Erlotinib combination with a mitochondria-targeted ubiquinone effectively suppresses pancreatic cancer cell survival

BACKGROUND Pancreatic cancer is a leading cause of cancer-related deaths.Increased activity of the epidermal growth factor receptor(EGFR)is often observed in pancreatic cancer,and the small molecule EGFR inhibitor erlotinib has been approved for pancreatic cancer therapy by the food and drug administration.Nevertheless,erlotinib alone is ineffective and should be combined with other drugs to improve therapeutic outcomes.We previously showed that certain receptor tyrosine kinase inhibitors can increase mitochondrial membrane potential(Δψm),facilitate tumor cell uptake ofΔψm-sensitive agents,disrupt mitochondrial homeostasis,and subsequently trigger tumor cell death.Erlotinib has not been tested for this effect.AIM To determine whether erlotinib can elevateΔψm and increase tumor cell uptake ofΔψm-sensitive agents,subsequently triggering tumor cell death.METHODSΔψm-sensitive fluorescent dye was used to determine how erlotinib affectsΔψm in pancreatic adenocarcinoma(PDAC)cell lines.The viability of conventional and patient-derived primary PDAC cell lines in 2D-and 3D cultures was measured after treating cells sequentially with erlotinib and mitochondria-targeted ubiquinone(MitoQ),aΔψm-sensitive MitoQ.The synergy between erlotinib and MitoQ was then analyzed using SynergyFinder 2.0.The preclinical efficacy of the twodrug combination was determined using immune-compromised nude mice bearing PDAC cell line xenografts.RESULTS Erlotinib elevatedΔψm in PDAC cells,facilitating tumor cell uptake and mitochondrial enrichment ofΔψm-sensitive agents.MitoQ triggered caspase-dependent apoptosis in PDAC cells in culture if used at high doses,while erlotinib pretreatment potentiated low doses of MitoQ.SynergyFinder suggested that these drugs synergistically induced tumor cell lethality.Consistent with in vitro data,erlotinib and MitoQ combination suppressed human PDAC cell line xenografts in mice more effectively than single treatments of each agent.CONCLUSION Our findings suggest that a combination of erlotinib and MitoQ has the potential to suppress pancreatic tumor cell viability effectively.

Protective Effect of Ubiquinone and Precursors of ItsSynthesis on Mitochondrial Respiratory Chain andActivity of Matrix Metalloproteinases in Animal Tissuesunder Effect of Doxorubicin

Mitochondrial dysfunction, oxidative stress, and their regulation are important fields of study in modem clinical research.Exogenous CoQ is an efficient therapeutic agent, yet its application has leads to continued suppression of endogenous CoQ synthesis,which limits CoQ applicability. Our aim was to study the state of mitochondrial electron transport chain components, CoQ contentand redox state, superoxide anion radicals and NO production rates, and active MMP-2 and MMP-9 content in rat liver and heartunder treatment with Doxorubicin, CoQ10, and complex preparation of modulators and precursors of CoQ biosynthesis （EPMcomplex）. The results demonstrate that treatment with EPM complex and CoQ10 in addition to Doxorubicin administration exertsprotective effect on liver and heart mitochondria, evidenced by restoration of electron transport in respiratory chain, which isexpressed as decreased nitrile complexes formation with Fe-S-proteins and increased ubisemiquinone content. The protective effectsof EPM complex on mitochondrial electron transport chain under Doxorubicin administration is on par with those of CoQ10, anddecreased MMP2 and MMP9 activities signify lessened extracellular matrix destruction. These results demonstrate the viability ofapproaches to correct adverse effects of Doxorubicin by treatment with CoQ10 and e complex of precursors and modulators of itsbiosynthesis.

cDNA cloning, functional expression and cellular localization of rat liver mitochondrial electron-transfer flavoprotein-ubiquinone oxidoreductase protein

