Tollip Inhibits IL-33 Release and Inflammation in Influenza A Virus-Infected Mouse Airways

Abstract

Respiratory influenza A virus (IAV) infection continues to pose significant challenges in healthcare of human diseases including asthma. IAV infection in mice was shown to increase IL-33, a key cytokine in driving airway inflammation in asthma, but how IL-33 is regulated during viral infection remains unclear. We previously found that a genetic mutation in Toll-interacting protein (Tollip) was linked to less airway epithelial Tollip expression, increased neutrophil chemokines, and lower lung function in asthma patients. As Tollip is involved in maintaining mitochondrial function, and mitochondrial stress may contribute to extracellular ATP release and IL-33 secretion, we hypothesized that Tollip downregulates IL-33 secretion via inhibiting ATP release during IAV infection. Wild-type and Tollip knockout (KO) mice were infected with IAV and treated with either an ATP converter apyrase or an IL-33 decoy receptor soluble ST2 (sST2). KO mice significantly lost more body weight and had increased extracellular ATP, IL-33 release, and neutrophilic inflammation. Apyrase treatment reduced extracellular ATP levels, IL-33 release, and neutrophilic inflammation in Tollip KO mice. Excessive lung neutrophilic inflammation in IAV-infected Tollip KO mice was reduced by sST2, which was coupled with less IL-33 release. Our data suggest that Tollip inhibits IAV infection, potentially by inhibiting extracellular ATP release and reducing IL-33 activation and lung inflammation. In addition, sST2 may serve as a potential therapeutic approach to mitigate respiratory viral infection in human subjects with Tollip deficiency.

High-fat diet and palmitic acid amplify airway type 2 inflammation

“…Cell supernatants (equal volume for all the samples) were prepared and analyzed as previously described ( 26 , 27 ). Blots were probed with an antibody against DPP4 (1:1,000, Proteintech) followed by horseradish peroxidase-conjugated secondary IgG (1:3,000; EMD Millipore, Burlington, Massachusetts, USA).…”

Tollip deficiency exaggerates airway type 2 inflammation in mice exposed to allergen and influenza A virus: role of the ATP/IL-33 signaling axis

“…Mice were lightly anesthetized with isoflurane, then intranasally exposed to 10 μg of HDM ( 30 ) or PBS on days 0 and 7, and then challenged daily with HDM at days 14–16. Two days after the last HDM challenge, mice were inoculated intranasally with 1x10 2 pfu/mouse of IAV in 50 µL of PBS or 50 µL of PBS ( 17 ). Mice were sacrificed at day 7 and day 10 post IAV infection ( Supplementary Figure 1 ).…”

“…Using the HDM and IAV infection model as described above, Tollip KO and WT mice were intranasally inoculated with 10 µg of recombinant mouse ST2 (R&D Systems, Minneapolis, MN, USA), or IgG control ( 17 ), in 50 µL of PBS on day 8 and day 9 post IAV infection. Mice were sacrificed on day 10 post infection.…”

“…IL-33 released into mouse BALF was measured via western blot as previously described ( 17 ). An equal volume of BALF (25 µl) was run on 15% polyacrylamide gels, and proteins were separated via denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).…”

“…The role of Tollip in viral exacerbations of asthma remains unclear. Our previous study suggests that Tollip deficiency enhanced lung non-type 2 (e.g., neutrophilic) inflammation, which was coupled with increased extracellular ATP and IL-33 release ( 17 ). However, whether Tollip regulates type 2 inflammation during IAV infection via extracellular ATP and IL-33 has not been investigated.…”