Total Cellular Levels Research Articles

DHCR24 exerts neuroprotection upon inflammation-induced neuronal death.

BackgroundDHCR24, involved in the de novo synthesis of cholesterol and protection of neuronal cells against different stress conditions, has been shown to be selectively downregulated in neurons of the affected brain areas in Alzheimer’s disease.MethodsHere, we investigated whether the overexpression of DHCR24 protects neurons against inflammation-induced neuronal death using co-cultures of mouse embryonic primary cortical neurons and BV2 microglial cells upon acute neuroinflammation. Moreover, the effects of DHCR24 overexpression on dendritic spine density and morphology in cultured mature mouse hippocampal neurons and on the outcome measures of ischemia-induced brain damage in vivo in mice were assessed.ResultsOverexpression of DHCR24 reduced the loss of neurons under inflammation elicited by LPS and IFN-γ treatment in co-cultures of mouse neurons and BV2 microglial cells but did not affect the production of neuroinflammatory mediators, total cellular cholesterol levels, or the activity of proteins linked with neuroprotective signaling. Conversely, the levels of post-synaptic cell adhesion protein neuroligin-1 were significantly increased upon the overexpression of DHCR24 in basal growth conditions. Augmentation of DHCR24 also increased the total number of dendritic spines and the proportion of mushroom spines in mature mouse hippocampal neurons. In vivo, overexpression of DHCR24 in striatum reduced the lesion size measured by MRI in a mouse model of transient focal ischemia.ConclusionsThese results suggest that the augmentation of DHCR24 levels provides neuroprotection in acute stress conditions, which lead to neuronal loss in vitro and in vivo.

Mitoketoscins: Novel mitochondrial inhibitors for targeting ketone metabolism in cancer stem cells (CSCs)

Previous studies have now well-established that epithelial cancer cells can utilize ketone bodies (3-hydroxybutyrate and aceto-acetate) as mitochondrial fuels, to actively promote tumor growth and metastatic dissemination. The two critical metabolic enzymes implicated in this process are OXCT1 and ACAT1, which are both mitochondrial proteins. Importantly, over-expression of OXCT1 or ACAT1 in human breast cancer cells is sufficient to genetically drive tumorigenesis and/or lung metastasis, validating that they indeed behave as metabolic “tumor promoters”. Here, we decided to target these two enzymes, which give cancer cells the ability to recycle ketone bodies into Acetyl-CoA and, therefore, to produce increased ATP. Briefly, we used computational chemistry (in silico drug design) to select a sub-set of potentially promising compounds that spatially fit within the active site of these enzymes, based on their known 3D crystal structures. These libraries of compounds were then phenotypically screened for their effects on total cellular ATP levels. Positive hits were further validated by metabolic flux analysis. Our results indicated that four of these compounds effectively inhibited mitochondrial oxygen consumption. Two of these compounds also induced a reactive glycolytic phenotype in cancer cells. Most importantly, using the mammosphere assay, we showed that these compounds can be used to functionally inhibit cancer stem cell (CSC) activity and propagation. Finally, our molecular modeling studies directly show how these novel compounds are predicted to bind to the active catalytic sites of OXCT1 and ACAT1, within their Coenzyme A binding site. As such, we speculate that these mitochondrial inhibitors are partially mimicking the structure of Coenzyme A. Thus, we conclude that OXCT1 and ACAT1 are important new therapeutic targets for further drug development and optimization. We propose that this new class of drugs should be termed “mitoketoscins”, to reflect that they were designed to target ketone re-utilization and mitochondrial function.

Morin Inhibits Proliferation of SW480 Colorectal Cancer Cells by Inducing Apoptosis Mediated by Reactive Oxygen Species Formation and Uncoupling of Warburg Effect.

The study under investigation focuses on in vitro antiproliferative efficacy of the flavonoid morin and the mechanisms by which it inhibits the growth of colon cancer using SW480 colon cancer cells with emphasis on Warburg effect. It was found that the cell proliferation was significantly inhibited by morin in a dose and time dependent manner. Morin induced apoptosis that was correlated with increased levels of reactive oxygen species formation and loss of mitochondrial membrane potential of the cells. In addition, an increase in cleaved PARP, cleaved caspase 3, cleaved caspase 8, cleaved caspase 9 and Bax as well as a decrease in Bcl 2 was observed, indicating morin is inducing both intrinsic as well as extrinsic pathway of apoptosis. This was further confirmed by using downstream caspase 3 inhibitor which indicated that caspase 3 inhibition reduces morin induced cell death. Moreover, the impact of morin on over all energy status when determined in terms of total cellular ATP level showed a decline with low level of glucose uptake and Glut1 expression. The results indicate that morin exerts antiproliferative activity by inducing apoptosis and by reducing Warburg effect in the evaluated cell lines and provide preliminary evidence for its anticancer activity.

