Jeffery D Molkentin

Howard Hughes Medical Institute, Ashburn, Virginia, United States

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Publications (364)3260.69 Total impact

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    ABSTRACT: Acute pancreatitis is caused by toxins that induce acinar cell calcium overload, zymogen activation, cytokine release and cell death, yet is without specific drug therapy. Mitochondrial dysfunction has been implicated but the mechanism not established. We investigated the mechanism of induction and consequences of the mitochondrial permeability transition pore (MPTP) in the pancreas using cell biological methods including confocal microscopy, patch clamp technology and multiple clinically representative disease models. Effects of genetic and pharmacological inhibition of the MPTP were examined in isolated murine and human pancreatic acinar cells, and in hyperstimulation, bile acid, alcoholic and choline-deficient, ethionine-supplemented acute pancreatitis. MPTP opening was mediated by toxin-induced inositol trisphosphate and ryanodine receptor calcium channel release, and resulted in diminished ATP production, leading to impaired calcium clearance, defective autophagy, zymogen activation, cytokine production, phosphoglycerate mutase 5 activation and necrosis, which was prevented by intracellular ATP supplementation. When MPTP opening was inhibited genetically or pharmacologically, all biochemical, immunological and histopathological responses of acute pancreatitis in all four models were reduced or abolished. This work demonstrates the mechanism and consequences of MPTP opening to be fundamental to multiple forms of acute pancreatitis and validates the MPTP as a drug target for this disease. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    Gut 06/2015; DOI:10.1136/gutjnl-2014-308553 · 13.32 Impact Factor
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    ABSTRACT: During apoptosis the pro-death Bcl-2 family members Bax and Bak induce mitochondrial outer membrane permeabilization (MOMP) to mediate cell death. Recently, it was shown that Bax and Bak are also required for mitochondrial permeability transition pore (MPTP)-dependent necrosis, where, in their non-oligomeric state, they enhance permeability characteristics of the outer mitochondrial membrane. Necroptosis is another form of regulated necrosis involving the death receptors and receptor interacting protein kinases (RIP proteins, by Ripk genes). Here, we show cells or mice deficient for Bax/Bak or cyclophilin D, a protein that regulates MPTP opening, are resistant to cell death induced by necroptotic mediators. We show that Bax/Bak oligomerization is required for necroptotic cell death and that this oligomerization reinforces MPTP opening. Mechanistically, we observe mixed lineage kinase domain-like (MLKL) protein and cofilin-1 translocation to the mitochondria following necroptosis induction, while expression of the mitochondrial matrix isoform of the antiapoptotic Bcl-2 family member, myeloid cell leukemia 1 (Mcl-1), is significantly reduced. Some of these effects are lost with necroptosis inhibition in Bax/Bak1 double null, Ppif-/-, or Ripk3-/- fibroblasts. Hence, downstream mechanisms of cell death induced by necroptotic stimuli utilize both Bax/Bak to generate apoptotic pores in the outer mitochondrial membrane as well as MPTP opening in association with known mitochondrial death modifying proteins.
    PLoS ONE 06/2015; 10(6):e0130520. DOI:10.1371/journal.pone.0130520 · 3.53 Impact Factor
  • Jason Karch, Jeffery D Molkentin
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    ABSTRACT: Although the molecular effectors of apoptotic cell death have been largely annotated over the past 30 years, leading to a strong biological understanding of this process and its importance in cell biology, cell death through necrosis has only recently been accepted as a similarly regulated process with definable molecular effectors. The mitochondria are important and central mediators of both apoptosis and regulated necrosis. In apoptosis, the B-cell leukemia/lymphoma 2 (Bcl-2) family members Bcl-2-associated protein x (Bax) and Bcl-2 homologues antagonist/killer (Bak) undergo oligomerization in the outer mitochondrial membrane resulting in the release of apoptosis inducing substrates and the activation of caspases and nucleases. In contrast, during necrosis the mitochondria become dysfunctional and maladaptive in conjunction with reactive oxygen species production and the loss of ATP production, in part through opening of the mitochondrial permeability transition pore. Although regulated necrosis is caspase-independent, recent evidence has shown that it still requires the apoptotic regulators Bax/Bak, which can regulate the permeability characteristics of the outer mitochondrial membrane in their nonoligomerized state. Here, we review the nonapoptotic side of Bcl-2 family, specifically the role of Bax/Bak in regulated necrotic cell death. We will also discuss how these Bcl-2 family member effectors could be part of a larger integrated network that ultimately decides the fate of a given cell somewhere within a molecular continuum between apoptosis and regulated necrosis. © 2015 American Heart Association, Inc.
