Role of autophagy in inhibiting the proliferation of A549 cells by type III interferon

Prokaryotic expression of soluble IFN-λ1 recombinant protein with cold-shock system

Interferon (IFN)-λ1, a member of type III IFN, possesses unique antiviral, anti-tumor, and immune modulation properties. IFN-λ alone or combined with other drugs is considered an essential therapeutic regimen in the clinic. Obtaining high-quality, biologically-active recombinant human IFN-λ1 (rhIFN-λ1) is of great practical significance. In this study, pCold-II-IFN-λ1 expression plasmid was correctly constructed, the rhIFN-λ1 was expressed in BL21(DE3) E.coli and reached the highest level under the optimal condition of 15 °C culture temperature and at 1 μg/L IPTG induction for 12 h. The soluble rhIFN-λ1 was purified by Ni-NTA affinity chromatography. The purified rhIFN-λ1 can effectively activate the JAK1-STAT1 signaling pathway and induce the expression of a large number of interferon-stimulated genes (ISG) including ISG15, ISG54, ISG56, TRAIL, OAS1, MX1, IRF7 and IRF9. In addition, rhIFN-λ1 can effectively inhibit the growth/proliferation of cervical cancer HeLa cells in a dose-dependent pattern. Collectively, the soluble rhIFN-λ1 was successfully expressed in BL21(DE3) E.coli with the cold-shock system, and the purified rhIFN-λ1 demonstrated excellent biological activity. This study lays a solid basis for acquiring high-quality rhIFN-λ1 and its clinical application.

Generation of an A549 ISRE-Luciferase Stable Cell Line

With its human lung origin, A549 cell line is a designated cellular model for viral respiratory infections studies. As such infections are known to lead to innate immune responses, various IFN signaling modifications occur in infected cells and have to be considered in respiratory viruses experiments. Here, we describe the generation of an A549 stable cell line that expresses firefly luciferase upon interferon-β stimulation, as well as upon RIG-I transfection and upon influenza A virus infection. Of the 18 clones generated, the first one, namely A549-RING1, demonstrated appropriate luciferase expression in the different conditions tested. This newly established cell line may therefore be used to decipher the impact of viral respiratory infection on innate immune response depending on IFN stimulation, without any plasmid transfection step. A549-RING1 can be provided upon request.

The E3 ligase subunit FBXO45 binds the interferon-λ receptor and promotes its degradation during influenza virus infection

Influenza remains a major public health challenge, as the viral infection activates multiple biological networks linked to altered host innate immunity. Following infection, IFN-λ, a ligand crucial for the resolution of viral infections, is known to bind to its cognate receptor, IFNLR1, in lung epithelia. However, little is known regarding the molecular expression and regulation of IFNLR1. Here, we show that IFNLR1 is a labile protein in human airway epithelia that is rapidly degraded after influenza infection. Using an unbiased proximal ligation biotin screen, we first identified that the Skp-Cullin-F box E3 ligase subunit, FBXO45, binds to IFNLR1. We demonstrate that FBXO45, induced in response to influenza infection, mediates IFNLR1 protein polyubiquitination and degradation through the ubiquitin-proteasome system by docking with its intracellular receptor domain. Furthermore, we found ectopically expressed FBXO45 and its silencing in cells differentially regulated both IFNLR1 protein stability and interferon-stimulated gene expression. Mutagenesis studies also indicated that expression of a K319R/K320R IFNLR1 variant in cells exhibited reduced polyubiquitination, yet greater stability and proteolytic resistance to FBXO45 and influenza-mediated receptor degradation. These results indicate that the IFN-λ-IFNLR1 receptor axis is tightly regulated by the Skp-Cullin-F box ubiquitin machinery, a pathway that may be exploited by influenza infection as a means to limit antiviral responses.

Cloning and codon optimization of a novel feline interferon omega gene for production by Pichia pastoris and its antiviral efficacy in polyethylene glycol-modified form

