Biomedicines (Oct 2023)

Cytokine-Induced iNOS in A549 Alveolar Epithelial Cells: A Potential Role in COVID-19 Lung Pathology

  • Amelia Barilli,
  • Giulia Recchia Luciani,
  • Rossana Visigalli,
  • Roberto Sala,
  • Maurizio Soli,
  • Valeria Dall’Asta,
  • Bianca Maria Rotoli

DOI
https://doi.org/10.3390/biomedicines11102699
Journal volume & issue
Vol. 11, no. 10
p. 2699

Abstract

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Background. In COVID-19, an uncontrolled inflammatory response might worsen lung damage, leading to acute respiratory distress syndrome (ARDS). Recent evidence points to the induction of inducible nitric oxide synthase (NOS2/iNOS) as a component of inflammatory response since NOS2 is upregulated in critical COVID-19 patients. Here, we explore the mechanisms underlying the modulation of iNOS expression in human alveolar cells. Methods. A549 WT and IRF1 KO cells were exposed to a conditioned medium of macrophages treated with SARS-CoV-2 spike S1. Additionally, the effect of IFNγ, IL-1β, IL-6, and TNFα, either alone or combined, was addressed. iNOS expression was assessed with RT-qPCR and Western blot. The effect of baricitinib and CAPE, inhibitors of JAK/STAT and NF-kB, respectively, was also investigated. Results. Treatment with a conditioned medium caused a marked induction of iNOS in A549 WT and a weak stimulation in IRF1 KO. IFNγ induced NOS2 and synergistically cooperated with IL-1β and TNFα. The inhibitory pattern of baricitinb and CAPE indicates that cytokines activate both IRF1 and NF-κB through the JAK/STAT1 pathway. Conclusions. Cytokines secreted by S1-activated macrophages markedly induce iNOS, whose expression is suppressed by baricitinib. Our findings sustain the therapeutic efficacy of this drug in COVID-19 since, besides limiting the cytokine storm, it also prevents NOS2 induction.

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