    Circulation Research 05/2015; 116(11):1800-1809. DOI:10.1161/CIRCRESAHA.116.305421 · 11.09 Impact Factor
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    ABSTRACT: Radiocontrast agents are required for radiographic procedures, but these agents can injure tissues by unknown mechanisms. We investigated whether exposure of pancreatic tissues to radiocontrast agents during endoscopic retrograde cholangiopancreatography (ERCP) causes pancreatic inflammation, and studied the effects of these agents on human cell lines and in mice. We exposed mouse and human acinar cells to the radiocontrast agent iohexol (Omnipaque) and measured intracellular release of Ca(2+), calcineurin activation (using a luciferase reporter), activation of nuclear factor-κB (NF-κB, using a luciferase reporter), and cell necrosis (via propidium iodide uptake). We infused the radiocontrast agent into the pancreatic ducts of wild type mice (C57BL/6) to create a mouse model of post-ERCP pancreatitis; some mice were given intraperitoneal injections of the calcineurin inhibitor FK506 before and after infusion of the radiocontrast agent. CnAβ(-/-) mice were also used. This experiment was also performed in mice given infusions of AAV6-NF-κB-luciferase, to assess activation of this transcription factor in vivo. Incubation of mouse and human acinar cells, but not HEK293 or COS7 cells, with iohexol led to a peak and then plateau in Ca(2+) signaling, along with activation of the transcription factors NF-κB and NFAT. Suppressing Ca(2+) signaling or calcineurin with BAPTA, cyclosporine A, or FK506 prevented activation of NF-κB and acinar cell injury. Calcineurin Aβ-deficient mice were protected against induction of pancreatic inflammation by iohexol. The calcineurin inhibitor FK506 prevented contrast-induced activation of NF-κB in pancreata of mice; this was observed by live imaging of mice given infusions of AAV6- NF-kB-luciferase. Radiocontrast agents cause pancreatic inflammation in mice, via activation of NF-κB, Ca(2+) signaling, and calcineurin. Calcineurin inhibitors might be developed to prevent post-ERCP pancreatitis in patients. Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.
    Gastroenterology 05/2015; DOI:10.1053/j.gastro.2015.05.004 · 13.93 Impact Factor
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    ABSTRACT: The matricellular secreted protein, connective tissue growth factor (CTGF), is upregulated in response to cardiac injury or with transforming growth factor β (TGFβ) stimulation, where it has been suggested to function as a fibrotic effector. Here we generated transgenic mice with inducible cardiac-specific CTGF overexpression, mice with cardiac-specific expression of an activated TGFβ mutant protein, mice with cardiac-specific deletion of Ctgf, and mice in which Ctgf was also deleted from fibroblasts in the heart. Remarkably, neither gain nor loss of CTGF in the heart affected cardiac pathology and propensity toward early lethality due to TGFβ over activation in the heart. Also, neither heart-specific Ctgf deletion nor CTGF overexpression altered cardiac remodeling and function with aging or after multiple acute stress stimuli. Cardiac fibrosis was also unchanged by modulation of CTGF levels in the heart with aging, pressure overload, agonist infusion or TGFβ overexpression. However, CTGF did mildly alter the overall cardiac response to TGFβ when pressure overload stimulation was applied. CTGF has been proposed to function as a critical TGFβ effector in underlying tissue remodeling and fibrosis throughout the body, although our results suggest that CTGF is of minimal importance and is an unlikely therapeutic vantage point for the heart. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Molecular and Cellular Biology 04/2015; DOI:10.1128/MCB.00199-15 · 5.04 Impact Factor
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    ABSTRACT: Sarcolipin (SLN) is a regulator of sarco(endo)plasmic reticulum calcium ATPase (SERCA) in skeletal muscle. Recent studies using SLN null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression (Sln(OE)) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/ fatigue and metabolic rate in whole animals and isolated muscle. We found that Sln(OE) mice are more resistant to fatigue and can run significantly longer distance than wild type (WT). Studies with isolated extensor digitorum longus (EDL) muscle show that Sln(OE) EDL produces higher twitch force than WT. The force-frequency curves were not different between WT and Sln(OE) EDLs, but at lower frequencies the pyruvate induced potentiation of force was significantly higher in Sln(OE) EDL. SLN overexpression did not alter the twitch and force frequency curve in isolated soleus muscle. However, during a 10 minute fatigue protocol both EDL and soleus from Sln(OE) mice fatigued significantly less than WT muscles. Interestingly, Sln(OE) muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in Sln(OE) EDL suggesting increased glycolytic capacity. We also found an increase in store operated calcium entry (SOCE), in isolated flexor digitorum brevis fibers of Sln(OE) than WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity, by increasing SOCE and muscle energetics. Copyright © 2014, Journal of Applied Physiology.
