J J Lemasters

Medical University of South Carolina, Charleston, South Carolina, United States

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Publications (408)2055.31 Total impact

  • Journal of the American Society of Nephrology 11/2014; 25:389A. · 9.47 Impact Factor
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    ABSTRACT: Cells exposed to extreme physicochemical or mechanical stimuli die in an uncontrollable manner, as a result of their immediate structural breakdown. Such an unavoidable variant of cellular demise is generally referred to as /`accidental cell death/' (ACD). In most settings, however, cell death is initiated by a genetically encoded apparatus, correlating with the fact that its course can be altered by pharmacologic or genetic interventions. /`Regulated cell death/' (RCD) can occur as part of physiologic programs or can be activated once adaptive responses to perturbations of the extracellular or intracellular microenvironment fail. The biochemical phenomena that accompany RCD may be harnessed to classify it into a few subtypes, which often (but not always) exhibit stereotyped morphologic features. Nonetheless, efficiently inhibiting the processes that are commonly thought to cause RCD, such as the activation of executioner caspases in the course of apoptosis, does not exert true cytoprotective effects i
    Cell death and differentiation 09/2014; · 8.24 Impact Factor
  • Eduardo N Maldonado, John J Lemasters
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    ABSTRACT: Non-proliferating cells generate the bulk of cellular ATP by fully oxidizing respiratory substrates in mitochondria. Respiratory substrates cross the mitochondrial outer membrane through only one channel, the voltage dependent anion channel (VDAC). Once in the matrix, respiratory substrates are oxidized in the tricarboxylic acid cycle to generate mostly NADH that is further oxidized in the respiratory chain to generate a proton motive force comprised mainly of membrane potential (ΔΨ) to synthesize ATP. Mitochondrial ΔΨ then drives release of ATP(-4) from the matrix in exchange for ADP(-3) in the cytosol via the adenine nucleotide translocator (ANT) located in the mitochondrial inner membrane. Thus, mitochondrial function in non-proliferating cells drives a high cytosolic ATP/ADP ratio, essential to inhibit glycolysis. By contrast, the bioenergetics of the Warburg phenotype of proliferating cells is characterized by enhanced aerobic glycolysis and suppression of mitochondrial metabolism. Suppressed mitochondrial function leads to lower production of mitochondrial ATP and hence lower cytosolic ATP/ADP ratios that favor enhanced glycolysis. Thus, cytosolic ATP/ADP ratio is a key feature that determines if cell metabolism is predominantly oxidative or glycolytic. Here, we describe two novel mechanisms to explain the suppression of mitochondrial metabolism in cancer cells: the relative closure of VDAC by free tubulin and inactivation of ANT. Both mechanisms contribute to low ATP/ADP ratios that activate glycolysis.
    Mitochondrion 09/2014; · 3.52 Impact Factor
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    ABSTRACT: First-line therapy for pancreatic cancer is gemcitabine. Although tumors may initially respond to the gemcitabine treatment, soon tumor resistance develops leading to treatment failure. Previously, we demonstrated in human MIA PaCa-2 pancreatic cancer cells that N-acetyl-l-cysteine (NAC), a glutathione (GSH) precursor, prevents NFκB activation via S-glutathionylation of p65-NFκB, thereby blunting expression of survival genes. In this study, we documented the molecular sites of S-glutathionylation of p65, and we investigated whether NAC can suppress NFκB signaling and augment a therapeutic response to gemcitabine in vivo. Mass spectrometric analysis of S-glutathionylated p65-NFκB protein in vitro showed post-translational modifications of cysteines 38, 105, 120, 160 and 216 following oxidative and nitrosative stress. Circular dichroism revealed that S-glutathionylation of p65-NFκB did not change secondary structure of the protein, but increased tryptophan fluorescence revealed altered tertiary structure. Gemcitabine and NAC individually were not effective in decreasing MIA PaCa-2 tumor growth in vivo. However, combination treatment with NAC and gemcitabine decreased tumor growth by approximately 50%. NAC treatment also markedly enhanced tumor apoptosis in gemcitabine-treated mice. Compared to untreated tumors, gemcitabine treatment alone increased p65-NFκB nuclear translocation (3.7-fold) and DNA binding (2.5-fold), and these effects were blunted by NAC. In addition, NAC plus gemcitabine treatment decreased anti-apoptotic XIAP protein expression compared to gemcitabine alone. None of the treatments, however, affected extent of tumor hypoxia, as assessed by EF5 staining. Together, these results indicate that adjunct therapy with NAC prevents NFκB activation and improves gemcitabine chemotherapeutic efficacy.
