Selenoprotein M Promotes Hypothalamic Leptin Signaling and Thioredoxin Antioxidant Activity

Aims: Selenoproteins are an essential class of proteins involved in redox signaling and energy metabolism. However, the functions of many selenoproteins are not clearly established. Selenoprotein M (SELENOM), an endoplasmic reticulum (ER)-resident oxidoreductase bearing structural similarity to thioredoxin (TXN), is among those yet to be fully characterized. This protein is highly expressed in hypothalamic regions involved in leptin signaling and has been previously linked to energy metabolism. Herein, we performed a series of studies using in vivo and in vitro models to probe the specific influence of SELENOM on hypothalamic leptin signaling and assess SELENOM-regulated pathways. Innovation and Results: Our initial experiment in vivo demonstrated that (i) leptin promotes hypothalamic expression of SELENOM and (ii) leptin-induced STAT3 phosphorylation is impeded by SELENOM deficiency. Additional in vitro studies using mHypoE-44 immortalized hypothalamic neurons corroborated these findings, as SELENOM deficiency obstructed downstream STAT3 phosphorylation and cytosolic calcium responses evoked by leptin treatment. Correspondingly, SELENOM overexpression enhanced leptin sensitivity. Microarray analysis conducted in parallel on hypothalamic tissue and mHypoE-44 cells revealed multiple genes significantly affected by SELENOM deficiency, including thioredoxin interacting protein, a negative regulator of the TXN system. Further analysis determined that (i) SELENOM itself possesses intrinsic TXN activity and (ii) SELENOM deficiency leads to a reduction in overall TXN activity. Finally, mHypoE-44 cells lacking SELENOM displayed diminished activation of the nuclear factor kappa-light-chain enhancer of activated B-cells (NF-κB) signaling pathway and increased susceptibility to ER stress-mediated cell death. Conclusion: In sum, these findings establish SELENOM as a positive regulator of leptin signaling and TXN antioxidant activity in the hypothalamus. Antioxid. Redox Signal. 35, 775-787.

Prepregnant Obesity of Mothers in a Multiethnic Cohort Is Associated with Cord Blood Metabolomic Changes in Offspring

Maternal obesity has become a growing global health concern that may predispose the offspring to medical conditions later in life. However, the metabolic link between maternal prepregnant obesity and healthy offspring has not yet been fully elucidated. In this study, we conducted a case-control study using a coupled untargeted and targeted metabolomic approach from the newborn cord blood metabolomes associated with a matched maternal prepregnant obesity cohort of 28 cases and 29 controls. The subjects were recruited from multiethnic populations in Hawaii, including rarely reported Native Hawaiian and other Pacific Islanders (NHPI). We found that maternal obesity was the most important factor contributing to differences in cord blood metabolomics. Using an elastic net regularization-based logistic regression model, we identified 29 metabolites as potential early-life biomarkers manifesting intrauterine effect of maternal obesity, with accuracy as high as 0.947 after adjusting for clinical confounding (maternal and paternal age, ethnicity, parity, and gravidity). We validated the model results in a subsequent set of samples (N = 30) with an accuracy of 0.822. Among the metabolites, six metabolites (galactonic acid, butenylcarnitine, 2-hydroxy-3-methylbutyric acid, phosphatidylcholine diacyl C40:3, 1,5-anhydrosorbitol, and phosphatidylcholine acyl-alkyl 40:3) were individually and significantly different between the maternal obese and normal-weight groups. Interestingly, hydroxy-3-methylbutyric acid showed significantly higher levels in cord blood from the NHPI group compared to that from Asian and Caucasian groups. In summary, significant associations were observed between maternal prepregnant obesity and offspring metabolomic alternation at birth, revealing the intergenerational impact of maternal obesity.

GNAI1 and GNAI3 Reduce Colitis-Associated Tumorigenesis in Mice by Blocking IL6 Signaling and Down-regulating Expression of GNAI2

BACKGROUND & AIMS

Interleukin 6 (IL6) and tumor necrosis factor contribute to the development of colitis-associated cancer (CAC). We investigated these signaling pathways and the involvement of G protein subunit alpha i1 (GNAI1), GNAI2, and GNAI3 in the development of CAC in mice and humans.

