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Updated: May 24, 2026
Induction of Ocular Surface Inflammation and Collection of Involved Tissues
Published on: August 4, 2022
The effect of Demodex-associated Bacillus oleronius proteins and hyperosmolarity on a human conjunctival epithelial
Nikhil Sharma1, Eilidh Martin1, Edward Ian Pearce1
1Department of Vision Sciences, Glasgow Caledonian University, Glasgow, Scotland, United Kingdom.
Purpose:
Demodex mites act as a carrier vector for the bacterium Bacillus oleronius. Antigenic proteins from this bacterium are capable of producing an inflammatory response. This study investigated the potential effects of Demodex spp.-associated Bacillus oleronius proteins and dry eye-induced hyperosmolarity on an immortalised human conjunctival epithelial (Chang) cell line.
Methods:
The Wong Kilbourne derivative of the Chang (WKD) HeLa-modified conjunctiva-derived epithelial cell line was cultured in a series of NaCl-hyperosmolar conditions with various concentrations ranging from 350mOsm/L to 550mOsm/L. Chang cells were then exposed to semi-purified B.oleronius proteins at 2 µg and 6 µg either alone or in conjunction with dry eye-induced hyperosmolar (HO) stress at 2 µg + HO500 mOsm/L and 6 µg + HO500 mOsm/L. The cell viability was assessed with the RealTime-Glo MT cell viability assay.
Results:
Compared to controls, the cell viability appeared to decrease in a dose-dependent manner. B. oleronius concentration at 6 µg showed significantly lower cell viability than both controls (p < 0.001) and 2 µg (p < 0.001). When 500mOsm/L was added to the 2 µg and 6 µg concentrations, the lowest cell viability was observed (p < 0.001). At 24 hours, the B.oleronius 2 μg combined with HO500 resulted in 38% viable cells, compared to 81% viability in B.oleronius 2 μg alone (p < 0.001). Similarly, the B.oleronius 6 μg combined with HO500 showed only 23% metabolising cells compared to 60% viability cells in B.oleronius 6 μg alone (p < 0.001).
Conclusion:
The results suggest that the presence of bacterial proteins and hyperosmolarity have a dose and time-dependent effect on cellular viability. These experiments suggest that patients affected with the comorbidity of dry eye disease and Demodex blepharitis could experience more severe signs than those with Demodex-associated blepharitis alone.
Insights
Demodex mites carry Bacillus oleronius bacteria, whose proteins can cause inflammation. This study found that bacterial proteins and dry eye-induced hyperosmolarity significantly decrease conjunctival cell viability, suggesting more severe symptoms in patients with both conditions.
Area of Science:
- Ophthalmology
- Microbiology
- Cell Biology
Background:
- Demodex mites harbor Bacillus oleronius, a bacterium whose proteins can trigger inflammatory responses.
- Dry eye disease is often associated with ocular surface inflammation and hyperosmolarity.
Purpose of the Study:
- To investigate the combined effects of Bacillus oleronius proteins and hyperosmolarity on human conjunctival epithelial cells.
- To assess the impact of these factors on cell viability.
Main Methods:
- Cultured a human conjunctival epithelial cell line (Chang cells) under varying hyperosmolar conditions (350-550 mOsm/L).
- Exposed cells to semi-purified Bacillus oleronius proteins (2 µg and 6 µg) alone and combined with hyperosmolar stress (500 mOsm/L).
- Assessed cell viability using the RealTime-Glo MT assay.
Main Results:
- Bacillus oleronius proteins reduced cell viability in a dose-dependent manner.
- Hyperosmolarity significantly exacerbated the reduction in cell viability caused by bacterial proteins.
- Combined exposure to 6 µg B. oleronius proteins and 500 mOsm/L hyperosmolarity resulted in the lowest cell viability (23%).
Conclusions:
- Bacterial proteins and hyperosmolarity exert a dose- and time-dependent negative effect on conjunctival cell viability.
- Patients with both dry eye disease and Demodex blepharitis may experience more severe ocular symptoms.
- This highlights the complex interplay between microbial factors and ocular surface environment in disease pathogenesis.
