Propionibacterium acnes activates caspase-1 in human neutrophils
Version of Record online: 20 DEC 2012
© 2012 APMIS. Published by John Wiley & Sons Ltd.
Volume 121, Issue 7, pages 652–663, July 2013
How to Cite
Propionibacterium acnes activates caspase-1 in human neutrophils. APMIS 2013; 121: 652–63., , , .
- Issue online: 19 JUN 2013
- Version of Record online: 20 DEC 2012
- Manuscript Accepted: 1 NOV 2012
- Manuscript Received: 11 MAY 2012
- King Gustaf V Memorial Foundation
- Swedish Research Council. Grant Number: K2010-57X-21435-01-3
- Propionibacterium acnes ;
- anaerobic bacteria;
- innate immunity;
Propionibacterium acnes is a Gram-positive, slow-growing, anaerobic bacillus, predominantly found as a commensal on the skin and mucous membranes of adults. It is, however, also considered an opportunistic pathogen; mostly associated with acne vulgaris, but rarely also with severe infections such as infective endocarditis, prosthetic joint infections, and deep sternal wound infections following cardiothoracic surgery. In addition, P. acnes has recently been found in high frequency in prostate tissue from patients with prostatitis and prostate cancer. The NOD-like receptors (NLR) act as intracellular sensors of microbial components, and a number of various bacteria have been found to induce assembling and activation of NLR-inflammasomes; leading to a pro-inflammatory response. The inflammasome-mediated formation of the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18 involves the auto-proteolytic maturation of caspase-1. This study investigated if P. acnes activates inflammasomes. Propionibacterium acnes isolates (n = 29) with diverse origin were used as stimuli for peripheral leukocytes obtained from blood donors (BDs). The activity of inflammasomes was determined by measuring caspase-1 by flow cytometry and cytokine production by ELISA. A significant amount of caspase-1 was found in neutrophils upon P. acnes stimulation, whereas only a modest activation was seen in monocytes. The activation was mainly produced by components of the bacterial cell and no exo-products, because heat-killed and live bacteria caused high activation of caspase-1 as well as cytokine production, whereas the bacterial supernatant elicited minor effect. The response among different BDs varied significantly, almost fivefold. In addition, P. acnes of various origins showed considerable variation, however, the commensal isolates showed a stronger response compared with the invasive. In conclusion, although regarded as a harmless commensal of the skin, P. acnes strongly activates the inflammasome of human peripheral neutrophils.