Interferon-resistant Daudi cells are deficient in interferon-alpha-induced ISGF3 alpha activation, but remain sensitive to the interferon-alpha-induced increase in ISGF3 gamma content

Dietary Betaine Addition Promotes Hepatic Cholesterol Synthesis, Bile Acid Conversion, and Export in Rats

It is widely reported how betaine addition regulates lipid metabolism but how betaine affects cholesterol metabolism is still unknown. This study aimed to investigate the role of betaine in hepatic cholesterol metabolism of Sprague-Dawley rats. Rats were randomly allocated to four groups and fed with a basal diet or a high-fat diet with or without 1% betaine. The experiment lasted 28 days. The results showed that dietary betaine supplementation reduced the feed intake of rats with final weight unchanged. Serum low-density-lipoprotein cholesterol was increased with the high-fat diet. The high-fat diet promoted cholesterol synthesis and excretion by enhancing the HMG-CoA reductase and ABCG5/G8, respectively, which lead to a balance of hepatic cholesterol. Rats in betaine groups showed a higher level of hepatic total cholesterol. Dietary betaine addition enhanced cholesterol synthesis as well as conversion of bile acid from cholesterol by increasing the levels of HMGCR and CYP7A1. The high-fat diet decreased the level of bile salt export pump, while dietary betaine addition inhibited this decrease and promoted bile acid efflux and increased total bile acid levels in the intestine. In summary, dietary betaine addition promoted hepatic cholesterol metabolism, including cholesterol synthesis, conversion of bile acids, and bile acid export.

Innate immune defects in HIV permissive cell lines

Background

Primary CD4+ T cells and cell lines differ in their permissiveness to HIV infection. Impaired innate immunity may contribute to this different phenotype.

Findings

We used transcriptome profiling of 1503 innate immunity genes in primary CD4+ T cells and permissive cell lines. Two clusters of differentially expressed genes were identified: a set of 249 genes that were highly expressed in primary cells and minimally expressed in cell lines and a set of 110 genes with the opposite pattern. Specific to HIV, HEK293T, Jurkat, SupT1 and CEM cell lines displayed unique patterns of downregulation of genes involved in viral sensing and restriction. Activation of primary CD4+ T cells resulted in reversal of the pattern of expression of those sets of innate immunity genes. Functional analysis of prototypical innate immunity pathways of permissive cell lines confirmed impaired responses identified in transcriptome analyses.

Conclusion

Integrity of innate immunity genes and pathways needs to be considered in designing gain/loss functional genomic screens of viral infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0275-8) contains supplementary material, which is available to authorized users.

Effect of double-stranded RNA and interferon on the antiviral activity of Atlantic salmon cells against infectious salmon anemia virus and infectious pancreatic necrosis virus

Type I interferons (IFN) establish an antiviral state in vertebrate cells by inducing expression of Mx and other antiviral proteins. We have studied the effect of Atlantic salmon interferon-like activity (AS-IFN) and poly I:C on the Mx protein expression and antiviral activity against infectious salmon anaemia virus (ISAV) and infectious pancreatic necrosis virus (IPNV) in the Atlantic salmon cell lines SHK-1 and TO. The double-stranded RNA poly I:C is an inducer of type I IFN in vertebrates. A cell cytotoxicity assay and measurements of virus yield were used to measure protection of cells against virus infection. Maximal induction of Mx protein in TO and SHK-1 cells occurred 48 h after poly I:C stimulation and 24 h after AS-IFN stimulation. TO cells pretreated with AS-IFN or poly I:C were protected from infection with IPNV 24 to 96 h after stimulation. Poly I:C or AS-IFN induced a minor protection against ISAV infection in SHK-1 cells, but no protection was induced against ISAV in TO cells. Western blot analysis showed that ISAV induced expression of Mx protein in TO and SHK-1 cells whereas IPNV did not induce Mx protein expression. These results suggest that ISAV and IPNV have very different sensitivities to IFN-induced antiviral activity and have developed different strategies to avoid the IFN-system of Atlantic salmon. Moreover, Atlantic salmon Mx protein appears not to inhibit replication of ISAV.

Molecular cloning of ADIR, a novel interferon responsive gene encoding a protein related to the torsins

The expression of the previously uncharacterized gene Adir (for ATP dependent interferon responsive gene) was increased by 5- to 15-fold in tissue of the oral cavity or in spleen and liver of mice treated orally or intraperitoneally with IFN-alpha, and in mouse cells treated in vitro with IFN-alpha or IFN-gamma. The level of Adir mRNA was also increased 20- to 40-fold in the brains of animals infected with encephalomyocarditis virus. Adir is expressed ubiquitously in mouse tissues as 1.9-, 2.4-, and 3.5-kb mRNA transcripts encoding a 385-amino-acid protein with a conserved ATP binding domain containing typical nucleotide and Mg(2+) binding sites. We also characterized the human ortholog, ADIR, which is located on chromosome 1q25-q31 and contains six exons encoding a 397-amino-acid protein with 80% homology to the mouse protein. A single 2.3-kb mRNA was detected in all human tissues examined, except for placenta, which also contained a 1.25-kb tissue-specific transcript generated by alternative splicing and encoding a putative 336-amino-acid protein. Although ADIR exhibits low homology to DYT1 and TOR1B, the deduced ADIR protein sequences are highly homologous to torsin A and torsin B and more distantly related to members of the Clp/HSP100 family of proteins, suggesting that ADIR, like torsins, is related to the AAA chaperone-like family of ATPases. An ADIR-EGFP fusion protein expressed in HeLa cells was shown to be associated with the endoplasmic reticulum.

