Intracellular ATP Levels (intracellular + atp_level)

Distribution by Scientific Domains

Selected Abstracts

Enhanced IFN, production in adenosine-treated CHOCells: A mechanistic study

William P. K. Chong
Abstract Adenosine causes growth arrest in recombinant mammalian cell cultures, which results in enhanced productivity of the recombinant protein. Adenosine is also known to increase intracellular ATP level when added to mammalian cells. As a cell's energy level affects its protein expression capacity, we investigated the factors that contribute to the increase in recombinant protein productivity. Chinese hamster ovary (CHO) cells expressing human interferon-gamma (IFN,) were treated with 1 mM adenosine on Day 2 of culture. The growth arrest resulted in 60% reduction in integral viable cell density when compared with control. However, IFN, titer improved 1.4-fold alongside a 2.5-fold increase in average specific productivity. The adenosine-treated cells also experienced a two-fold increase in ATP level that sustained for 3 days. Western blot studies revealed a relatively short-lived but strong activation of the energy sensor AMP-activated protein kinase (AMPK) in adenosine-treated cells. Activation of AMPK was probably due to adenosine being temporarily converted to AMP. Activated AMPK should have down-regulated protein translation by preventing mammalian target of rapamycin (mTOR) from phosphorylating and inactivating 4E-binding protein 1 (4E-BP1), a key repressor of protein translation initiation. However, Western blots showed increased phosphorylation of 4E-BP1 on Day 2 that lasted 3 days. This implied that a high concentration of ATP could keep 4E-BP1 inhibited, probably by directly modulating mTOR. This corroborated with an earlier in vitro observation (Dennis et al., Science. 2001;294:1102-1105). Inhibition of translation initiation repression is thus likely to contribute in part to the improvement in IFN,-specific productivity and titer. 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Nitric oxide suppresses transforming growth factor-,1,induced epithelial-to-mesenchymal transition and apoptosis in mouse hepatocytes,

HEPATOLOGY, Issue 5 2009
Xinchao Pan
Nitric oxide (NO) is a multifunctional regulator that is implicated in various physiological and pathological processes. Here we report that administration of NO donor S-nitroso-N-acetylpenicillamine (SNAP) inhibited transforming growth factor-,1 (TGF-,1)-induced epithelial-to-mesenchymal transition (EMT) and apoptosis in mouse hepatocytes. Overexpression of inducible NO synthase (iNOS) by transfection of the iNOS-expressing vector, which increased NO production, also inhibited the TGF-,1-induced EMT and apoptosis in these cells. Treatment of cells with proinflammatory mediators, including tumor necrosis factor (TNF)-,, interleukin (IL)-1,, and interferon (IFN)-,, which increased the endogenous NO production, produced the same inhibitory effect. Furthermore, exogenous NO donor SNAP treatment caused a decrease in the intracellular adenosine triphosphate (ATP) levels. Consistently, depletion of intracellular ATP by mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) inhibited the TGF-,1-induced EMT and apoptosis, suggesting that an NO-induced decrease of ATP involved in the NO-mediated inhibition of TGF-,1-induced EMT and apoptosis. NO and FCCP also inhibited TGF-,1-induced STAT3 activation, suggesting that signal transducer and activator of transcription 3 inactivation is involved in the NO-induced effects on TGF-,1-induced EMT and apoptosis. Conclusion: Our study indicates that NO plays an important role in the inhibition of TGF-,1-induced EMT and apoptosis in mouse hepatocytes through the downregulation of intracellular ATP levels. The data provide an insight into the in vivo mechanisms on the function of NO during the processes of both EMT and apoptosis. (HEPATOLOGY 2009.) [source]

