCs) from bone marrow and adipose tissue. This study was designed to compare the osteogenic potential of bone marrow mesenchymal stem cells (BMMSCs) and adipose-derived stem cells (ADSCs) of ovariectomized (OVX) rats. MSC were harvested from bone marrow and inguinal fat pads of six OVX rats. The limitations of this report are that cells from different animals were pooled for the purpose of the experiments that were carried out in this study. At 7, 14 and 21 d of osteogenic differentiation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion, alkaline phosphatase activity and gene expression for collagen I, osteocalcin, bone sialoprotein, osteopontin and bone morphogenetic protein-2 bone morphogenetic protein-2 (BMP-2) were analyzed. At 21 d, percentage of cells per field and percentage of mineralized nodule were analyzed. The data were subjected to analysis of variance, and the means were compared by Student–Newman–Keuls test. The cells, regardless of group, showed phenotypic characteristics consistent with stem cells. MTT conversion, alkaline phosphatase activity, percentage of mineralized nodule and expression of collagen I, osteocalcin and BMP-2 of ADSCs from OVX rats were higher when compared to BMMSCs from OVX rats in at least one of the evaluated periods (p < 0.05). However, bone sialoprotein and osteopontin expression were smaller than those observed in BMMSCs for all evaluated periods (p < 0.05). It was concluded that the ADSCs from OVX rats have higher osteogenic potential when compared to BMMSCs from OVX rats. This result suggests that the treatment of osteoporosis with autologous ADSCs may be more efficient.

Human Krüppel-related 3 (HKR3) Is a Novel Transcription Activator of Alternate Reading Frame (ARF) Gene

HKR3 (Human Krüppel-related 3) is a novel POK (POZ-domain Krüppel-like zinc-finger) family transcription factor. Recently, some of the POK (POZ-domain Krüppel-like zinc finger) family proteins have been shown to play roles in cell cycle arrest, apoptosis, cell proliferation, and oncogenesis. We investigated whether HKR3, an inhibitor of cell proliferation and an uncharacterized POK family protein, could regulate the cell cycle by controlling expression of genes within the p53 pathway (ARF-MDM2-TP53-p21WAF/CDKN1A). HKR3 potently activated the transcription of the tumor suppressor gene ARF by acting on the proximal promoter region (bp, -149∼+53), which contains Sp1 and FBI-1 binding elements (FREs). HKR3 interacted with the co-activator p300 to activate ARF transcription, which increased the acetylation of histones H3 and H4 within the proximal promoter. Oligonucleotide pull-down assays and ChIP assays revealed that HKR3 interferes with the binding of the proto-oncogenic transcription repressor FBI-1 to proximal FREs, thus derepressing ARF transcription.

A Novel Three-Dimensional Large-Pore Mesoporous Carbon Matrix as a Potential Nanovehicle for the Fast Release of the Poorly Water-soluble Drug, Celecoxib

A novel mesocellular carbon foam (MSU-FC) with a large pore size and a three-dimensional porous structure for the oral delivery of poorly water-soluble drugs was prepared. The goal of this study was to improve in vitro dissolution and in vivo absorption of celecoxib (CEB), a model drug, by means of novel carbon-based nanoparticles prepared from the MSU-FC matrix. The MSU-FC matrix was synthesized by an inverse replica templating method using mesocellular silica template. A solvent immersion/evaporation method was used to load the drug molecules. The drug-loaded nanoparticles were characterized for morphology, surface area, particle size, mesoporous structure, crystallinity, solubility and dissolution. The effect of MSU-FC on cell viability was measured using the MTT conversion assay. Furthermore, the oral bioavailability of CEB-loaded MSU-FC in fasted rats was compared with that of the marketed product. Our results demonstrate that CEB incorporation into the prepared MSU-FC resulted in an approximately 9-fold increase in aqueous solubility in comparison with crystalline CEB. MSU-FC produced accelerated immediate release of CEB in comparison with crystalline CEB (pure CEB powder or marketed formulation) and the drug-loaded conventional mesoporous carbon particles. The relative bioavailability of CEB for CEB-loaded MSU-FC was 172%. In addition, MSU-FC nanoparticles exhibited very low toxicity. The MSU-FC nanomatrix has been shown to be a promising drug delivery vehicle for improving the dissolution and biopharmaceutical characteristics of poorly water-soluble drugs.

