Thomas Böttger

Cardiomyocyte-specific IκB kinase (IKK)/NF-κB activation induces reversible inflammatory cardiomyopathy and heart failure

Inflammation is a major factor in heart disease. IκB kinase (IKK) and its downstream target NF-κB are regulators of inflammation and are activated in cardiac disorders, but their precise contributions and targets are unclear. We analyzed IKK/NF-κB function in the heart by a gain-of-function approach, generating an inducible transgenic mouse model with cardiomyocyte-specific expression of constitutively active IKK2. In adult animals, IKK2 activation led to inflammatory dilated cardiomyopathy and heart failure. Transgenic hearts showed infiltration with CD11b+ cells, fibrosis, fetal reprogramming, and atrophy of myocytes with strong constitutively active IKK2 expression. Upon transgene inactivation, the disease was reversible even at an advanced stage. IKK-induced cardiomyopathy was dependent on NF-κB activation, as in vivo expression of IκBα superrepressor, an inhibitor of NF-κB, prevented the development of disease. Gene expression and proteomic analyses revealed enhanced expression of inflammatory cytokines, and an IFN type I signature with activation of the IFN-stimulated gene 15 (ISG15) pathway. In that respect, IKK-induced cardiomyopathy resembled Coxsackievirus-induced myocarditis, during which the NF-κB and ISG15 pathways were also activated. Vice versa, in cardiomyocytes lacking the regulatory subunit of IKK (IKKγ/NEMO), the induction of ISG15 was attenuated. We conclude that IKK/NF-κB activation in cardiomyocytes is sufficient to cause cardiomyopathy and heart failure by inducing an excessive inflammatory response and myocyte atrophy.

Cardiac Deletion of Smyd2 Is Dispensable for Mouse Heart Development

Chromatin modifying enzymes play a critical role in cardiac differentiation. Previously, it has been shown that the targeted deletion of the histone methyltransferase, Smyd1, the founding member of the SET and MYND domain containing (Smyd) family, interferes with cardiomyocyte maturation and proper formation of the right heart ventricle. The highly related paralogue, Smyd2 is a histone 3 lysine 4- and lysine 36-specific methyltransferase expressed in heart and brain. Here, we report that Smyd2 is differentially expressed during cardiac development with highest expression in the neonatal heart. To elucidate the functional role of Smyd2 in the heart, we generated conditional knockout (cKO) mice harboring a cardiomyocyte-specific deletion of Smyd2 and performed histological, functional and molecular analyses. Unexpectedly, cardiac deletion of Smyd2 was dispensable for proper morphological and functional development of the murine heart and had no effect on global histone 3 lysine 4 or 36 methylation. However, we provide evidence for a potential role of Smyd2 in the transcriptional regulation of genes associated with translation and reveal that Smyd2, similar to Smyd3, interacts with RNA Polymerase II as well as to the RNA helicase, HELZ.

Inhibition of Notch2 by Numb/Numblike controls myocardial compaction in the heart

AIMS The ventricular wall of the heart is composed of trabeculated and compact layers, which are separated by yet unknown processes during embryonic development. Here, we wanted to explore the role of Notch2 and Numb/Numblike for myocardial trabeculation and compaction. METHODS AND RESULTS We found that Notch2 activity is specifically down-regulated in the compact layer during cardiac development in the mouse. The biological role of Notch2 down-regulation was investigated by the expression of constitutively active Notch2 in the myocardium of transgenic mice, resulting in hypertrabeculation, reduced compaction, and ventricular septum defects. To disclose the mechanism that inhibited Notch2 activity during the formation of myocardial layers, we analysed potential suppressors of Notch signalling. We unveiled that concomitant but not separate ablation of Numb and Numblike in the developing heart leads to increased Notch2 activity along with hypertrabeculation, reduced compaction, and ventricular septum defects, phenocopying effects gained by overexpression of constitutively active Notch2. Expression profiling revealed a strong up-regulation of Bmp10 in Numb/Numblike mutant hearts, which might also interfere with trabeculation and compaction. CONCLUSION This study identified potential novel roles of Numb/Numblike in regulating trabeculation and compaction by inhibiting Notch2 and Bmp10 signalling.

Characterization of a Newly Developed Aircraft-Based Laser Ablation Aerosol Mass Spectrometer (ALABAMA) and First Field Deployment in Urban Pollution Plumes over Paris During MEGAPOLI 2009

We present here the development and first field deployment of a novel Aircraft-based Laser ABlation Aerosol MAss spectrometer (ALABAMA), which is capable of measuring the chemical composition and size of individual ambient aerosol particles in the size range between 150 and 900 nm. The instrument uses a continuous wave 532 nm laser to size and detect the particles, a pulsed 266 nm laser to ablate and ionize the particles, and a bipolar, Z-shaped time-of-flight mass spectrometer to detect positive and negative ions. The ALABAMA fits into a 19”-aircraft rack of 150 cm height and has a total weight of 140 kg, thus currently being one of the smallest and lightest-weight instruments of its type. We present a detailed characterization of ALABAMA with respect to particle beam width, detection and ablation efficiency, and example mass spectra of different particle types. The first aircraft-based field mission was performed within the MEGAPOLI summer campaign in July 2009 around Paris, France, onboard an ATR42 aircraft. During 11 research flights, corresponding to a total measuring time of approximately 44 hours, ALABAMA measured 6502 single particle mass spectra. The mass spectra were classified into eight particle classes using distinctive markers for each particle type. The most abundant particle types contained organic and secondary inorganic compounds. The results further show that differences in the abundance of observed particle types between different air masses are very pronounced when comparing air masses arriving from the greater Paris area with air masses arriving from other directions.