Dietary supplementation with acetyl-l-carnitine counteracts age-related alterations of mitochondrial biogenesis, dynamics and antioxidant defenses in brain of old rats

We previously reported the ability of dietary supplementation with acetyl-l-carnitine (ALCAR) to prevent age-related decreases of mitochondrial biogenesis in skeletal muscle and liver of old rats. Here, we investigate the effects of ALCAR supplementation in cerebral hemispheres and cerebellum of old rats by analyzing several parameters linked to mitochondrial biogenesis, mitochondrial dynamics and antioxidant defenses.We measured the level of the coactivators PGC-1α and PGC-1β and of the factors regulating mitochondrial biogenesis, finding an age-related decrease of PGC-1β, whereas PGC-1α level was unvaried. Twenty eight-month old rats supplemented with ALCAR for one and two months showed increased levels of both factors. Accordingly, the expression of the two transcription factors NRF-1 and TFAM followed the same trend of PGC-1β. The level of mtDNA, ND1 and the activity of citrate synthase, were decreased with aging and increased following ALCAR treatment. Furthermore, ALCAR counteracted the age-related increase of deleted mtDNA. We also analyzed the content of proteins involved in mitochondrial dynamics (Drp1, Fis1, OPA1 and MNF2) and found an age-dependent increase of MFN2 and of the long form of OPA1. ALCAR treatment restored the content of the two proteins to the level of the young rats. No changes with aging and ALCAR were observed for Drp1 and Fis1. ALCAR reduced total cellular levels of oxidized PRXs and counteracted the age-related decrease of PRX3 and SOD2.Overall, our findings indicate a systemic positive effect of ALCAR dietary treatment and a tissue specific regulation of mitochondrial homeostasis in brain of old rats. Moreover, it appears that ALCAR acts as a nutrient since in most cases its effects were almost completely abolished one month after treatment suspension. Dietary supplementation of old rats with this compound seems a valuable approach to prevent age-related mitochondrial dysfunction and might ultimately represent a strategy to delay age-associated negative consequences in mitochondrial homeostasis.

Folic Acid Impairs the Uptake of 5-Methyltetrahydrofolate in Human Umbilical Vascular Endothelial Cells.

Background:Adequate folate status supports endothelial structure and function. Folic acid (FA), an oxidized synthetic folate, which is present in the plasma of patients consuming fortified food or FA supplements, may impair cellular uptake of physiological, reduced folates. We studied the effect of FA on uptake of the dominant circulatory folate, 5-methyltetrahydrofolate (5MTHF) in endothelial cells.Methods and Results:For short-term effects of FA, primary human umbilical vein endothelial cells (HUVECs) were maintained in growth medium containing 200 nM 5MTHF and preincubated with 20 nM FA 10 minutes before the 5MTHF uptake assessment. For long-term effects, HUVECs were cultured for 3 passages in growth medium containing either 200 nM 5MTHF, or a combination of 100 nM 5MTHF and 100 nM FA. 5MTHF uptake was assessed after exposing cells to 200 nM [13C5]-5MTHF, after which intracellular [13C5]-5MTHF was quantified using liquid chromatography/tandem mass spectrometry. Acute FA exposure caused a 57% reduction in 5MTHF uptake compared with control conditions (51 ± 12 vs. 22 ± 7 fmol·min−1·mg−1 protein; P = 0.01). Long-term exposure to FA reduced 5MTHF uptake by 41% (51 ± 12 vs. 30 ± 11 fmol·min−1·mg−1 protein; P = 0.05) and reduced total cellular 5MTHF levels by 47 ± 21% in HUVEC (P = 0.02).Conclusion:Unmetabolized FA, which appears in the plasma after consumption of fortified food or FA supplements, may impair uptake of 5MTHF, the dominant bioactive form of folate, in HUVEC.

