The Journal of biological chemistry
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Elucidation of Abeta-lowering agents that inhibit processing of the wild-type (WT) beta-secretase amyloid precursor protein (APP) site, present in most Alzheimer disease (AD) patients, is a logical approach for improving memory deficit in AD. The cysteine protease inhibitors CA074Me and E64d were selected by inhibition of beta-secretase activity in regulated secretory vesicles that produce beta-amyloid (Abeta). The regulated secretory vesicle activity, represented by cathepsin B, selectively cleaves the WT beta-secretase site but not the rare Swedish mutant beta-secretase site. ⋯ After inhibitor treatment, the improved memory function was accompanied by reduced amyloid plaque load, decreased Abeta40 and Abeta42, and reduced C-terminal beta-secretase fragment derived from APP by beta-secretase. However, the inhibitors had no effects on any of these parameters in mice expressing the Swedish mutant beta-secretase site of APP. The notable efficacy of these inhibitors to improve memory and reduce Abeta in an AD animal model expressing the WT beta-secretase APP site present in the majority of AD patients provides support for CA074Me and E64d inhibitors as potential AD therapeutic agents.
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Extracellular ATP, an autocrine or paracrine intercellular transmitter, is known to induce apoptosis in macrophages. However, the precise signaling mechanisms of ATP-induced apoptosis remain to be elucidated. Here we showed that activation of p38 mitogen-activated protein kinase (MAPK) plays a critical role in ATP-induced apoptosis. p38 activation and apoptosis in macrophages were induced by ATP. ⋯ Furthermore, ATP-induced ROS generation, p38 activation, and apoptosis were almost completely inhibited by selective P2X(7) receptor antagonists. We also found that ATP-induced apoptosis were diminished in ASK1-deficient macrophages accompanied by the lack of p38 activation. These results demonstrate that ROS-mediated activation of the ASK1-p38 MAPK pathway downstream of P2X(7) receptor is required for ATP-induced apoptosis in macrophages.
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Hutchinson-Gilford progeria syndrome is caused by the synthesis of a mutant form of prelamin A, which is generally called progerin. Progerin is targeted to the nuclear rim, where it interferes with the integrity of the nuclear lamina, causes misshapen cell nuclei, and leads to multiple aging-like disease phenotypes. We created a gene-targeted allele yielding exclusively progerin (Lmna HG) and found that heterozygous mice (Lmna HG/+) exhibit many phenotypes of progeria. ⋯ Lmna HG/LCO mice exhibited improved HG/LCO fibroblasts had fewer misshapen nuclei than Lmna HG/+ fibroblasts (p < 0.0001). A likely explanation for these differences was uncovered; the amount of progerin in Lmna HG/LCO fibroblasts and tissues was lower than in Lmna HG/+ fibroblasts and tissues. These studies suggest that compositional changes in the nuclear lamina can influence both the steady-state levels of progerin and the severity of progeria-like disease phenotypes.
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Extracellular superoxide dismutase (EC-SOD) is expressed at high levels in lungs. EC-SOD has a polycationic matrix-binding domain that binds to polyanionic constituents in the matrix. Previous studies indicate that EC-SOD protects the lung in both bleomycin- and asbestos-induced models of pulmonary fibrosis. ⋯ Intratracheal injection of crocidolite asbestos in mice leads to pulmonary inflammation and injury that is enhanced in EC-SOD knock-out mice. Notably, hyaluronan levels are increased in the bronchoalveolar lavage fluid after asbestos-induced pulmonary injury, and this response is markedly enhanced in EC-SOD knock-out mice. These data indicate that inhibition of oxidative hyaluronan fragmentation probably represents one mechanism by which EC-SOD inhibits inflammation in response to lung injury.