    Biomedecine [?] Pharmacotherapy 08/2014; · 2.11 Impact Factor
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    ABSTRACT: Ca(2+)-induced permeability transition pore (mPTP) opening in isolated rat brain mitochondria is promoted through targeting of connexin43. After a threshold Ca(2+) load, mitochondrial membrane potential drops and efflux of accumulated Ca(2+) from the mitochondrial matrix occurs, indicating the mPTP opening. Specific antibodies were used to assess the role of the translocator protein (18 kDa; TSPO) and connexin43 in swelling of isolated rat liver and brain mitochondria induced by carbenoxolone and the endogenous TSPO ligand protoporphyrin IX. Mitochondrial membrane potential, Ca(2+) transport and oxygen consumption were determined using selective electrodes. All the parameters were detected simultaneously in a chamber with the selective electrodes. The phosphorylation state of mitochondrial protein targets was assessed. We report that Ca(2+)-induced mitochondrial swelling was strengthened in the presence of both carbenoxolone and protoporphyrin IX. The carbenoxolone- and protoporphyrin IX-accelerated mPTP induction in brain mitochondria was completely prevented by antibodies specific for the mitochondrial translocator protein (TSPO). The anti-TSPO antibodies were more effective than anti-сonnexin43 antibodies. Moreover, carbenoxolone-stimulated phosphorylation of mitochondrial proteins was inhibited by anti-TSPO antibodies. Taken together, the data suggests that, in addition to acting via connexion43, carbenoxolone may exert its effect on mPTP via mitochondrial outer membrane TSPO.
    Archives of Biochemistry and Biophysics 07/2014; · 3.04 Impact Factor
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    ABSTRACT: Despite recovery of hemodynamics by fluid resuscitation after hemorrhage, development of the systemic inflammatory response and multiple organ dysfunction syndromes can nonetheless lead to death. Minocycline and doxycycline are tetracycline derivatives that are protective in models of hypoxic, ischemic and oxidative stress. Our Aim was to determine whether minocycline and doxycycline protect liver and kidney and improve survival in a mouse model of hemorrhagic shock and resuscitation.
    Shock (Augusta, Ga.) 06/2014; · 2.87 Impact Factor
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    ABSTRACT: Polycystic kidney disease (PKD) is a common genetic disorder leading to cyst formation in the kidneys and other organs that ultimately results in kidney failure and death. Currently, there is no therapy for slowing down or stopping the progression of PKD. In this study we identified the disintegrin metalloenzyme 17 (ADAM17) as a key regulator of cell proliferation in kidney tissues of conditional knockout Ift88-/- mice and collecting duct epithelia cell from Ift88orpk mice, animal models of autosomal recessive polycystic kidney disease (ARPKD). Using Western blotting, an enzyme activity assay and a growth factor shedding assay in the presence or absence of the specific ADAM17 inhibitor TMI-005, we show that increased expression and activation of ADAM17 in cystic kidney and in collecting duct epithelial cells originating from the Ift88orpk mice (designated as PKD cells) leads to constitutive shedding of several growth factors including heparin-binding EGF-like growth factor (HB-EGF), amphiregulin and transforming growth factor-alpha (TGFα). Increased growth factor shedding induces activation of the EGFR/MAPK/ERK pathway and maintains higher cell proliferation rate in PKD cells compared to control cells. PKD cells also displayed increased lactate formation and extracellular acidification indicative of aerobic glycolysis (Warburg effect) that was blocked by ADAM17 inhibition. We propose that ADAM17 is a key promoter of cellular proliferation in PKD cells by activating the EGFR/ERK axis and a pro-proliferative glycolytic phenotype.