Abstract 963: Ovarian-dependent SSM2ucd mouse mammary carcinoma cells depend on Cyp3a11 epoxygenase activity for proliferation

Abstract Introduction: Silencing of the human cytochrome P450 (CYP) monooxygenase enzyme CYP3A4 in the ER+ MCF-7 tumor cell line inhibits tumor growth in the mammary fat pad, but the relative roles of tumor cell intrinsic CYPs vs. vascular/microenvironment CYPs remain to be determined and a syngeneic animal model is needed to answer this question. The SSM2ucd ovarian dependent mouse mammary carcinoma cell line forms a transplantable estrogen-receptor positive (ER+) mouse mammary tumor in which growth dependence on cell intrinsic CYPs may be tested in vitro and in vivo. The SSM2ucd cell line is derived from 129SvJ: homozygous Stat1-null female mice, which develop ER+ mammary tumors (1,2). Expression profiling of spontaneously arising mouse mammary carcinomas in a TP53 KO model revealed that the CYP3A4 ortholog Cyp3a11 is up-regulated in these tumors. Methods: Cyp3a11 bactosomes were used to assay for NADPH dependent biosynthesis of EETs from arachidonic acid using an LC-MS/MS method. siRNA silencing and CRISPR/Cas9 knock out of the Cyp3a11 exons 2 and 3 was performed and the cell lines were characterized for EET dependence using an MTT assay. The highly potent inhibitor and chemical probe of CYP epoxygenase activity, hexyl-benzyl-biguanide (HBB), was used to test dependence of SSM2ucd cells on CYP epoxygenase activity. Total cellular EETs in SSM2ucd cells exposed to HBB at the IC50were measured by the LC-MS/MS method. Results: Cyp3a11 was shown to have robust NADPH dependent epoxygenase activity, while SSM2ucd cells were EET dependent for growth. Silencing of Cyp3a11 was demonstrated to inhibit proliferation of the SSM2ucd cell line, which was partly abrogated by EETs. CRISPR/Cas9 knock out of the Cyp3a11 in the SSM2ucd cell line was performed and exon 2 and exon 3 deleted cell lines were derived. SSM2ucd Cyp3a11 knock out cell lines were more sensitive to EET-induced proliferation under serum free condition than control lines. HBB potently inhibits the SSM2ucd cell line in vitro (IC50=25 uM) and reduces total cellular EET levels in this cell line at IC50. These results suggest that we may see inhibitory activity of HBB in a syngeneic 129/SvJ tumor transplantation model. Conclusions: The Cyp3a11 gene can be silenced in the SSM2ucd cell line, without disrupting cell viability, allowing further study of the roles of EETs in mouse mammary carcinoma proliferation, survival and clonogenicity. The Cyp3a11 gene has been knocked out in the SSM2 ucd cell line, allowing in vitro and in vivo studies of the roles of Cyp3a11 in the growth of ovarian dependent mouse mammary carcinoma. 1. Breast Cancer Res. 2012 Jan 20;14(1):R16 2. PLoS One. 2015 Jun 15;10(6):e0129895] Citation Format: Zhijun Guo, Patrick McGrarrah, Ted Bebi, Ashley Mooneyham, Alejandra Osorio, Cesar Herrera, Victor Arrieta, Sebastian Mohar, Irwin Hernandez, Robert Klink, Robert Cardiff, David A. Potter. Ovarian-dependent SSM2ucd mouse mammary carcinoma cells depend on Cyp3a11 epoxygenase activity for proliferation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 963. doi:10.1158/1538-7445.AM2017-963

Ly6Chigh Monocytes Oscillate in the Heart During Homeostasis and After Myocardial Infarction-Brief Report.

Circadian regulation of neutrophil homeostasis affects myocardial infarction (MI) healing. It is unknown whether diurnal variations of monocyte counts exist in the heart and whether this affects their cardiac infiltration in response to MI. Murine blood and organs were harvested at distinct times of day and analyzed by flow cytometry. Ly6Chigh monocyte surface expression levels of chemokine receptors (CCR) were ≈2-fold higher at the beginning of the active phase, Zeitgeber Time (ZT) 13 compared with ZT5. This was because of enhanced receptor surface expression at ZT13, whereas no significant changes in total cellular protein levels were found. Most blood Ly6Chigh monocytes were CCR2high, whereas only a minority was CCR1high and CCR5high. We also found diurnal changes of classical monocyte blood counts in humans, being higher in the evening, while exhibiting enhanced CCR2 surface expression in the morning. In support of monocyte oscillations between blood and tissue, murine cardiac Ly6Chigh monocyte counts were highest at ZT13, accompanied by an upregulation of cardiac CC chemokine ligand 2 mRNA. Mice subjected to MI at ZT13 had an even higher upregulation of CCR2 surface expression on circulating monocytes compared with noninfarcted mice and more elevated cardiac CC chemokine ligand 2 protein expression and more pronounced Ly6Chigh monocyte infiltration compared with ZT5-infarcted mice. Concomitantly, CCR2 antagonism only inhibited the excessive cardiac Ly6Chigh monocyte infiltration after ZT13 MI but not ZT5 MI. CCR2 surface expression on Ly6Chigh monocytes changes in a time-of-day-dependent manner, which crucially affects cardiac monocyte recruitment after an acute ischemic event.

