Achyranthis radix Extract Improves Urban Particulate Matter-Induced Dry Eye Disease

Abstract

Dry eye disease (DED) is a multifactorial inflammatory disease that severely impairs patients' quality of life. Particulate matter comprises a harmful mixture of particles less than 10 μm in size, which on contact with the eye, causes inflammation in the cornea/conjunctival epithelium, threatening eye health and triggering the onset of DED. Achyranthis radix is an ingredient of traditional medicine generally used for treating osteoporosis, trauma, and thrombosis in Asian countries. However, the effect of Achyranthis radix on eye health has not been elucidated. In this study, we evaluate the protective effect of Achyranthis radix hot water extract (ARE) in a rat model of urban particulate matter (UPM)-induced DED. UPM with or without ARE were topically administered on both eyes thrice daily for 10 days. ARE induced tear secretion and improved corneal irregularity. Additionally, ARE treatment protected the corneal epithelial cells from UPM-induced apoptosis. It also restored rMuc4 expression in the cornea and increased goblet cell density in the conjunctiva. These results are suggestive of the potential of ARE as a topical therapeutic agent for treating DED.

Keywords: Achyranthis radix extract; dry eye disease; urban particulate matter.

Figure 1

HPLC chromatogram of Achyranthis radix extract (ARE). Peak identification: 1, ecdysterone; 2, 25R-inokosterone; 3, 25S-inokosterone. Chromatographic conditions are described in the text. Detection was at 250 nm.

Figure 2

Achyranthis radix extract restored tear secretion in rat model of urban particulate matter-induced dry eye disease. The volume of tears secreted was measured using the phenol red thread test. The length of the thread that changed color to red is shown for each group. Each bar represents the mean tear volume ± SEM, n = 6. ### p < 0.001 vs. control group, ** p < 0.01 vs. UPM group. CTL, control; ARE, Achyranthis radix extract; UPM, urban particulate matter.

Figure 3

Achyranthis radix extract improved corneal smoothness. (A) Corneal smoothness was evaluated by the reflection images of the white ring from the light source on the surface of the eye. (B) Each bar represents mean corneal irregularity score ± SEM, n = 6. ### p < 0.001 vs. control group, ** p <0. 01, *** p < 0.001 vs. urban particulate matter group. ARE, Achyranthis radix extract; UPM, urban particulate matter; CTL, control; AU, arbitrary unit.

Figure 4

Topical administration of Achyranthis radix extract reduced apoptosis of the corneal epithelium. (A) Apoptosis of corneal epithelial cell was evaluated using TUNEL assay. (B) Each bar represents the mean number of TUNEL-positive cells ± SEM, n ≥ 5. ### p < 0.001 vs. control group, ** p < 0.01 vs. UPM group. ARE, Achyranthis radix extract; UPM, urban particulate matter; CTL, control; TUNEL, terminal deoxynucleotidyl transferase deoxy uridine triphosphate nick end labeling; SEM, standard error of mean.

Figure 5

Achyranthis radix extract restored rMuc4 expression in the corneal epithelium. (A) Immunohistochemical staining of the corneal epithelium was performed by immunostaining the paraffin-embedded corneal sections for rMuc4. The immunostained sections were counterstained with hematoxylin. (B) Each bar represents mean rMuc4 fluorescence signal intensity ± SEM, n ≥ 5. ### p < 0.001 vs. control group, * p < 0.05 vs. UPM group. ARE, Achyranthis radix extract; UPM, urban particulate matter; CTL, control; AU, arbitrary units; SEM, standard error of mean.

Figure 6

Achyranthis radix extract restored goblet cell population in the conjunctival epithelium. (A) Representative PAS-stained images of conjunctival sections. The violet colored cells are goblet cells. (B) Each bar represents the mean number of goblet cells ± SEM, n ≥ 3. ### p < 0.001 vs. control group, * p < 0.05, *** p < 0.001 vs. UPM group. ARE, Achyranthis radix extract; UPM, urban particulate matter; PAS, periodic acid-Schiff; CTL, control; SEM, standard error of mean.