    American journal of physiology. Renal physiology 06/2014; · 3.30 Impact Factor
  • Gastroenterology 05/2014; 146(5):944. · 13.93 Impact Factor
  • Gastroenterology 05/2014; 146(5):S928. · 13.93 Impact Factor
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    ABSTRACT: An increase of ethanol metabolism and hepatic mitochondrial respiration occurs in vivo after a single binge of alcohol. Here, our aim was to determine how ethanol intake affects hepatic mitochondrial polarization status in vivo in relation to ethanol metabolism and steatosis. Hepatic mitochondrial polarization, permeability transition (MPT), and reduce pyridine nucleotides, and steatosis in mice were monitored by intravital confocal/multiphoton microscopy of the fluorescence of rhodamine 123 (Rh123), calcein, NAD(P)H, and BODIPY493/503, respectively, after gavage with ethanol (1-6 g/kg). Mitochondria depolarized in an all-or-nothing fashion in individual hepatocytes as early as 1 h after alcohol. Depolarization was dose- and time-dependent, peaked after 6 to 12 h and maximally affected 94% of hepatocytes. This mitochondrial depolarization was not due to onset of the MPT. After 24 h, mitochondria of most hepatocytes recovered normal polarization and were indistinguishable from untreated after 7 days. Cell death monitored by propidium iodide staining, histology and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was low throughout. After alcohol, mitochondrial NAD(P)H autofluorescence increased and decreased, respectively, in hepatocytes with polarized and depolarized mitochondria. Ethanol also caused steatosis mainly in hepatocytes with depolarized mitochondria. Depolarization was linked to ethanol metabolism, since deficiency of alcohol dehydrogenase and cytochrome-P450 2E1 (CYP2E1), the major ethanol-metabolizing enzymes, decreased mitochondrial depolarization by ∼70% and ∼20%, respectively. Activation of aldehyde dehydrogenase decreased depolarization, whereas inhibition of aldehyde dehydrogenase enhanced depolarization. Activation of aldehyde dehydrogenase also markedly decreased steatosis. Acute ethanol causes reversible hepatic mitochondrial depolarization in vivo that may contribute to steatosis and increased mitochondrial respiration. Onset of this mitochondrial depolarization is linked, at least in part, to metabolism of ethanol to acetaldehyde.
    PLoS ONE 03/2014; 9(3):e91308. · 3.53 Impact Factor
  • AJP Heart and Circulatory Physiology 03/2014; 306(5):H778-9. · 4.01 Impact Factor
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    John J. Lemasters
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    ABSTRACT: Mitophagy (mitochondrial autophagy), which removes damaged, effete and superfluous mitochondria, has several distinct variants. In Type 1 mitophagy occurring during nutrient deprivation, preautophagic structures (PAS) grow into cup-shaped phagophores that surround and sequester individual mitochondria into mitophagosomes, a process requiring phosphatidylinositol-3-kinase (PI3K) and often occurring in coordination with mitochondrial fission. After sequestration, the outer compartment of the mitophagosome acidifies, followed by mitochondrial depolarization and ultimately hydrolytic digestion in lysosomes. Mitochondrial damage stimulates Type 2 mitophagy. After photodamage to single mitochondria, depolarization occurs followed by decoration and then coalescence of autophagic LC3-containing structures on mitochondrial surfaces. Vesicular acidification then occurs. By contrast to Type 1 mitophagy, PI3K inhibition does not block Type 2 mitophagy. Further, Type 2 mitophagy is not associated with phagophore formation or mitochondrial fission. A third form of self-eating of mitochondria is formation of mitochondria-derived vesicles (MDVs) enriched in oxidized mitochondrial proteins that bud off and transit into multivesicular bodies. Topologically, the internalization of MDV by invagination of the surface of multivesicular bodies followed by vesicle scission into the lumen is a form of microautophagy, or micromitophagy (Type 3 mitophagy). Cell biological distinctions are the basis for these three types of mitophagy. Future studies are needed to better characterize the molecular and biochemical differences between Types 1, 2 and 3 mitophagy.
    Redox Biology. 01/2014;
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    ABSTRACT: Research in autophagy continues to accelerate,(1) and as a result many new scientists are entering the field. Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms. Recent reviews have described the range of assays that have been used for this purpose.(2,3) There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi). Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes. This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response.
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    ABSTRACT: Recent studies suggest that an increase in apoptosis within the myocardium may be a contributing factor for the progression of adverse left ventricular (LV) remodeling following myocardial infarction (MI). Given that apoptosis is often triggered by induction of the mitochondrial permeability transition (MPT) pore, the goal of this study was to evaluate the therapeutic efficacy of cyclosporin A (CsA), an MPT blocker, to prevent cells from undergoing apoptosis and consequently attenuate LV remodeling post-MI. MI was induced in C57BL/6 mice and then randomized to either vehicle or CsA groups. Beginning 48 h after surgery, mice were gavaged with CsA (2 mg/kg) or vehicle once daily. LV end diastolic volume and LV ejection fraction were assessed by echocardiography before MI induction and terminally at either 7 days (n=7) or 28 days (n=8) post-MI. LV end diastolic volume was increased and LV ejection fraction was decreased in all MI groups with no difference between the CsA-treated and untreated groups. After vehicle and CsA, areas of necrosis were present at 7 and 28 days post MI with no difference between MI groups. Caspase-3 activity and TUNEL-positive cells in myocardium from the non-necrotic areas were both increased after MI but were lower in CsA-treated mice compared to vehicle (p<0.05). In conclusion, CsA decreased apoptosis occurring after MI, confirming involvement of the MPT. However, CsA-mediated reduction in apoptosis in non-MI myocardium was not beneficial in reducing LV volume or improving LV pump function.
