Development and progression of cancer is accompanied by marked changes in the expression and activity of enzymes involved in the cellular homeostasis of fatty acids. One class of enzymes that play a ...particularly important role in this process are the acetyl-CoA carboxylases (ACC). ACCs produce malonyl-CoA, an intermediate metabolite that functions as substrate for fatty acid synthesis and as negative regulator of fatty acid oxidation. Here, using the potent ACC inhibitor soraphen A, a macrocyclic polyketide from myxobacteria, we show that ACC activity in cancer cells is essential for proliferation and survival. Even at nanomolar concentrations, soraphen A can block fatty acid synthesis and stimulate fatty acid oxidation in LNCaP and PC-3M prostate cancer cells. As a result, the phospholipid content of cancer cells decreased, and cells stopped proliferating and ultimately died. LNCaP cells predominantly died through apoptosis, whereas PC-3M cells showed signs of autophagy. Supplementation of the culture medium with exogenous palmitic acid completely abolished the effects of soraphen A and rescued the cells from cell death. Interestingly, when added to cultures of premalignant BPH-1 cells, soraphen A only slightly affected cell proliferation and did not induce cell death. Together, these findings indicate that cancer cells have become dependent on ACC activity to provide the cell with a sufficient supply of fatty acids to permit proliferation and survival, introducing the concept of using small-molecule ACC inhibitors as therapeutic agents for cancer.
Tight control of storage and synthesis of glucose during nutritional transitions is essential to maintain blood glucose levels, a process in which the liver has a central role. PPARα is the master ...regulator of lipid metabolism during fasting, but evidence is emerging for a role of PPARα in balancing glucose homeostasis as well. By using PPARα ligands and PPARα−/− mice, several crucial genes were shown to be regulated by PPARα in a direct or indirect way. We here review recent evidence that PPARα contributes to the adaptation of hepatic carbohydrate metabolism during the fed-to-fasted or fasted-to-fed transition in rodents.
While the utility of cryopreserved human hepatocyte suspensions (CHHS) for
in vitro drug metabolism assays has been established, less is known about the effects of cryopreservation on transporter ...activity in human hepatocytes. In the present study, the activities of NTCP (sodium taurocholate co-transporting polypeptide;
SLC10A1), as well as of the hepatic OATP (organic anion transporting polypeptide;
SLCO gene family) and OCT (organic cation transporter;
SLC22A) isoforms were assessed in 14 individual and four pooled batches of CHHS. For comparative purposes, substrate accumulation rates were also measured in sandwich-cultured human hepatocytes.
In CHHS, the mean accumulation clearance of the NTCP substrate taurocholate (1
μM) was 27.5 (±15.0)
μl/min/million cells and decreased by 10-fold when extracellular sodium was replaced by choline. The accumulation clearance of digoxin and of the OATP substrates estrone-3-sulfate and estradiol-17β-
d-glucuronide (E
2-17β-G; 1
μM) amounted to 9.5 (±4.9), 99 (±67) and 5.2 (±2.6)
μl/min/million cells, respectively. Presence of the known OATP inhibitor rifampicin (25
μM) significantly (
p
<
0.01) decreased the accumulation of estrone-3-sulfate and E
2-17β-G to 48% and 70% of the control value, respectively, while no significant effect on digoxin accumulation was observed. The mean accumulation clearance of the OCT substrate 1-methyl-4-phenylpyridinium amounted to 19.8 (±10.9)
μl/min/million cells. Co-incubation with the OCT1 inhibitor prazosin (3
μM) and the OCT3 inhibitor corticosterone (1
μM) resulted in a significant (
p
<
0.01) decrease to 72% and 85% of the accumulation in control conditions, respectively. Experiments in pooled CHHS generally showed accumulation values that were comparable with the mean of the individual batches. A good correlation (
R
2
=
0.93) was observed between estrone-3-sulfate accumulation values and OATP1B3 mRNA levels, as determined in five batches of CHHS. Compared to substrate accumulation measured in sandwich-cultured human hepatocytes, accumulation values in CHHS were comparable (taurocholate and digoxin) to slightly higher (estrone-3-sulfate). Our data indicate that cryopreserved human hepatocyte suspensions are a reliable
in vitro model to study transporter-mediated substrate uptake in the liver. Systematic characterization of multiple batches of CHHS for transporter activity supports rational selection of human hepatocytes for specific applications.
Tight control of storage and synthesis of glucose during nutritional transitions is essential to maintain blood glucose levels, a process in which the liver has a central role. PPAR is the master ...regulator of lipid metabolism during fasting, but evidence is emerging for a role of PPAR in balancing glucose homeostasis as well. By using PPAR ligands and PPAR mice, several crucial genes were shown to be regulated by PPAR in a direct or indirect way. We here review recent evidence that PPAR contributes to the adaptation of hepatic carbohydrate metabolism during the fed-to-fasted or fasted-to-fed transition in rodents.
Transition-metal-free oxides were studied as heterogeneous catalysts for the sustainable epoxidation of alkenes with aqueous H₂O₂ by means of high throughput experimentation (HTE) techniques. A ...full-factorial HTE approach was applied in the various stages of the development of the catalysts: the synthesis of the materials, their screening as heterogeneous catalysts in liquid-phase epoxidation and the optimisation of the reaction conditions. Initially, the chemical composition of transition-metal-free oxides was screened, leading to the discovery of gallium oxide as a novel, active and selective epoxidation catalyst. On the basis of these results, the research line was continued with the study of structured porous aluminosilicates, gallosilicates and silica-gallia composites. In general, the gallium-based materials showed the best catalytic performances. This family of materials represents a promising class of heterogeneous catalysts for the sustainable epoxidation of alkenes and offers a valid alternative to the transition-metal heterogeneous catalysts commonly used in epoxidation. High throughput experimentation played an important role in promoting the development of these catalytic systems.
