Mesoionische Sechsringheterocyclen, III Reaktionen o-chinoider Verbindungen mit 6-Oxo-6H-1,3-diazin-1-ium-4-olaten

Mesoionische 6-Oxo-6H-1,3-diazin-1-ium-4-olate 9 reagieren mit Tetrachlor-o-benzochinon (2, R = Cl) unter Bildung von 1:1-Addukten 12, die sich formal von den Ketentautomeren 13 von 9 ableiten. Die Struktur von 12f wurde durch eine Röntgenstrukturanalyse geklärt

Cytoskeleton’s Role in KIR2.1 Trafficking

Alteration of the inward rectifier current IK1, carried by KIR2.1 channels, affects action potential duration, impacts resting membrane stability and associates with cardiac arrhythmias. Congenital and acquired KIR2.1 malfunction frequently associates with aberrant ion channel trafficking. Cellular processes underlying trafficking are intertwined with cytoskeletal function. The extent to which the cytoskeleton is involved in KIR2.1 trafficking processes is unknown. We aimed to quantify the dependence of KIR2.1 trafficking on cytoskeleton function. GFP or photoconvertible Dendra2 tagged KIR2.1 constructs were transfected in HEK293 or HeLa cells. Photoconversion of the Dendra2 probe at the plasma membrane and subsequent live imaging of trafficking processes was performed by confocal laser-scanning microscopy. Time constant of green fluorescent recovery (τg,s) represented recruitment of new KIR2.1 at the plasma membrane. Red fluorescent decay (τr,s) represented internalization of photoconverted KIR2.1. Patch clamp electrophysiology was used to quantify IKIR2.1. Biochemical methods were used for cytoskeleton isolation and detection of KIR2.1 cytoskeleton interactions. Cytochalasin B (20 μM), Nocodazole (30 μM) and Dyngo-4a (10 nM) were used to modify the cytoskeleton. Chloroquine (10 μM, 24 h) was used to impair KIR2.1 breakdown. Cytochalasin B and Nocodazole, inhibitors of actin and tubulin filament formation respectively, strongly inhibited the recovery of green fluorescence at the plasma membrane suggestive for inhibition of KIR2.1 forward trafficking [τg,s 13 ± 2 vs. 131 ± 31* and 160 ± 40* min, for control, Cytochalasin B and Nocodazole, respectively (*p < 0.05 vs. control)]. Dyngo-4a, an inhibitor of dynamin motor proteins, strongly slowed the rate of photoconverted channel internalization, whereas Nocodazole and Cytochalasin B had less effect [τr,s 20 ± 2 vs. 87 ± 14*, 60 ± 16 and 64 ± 20 min (*p < 0.05 vs. control)]. Cytochalasin B treatment (20 μM, 24 h) inhibited IKIR2.1. Chloroquine treatment (10 μM, 24 h) induced intracellular aggregation of KIR2.1 channels and enhanced interaction with the actin/intermediate filament system (103 ± 90 fold; p < 0.05 vs. control). Functional actin and tubulin cytoskeleton systems are essential for forward trafficking of KIR2.1 channels, whereas initial backward trafficking relies on a functional dynamin system. Chronic disturbance of the actin system inhibits KIR2.1 currents. Internalized KIR2.1 channels become recruited to the cytoskeleton, presumably in lysosomes

Tissue-specific suppression of thyroid hormone signaling in various mouse models of aging

DNA damage contributes to the process of aging, as underscored by premature aging syndromes caused by defective DNA repair. Thyroid state changes during aging, but underlying mechanisms remain elusive. Since thyroid hormone (TH) is a key regulator of metabolism, changes in TH signaling have widespread effects. Here, we reveal a significant common transcriptomic signature in livers from hypothyroid mice, DNA repair-deficient mice with severe (Csbm/m/Xpa-/-) or intermediate (Ercc1-/Δ-7) progeria and naturally aged mice. A strong induction of TH-inactivating deiodinase D3 and decrease of TH-activating D1 activities are observed in Csbm/m/Xpa-/- livers. Similar findings are noticed in Ercc1-/Δ-7, in naturally aged animals and in wild-type mice exposed to a chronic subtoxic dose of DNAdamaging agents. In contrast, TH signaling in muscle, heart and brain appears unaltered. These data show a strong suppression of TH signaling in specific peripheral organs in premature and normal aging, probably lowering metabolism, while other tissues appear to preserve metabolism. D3-mediated TH inactivation is unexpected, given its expression mainly in fetal tissues. Our studies highlight the importance of DNA damage as the underlying mechanism of changes in thyroid state. Tissue-specific regulation of deiodinase activities, ensuring diminished TH signaling, may contribute importantly to the protective metabolic response in aging

Tissue-Specific Suppression of Thyroid Hormone Signaling in Various Mouse Models of Aging

