ABCA7 deficiency causes neuronal dysregulation by altering mitochondrial lipid metabolism

ABCA7 loss-of-function variants are associated with increased risk of Alzheimer's disease (AD). Using ABCA7 knockout human iPSC models generated with CRISPR/Cas9, we investigated the impacts of ABCA7 deficiency on neuronal metabolism and function. Lipidomics revealed that mitochondria-related phospholipids, such as phosphatidylglycerol and cardiolipin were reduced in the ABCA7-deficient iPSC-derived cortical organoids. Consistently, ABCA7 deficiency-induced alterations of mitochondrial morphology accompanied by reduced ATP synthase activity and exacerbated oxidative damage in the organoids. Furthermore, ABCA7-deficient iPSC-derived neurons showed compromised mitochondrial respiration and excess ROS generation, as well as enlarged mitochondrial morphology compared to the isogenic controls. ABCA7 deficiency also decreased spontaneous synaptic firing and network formation in iPSC-derived neurons, in which the effects were rescued by supplementation with phosphatidylglycerol or NAD+ precursor, nicotinamide mononucleotide. Importantly, effects of ABCA7 deficiency on mitochondria morphology and synapses were recapitulated in synaptosomes isolated from the brain of neuron-specific Abca7 knockout mice. Together, our results provide evidence that ABCA7 loss-of-function contributes to AD risk by modulating mitochondria lipid metabolism.

LRP1 in vascular mural cells modulates cerebrovascular integrity and function in the presence of APOE4

Cerebrovasculature is critical in maintaining brain homeostasis; its dysregulation often leads to vascular cognitive impairment and dementia (VCID) during aging. VCID is the second most prevalent cause of dementia in the elderly, after Alzheimer's disease (AD), with frequent cooccurrence of VCID and AD. While multiple factors are involved in the pathogenesis of AD and VCID, APOE4 increases the risk for both diseases. A major apolipoprotein E (apoE) receptor, the low-density lipoprotein receptor-related protein 1 (LRP1), is abundantly expressed in vascular mural cells (pericytes and smooth muscle cells). Here, we investigated how deficiency of vascular mural cell LRP1 affects the cerebrovascular system and cognitive performance using vascular mural cell-specific Lrp1-KO mice (smLrp1-/-) in a human APOE3 or APOE4 background. We found that spatial memory was impaired in the 13- to 16-month-old APOE4 smLrp1-/- mice but not in the APOE3 smLrp1-/- mice, compared with their respective littermate control mice. These disruptions in the APOE4 smLrp1-/- mice were accompanied with excess paravascular glial activation and reduced cerebrovascular collagen IV. In addition, blood-brain barrier (BBB) integrity was disrupted in the APOE4 smLrp1-/- mice. Together, our results suggest that vascular mural cell LRP1 modulates cerebrovasculature integrity and function in an APOE genotype-dependent manner.

Experimental method for haplotype phasing across the entire length of chromosome 21 in trisomy 21 cells using a chromosome elimination technique

Modern sequencing technologies produce a single consensus sequence without distinguishing between homologous chromosomes. Haplotype phasing solves this limitation by identifying alleles on the maternal and paternal chromosomes. This information is critical for understanding gene expression models in genetic disease research. Furthermore, the haplotype phasing of three homologous chromosomes in trisomy cells is more complicated than that in disomy cells. In this study, we attempted the accurate and complete haplotype phasing of chromosome 21 in trisomy 21 cells. To separate homologs, we established three corrected disomy cell lines (ΔPaternal chromosome, ΔMaternal chromosome 1, and ΔMaternal chromosome 2) from trisomy 21 induced pluripotent stem cells by eliminating one chromosome 21 utilizing the Cre-loxP system. These cells were then whole-genome sequenced by a next-generation sequencer. By simply comparing the base information of the whole-genome sequence data at the same position between each corrected disomy cell line, we determined the base on the eliminated chromosome and performed phasing. We phased 51,596 single nucleotide polymorphisms (SNPs) on chromosome 21, randomly selected seven SNPs spanning the entire length of the chromosome, and confirmed that there was no contradiction by direct sequencing.