Interferon-alpha resistance in renal carcinoma cells is associated with defective induction of signal transducer and activator of transcription 1 which can be restored by a supernatant of phorbol 12-myristate 13-acetate stimulated peripheral blood mononuclear cells

Therapy of selected human malignancies with interferon-alpha is widely accepted but often complicated by the emergence of interferon-alpha resistance. Interferon is a pleiotropic cytokine with antiproliferative, antitumour, antiviral and immunmodulatory effect; it signals through the Jak-STAT signal transduction pathway where signal transducer and activator of transcription 1 plays an important role. Here we report both, a lack of signal transducer and activator of transcription induction in interferon-alpha resistant renal cell carcinoma cells and signal transducer and activator of transcription 1 reinduction of phorbol 12-myristate 13-acetate-stimulated peripheral blood mononuclear cells supernatant. Preliminary experiments on the identification of the molecules that reinducing signal transducers and activators of transcription 1 indicate that interferon-gamma may be the responsible candidate cytokine, but several others may be involved as well. This work provides the basis for therapeutic strategies directed at the molecular modulation of interferon-alpha resistance in human neoplasms.

Interferon-resistant human melanoma cells are deficient in ISGF3 components, STAT1, STAT2, and p48-ISGF3gamma

The mechanism of IFN resistance was examined in three long-term cell lines, SK-MEL-28, SK-MEL-3, and MM96, exhibiting significant variation in responsiveness to the antiproliferative and antiviral effects of type I IFNs. The JAK-STAT components involved in IFN signal transduction were analyzed in detail. After exposure to IFN, activation of the IFN type I receptor-linked tyrosine kinases, JAK-1 and TYK-2, was detected at similar levels in both IFN-sensitive and IFN-resistant cell types, indicating that IFN resistance did not result from a deficiency in signaling at the level of receptor-associated kinase activation. However, analysis of ISGF3 transcription factor components, STAT1, STAT2, and p48-ISGF3gamma, revealed that their expression and activation correlated with cellular IFN responsiveness. The analysis was extended to also include IFN-sensitive primary melanocytes, three additional IFN-resistant melanoma cell lines, and seven cell cultures recently established from melanoma patient biopsies. It was consistently observed that the most marked difference in ISGF3 was a lack of STAT1 in the resistant versus the sensitive cells. Transfection of the IFN-resistant MM96 cell line to express increased levels of STAT1 protein partially restored IFN responsiveness in an antiviral assay. We conclude that a defect in the level of STAT1 and possibly all three ISGF3 components in IFN-resistant human melanoma cells may be a general phenomenon responsible for reduced cellular responsiveness of melanomas to IFNs.

Regulation of interferon-alpha responsiveness by the duration of Janus kinase activity

Daudi B lymphoblastoid cells are highly sensitive to the anti-growth and anti-viral effects of interferon (IFN). Unlike many cell lines, these cells show prolonged transcription of IFN-stimulated genes following treatment with IFN-alpha. This prolonged response correlated with the continued presence of the activated transcription factor, IFN-stimulated gene factor 3 (ISGF3). Pulse-chase labeling experiments indicated that the half-life of the phosphorylation of signal transducers and activators of transcription (Stat)1 and Stat2 was short (<2 h) although the turnover of the proteins themselves was slow (>24 h), indicative of a constitutive phosphatase activity. The administration of protein-tyrosine kinase inhibitors at any time point during IFN stimulation led to rapid inhibition of the response, indicating that tyrosine kinase activity was continuously required. Catalytic activity of Jak1 and Tyk2 kinases remained elevated for prolonged periods following stimulation. Continuous presence of IFN-alpha was necessary for maintaining prolonged activation of ISGF3 and of Janus kinases, an activity that was blocked by antibodies to IFN-alpha or by cycloheximide. Conditioned medium of IFN-alpha-stimulated cells was capable of stimulating STAT activation in naive cells. Taken together, these results suggest that the response to IFN-alpha is controlled by the duration of stimulated Janus kinase activity over the background of constitutive dephosphorylation and that this response can be sustained by autocrine secretion of IFN-alpha.

Characterization of a gastric tumor cell line defective in MHC class I inducibility by both alpha- and gamma-interferon

Alpha/beta and gamma type interferons (IFN), act through distinct cell surface receptors and induce transcription of an overlapping sets of genes. MHC class I genes are inducible by both type of interferons. We have analyzed a gastric tumor cell line, AGS, which was completely defective in MHC class I response to interferon-alpha and gamma. Northern blot analysis demonstrated that the lack of IFN response was related with the absence of up-regulation of specific HLA class I mRNA. Electrophoretic mobility shift assays in various tumor cell lines after IFN-alpha and IFN-gamma treatment showed differential binding of the transcriptional factors to MHC class I regulatory elements. Comparison of kappa-B binding activity showed that IFN-alpha and IFN-gamma induced opposite changes in NF-kappa B binding activity in AGS cells, indicating that the absence of MHC class I response in AGS appears to be independent of kappa-B activity. In contrast, there were remarkable differences in the level of transcriptional factor binding to an interferon-responsive sequence element (IRSE), between AGS and other interferon-responsive tumor cell lines. This result suggests that the low level of transcriptional factor binding to IRSE in AGS cells was responsible of the lack of induction of MHC class I antigens. In this context, overlapping factors in the signal transduction pathway of both type I and II interferons may be involved in the non-responsiveness of this gastric carcinoma tumor cell line.