A membrane-bound protein was purified from rat liver mitochondria. After being di-gested with V8 protease, two peptides containing identical 14 amino acid residue sequences were obtained. Using the 14 amino acid peptide derived DNA sequence as gene specific primer, the cDNA of correspondent gene 5′-terminal and 3′-terminal were obtained by RACE technique. The full-length cDNA that encoded a protein of 616 amino acids was thus cloned, which included the above mentioned peptide sequence. The full length cDNA was highly homologous to that of human ETF-QO, indicating that it may be the cDNA of rat ETF-QO. ETF-QO is an iron sulfur protein located in mitochondria inner membrane containing two kinds of redox center: FAD and [4Fe-4S] center. After comparing the sequence from the cDNA of the 616 amino acids protein with that of the mature protein of rat liver mitochondria, it was found that the N terminal 32 amino acid residues did not exist in the mature protein, indicating that the cDNA was that of ETF-QOp. When the cDNA was expressed in Saccharomyces cerevisiae with inducible vectors, the protein product was enriched in mitochondrial fraction and exhibited electron transfer activity (NBT re-ductase activity) of ETF-QO. Results demonstrated that the 32 amino acid peptide was a mito-chondrial targeting peptide, and both FAD and iron-sulfur cluster were inserted properly into the expressed ETF-QO. ETF-QO had a high level expression in rat heart, liver and kidney. The fu-sion protein of GFP-ETF-QO co-localized with mitochondria in COS-7 cells.

Roles of MT-ND1 in Cancer

The energy shift toward glycolysis is one of the hallmarks of cancer.Complex I is a vital enzyme complex necessary for oxidative phosphorylation.The mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 1(MT-ND1)is the largest subunit coded by mitochondria of complex I.The present study summarizes the structure and biological function of MT-ND1.From databases and literature,the expressions and mutations of MT-ND1 in a variety of cancers have been reviewed.MT-ND1 may be a biomarker for cancer diagnosis and prognosis.It is also a potential target for cancer therapy.

Putative metabolic roles of the mitochondria in asexual blood stages and gametocytes of Plasmodium falciparum

Upon infection into human red cell,Plasmodium falciparum differentiates into asexual and sexual(gametocyte) stages.The mitochondrion is a tubular-cristate organelle,functionally and structurally different between the two stages.Genes and proteins involving metabolic and functional roles,protein targeting and import to this organelle, are comprehensively reviewed.The genes and proteins of the electron transport system are identified, partially characterized in human and rodent malaria parasites consisting of a single subunit of NADH dehydrogenase, two subunits of succinate dehydrogenase,cytochrome C reductase and cytochrome Coxidase.One of the primary functional roles of the mitochondrion in the parasite is the coordination of pyrimidine biosynthesis, the electron transport system and oxygen utilization through dihydroorotate dehydrogenase.All enzymes of tricarboxylic acid cycle,pyruvate dehydrogenase complex and some enzymes of ATP synthase,are identified and partially characterized using the completed P.falciparum genome.Some metabolic and functional roles of the organelle include oxidative phosphorylation,ubiquinone and heme biosynthesis,antioxidant defense and redox balance.Recent physiological studies involve membrane potential maintenance,cellular signaling and cation homeostasis.The organelle is a target for antimalarial drug,i.e.atovaquone.Based on the lines of evidence, we hypothesize that the parasite exhibits metabolic adaptation of the underdeveloped mitochondrial organelle to life in the mosquito vector and the human host.

CPEB1,a novel risk gene in recent-onset schizophrenia,contributes to mitochondrial complex I defect caused by a defective provirus ERVWE1