METHODS

B6;129 wild-type (control) or mice with disruption of Gnai1, Gnai2, and/or Gnai3 or conditional disruption of Gnai2 in CD11c+ or epithelial cells were given dextran sulfate sodium (DSS) to induce colitis followed by azoxymethane (AOM) to induce carcinogenesis; some mice were given an antibody against IL6. Feces were collected from mice, and the compositions of microbiomes were analyzed by polymerase chain reactions. Dendritic cells (DCs) and myeloid-derived suppressor cells (MDSCs) isolated from spleen and colon tissues were analyzed by flow cytometry. We performed immunoprecipitation and immunoblot analyses of colon tumor tissues, MDSCs, and mouse embryonic fibroblasts to study the expression levels of GNAI1, GNAI2, and GNAI3 and the interactions of GNAI1 and GNAI3 with proteins in the IL6 signaling pathway. We analyzed the expression of Gnai2 messenger RNA by CD11c+ cells in the colonic lamina propria by PrimeFlow, expression of IL6 in DCs by flow cytometry, and secretion of cytokines in sera and colon tissues by enzyme-linked immunosorbent assay. We obtained colon tumor and matched nontumor tissues from 83 patients with colorectal cancer having surgery in China and 35 patients with CAC in the United States. Mouse and human colon tissues were analyzed by histology, immunoblot, immunohistochemistry, and/or RNA-sequencing analyses.

RESULTS

GNAI1 and GNAI3 (GNAI1;3) double-knockout (DKO) mice developed more severe colitis after administration of DSS and significantly more colonic tumors than control mice after administration of AOM plus DSS. Development of increased tumors in DKO mice was not associated with changes in fecal microbiomes but was associated with activation of nuclear factor (NF) κB and signal transducer and activator of transcription (STAT) 3; increased levels of GNAI2, nitric oxide synthase 2, and IL6; increased numbers of CD4+ DCs and MDSCs; and decreased numbers of CD8+ DCs. IL6 was mainly produced by CD4+/CD11b+, but not CD8+, DCs in DKO mice. Injection of DKO mice with a blocking antibody against IL6 reduced the expansion of MDSCs and the number of tumors that developed after CAC induction. Incubation of MDSCs or mouse embryonic fibroblasts with IL6 induced activation of either NF-κB by a JAK2-TRAF6-TAK1-CHUK/IKKB signaling pathway or STAT3 by JAK2. This activation resulted in expression of GNAI2, IL6 signal transducer (IL6ST, also called GP130) and nitric oxide synthase 2, and expansion of MDSCs; the expression levels of these proteins and expansion of MDSCs were further increased by the absence of GNAI1;3 in cells and mice. Conditional disruption of Gnai2 in CD11c+ cells of DKO mice prevented activation of NF-κB and STAT3 and changes in numbers of DCs and MDSCs. Colon tumor tissues from patients with CAC had reduced levels of GNAI1 and GNAI3 and increased levels of GNAI2 compared with normal tissues. Further analysis of a public human colorectal tumor DNA microarray database (GSE39582) showed that low Gani1 and Gnai3 messenger RNA expression and high Gnai2 messenger RNA expression were significantly associated with decreased relapse-free survival.

CONCLUSIONS

GNAI1;3 suppresses DSS-plus-AOM-induced colon tumor development in mice, whereas expression of GNAI2 in CD11c+ cells and IL6 in CD4+/CD11b+ DCs appears to promote these effects. Strategies to induce GNAI1;3, or block GNAI2 and IL6, might be developed for the prevention or therapy of CAC in patients.

Emissivity Compensated Pyrometry of the Substrate Surface During Movpe Growth of InxGa1−xAs1−yPy/InP Materials in Rotating Disc Reactors

In order to overcome some of the inherent difficulties with applying conventional pyrometry to production scale rotating disc MOVPE reactors, the in-situ technique of emissivity compensated pyrometry has been applied. Due to the extreme temperature sensitivity of epitaxial processes involving InxGa1−xAs1−yPy, this material system provides the optimum proving grounds for this technology. With this temperature measurement technique, we have developed a method for measuring the temperature of the substrate during MOVPE growth in high speed rotating disc reactors that does not require any modification to the reactor hardware. Real world testing, during the growth of complex epitaxial structures involving the highly temperature sensitive InxGa1−xAs1−yPy quaternary, indicates a very strong correlation between the measured temperature of the substrate during growth, and actual epitaxial wafer measurements after growth. This temperature measurement system can be used to maintain the wavelength of the InxGa1−xAs1−yPy quaternary materials within a range of 2 nm.

