IL-22Ra1 is induced during influenza infection by direct and indirect TLR3 induction of STAT1

Abstract

Background Influenza attacks the epithelium of the lung, causing cell death and disruption of the epithelial barrier leading to fluid buildup in the lung and impairment of gas exchange. Limited treatment options for severe influenza pneumonia prioritize the need for the discovery of effective therapies. IL-22 is a cytokine that promotes tissue integrity and has strong promise as a treatment option. While research has been focused on the cytokine itself, there is limited understanding of the regulation of the IL-22 receptor (IL-22Ra1) at the epithelial surface during infection. Methods IL-22Ra1 levels were measured by qRT-PCR, western blot and immunofluorescence following H1N1 influenza infection (A/PR/8/34 H1N1) or synthetic TLR3 mimetic, Poly (I:C). Regulation of the receptor was determined using STAT inhibitors (STAT1, STAT3 and PanSTAT inhibitors), TLR3 inhibition, and neutralization of interferon alpha receptor 2 (IFNAR2). Significance was determined by a p -value of greater than 0.05. Significance between two groups was measured using unpaired t-test and significance between more than two groups was measured using one-way ANOVA with Tukey Multiple Comparison Test. Results Here we show both in vivo and in vitro that IL-22Ra1 was induced as early as 24 h after influenza (H1N1 PR8) infection. This induction was triggered by toll-like receptor 3 (TLR3) as a TLR3 mimetic [Poly (I:C)] also induced IL-22Ra1 and inhibition of endosomal formation required for TLR3 function inhibited this process. This upregulation was dependent upon IFNβ signaling through STAT1. Importantly, induction of IL-22Ra1 significantly increased IL-22 signaling as evidenced by pSTAT3 levels following IL-22 treatment. Conclusion Collectively, these data suggest epithelial cells may optimize the beneficial effects of IL-22 through the induction of the IL-22 receptor during viral infection in the lung.

IL-22 Plays a Critical Role in Maintaining Epithelial Integrity During Pulmonary Infection

“…Following infection, expression of IL-22Ra1 is highly increased in injured areas of the distal lung. Tlr3 activation by viral pathogen-associated molecular pattern molecules in epithelial cells results in increased expression of IL-22Ra1 via IFNβ dependent STAT1 signaling (23). Additional pathways have been shown to regulate IL-22Ra1 protein stability.…”

Immune Modulation as a Therapeutic Option During the SARS-CoV-2 Outbreak: The Case for Antimalarial Aminoquinolines

“…Proton capture explains CQ/HCQ-induced pH increase and organelle deacidification, affecting any subcellular compartment with baseline pH lower than the surrounding cytoplasm, e.g., lysosomes, Golgi vesicles, and microsomes. CQ/HCQ thus interfere with local proteases and endosomal pattern recognition receptors (PRRs), notably toll-like receptors (TLRs), which sense viral nucleic acids ( 15 , 19 , 27 , 28 ). Impaired endosomal/lysosomal protease activity disrupts cellular and infectious processes.…”

“…CQ/HCQ modulate the monocyte-macrophage axis through multiple pathways ( Figure 2 ), including deacidification of intracellular organelles and disruption of cytokine production. Endosomal pH increase disrupts nucleic acid binding to endosomal TLRs, such as TLR-3, TLR-7, and TLR-9, thereby inhibiting endosomal TLR-mediated induction of type I IFN ( 19 , 27 , 28 ). In addition, one of the most prominent targets of CQ/HCQ during infection is the production of TNFα (Tumor Necrosis Factor α), a major proinflammatory cytokine driving a positive feedback loop of type 1 macrophage activation, oxygen and nitrogen reactive species generation, further proinflammatory mediators release, and more efficient phagocytosis ( 70 ).…”

“…CQ/HCQ act on immune cells residing in the airway and pulmonary environments, but also affect structural elements such as epithelium, endothelium, smooth muscle, and fibroblasts, potentially protecting lung tissue from overt damage. CQ inhibits TLR-3 sensing and thus abrogates IL22Ra1 (Interleukin 22 Receptor Subunit Alpha-1) induction in normal human bronchial epithelial cells ( 28 ). IL-22 supports cell proliferation and inhibits apoptosis, thus favoring lung epithelial repair under mild viral attack, but retaining a deleterious potential in cases of serious lung viral infections.…”

“…IL-22 supports cell proliferation and inhibits apoptosis, thus favoring lung epithelial repair under mild viral attack, but retaining a deleterious potential in cases of serious lung viral infections. As demonstrated in A549 cells, a cell line of adenocarcinomic human alveolar basal epithelial cells, activation of TLR-3 by the H1N1 influenza virus induces type I IFN which directly upregulates the expression of IL-22Ra1 in a STAT1-dependent manner ( 28 ).…”