Unraveling the Mechanisms Behind the Enhanced MTT Conversion by Irradiated Breast Cancer Cells

Previously, we described the radiation-induced (RI) 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) effect as the increased MTT metabolization at the intermediate dose region after the irradiation of an MCF-7/6 cell monolayer with an X-ray dose gradient. We wondered if the cell monolayer at the intermediate dose region was characterized by an increased metabolic activity. In this study, we unraveled the mechanisms behind the RI MTT effect. Comparison of the MTT, sulforhodamine B (SRB), 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H tetrazolium (WST-8), and nitroblue tetrazolium (NBT) assays indicated that the RI MTT effect is not due to an increased cell density, but to an exclusively intracellular MTT conversion. Our results for the MTT and NBT assays after digitonin pretreatment of the irradiated cell monolayer indicated a role of the plasma membrane permeability in the RI MTT effect. Assessment of the radiation impact on the oxidative phosphorylation system by Western blot analysis, spectrophotometric measurement and Blue Native gel electrophoresis showed a dose-dependent downregulation of the oxidative phosphorylation system complexes, whereby the radiosensitivity of each complex was proportional to the number of mitochondrial DNA-encoded subunits. Further, only treatment of the irradiated cell monolayer with a cocktail and not with the individual inhibitors of complexes I, II and IV during the MTT assay prevented the RI MTT effect. In general, our results demonstrate that the RI MTT effect is not due to an increased metabolic activity, but rather to an enhanced cellular MTT entry and mitochondrial MTT conversion.

Efeito in vitro da triiodotironina sob o potencial osteogênico reduzido de células-tronco mesenquimais do tecido adiposo de ratas ovariectomizadas e com osteoporose

To examine if triiodothyronine (T3) increases osteogenic differentiation adipose tissue derived stem cells (ASCs) from ovariectomized adult rats with osteoporosis compared with young rats and adult rats without osteoporosis. The ASCs were cultured in osteogenic medium and distributed into seven groups: 1) ASCs of young rats without osteoporosis; 2) ASCs of adult rats without osteoporosis; 3) ASCs of adult rats with osteoporosis and 4, 5, 6 and 7) ASCs of adult rats with osteoporosis treated with T3 (0.01 nM, 1 nM, 100 nM and 1,000 nM). We analyzed alkaline phosphatase activity, dimethylthiazol (MTT) conversion, percentage of mineralized nodules, cellularity and quantification of gene transcripts for collagen I, osteocalcin, osteopontin and Bmp-2. Regardless of the dose, T3 reduced the MTT conversion, alkaline phosphatase activity, percentage of cells and the expression of collagen I in at least one of the doses and periods studied (p < 0.05). But, the treatment with T3 does not modify the number of mineralized nodules and the expression of osteopontin and Bmp-2 in culture of ASCs from adult rats with osteoporosis (p > 0.05). T3 has a negative effect on some factors involved in osteogenic differentiation of ASCs from adult rats with osteoporosis, without; however, reduce the formation of mineralized nodules and the expression of bone proteins.

Triiodotironina não aumenta a diferenciação osteogênica reduzida pela idade de células-tronco mesenquimais da medula óssea de ratas

To examine if triiodothyronine (T3) increases osteogenic differentiation in bone marrow mesenchymal stem cells (BMMSCs) of adult rats compared with young rats. BMMSCs were cultured in osteogenic medium and distributed into six groups: 1) BMMSCs of young rats; 2) BMMSCs of adult rats; 3, 4, 5 and 6) BMMSCs of adult rats with T3 (0.01, 1, 100 to 1000 nM). We analyzed alkaline phosphatase activity, dimethylthiazol (MTT) conversion, and collagen synthesis at 7, 14, and 21 days, and percentage of cells per field and number of mineralized nodules at 21 days of differentiation. T3 reduced MTT conversion, alkaline phosphatase activity, collagen synthesis, and the synthesis of mineralizalized nodules in at least one of the doses and periods studied (p < 0.05). Values were lower when compared with young and adult rats BMMSCs (p < 0.05) without T3. T3 has a negative effect on the factors involved in osteogenic differentiation of BMMSC from adult rats.

