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Updated: May 27, 2026
Morphological and Compositional Analysis of Neutrophil Extracellular Traps Induced by Microbial and Chemical Stimuli
Published on: November 4, 2022
Demodex-associated bacterial proteins induce neutrophil activation
N O'Reilly1, D Bergin, E P Reeves
1Department of Biology, National University of Ireland Maynooth, Co. Kildare, Ireland.
Background:
Patients with rosacea demonstrate a higher density of Demodex mites in their skin than do controls. A bacterium isolated from a Demodex mite from a patient with papulopustular rosacea (PPR) was previously shown to provoke an immune response in patients with PPR or ocular rosacea, thus suggesting a possible role for bacterial proteins in the aetiology of this condition.
Objectives:
To examine the response of neutrophils to proteins derived from a bacterium isolated from a Demodex mite.
Methods:
Bacterial cells were lysed and proteins were partially purified by ÄKTA fast protein liquid chromatography. Isolated neutrophils were exposed to bacterial proteins and monitored for alterations in migration, degranulation and cytokine production.
Results:
Neutrophils exposed to proteins from Bacillus cells demonstrated increased levels of migration and elevated release of matrix metalloprotease 9, an enzyme known to degrade collagen, and cathelicidin, an antimicrobial peptide. In addition, neutrophils exposed to the bacterial proteins demonstrated elevated rates of interleukin 8 and tumour necrosis factor-α production.
Conclusions:
Proteins produced by a bacterium isolated from a Demodex mite have the ability to increase the migration, degranulation and cytokine production abilities of neutrophils. These results suggest that bacteria may play a role in the inflammatory erythema associated with rosacea.
Insights
Proteins from Demodex-associated bacteria trigger neutrophil responses, including increased migration and release of inflammatory molecules. This suggests a potential role for these bacteria in rosacea inflammation.
Area of Science:
- Microbiology and Immunology
- Dermatology
- Host-Microbe Interactions
Background:
- Increased Demodex mite density is observed in rosacea patients.
- Bacteria isolated from Demodex mites can elicit immune responses in rosacea.
- Bacterial proteins are implicated in the etiology of papulopustular rosacea (PPR) and ocular rosacea.
Purpose of the Study:
- To investigate neutrophil responses to proteins from a Demodex-associated bacterium.
- To understand the role of bacterial proteins in rosacea pathogenesis.
Main Methods:
- Bacterial cells were lysed and proteins were purified using ÄKTA fast protein liquid chromatography.
- Isolated human neutrophils were exposed to purified bacterial proteins.
- Neutrophil migration, degranulation, and cytokine production were measured.
Main Results:
- Neutrophils exposed to bacterial proteins showed increased migration.
- Elevated release of matrix metalloprotease 9 (collagen-degrading enzyme) and cathelicidin (antimicrobial peptide) was observed.
- Increased production of interleukin 8 and tumor necrosis factor-α by neutrophils was detected.
Conclusions:
- Proteins from Demodex-associated bacteria enhance neutrophil migration, degranulation, and cytokine production.
- These findings suggest that bacteria may contribute to the inflammatory erythema characteristic of rosacea.
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