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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Research Article Dermatology Inflammation

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 1

Suppression of P-2 in the epidermis of DFUs allows intracellular accumulation of S. aureus.

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Suppression of P-2 in the epidermis of DFUs allows intracellular accumul...
(A) Relative expression of P-2 was assessed by qPCR normalized to Arpc2 in control foot skin (FS; n = 5 biological replicates, 15 technical replicates) and diabetic foot ulcers (DFUs; n = 6 biological replicates, 18 technical replicates). (B) P-2 mRNA levels in control and DFU keratinocytes quantified using FISH-Flow. Live CD45–, CD31–, and CD104+ cells were analyzed for P-2 RNA expression within epidermal keratinocytes (n = 5 biological replicates). (C) Quantification of intracellular bacterial load in the epidermis and dermis per milligram of tissue (n = 5 biological replicates, 15 technical replicates). (D) Immunofluorescence staining of FS and DFU with S. aureus–specific antibody (green). Arrows indicate presence of intracellular S. aureus. DAPI = nuclei; dashed line demarcates epidermal-dermal boundary; Epi, epidermis; Der, dermis; scale bar: 50 μm. (E) Confocal imaging of DFU tissue stained with keratin 17 (K17; red) and S. aureus–specific antibody (green). DAPI (blue) = nuclei; images taken at 63× magnification, scale bar: 10 μm. **P < 0.05 (A and B); **P < 0.01 (C).