Forced expression of Wnt antagonists sFRP1 and WIF1 sensitizes chronic myeloid leukemia cells to tyrosine kinase inhibitors.

Chronic myeloid leukemia is a clonal myeloproliferative disorder that arises from the neoplastic transformation of the hematopoietic stem cell, in which the Wnt/β-catenin signaling pathway has been demonstrated to play an important role in disease progression. However, the role of Wnt signaling antagonists in therapy resistance and disease progression has not been fully investigated. We aimed to study the effects of Wnt/β-catenin pathway antagonists-secreted frizzled-related protein 1 and Wnt inhibitory factor 1-on resistance toward tyrosine kinase inhibitors in chronic myeloid leukemia. Response to tyrosine kinase inhibitors was analyzed in secreted frizzled-related protein 1 and Wnt inhibitory factor 1 stably transfected K562 cells. Experiments were repeated using a tetracycline-inducible expression system, confirming previous results. In addition, response to tyrosine kinase inhibitor treatment was also analyzed using the secreted frizzled-related protein 1 expressing, BCR-ABL positive MEG01 cell line, in the presence and absence of a secreted frizzled-related protein 1 inhibitor. Our data suggests that total cellular β-catenin levels decrease in the presence of secreted frizzled-related protein 1 and Wnt inhibitory factor 1, and a significant increase in cell death after tyrosine kinase inhibitor treatment is observed. On the contrary, when secreted frizzled-related protein 1 is suppressed, total β-catenin levels increase in the cell and the cells become resistant to tyrosine kinase inhibitors. We suggest that Wnt antagonists carry the potential to be exploited in designing new agents and strategies for the advanced and resistant forms of chronic myeloid leukemia.

Acute acinar pancreatitis blocks vesicle-associated membrane protein 8 (VAMP8)-dependent secretion, resulting in intracellular trypsin accumulation

Zymogen secretory granules in pancreatic acinar cells express two vesicle-associated membrane proteins (VAMP), VAMP2 and -8, each controlling 50% of stimulated secretion. Analysis of secretion kinetics identified a first phase (0-2 min) mediated by VAMP2 and second (2-10 min) and third phases (10-30 min) mediated by VAMP8. Induction of acinar pancreatitis by supramaximal cholecystokinin (CCK-8) stimulation inhibits VAMP8-mediated mid- and late-phase but not VAMP2-mediated early-phase secretion. Elevation of cAMP during supramaximal CCK-8 mitigates third-phase secretory inhibition and acinar damage caused by the accumulation of prematurely activated trypsin. VAMP8-/- acini are resistant to secretory inhibition by supramaximal CCK-8, and despite a 4.5-fold increase in total cellular trypsinogen levels, are fully protected from intracellular trypsin accumulation and acinar damage. VAMP8-mediated secretion is dependent on expression of the early endosomal proteins Rab5, D52, and EEA1. Supramaximal CCK-8 (60 min) caused a 60% reduction in the expression of D52 followed by Rab5 and EEA1 in isolated acini and in in vivo The loss of D52 occurred as a consequence of its entry into autophagic vacuoles and was blocked by lysosomal cathepsin B and L inhibition. Accordingly, adenoviral overexpression of Rab5 or D52 enhanced secretion in response to supramaximal CCK-8 and prevented accumulation of activated trypsin. These data support that acute inhibition of VAMP8-mediated secretion during pancreatitis triggers intracellular trypsin accumulation and loss of the early endosomal compartment. Maintaining anterograde endosomal trafficking during pancreatitis maintains VAMP8-dependent secretion, thereby preventing accumulation of activated trypsin.

The immunoproteasome is induced by cytokines and regulates apoptosis in human islets.