A human isogenic iPSC-derived cell line panel identifies major regulators of aberrant astrocyte proliferation in Down syndrome

Astrocytes exert adverse effects on the brains of individuals with Down syndrome (DS). Although a neurogenic-to-gliogenic shift in the fate-specification step has been reported, the mechanisms and key regulators underlying the accelerated proliferation of astrocyte precursor cells (APCs) in DS remain elusive. Here, we established a human isogenic cell line panel based on DS-specific induced pluripotent stem cells, the XIST-mediated transcriptional silencing system in trisomic chromosome 21, and genome/chromosome-editing technologies to eliminate phenotypic fluctuations caused by genetic variation. The transcriptional responses of genes observed upon XIST induction and/or downregulation are not uniform, and only a small subset of genes show a characteristic expression pattern, which is consistent with the proliferative phenotypes of DS APCs. Comparative analysis and experimental verification using gene modification reveal dose-dependent proliferation-promoting activity of DYRK1A and PIGP on DS APCs. Our collection of human isogenic cell lines provides a comprehensive set of cellular models for further DS investigations.

Keiji Kawatani et al. developed a panel of Down syndrome (DS) isogenic astrocytes derived from iPSCs to observe the consequence of DS on astrocyte precursor proliferation, differentiation, and gene expression. Their results suggest a dose-dependent effect of DYRK1A and PIGP on DS-derived astrocyte precursor proliferation, and represent a valuable resource and cellular model for future DS research.

Elimination of protein aggregates prevents premature senescence in human trisomy 21 fibroblasts

Chromosome abnormalities induces profound alterations in gene expression, leading to various disease phenotypes. Recent studies on yeast and mammalian cells have demonstrated that aneuploidy exerts detrimental effects on organismal growth and development, regardless of the karyotype, suggesting that aneuploidy-associated stress plays an important role in disease pathogenesis. However, whether and how this effect alters cellular homeostasis and long-term features of human disease are not fully understood. Here, we aimed to investigate cellular stress responses in human trisomy syndromes, using fibroblasts and induced pluripotent stem cells (iPSCs). Dermal fibroblasts derived from patients with trisomy 21, 18 and 13 showed a severe impairment of cell proliferation and enhanced premature senescence. These phenomena were accompanied by perturbation of protein homeostasis, leading to the accumulation of protein aggregates. We found that treatment with sodium 4-phenylbutyrate (4-PBA), a chemical chaperone, decreased the protein aggregates in trisomy fibroblasts. Notably, 4-PBA treatment successfully prevented the progression of premature senescence in secondary fibroblasts derived from trisomy 21 iPSCs. Our study reveals aneuploidy-associated stress as a potential therapeutic target for human trisomies, including Down syndrome.

Role of Na(+)-K(+)-ATPase in sodium nitroprusside-induced relaxation of pulmonary artery under hypoxia

BACKGROUND

The sodium pump (Na(+)-K(+)-ATPase) plays a part in the regulation of smooth muscle contractility, and alterations of enzyme activity by hypoxia could contribute to the mechanism of hypoxic pulmonary vasoconstriction.

OBJECTIVE

To determine the role of Na(+)-K(+)-ATPase in the sodium nitroprusside (SNP)-induced relaxation of pulmonary artery in hypoxia.

METHODS

Using isolated canine pulmonary arterial rings, we measured the relaxant responses of KCI-contracted tissues to SNP under hyperoxic (95% O2, 5% O2) and hypoxic conditions (5% O2, 5% CO2, 90% N2 in vitro. Na(+)-K(+)-ATPase activity was assessed by measuring ouabain-sensitive (86)Rb uptake.

RESULTS

The SNP-induced relaxation was reduced under hypoxia, so that the maximal relaxation decreased from 80.1 +/- 8.6 to 57.8 +/- 6.8% (p < 0.01) and the concentration of SNP required to produce 50% relaxation increased from 1.9 +/- 0.4 x 10(-6) to 2.6 +/- 0.6 x 10(-5) M (p < 0.01). Addition of ouabain, an Na(+)-K(+)-ATPase inhibitor, attenuated the relaxant response to SNP and this inhibition was still observed under hypoxia. Incubation of endothelium-denuded rings with SNP caused dose-dependent increases in intracellular cGMP levels and ouabain-sensitive (86)Rb uptake, and these effects were not significantly altered by hypoxia.

CONCLUSION

These results suggest that sarcolemmal Na(+)-K(+)-ATPase activity may be implicated in the mechanism of nitrovasodilator-induced vasodilation of pulmonary artery and may still be functioning under hypoxia.