    Journal of Applied Physiology 02/2015; 118(8):jap.01066.2014. DOI:10.1152/japplphysiol.01066.2014 · 3.43 Impact Factor
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    ABSTRACT: Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting secondary to repeated muscle damage and inadequate repair. Elevations in intracellular free Ca2+ have been implicated in disease progression and SERCA1 overexpression has been shown to ameliorate the dystrophic phenotype in mdx mice. The purpose of this study was to assess the effects of SERCA1 overexpression in the more severe mdx/Utr-/- mouse model of DMD. Mice overexpressing SERCA1 were crossed with mdx/Utr+/- mice to generate mdx/Utr-/-/+SERCA1 mice and compared to wild-type (WT), WT/+SERCA1, mdx/+SERCA1 and genotype controls. Mice were assessed at ~12 weeks of age for changes in Ca2+-handling, muscle mass, quadriceps torque, markers of muscle damage and response to repeated eccentric contractions. SERCA1 overexpressing mice had a 2- to 3-fold increase in maximal SR Ca2+ ATPase activity compared to WT which was associated with normalization in body mass for both mdx/+SERCA1 and mdx/Utr-/-/+SERCA1. Torque deficit in the quadriceps after eccentric injury was 2.7-fold greater in mdx/Utr-/- vs. WT mice, but only 1.5-fold greater in mdx/Utr-/-/+SERCA1 vs. WT mice, an attenuation of 44%. Markers of muscle damage (% central nucleated fibres, necrotic area, and serum creatine kinase levels) were higher in both mdx and mdx/Utr-/- vs. WT and all were attenuated by overexpression of SERCA1. These data indicate that SERCA1 overexpression ameliorates functional impairments and cellular markers of damage in a more severe mouse model of DMD. These findings support targeting intracellular Ca2+ control as a therapeutic approach for DMD.
    AJP Cell Physiology 02/2015; 308(9). DOI:10.1152/ajpcell.00341.2014 · 3.67 Impact Factor
  • Jennifer Q Kwong, Jeffery D Molkentin
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    ABSTRACT: Prolonged mitochondrial permeability transition pore (MPTP) opening results in mitochondrial energetic dysfunction, organelle swelling, rupture, and typically a type of necrotic cell death. However, acute opening of the MPTP has a critical physiologic role in regulating mitochondrial Ca(2+) handling and metabolism. Despite the physiological and pathological roles that the MPTP orchestrates, the proteins that comprise the pore itself remain an area of ongoing investigation. Here, we will discuss the molecular composition of the MPTP and its role in regulating cardiac physiology and disease. A better understanding of MPTP structure and function will likely suggest novel cardioprotective therapeutic approaches. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell Metabolism 02/2015; 21(2):206-214. DOI:10.1016/j.cmet.2014.12.001 · 16.75 Impact Factor
  • Jop H van Berlo, Jeffery D Molkentin
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    ABSTRACT: Cardiac regeneration is a rapidly evolving and controversial field of research. The identification some 12 years ago of progenitor cells that reside within the heart spurred enthusiasm for cell-based regenerative therapies. However, recent evidence has called into question both the presence of a biologically important stem cell population in the heart and the ability of exogenously derived cells to promote regeneration through direct formation of new cardiomyocytes. Here, we discuss recent developments that suggest an emerging consensus on the ability of different cell types to regenerate the adult mammalian heart.
