α1-Antitrypsin Combines with Plasma Fatty Acids and Induces Angiopoietin-like Protein 4 Expression.

α1-Antitrypsin (A1AT) purified from human plasma upregulates expression and release of angiopoietin-like protein 4 (Angptl4) in adherent human blood monocytes and in human lung microvascular endothelial cells, providing a mechanism for the broad immune-regulatory properties of A1AT independent of its antiprotease activity. In this study, we demonstrate that A1AT (Prolastin), a potent inducer of Angptl4, contains significant quantities of the fatty acids (FA) linoleic acid (C18:2) and oleic acid (C18:1). However, only trace amounts of FAs were present in preparations that failed to increase Angplt4 expression, for example, A1AT (Zemaira) or M-type A1AT purified by affinity chromatography. FA pull-down assays with Western blot analysis revealed a FA-binding ability of A1AT. In human blood-adherent monocytes, A1AT-FA conjugates upregulated expression of Angptl4 (54.9-fold, p < 0.001), FA-binding protein 4 (FABP4) (11.4-fold, p < 0.001), and, to a lesser degree, FA translocase (CD36) (3.1-fold, p < 0.001) relative to A1AT devoid of FA (A1AT-0). These latter effects of A1AT-FA were blocked by inhibitors of peroxisome proliferator-activated receptor (PPAR) ß/δ (ST247) and PPARγ (GW9662). When compared with controls, cell pretreatment with ST247 diminished the effect of A1AT-LA on Angptl4 mRNA (11.6- versus 4.1-fold, p < 0.001) and FABP4 mRNA (5.4- versus 2.8-fold, p < 0.001). Similarly, preincubation of cells with GW9662 inhibited inducing effect of A1AT-LA on Angptl4 mRNA (by 2-fold, p < 0.001) and FABP4 mRNA (by 3-fold, p < 0.001). Thus, A1AT binds to FA, and it is this form of A1AT that induces Angptl4 and FABP4 expression via a PPAR-dependent pathway. These findings provide a mechanism for the unexplored area of A1AT biology independent of its antiprotease properties.

Large-scale hematopoietic differentiation of human induced pluripotent stem cells provides granulocytes or macrophages for cell replacement therapies.

Interleukin-3 (IL-3) is capable of supporting the proliferation of a broad range of hematopoietic cell types, whereas granulocyte colony-stimulating factor (G-CSF) and macrophage CSF (M-CSF) represent critical cytokines in myeloid differentiation. When this was investigated in a pluripotent-stem-cell-based hematopoietic differentiation model, IL-3/G-CSF or IL-3/M-CSF exposure resulted in the continuous generation of myeloid cells from an intermediate myeloid-cell-forming complex containing CD34(+) clonogenic progenitor cells for more than 2 months. Whereas IL-3/G-CSF directed differentiation toward CD45(+)CD11b(+)CD15(+)CD16(+)CD66b(+) granulocytic cells of various differentiation stages up to a segmented morphology displaying the capacity of cytokine-directed migration, respiratory burst response, and neutrophil-extracellular-trap formation, exposure to IL-3/M-CSF resulted in CD45(+)CD11b(+)CD14(+)CD163(+)CD68(+) monocyte/macrophage-type cells capable of phagocytosis and cytokine secretion. Hence, we show here that myeloid specification of human pluripotent stem cells by IL-3/G-CSF or IL-3/M-CSF allows for prolonged and large-scale production of myeloid cells, and thus is suited for cell-fate and disease-modeling studies as well as gene- and cell-therapy applications.

Cell-type-specific downregulation of heme oxygenase-1 by lipopolysaccharide via Bach1 in primary human mononuclear cells.

Heme oxygenase (HO)-1 is the inducible isoform of the heme-degrading enzyme HO, which is upregulated by multiple stress stimuli. HO-1 has major immunomodulatory and anti-inflammatory effects via its cell-type-specific functions in mononuclear cells. Contradictory findings have been reported on HO-1 regulation by the Toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS) in these cells. Therefore, we reinvestigated the effects of LPS on HO-1 gene expression in human and murine mononuclear cells in vitro and in vivo. Remarkably, LPS downregulated HO-1 in primary human peripheral blood mononuclear cells (PBMCs), CD14(+) monocytes, macrophages, dendritic cells, and granulocytes, but upregulated this enzyme in primary murine macrophages and human monocytic leukemia cell lines. Furthermore, experiments with human CD14(+) monocytes revealed that activation of other TLRs including TLR1, -2, -5, -6, -8, and -9 decreased HO-1 mRNA expression. LPS-dependent downregulation of HO-1 was specific, because expression of cyclooxygenase-2, NADP(H)-quinone oxidoreductase-1, and peroxiredoxin-1 was increased under the same experimental conditions. Notably, LPS upregulated expression of Bach1, a critical transcriptional repressor of HO-1. Moreover, knockdown of this nuclear factor enhanced basal and LPS-dependent HO-1 expression in mononuclear cells. Finally, downregulation of HO-1 in response to LPS was confirmed in PBMCs from human individuals subjected to experimental endotoxemia. In conclusion, LPS downregulates HO-1 expression in primary human mononuclear cells via a Bach1-mediated pathway. As LPS-dependent HO-1 regulation is cell-type- and species-specific, experimental findings in cell lines and animal models need careful interpretation.