In addition to degrading misfolded and damaged proteins, the proteasome regulates the fate of cells in response to stress. The role of the proteasome in pro-inflammatory cytokine-induced human beta-cell apoptosis is unknown. Using INS-1, INS-1E and human islets exposed to combinations of IFNγ, IL-1β and TNFα with or without addition of small molecules, we assessed the role of the immunoproteasome in pancreatic beta-cell demise. Here, we show that cytokines induce the expression and activity of the immuno-proteasome in INS-1E cells and human islets. Cytokine-induced expression of immuno-proteasome subunits, but not activity, depended upon histone deacetylase 3 activation. Inhibition of JAK1/STAT1 signaling did not affect proteasomal activity. Inhibition of the immuno-proteasome subunit PSMB8 aggravated cytokine-induced human beta-cell apoptosis while reducing intracellular levels of oxidized proteins in INS-1 cells. While cytokines increased total cellular NFκB subunit P50 and P52 levels and reduced the cytosolic NFκB subunit P65 and IκB levels, these effects were unaffected by PSMB8 inhibition. We conclude that beta cells upregulate immuno-proteasome expression and activity in response to IFNγ, likely as a protective response to confine inflammatory signaling.

H2S-induced S-sulfhydration of lactate dehydrogenase a (LDHA) stimulates cellular bioenergetics in HCT116 colon cancer cells

Cystathionine-β-synthase (CBS) is upregulated and hydrogen sulfide (H2S) production is increased in colon cancer cells. The functional consequence of this response is stimulation of cellular bioenergetics and tumor growth and proliferation. Lactate dehydrogenase A (LDHA) is also upregulated in various colon cancer cells and has been previously implicated in tumor cell bioenergetics and proliferation. In the present study, we sought to determine the potential interaction between the H2S pathway and LDH activity in the control of bioenergetics and proliferation of colon cancer, using the colon cancer line HCT116. Low concentrations of GYY4137 (a slow-releasing H2S donor) enhanced mitochondrial function (oxygen consumption, ATP production, and spare respiratory capacity) and glycolysis in HCT116 cells. SiRNA-mediated transient silencing of LDHA attenuated the GYY4137-induced stimulation of mitochondrial respiration, but not of glycolysis. H2S induced the S-sulfhydration of Cys163 in recombinant LDHA, and stimulated LDHA activity. The H2S-induced stimulation of LDHA activity was absent in C163A LDHA. As shown in HCT116 cell whole extracts, in addition to LDHA activation, GYY4137 also stimulated LDHB activity, although to a smaller extent. Total cellular lactate and pyruvate measurements showed that in HCT116 cells LDHA catalyzes the conversion of pyruvate to lactate. Total cellular lactate levels were increased by GYY4137 in wild-type cells (but not in cells with LDHA silencing). LDHA silencing sensitized HCT116 cells to glucose oxidase (GOx)-induced oxidative stress; this was further exacerbated with GYY4137 treatment. Treatment with low concentrations of GYY4137 (0.3mM) or GOx (0.01U/ml) significantly increased the proliferation rate of HCT116 cells; the effect of GOx, but not the effect of GYY4137 was attenuated by LDHA silencing. The current report points to the involvement of LDHA in the stimulatory effect of H2S on mitochondrial respiration in colon cancer cells and characterizes some of the functional interactions between LDHA and H2S-stimulated bioenergetics under resting conditions, as well as during oxidative stress.

Abnormal glycosylation in Joubert syndrome type 10

BackgroundThe discovery of disease pathogenesis requires systematic agnostic screening of multiple homeostatic processes that may become deregulated. We illustrate this principle in the evaluation and diagnosis of a 5-year-old boy with Joubert syndrome type 10 (JBTS10). He carried the OFD1 mutation p.Gln886Lysfs*2 (NM_003611.2: c.2656del) and manifested features of Joubert syndrome.MethodsWe integrated exome sequencing, MALDI-TOF mass spectrometry analyses of plasma and cultured dermal fibroblasts glycomes, and full clinical evaluation of the proband. Analyses of cilia formation and lectin staining were performed by immunofluorescence. Measurement of cellular nucleotide sugar levels was performed with high-performance anion-exchange chromatography with pulsed amperometric detection. Statistical analyses utilized the Student’s and Fisher’s exact t tests.ResultsGlycome analyses of plasma and cultured dermal fibroblasts identified abnormal N- and O-linked glycosylation profiles. These findings replicated in two unrelated males with OFD1 mutations. Cultured fibroblasts from affected individuals had a defect in ciliogenesis. The proband’s fibroblasts also had an abnormally elevated nuclear sialylation signature and increased total cellular levels of CMP-sialic acid. Ciliogenesis and each glycosylation anomaly were rescued by expression of wild-type OFD1.ConclusionsThe rescue of ciliogenesis and glycosylation upon reintroduction of WT OFD1 suggests that both contribute to the pathogenesis of JBTS10.