    Nature Medicine 12/2014; 20(12):1386-93. DOI:10.1038/nm.3764 · 28.05 Impact Factor
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    ABSTRACT: Latent transforming growth factor-β (TGFβ) binding proteins (LTBPs) bind to inactive TGFβ in the extracellular matrix. In mice, muscular dystrophy symptoms are intensified by a genetic polymorphism that changes the hinge region of LTBP, leading to increased proteolytic susceptibility and TGFβ release. We have found that the hinge region of human LTBP4 was also readily proteolysed and that proteolysis could be blocked by an antibody to the hinge region. Transgenic mice were generated to carry a bacterial artificial chromosome encoding the human LTBP4 gene. These transgenic mice displayed larger myofibers, increased damage after muscle injury, and enhanced TGFβ signaling. In the mdx mouse model of Duchenne muscular dystrophy, the human LTBP4 transgene exacerbated muscular dystrophy symptoms and resulted in weaker muscles with an increased inflammatory infiltrate and greater LTBP4 cleavage in vivo. Blocking LTBP4 cleavage may be a therapeutic strategy to reduce TGFβ release and activity and decrease inflammation and muscle damage in muscular dystrophy.
    Science translational medicine 10/2014; 6(259):259ra144. DOI:10.1126/scitranslmed.3010018 · 14.41 Impact Factor
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    ABSTRACT: The Ras-related guanosine triphosphatase RhoA mediates pathological cardiac hypertrophy, but also promotes cell survival and is cardioprotective after ischemia/reperfusion injury. To understand how RhoA mediates these opposing roles in the myocardium, we generated mice with a cardiomyocyte-specific deletion of RhoA. Under normal conditions, the hearts from these mice showed functional, structural, and growth parameters similar to control mice. Additionally, the hearts of the cardiomyocyte-specific, RhoA-deficient mice subjected to transverse aortic constriction (TAC)-a procedure that induces pressure overload and, if prolonged, heart failure-exhibited a similar amount of hypertrophy as those of the wild-type mice subjected to TAC. Thus, neither normal cardiac homeostasis nor the initiation of compensatory hypertrophy required RhoA in cardiomyocytes. However, in response to chronic TAC, hearts from mice with cardiomyocyte-specific deletion of RhoA showed greater dilation, with thinner ventricular walls and larger chamber dimensions, and more impaired contractile function than those from control mice subjected to chronic TAC. These effects were associated with aberrant calcium signaling, as well as decreased activity of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and AKT. In addition, hearts from mice with cardiomyocyte-specific RhoA deficiency also showed less fibrosis in response to chronic TAC, with decreased transcriptional activation of genes involved in fibrosis, including myocardin response transcription factor (MRTF) and serum response factor (SRF), suggesting that the fibrotic response to stress in the heart depends on cardiomyocyte-specific RhoA signaling. Our data indicated that RhoA regulates multiple pathways in cardiomyocytes, mediating both cardioprotective (hypertrophy without dilation) and cardio-deleterious effects (fibrosis).
    Science Signaling 10/2014; 7(348):ra100. DOI:10.1126/scisignal.2005262 · 7.65 Impact Factor
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    ABSTRACT: -Programmed necrosis (necroptosis) plays an important role in development, tissue homeostasis, and disease pathogenesis. The molecular mechanisms that regulate necroptosis in the heart and its physiological relevance in myocardial remodeling and heart failure remain largely unknown.
