Respiratory syncytial virus infection up-regulates TLR7 expression by inducing oxidative stress via the Nrf2/ARE pathway in A549 cells
In order to better understand the early pathways of the pathogenesis of, and immune response to, RSV, herein, we explored the relationship between TLR7 expression and oxidative stress induction following RSV infection in A549 cells. We studied the intervening effects of the Nrf2/ARE pathway agonist butylated hydroxyanisole (BHA) and inhibitor trigonelline (TRI) on TLR7 modulation or oxidative stress induction. For comparison purposes, we set up seven treatment groups in this study, including RSV-treated cells, BHA + RSV-treated cells, TRI + RSV-treated cells, normal cell controls, inactivated RSV controls, BHA controls and TRI controls. We measured changes in TLR7, IL-6, TNF-α mRNA using RT-PCR and IL-6, TNF-α and IL-1β protein using ELISA as well as TLR7, Nrf2 and HO-1 protein using Western blot in A549 cells from the different treatment groups. We also assessed changes in cell proliferation and measured changes in ·OH and NO in A549 cells from the different treatment groups. The results indicate that TLR7 up-regulation is related to RSV infection and the induction of oxidative stress and that TLR7 expression was mediated by the anti-inflammatory effects of Nrf2/ARE pathway inhibitors or agonists. Our experiments may help elucidate the underlying pathology of RSV infection and suggest potential therapeutic targets for drug development and the prevention of RSV-induced human diseases.
Respiratory syncytial virus
Toll-like receptor 7
NF-E2-related factor 2
Chronic obstructive pulmonary disease
Reactive oxygen species
Human laryngeal carcinoma epithelial cells
We thank Ms. Xiao-yan Zhang for her technical assistance and LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
- 4.Marshak-Rothstein A, Rifkin IR (2007) Immunologically active autoantigens: the role of toll-like receptors in the development of chronic inflammatory disease. Annu Rev Immunol 25:419–441. https://doi.org/10.1146/annurev.immunol.22.012703.104514 CrossRefPubMedGoogle Scholar
- 7.Hosakote YM, Jantzi PD, Esham DL et al (2011) Viral-mediated inhibition of antioxidant enzymes contributes to the pathogenesis of severe respiratory syncytial virus bronchiolitis. Am J Respir Crit Care Med 183:1550–1560. https://doi.org/10.1164/rccm.201010-1755OC CrossRefPubMedPubMedCentralGoogle Scholar
- 17.Komaravelli N, Tian B, Ivanciuc T et al (2015) Respiratory syncytial virus infection down-regulates antioxidant enzyme expression by triggering deacetylation-proteasomal degradation of Nrf2. Free Radic Biol Med 88:391–403. https://doi.org/10.1016/j.freeradbiomed.2015.05.043 CrossRefPubMedPubMedCentralGoogle Scholar
- 22.Zeng H, Chen Q, Zhao B (2004) Genistein ameliorates beta-amyloid peptide (25–35)-induced hippocampal neuronal apoptosis. Free Radic Biol Med 36:180–188. https://doi.org/10.1016/j.freeradbiomed.2003.10.018 CrossRefPubMedGoogle Scholar
- 24.Kalaivani P, Saranya S, Poornima P et al (2014) Biological evaluation of new nickel(II) metallates: synthesis, DNA/protein binding and mitochondrial mediated apoptosis in human lung cancer cells (A549) via ROS hypergeneration and depletion of cellular antioxidant pool. Eur J Med Chem 82:584–599. https://doi.org/10.1016/j.ejmech.2014.05.075 CrossRefPubMedGoogle Scholar
- 25.Zhang Q, Zhao H, Wang L et al (2012) Effects of wind-dispelling drugs and deficiency-nourishing drugs of Houshiheisan compound prescription on astrocyte activation and inflammatory factor expression in the corpus striatum of cerebral ischemia rats. Neural Regen Res 7:1851–1857. https://doi.org/10.3969/j.issn.1673-5374.2012.24.002 PubMedPubMedCentralGoogle Scholar
- 27.Kaul P, Biagioli MC, Singh I et al (2000) Rhinovirus-induced oxidative stress and interleukin-8 elaboration involves p47-phox but is independent of attachment to intercellular adhesion molecule-1 and viral replication. J Infect Dis 181:1885–1890. https://doi.org/10.1086/315504 CrossRefPubMedGoogle Scholar
- 29.Sharma B, Altman JK, Goussetis DJ et al (2011) Protein kinase R as mediator of the effects of interferon (IFN) gamma and tumor necrosis factor (TNF) alpha on normal and dysplastic hematopoiesis. J Biol Chem 286:27506–27514. https://doi.org/10.1074/jbc.M111.238501 CrossRefPubMedPubMedCentralGoogle Scholar
- 32.Komaravelli N, Ansar M, Garofalo RP et al (2017) Respiratory syncytial virus induces NRF2 degradation through a promyelocytic leukemia protein-ring finger protein 4 dependent pathway. Free Radic Biol Med 113:494–504. https://doi.org/10.1016/j.freeradbiomed.2017.10.380 CrossRefPubMedGoogle Scholar
- 37.Gjyshi O, Bottero V, Veettil MV et al (2014) Kaposi’s sarcoma-associated herpesvirus induces Nrf2 during de novo infection of endothelial cells to create a microenvironment conducive to infection. PLoS Pathog 10:e1004460. https://doi.org/10.1371/journal.ppat.1004460 CrossRefPubMedPubMedCentralGoogle Scholar