Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides
Background/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureu...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Cell Physiol Biochem Press GmbH & Co KG
2017-10-01
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| Series: | Cellular Physiology and Biochemistry |
| Subjects: | |
| Online Access: | https://www.karger.com/Article/FullText/484296 |
| _version_ | 1818869964661063680 |
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| author | Jie Ma Erich Gulbins Michael J. Edwards Charles C. Caldwell Martin Fraunholz Katrin Anne Becker |
| author_facet | Jie Ma Erich Gulbins Michael J. Edwards Charles C. Caldwell Martin Fraunholz Katrin Anne Becker |
| author_sort | Jie Ma |
| collection | DOAJ |
| description | Background/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureus mediate many of these effects. Here, we aimed to identify molecular mechanisms how α-toxin, a major S. aureus toxin, induces inflammation. Methods: Macrophages were isolated from the bone marrow of wildtype and acid sphingomyelinase-deficient mice, stimulated with S. aureus α-toxin and activation of the acid sphingomyelinase was quantified. The subcellular formation of ceramides was determined by confocal microscopy. Release of cathepsins from lysosomes, activation of inflammasome proteins and formation of Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) were analyzed by western blotting, confocal microscopy and ELISA. Results: We demonstrate that S. aureus α-toxin activates the acid sphingomyelinase in ex vivo macrophages and triggers a release of ceramides. Ceramides induced by S. aureus α-toxin localize to lysosomes and mediate a release of cathepsin B and D from lysosomes into the cytoplasm. Cytosolic cathepsin B forms a complex with Nlrc4. Treatment of macrophages with α-toxin induces the formation of IL-1β and TNF-α. These events are reduced or abrogated, respectively, in cells lacking the acid sphingomyelinase and upon treatment of macrophages with amitriptyline, a functional inhibitor of acid sphingomyelinase. Pharmacological inhibition of cathepsin B prevented activation of the inflammasome measured as release of IL-1β, while the formation of TNF-α was independent of cathepsin B. Conclusion: We demonstrate a novel mechanism how bacterial toxins activate the inflammasome and mediate the formation and release of cytokines: S. aureus α-toxin triggers an activation of the acid sphingomyelinase and a release of ceramides resulting in the release of lysosomal cathepsin B and formation of pro-inflammatory cytokines. |
| first_indexed | 2024-12-19T11:59:30Z |
| format | Article |
| id | doaj.art-6ac821c4f51c4a5ea71ca906de467e95 |
| institution | Directory Open Access Journal |
| issn | 1015-8987 1421-9778 |
| language | English |
| last_indexed | 2024-12-19T11:59:30Z |
| publishDate | 2017-10-01 |
| publisher | Cell Physiol Biochem Press GmbH & Co KG |
| record_format | Article |
| series | Cellular Physiology and Biochemistry |
| spelling | doaj.art-6ac821c4f51c4a5ea71ca906de467e952022-12-21T20:22:32ZengCell Physiol Biochem Press GmbH & Co KGCellular Physiology and Biochemistry1015-89871421-97782017-10-014362170218410.1159/000484296484296Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and CeramidesJie MaErich GulbinsMichael J. EdwardsCharles C. CaldwellMartin FraunholzKatrin Anne BeckerBackground/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureus mediate many of these effects. Here, we aimed to identify molecular mechanisms how α-toxin, a major S. aureus toxin, induces inflammation. Methods: Macrophages were isolated from the bone marrow of wildtype and acid sphingomyelinase-deficient mice, stimulated with S. aureus α-toxin and activation of the acid sphingomyelinase was quantified. The subcellular formation of ceramides was determined by confocal microscopy. Release of cathepsins from lysosomes, activation of inflammasome proteins and formation of Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) were analyzed by western blotting, confocal microscopy and ELISA. Results: We demonstrate that S. aureus α-toxin activates the acid sphingomyelinase in ex vivo macrophages and triggers a release of ceramides. Ceramides induced by S. aureus α-toxin localize to lysosomes and mediate a release of cathepsin B and D from lysosomes into the cytoplasm. Cytosolic cathepsin B forms a complex with Nlrc4. Treatment of macrophages with α-toxin induces the formation of IL-1β and TNF-α. These events are reduced or abrogated, respectively, in cells lacking the acid sphingomyelinase and upon treatment of macrophages with amitriptyline, a functional inhibitor of acid sphingomyelinase. Pharmacological inhibition of cathepsin B prevented activation of the inflammasome measured as release of IL-1β, while the formation of TNF-α was independent of cathepsin B. Conclusion: We demonstrate a novel mechanism how bacterial toxins activate the inflammasome and mediate the formation and release of cytokines: S. aureus α-toxin triggers an activation of the acid sphingomyelinase and a release of ceramides resulting in the release of lysosomal cathepsin B and formation of pro-inflammatory cytokines.https://www.karger.com/Article/FullText/484296Staphylococcus aureusSphingomyelinaseCeramide, toxinsMacrophagesCytokines |
| spellingShingle | Jie Ma Erich Gulbins Michael J. Edwards Charles C. Caldwell Martin Fraunholz Katrin Anne Becker Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides Cellular Physiology and Biochemistry Staphylococcus aureus Sphingomyelinase Ceramide, toxins Macrophages Cytokines |
| title | Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides |
| title_full | Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides |
| title_fullStr | Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides |
| title_full_unstemmed | Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides |
| title_short | Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides |
| title_sort | staphylococcus aureus α toxin induces inflammatory cytokines via lysosomal acid sphingomyelinase and ceramides |
| topic | Staphylococcus aureus Sphingomyelinase Ceramide, toxins Macrophages Cytokines |
| url | https://www.karger.com/Article/FullText/484296 |
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