BACKGROUND Schizophrenia afflicts 1%of the world population.Clinical studies suggest that schizophrenia patients may have an imbalance of mitochondrial energy metabolism via inhibition of mitochondrial complex I activity.Moreover,recent studies have shown that ERVWE1 is also a risk factor for schizophrenia.Nevertheless,there is no available literature concerning the relationship between complex I deficits and ERVWE1 in schizophrenia.Identifying risk factors and blood-based biomarkers for schizophrenia may provide new guidelines for early interventions and prevention programs.AIM To address novel potential risk factors and the underlying mechanisms of mitochondrial complex I deficiency caused by ERVWE1 in schizophrenia.METHODS Quantitative polymerase chain reaction(qPCR)and enzyme-linked immunosorbent assay were used to detect differentially expressed risk factors in blood samples.Clinical statistical analyses were performed by median analyses and Mann-Whitney U analyses.Spearman’s rank correlation was applied to examine the correlation between different risk factors in blood samples.qPCR,western blot analysis,and luciferase assay were performed to confirm the relationship among ERVWE1,cytoplasmic polyadenylation element-binding protein 1(CPEB1),NADH dehydrogenase ubiquinone flavoprotein 2(NDUFV2),and NDUFV2 pseudogene(NDUFV2P1).The complex I enzyme activity microplate assay was carried out to evaluate the complex I activity induced by ERVWE1.RESULTS Herein,we reported decreasing levels of CPEB1 and NDUFV2 in schizophrenia patients.Further studies showed that ERVWE1 was negatively correlated with CPEB1 and NDUFV2 in schizophrenia.Moreover,NDUFV2P1 was increased and demonstrated a significant positive correlation with ERVWE1 and a negative correlation with NDUFV2 in schizophrenia.In vitro experiments disclosed that ERVWE1 suppressed NDUFV2 expression and promoter activity by increasing NDUFV2P1 level.The luciferase assay revealed that ERVWE1 could enhance the promoter activity of NDUFV2P1.Additionally,ERVWE1 downregulated the expression of CPEB1 by suppressing the promoter activity,and the 400 base pair sequence at the 3′terminus of the promoter was the minimum sequence required.Advanced studies showed that CPEB1 participated in regulating the NDUFV2P1/NDUFV2 axis mediated by ERVWE1.Finally,we found that ERVWE1 inhibited complex I activity in SH-SY5Y cells via the CPEB1/NDUFV2P1/NDUFV2 signaling pathway.CONCLUSION In conclusion,CPEB1 and NDUFV2 might be novel potential blood-based biomarkers and pathogenic factors in schizophrenia.Our findings also reveal a novel mechanism of ERVWE1 in the etiology of schizophrenia.

HMG CoA reductase inhibition by Simvastatin gets rat <i>β</i>-Myosin heavy chain disappeared: A statin paradox

3-hydroxy-3methylglutaryl Coenzyme A reductase, the rate limiting enzyme of mevalonate pathway, generates, in addition to cholesterol, a range of products involved in several biological functions: oligoprenyl groups, dolichol and ubiquinone. The latter, in particular, participates in electron transport chain and, in turn, in tissue energy supply. The enzyme is inhibited by statins that, besides lowering cholesterolemia, seem to impair human energy-dependent myocardial functions (e.g. stroke volume, cardiac output, and contractile index). The modulation of heart contractile properties could be explained by the decrease of ventricle ubiquinone content and/or by putative changes in proportion of the different myosin heavy chain isoforms. Since we previously demonstrated that chronic statin treatment modifies myosin heavy chain isoform pattern in skeletal muscle impairing its functional properties, this work was aimed at investigating the effects of statin chronic treatment on both ventricle ubiquinone content and myosin heavy chain isoforms. Our results showed that simvastatin treatment leads to a reduced amount of rat ventricle ubiquinone and to β myosin heavy chain disappearance. Thus, statins which are prescribed to prevent cardiovascular disease, might induce cardiac metabolic and structural modifications whose functional implications on contractility are still to be established and carefully considered.

Liposoluble quinone promotes the reduction of hydrophobic mineral and extracellular electron transfer of Shewanella oneidensis MR-1

A large number of reaction systems are composed of hydrophobic interfaces and microorganisms in natural environment.However,it is not clear how microorganisms adjust their breathing patterns and respond to hydrophobic interfaces.Here,Shewanella oneidensis MR-1 was used to reduce ferrihydrite of a hydrophobic surface.Through Fe(II)kinetic analysis,it was found that the reduction rate of hydrophobic ferrihydrite was 1.8 times that of hydrophilic one.The hydrophobic surface of the mineral hinders the way the electroactive microorganism uses the water-soluble electron mediator riboflavin for indirect electron transfer and promotes MR-1 to produce more liposoluble quinones.Ubiquinone can mediate electron transfer at the hydrophobic interface.Ubiquinone-30(UQ-6)increases the reduction rate of hydrophobic ferrihydrite from 38.5±4.4 to 52.2±0.8 mM$h
1.Based on the above experimental results,we propose that liposoluble electron mediator ubiquinone can act on the extracellular hydrophobic surface,proving that the metabolism of hydrophobic minerals is related to endogenous liposoluble quinones.Hydrophobic modification of minerals encourages electroactive microorganisms to adopt differentiated respiratory pathways.This finding helps in understanding the electron transfer behavior of the microbes at the hydrophobic interface and provides new ideas for the study of hydrophobic reactions that may occur in systems,such as soil and sediment.