Antibody to dengue 1 detected more than 60 years after infection

We investigated the duration of humoral responses to dengue virus infection in individuals who recalled experiencing dengue fever-like illnesses at the time of the Second World War, when dengue fever epidemics occurred throughout the Pacific and Southeast Asia. In July 1943 dengue fever reappeared in Hawaii following an interval of 31 years. Over the next 12 months a total of 1498 locally transmitted cases were reported, and at least 46 imported cases were identified, most of which were among members of the military returning from the Pacific Theatre of the war. Serum samples collected in 2005, more than 60 years after onset of symptoms, were tested for the presence of dengue-specific antibodies using a rapid ELISA test, and by plaque reduction neutralization test. Four of seven samples were positive for dengue-specific IgG and demonstrated neutralization titers >or=160 to dengue 1. We describe the existence of dengue-specific antibodies in the serum of people infected more than 60 years earlier.

A new approach for analyzing cellular infiltration during allergic airway inflammation

A mouse model for allergic airway inflammation involving ovalbumin (OVA) sensitization and challenge has been developed that reproduces hallmark features of human asthma and has provided valuable insight into the mechanisms by which this disease occurs. Cellular infiltrate in lungs of mice used in this model have conventionally been evaluated using histological examination of tissue sections and light microscopic analysis of lung lavage samples. As an alternative or complementary approach for characterizing cellular infiltrate, we developed a multicolor fluorescence-activated cell sorter (FACS) method involving the simultaneous detection of seven different markers on lung cell suspensions: CD4, CD8, B220, CD11b, Gr-1, CD49b, and FcepsilonRI. Only some of these cell types increased in OVA-challenged mice compared to PBS controls, including the CD4(+), B220(+), CD11b(+), and FcepsilonRI(+) groups. We also examined subpopulations of cells for coexpression of these markers and dissected heterogeneous populations as further evaluation procedures to characterize the cellular infiltrate resulting from OVA challenge. Finally, we combined FACS with real-time PCR to analyze certain cell types in terms of mRNA levels for factors involved in asthma, including GATA-3 and IL-1beta. Overall, these FACS-based techniques provide a powerful approach for analyzing cellular profiles in lung tissue from mice used in the mouse model of asthma and may also prove valuable in evaluating cellular infiltrates for other models of inflammation and immune responses.

Differential functional avidity of dengue virus-specific T-cell clones for variant peptides representing heterologous and previously encountered serotypes

Proinflammatory cytokines secreted by memory CD8+ and CD4+ T cells are thought to play a direct role in the pathogenesis of dengue virus infection by increasing vascular permeability and thereby inducing the pathophysiologic events associated with dengue hemorrhagic fever and dengue shock syndrome. Severe disease is frequently observed in the setting of secondary infection with heterologous dengue virus serotypes, suggesting a role for cross-reactive memory T cells in the immunopathogenesis of severe disease. We used a large panel of well-characterized dengue virus-specific CD8+ T-cell clones isolated from Pacific Islanders previously infected with dengue virus 1 to examine effector memory function, focusing on a novel dominant HLA-B*5502-restricted NS5(329-337) epitope, and assessed T-cell responses to stimulation with variant peptides representing heterologous serotypes. Variant peptides were differentially recognized by dengue virus 1-specific effector CD8+ cytotoxic T lymphocytes (CTL) in a heterogeneous and clone-specific manner, in which cytolytic function and cytokine secretion could be enhanced, diminished, or abrogated compared with cognate peptide stimulation. Dengue virus-specific CTL stimulated with cognate and variant peptides demonstrated a cytokine response hierarchy of gamma IFN (IFN-gamma) > tumor necrosis factor alpha (TNF-alpha) > interleukin-2 (IL-2), and a subset of clones also produced IL-4 and IL-6. Individual clones demonstrated greater avidity for variant peptides representing heterologous serotypes, including serotypes previously encountered by the subject, and IFN-gamma and TNF-alpha secretion was enhanced by stimulation with these heterologous peptides. Altered antiviral T-cell responses in response to stimulation with heterologous dengue virus serotypes have implications for control of virus replication and for disease pathogenesis.