    AJP Heart and Circulatory Physiology 10/2013; · 4.01 Impact Factor
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    ABSTRACT: Minocycline, a tetracycline-derived compound, mitigates damage caused by ischemia/reperfusion (I/R) injury. Here, 19 tetracycline-derived compounds were screened in comparison to minocycline for their ability to protect hepatocytes against damage from chemical hypoxia and I/R injury. Cultured rat hepatocytes were incubated with 50μM of each tetracycline-derived compound 20min prior to exposure to 500μM iodoacetic acid plus 1mM KCN (chemical hypoxia). In other experiments, hepatocytes were incubated in anoxic Krebs-Ringer-Hepes buffer (KRH) at pH6.2 for 4h prior to reoxygenation at pH7.4 (simulated I/R). Tetracycline-derived compounds were added 20min prior to reperfusion. Ca(2+) uptake was measured in isolated rat liver mitochondria incubated with Fluo-5N. Cell killing after 120min of chemical hypoxia measured by propidium iodide (PI) fluorometery was 87%, which decreased to 28% and 42% with minocycline and doxycycline, respectively. After I/R, cell killing at 120min decreased from 79% with vehicle to 43% and 49% with minocycline and doxycycline. No other tested compound decreased killing. Minocycline and doxycycline also inhibited mitochondrial Ca(2+) uptake and suppressed the Ca(2+)-induced mitochondrial permeability transition (MPT), the penultimate cause of cell death in reperfusion injury. Ru360, a specific inhibitor of the mitochondrial calcium uniporter (MCU), also decreased cell killing after hypoxia and I/R and blocked mitochondrial Ca(2+) uptake and the MPT. Other proposed mechanisms, including mitochondrial depolarization and matrix metalloprotease inhibition could not account for cytoprotection. Taken together, these results indicate that minocycline and doxycycline are cytoprotective by way of inhibition of MCU.
    Toxicology and Applied Pharmacology 09/2013; · 3.98 Impact Factor
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    ABSTRACT: Sub-100 nm colloidal particles which are surface-functionalized with multiple environmentally-sensitive moieties have the potential to combine imaging, early detection, and the treatment of cancer with a single type of long-circulating “nanodevice”. Deep tissue imaging is achievable through the development of particles which are surface-modified with fluorophores that operate in the near-infrared (NIR) spectrum and where the fluorophore's signal can be maximized by “turning-on” the fluorescence only in the targeted tissue. We present a general approach for the synthesis of NIR emitting nanoparticles that exhibit a protein triggered activation/deactivation of the emission. Dispersing the particles into an aqueous solution, such as phosphate buffered saline (PBS), resulted in an aggregation of the hydrophobic fluorophores and a cessation of emission. The emission can be reinstated, or activated, by the conversion of the surface-attached fluorophores from an aggregate to a monomeric species with the addition of an albumin. This activated probe can be deactivated and returned to a quenched state by a simple tryptic digestion of the albumin. The methodology for emission switching offers a path to maximize the signal from the typically weak quantum yield inherent in NIR fluorophores.
    J. Mater. Chem. B. 08/2013; 1(36).
  • Shock (Augusta, Ga.) 06/2013; 39(6):543. · 2.87 Impact Factor
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    Gastroenterology 05/2013; 144(5):S-1030. · 13.93 Impact Factor
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    ABSTRACT: Autophagy has emerged as a critical lysosomal pathway that maintains cell function and survival through the degradation of cellular components such as organelles and proteins. Investigations specifically employing the liver or hepatocytes as experimental models have contributed significantly to our current knowledge of autophagic regulation and function. The diverse cellular functions of autophagy, along with unique features of the liver and its principal cell type the hepatocyte, suggest that the liver is highly dependent on autophagy for both normal function and to prevent the development of disease states. However, instances have also been identified in which autophagy promotes pathological changes such as the development of hepatic fibrosis. Considerable evidence has accumulated that alterations in autophagy are an underlying mechanism of a number of common hepatic diseases including toxin-, drug- and ischemia/reperfusion-induced liver injury, fatty liver, viral hepatitis and hepatocellular carcinoma. This review summarizes recent advances in understanding the roles that autophagy plays in normal hepatic physiology and pathophysiology with the intent of furthering the development of autophagy-based therapies for human liver diseases.