Adaptor protein-3: A key player in RBL-2H3 mast cell mediator release.

Mast cell (MC) secretory granules are Lysosome-Related Organelles (LROs) whose biogenesis is associated with the post-Golgi secretory and endocytic pathways in which the sorting of proteins destined for a specific organelle relies on the recognition of sorting signals by adaptor proteins that direct their incorporation into transport vesicles. The adaptor protein 3 (AP-3) complex mediates protein trafficking between the trans-Golgi network (TGN) and late endosomes, lysosomes, and LROs. AP-3 has a recognized role in LROs biogenesis and regulated secretion in several cell types, including many immune cells such as neutrophils, natural killer cells, and cytotoxic T lymphocytes. However, the relevance of AP-3 for these processes in MCs has not been previously investigated. AP-3 was found to be expressed and distributed in a punctate fashion in rat peritoneal mast cells ex vivo. The rat MC line RBL-2H3 was used as a model system to investigate the role of AP-3 in mast cell secretory granule biogenesis and mediator release. By immunofluorescence and immunoelectron microscopy, AP-3 was localized both to the TGN and early endosomes indicating that AP-3 dependent sorting of proteins to MC secretory granules originates in these organelles. ShRNA mediated depletion of the AP-3 δ subunit was shown to destabilize the AP-3 complex in RBL-2H3 MCs. AP-3 knockdown significantly affected MC regulated secretion of β-hexosaminidase without affecting total cellular enzyme levels. Morphometric evaluation of MC secretory granules by electron microscopy revealed that the area of MC secretory granules in AP-3 knockdown MCs was significantly increased, indicating that AP-3 is involved in MC secretory granule biogenesis. Furthermore, AP-3 knockdown had a selective impact on the secretion of newly formed and newly synthesized mediators. These results show for the first time that AP-3 plays a critical role in secretory granule biogenesis and mediator release in MCs.

Plasmalogen biosynthesis is spatiotemporally regulated by sensing plasmalogens in the inner leaflet of plasma membranes

Alkenyl ether phospholipids are a major sub-class of ethanolamine- and choline-phospholipids in which a long chain fatty alcohol is attached at the sn-1 position through a vinyl ether bond. Biosynthesis of ethanolamine-containing alkenyl ether phospholipids, plasmalogens, is regulated by modulating the stability of fatty acyl-CoA reductase 1 (Far1) in a manner dependent on the level of cellular plasmalogens. However, precise molecular mechanisms underlying the regulation of plasmalogen synthesis remain poorly understood. Here we show that degradation of Far1 is accelerated by inhibiting dynamin-, Src kinase-, or flotillin-1-mediated endocytosis without increasing the cellular level of plasmalogens. By contrast, Far1 is stabilized by sequestering cholesterol with nystatin. Moreover, abrogation of the asymmetric distribution of plasmalogens in the plasma membrane by reducing the expression of CDC50A encoding a β-subunit of flippase elevates the expression level of Far1 and plasmalogen synthesis without reducing the total cellular level of plasmalogens. Together, these results support a model that plasmalogens localised in the inner leaflet of the plasma membranes are sensed for plasmalogen homeostasis in cells, thereby suggesting that plasmalogen synthesis is spatiotemporally regulated by monitoring cellular level of plasmalogens.

Nuclear translocation of STAT3 and NF-κB are independent of each other but NF-κB supports expression and activation of STAT3

NF-κB and STAT3 are essential transcription factors in immunity and act at the interface of the transition from chronic inflammation to cancer. Different functional crosstalks between NF-κB and STAT3 have been recently described arguing for a direct interaction of both proteins. During a systematic analysis of NF-κB/STAT3 crosstalk we observed that appearance of the subcellular distribution of NF-κB and STAT3 in immunofluorescence heavily depends on the fixation procedure. Therefore, we established an optimized fixation protocol for the reliable simultaneous analysis of the subcellular distributions of both transcription factors. Using this protocol we found that cytokine-induced nuclear accumulation of NF-κB or STAT3 did not alter the subcellular distribution of the other transcription factor. Both knockout and overexpression of STAT3 does not have any major effect on canonical TNFα-NF-κB signalling in MEF or HeLa cells. Similarly, knockout of p65 did not alter nuclear accumulation of STAT3 in response to IL-6. However, p65 expression correlates with elevated total cellular levels of STAT3 and STAT1 and supports activation of these transcription factors. Our findings in MEF cells argue against a direct physical interaction of free cellular NF-κB and STAT3 but point to more intricate functional interactions.

