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Published on: August 31, 2015
Therapeutic effect of oxidized bletilla striata polysaccharide-natamycin eye drops on fungal keratitis
Xue Tian1, Xiaoyue Ji1, Ranran Zhang2
1Department of Ophthalmology, The Affiliated Hospital of Qingdao University, Qingdao, China.
Objective:
Fungal keratitis (FK) usually develops to a poor clinical prognosis due to the fungal invasion and excessive inflammatory reaction. In order to enhance the therapeutic effect of natamycin (NAT), we used the anti-inflammatory biological polysaccharide bletilla striata polysaccharide (BSP) combined with NAT to prepare a new eye drop -- oxidized bletilla striata polysaccharide-natamycin (OBN).
Methods:
UV-vis, FT-IR, and fluorescence spectroscopy were used to identify the synthesis of OBN. Biocompatibility of OBN was determined by CCK-8, scratch assay, and corneal toxicity test. RAW264.7 cells and C57BL/6 mice were stimulated with A. fumigatus and treated with PBS, OBN, or NAT. The anti-inflammatory activity of OBN was detected by RT-PCR and ELISA. In mice with FK, the clinical scores were used to evaluate the effect of OBN; HE staining was performed to assess the corneal pathological changes; MPO assay and immunofluorescence staining were used to investigate neutrophil infiltration.
Results:
OBN was synthesized by combining oxidized bletilla striata polysaccharide (OBSP) with NAT through Schiff base reaction. OBN did not affect cell viability at a concentration of 160 μg/mL in HCECs, RAW264.7 cells, and mouse corneas. OBN versus NAT significantly improved the prognosis of A. fumigatus keratitis by reducing disease severity, neutrophil infiltration, and expression of inflammatory factors in vivo. Additionally, OBN treatment down-regulated the mRNA and protein expression levels of inflammatory factors IL-1β, TNF-α, and IL-6 in RAW264.7 and mouse models.
Conclusion:
OBN is a compound prepared by covalently linking OBSP to the imino group of NAT through Schiff base reaction. OBN treatment down-regulated inflammation and improved the prognosis of mice with A. fumigatus keratitis.
Insights
A novel eye drop, oxidized bletilla striata polysaccharide-natamycin (OBN), was developed to treat fungal keratitis. OBN demonstrated reduced inflammation and improved outcomes in a mouse model, offering a promising therapeutic strategy.
Area of Science:
- Ophthalmology
- Mycology
- Pharmacology
- Biomaterials Science
Background:
- Fungal keratitis (FK) presents a significant clinical challenge due to invasive fungal infections and severe inflammatory responses, often leading to poor prognoses.
- Current treatments, such as natamycin (NAT), may require enhancement to improve therapeutic efficacy and patient outcomes in managing FK.
Purpose of the Study:
- To develop and evaluate a novel ophthalmic formulation, oxidized bletilla striata polysaccharide-natamycin (OBN), for enhanced treatment of fungal keratitis.
- To investigate the anti-inflammatory properties and therapeutic potential of OBN in preclinical models of fungal keratitis.
Main Methods:
- Oxidized bletilla striata polysaccharide (OBSP) was conjugated with natamycin (NAT) via Schiff base reaction to synthesize OBN.
- OBN's synthesis was confirmed using spectroscopic techniques (UV-vis, FT-IR, fluorescence). Biocompatibility was assessed via CCK-8, scratch assays, and corneal toxicity tests.
- Anti-inflammatory effects were evaluated in RAW264.7 cells and C57BL/6 mice infected with *A. fumigatus*, measuring inflammatory markers (RT-PCR, ELISA) and neutrophil infiltration (MPO assay, immunofluorescence).
Main Results:
- OBN was successfully synthesized and exhibited good biocompatibility, with no observed cytotoxicity in corneal and immune cells at tested concentrations.
- In a mouse model of *A. fumigatus* keratitis, OBN treatment significantly reduced disease severity, corneal pathology, and neutrophil infiltration compared to NAT alone.
- OBN effectively downregulated key pro-inflammatory cytokines, including IL-1β, TNF-α, and IL-6, at both mRNA and protein levels in cellular and animal models.
Conclusions:
- The novel OBN eye drop, formed by covalently linking OBSP and NAT, demonstrates significant anti-inflammatory activity and therapeutic benefits.
- OBN represents a promising new therapeutic agent for fungal keratitis, offering improved clinical outcomes by mitigating inflammation and infection progression.
