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Potential role of macrophages in experimental keratomycosis
Jianzhang Hu1, Ye Wang, Lixin Xie
1Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Qingdao, China.
Purpose:
To investigate the potential role of macrophages in keratomycosis.
Methods:
Macrophage elimination was achieved by repeated subconjunctival injection of liposomes containing dichloromethylene diphosphonate (Cl(2)MDP-LIP) in BALB/c mice with Fusarium solani and Candida albicans keratitis, respectively. Controls received liposomes containing phosphate-buffered saline (PBS-LIP). Infected corneas were homogenized for colony counts. Immunohistochemistry was used to determine the efficiency of macrophage depletion. The cytokine production of Th1 cells, expressed by IFN-gamma and IL-12, and of Th2 cells, expressed by IL-4 and IL-10, in corneas was analyzed by enzyme-linked immunosorbent assay. Cytokine mRNA levels were detected by real-time polymerase chain reaction. Toll-like receptor 4 (TLR4) expression and mRNA levels were also examined. Immunoblotting and immunofluorescence staining were performed to evaluate the correlation between macrophages and TLR4 distribution.
Results:
Histopathologically, more severe keratomycosis developed in the mice treated with Cl(2)MDP-LIP than those treated with PBS-LIP 5 and 7 days after inoculation. In the Cl(2)MDP-LIP-treated group, little expression of macrophages could be detected in the conjunctiva and cornea. Numerous colonies were observed. There was a marked decrease of Th1 and Th2 cytokine production and mRNA expression, and TLR4 was significantly upregulated. Immunofluorescence staining demonstrated that partial F4/80(+) cells were TLR4(+). There was a positive correlation between TLR4 mRNA and IFN-gamma mRNA expression.
Conclusions:
Local depletion of macrophages may downregulate the immune response and aggravate fungal keratitis. Macrophages appear to play an important role in host defense against corneal infection of F. solani and C. albicans.
Insights
Depleting macrophages worsened fungal keratitis in mice, indicating their crucial role in fighting corneal infections from Fusarium solani and Candida albicans.
Area of Science:
- Ophthalmology
- Immunology
- Microbiology
Background:
- Keratomycosis, a fungal infection of the cornea, poses a significant threat to vision.
- The role of macrophages in the host immune response to fungal keratitis is not fully understood.
Purpose of the Study:
- To investigate the role of macrophages in the pathogenesis of fungal keratitis.
- To determine the impact of macrophage depletion on the immune response and disease severity in a murine model.
Main Methods:
- Macrophage depletion was induced using liposomes containing dichloromethylene diphosphonate (Cl(2)MDP-LIP) in mice with Fusarium solani or Candida albicans keratitis.
- Corneal fungal burden was quantified, and immune responses were assessed by measuring Th1/Th2 cytokine levels (IFN-gamma, IL-12, IL-4, IL-10) and Toll-like receptor 4 (TLR4) expression.
- Immunohistochemistry, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, immunoblotting, and immunofluorescence staining were employed.
Main Results:
- Macrophage depletion led to more severe keratomycosis and increased fungal burden.
- A significant decrease in Th1 and Th2 cytokine production and mRNA expression was observed in depleted corneas.
- Toll-like receptor 4 (TLR4) expression was upregulated, with partial colocalization with macrophages (F4/80+ cells).
Conclusions:
- Local depletion of macrophages exacerbates fungal keratitis, suggesting a critical role in host defense.
- Macrophages are essential for controlling Fusarium solani and Candida albicans corneal infections.
