Abstract
PurposeTo test the effects of acidic vs. neutral pH glycyrrhizin (GLY) on the unwounded and wounded normal mouse cornea and after infection with Pseudomonas aeruginosa isolates KEI 1025 and multidrug-resistant MDR9.MethodsAcidic or neutral GLY vs. phosphate-buffered saline (PBS) was topically applied to normal or wounded corneas of C57BL/6 mice. In unwounded corneas, goblet cells and corneal nerves were stained and quantitated. After wounding, corneas were fluorescein stained and photographed using a slit lamp. Mice also were infected with KEI 1025 or MDR9 and the protective effects of GLY pH evaluated comparatively.ResultsIn the unwounded cornea, application of acidic or neutral GLY vs. PBS reduced the number of bulbar conjunctival goblet cells but did not alter corneal nerve density. Similar application of GLY to scarified corneas delayed wound closure. After KEI 1025 infection, none of the GLY vs. PBS-treated corneas perforated; GLY treatment also decreased plate count (neutral pH more effective) and reduced MPO and several cytokines. Similarly, for MDR9, GLY at either pH was protective and also enhanced the effects of moxifloxacin to which MDR9 is resistant.ConclusionAcidic or neutral pH GLY decreased goblet cell number but had no effect on nerve density. After corneal wounding, GLY at either pH (1) delayed wound closure and, (2) after infection, decreased keratitis when used alone or in combination with moxifloxacin. Neutral pH did not alter the therapeutic effect of GLY and would be preferred if used clinically.
Highlights
Glycyrrhizin (GLY), a derivative of the licorice root, is used in traditional medicine in many parts of the world due to its nutritional and therapeutic properties (Isbrucker and Burdock, 2006)
Periodic acid–Schiff (PAS) positively stained goblet cells were routinely observed after phosphate-buffered saline (PBS) (Figure 1A, arrows) application but were rarely seen after either acidic (Figure 1C) or neutral (Figure 1D) GLY application
Both acidic and neutral GLY application significantly reduced the number of PAS-positive cells vs. PBS (Figure 1B, p < 0.001 for both)
Summary
Glycyrrhizin (GLY), a derivative of the licorice root, is used in traditional medicine in many parts of the world due to its nutritional and therapeutic properties (Isbrucker and Burdock, 2006) It is a triterpenoid saponin with anti-inflammatory properties (Yang et al, 2017). In other studies, ophthalmic solutions containing GLY as nanocarriers at neutral pH were used to treat Staphylococcus aureus infection in rabbits (Song et al, 2020; Zhang et al, 2021) and corneal wounds in diabetic mice (Hou et al, 2021a). Pilot clinical studies have investigated the efficacy of GLY in ophthalmic solutions (all at neutral pH) to treat blepharitis (Mencucci et al, 2013) and dry eye disease (Burillon et al, 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