LPS-induced iNOS expression in N9 microglial cells is suppressed by geniposide via ERK, p38 and nuclear factor-κB signaling pathways

Activated microglia producing reactive nitrogen species, inflammatory factors, reactive oxygen species (ROS) and other neurovirulent factors, can lead to the development of neurodegenerative diseases. Certain compounds can inhibit the activation of microglia. However, the mechanisms remain unclear. In the present study, we investigated the inhibitory effect of geniposide on the production of ROS and inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated N9 murine microglial cells through the p38, ERK1/2 and nuclear factor-κB (NF-κB) signaling pathways. After the N9 cells were pre-treated with the vehicle or geniposide and exposed to LPS for the time indicated, the MTT conversion test was used to assess cell viability. Suitable concentrations were chosen and adjusted according to the experiments. Extracellular nitric oxide (NO) release was measured by Griess reaction. The formation of ROS and intracellular NO was evaluated by fluorescence imaging. NOS activities were determined using commercially available kits. The morphology of the N9 cells was examined by hematoxylin and eosin staining. The expression of iNOS mRNA was examined by RT-PCR. The protein levels of iNOS, p38 mitogen-activated protein kinase (MAPK), ERK1/2 and NF-κB, inhibitory factor-κB-α (IκB-α) were determined by western blot analysis. The results showed that geniposide attenuated the activation of N9 cells and inhibited the overproduction of NO, intracellular ROS and the expression of iNOS induced by LPS in the cells. In addition, geniposide blocked the phosphorylation of p38, ERK1/2 and inhibited the drop-off of IκB induced by LPS in the cells. These data indicate that geniposide has therapeutic potential for the treatment of neurodegenerative diseases, and that it exerts its effects by inhibiting inflammation.

Aspartic acid substitutions in monoamine oxidase-A reveal both catalytic-dependent and -independent influences on cell viability and proliferation

Post-translational influences could underlie the ambiguous roles of monoamine oxidase-A (MAO-A) in pathologies such as depression, cancer and Alzheimer disease. In support of this, we recently demonstrated that the Ca²⁺-sensitive component of MAO-A catalytic activity is inhibited by a pro-survival p38 (MAPK)-dependent mechanism. We substituted three aspartic acid (D) residues in human MAO-A that reside in putative Ca²⁺-binding motifs and overexpressed the individual proteins in the human HEK293 cell line. We assayed the overexpressed proteins for catalytic activity and for their influence on cell viability (using MTT conversion and trypan blue exclusion) and proliferation/DNA synthesis [using bromodeoxyuridine (BrdU) incorporation]. Innate MAO-A catalytic activity (and the capacity for generating hydrogen peroxide) was unaffected by the D61A substitution, but inhibited moderately or completely by the D248A and D328G substitutions, respectively. The Ca²⁺-sensitive activities of wild-type and D248A MAO-A proteins were enhanced by treatment with the selective p38(MAPK) inhibitor, SB203580, but was completely abrogated by the D61A substitution. Monoamine oxidase-A(D61A) was toxic to cells and exerted no effect on cell proliferation, while MAO-A(D248A) was generally comparable to wild-type MAO-A. As expected, the catalytic-dead MAO-A(D328G) was not cytotoxic, but unexpectedly enhanced both MTT conversion and BrdU staining. Variant-dependent changes in Bax and Bcl-2/Bcl-XL protein expression were observed. A different pattern of effects in N2-a cells suggests cell line-dependent roles for MAO-A. A catalytic-dependent mechanism influences MAO-A-mediated cytotoxicity, whereas a catalytic-independent mechanism contributes to proliferation. Context-dependent inputs by either mechanism could underlie the ambiguous pathological contributions of MAO-A.