Agent-Based Modeling of Mitochondria Links Sub-Cellular Dynamics to Cellular Homeostasis and Heterogeneity.

Mitochondria are semi-autonomous organelles that supply energy for cellular biochemistry through oxidative phosphorylation. Within a cell, hundreds of mobile mitochondria undergo fusion and fission events to form a dynamic network. These morphological and mobility dynamics are essential for maintaining mitochondrial functional homeostasis, and alterations both impact and reflect cellular stress states. Mitochondrial homeostasis is further dependent on production (biogenesis) and the removal of damaged mitochondria by selective autophagy (mitophagy). While mitochondrial function, dynamics, biogenesis and mitophagy are highly-integrated processes, it is not fully understood how systemic control in the cell is established to maintain homeostasis, or respond to bioenergetic demands. Here we used agent-based modeling (ABM) to integrate molecular and imaging knowledge sets, and simulate population dynamics of mitochondria and their response to environmental energy demand. Using high-dimensional parameter searches we integrated experimentally-measured rates of mitochondrial biogenesis and mitophagy, and using sensitivity analysis we identified parameter influences on population homeostasis. By studying the dynamics of cellular subpopulations with distinct mitochondrial masses, our approach uncovered system properties of mitochondrial populations: (1) mitochondrial fusion and fission activities rapidly establish mitochondrial sub-population homeostasis, and total cellular levels of mitochondria alter fusion and fission activities and subpopulation distributions; (2) restricting the directionality of mitochondrial mobility does not alter morphology subpopulation distributions, but increases network transmission dynamics; and (3) maintaining mitochondrial mass homeostasis and responding to bioenergetic stress requires the integration of mitochondrial dynamics with the cellular bioenergetic state. Finally, (4) our model suggests sources of, and stress conditions amplifying, cell-to-cell variability of mitochondrial morphology and energetic stress states. Overall, our modeling approach integrates biochemical and imaging knowledge, and presents a novel open-modeling approach to investigate how spatial and temporal mitochondrial dynamics contribute to functional homeostasis, and how subcellular organelle heterogeneity contributes to the emergence of cell heterogeneity.

Lipopolysaccharide inhibits colonic biotin uptake via interference with membrane expression of its transporter: a role for a casein kinase 2-mediated pathway.

Biotin (vitamin B7), an essential micronutrient for normal cellular functions, is obtained from both dietary sources as well as gut microbiota. Absorption of biotin in both the small and large intestine is via a carrier-mediated process that involves the sodium-dependent multivitamin transporter (SMVT). Although different physiological and molecular aspects of intestinal biotin uptake have been delineated, nothing is known about the effect of LPS on the process. We addressed this issue using in vitro (human colonic epithelial NCM460 cells) and in vivo (mice) models of LPS exposure. Treating NCM460 cells with LPS was found to lead to a significant inhibition in carrier-mediated biotin uptake. Similarly, administration of LPS to mice led to a significant inhibition in biotin uptake by native colonic tissue. Although no changes in total cellular SMVT protein and mRNA levels were observed, LPS caused a decrease in the fraction of SMVT expressed at the cell surface. A role for casein kinase 2 (CK2) (whose activity was also inhibited by LPS) in mediating the endotoxin effects on biotin uptake and on membrane expression of SMVT was suggested by findings that specific inhibitors of CK2, as well as mutating the putative CK2 phosphorylation site (Thr78Ala) in the SMVT protein, led to inhibition in biotin uptake and membrane expression of SMVT. This study shows for the first time that LPS inhibits colonic biotin uptake via decreasing membrane expression of its transporter and that these effects likely involve a CK2-mediated pathway.