Inhibition of airway smooth muscle tone by Chinese herbal medicines

The aim of the present study was to elucidate whether Chinese traditional herbal drugs, Gorei-San (TJ-17) and Toki-Shakuyaku-San (TJ-23), affect airway smooth muscle tone and, if so, to determine what the mechanism of action is. Rabbit tracheal segments were isolated and the contractile responses to electrical field stimulation and acetylcholine were measured before and after the application of TJ-17 or TJ-23 under isometric conditions in vitro. Ouabain-sensitive rubidium-86 (86Rb) uptake by tissues in response to each drug was also measured. Each herbal medicine attenuated the contractile responses to electrical field stimulation and acetylcholine in a concentration-dependent manner, the maximal inhibition of acetylcholine-induced contraction being 37.5+/-4.9% for TJ-17 and 42.4+/-5.3% for TJ-23 (p<0.05 for each). These effects were not altered by mechanical removal of the epithelium, indomethacin, the nitric oxide synthase inhibitor NG -nitro-L-arginine methyl ester, the cyclic adenosine monophosphate (cAMP)-dependent protein kinase inhibitor adenosine 3'5'-cyclic monophosphorothioate (Rp-cAMPS), the cyclic guanosine monophosphate (cGMP)-dependent protein kinase inhibitor KT5823, or the calcium (Ca2+)-activated potassium (K+) channel inhibitor charybdotoxin, but were greatly inhibited in the presence of the sodium (Na+)-K+ adenosine triphosphatase (ATPase) inhibitor ouabain. Incubation of tissues with TJ-17 and TJ-23 dose dependently increased ouabain-sensitive 86Rb uptake. The results of the study suggest that both Gorei-San and Toki-Shakuyaku-San reduce airway smooth muscle tone via a postjunctional mechanism probably through stimulation of the sodium pump and the subsequent hyperpolarization/repolarization of the cell membrane. These effects may contribute to the antiasthmatic properties of these herbal medicines.

Ginsenoside-induced relaxation of human bronchial smooth muscle via release of nitric oxide

Ginsenoside, an extract of Panax ginseng, is an essential constituent of anti-asthmatic Chinese herbal medicine. To elucidate whether ginsenoside affects airway smooth muscle tone and, if so, what the mechanism of action is, we studied relaxant responses of human bronchial strips under isometric condition in vitro, and directly measured the release of nitric oxide (NO) by an amperometric sensor for this molecule. Addition of ginsenoside relaxed the tissues precontracted with acetylcholine in a dose-dependent manner, the maximal relaxation and the ginsenoside concentration required to produce 50% relaxation being 67+/-8% and 210+/-29 microg ml(-1), respectively. The relaxant responses to ginsenoside were inhibited by N(G)-nitro-L-arginine methylester (L-NAME) and removal of the epithelium, but not by N(G)-nitro-D-arginine methylester (D-NAME) or tetrodotoxin. This inhibitory effect of L-NAME was reversed by L-arginine but not by D-arginine. Addition of ginsenoside to the medium containing bronchial tissues dose-dependently increased NO-selective electrical current, and this effect was greatly attenuated by the epithelial removal or Ca(2+)-free medium. Ginsenoside also increased tissue cyclic GMP contents, an effect that was abolished in the presence of L-NAME. It is concluded that ginsenoside induces relaxation of human bronchial smooth muscle via stimulation of NO generation predominantly from airway epithelium and cyclic GMP synthesis. This action might account for the anti-asthmatic effect of Panax ginseng.

Effect of inhaled indomethacin in asthmatic patients taking high doses of inhaled corticosteroids

BACKGROUND

Cyclooxygenase products of arachidonic acid may play a part in bronchoconstriction and airway inflammation in asthma.

OBJECTIVE

We sought to determine the effect of inhaled indomethacin on asthma control and asthma exacerbations during reduction of inhaled corticosteroids in patients with moderate-to-severe steroid-dependent asthma.

METHODS

We conducted a double-blind, randomized, parallel-group, multicenter study in 38 patients with asthma taking high doses (> or =1500 microg/d) of beclomethasone dipropionate (BDP). After a run-in period, patients were assigned inhaled indomethacin (50 mg/d) or placebo for 6 weeks, during which the daily doses of BDP were reduced to half at week 2 and then to one third of the baseline dose at week 4.

RESULTS

Data were available from 34 patients. After the reduction of BDP doses, FEV(1), peak expiratory flow, asthma symptoms, and exhaled nitric oxide concentrations deteriorated in both treatment groups, but these effects were less pronounced in the indomethacin group compared with the placebo group. During the 6-week treatment period, 89% of the patients receiving placebo had relapse of asthma, whereas only 38% of those receiving inhaled indomethacin did so (P =.003).