Physical activity improves age‐related decline in the osteogenic potential of rats' bone marrow‐derived mesenchymal stem cells

To examine whether physical activity increases osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) from adult rats compared with young rats. Eighteen female Wistar rats were divided into three groups and the following cells isolated: (1) differentiated BMMSCs from young donors, (2) differentiated BMMSCs from sedentary adult donors and (3) differentiated BMMSCs from active adult donors. We analysed MTT conversion, percentage of cells per field, mineralized nodule number and gene expression for telomerase reverse transcriptase (TERT), alkaline phosphatase, caspase 3, osteocalcin, bone sialoprotein and collagen I. Telomerase reverse transcriptase expression and the percentage of cells per field in BMMSCs cultures from adult rats were smaller than those observed in young donors. However, levels of caspase 3 expression were higher in BMMSCs from adult donors (P<0.05). Despite the fact that physical activity was associated with an increase in expression of caspase 3 (P<0.05), there was no difference in the percentage of cells per field between groups of adult BMMSCs (active or sedentary). However, physical activity increased the number of mineralized nodules and osteocalcin expression after 21days, and alkaline phosphatase expression at 7, 14 and 21days in the BMMSCs of adult donors (P<0.05). However, those values were smaller when compared with young donors BMMSCs (P<0.05). Only the expression levels of alkaline phosphatase were similar to young donors BMMSCs (P≥0.05). Physical activity increases osteogenic differentiation of BMMSCs from adult donors but does not increase the differentiation to the levels observed in BMMSCs from young donor rats.

Analysis of the p53 pathway in clear cell renal cell carcinoma to identify novel drug combinations.

460 Background: p53 is rarely mutated in clear cell renal cell carcinoma (ccRCC) with typical mutation frequencies between 0 and 5%. Recent studies have shown that combined p53/MDM2 expression is significantly linked with reduced survival (P&lt;0.0001, HR=3.2) and is an independent prognostic indicator (Cox multiple regression analysis, P=0.027). Studies have also found that p53 is negatively regulated by MDM2 in RCC cells but that rescue of p53 stability is not effective at inducing apoptosis. Studies of normal kidney have shown that signalling to p53 by genotoxic agents is intact, but fail to elicit an apoptotic response. We have therefore investigated a rational combinatorial approach to drug targeting in RCC cells in which both MDM2 is inhibited and apoptosis is stimulated. Methods: Senescence was quantitated by assaying SA-β-galactosidase. Drug sensitivity was determined by measuring MTT conversion at multiple time points. Data from these were used to generate isobolograms and combination indices. Further details of the drugs used will be presented. Results: Using a p53-MDM2 antagonist (currently in clinical trials), our results indicate that in RCC cells rescue of p53 induces some growth arrest and senescence but not apoptosis (IC70 range 7-30 μM). Similarly, using a pro-apoptotic drug (also in clinical trials) which has been demonstrated to promote apoptosis in a wide range of cells, we find little growth inhibitory effect (IC70 range 2.5-30 μM). However, combining a p53-MDM2 antagonist with the pro-apoptotic drug leads to dramatic synergy (combination indices as low as 0.26 [&lt;1 indicates synergy]) and rapid p53-dependent apoptosis in a range of p53 wild-type RCC cell lines. Crucially, the drug combinations have no impact on non-tumour renal cells (neither IC70 nor IC50 could be determined, but both exceed 30 μM) suggesting these may have a high therapeutic index. Conclusions: Rationally designed combinatorial approaches for the treatment of RCC can lead to dramatic enhancement of RCC cell sensitivity and clearly warrant further investigation in both pre-clinical studies (under development) and in clinical trials for RCC due to the retention of wild-type p53 in this disease.