Effects of Simvastatin on Expression of Multidrug Resistance Gene and Protein of SHI-1 Cells

To investigate the effects of simvastatin(SIM) and serum free medium(SFM) on the expression of multidrug resistance gene(MDR1) and protein of SHI-1 cells. Trypan blue exclusion assay was used to detect the proliferation level and viability of SHI-1 cells after treatment with SIM and culture in SFM; The multi-drug resistant protein p-gp was measured by flow cytometry after culture in SFM for 1 to 3 days and treatment with various concentration of simvastatin. The effect of SFM culture and SIM treatment on the expression of MDR1 trascript was detected by qPCR; ELISA was used to measure the change of cellular cholesterol after culture in SIM and SFM. Chemosensitivity assay was performed after treatment with SIM for SHI-1 cells. Compared with control group, the growth of SHI-1 cells cultured in SFM decreased in a time-dependent manner. The growth-inhibitory effect was markedly increased when SHI-1 cells were treated with SIM and SFM. The mRNA level of MDR1 gene decreased after SIM treatment or/and culture in SFM. P-gp protein was downregulated in SHI-1 cells cultured in SFM or/and treated with SIM. The cellular cholesterol level increased when the cells were cultured in SFM. Total cellular cholesterol level decreased in SHI-1 cells treated with SIM and cultured in SFM. Chemosensitivity assays found that pre-treatment with SIM could increase the cytotoxicity of DNR to SHI-1 cells. Culture with SIM and SFM can downregulate the expression of MDR1 gene and p-gp protein in SHI-1 cells. SIM also can enhance the chemotherapeutic sensitivity of SHI-1 cells.

Ceramide activates lysosomal cathepsin B and cathepsin D to attenuate autophagy and induces ER stress to suppress myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are immune suppressive cells that are hallmarks of human cancer. MDSCs inhibit cytotoxic T lymphocytes (CTLs) and NK cell functions to promote tumor immune escape and progression, and therefore are considered key targets in cancer immunotherapy. Recent studies determined a key role of the apoptosis pathways in tumor-induced MDSC homeostasis and it is known that ceramide plays a key role in regulation of mammalian cell apoptosis. In this study, we aimed to determine the efficacy and underlying molecular mechanism of ceramide in suppression of MDSCs. Treatment of tumor-bearing mice with LCL521, a lysosomotropic inhibitor of acid ceramidase, significantly decreased MDSC accumulation in vivo. Using a MDSC-like myeloid cell model, we determined that LCL521 targets lysosomes and increases total cellular C16 ceramide level. Although MDSC-like cells have functional apoptosis pathways, LCL521-induced MDSC death occurs in an apoptosis- and necroptosis-independent mechanism. LCL521 treatment resulted in an increase in the number of autophagic vesicles, heterolysosomes and swollen ERs. Finally, concomitant inhibition of cathepsin B and cathepsin D was required to significantly decrease LCL521-induced cell death. Our observations indicate that LCL521 targets lysosomes to activate cathepsin B and cathepsin D, resulting in interrupted autophagy and ER stress that culminates in MDSC death. Therefore, a ceramidase inhibitor is potentially an effective adjunct therapeutic agent for suppression of MDSCs to enhance the efficacy of CTL-based cancer immunotherapy.

Oroxylin A attenuates cigarette smoke-induced lung inflammation by activating Nrf2

Oroxylin A, a natural flavonoid isolated from the medicinal herb Scutellaria baicalensis Georgi, has been reported to have anti-inflammatory and antioxidant properties. However, the effect of oroxylin A on cigarette smoke (CS)-induced lung inflammation remains unclear. In this study, the ability of oroxylin A to protect against CS-induced lung inflammation was detected in vivo and in vitro. Oroxylin A was administered intraperitoneally to mice 2h prior CS exposure every day for five consecutive days. BEAS-2B bronchial epithelial cells and RAW264.7 cells were used to investigate the molecular mechanism of oroxylin A in vitro. In vivo, the results showed that oroxylin A dose-dependently attenuated CS-induced lung histopathologic changes, expression of cytokines TNF-α, IL-1β, and MCP-1, and levels of oxidative biomarkers 3-nitrotyrosine and 8-isoprostane. Meanwhile, oroxylin A up-regulated GSH level and glutathione reductase (GR) activity in lung tissues. In vitro, oroxylin A significantly up-regulated Nrf2 expression and total cellular glutathione level in cigarette smoke extract (CSE)-stimulated cells. In addition, oroxylin A promoted Nrf2 binding to antioxidant response element (ARE) and up-regulated ARE-regulated gene such as heme oxygenase-1 (HO-1), GPx, and GR in CSE-stimulated cells. Oroxylin A could protect both epithelial cells and macrophages from damage by cigarette smoke in vitro. Taken together, these data indicated that oroxylin A attenuated oxidative stress and lung inflammation induced by CS via activating Nrf2 signaling pathway. Oroxylin A may be a protective agent against CS-induced lung inflammation and chronic obstructive pulmonary disease.