The intermolecular amination of alcohols was performed with ruthenium (Ru3+) immobilized on a calcium hydroxyapatite support. No additional base additives were necessary, nor did the catalyst require ...base treatment prior to reaction. High conversions were obtained with different amine and alcohol reactants.
The tight interrelationship between peroxisomes and mitochondria is illustrated by their cooperation in lipid metabolism, antiviral innate immunity and shared use of proteins executing organellar ...fission. In addition, we previously reported that disruption of peroxisome biogenesis in hepatocytes severely impacts on mitochondrial integrity, primarily damaging the inner membrane. Here we investigated the molecular impairments of the dysfunctional mitochondria in hepatocyte selective Pex5 knockout mice. First, by using blue native electrophoresis and in-gel activity stainings we showed that the respiratory complexes were differentially affected with reduction of complexes I and III and incomplete assembly of complex V, whereas complexes II and IV were normally active. This resulted in impaired oxygen consumption in cultured Pex5−/− hepatocytes. Second, mitochondrial DNA was depleted causing an imbalance in the expression of mitochondrial- and nuclear-encoded subunits of the respiratory chain complexes. Third, mitochondrial membranes showed increased permeability and fluidity despite reduced content of the polyunsaturated fatty acid docosahexaenoic acid. Fourth, the affected mitochondria in peroxisome deficient hepatocytes displayed increased oxidative stress. Acute deletion of PEX5 in vivo using adeno-Cre virus phenocopied these effects, indicating that mitochondrial perturbations closely follow the loss of functional peroxisomes in time. Likely to compensate for the functional impairments, the volume of the mitochondrial compartment was increased several folds. This was not driven by PGC-1α but mediated by activation of PPARα, possibly through c-myc overexpression. In conclusion, loss of peroxisomal metabolism in hepatocytes perturbs the mitochondrial inner membrane, depletes mitochondrial DNA and causes mitochondrial biogenesis independent of PGC-1α.
•Peroxisome deficiency in murine hepatocytes causes respiratory chain impairments.•Mitochondrial-encoded subunits and mitochondrial DNA are depleted.•Aberrant mitochondria have altered membrane properties and increased redox state.•The mitochondrial compartment is enlarged but not through PGC-1α.
The success of chemotherapy in cancer treatment is limited by scarce drug delivery to the tumor and severe side-toxicity. Prolyl hydroxylase domain protein 2 (PHD2) is an oxygen/redox-sensitive ...enzyme that induces cellular adaptations to stress conditions. Reduced activity of PHD2 in endothelial cells normalizes tumor vessels and enhances perfusion. Here, we show that tumor vessel normalization by genetic inactivation of Phd2 increases the delivery of chemotherapeutics to the tumor and, hence, their antitumor and antimetastatic effect, regardless of combined inhibition of Phd2 in cancer cells. In response to chemotherapy-induced oxidative stress, pharmacological inhibition or genetic inactivation of Phd2 enhances a hypoxia-inducible transcription factor (HIF)-mediated detoxification program in healthy organs, which prevents oxidative damage, organ failure, and tissue demise. Altogether, our study discloses alternative strategies for chemotherapy optimization.
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► Combined loss of Phd2 in stromal and cancer cells sensitizes tumors to chemotherapy ► Loss of Phd2 protects healthy organs against chemotherapy-induced oxidative damage ► Loss of Phd2 in healthy organs unleashes a HIF-mediated anti-oxidative response
Zn–Co double metal cyanide (DMC) materials are effective heterogeneous catalysts for intermolecular hydroaminations. Using the reaction of 4-isopropylaniline with phenylacetylene as a test, the ...effect of different catalyst synthesis procedures on the catalytic performance is examined. The best activities are observed for double metal cyanides with a cubic structure and prepared with a Zn2+ excess, and for nanosized particles prepared via a reverse emulsion synthesis. Detailed study of the active Zn2+ sites in the cubic material by EXAFS gives evidence for coordinative vacancies around the Zn, with four cyanide ligands in close proximity of the Zn. The substrate scope of the hydroaminations was successfully expanded to both aromatic and aliphatic alkynes and other aromatic and aliphatic amines. Even with styrenes the reaction proceeded with aromatic amines. The DMC catalysts are truly heterogeneous, possess a high thermal stability and are perfectly reusable.
We performed a whole-transcriptome analysis of miconazole-treated Candida albicans biofilms, using RNA-sequencing. Our aim was to identify molecular pathways employed by biofilm cells of this ...pathogen to resist action of the commonly used antifungal miconazole. As expected, genes involved in sterol biosynthesis and genes encoding drug efflux pumps were highly induced in biofilm cells upon miconazole treatment. Other processes were affected as well, including the electron transport chain (ETC), of which eight components were transcriptionally downregulated. Within a diverse set of 17 inhibitors/inducers of the transcriptionally affected pathways, the ETC inhibitors acted most synergistically with miconazole against C. albicans biofilm cells. Synergy was not observed for planktonically growing C. albicans cultures or when biofilms were treated in oxygen-deprived conditions, pointing to a biofilm-specific oxygen-dependent tolerance mechanism. In line, a correlation between miconazole's fungicidal action against C. albicans biofilm cells and the levels of superoxide radicals was observed, and confirmed both genetically and pharmacologically using a triple superoxide dismutase mutant and a superoxide dismutase inhibitor N-N'-diethyldithiocarbamate, respectively. Consequently, ETC inhibitors that result in mitochondrial dysfunction and affect production of reactive oxygen species can increase miconazole's fungicidal activity against C. albicans biofilm cells.
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