DNA damage contributes to the process of aging, as underscored by premature aging syndromes caused by defective DNA repair. Thyroid state changes during aging, but underlying mechanisms remain elusive. Since thyroid hormone (TH) is a key regulator of metabolism, changes in TH signaling have widespread effects. Here, we reveal a significant common transcriptomic signature in livers from hypothyroid mice, DNA repair-deficient mice with severe (Csbm/m/Xpa-/-) or intermediate (Ercc1-/Δ-7) progeria and naturally aged mice. A strong induction of TH-inactivating deiodinase D3 and decrease of TH-activating D1 activities are observed in Csbm/m/Xpa-/- livers. Similar findings are noticed in Ercc1-/Δ-7, in naturally aged animals and in wild-type mice exposed to a chronic subtoxic dose of DNA-damaging agents. In contrast, TH signaling in muscle, heart and brain appears unaltered. These data show a strong suppression of TH signaling in specific peripheral organs in premature and normal aging, probably lowering metabolism, while other tissues appear to preserve metabolism. D3-mediated TH inactivation is unexpected, given its expression mainly in fetal tissues. Our studies highlight the importance of DNA damage as the underlying mechanism of changes in thyroid state. Tissue-specific regulation of deiodinase activities, ensuring diminished TH signaling, may contribute importantly to the protective metabolic response in aging.status: publishe

Tissue-specific suppression of thyroid hormone signaling in various mouse models of aging

DNA damage contributes to the process of aging, as underscored by premature aging syndromes caused by defective DNA repair. Thyroid state changes during aging, but underlying mechanisms remain elusive. Since thyroid hormone (TH) is a key regulator of metabolism, changes in TH signaling have widespread effects. Here, we reveal a significant common transcriptomic signature in livers from hypothyroid mice, DNA repair-deficient mice with severe (Csbm/m/Xpa-/-) or intermediate (Ercc1-/Δ-7) progeria and naturally aged mice. A strong induction of TH-inactivating deiodinase D3 and decrease of TH-activating D1 activities are observed in Csbm/m/Xpa-/- livers. Similar findings are noticed in Ercc1-/Δ-7, in naturally aged animals and in wild-type mice exposed to a chronic subtoxic dose of DNAdamaging agents. In contrast, TH signaling in muscle, heart and brain appears unaltered. These data show a strong suppression of TH signaling in specific peripheral organs in premature and normal aging, probably lowering metabolism, while other tissues appear to preserve metabolism. D3-mediated TH inactivation is unexpected, given its expression mainly in fetal tissues. Our studies highlight the importance of DNA damage as the underlying mechanism of changes in thyroid state. Tissue-specific regulation of deiodinase activities, ensuring diminished TH signaling, may contribute importantly to the protective metabolic response in aging

Thyroid state in skeletal muscle of progeroid and naturally aged mice.

<p>T3 concentrations (A) and activities of D2 (B) and D3 (C) in muscle of 15-day-old WT and XAA (Csbm/m/Xpa-/-) mice (n = 3/group). T4 (D) and T3 (E) concentrations and activities of D2 (F) and D3 (G) in muscle of 18-week-old WT and MAA (Ercc1-/Δ-7) mice (n = 3/group). T4 (H) and T3 (I) concentrations and activities of D2 (J) and D3 (K) in muscle of 26-, 104-, and 130-week-old WT mice (n = 3-5/group). Values represent mean ± SE per group. * P < 0.05</p

Thyroid state in brains of progeroid and naturally aged mice.

<p>Homogenates of whole brain or hemispheres were used. T4 (A) and T3 (B) concentrations in brains of 7-, 12-, 15-, and 18-day-old WT (squares) and XAA (Csbm/m/Xpa-/-) mice (n = 3/group). Activities of D2 (C) and D3 (D) brains of 7-, 12-, 15-, and 18-day-old WT and XAA (Csbm/m/Xpa-/-) mice (n = 3/group). T4 (E) and T3 (F) concentrations and D3 activity (G) in brains of 4-, and 18-week-old WT (black bars) and MAA (Ercc-/Δ-7) (white bars) mice (n = 3/group). It was not possible to measure D2 activity due to technical constraints. Values represent mean ± SE per group. * P < 0.05; ** P < 0.01; *** P < 0.001.</p

Thyroid state in serum of progeroid and naturally aged mice.

<p>Serum T4 (A) and T3 (B) concentrations in 7-, 12-, 15-, and 18-day-old WT (squares) and XAA (Csbm/m/Xpa-/-) mice (circles) (n = 3/group). Serum T4 (C) and T3 (D) concentrations in 4-, and 18-week-old WT (black bars) and MAA (Ercc1-/Δ-7) (white bars) mice (n = 3/group). Serum T4 and T3 concentrations in 26-, 104-, and 130-week-old WT male mice (n = 3-4/group) (E). Serum TSH levels in 15-day old WT and XAA (Csbm/m/Xpa-/-) mice (F) and in 26-, 104-, and 130-week-old WT male mice (G). Values represent mean ± SE per group. * P < 0.05; ** P < 0.01; *** P < 0.001; # P = 0.054.</p

Liver D1 and D3 activity in DEHP-treated WT mice.

<p>Activities of D1 (A) and D3 (B) in 10-wk-old WT animals after exposure or not to subtoxic doses of the pro-oxidant DEHP for 2, 12 and 39 weeks. Values represent mean ± SE per group (n = 5). * P < 0.05; ** P < 0.01.</p