Acute-phase protein α1-antitrypsin--a novel regulator of angiopoietin-like protein 4 transcription and secretion.

The angiopoietin-like protein 4 (angptl4, also known as peroxisome proliferator-activated receptor [PPAR]γ-induced angiopoietin-related protein) is a multifunctional protein associated with acute-phase response. The mechanisms accounting for the increase in angptl4 expression are largely unknown. This study shows that human α1-antitrypsin (A1AT) upregulates expression and release of angplt4 in human blood adherent mononuclear cells and in primary human lung microvascular endothelial cells in a concentration- and time-dependent manner. Mononuclear cells treated for 1 h with A1AT (from 0.1 to 4 mg/ml) increased mRNA of angptl4 from 2- to 174-fold, respectively, relative to controls. In endothelial cells, the maximal effect on angptl4 expression was achieved at 8 h with 2 mg/ml A1AT (11-fold induction versus controls). In 10 emphysema patients receiving A1AT therapy (Prolastin), plasma angptl4 levels were higher relative to patients without therapy (nanograms per milliliter, mean [95% confidence interval] 127.1 [99.5-154.6] versus 76.8 [54.8-98.8], respectively, p = 0.045) and correlated with A1AT levels. The effect of A1AT on angptl4 expression was significantly diminished in cells pretreated with a specific inhibitor of ERK1/2 activation (UO126), irreversible and selective PPARγ antagonist (GW9662), or genistein, a ligand for PPARγ. GW9662 did not alter the ability of A1AT to induce ERK1/2 phosphorylation, suggesting that PPARγ is a critical mediator in the A1AT-driven angptl4 expression. In contrast, the forced accumulation of HIF-1α, an upregulator of angptl4 expression, enhanced the effect of A1AT. Thus, acute-phase protein A1AT is a physiological regulator of angptl4, another acute-phase protein.

Cellular uptake of Clostridium difficile TcdA and truncated TcdA lacking the receptor binding domain.

The combined repetitive oligopeptides (CROPs) of Clostridium difficile toxins A (TcdA) and B (TcdB) induce clathrin-mediated endocytosis of the toxins. Inconsistently, CROP-truncated TcdA(1-1874) is also capable of entering host cells and displaying full cytotoxic properties although with less potency. Pre-incubation of cells with isolated CROPs, however, reconstitutes the reduced uptake of TcdA(1-1874) to the level of the full-length toxin. We believe that TcdA exhibits an additional binding motif beyond the C-terminally located CROP domain, which might interact with cellular receptor structures that are associated with alternative internalization pathways. This study therefore evaluated endocytosis routes of CROP-dependent cellular uptake for TcdA and CROP-independent cellular uptake for TcdA(1-1874). Clathrin knockdown or inhibition with chlorpromazine affected subsequent internalization of TcdA and TcdA(1-1874), although only to some extent, arguing for alternative, clathrin-independent endocytosis routes. Inhibition of dynamin, a GTPase essentially involved in clathrin-mediated endocytosis as well as in various clathrin-independent uptake mechanisms, affected uptake of TcdA to the same extent as clathrin inhibition. In contrast, uptake of TcdA(1-1874) was almost completely eliminated in dynamin-inhibited cells. Thus, clathrin-independent uptake of TcdA(1-1874) presumably depends on dynamin. These findings demonstrate that the toxins are endocytosed via complex pathways involving clathrin and dynamin, putatively enabling them to adapt to mechanisms of various cell types. With regard to the emergence of C. difficile strains producing C-terminally truncated toxins, this study emphasizes the relevance of elucidating toxin uptake as a prerequisite for the development of toxin intervention strategies.

Should TSPYL1 mutation screening be included in routine diagnostics of male idiopathic infertility?

OBJECTIVE: To investigate a putative role of TSPYL1 in male idiopathic infertility. DESIGN: Clinical article. SETTING: University hospital. PATIENT(S): A total of 104 infertile men were selected with idiopathic nonobstructive azoospermia, cryptozoospermia, oligozoospermia, oligonecrozoospermia, and oligoasthenoteratozoospermia (OAT) syndrome, along with a control group of 106 men with proven paternity. INTERVENTION(S): Mutation screening of the coding region and parts of the 5' and 3' untranslated regions of the TSPYL1 gene was performed by polymerase chain reaction and sequencing. MAIN OUTCOME MEASURE(S): Occurrence of TSPYL1 single-nucleotide polymorphisms (SNPs) and mutations. RESULT(S): In these cohorts, eight known TSPYL1 SNPs were identified, none of which was significantly associated with male infertility. Two potentially disease-causing variants were detected in the infertile cohort: one man with azoospermia was found to be heterozygous for the novel TSPYL1 variant c.419C>G (p.Ser140Cys), and the rare substitution c.1098C>A (p.Phe366Leu) was identified in a man with OAT syndrome in the heterozygous state. Additionally, one fertile man was found to be heterozygous for the rare variant c.487G>A (p.Val163Ile). In silico analyses predicted a nonpathogenic effect for all amino acid exchanges, although protein features might be affected by p.Ser140Cys and p.Phe366Leu, respectively. CONCLUSION(S): Mutations in the TSPYL1 gene do not seem to play a major role in the pathogenesis of idiopathic male infertility, and mutation screening of the TSPYL1 gene can currently not be recommended in routine diagnostics of idiopathic male infertility.