Improving cellular function through modulation of energy metabolism

D. Maes
The ambivalent consequences of mitochondrial stimulation on cellular activity have been well established. Mitochondria supply the cell with energy through a process of oxidative phosphorylation but thereby generate free radicals, resulting in the accumulation of hydrogen peroxide in the cytoplasm. We have investigated the impact of cellular senescence as well as UV irradiation, on the balance between these two activities. The adenosine triphosphate (ATP) level, DNA and protein synthesis in fibroblasts obtained from donors between 30 and 90 years of age appeared to be significantly influenced by the aging process. Both DNA and protein synthesis could be stimulated by increasing intracellular ATP levels. In-vitro senescent fibroblasts showed a reduction in the level of ATP as well as a shift in mitochondrial membrane potential. At the same time, there was an increase in intracellular hydrogen peroxide with increasing population doubling, indicating a clear dysfunction of the metabolic machinery in the mitochondria of senescent cells. To counteract this degradation of the energy pool, we treated cells with creatine, which is known to restore the pool of phosphocreatine in the mitochondria. Creatine treatment significantly increased cell survival after UV exposure, stimulated the repair of UVB-induced DNA damage in keratinocytes and caused a significant reduction in the number of sunburn cells in a UVB-exposed reconstituted skin model. These results clearly indicate that restoration of the energy pool in mitochondria increased cellular self-defense mechanism. These data show the important role played by the mitochondrial energy metabolism on the aging process, and indicate a possible therapy that can be used to counteract this negative effect. Treatment with creatine seems to provide the necessary boost to the cellular metabolism, which leads to an induction of a significant amount of protection and repair to human skin cells. [source]

Uncoupling protein 2 influences dopamine secretion in PC12h cells

Shigeru Yamada
Abstract Uncoupling protein 2 (UCP2) belongs to the UCP family, and is distributed in many organs including the brain. Although UCP2 is known to be related to many functions such as the regulation of insulin secretion or the scavenging of the radicals, the role of UCP2 in the central nervous system remains unclear. In this report, rat UCP2 (rUCP2) and its mutants were overexpressed in the PC12h cells to determine the physiological roles played by UCP2 in neural cells and to elucidate the mechanisms that regulate these functions. It was found that rUCP2 was activated by the stimulation of the cAMP-protein kinase A (PKA) cascade. Moreover, the activation of rUCP2 suppressed intracellular ATP levels and inhibited the cAMP-dependent increase of dopamine secretion. Thus, UCP2 appears to be regulated by the excitatory stimulus via the cAMP-PKA cascade and serves to negatively control the synaptic output by reducing intracellular ATP levels. [source]

Adenosine triphosphate-based chemotherapy response assay (ATP-CRA)-guided platinum-based 2-drug chemotherapy for unresectable nonsmall-cell lung cancer,

CANCER, Issue 9 2007
Yong Wha Moon MD
Abstract BACKGROUND. The study investigated correlations between adenosine triphosphate / chemotherapy response assay (ATP-CRA) and clinical outcomes after ATP-CRA-guided platinum-based chemotherapy for unresectable nonsmall-cell lung cancer (NSCLC). METHODS. The authors performed an in vitro chemosensitivity test, ATP-CRA, to evaluate the chemosensitivities of anticancer drugs such as cisplatin, carboplatin, paclitaxel, docetaxel, gemcitabine, and vinorelbine for chemonaive, unresectable NSCLC. The cell death rate was determined by measuring the intracellular ATP levels of drug-exposed cells compared with untreated controls. A sensitive drug was defined as a drug producing 30% or more reduction in ATP compared with untreated controls. Assay-guided platinum-based 2-drug chemotherapy was given to patients with pathologically confirmed NSCLC. RESULTS. Thirty-four patients were enrolled. Thirty tumor specimens were obtained by bronchoscopic biopsies and 4 obtained surgically. The median age was 61 years and 27 patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 0,1. The response rate was 43.8%. At a median follow-up period of 16.9 months, the median progression-free and overall survivals were 3.6 and 11.2 months, respectively. Patients were dichotomized into the platinum-sensitive (S; 20 patients) and resistant (R; 14 patients) groups. The positive/negative predictive values were 61.1% and 78.6% with a predictive accuracy of 68.8%. Although without significant differences in pretreatment parameters, the S-group showed better clinical response (P = .036), longer progression-free survival (P = .060), and longer overall survival (P = .025). CONCLUSIONS. Despite using bronchoscopic biopsied specimens, ATP-CRA and clinical outcomes correlated well after assay-guided platinum-based 2-drug chemotherapy for unresectable NSCLC. There was a favorable response and survival in the platinum-sensitive vs resistant groups. Cancer 2007. 2007 American Cancer Society. [source]