    Circulation 10/2014; DOI:10.1161/CIRCULATIONAHA.114.011195 · 14.95 Impact Factor
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    ABSTRACT: Background Calcium dependent signaling mechanisms play a critical role in platelet activation. Unlike calcium-activated protease and kinase, the contribution of calcium-activated protein serine/threonine phosphatase in platelet activation is poorly understood.Objective To assess the role of catalytic subunit of protein phosphatase 2B (PP2B) or calcineurin in platelet function.ResultsHere, we showed that an increase in PP2B activity was associated with agonist-induced activation of human and murine platelets. Pharmacological inhibitors of the catalytic subunit of protein phosphatase 2B (PP2B-A) such as cyclosporine A (CsA) or tacrolimus (FK506) potentiated aggregation of human platelets. Murine platelets lacking the β isoform of PP2B-A (PP2B-Aβ-/-) displayed increased aggregation with low doses of agonist concentrations. Loss of PP2B-Aβ did not affect agonist-induced integrin αIIbβ3 inside-out signaling, but increased basal Src activation and outside-in αIIbβ3 signaling to p38 mitogen activated protein kinase (MAPK), with a concomitant enhancement in platelet spreading on immobilized fibrinogen and greater fibrin clot retraction. Fibrinogen induced increased p38 activation in PP2B-Aβ-/- platelets were blocked by Src inhibitor. Both PP2B-Aβ-/- platelets and PP2B-Aβ depleted human embryonal kidney 293 αIIbβ3 cells displayed increased adhesion to immobilized fibrinogen. Filamin A, an actin crosslinking phosphoprotein that is known to associate with β3 was dephosphorylated on Ser2152 in fibrinogen adhered wild type but not in PP2B-Aβ-/- platelets. In a FeCl3 injury thrombosis model, PP2B-Aβ-/- mice showed decreased time to occlusion in the carotid artery.Conclusion These observations suggest that PP2B-Aβ by suppressing outside-in αIIbβ3 integrin signaling limits platelet response to vascular injury.This article is protected by copyright. All rights reserved.
    Journal of Thrombosis and Haemostasis 10/2014; 12(12). DOI:10.1111/jth.12761 · 5.55 Impact Factor
  • Jeffery D Molkentin
    Circulation Research 09/2014; 115(8):e21-3. DOI:10.1161/CIRCRESAHA.114.305011 · 11.09 Impact Factor
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    ABSTRACT: Muscular dystrophy (MD) is a disease characterized by skeletal muscle necrosis and the progressive accumulation of fibrotic tissue. While transforming growth factor (TGF)-β has emerged as central effector of MD and fibrotic disease, the cell types in diseased muscle that underlie TGFβ-dependent pathology have not been segregated. Here we generated transgenic mice with myofiber-specific inhibition of TGFβ signaling due to expression of a TGFβ type II receptor dominant negative (dnTGFβRII) truncation mutant. Expression of dnTGFβRII in myofibers mitigated the dystrophic phenotype observed in δ-sarcoglycan-null (Sgcd(-/-)) mice through a mechanism involving reduced myofiber membrane fragility. The dnTGFβRII transgene also reduced muscle injury and improved muscle regeneration after cardiotoxin injury, as well as increased satellite cell numbers and activity. An unbiased global expression analysis revealed a number of potential mechanisms for dnTGFβRII mediated protection, one of which was induction of the antioxidant proteins metallothionein (Mt). Indeed, TGFβ directly inhibited Mt gene expression in vitro, the dnTGFβRII transgene conferred protection against ROS accumulation in dystrophic muscle, and treatment with Mt mimetics protected skeletal muscle upon injury in vivo and improved the membrane stability of dystrophic myofibers. Hence, our results show that the myofibers are central mediators of the deleterious effects associated with TGFβ signaling in MD.
    Human Molecular Genetics 08/2014; 23(25). DOI:10.1093/hmg/ddu413 · 6.68 Impact Factor
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    ABSTRACT: Rationale: Impairment of proteasomal function is pathogenic in a number of cardiac proteinopathies and can eventually lead to heart failure. Loss of proteasomal activity often results in the accumulation of large protein aggregates. The ubiquitin proteasome system (UPS) is primarily responsible for cellular protein degradation and, while the role of ubiquitination in this process is well studied, the function of an ancillary post-translational modification, SUMOylation, in protein quality control (PQC) is not fully understood. Objective: To determine the role of UBC9, a SUMO-conjugating enzyme, in cardiomyocyte PQC. Methods and Results: Gain- and loss-of-function approaches were used to determine the importance of UBC9. Overexpression of UBC9 enhanced UPS function in cardiomyocytes while knockdown of UBC9 by siRNA caused significant accumulations of aggregated protein. UPS function and relative activity was analyzed using a UPS reporter protein, GFPu. Subsequently, UBC9's effects on UPS function were tested in a proteotoxic model of desmin-related cardiomyopathy, caused by cardiomyocyte specific expression of a mutated alpha B crystallin, CryABR120G. CryABR120G expression leads to aggregate formation and decreased proteasomal function. Co-infection of UBC9-adenovirus with CryABR120G virus reduced the proteotoxic sequelae, decreasing overall aggregate concentrations. Conversely, knockdown of UBC9 significantly decreased UPS function in the model and resulted in increased aggregate levels. Conclusions: UBC9 plays a significant role in cardiomyocyte PQC and its activity can be exploited to reduce toxic levels of misfolded or aggregated proteins in cardiomyopathy.