CONCLUSION

Inhalation of indomethacin can reduce asthma exacerbations induced by reduction of high-dose inhaled corticosteroid in steroid-dependent asthma.

Repetitive use of a phosphate-binding module in DNA polymerase beta, Oct-1 POU domain and phage repressors

Motifs for sequence specific-protein-DNA interactions, such as helix-turn-helix, zinc finger and leucine zipper, are now better understood as a result of extensive studies of three-dimensional (3D) structures of transcription factors. On the other hand, little attention has been paid to motifs for sequence nonspecific binding, namely DNA-phosphate binding. To address the question whether different transcription factors and DNA manipulation enzymes, that is enzymes that work on DNA, share a similar mode of phosphate binding, we surveyed interactions between DNA and protein module, a structural unit of a globular protein. We analyzed the modular organization of DNA polymerase beta and found that residues making contact with DNA phosphates were localized to five modules. Structural comparison of these phosphate-binding modules against others in transcription factors and DNA manipulation enzymes revealed that DNA polymerase beta, the Oct-1 POU domain, 434 Cro and the Arc repressor have a phosphate-binding module with 3D structures similar to one another. This newly detected module, the phosphate-binding helix-turn-helix (pbHTH) module, named for its function and 3D structure, interacts with DNA by (i) making hydrogen bonds between a DNA phosphodiester oxygen and an amino hydrogen of the main chain located at the N-terminus of a C-terminal alpha-helix, and (ii) making electrostatic interactions between DNA phosphates and side chains of lysine or arginine. Finding structurally and functionally similar phosphate-binding units in different transcription factors and DNA manipulation enzymes suggests that shuffling of modules is not limited to the DNA base-recognition motif. Phosphate-binding modules are apparently also shuffled in DNA-binding proteins.

[A case of pulmonary eosinophilic granuloma undergoing spontaneous remission]

A case of pulmonary eosinophilic granuloma that underwent spontaneous remission is presented. A 23-year old man presented with dry cough and fever. Chest X-ray film revealed diffuse reticulo-nodular infiltrates in the middle and upper lung fields. Chest CT and HRCT showed multiple cystic lesions with thick walls and small nodules predominantly in the inner zone. Based on radiographic findings, pulmonary eosinophilic granuloma was suspected. Bronchoalveolar lavage cell data showed lymphocyte and eosinophil alveolitis with no increase of CD 1 lymphocytes. The symptoms and radiographic findings improved markedly within 4 months after the onset of symptoms without treatment and upon cessation of smoking. Chest CT and HRCT showed that the cystic walls were thinner and that the small nodules had decreased. Thoracoscopic lung biopsy revealed granulomatous lesions consisting of CD 1 and S-100 protein positive histiocytes with infiltration of eosinophils and fibrous lesions. Pulmonary eosinophilic granuloma was diagnosed. There has been no recurrence for 1 year.

Purification and properties of a proline iminopeptidase from apricot seeds

A proline iminopeptidase was purified about 18,000-fold from apricot seeds (Prunus armeniaca LINN.) by a five-step procedure comprised of extraction from seeds, ammonium sulfate fractionation, DEAE-cellulose chromatography, CM-Sepharose chromatography, and rechromatography on CM-Sepharose. The purified enzyme had a molecular weight of 220,000 by gel filtration and 55,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This indicates that the native enzyme may be composed of four identical subunits. The isoelectric point was 6.2 as determined by gel electrofocusing. The pH optimum for L-proline beta-naphthylamide was between pH 7.5 and 8.0, and the enzyme was stable in the pH 6.5-to-8.0 region and up to 40 degrees C. The enzyme was specific for L-proline beta-naphthylamide among various amino acid beta-naphthylamides, and it also hydrolzyed L-prolylglycine and L-prolylglycylglycine. The enzyme was strongly inhibited by p-chloromercuribenzoate, 5,5'-dithiobis(2-nitrobenzoic acid), N-ethylmaleimide, and heavy metal ions, but was not activated significantly by thiol compounds. Moreover, the enzyme was inactivated by diethyl pyrocarbonate, p-bromophenacyl bromide, and photooxidation, but was not affected by diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, bestatin, puromycin, or metal chelating agents. No activation of the enzyme was observed on addition of metal ions. These results suggest that the enzyme is not classifiable as a metalloenzyme, and that cysteine and histidine residues may participate in the enzyme activity.