An animal study on the effect of topically administered ambroxol for dry eye

Objective: To evaluate the effect of 0.2% ambroxol eye drop on tear secretion and corneal healing on a rabbit dry eye model, and to delineate potential underlying mechanisms. Materials and method: A mixed mechanism dry eye model was created using 12 healthy New Zealand rabbits by excision of the main lacrimal glands, Harderian gland and nictitating membrane. Establishment of the model was confirmed by the decrease of Schirmer I and increase of corneal fluorescein staining scores. Two weeks after model creation, the rabbits were randomly and evenly divided into NaCl, 0.1% sodium hyaluronate and 0.2% ambroxol groups. Each group was administered the respective eye drops 4 times a day for four weeks. The Schirmer I test and corneal fluorescein staining were performed at two and four weeks. After four weeks of treatment, the animals were sacrificed and the conjunctiva and eyelid specimens collected. Inflammatory factors IL-8, TNF-α, and goblet cell specific mucin MUC5AC were measured by ELISA while the lid meibomian gland was evaluated by oil red O staining. Results: Compared with the baseline, 2 weeks after the surgery, Schirmer I test value decreased significantly (20.35 ± 5.18 mm/5 min vs 13.95 ± 4.64 mm/5 min, p < 0.01), and the fluorescein staining score increased significantly (0.5 ± 0.6 vs 5.5 ± 1.4, p < 0.01). After four weeks of treatment, compared with the NaCl and sodium hyaluronate groups, tear secretion in ambroxol group increased significantly (p < 0.01), while the corneal fluorescence staining score decreased significantly (p < 0.01). In the conjunctival tissue, significant decrease was seen in TNF-α (p < 0.01) and IL-8 [p (unilateral) < 0.05] concentrations in ambroxol group, and significant increase in MUC5AC concentration (p < 0.01) in ambroxol group as well. The lipid content in the lid meibomian glands appeared increased after the administration of ambroxol. Conclusion: The present rabbit dry eye model study demonstrated potentials of topically administered 0.2% ambroxol in stimulating tear and mucin secretion, inhibiting ocular surface inflammation, promoting corneal healing, and possibly augmenting meibomian gland lipid production.