Intracellular Staphylococcus aureus triggers pyroptosis and contributes to inhibition of healing due to perforin-2 suppression
Irena Pastar, … , Hadar Lev-Tov, Marjana Tomic-Canic
Irena Pastar, … , Hadar Lev-Tov, Marjana Tomic-Canic
Published November 2, 2021
Citation Information: J Clin Invest. 2021;131(24):e133727. https://doi.org/10.1172/JCI133727.
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Intracellular Staphylococcus aureus triggers pyroptosis and contributes to inhibition of healing due to perforin-2 suppression

Abstract

Impaired wound healing associated with recurrent Staphylococcus aureus infection and unresolved inflammation are hallmarks of nonhealing diabetic foot ulcers (DFUs). Perforin-2, an innate immunity molecule against intracellular bacteria, limits cutaneous infection and dissemination of S. aureus in mice. Here, we report the intracellular accumulation of S. aureus in the epidermis of DFUs with no clinical signs of infection due to marked suppression of perforin-2. S. aureus residing within the epidermis of DFUs triggers AIM2 inflammasome activation and pyroptosis. These findings were corroborated in mice lacking perforin-2. The effects of pyroptosis on DFU clinical outcomes were further elucidated in a 4-week longitudinal clinical study in patients with DFUs receiving standard care. Increased AIM2 inflammasome and ASC-pyroptosome coupled with induction of IL-1β were found in nonhealing DFUs compared with healing DFUs. Our findings revealed that perforin-2 suppression, intracellular S. aureus accumulation, and associated induction of pyroptosis contribute to healing inhibition and prolonged inflammation in patients with DFUs.

Authors

Irena Pastar, Andrew P. Sawaya, Jelena Marjanovic, Jamie L. Burgess, Natasa Strbo, Katelyn E. Rivas, Tongyu C. Wikramanayake, Cheyanne R. Head, Rivka C. Stone, Ivan Jozic, Olivera Stojadinovic, Eran Y. Kornfeld, Robert S. Kirsner, Hadar Lev-Tov, Marjana Tomic-Canic

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Figure 3

AIM2 inflammasome activation induces pyroptosis and increases IL-1β activation in DFUs.

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AIM2 inflammasome activation induces pyroptosis and increases IL-1β acti...
(A) Immunoperoxidase staining of AIM2 in FS and DFUs. AIM2 was induced in DFUs compared with FS. Epi, epidermis; Der, dermis; dashed line demarcates epidermal/dermal boundary; scale bar: 50 μm. (B) Western blot of AIM2 in FS and DFUs (n = 3 per group). (C) Representative Western blot and quantification (D) of AIM2 levels in WT (n = 4) and P-2–KO (n = 5) from murine skin in response to infection with MRSA USA3000 AH1726, validating that MRSA infection induced AIM2 with amplified induction in the skin from P-2–KO mice; *P < 0.05. (E) Confocal imaging confirming intracellular MRSA in the epidermis of P-2–KO mice but not in the WT; Epi, epidermis; Der, dermis; dashed line demarcates epidermal/dermal boundary; arrows indicate intracellular MRSA; scale bar: 10 μm; inset scale bar: 2 μm. (F) Western blot caspase-1 in FS and DFUs (n = 3 per group). Caspase-1 is uniquely activated in DFUs compared with FS. (G) Western blot of gasdermin D (GsdmD; n = 3 per group). Activation of GsdmD was found to be present in prospectively collected DFUs. (H) Gene signature of DFUs compared with control FS of a subset of genes involved in pyroptosis indicated strong induction of IL-1β. (I) ELISA of IL-1β in FS and DFUs confirmed increased levels of IL-1β in DFUs (n = 6 biological replicates for FS, n = 3 biological replicates for DFUs). Data are represented as mean ± SEM and analyzed by unpaired 2-tailed t test, **P < 0.01. (J) ELISA of IL-1β confirmed increased levels of IL-1β in the murine skin lacking P-2 after infection (n = 4 biological, 8 technical replicates for WT, n = 4 biological, 7 technical replicates for P-2–KO). Data are represented as mean ± SEM and analyzed by unpaired 2-tailed t test, **P < 0.01.