Feline viral diseases, such as feline panleukopenia, feline infectious peritonitis, and feline coronaviral enteritis, seriously endanger the health of cats, and restrict the development of pet industry. Meanwhile, there is a current lack of effective vaccines to protect against feline viral diseases. Thus, effective therapeutic agents are highly desirable. Interferons (IFNs) are important mediators of the antiviral host defense in animals, particularly type I IFNs. In this study, a novel feline IFN omega (feIFN-ω) gene was extracted from the cat stimulated with feline parvovirus (FPV) combined with poly(I:C), and following codon optimization encoding the feIFN-ω, the desired gene (feIFN-ω’) fragment was inserted into plasmid pPICZαA, and transformed into Pichia pastoris GS115, generating a recombinant P. pastoris GS115 strain expressing the feIFN-ω’. After induction, we found that the expression level of the feIFN-ω’ was two times more than that of feIFN-ω (p < 0.01). Subsequently, the feIFN-ω’ was purified and modified with polyethylene glycol, and its antiviral efficacy was evaluated in vitro and in vivo, using vesicular stomatitis virus (VSV) and FPV as model virus. Our results clearly demonstrated that the feIFN-ω’ had significant antiviral activities on both homologous and heterologous animal cells in vitro. Importantly, the feIFN-ω’ can effectively promote the expression of antiviral proteins IFIT3, ISG15, Mx1, and ISG56, and further enhance host defense to eliminate FPV infection in vivo, suggesting a potential candidate for the development of therapeutic agent against feline viral diseases.

Cellular Mechanisms Involved in the Combined Toxic Effects of Diesel Exhaust and Metal Oxide Nanoparticles

Diesel exhaust particles (DEPs) and non-exhaust particles from abrasion are two main representative sources of air pollution to which humans are exposed daily, together with emerging nanomaterials, whose emission is increasing considerably. In the present work, we aimed to investigate whether DEPs, metal oxide nanoparticles (MeO-NPs), and their mixtures could affect alveolar cells. The research was focused on whether NPs induced different types of death in cells, and on their effects on cell motility and migration. Autophagy and cell cycles were investigated via cytofluorimetric analyses, through the quantification of the autophagic biomarker LC3B and PI staining, respectively. Cellular ultrastructures were then observed via TEM. Changes in cell motility and migration were assessed via transwell migration assay, and by the cytofluorimetric analysis of E-cadherin expression. A colony-forming efficiency (CFE) assay was performed in order to investigate the interactions between cells inside the colonies, and to see how these interactions change after exposure to the single particles or their mixtures. The results obtained suggest that NPs can either reduce the toxicity of DEPs (CuO) or enhance it (ZnO), through a mechanism that may involve autophagy as cells' response to stressors and as a consequence of particles' cellular uptake. Moreover, NPs can induce modification of E-cadherin expression and, consequentially, of colonies' phenotypes.

IFN-λ Modulates the Migratory Capacity of Canine Mammary Tumor Cells via Regulation of the Expression of Matrix Metalloproteinases and Their Inhibitors

Interactions between neoplastic and immune cells taking place in tumors drive cancer regulatory mechanisms both in humans and animals. IFN-λ, a potent antiviral factor, is also secreted in the tumor; however, its role in tumor development is still unclear. In our study, we investigate the influence of IFN-λ on the canine mammary tumor (CMT) cell survival and their metastatic potential in vitro. First, we examined, by Western blot, the expression of the IFN-λ receptor complex in three CMT cell lines (P114, CMT-U27 and CMT-U309). We showed that only two cell lines (P114 and CMT-U27) express both (IL-28RA and IL-10Rb) receptor subunits and respond to IFN-λ treatment by STAT phosphorylation and the expression of interferon-stimulated genes. Using MTT, crystal violet and annexin-V assays, we showed a minimal role of IFN-λ in CMT viability. However, IFN-λ administration had a contradictory effect on cell migration in the scratch test, namely, it increased P114 and decreased CMT-U27 motility. Moreover, we demonstrated that this process is related to the expression of extracellular matrix metalloproteinases and their inhibitors; furthermore, it is independent of Akt and ERK signaling pathways. To conclude, we showed that IFN-λ activity is reliant on the expression of two receptor subunits and tumor type, but further investigations are needed.

Antiangiogenic effect of arsenic trioxide in HUVECs by FoxO3a-regulated autophagy

Arsenic trioxide (ATO) has been shown to have antitumor effect in different tumors, although the underlying mechanisms are not fully understood. Autophagy plays a critical role in tumorigenesis and cancer therapy and has been found to be activated by ATO in different cells. However, the role of autophagy in the antitumor effect of ATO has not yet been elucidated. In this study, we investigated the role of autophagy in the antiangiogenic effect of ATO in human umbilical vein endothelial cells (HUVECs) in vitro and its underlying mechanism. Our data showed that ATO suppresses angiogenesis and induces autophagy in HUVECs through upregulation of forkhead box protein O3 (FoxO3a). Co-incubated with autophagy inhibitor or knockdown of FoxO3a effectively inhibited ATO-induced autophagy and reversed the antiangiogenic effect of ATO, indicating that ATO-induced autophagy plays an antiangiogenic role in HUVECs. Our results highlight the importance of autophagy in the antiangiogenic effect of ATO and provide an improved understanding of the function of ATO.