    Circulation Research 08/2014; 115(8). DOI:10.1161/CIRCRESAHA.115.304760 · 11.09 Impact Factor
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    ABSTRACT: Rationale: The cellular and molecular basis for post myocardial infarction (MI) structural and functional remodeling is not well understood. Objective: To determine if Ca(2+) influx through transient receptor potential (canonical) (TRPC) channels contributes to post-MI structural and functional remodeling. Methods and Results: TRPC1/3/4/6 channel mRNA increased after MI in mice and was associated with TRPC-mediated Ca(2+) entry. Cardiac myocyte specific expression of a dominant negative (dn: loss of function) TRPC4 channel increased basal myocyte contractility and reduced hypertrophy and cardiac structural and functional remodeling after MI while increasing survival. We used adenovirus-mediated expression of TRPC3/4/6 channels in cultured adult feline myocytes (AFMs) to define mechanistic aspects of these TRPC-related effects. TRPC3/4/6 over expression in AFMs induced calcineurin (Cn)-Nuclear Factor of Activated T cells (NFAT) mediated hypertrophic signaling, which was reliant on caveolae targeting of TRPCs. TRPC3/4/6 expression in AFMs increased rested state contractions and increased spontaneous sarcoplasmic reticulum (SR) Ca(2+) sparks mediated by enhanced phosphorylation of the ryanodine receptor. TRPC3/4/6 expression was associated with reduced contractility and response to catecholamines during steady state pacing, likely due to enhanced SR Ca(2+) leak. Conclusions: Ca(2+) influx through TRPC channels expressed after MI activates pathological cardiac hypertrophy and reduces contractility reserve. Blocking post-MI TRPC activity improved post-MI cardiac structure and function.
    Circulation Research 07/2014; 115(6). DOI:10.1161/CIRCRESAHA.115.303831 · 11.09 Impact Factor
  • Jason Karch, Jeffery D Molkentin
    Proceedings of the National Academy of Sciences 07/2014; 111(29). DOI:10.1073/pnas.1410104111 · 9.81 Impact Factor
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    ABSTRACT: Muscular dystrophies are a group of genetic diseases that lead to muscle wasting and in most cases, premature death. Cytokines and inflammatory factors are released during the disease process where they promote deleterious signaling events that directly participate in myofiber death. Here we show that p38α, a kinase in the greater mitogen-activated protein kinase (MAPK) signaling network, serves as a nodal regulator of disease signaling in dystrophic muscle. Deletion of Mapk14 (p38α encoding gene) in the skeletal muscle of mdx (lacking dystrophin) or sgcd (δ-sarcoglycan encoding gene) null mice resulted in a significant reduction in pathology up to 6 months of age. We also generated MAPK kinase 6 (MKK6) muscle-specific transgenic mice to model heightened p38α disease signaling that occurs in dystrophic muscle, which resulted in severe myofiber necrosis and many hallmarks of muscular dystrophy. Mechanistically, we show that p38α directly induces myofiber death through a mitochondrial-dependent pathway involving direct phosphorylation and activation of the pro-death Bcl-2 family member Bax. Indeed, muscle-specific deletion of Bax, but not the apoptosis regulatory gene Tp53 (encoding p53), significantly reduced dystrophic pathology in the muscles of MKK6 transgenic mice. Moreover, use of a p38 MAPK pharmacologic inhibitor reduced dystrophic disease in Sgcd(-/-) mice suggesting a future therapeutic approach to delay disease.