Coenzyme Q10 Ameliorates Ultraviolet B Irradiation Induced Cell Death Through Inhibition of Mitochondrial Intrinsic Cell Death Pathway

Ultraviolet B (UVB) induces cell death by increasing free radical production, activating apoptotic cell death pathways and depolarizing mitochondrial membrane potential. Coenzyme Q10 (CoQ10), an essential cofactor in the mitochondrial electron transport chain, serves as a potent antioxidant in the mitochondria. The aim of the present study is to establish whether CoQ10 is capable of protecting neuronal cells against UVB-induced damage. Murine hippocampal HT22 cells were treated with 0.01, 0.1 or 1 μM of CoQ10 3 or 24 h prior to the cells being exposed to UVB irradiation. The CoQ10 concentrations were maintained during irradiation and 24 h post-UVB. Cell viability was assessed by counting viable cells and MTT conversion assay. Superoxide production and mitochondrial membrane potential were measured using fluorescent probes. Levels of cleaved caspase-9, caspase-3, and apoptosis-inducing factor (AIF) were detected using immunocytochemistry and Western blotting. The results showed that UVB irradiation decreased cell viability and such damaging effect was associated with increased superoxide production, mitochondrial depolarization, and activation of caspase-9 and caspase-3. Treatment with CoQ10 at three different concentrations started 24 h before UVB exposure significantly increased the cell viability. The protective effect of CoQ10 was associated with reduction in superoxide production, normalization of mitochondrial membrane potential and inhibition of caspase-9 and caspase-3 activation. It is concluded that the neuroprotective effect of CoQ10 results from inhibiting oxidative stress and blocking caspase-3 dependent cell death pathway.

Phytosterol supplementation reduces metabolic activity and slows cell growth in cultured rat cardiomyocytes

Besides being cholesterol-lowering agents, phytosterols (PS) can inhibit the growth and development of tumours. The anti-neoplastic activity is accounted for by PS incorporation into cell membranes, resulting in the interference of membrane functionality. The similarity between the PS cholesterol-lowering and anti-neoplastic effective doses deserves attention on the possible adverse effects even in non-neoplastic cells. To date, few studies have addressed the clarification of this important issue. In the present study, we supplemented primary, non-neoplastic neonatal rat cardiomyocytes with two different PS concentrations (3 or 6 μg/ml), both within the range of human plasma concentration. Cardiac cells were chosen as an experimental model since the heart has been reported as the target organ for subchronic toxicity of PS. Following supplementation, a dose-dependent incorporation of PS and a decrease in cholesterol content were clearly evidenced. PS did not induce apoptosis but caused a reduction in metabolic activity (measured as 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion) and a slowing down of cell growth. The lower MTT conversion and the similar lactate dehydrogenase release could suggest that PS more efficiently target mitochondria than plasma membrane integrity. The replacement of cholesterol by PS could also have caused the observed slowing down of cell growth and the reduction in metabolic activity, which could rely on the PS increase, cholesterol decrease, or both. The present study is the first report on the effect of PS in cardiac cells, and although it is difficult to translate the obtained results to the health of heart tissue, it raises concerns about the safety of long-term exposure to physiologically relevant PS concentrations.

The role of Med19 in the proliferation and tumorigenesis of human hepatocellular carcinoma cells

To explore the role of Med19, a component of the Mediator complex that coactivates DNA-binding transcription factors, in the proliferation and tumorigenesis of human hepatocellular carcinoma cells. The human hepatocellular carcinoma cell lines HepG2 and Hep3B were infected with lentiviral vectors encoding interfering RNA (RNAi) targeting the Med19 gene. To further confirm the inhibitory effects of RNAi vectors on Med19 gene expression, quantitative real-time RT-PCR and Western blotting assays were used. The proliferation of HepG2 and Hep3B cells after transduction with the Med19-RNAi-Lentivirus vector was evaluated by MTT conversion, BrdU incorporation, colony formation, and cell-cycle assays in vitro. In addition, the ability of the Med19-RNAi-Lentivirus vector-infected Hep3B cells to form tumors after inoculation into nude mice was determined. Recombinant lentiviral vectors expressing small interfering RNA (siRNA) against Med19 were constructed and were found to efficiently downregulate Med19 mRNA and protein levels in HepG2 and Hep3B cells. Furthermore, the inhibition of Med19 by RNAi dramatically reduced hepatocellular carcinoma cell proliferation, induced cell-cycle arrest in the G(0)/G(1) phase, and suppressed tumor formation. These results provide new evidence of an important role for Med19 in the development of hepatocellular carcinomas, suggesting that lentivirus-mediated RNAi to target Med19 is a potential tool for inhibiting cancer cell proliferation and tumorigenesis.