    Autophagy 05/2013; 9(8). · 11.42 Impact Factor
  • Xun Zhang, John J Lemasters
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    ABSTRACT: The mitochondrial permeability transition (MPT) initiated by reactive oxygen species (ROS) plays an essential role in ischemia-reperfusion (IR) injury. Iron is a critical catalyst for ROS formation, and intracellular chelatable iron promotes oxidative injury-induced and MPT-dependent cell death in hepatocytes. Accordingly, our aim was to investigate the role of chelatable iron in IR-induced ROS generation, MPT formation and cell death in primary rat hepatocytes. To simulate IR, overnight cultured hepatocytes were incubated anoxically at pH 6.2 for 4h and re-oxygenated at pH 7.4. Chelatable Fe(2+), ROS and mitochondrial membrane potential were monitored by confocal fluorescence microscopy of calcein, chloromethyl dichlorofluorescein (cmDCF) and tetramethylrhodamine methylester (TMRM), respectively. Cell killing was assessed by propidium iodide fluorometry. Ischemia caused progressive quenching of cytosolic calcein by more than 90%, signifying increased chelatable Fe(2+). Desferal and starch-desferal 1h prior to ischemia suppressed calcein quenching. Ischemia also induced quenching and dequenching of calcein loaded into mitochondria and lysosomes, respectively. Desferal, starch-desferal, and the inhibitor of the mitochondrial Ca(2+) uniporter (MCU), Ru360, suppressed mitochondrial calcein quenching during ischemia. Desferal, starch-desferal and Ru360 before ischemia also decreased mitochondrial ROS formation, MPT opening and cell killing after reperfusion. These results indicate that lysosomes release chelatable Fe(2+) during ischemia, which is taken up into mitochondria by MCU. Increased mitochondrial iron then predisposes to ROS-dependent MPT opening and cell killing after reperfusion.
    Free Radical Biology and Medicine 05/2013; · 5.27 Impact Factor

Publication Stats

18k Citations
2,055.31 Total Impact Points

Institutions

  • 2006–2014
    • Medical University of South Carolina
      • • Hollings Cancer Center
      • • Center of Cell Death, Injury and Regeneration
      • • Department of Pharmaceutical Sciences
      Charleston, South Carolina, United States
    • Mayo Foundation for Medical Education and Research
      • Department of Medicine
      Scottsdale, AZ, United States
  • 2012
    • University of Michigan
      • Life Sciences Institute
      Ann Arbor, MI, United States
  • 2008–2012
    • Kansas City VA Medical Center
      Kansas City, Missouri, United States
    • University of South Carolina
      • Pharmaceutical and Biomedical Sciences
      Columbia, South Carolina, United States
  • 1997–2012
    • University of Florida
      • • Department of Surgery
      • • Department of Pharmacology and Therapeutics
      Gainesville, FL, United States
  • 1980–2012
    • University of North Carolina at Chapel Hill
      • • Department of Cell and Developmental Biology
      • • Department of Surgery
      • • Department of Medicine
      • • Department of Pharmacology
      Chapel Hill, NC, United States
  • 2007
    • University of Charleston
      Charleston, West Virginia, United States
    • Juntendo University
      • Division of Gastroenterology
      Tokyo, Tokyo-to, Japan
  • 2003–2006
    • The University of Arizona
      • College of Medicine
      Tucson, AZ, United States
    • Columbia University
      • Department of Medicine
      New York City, NY, United States
  • 2002–2003
    • Novartis
      Bâle, Basel-City, Switzerland
    • University of Arkansas at Little Rock
      Little Rock, Arkansas, United States
  • 2001
    • VU University Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 2000
    • National Institute on Alcohol Abuse and Alcoholism
      Maryland, United States
  • 1997–1999
    • Case Western Reserve University
      • Department of Anatomy
      Cleveland, OH, United States
  • 1996
    • University of Pavia
      Ticinum, Lombardy, Italy
  • 1990
    • Universität des Saarlandes
      Saarbrücken, Saarland, Germany
  • 1983
    • University of North Carolina at Pembroke
      North Carolina, United States