Myeloid-Derived Suppressor Cells Are Controlled by Regulatory T Cells via TGF-β during Murine Colitis

Myeloid-derived suppressor cells (MDSCs) are well known regulators of regulatory T cells (Treg cells); however, the direct regulation of MDSCs by Treg cells has not been well characterized. We find that colitis caused by functional deficiency of Treg cells leads to altered expansion and reduced function of MDSCs. During differentiation of MDSCs in vitro from bone marrow cells, Treg cells enhanced MDSC function and controlled their differentiation through a mechanism involving transforming growth factor-β (TGF-β). TGF-β-deficient Treg cells were not able to regulate MDSC function in an experimentally induced model of colitis. Finally, we evaluated the therapeutic effect of TGF-β-mediated in-vitro-differentiated MDSCs on colitis. Adoptive transfer of MDSCs that differentiated with TGF-β led to better colitis prevention than the transfer of MDSCs that differentiated without TGF-β. Our results demonstrate an interaction between Treg cells and MDSCs that contributes to the regulation of MDSC proliferation and the acquisition of immunosuppressive functions

Carbon Monoxide Poisoning and Developing Ischemic Heart Disease: A Nationwide Population-Based Nested Case-Control Study

Although there are several case reports showing that carbon monoxide (CO) poisoning causes ischemic heart disease (IHD), no large-scale epidemiological studies have shown a significant association between the two. To investigate the association between CO poisoning and IHD, a nested case-control study of 28,113 patients who experienced CO poisoning and 28,113 controls matched by sex and age was performed using the nationwide health database of South Korea. Based on a conditional logistic regression, there was a significantly higher risk of IHD among the CO poisoning group than among the control group (adjusted hazard ratio [HR], 2.16; 95% confidence interval [CI], 1.87–2.49). The risk of IHD after CO poisoning was higher among the younger age group under 40 years (adjusted HR, 4.85; 95% CI, 3.20–7.35), and it was much greater among those with comorbidities (adjusted HR, 10.69; 95% CI, 2.41–47.51). The risk of IHD was the highest within the first two years after CO poisoning (adjusted HR, 11.12; 95% CI, 4.54–27.22). Even if more than six years had passed, the risk was still significantly higher than among the control group (adjusted HR, 1.55; 95% CI, 1.27–1.89). The analyses imply that CO poisoning is associated with an increased risk of IHD

Independent Relationship between Amyloid Precursor Protein (APP) Dimerization and γ-Secretase Processivity

<div><p>Altered production of β-amyloid (Aβ) from the amyloid precursor protein (APP) is closely associated with Alzheimer’s disease (AD). APP has a number of homo- and hetero-dimerizing domains, and studies have suggested that dimerization of β-secretase derived APP carboxyl terminal fragment (CTFβ, C99) impairs processive cleavage by γ-secretase increasing production of long Aβs (e.g., Aβ1-42, 43). Other studies report that APP CTFβ dimers are not γ-secretase substrates. We revisited this issue due to observations made with an artificial APP mutant referred to as 3xK-APP, which contains three lysine residues at the border of the APP ectodomain and transmembrane domain (TMD). This mutant, which dramatically increases production of long Aβ, was found to form SDS-stable APP dimers, once again suggesting a mechanistic link between dimerization and increased production of long Aβ. To further evaluate how multimerization of substrate affects both initial γ-secretase cleavage and subsequent processivity, we generated recombinant wild type- (WT) and 3xK-C100 substrates, isolated monomeric, dimeric and trimeric forms of these proteins, and evaluated both ε-cleavage site utilization and Aβ production. These show that multimerization significantly impedes γ-secretase cleavage, irrespective of substrate sequence. Further, the monomeric form of the 3xK-C100 mutant increased long Aβ production without altering the initial ε-cleavage utilization. These data confirm and extend previous studies showing that dimeric substrates are not efficient γ-secretase substrates, and demonstrate that primary sequence determinants within APP substrate alter γ-secretase processivity.</p></div

Recombinant 3xK-C100Flag monomer increased longer Aβ peptides.

<p>(A) The purified monomer, dimer, and trimer of recombinant 3xK-C100Flag were loaded on a SDS-PAGE gel and identified from the gel stained by Coomassie blue. The size of the monomer was at ∼12 kDa (black arrow), the dimer was at ∼24 kDa (grey arrow), and the trimer was at ∼36 kDa (open arrow). (B–C) Western blot of the purified monomer, dimer, and trimer 3xK-C100Flag substrates before/after IVA did not show significant changes in relative amounts of the various multimers. (D) Aβ ELISAs showed that Aβ production measured from 3xK-C100Flag dimer substrate is significantly reduced compared to that from 3xK-C100Flag monomer, but that there is no evidence for major shifts in Aβ ratios (E). Aβ profiles generated from IP/MS of the media show that for 3xK-C100Flag there is increased relative production of longer Aβ isoforms compared to WT substrate (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111553#pone-0111553-g002" target="_blank">Figure 2</a>). Molecular mass (m/z) of monomeric 3xK-C100Flag for Aβ40 is 4588.43 (calculated m/z: 4589.27), for Aβ42 is 4773.07 (calculated m/z: 4773.51), and for Aβ45 is 5084.52 (calculated m/z: 5086.90). 3xK-C100Flag dimer and trimer showed decreased Aβ levels compared to the monomer. Molecular mass of dimeric 3xK-C100Flag for Aβ40 is 4587.48 (calculated m/z: 4589.27) and for Aβ42 is 4769.235 (calculated m/z: 4773.51). (F) AICD profiles show that C49-99 and C50-99 are the dominant peaks for 3xK-C100Flag monomer and that this profile is similar to that observed for WT substrate. Molecular mass (m/z) of monomeric 3xK-C100Flag for AICD50-99 is 6915.460 (calculated m/z: 6905.66), for AICD49-99 is 7027.141 (calculated m/z: 7018.82). AICD production from 3xK-C100Flag dimer and trimer is markedly decreased in comparison to monomer. This experiment was performed twice with duplicates. Results were analyzed by two-way analysis of variance (ANOVA) followed by bonferroni post hoc testing (****<i>p</i><0.0001).</p

An APP dimer in 3xK-APP mutant-overexpressing CHO cells.

<p>(A) Schematic of WT-APP and 3xK-APP mutant. (B) Aβ profile analyzed by IP/MS demonstrated increased Aβ42 and Aβ43 levels of the mutant compared to WT. (C) APP dimer bands migrated at ∼200 kDa along with APP monomer bands at ∼100 kDa in a 3–8% tris-acetate gel. Both WT APP and 3xK-APP were normally processed to CTFα and CTFβ, but 3xK-APP produced less CTFα and CTFβ than WT-APP (Also see Figure S1 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111553#pone.0111553.s001" target="_blank">File S1</a>).</p