    Human Molecular Genetics 05/2014; DOI:10.1093/hmg/ddu270 · 6.68 Impact Factor
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    ABSTRACT: The hearts of neonatal mice and adult zebrafish can regenerate after injury through proliferation of preexisting cardiomyocytes. However, adult mammals are not capable of cardiac regeneration because almost all cardiomyocytes exit their cell cycle. Exactly how the cell cycle exit is maintained and how many adult cardiomyocytes have the potential to reenter the cell cycle are unknown. The expression and activation levels of main cyclin-CDK complexes are extremely low or undetectable at adult stages. The nuclear DNA content of almost all cardiomyocytes is 2C, indicating the cell cycle exit from G1-phase. Here, we induced expression of cyclin D1, which regulates the progression of G1-phase, only in differentiated cardiomyocytes of adult mice. In these cardiomyocytes, S-phase marker positive cardiomyocytes and the expression of main cyclins and CDKs increased remarkably, although cyclin B1-CDK1 activation was inhibited in an ATM/ATR independent manner. The phosphorylation pattern of CDK1 and expression pattern of Cdc25 subtypes suggested that a deficiency in the increase in Cdc25 (a and -b), which is required for M-phase entry, inhibited the cyclin B1-CDK1 activation. Finally, analysis of cell cycle distribution patterns showed that more than 40% of adult mouse cardiomyocytes reentered the cell cycle by the induction of cyclin D1. The cell cycle of these binucleated cardiomyocytes was arrested before M-phase, and many mononucleated cardiomyocytes entered endoreplication. These data indicate that silencing the cyclin D1 expression is necessary for the maintenance of the cell cycle exit, and suggest a mechanism that involves inhibition of M-phase entry.
    Journal of Biological Chemistry 05/2014; 289(26). DOI:10.1074/jbc.M113.541953 · 4.60 Impact Factor

Publication Stats

27k Citations
3,260.69 Total Impact Points

Institutions

  • 2009–2015
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States
    • Hannover Medical School
      • Department of Cardiology and Angiology
      Hanover, Lower Saxony, Germany
    • Duke University
      Durham, North Carolina, United States
    • University of Maryland, Baltimore
      • Department of Physiology
      Baltimore, Maryland, United States
    • Washington University in St. Louis
      • Center for Pharmacogenomics
      Saint Louis, MO, United States
  • 2000–2015
    • University of Cincinnati
      • • Department of Pediatrics
      • • Department of Molecular and Cellular Physiology
      Cincinnati, Ohio, United States
    • Harvard University
      Cambridge, Massachusetts, United States
  • 2000–2014
    • Cincinnati Children's Hospital Medical Center
      • • Division of Molecular Cardiovascular Biology
      • • Department of Pediatrics
      Cincinnati, Ohio, United States
  • 2013
    • Temple University
      Filadelfia, Pennsylvania, United States
  • 2012
    • Childrens Hospital of Pittsburgh
      • Division of Pediatric Gastroenterology, Hepatology and Nutrition
      Pittsburgh, PA, United States
  • 2007–2012
    • University of Washington Seattle
      • Department of Physiology and Biophysics
      Seattle, WA, United States
    • University of Oslo
      Kristiania (historical), Oslo, Norway
    • University of Cologne
      Köln, North Rhine-Westphalia, Germany
    • Albany Medical College
      • Center for Immunology and Microbial Disease
      Albany, New York, United States
    • Boston University
      • Department of Biology
      Boston, Massachusetts, United States
  • 2011
    • Shanghai Jiao Tong University
      Shanghai, Shanghai Shi, China
  • 1996–2011
    • University of Texas Southwestern Medical Center
      • Department of Molecular Biology
      Dallas, Texas, United States
    • The American Society for Biochemistry and Molecular Biology
      Порт-Артур, Texas, United States
  • 2010
    • University of Bristol
      • School of Physiology and Pharmacology
      Bristol, ENG, United Kingdom
  • 2002–2006
    • University of Toronto
      • Division of Cardiology
      Toronto, Ontario, Canada
  • 2004
    • University of Freiburg
      Freiburg, Baden-Württemberg, Germany
  • 2003
    • Tufts University
      • Molecular Cardiology Research Institute (MCRI)
      Medford, MA, United States
    • Maastricht University
      • Department of Cardiology
      Maestricht, Limburg, Netherlands
  • 2001
    • Massachusetts General Hospital
      • Division of Cardiology
      Boston, MA, United States
  • 1996–1998
    • University of Texas at Dallas
      • Molecular Biology
      Richardson, Texas, United States
  • 1997
    • The Rockefeller University
      New York, New York, United States
  • 1994–1997
    • Medical College of Wisconsin
      • Department of Physiology
      Milwaukee, Wisconsin, United States